Merge branch 'bmk/snmp/20210830/use_inet_backend/OTP-17526' into maint

OTP-17526

13 files changed, 969 insertions, 583 deletions

diff --git a/lib/kernel/src/gen_udp_socket.erl b/lib/kernel/src/gen_udp_socket.erl
index 43b11b456b..998ec8e194 100644
--- a/lib/kernel/src/gen_udp_socket.erl
+++ b/lib/kernel/src/gen_udp_socket.erl
@@ -1142,7 +1142,7 @@ init(Arg) ->
     error_logger:error_report([{badarg, {?MODULE, init, [Arg]}}]),
     error(badarg, [Arg]).
 
-
+                        
 socket_open(Domain, Proto, #{fd := FD} = ExtraOpts, Extra) ->
     Opts =
         (maps:merge(Extra, maps:remove(fd, ExtraOpts)))
@@ -1170,6 +1170,8 @@ socket_open(Domain, Proto, #{fd := FD} = ExtraOpts, Extra) ->
             ERROR
     end;
 socket_open(Domain, Proto, ExtraOpts, Extra) ->
+    %% ?DBG([{domain, Domain}, {proto, Proto},
+    %%       {extra_opts, ExtraOpts}, {extra, Extra}]),
     Opts = maps:merge(Extra, ExtraOpts),
     socket:open(Domain, dgram, Proto, Opts).
 
@@ -1444,7 +1446,18 @@ handle_event({call, From}, {bind, BindAddr} = _BIND, _State, {P, _D}) ->
     %% ?DBG(['try bind',
     %%       {handle_event, call}, {bind_addr, BindAddr}, {state, _State}]),
     Result = socket:bind(P#params.socket, BindAddr),
-    %% ?DBG([{bind_result, Result}]),
+    %% ?DBG([{bind_result, Result}] ++ 
+    %%     case Result of
+    %%         ok ->
+    %%             case socket:sockname(P#params.socket) of
+    %%                 {ok, SockAddr} ->
+    %%                     [{sockaddr, SockAddr}];
+    %%                 {error, SAReason} ->
+    %%                     [{sockaddr_reason, SAReason}]
+    %%             end;
+    %%         {error, BReason} ->
+    %%             [{bind_reason, BReason}]
+    %%     end),
     {keep_state_and_data, [{reply, From, Result}]};
 
 
@@ -1478,7 +1491,7 @@ handle_event(
   info, ?socket_select(Socket, SelectRef),
   #recv{info = ?select_info(SelectRef)},
   {#params{socket = Socket} = P, D}) ->
-    %% ?DBG([info, {socket, Socket}, {ref, SelectRef}]),
+    %% ?DBG(['info socket select', {socket, Socket}, {ref, SelectRef}, {p, P}, {d, D}]),
     handle_recv(P, D, []);
 
 %%
@@ -1486,7 +1499,7 @@ handle_event(
   info, ?socket_abort(Socket, SelectRef, Reason),
   #recv{info = ?select_info(SelectRef)},
   {#params{socket = Socket} = P, D}) ->
-    %% ?DBG({abort, Reason}),
+    %% ?DBG(['socket abort', {reason, Reason}, {p, P}, {d, D}]),
     handle_reading(P, cleanup_recv_reply(P, D, [], Reason));
 
 %%
@@ -1622,6 +1635,8 @@ handle_recv(#params{socket = Socket, recv_method = []} = P,
     %% ?DBG(['try recvfrom', {socket, Socket}, {length, Length}]),
     case socket_recvfrom(Socket, Length) of
         {ok, {Source, <<Data/binary>>}} ->
+            %% ?DBG(['recvfrom ok', {source, Source},
+            %%       {'data sz', byte_size(Data)}]),
             handle_recv_deliver(P, D, ActionsR, {Source, Data});
         {select, ?select_info(_) = SelectInfo} ->
             %% ?DBG(['recvfrom select', {socket_info, SelectInfo}]),
@@ -1635,16 +1650,18 @@ handle_recv(#params{socket = Socket, recv_method = []} = P,
     end;
 handle_recv(#params{socket = Socket} = P,
             #{recv_length := Length} = D, ActionsR) ->
+    %% ?DBG(['try recvmsg', {socket, Socket}, {length, Length}]),
     case socket_recvmsg(Socket, Length) of
         {ok, MsgHdr} ->
             handle_recv_deliver(P, D, ActionsR, MsgHdr);
         {select, ?select_info(_) = SelectInfo} ->
+            %% ?DBG(['recvmsg select', {socket_info, SelectInfo}]),
             {next_state,
              #recv{info = SelectInfo},
              {P, D},
              reverse(ActionsR)};
         {error, Reason} ->
-            %% ?DBG({'recv error wo rest-data', Reason}),
+            %% ?DBG(['recvmsg error', {reason, Reason}]),
             handle_recv_error(P, D, ActionsR, Reason)
     end.
 
@@ -1731,10 +1748,9 @@ recv_data_deliver(
   #params{owner = Owner} = P,
   #{mode := Mode, deliver := Deliver} = D,
   ActionsR, Data) ->
-    %%
-    %% ?DBG([{owner, Owner},
-    %% 	  {mode, Mode},
-    %% 	  {header, Header}, {deliver, Deliver}, {packet, Packet}]), 
+
+    %% ?DBG([{owner, Owner}, {mode, Mode}, {deliver, Deliver}]), 
+
     {IP, Port, AncData, DeliverData} = deliver_data(Data, Mode),
     case D of
         #{recv_from := From} ->
@@ -1769,6 +1785,7 @@ mk_recv_reply(IP, Port, AncData, Data) ->
     {IP, Port, AncData, Data}.
 
 deliver_recv_msg(Pid, Active, Deliver, Socket, IP, Port, AncData, Data) ->
+    %% ?DBG(['deliver packet', {pid, Pid}]),
     Pid ! mk_recv_msg(Active, Deliver, Socket, IP, Port, AncData, Data).
 
 mk_recv_msg(true = _Active, port = _Deliver,
diff --git a/lib/snmp/doc/src/snmp_app.xml b/lib/snmp/doc/src/snmp_app.xml
index 361781cb61..9f346f0fe2 100644
--- a/lib/snmp/doc/src/snmp_app.xml
+++ b/lib/snmp/doc/src/snmp_app.xml
@@ -294,13 +294,15 @@ in the snmp_config file!
       <tag><marker id="agent_ni_opts"></marker>
         <c><![CDATA[agent_net_if_options() = [agent_net_if_option()] <optional>]]></c></tag>
       <item>
-        <p><c>agent_net_if_option() = {bind_to, bind_to()} |  
+	<p><c>agent_net_if_option() =
+	{bind_to,         bind_to()} |  
 	{sndbuf,          sndbuf()} |  
 	{recbuf,          recbuf()} |  
 	{no_reuse,        no_reuse()} |  
 	{req_limit,       req_limit()} |
 	{filter,          agent_net_if_filter_options()} |
-	{extra_sock_opts, extra_socket_options()}</c></p>
+	{extra_sock_opts, extra_socket_options()} |
+	{inet_backend,    inet | socket}</c></p>
 	<p>These options are actually specific to the used module.
 	The ones shown here are applicable to the default 
 	<c>agent_net_if_module()</c>.</p>
@@ -796,12 +798,14 @@ in the snmp_config file!
       <tag><marker id="manager_ni_opts"></marker>
         <c><![CDATA[manager_net_if_options() = [manager_net_if_option()] <optional>]]></c></tag>
       <item>
-        <p><c>manager_net_if_option() = {bind_to, bind_to()} | 
-	{sndbuf,          sndbuf()} |  
-	{recbuf,          recbuf()} | 
-	{no_reuse,        no_reuse()} |
+	<p><c>manager_net_if_option() =
+	{bind_to,         bind_to()}    | 
+	{sndbuf,          sndbuf()}     |  
+	{recbuf,          recbuf()}     | 
+	{no_reuse,        no_reuse()}   |
 	{filter,          manager_net_if_filter_options()} |
-	{extra_sock_opts, extra_socket_options()}</c></p>
+	{extra_sock_opts, extra_socket_options()} |
+	{inet_backend,    inet | socket}</c></p>
         <p>These options are actually specific to the used module.
 	The ones shown here are applicable to the default 
 	<c>manager_net_if_module()</c>.</p>
diff --git a/lib/snmp/doc/src/snmp_config.xml b/lib/snmp/doc/src/snmp_config.xml
index 41646d86c3..7dc8e2f66e 100644
--- a/lib/snmp/doc/src/snmp_config.xml
+++ b/lib/snmp/doc/src/snmp_config.xml
@@ -280,13 +280,15 @@
       <tag><marker id="agent_ni_opts"></marker>
         <c><![CDATA[agent_net_if_options() = [agent_net_if_option()] <optional>]]></c></tag>
       <item>
-	<p><c>agent_net_if_option() = {bind_to, bind_to()} |  
+	<p><c>agent_net_if_option() =
+	{bind_to,         bind_to()} |  
 	{sndbuf,          sndbuf()} |  
 	{recbuf,          recbuf()} |  
 	{no_reuse,        no_reuse()} | 
 	{req_limit,       req_limit()} |
 	{filter,          agent_net_if_filter_options()} |
-	{extra_sock_opts, extra_socket_options()}</c></p>
+	{extra_sock_opts, extra_socket_options()} |
+	{inet_backend,    inet | socket}</c></p>
         <p>These options are actually specific to the used module.
 	The ones shown here are applicable to the default 
 	<c>agent_net_if_module()</c>.</p>
@@ -818,12 +820,14 @@ in so far as it will be converted to the new format if found.
       <tag><marker id="manager_ni_opts"></marker>
         <c><![CDATA[manager_net_if_options() = [manager_net_if_option()] <optional>]]></c></tag>
       <item>
-        <p><c>manager_net_if_option() = {bind_to, bind_to()} | 
-            {sndbuf,          sndbuf()} | 
-            {recbuf,          recbuf()} | 
+	<p><c>manager_net_if_option() =
+	    {bind_to,         bind_to()}  |
+            {sndbuf,          sndbuf()}   |
+            {recbuf,          recbuf()}   |
             {no_reuse,        no_reuse()} |
             {filter,          manager_net_if_filter_options()} |
-	    {extra_sock_opts, extra_socket_options()}</c></p>
+	    {extra_sock_opts, extra_socket_options()} |
+	    {inet_backend,    inet | socket}</c></p>
         <p>These options are actually specific to the used module.
 	The ones shown here are applicable to the default 
 	<c>manager_net_if_module()</c>. </p>
diff --git a/lib/snmp/src/agent/snmpa_net_if.erl b/lib/snmp/src/agent/snmpa_net_if.erl
index b6b115bd75..cdb68afef4 100644
--- a/lib/snmp/src/agent/snmpa_net_if.erl
+++ b/lib/snmp/src/agent/snmpa_net_if.erl
@@ -128,17 +128,19 @@
 
 -record(transport,
 	{socket,
-         kind      = all :: all | transport_kind(),
-	 domain    = snmpUDPDomain,
+         mref,
+         kind         = all :: all | transport_kind(),
+	 domain       = snmpUDPDomain,
          address   :: inet:ip_address(),
          port_no   :: pos_integer(),
          port_info :: port_info(),
          %% <EPHEMERAL-FOR-FUTUR-USE>
-         ephm      = none, %%  :: ephemeral(),
-         ephm_info = undefined, % Only used if ephm =/= none and once
+         ephm         = none, %%  :: ephemeral(),
+         ephm_info    = undefined, % Only used if ephm =/= none and once
          %% </EPHEMERAL-FOR-FUTUR-USE>
-	 opts      = [],
-	 req_refs  = [] % Not used for trap/notification transports
+         inet_backend = [],
+	 opts         = [],
+	 req_refs     = [] % Not used for trap/notification transports
         }).
 
 -ifndef(default_verbosity).
@@ -274,34 +276,45 @@ do_init(Prio, NoteStore, MasterAgent, Parent, Opts) ->
              %% will be taken from the "global" socket options (which serve as
              %% default values).
              %% Also, note that Ephm are not actually used at this time.
-	     {Ephm, IpAddr, PortInfo, SocketOpts} = socket_opts(Domain, Address,
-                                                                RawSocketOpts, Opts),
+	     {Ephm, IpAddr, PortInfo, InetBackend, SocketOpts} =
+                 socket_opts(Domain, Address, RawSocketOpts, Opts),
              ?vtrace("socket opts processed:"
-                     "~n      Ephm:        ~p"
-                     "~n      Port Info:   ~p"
-                     "~n      Socket Opts: ~p", [Ephm, PortInfo, SocketOpts]),
+                     "~n      Ephm:         ~p"
+                     "~n      Port Info:    ~p"
+                     "~n      Inet Backend: ~p"
+                     "~n      Socket Opts:  ~p",
+                     [Ephm, PortInfo, InetBackend, SocketOpts]),
 	     {Socket, IpPort}             = socket_open(Domain, PortInfo,
+                                                        InetBackend,
                                                         SocketOpts),
+             SockMRef = inet:monitor(Socket),
              ?vtrace("socket opened:"
-                     "~n      Socket:  ~p"
-                     "~n      Port No: ~p", [Socket, IpPort]),
+                     "~n      Socket:   ~p"
+                     "~n      Port No:  ~p"
+                     "~n      Info:     ~p",
+                     [Socket, IpPort, inet:info(Socket)]),
+
              %% Should we really do this here?
              %% If Kind =:= trap_sender, we only need to receive after 
              %% we have sent an inform!
 	     active_once(Socket),
+             ?vtrace("socket activated:"
+                     "~n      Info: ~p", [inet:info(Socket)]),
 	     #transport{
-                socket    = Socket,
-                kind      = Kind,
-                domain    = Domain,
+                socket       = Socket,
+                mref         = SockMRef,
+                kind         = Kind,
+                domain       = Domain,
                 %% We may not have explicitly specified the port ('system'
                 %% or a range), so it could have been "generated".
                 %% Also, shall we push this into the transport (handled by the
                 %% FRAMEWORK MIB)? Would not work for ephemeral sockets.
-                address   = IpAddr,
-                port_no   = IpPort,
-                port_info = PortInfo,
-                ephm      = Ephm,
-                opts      = SocketOpts}
+                address      = IpAddr,
+                port_no      = IpPort,
+                port_info    = PortInfo,
+                ephm         = Ephm,
+                inet_backend = InetBackend,
+                opts         = SocketOpts}
              %% We need to fix this also
 	 end || {Domain, Address, Kind, RawSocketOpts} <- RawTransports]
     of
@@ -401,7 +414,7 @@ format_address(Address) ->
     iolist_to_binary(snmp_conf:mk_addr_string(Address)).
 
 
-socket_open(snmpUDPDomain = Domain, IpPort, Opts) ->
+socket_open(snmpUDPDomain = Domain, IpPort, InetBackend, Opts) ->
     ?vdebug("socket_open(~p) -> entry with"
             "~n   Port: ~p"
             "~n   Opts: ~p", [Domain, IpPort, Opts]),
@@ -413,7 +426,7 @@ socket_open(snmpUDPDomain = Domain, IpPort, Opts) ->
                     "~n   FD:   ~p"
                     "~n   Port: ~p"
                     "~n   Opts: ~p", [Domain, FD, IpPort, Opts]),
-	    gen_udp_open(0, [{fd, FD} | Opts]);
+	    gen_udp_open(0, InetBackend ++ [{fd, FD} | Opts]);
 	error ->
 	    case init:get_argument(snmpa_fd) of
 		{ok, [[FdStr]]} ->
@@ -423,26 +436,28 @@ socket_open(snmpUDPDomain = Domain, IpPort, Opts) ->
                             "~n   FD:   ~p"
                             "~n   Port: ~p"
                             "~n   Opts: ~p", [Domain, FD, IpPort, Opts]),
-		    gen_udp_open(0, [{fd, FD} | Opts]);
+		    gen_udp_open(0, InetBackend ++ [{fd, FD} | Opts]);
 		error ->
 		    ?vdebug("socket_open(~p) -> plain open"
                             "~n   Port: ~p"
                             "~n   Opts: ~p", [Domain, IpPort, Opts]),
-		    gen_udp_open(IpPort, Opts)
+		    gen_udp_open(IpPort, InetBackend ++ Opts)
 	    end
     end;
-socket_open(Domain, PortInfo, Opts)
+socket_open(Domain, PortInfo, InetBackend, Opts)
   when (Domain =:= transportDomainUdpIpv4) orelse
        (Domain =:= transportDomainUdpIpv6) ->
     ?vdebug("socket_open(~p) -> entry with"
-            "~n   PortInfo: ~p"
-            "~n   Opts:     ~p", [Domain, PortInfo, Opts]),
-    gen_udp_open(PortInfo, Opts);
-socket_open(Domain, PortInfo, Opts) ->
+            "~n      PortInfo:    ~p"
+            "~n      InetBackend: ~p"
+            "~n      Opts:        ~p", [Domain, PortInfo, InetBackend, Opts]),
+    gen_udp_open(PortInfo, InetBackend ++ Opts);
+socket_open(Domain, PortInfo, InetBackend, Opts) ->
     ?vinfo("socket_open(~p) -> entry when invalid with"
-           "~n   PortInfo: ~p"
-           "~n   Opts:     ~p", [Domain, PortInfo, Opts]),
-    throw({socket_open, Domain, Opts}).
+           "~n   PortInfo:    ~p"
+           "~n   InetBackend: ~p"
+           "~n   Opts:        ~p", [Domain, PortInfo, InetBackend, Opts]),
+    throw({socket_open, Domain, InetBackend, Opts}).
 
 
 %% Make the system choose!
@@ -464,7 +479,8 @@ gen_udp_open(system, Opts) ->
     end;
 %% This is for "future compat" since we cannot actually config '0'...
 gen_udp_open(IpPort, Opts) when (IpPort =:= 0) ->
-    ?vtrace("gen_udp_open(0) -> entry"),
+    ?vtrace("gen_udp_open(0) -> entry with"
+            "~n   Opts: ~p", [Opts]),
     case gen_udp:open(IpPort, Opts) of
 	{ok, Socket} ->
             case inet:port(Socket) of
@@ -480,7 +496,8 @@ gen_udp_open(IpPort, Opts) when (IpPort =:= 0) ->
 	    throw({udp_open, {open, IpPort, Reason}})
     end;
 gen_udp_open(IpPort, Opts) when is_integer(IpPort) ->
-    ?vtrace("gen_udp_open(~w) -> entry", [IpPort]),
+    ?vtrace("gen_udp_open(~w) -> entry with"
+            "~n   Opts: ~p", [IpPort, Opts]),
     case gen_udp:open(IpPort, Opts) of
 	{ok, Socket} ->
             ?vtrace("gen_udp_open(~w) -> created: "
@@ -555,7 +572,7 @@ loop(#state{transports = Transports,
             parent     = Parent} = S) ->
     ?vdebug("loop(~p)", [S]),
     receive
-	{udp, Socket, IpAddr, IpPort, Packet} = Msg when is_port(Socket) ->
+        {udp, Socket, IpAddr, IpPort, Packet} = Msg ->
 	    ?vlog("got paket from ~w:~w on ~w", [IpAddr, IpPort, Socket]),
 	    case lists:keyfind(Socket, #transport.socket, Transports) of
 		#transport{socket = Socket, domain = Domain} = Transport ->
@@ -568,7 +585,8 @@ loop(#state{transports = Transports,
 			end,
 		    loop(maybe_handle_recv(S, Transport, From, Packet));
 		false ->
-		    error_msg("Packet on unknown port: ~p", [Msg]),
+		    error_msg("Packet on unknown socket: "
+                              "~n   ~p", [Msg]),
 		    loop(S)
 	    end;
 
@@ -750,17 +768,16 @@ loop(#state{transports = Transports,
 		  "~n   ~p", [Parent, Reason]),
 	    exit(Reason);
 
-        %% We should not do this.
-        %% Future versions of sockets will/may not be linkable (port)
-	{'EXIT', Socket, Reason} when is_port(Socket) ->
+        {'DOWN', _SockMRef, socket, Socket, Reason} ->
 	    case lists:keyfind(Socket, #transport.socket, Transports) of
 		#transport{
-                   socket    = Socket,
-                   domain    = Domain,
-                   port_info = PortInfo,
-                   opts      = SocketOpts,
-                   req_refs  = ReqRefs} = Transport ->
-		    try socket_open(Domain, PortInfo, SocketOpts) of
+                   socket       = Socket,
+                   domain       = Domain,
+                   port_info    = PortInfo,
+                   inet_backend = InetBackend,
+                   opts         = SocketOpts,
+                   req_refs     = ReqRefs} = Transport ->
+		    try socket_open(Domain, PortInfo, InetBackend, SocketOpts) of
 			{NewSocket, PortNo} ->
 			    error_msg(
 			      "Socket ~p exited for reason"
@@ -769,11 +786,13 @@ loop(#state{transports = Transports,
 			      [Socket, Reason, NewSocket, PortNo]),
 			    (length(ReqRefs) < Limit) andalso
 				active_once(NewSocket),
+                            NewSockMRef = inet:monitor(NewSocket),
 			    S#state{
 			      transports =
 				  lists:keyreplace(
 				    Socket, #transport.socket, Transports,
 				    Transport#transport{socket  = NewSocket,
+                                                        mref    = NewSockMRef,
                                                         port_no = PortNo})}
 		    catch
 			ReopenReason ->
@@ -787,7 +806,7 @@ loop(#state{transports = Transports,
 		    end;
 		false ->
 		    error_msg(
-		      "Exit message from port ~p for reason ~p~n",
+		      "Exit message from socket ~p for reason ~p~n",
 		      [Socket, Reason]),
 		    loop(S)
 	    end;
@@ -806,7 +825,6 @@ loop(#state{transports = Transports,
 	    loop(S)
     end.
 
-
 handle_udp_error(S, #transport{socket = Socket,
                                kind   = Kind}, Error) ->
     try inet:sockname(Socket) of
@@ -1702,7 +1720,7 @@ toname(Else) ->
 
 active_once(Sock) ->
     ?vtrace("activate once", []),
-    inet:setopts(Sock, [{active, once}]).
+    ok = inet:setopts(Sock, [{active, once}]).
 
 
 select_transport(_, []) ->
@@ -1988,7 +2006,7 @@ socket_opts(Domain, {IpAddr, PortInfo}, SocketOpts, DefaultOpts) ->
             "~n      Domain:      ~p"
             "~n      IpAddr:      ~p"
             "~n      PortInfo:    ~p"
-            "~n      SpocketOpts: ~p"
+            "~n      SocketOpts:  ~p"
             "~n      DefaultOpts: ~p",
             [Domain, IpAddr, PortInfo, SocketOpts, DefaultOpts]),
     Opts =
@@ -2017,12 +2035,12 @@ socket_opts(Domain, {IpAddr, PortInfo}, SocketOpts, DefaultOpts) ->
              Sz ->
                  [{recbuf, Sz}]
          end ++
-         case get_sndbuf(SocketOpts, DefaultOpts) of
-             use_default ->
-                 [];
-             Sz ->
-		 [{sndbuf, Sz}]
-	 end
+             case get_sndbuf(SocketOpts, DefaultOpts) of
+                 use_default ->
+                     [];
+                 Sz ->
+                     [{sndbuf, Sz}]
+             end
         ] ++
         case get_extra_sock_opts(SocketOpts, DefaultOpts) of
             ESO when is_list(ESO) ->
@@ -2032,11 +2050,18 @@ socket_opts(Domain, {IpAddr, PortInfo}, SocketOpts, DefaultOpts) ->
                           "~n   ~p", [BadESO]),
                 []
         end,
+    InetBackend =
+        case get_inet_backend(SocketOpts, DefaultOpts) of
+            use_default ->
+                [];
+            Backend when (Backend =:= inet) orelse (Backend =:= socket) ->
+                [{inet_backend, Backend}]
+        end,
     %% <EPHEMERAL-FOR-FUTUR-USE>
     %% Ephm = get_ephemeral(SocketOpts),
     %% {Ephm, PortInfo, Opts}.
     %% </EPHEMERAL-FOR-FUTUR-USE>
-    {none, IpAddr, PortInfo, Opts}.
+    {none, IpAddr, PortInfo, InetBackend, Opts}.
 
 
 %% ----------------------------------------------------------------
@@ -2093,6 +2118,9 @@ get_no_reuse_address(Opts, DefaultOpts) ->
 get_extra_sock_opts(Opts, DefaultOpts) ->
     get_socket_opt(extra_sock_opts, Opts, DefaultOpts, []).
 
+get_inet_backend(Opts, DefaultOpts) -> 
+    get_socket_opt(inet_backend, Opts, DefaultOpts, use_default).
+
 %% <EPHEMERAL-FOR-FUTUR-USE>
 %% This is not realy a socket option, but rather socket 'meta'
 %% information. Its still put together with the actual socket
@@ -2157,7 +2185,7 @@ get_info(#state{transports = Transports, reqs = Reqs}) ->
                          transport_kind => Kind,
                          port_info      => PortInfo,
                          opts           => Opts,
-                         socket_info    => get_port_info(Socket),
+                         socket_info    => get_socket_info(Socket),
                          num_reqs       => length(Refs)} ||
                           #transport{socket    = Socket,
                                      domain    = Domain,
@@ -2178,35 +2206,8 @@ proc_mem(P) when is_pid(P) ->
 %% proc_mem(_) ->
 %%     undefined.
 
-get_port_info(Id) ->
-    PortInfo = 
-	case (catch erlang:port_info(Id)) of
-	    PI when is_list(PI) ->
-		[{port_info, PI}];
-	    _ ->
-		[]
-	end,
-    PortStatus = 
-	case (catch prim_inet:getstatus(Id)) of
-	    {ok, PS} ->
-		[{port_status, PS}];
-	    _ ->
-		[]
-	end,
-    PortAct = 
-	case (catch inet:getopts(Id, [active])) of
-	    {ok, PA} ->
-		[{port_act, PA}];
-	    _ ->
-		[]
-	end,
-    PortStats = 
-	case (catch inet:getstat(Id)) of
-	    {ok, Stat} ->
-		[{port_stats, Stat}];
-	    _ ->
-		[]
-	end,
+get_socket_info(Id) when is_port(Id) ->
+    Info = inet:info(Id),
     IfList = 
 	case (catch inet:getif(Id)) of
 	    {ok, IFs} ->
@@ -2221,13 +2222,29 @@ get_port_info(Id) ->
 	    _ ->
 		[]
 	end,
-    [{socket, Id}] ++ 
-	IfList ++ 
-	PortStats ++ 
-	PortInfo ++ 
-	PortStatus ++ 
-	PortAct ++ 
-	BufSz.
+    [{socket, Id}, {info, Info}] ++ IfList ++ BufSz;
+get_socket_info(Id) ->
+    Info = inet:info(Id),
+
+    %% Does not exist for 'socket'
+    IfList = [],
+	%% case (catch inet:getif(Id)) of
+	%%     {ok, IFs} ->
+	%% 	[{interfaces, IFs}];
+	%%     _ ->
+	%% 	[]
+	%% end,
+
+    BufSz = 
+	case (catch inet:getopts(Id, [recbuf, sndbuf])) of
+	    {ok, Sz} ->
+		[{buffer_size, Sz}];
+	    _ ->
+		[]
+	end,
+
+    [{socket, Id}, {info, Info}] ++ IfList ++ BufSz.
+
 
 
 %% ---------------------------------------------------------------
diff --git a/lib/snmp/src/manager/snmpm_net_if.erl b/lib/snmp/src/manager/snmpm_net_if.erl
index 1eb5ae216a..5ff8f91a6e 100644
--- a/lib/snmp/src/manager/snmpm_net_if.erl
+++ b/lib/snmp/src/manager/snmpm_net_if.erl
@@ -1,7 +1,7 @@
 %% 
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 2004-2020. All Rights Reserved.
+%% Copyright Ericsson AB 2004-2021. All Rights Reserved.
 %%
 %% Licensed under the Apache License, Version 2.0 (the "License");
 %% you may not use this file except in compliance with the License.
@@ -81,7 +81,11 @@
 
 -record(transport,
 	{socket,
-	 domain = snmpUDPDomain}).
+         port_info,
+         opts,
+	 domain       = snmpUDPDomain,
+         inet_backend = []
+        }).
 
 -define(DEFAULT_FILTER_MODULE, snmpm_net_if_filter).
 -define(DEFAULT_FILTER_OPTS,   [{module, ?DEFAULT_FILTER_MODULE}]).
@@ -285,15 +289,29 @@ do_init(Server, NoteStore) ->
     ?vdebug("Log: ~w", [Log]),
 
     {ok, DomainAddresses} = snmpm_config:system_info(transports),
-    ?vdebug("DomainAddresses: ~w",[DomainAddresses]),
+    ?vdebug("DomainAddresses: ~w", [DomainAddresses]),
     CommonSocketOpts = common_socket_opts(Opts),
-    BindTo = get_opt(Opts, bind_to,  false),
+    BindTo = get_opt(Opts, bind_to, false),
+    InetBackend = case get_opt(Opts, inet_backend, use_default) of
+                      use_default -> [];
+                      IB          -> [{inet_backend, IB}]
+                  end,
     case
 	[begin
 	     {IpPort, SocketOpts} =
 		 socket_params(Domain, Address, BindTo, CommonSocketOpts),
-	     Socket = socket_open(IpPort, SocketOpts),
-	     #transport{socket = Socket, domain = Domain}
+             %% The 'inet-backend' option has to be first,
+             %% so we might as well add it last.
+	     Socket = socket_open(IpPort, InetBackend ++ SocketOpts),
+             ?vtrace("socket created: "
+                     "~n      Ip Port:     ~p"
+                     "~n      Socket Opts: ~p"
+                     "~n      Socket:      ~p", [IpPort, SocketOpts, Socket]),
+	     #transport{socket       = Socket,
+                        port_info    = IpPort,
+                        opts         = SocketOpts,
+                        inet_backend = InetBackend,
+                        domain       = Domain}
 	 end || {Domain, Address} <- DomainAddresses]
     of
 	[] ->
@@ -318,9 +336,9 @@ do_init(Server, NoteStore) ->
     end.
 
 socket_open(IpPort, SocketOpts) ->
-    ?vtrace("socket_open -> entry with~n"
-	    "   IpPort:     ~p~n"
-	    "   SocketOpts: ~p", [IpPort, SocketOpts]),
+    ?vtrace("socket_open -> entry with"
+	    "~n      IpPort:     ~p"
+	    "~n      SocketOpts: ~p", [IpPort, SocketOpts]),
     case gen_udp:open(IpPort, SocketOpts) of
 	{error, _} = Error ->
 	    throw(Error);
@@ -354,6 +372,7 @@ socket_params(Domain, {IpAddr, IpPort} = Addr, BindTo, CommonSocketOpts) ->
 	_ ->
 	    socket_params(SocketOpts, Addr, BindTo)
     end.
+
 %%
 socket_params(SocketOpts, {IpAddr, IpPort}, BindTo) ->
     case BindTo of
@@ -1253,9 +1272,9 @@ error_msg(F, A) ->
 
 %%%-------------------------------------------------------------------
 
-% get_opt(Key, Opts) ->
-%     ?vtrace("get option ~w", [Key]),
-%     snmp_misc:get_option(Key, Opts).
+%% get_opt(Key, Opts) ->
+%%     ?vtrace("get option ~w", [Key]),
+%%     snmp_misc:get_option(Key, Opts).
 
 get_opt(Opts, Key, Def) ->
     ?vtrace("get option ~w with default ~p", [Key, Def]),
@@ -1265,10 +1284,19 @@ get_opt(Opts, Key, Def) ->
 %% -------------------------------------------------------------------
 
 get_info(#state{transports = Transports}) ->
-    ProcSize = proc_mem(self()),
-    [{process_memory, ProcSize}
-     | [{port_info, get_port_info(Socket)}
-	|| #transport{socket = Socket} <- Transports]].
+    ProcSize      = proc_mem(self()),
+    Counters      = get_counters(),
+    TransportInfo = [#{tdomain     => Domain,
+                       port_info   => PI,
+                       opts        => Opts,
+                       socket_info => get_socket_info(Socket)} ||
+                        #transport{socket    = Socket,
+                                   port_info = PI,
+                                   opts      = Opts,
+                                   domain    = Domain} <- Transports],
+    [{counters,       Counters},
+     {process_memory, ProcSize},
+     {transport_info, TransportInfo}].
 
 proc_mem(P) when is_pid(P) ->
     case (catch erlang:process_info(P, memory)) of
@@ -1279,35 +1307,9 @@ proc_mem(P) when is_pid(P) ->
     end.
 
 
-get_port_info(Id) ->
-    PortInfo = 
-	case (catch erlang:port_info(Id)) of
-	    PI when is_list(PI) ->
-		[{port_info, PI}];
-	    _ ->
-		[]
-	end,
-    PortStatus = 
-	case (catch prim_inet:getstatus(Id)) of
-	    {ok, PS} ->
-		[{port_status, PS}];
-	    _ ->
-		[]
-	end,
-    PortAct = 
-	case (catch inet:getopts(Id, [active])) of
-	    {ok, PA} ->
-		[{port_act, PA}];
-	    _ ->
-		[]
-	end,
-    PortStats = 
-	case (catch inet:getstat(Id)) of
-	    {ok, Stat} ->
-		[{port_stats, Stat}];
-	    _ ->
-		[]
-	end,
+get_socket_info(Id) when is_port(Id) ->
+    Info = inet:info(Id),
+
     IfList = 
 	case (catch inet:getif(Id)) of
 	    {ok, IFs} ->
@@ -1315,6 +1317,29 @@ get_port_info(Id) ->
 	    _ ->
 		[]
 	end,
+
+    BufSz = 
+	case (catch inet:getopts(Id, [recbuf, sndbuf, buffer])) of
+	    {ok, Sz} ->
+		[{buffer_size, Sz}];
+	    _ ->
+		[]
+	end,
+
+    [{socket, Id}, {info, Info}] ++ IfList ++ BufSz;
+
+get_socket_info(Id) ->
+    Info = inet:info(Id),
+
+    %% Does not exist for 'socket' ... yet
+    %% IfList = 
+    %%     case (catch inet:getif(Id)) of
+    %%         {ok, IFs} ->
+    %%     	[{interfaces, IFs}];
+    %%         _ ->
+    %%     	[]
+    %%     end,
+
     BufSz = 
 	case (catch inet:getopts(Id, [recbuf, sndbuf, buffer])) of
 	    {ok, Sz} ->
@@ -1322,13 +1347,9 @@ get_port_info(Id) ->
 	    _ ->
 		[]
 	end,
-    [{socket, Id}] ++ 
-	IfList ++ 
-	PortStats ++ 
-	PortInfo ++ 
-	PortStatus ++ 
-	PortAct ++
-	BufSz.
+
+    [{socket, Id}, {info, Info}] ++ BufSz.
+
 
 
 %%-----------------------------------------------------------------
@@ -1356,6 +1377,20 @@ counters() ->
 inc(Name)    -> inc(Name, 1).
 inc(Name, N) -> snmpm_config:incr_stats_counter(Name, N).
 
+get_counters() ->
+    Counters = counters(),
+    get_counters(Counters, []).
+
+get_counters([], Acc) ->
+    lists:reverse(Acc);
+get_counters([Counter|Counters], Acc) ->
+    case snmpm_config:get_stats_counter(Counter) of
+	{ok, CounterVal} ->
+	    get_counters(Counters, [{Counter, CounterVal}|Acc]);
+	_ ->
+	    get_counters(Counters, Acc)
+    end.
+
 
 %% ----------------------------------------------------------------
 
diff --git a/lib/snmp/src/misc/snmp_misc.erl b/lib/snmp/src/misc/snmp_misc.erl
index 39254503ac..63abb1ac90 100644
--- a/lib/snmp/src/misc/snmp_misc.erl
+++ b/lib/snmp/src/misc/snmp_misc.erl
@@ -455,7 +455,7 @@ bits_to_int([],_Kibbles,Res) -> Res;
 bits_to_int([Kibble|Ks],Kibbles,Res) ->
     case snmp_misc:assq(Kibble,Kibbles) of
 	{value,V} ->
-	    bits_to_int(Ks,Kibbles,Res + round(math:pow(2,V)));
+	    bits_to_int(Ks, Kibbles, Res + round(math:pow(2,V)));
 	_ ->
 	    error
     end.
diff --git a/lib/snmp/test/snmp_agent_SUITE.erl b/lib/snmp/test/snmp_agent_SUITE.erl
index fc4de668ab..6564c48d70 100644
--- a/lib/snmp/test/snmp_agent_SUITE.erl
+++ b/lib/snmp/test/snmp_agent_SUITE.erl
@@ -26,12 +26,12 @@
 	 init_per_group/2,    end_per_group/2, 
 	 init_per_testcase/2, end_per_testcase/2, 
 
-	 %% all_tcs - misc
+	 %% major_tcs - misc
 	 app_info/1, 
 	 info_test/1, 
          create_local_db_dir/1,
 
-	 %% all_tcs - test_v1
+	 %% major_tcs - test_v1
 	 simple/1, 
 	 db_notify_client/1, 
 	 v1_processing/1, 
@@ -51,7 +51,7 @@
 	 opaque/1, 
 	 change_target_addr_config/1, 
 
-	 %% all_tcs - test_v1 - multiple_reqs
+	 %% major_tcs - test_v1 - multiple_reqs
 	 mul_get/1, 
 	 mul_get_err/1, 
 	 mul_next/1, 
@@ -59,7 +59,7 @@
 	 mul_set/1, 
 	 mul_set_err/1, 
 
-	 %% all_tcs - test_v1 - reported_bugs
+	 %% major_tcs - test_v1 - reported_bugs
 	 otp_1128/1, 
 	 otp_1129/1, 
 	 otp_1131/1, 
@@ -75,7 +75,7 @@
 	 otp_3187/1, 
 	 otp_3725/1, 
 
-	 %% all_tcs - test_v1 - standard_mibs
+	 %% major_tcs - test_v1 - standard_mibs
 	 snmp_standard_mib/1, 
 	 snmp_community_mib/1,
 	 snmp_framework_mib/1, 
@@ -83,7 +83,7 @@
 	 snmp_notification_mib/1, 
 	 snmp_view_based_acm_mib/1, 
 
-	 %% all_tcs - test_v2
+	 %% major_tcs - test_v2
 	 simple_2/1, 
 	 v2_processing/1, 
 	 big_2/1, 
@@ -104,7 +104,7 @@
 	 opaque_2/1, 
 	 v2_caps/1,
 
-	 %% all_tcs - test_v2 - multiple_reqs_2
+	 %% major_tcs - test_v2 - multiple_reqs_2
 	 mul_get_2/1, 
 	 mul_get_err_2/1, 
 	 mul_next_2/1, 
@@ -112,10 +112,10 @@
 	 mul_set_2/1, 
 	 mul_set_err_2/1, 
 
-	 %% all_tcs - test_v2 - v2_inform
+	 %% major_tcs - test_v2 - v2_inform
 	 v2_inform_i/1, 
 
-	 %% all_tcs - test_v2 - reported_bugs_2
+	 %% major_tcs - test_v2 - reported_bugs_2
 	 otp_1128_2/1, 
 	 otp_1129_2/1, 
 	 otp_1131_2/1, 
@@ -130,7 +130,7 @@
 	 otp_2979_2/1, 
 	 otp_3187_2/1, 
 
-	 %% all_tcs - test_v2 - standard_mibs_2
+	 %% major_tcs - test_v2 - standard_mibs_2
 	 snmpv2_mib_2/1, 
 	 snmp_community_mib_2/1,
 	 snmp_framework_mib_2/1, 
@@ -138,10 +138,10 @@
 	 snmp_notification_mib_2/1, 
 	 snmp_view_based_acm_mib_2/1,
 
-	 %% all_tcs - test_v1_v2
+	 %% major_tcs - test_v1_v2
 	 simple_bi/1, 
 
-	 %% all_tcs - test_v3
+	 %% major_tcs - test_v3
 	 simple_3/1, 
 	 v3_processing/1, 
 	 big_3/1, 
@@ -162,7 +162,7 @@
 	 opaque_3/1, 
 	 v2_caps_3/1, 
 
-	 %% all_tcs - test_v3 - multiple_reqs_3
+	 %% major_tcs - test_v3 - multiple_reqs_3
 	 mul_get_3/1, 
 	 mul_get_err_3/1, 
 	 mul_next_3/1, 
@@ -170,10 +170,10 @@
 	 mul_set_3/1,
 	 mul_set_err_3/1,
 
-	 %% all_tcs - test_v3 - v3_inform
+	 %% major_tcs - test_v3 - v3_inform
 	 v3_inform_i/1, 
 
-	 %% all_tcs - test_v3 - reported_bugs_3
+	 %% major_tcs - test_v3 - reported_bugs_3
 	 otp_1128_3/1, 
 	 otp_1129_3/1, 
 	 otp_1131_3/1, 
@@ -189,7 +189,7 @@
 	 otp_3187_3/1,
 	 otp_3542/1,
 
-	 %% all_tcs - test_v3 - standard_mibs_3
+	 %% major_tcs - test_v3 - standard_mibs_3
 	 snmpv2_mib_3/1, 
 	 snmp_framework_mib_3/1, 
 	 snmp_mpd_mib_3/1,
@@ -198,17 +198,17 @@
 	 snmp_view_based_acm_mib_3/1, 
 	 snmp_user_based_sm_mib_3/1,
 
-	 %% all_tcs - test_v3 - v3_security
+	 %% major_tcs - test_v3 - v3_security
 	 v3_crypto_basic/1, 
 	 v3_md5_auth/1, 
 	 v3_sha_auth/1,
 	 v3_des_priv/1, 
 
-	 %% all_tcs - test_multi_threaded, test_multi_threaded_ext
+	 %% major_tcs - test_multi_threaded, test_multi_threaded_ext
 	 multi_threaded/1, 
 	 mt_trap/1, 
 	 
-	 %% all_tcs - mib_storage - mib_storage_ets
+	 %% major_tcs - mib_storage - mib_storage_ets
 	 mse_simple/1, 
 	 mse_v1_processing/1, 
 	 mse_big/1, 
@@ -230,7 +230,7 @@
 	 mse_me_of/1,
 	 mse_mib_of/1, 
 
-	 %% all_tcs - mib_storage - mib_storage_dets
+	 %% major_tcs - mib_storage - mib_storage_dets
 	 msd_simple/1, 
 	 msd_v1_processing/1, 
 	 msd_big/1, 
@@ -252,7 +252,7 @@
 	 msd_me_of/1,
 	 msd_mib_of/1, 
 
-	 %% all_tcs - mib_storage - mib_storage_mnesia
+	 %% major_tcs - mib_storage - mib_storage_mnesia
 	 msm_simple/1, 
 	 msm_v1_processing/1, 
 	 msm_big/1, 
@@ -274,28 +274,28 @@
 	 msm_me_of/1,
 	 msm_mib_of/1, 
 
-	 %% all_tcs - mib_storage - mse_size_check
+	 %% major_tcs - mib_storage - mse_size_check
 	 mse_size_check/1, 
 
-	 %% all_tcs - mib_storage - msd_size_check
+	 %% major_tcs - mib_storage - msd_size_check
 	 msd_size_check/1, 
 
-	 %% all_tcs - mib_storage - msm_size_check
+	 %% major_tcs - mib_storage - msm_size_check
 	 msm_size_check/1, 
 
-	 %% all_tcs - mib_storage - varm_mib_storage_dets
+	 %% major_tcs - mib_storage - varm_mib_storage_dets
 	 msd_varm_mib_start/1, 
 
-	 %% all_tcs - mib_storage - varm_mib_storage_mnesia
+	 %% major_tcs - mib_storage - varm_mib_storage_mnesia
 	 msm_varm_mib_start/1, 
 
-	 %% all_tcs - tickets1 - otp4394
+	 %% major_tcs - tickets1 - otp4394
 	 otp_4394/1, 
 
-	 %% all_tcs - tickets1 - otp7157
+	 %% major_tcs - tickets1 - otp7157
 	 otp_7157/1,
 
-         %% all_tcs - tickets1 - otp16092
+         %% major_tcs - tickets1 - otp16092
          otp_16092_simple_start_and_stop1/1,
          otp_16092_simple_start_and_stop2/1,
          otp_16092_simple_start_and_stop3/1,
@@ -526,14 +526,31 @@ suite() ->
     [{ct_hooks, [ts_install_cth]}].
 
 all() -> 
-    %% Reqs  = [mnesia, distribution, {local_slave_nodes, 2}, {time, 360}],
-    Conf1 = [{group, all_tcs}],
-    Conf2 = [{group, tickets2}],
-    Conf1 ++ Conf2.
+    %% This is a temporary messure to ensure that we can 
+    %% test the socket backend without effecting *all*
+    %% applications on *all* machines.
+    %% This flag is set only for *one* host.
+    case ?TEST_INET_BACKENDS() of
+        true ->
+            [
+             {group, inet_backend_default},
+             {group, inet_backend_inet},
+             {group, inet_backend_socket}
+            ];
+        _ ->
+            [
+             {group, inet_backend_default}
+            ]
+    end.
 
 groups() -> 
     [
-     {all_tcs,                       [], all_cases()},
+     {inet_backend_default,          [], inet_backend_default_cases()},
+     {inet_backend_inet,             [], inet_backend_inet_cases()},
+     {inet_backend_socket,           [], inet_backend_socket_cases()},
+
+     {all,                           [], all_cases()},
+     {major_tcs,                     [], major_cases()},
      {mib_storage,                   [], mib_storage_cases()}, 
      {mib_storage_ets,               [], mib_storage_ets_cases()},
      {mib_storage_dets,              [], mib_storage_dets_cases()},
@@ -568,17 +585,32 @@ groups() ->
      {reported_bugs_2,               [], reported_bugs2_cases()}, 
      {reported_bugs_3,               [], reported_bugs3_cases()}, 
      {tickets1,                      [], tickets1_cases()}, 
-     {tickets2,                      [], tickets2_cases()}, 
      {otp4394,                       [], [otp_4394]},
      {otp7157,                       [], [otp_7157]},
      {otp16092,                      [], otp16092_cases()},
+
+     %% These all belong to group 'tickets2'
+     {tickets2,                      [], tickets2_cases()}, 
      {otp16649,                      [], otp16649_cases()},
      {otp16649_ipv4,                 [], otp16649_gen_cases()},
      {otp16649_ipv6,                 [], otp16649_gen_cases()}
     ].
 
 
-all_cases() -> 
+inet_backend_default_cases() ->
+    [{all, [], all_cases()}].
+
+inet_backend_inet_cases() ->
+    [{all, [], all_cases()}].
+
+inet_backend_socket_cases() ->
+    [{all, [], all_cases()}].
+
+
+%% The agent and the nodes of the agent and manager
+%% is started at group init and then lives until
+%% group end!
+major_cases() ->
     [
      {group, misc}, 
      {group, test_v1}, 
@@ -594,6 +626,53 @@ all_cases() ->
      {group, mib_storage},
      {group, tickets1}
     ].
+    
+all_cases() -> 
+    [
+     %% The agent and the nodes of the agent and manager
+     %% is started at group init and then lives until
+     %% group end!
+     {group, major_tcs},
+
+     %% The test cases in the 'tickets2' group
+     %% require control of start and stop of agents and inodes!
+     {group, tickets2}
+    ].
+
+
+tickets1_cases() ->
+    [
+     {group, otp4394}, 
+     {group, otp7157}, 
+     {group, otp16092}
+    ].
+
+
+tickets2_cases() ->
+    [
+     otp8395, 
+     otp9884,
+     {group, otp16649}
+    ].
+
+otp16649_cases() ->
+    [
+     {group, otp16649_ipv4},
+     {group, otp16649_ipv6}
+    ].
+
+otp16649_gen_cases() ->
+    [
+     otp16649_1,
+     otp16649_2,
+     otp16649_3,
+     otp16649_4,
+     otp16649_5,
+     otp16649_6,
+     otp16649_7
+    ].
+
+
 
 %%
 %% -----
@@ -603,7 +682,12 @@ init_per_suite(Config0) when is_list(Config0) ->
 
     ?IPRINT("init_per_suite -> entry with"
             "~n   Config: ~p"
-            "~n   Nodes:  ~p", [Config0, erlang:nodes()]),
+            "~n   Nodes:  ~p"
+            "~n   explicit inet backend: ~p"
+            "~n   test inet backends:    ~p",
+            [Config0, erlang:nodes(),
+             ?EXPLICIT_INET_BACKEND(),
+             ?TEST_INET_BACKENDS()]),
 
     case ?LIB:init_per_suite(Config0) of
         {skip, _} = SKIP ->
@@ -660,125 +744,133 @@ end_per_suite(Config0) when is_list(Config0) ->
 %% -----
 %%
 
-init_per_group(all_tcs = GroupName, Config) ->
+init_per_group(GroupName, Config0) ->
+    ?IPRINT("init_per_group -> entry with"
+            "~n      GroupName: ~p"
+            "~n      Config:    ~p"
+            "~n   when"
+            "~n      Nodes:     ~p",
+            [GroupName, Config0, nodes()]),
+
+    Config1 = init_per_group2(GroupName, Config0),
+
+    ?IPRINT("init_per_group -> done when"
+            "~n      GroupName: ~p"
+            "~n      Config:    ~p"
+            "~n      Nodes:     ~p",
+            [GroupName, Config1, nodes()]),
+
+    Config1.
+
+
+init_per_group2(inet_backend_default = _GroupName, Config) ->
+    snmp_test_lib:init_group_top_dir(default, [{socket_create_opts, []} | Config]);
+init_per_group2(inet_backend_inet = _GroupName, Config) ->
+    case ?EXPLICIT_INET_BACKEND() of
+        true ->
+            %% The environment trumps us,
+            %% so only the default group should be run!
+            {skip, "explicit inet backend"};
+        false ->
+            snmp_test_lib:init_group_top_dir(inet, [{socket_create_opts, [{inet_backend, inet}]} | Config])
+    end;
+init_per_group2(inet_backend_socket = _GroupName, Config) ->
+    case ?EXPLICIT_INET_BACKEND() of
+        true ->
+            %% The environment trumps us,
+            %% so only the default group should be run!
+            {skip, "explicit inet backend"};
+        false ->
+            snmp_test_lib:init_group_top_dir(socket, [{socket_create_opts, [{inet_backend, socket}]} | Config])
+    end;
+init_per_group2(major_tcs = GroupName, Config) ->
     init_all(snmp_test_lib:init_group_top_dir(GroupName, Config));
-init_per_group(otp7157 = GroupName, Config) -> 
+init_per_group2(otp7157 = GroupName, Config) -> 
     otp_7157_init(snmp_test_lib:init_group_top_dir(GroupName, Config));
-init_per_group(otp4394 = GroupName, Config) -> 
+init_per_group2(otp4394 = GroupName, Config) -> 
     otp_4394_init(snmp_test_lib:init_group_top_dir(GroupName, Config));
-init_per_group(v2_inform = GroupName, Config) -> 
+init_per_group2(v2_inform = GroupName, Config) -> 
     init_v2_inform(snmp_test_lib:init_group_top_dir(GroupName, Config));
-init_per_group(v3_inform = GroupName, Config) -> 
+init_per_group2(v3_inform = GroupName, Config) -> 
     init_v3_inform(snmp_test_lib:init_group_top_dir(GroupName, Config));
-init_per_group(multiple_reqs = GroupName, Config) -> 
+init_per_group2(multiple_reqs = GroupName, Config) -> 
     init_mul(snmp_test_lib:init_group_top_dir(GroupName, Config));
-init_per_group(multiple_reqs_2 = GroupName, Config) -> 
+init_per_group2(multiple_reqs_2 = GroupName, Config) -> 
     init_mul(snmp_test_lib:init_group_top_dir(GroupName, Config));
-init_per_group(multiple_reqs_3 = GroupName, Config) -> 
+init_per_group2(multiple_reqs_3 = GroupName, Config) -> 
     init_mul(snmp_test_lib:init_group_top_dir(GroupName, Config));
-init_per_group(test_multi_threaded = GroupName, Config) -> 
+init_per_group2(test_multi_threaded = GroupName, Config) -> 
     init_mt(snmp_test_lib:init_group_top_dir(GroupName, Config), true);
-init_per_group(test_multi_threaded_ext = GroupName, Config) -> 
+init_per_group2(test_multi_threaded_ext = GroupName, Config) -> 
     init_mt(snmp_test_lib:init_group_top_dir(GroupName, Config), extended);
-init_per_group(test_v3 = GroupName, Config) -> 
+init_per_group2(test_v3 = GroupName, Config) -> 
     case snmp_test_lib:crypto_start() of
         ok ->
             init_v3(snmp_test_lib:init_group_top_dir(GroupName, Config));
         _ ->
             {skip, "Crypto did not start"}
     end;
-init_per_group(test_v1_v2 = GroupName, Config) -> 
+init_per_group2(test_v1_v2 = GroupName, Config) -> 
     init_v1_v2(snmp_test_lib:init_group_top_dir(GroupName, Config));
-init_per_group(test_v2 = GroupName, Config) -> 
+init_per_group2(test_v2 = GroupName, Config) -> 
     init_v2(snmp_test_lib:init_group_top_dir(GroupName, Config));
-init_per_group(test_v1 = GroupName, Config) -> 
+init_per_group2(test_v1 = GroupName, Config) -> 
     init_v1(snmp_test_lib:init_group_top_dir(GroupName, Config));
-init_per_group(test_v1_ipv6 = GroupName, Config) ->
+init_per_group2(test_v1_ipv6 = GroupName, Config) ->
     init_per_group_ipv6(GroupName, Config, fun init_v1/1);
-init_per_group(test_v2_ipv6 = GroupName, Config) ->
+init_per_group2(test_v2_ipv6 = GroupName, Config) ->
     init_per_group_ipv6(GroupName, Config, fun init_v2/1);
-init_per_group(test_v1_v2_ipv6 = GroupName, Config) ->
+init_per_group2(test_v1_v2_ipv6 = GroupName, Config) ->
     init_per_group_ipv6(GroupName, Config, fun init_v1_v2/1);
-init_per_group(test_v3_ipv6 = GroupName, Config) ->
+init_per_group2(test_v3_ipv6 = GroupName, Config) ->
     init_per_group_ipv6(GroupName, Config, fun init_v3/1);
-init_per_group(misc = GroupName, Config) -> 
+init_per_group2(misc = GroupName, Config) -> 
     init_misc(snmp_test_lib:init_group_top_dir(GroupName, Config));
-init_per_group(mib_storage_varm_mnesia = GroupName, Config) -> 
+init_per_group2(mib_storage_varm_mnesia = GroupName, Config) -> 
     init_varm_mib_storage_mnesia(snmp_test_lib:init_group_top_dir(GroupName, 
 								  Config));
-init_per_group(mib_storage_varm_dets = GroupName, Config) -> 
-    ?DBG("init_per_group(mib_storage_varm_dets) -> entry with"
-	 "~n   Config: ~p", [Config]),    
+init_per_group2(mib_storage_varm_dets = GroupName, Config) -> 
     init_varm_mib_storage_dets(
       snmp_test_lib:init_group_top_dir(GroupName, Config));
-init_per_group(mib_storage_size_check_mnesia = GroupName, Config) -> 
+init_per_group2(mib_storage_size_check_mnesia = GroupName, Config) -> 
        case snmp_test_lib:crypto_start() of
            ok ->
                init_size_check_msm(snmp_test_lib:init_group_top_dir(GroupName, Config));
            _ ->
                {skip, "Crypto did not start"}
        end;
-init_per_group(mib_storage_size_check_dets = GroupName, Config) -> 
+init_per_group2(mib_storage_size_check_dets = GroupName, Config) -> 
        case snmp_test_lib:crypto_start() of
            ok ->
                init_size_check_msm(snmp_test_lib:init_group_top_dir(GroupName, Config));
            _ ->
                {skip, "Crypto did not start"}
        end;
-init_per_group(mib_storage_size_check_ets = GroupName, Config) -> 
-           case snmp_test_lib:crypto_start() of
-           ok ->
-               init_size_check_msm(snmp_test_lib:init_group_top_dir(GroupName, Config));
-           _ ->
-               {skip, "Crypto did not start"}
-       end;
-init_per_group(mib_storage_mnesia = GroupName, Config) -> 
+init_per_group2(mib_storage_size_check_ets = GroupName, Config) -> 
+    case snmp_test_lib:crypto_start() of
+        ok ->
+            init_size_check_msm(snmp_test_lib:init_group_top_dir(GroupName, Config));
+        _ ->
+            {skip, "Crypto did not start"}
+    end;
+init_per_group2(mib_storage_mnesia = GroupName, Config) -> 
     init_mib_storage_mnesia(snmp_test_lib:init_group_top_dir(GroupName, 
 							     Config));
-init_per_group(mib_storage_dets = GroupName, Config) -> 
+init_per_group2(mib_storage_dets = GroupName, Config) -> 
     init_mib_storage_dets(snmp_test_lib:init_group_top_dir(GroupName, Config));
-init_per_group(mib_storage_ets = GroupName, Config) -> 
+init_per_group2(mib_storage_ets = GroupName, Config) -> 
     init_mib_storage_ets(snmp_test_lib:init_group_top_dir(GroupName, Config));
-init_per_group(otp16649_ipv4 = GroupName, Config) -> 
+init_per_group2(otp16649_ipv4 = GroupName, Config) -> 
     Config2 = [{ip,       ?LOCALHOST(inet)},
                {ipfamily, inet},
                {tdomain,  transportDomainUdpIpv4} |
                lists:keydelete(ip, 1, Config)],
     snmp_test_lib:init_group_top_dir(GroupName, Config2);
-init_per_group(otp16649_ipv6 = GroupName, Config) ->
+init_per_group2(otp16649_ipv6 = GroupName, Config) ->
     init_per_group_ipv6(GroupName,
                         [{tdomain,  transportDomainUdpIpv6} | Config],
                         fun(C) -> C end);
-    %% SupportsIPv6 =
-    %%     case ?HAS_SUPPORT_IPV6() of
-    %%         true ->
-    %%             case os:type() of
-    %%                 {unix, netbsd} ->
-    %%                     {false, "Host *may* not *properly* support IPV6"};
-    %%                 {unix, darwin} ->
-    %%                     case os:version() of
-    %%                         V > {9, 8, 0} ->
-    %%                             true;
-    %%                         _ ->
-    %%                             {false, "Host *may* not *properly* support IPV6"};
-    %%                     end;
-    %%                 _ ->
-    %%                     true
-    %%             end;
-    %%         false ->
-    %%             {false, "Host does not support IPv6"}
-    %%     end,
-    %% case SupportsIPv6 of
-    %%     true ->
-    %%         Config2 = [{ip,       ?LOCALHOST(inet6)},
-    %%                    {ipfamily, inet6},
-    %%                    {tdomain,  transportDomainUdpIpv6} |
-    %%                    lists:keydelete(ip, 1, Config)],
-    %%         snmp_test_lib:init_group_top_dir(GroupName, Config2);
-    %%     {false, SkipReason} ->
-    %%         {skip, SkipReason}
-    %% end;
-init_per_group(GroupName, Config) ->
+init_per_group2(GroupName, Config) ->
     snmp_test_lib:init_group_top_dir(GroupName, Config).
 
 init_per_group_ipv6(GroupName, Config, Init) ->
@@ -820,61 +912,78 @@ init_per_group_ipv6(GroupName, Config, Init) ->
             end
     end.
 
-end_per_group(all_tcs, Config) ->
+
+end_per_group(GroupName, Config) ->
+    ?IPRINT("end_per_group -> entry with"
+            "~n      GroupName: ~p"
+            "~n      Config:    ~p"
+            "~n   when"
+            "~n      Nodes:     ~p",
+            [GroupName, Config, nodes()]),
+
+    Config1 = end_per_group2(GroupName, Config),
+
+    ?IPRINT("end_per_group -> done when"
+            "~n      Nodes:     ~p",
+            [nodes()]),
+
+    Config1.
+
+end_per_group2(major_tcs, Config) ->
     finish_all(Config);
-end_per_group(otp7157, Config) -> 
+end_per_group2(otp7157, Config) -> 
     otp_7157_finish(Config);
-end_per_group(otp4394, Config) -> 
+end_per_group2(otp4394, Config) -> 
     otp_4394_finish(Config);
-end_per_group(v2_inform, Config) -> 
+end_per_group2(v2_inform, Config) -> 
     finish_v2_inform(Config);
-end_per_group(v3_inform, Config) -> 
+end_per_group2(v3_inform, Config) -> 
     finish_v3_inform(Config);
-end_per_group(multiple_reqs, Config) -> 
+end_per_group2(multiple_reqs, Config) -> 
     finish_mul(Config);
-end_per_group(multiple_reqs_2, Config) -> 
+end_per_group2(multiple_reqs_2, Config) -> 
     finish_mul(Config);
-end_per_group(multiple_reqs_3, Config) -> 
+end_per_group2(multiple_reqs_3, Config) -> 
     finish_mul(Config);
-end_per_group(test_multi_threaded, Config) -> 
+end_per_group2(test_multi_threaded, Config) -> 
     finish_mt(Config);
-end_per_group(test_multi_threaded_ext, Config) -> 
+end_per_group2(test_multi_threaded_ext, Config) -> 
     finish_mt(Config);
-end_per_group(test_v3_ipv6, Config) ->
+end_per_group2(test_v3_ipv6, Config) ->
     finish_v3(Config);
-end_per_group(test_v1_v2_ipv6, Config) ->
+end_per_group2(test_v1_v2_ipv6, Config) ->
     finish_v1_v2(Config);
-end_per_group(test_v2_ipv6, Config) ->
+end_per_group2(test_v2_ipv6, Config) ->
     finish_v2(Config);
-end_per_group(test_v1_ipv6, Config) ->
+end_per_group2(test_v1_ipv6, Config) ->
     finish_v1(Config);
-end_per_group(test_v3, Config) ->
+end_per_group2(test_v3, Config) ->
     finish_v3(Config);
-end_per_group(test_v1_v2, Config) ->
+end_per_group2(test_v1_v2, Config) ->
     finish_v1_v2(Config);
-end_per_group(test_v2, Config) ->
+end_per_group2(test_v2, Config) ->
     finish_v2(Config);
-end_per_group(test_v1, Config) ->
+end_per_group2(test_v1, Config) ->
     finish_v1(Config);
-end_per_group(misc, Config) ->
+end_per_group2(misc, Config) ->
     finish_misc(Config);
-end_per_group(mib_storage_varm_mnesia, Config) ->
+end_per_group2(mib_storage_varm_mnesia, Config) ->
     finish_varm_mib_storage_mnesia(Config);
-end_per_group(mib_storage_varm_dets, Config) ->
+end_per_group2(mib_storage_varm_dets, Config) ->
     finish_varm_mib_storage_dets(Config);
-end_per_group(mib_storage_size_check_mnesia, Config) ->
+end_per_group2(mib_storage_size_check_mnesia, Config) ->
     finish_size_check_msm(Config);
-end_per_group(mib_storage_size_check_dets, Config) ->
+end_per_group2(mib_storage_size_check_dets, Config) ->
     finish_size_check_msd(Config);
-end_per_group(mib_storage_size_check_ets, Config) ->
+end_per_group2(mib_storage_size_check_ets, Config) ->
     finish_size_check_mse(Config);
-end_per_group(mib_storage_mnesia, Config) ->
+end_per_group2(mib_storage_mnesia, Config) ->
     finish_mib_storage_mnesia(Config);
-end_per_group(mib_storage_dets, Config) ->
+end_per_group2(mib_storage_dets, Config) ->
     finish_mib_storage_dets(Config);
-end_per_group(mib_storage_ets, Config) ->
+end_per_group2(mib_storage_ets, Config) ->
     finish_mib_storage_ets(Config);
-end_per_group(_GroupName, Config) ->
+end_per_group2(_GroupName, Config) ->
     Config.
 
 
@@ -7025,14 +7134,6 @@ otp_3725_test(MaNode) ->
 %% Slogan: Target mib tag list check invalid
 %%-----------------------------------------------------------------
 
-tickets1_cases() ->
-    [
-     {group, otp4394}, 
-     {group, otp7157}, 
-     {group, otp16092}
-    ].
-
-
 otp_4394_init(Config) when is_list(Config) ->
     ?DBG("otp_4394_init -> entry with"
 	   "~n   Config: ~p", [Config]),
@@ -7398,31 +7499,6 @@ otp16092_try_start_and_stop_agent(Node, Opts, Expected) ->
 %% These cases are started in the new way
 %%-----------------------------------------------------------------
 
-tickets2_cases() ->
-    [
-     otp8395, 
-     otp9884,
-     {group, otp16649}
-    ].
-
-otp16649_cases() ->
-    [
-     {group, otp16649_ipv4},
-     {group, otp16649_ipv6}
-    ].
-
-otp16649_gen_cases() ->
-    [
-     otp16649_1,
-     otp16649_2,
-     otp16649_3,
-     otp16649_4,
-     otp16649_5,
-     otp16649_6,
-     otp16649_7
-    ].
-
-
 otp8395({init, Config}) when is_list(Config) ->
     ?DBG("otp8395(init) -> entry with"
 	 "~n   Config: ~p", [Config]),
@@ -7430,9 +7506,9 @@ otp8395({init, Config}) when is_list(Config) ->
     %% --
     %% Start nodes
     %%
-
-    {ok, AgentNode}    = start_node(agent),
-    {ok, ManagerNode}  = start_node(manager),
+    FName              = ?FUNCTION_NAME,
+    {ok, AgentNode}    = start_node(mk_node_name(FName, agent)),
+    {ok, ManagerNode}  = start_node(mk_node_name(FName, manager)),
 
     %% -- 
     %% Mnesia init
@@ -7580,7 +7656,7 @@ otp8395(Config) when is_list(Config) ->
 otp9884({init, Config}) when is_list(Config) ->
     ?DBG("otp9884(init) -> entry with"
 	 "~n   Config: ~p", [Config]),
-    init_v1_agent([{ipfamily, inet} | Config]);
+    init_v1_agent([{fname, otp9884}, {ipfamily, inet} | Config]);
 
 otp9884({fin, Config}) when is_list(Config) ->
     ?DBG("otp9884(fin) -> entry with"
@@ -8024,8 +8100,12 @@ otp16649_init(N, AgentPreTransports, Config) ->
          "~n   Config2: ~p", [Config3]),
     [{agent_raw_transports, AgentPreTransports} | Config3].
 
+mk_node_name(FName, Post) when is_atom(FName) andalso is_atom(Post) ->
+    list_to_atom(?F("~w_~w", [FName, Post])).
+
 otp16649_mk_name(N, Post) when is_integer(N) andalso is_atom(Post) ->
-    list_to_atom(?F("otp16649_~w_~w", [N, Post])).
+    mk_node_name(otp16649, list_to_atom(?F("~w_~w", [N, Post]))).
+%% list_to_atom(?F("otp16649_~w_~w", [N, Post])).
 
 
 otp16649_fin(N, Config) when is_integer(N) ->
@@ -8241,13 +8321,15 @@ start_agent(Config) ->
 start_agent(Config, Opts) ->
 
     %% Directories
-    ConfDir = ?config(agent_conf_dir, Config),
-    DbDir   = ?config(agent_db_dir,   Config),
-    LogDir  = ?config(agent_log_dir,  Config),
+    ConfDir     = ?config(agent_conf_dir,     Config),
+    DbDir       = ?config(agent_db_dir,       Config),
+    LogDir      = ?config(agent_log_dir,      Config),
+    InetBackend = ?config(socket_create_opts, Config),
  
     Vsns = [v1], 
 
-    AgentConfig = process_agent_options(ConfDir, DbDir, LogDir, Vsns, Opts),
+    AgentConfig = process_agent_options(ConfDir, DbDir, LogDir, Vsns,
+                                        InetBackend, Opts),
     
     %% Nodes
     AgentNode = ?config(agent_node, Config),
@@ -8259,7 +8341,15 @@ start_agent(Config, Opts) ->
     [{agent_sup, AgentTopSup} | Config].
     
 
-process_agent_options(ConfDir, DbDir, LogDir, Vsns, Opts) ->
+process_agent_options(ConfDir, DbDir, LogDir, Vsns, InetBackend, Opts) ->
+    ?IPRINT("process_agent_options ->"
+            "~n   ConfDir:     ~p"
+            "~n   DbDir:       ~p"
+            "~n   LogDir:      ~p"
+            "~n   Vsns:        ~p"
+            "~n   InetBackend: ~p"
+            "~n   Opts:        ~p",
+            [ConfDir, DbDir, LogDir, Vsns, InetBackend, Opts]),
     Defaults = 
 	[{agent_type,      master},
 	 {agent_verbosity, trace},
@@ -8283,9 +8373,9 @@ process_agent_options(ConfDir, DbDir, LogDir, Vsns, Opts) ->
 	 {note_store, [{timeout,30000}, {verbosity,log}]},
 	 {net_if, [{module,    snmpa_net_if},
 		   {verbosity, trace},
-		   {options,   [{bind_to,   false},
-				{no_reuse,  false},
-				{req_limit, infinity}]}]},
+		   {options,   InetBackend ++ [{bind_to,   false},
+                                               {no_reuse,  false},
+                                               {req_limit, infinity}]}]},
 	 {audit_trail_log, [{type,   read_write},
 			    {dir,    LogDir},
 			    {size,   {10240,20}},
@@ -8699,11 +8789,12 @@ init_v1_agent(Config) ->
     %% Start nodes
     %% 
 
-    {ok, AgentNode}   = start_node(agent),
+    FName             = ?config(fname, Config),
+    {ok, AgentNode}   = start_node(mk_node_name(FName, agent)),
 
     %% We don't use a manager in this test but the (common) config 
     %% function takes an argument that is derived from this
-    {ok, ManagerNode} = start_node(manager), 
+    {ok, ManagerNode} = start_node(mk_node_name(FName, manager)), 
 
     %% -- 
     %% Mnesia init
@@ -8758,7 +8849,11 @@ init_v1_agent(Config) ->
 			   {agent_node,        AgentNode}, 
 			   {agent_host,        AgentHost}, 
 			   {agent_ip,          AgentIP}, 
-			   {agent_backup_dirs, AgentBkpDirs}|Config]),
+			   {agent_backup_dirs, AgentBkpDirs},
+                           
+                           %% We need this here since without it
+                           %% fin_v1_agent will not be able to stop!
+                           {manager_node, ManagerNode}|Config]),
 
     %% -- 
     %% Create watchdog 
@@ -8786,7 +8881,7 @@ fin_v1_agent(Config) ->
 
     %% - 
     %% Stop the agent node
-    %% 
+    %%
     stop_node(AgentNode),
 
 
diff --git a/lib/snmp/test/snmp_agent_test_lib.erl b/lib/snmp/test/snmp_agent_test_lib.erl
index c99c0359f2..236015cfe0 100644
--- a/lib/snmp/test/snmp_agent_test_lib.erl
+++ b/lib/snmp/test/snmp_agent_test_lib.erl
@@ -123,7 +123,8 @@
 init_all(Config) when is_list(Config) ->
 
     ?IPRINT("init_all -> entry with"
-            "~n   Config: ~p", [Config]),
+            "~n   Config: ~p"
+            "~n   Nodes:  ~p", [Config, nodes()]),
 
     %% --
     %% Start nodes
@@ -140,12 +141,12 @@ init_all(Config) when is_list(Config) ->
     %% Create necessary files ( and dirs ) 
     %% 
 
-    ?IPRINT("init_all -> create suite top dir"),
-    SuiteTopDir = ?config(snmp_suite_top_dir, Config),
-    ?DBG("init_all -> SuiteTopDir ~p", [SuiteTopDir]),
+    ?IPRINT("init_all -> lookup group top dir"),
+    GroupTopDir = ?config(snmp_group_top_dir, Config),
+    ?DBG("init_all -> GroupTopDir ~p", [GroupTopDir]),
 
     ?IPRINT("init_all -> create agent dir"),
-    AgentDir = join(SuiteTopDir, "agent/"), 
+    AgentDir = join(GroupTopDir, "agent/"), 
     ?line ok = file:make_dir(AgentDir),
     ?DBG("init_all -> AgentDir ~p", [AgentDir]),
 
@@ -165,12 +166,12 @@ init_all(Config) when is_list(Config) ->
     ?DBG("init_all -> AgentConfDir ~p", [AgentConfDir]),
 
     ?IPRINT("init_all -> create manager dir"),
-    MgrDir   = join(SuiteTopDir, "mgr/"), 
+    MgrDir   = join(GroupTopDir, "mgr/"), 
     ?line ok = file:make_dir(MgrDir),
     ?DBG("init_all -> MgrDir ~p", [MgrDir]),
 
     ?IPRINT("init_all -> create sub-agent dir"),
-    SaDir    = join(SuiteTopDir, "sa/"), 
+    SaDir    = join(GroupTopDir, "sa/"), 
     ?line ok = file:make_dir(SaDir),
     ?DBG("init_all -> SaDir ~p", [SaDir]),
 
@@ -213,7 +214,8 @@ init_all(Config) when is_list(Config) ->
     ?IPRINT("init_all -> get localhost"),
     Ip = ?LOCALHOST(),
 
-    ?IPRINT("init_all -> done"),
+    ?IPRINT("init_all -> done when"
+            "~n   Nodes: ~p", [nodes()]),
     [{snmp_sa,        SaNode}, 
      {snmp_mgr,       MgrNode}, 
      {snmp_master,    node()}, 
@@ -232,7 +234,8 @@ init_all(Config) when is_list(Config) ->
 finish_all(Config) when is_list(Config) ->
 
     ?IPRINT("finish_all -> entry with"
-            "~n   Config: ~p", [Config]),
+            "~n   Config: ~p"
+            "~n   Nodes:  ~p", [Config, nodes()]),
 
     SaNode  = ?config(snmp_sa, Config),
     MgrNode = ?config(snmp_mgr, Config),
@@ -246,7 +249,11 @@ finish_all(Config) when is_list(Config) ->
     ?IPRINT("finish_all -> stop mnesia application"),
     application:stop(mnesia),
 
-    ?IPRINT("finish_all -> stop"),
+    ?IPRINT("finish_all -> unload mnesia application"),
+    application:unload(mnesia),
+
+    ?IPRINT("finish_all -> stop when"
+            "~n   Nodes: ~p", [nodes()]),
     ok.
 
 
@@ -266,9 +273,18 @@ init_case(Config) when is_list(Config) ->
     SaHost         = ?HOSTNAME(SaNode),
     MgrHost        = ?HOSTNAME(MgrNode),
     MasterHost     = ?HOSTNAME(MasterNode),
-    {ok, MasterIP} = snmp_misc:ip(MasterHost, IpFamily),
-    {ok, MIP}      = snmp_misc:ip(MgrHost, IpFamily),
-    {ok, SIP}      = snmp_misc:ip(SaHost, IpFamily),
+    {ok, MasterIP} = ?LIB:which_host_ip(MasterHost, IpFamily),
+    {ok, MIP}      = ?LIB:which_host_ip(MgrHost,    IpFamily),
+    {ok, SIP}      = ?LIB:which_host_ip(SaHost,     IpFamily),
+
+    ?IPRINT("init_case -> "
+            "~n   SaHost:     ~p"
+            "~n   MgrHost:    ~p"
+            "~n   MasterHost: ~p"
+            "~n   MasterIP:   ~p"
+            "~n   MIP:        ~p"
+            "~n   SIP:        ~p",
+            [SaHost, MgrHost, MasterHost, MasterIP, MIP, SIP]),
 
     put(mgr_node,    MgrNode),
     put(sa_node,     SaNode),
@@ -296,6 +312,7 @@ init_case(Config) when is_list(Config) ->
             "~n   SaNode:     ~p"
             "~n   MgrNode:    ~p"
             "~n   MibDir:     ~p", [MasterNode, SaNode, MgrNode, MibDir]),
+
     {SaNode, MgrNode, MibDir}.
 
 
@@ -646,10 +663,11 @@ start_agent(Config, Vsns, Opts) ->
             "~n   Vsns:   ~p"
             "~n   Opts:   ~p", [node(), Config, Vsns, Opts]),
     
-    ?line AgentLogDir  = ?config(agent_log_dir,  Config),
-    ?line AgentConfDir = ?config(agent_conf_dir, Config),
-    ?line AgentDbDir   = ?config(agent_db_dir,   Config),
-    ?line SaNode       = ?config(snmp_sa,        Config),
+    ?line AgentLogDir  = ?config(agent_log_dir,      Config),
+    ?line AgentConfDir = ?config(agent_conf_dir,     Config),
+    ?line AgentDbDir   = ?config(agent_db_dir,       Config),
+    ?line SaNode       = ?config(snmp_sa,            Config),
+    ?line InetBackend  = ?config(socket_create_opts, Config),
 
     Env = app_agent_env_init(
 	    [{versions,         Vsns}, 
@@ -668,7 +686,8 @@ start_agent(Config, Vsns, Opts) ->
 	     {mib_server,       [{verbosity, log}]},
 	     {symbolic_store,   [{verbosity, log}]},
 	     {note_store,       [{verbosity, log}]},
-	     {net_if,           [{verbosity, trace}]}],
+	     {net_if,           [{verbosity, trace},
+                                 {options,   InetBackend}]}],
 	    Opts),
     
 
diff --git a/lib/snmp/test/snmp_manager_SUITE.erl b/lib/snmp/test/snmp_manager_SUITE.erl
index 1f0dd506b5..15c02942ba 100644
--- a/lib/snmp/test/snmp_manager_SUITE.erl
+++ b/lib/snmp/test/snmp_manager_SUITE.erl
@@ -143,8 +143,61 @@
 suite() -> 
     [{ct_hooks, [ts_install_cth]}].
 
-
 all() -> 
+    %% This is a temporary messure to ensure that we can 
+    %% test the socket backend without effecting *all*
+    %% applications on *all* machines.
+    %% This flag is set only for *one* host.
+    case ?TEST_INET_BACKENDS() of
+        true ->
+            [
+             {group, inet_backend_default},
+             {group, inet_backend_inet},
+             {group, inet_backend_socket}
+            ];
+        _ ->
+            [
+             {group, inet_backend_default}
+            ]
+    end.
+
+groups() -> 
+    [
+     {inet_backend_default, [], inet_backend_default_cases()},
+     {inet_backend_inet,    [], inet_backend_inet_cases()},
+     {inet_backend_socket,  [], inet_backend_socket_cases()},
+
+     {all,                  [], all_cases()},
+     {start_and_stop_tests, [], start_and_stop_tests_cases()},
+     {misc_tests,           [], misc_tests_cases()},
+     {user_tests,           [], user_tests_cases()},
+     {agent_tests,          [], agent_tests_cases()},
+     {request_tests,        [], request_tests_cases()},
+     {request_tests_mt,     [], request_tests_mt_cases()},
+     {get_tests,            [], get_tests_cases()},
+     {get_next_tests,       [], get_next_tests_cases()},
+     {set_tests,            [], set_tests_cases()},
+     {bulk_tests,           [], bulk_tests_cases()},
+     {event_tests,          [], event_tests_cases()},
+     {event_tests_mt,       [], event_tests_mt_cases()},
+     {tickets,              [], tickets_cases()},
+     {otp8015,              [], otp8015_cases()},
+     {otp8395,              [], otp8395_cases()},
+     {ipv6,                 [], ipv6_tests()},
+     {ipv6_mt,              [], ipv6_tests()}
+
+    ].
+
+inet_backend_default_cases() ->
+    [{all, [], all_cases()}].
+
+inet_backend_inet_cases() ->
+    [{all, [], all_cases()}].
+
+inet_backend_socket_cases() ->
+    [{all, [], all_cases()}].
+
+all_cases() -> 
     [
      {group, start_and_stop_tests}, 
      {group, misc_tests}, 
@@ -160,130 +213,73 @@ all() ->
      {group, ipv6_mt}
     ].
 
-groups() -> 
+start_and_stop_tests_cases() ->
+    [
+     simple_start_and_stop1, 
+     simple_start_and_stop2,
+     simple_start_and_stop3, 
+     simple_start_and_monitor_crash1,
+     simple_start_and_monitor_crash2, 
+     notify_started01,
+     notify_started02
+    ].
+
+misc_tests_cases() ->
+    [
+     info,
+     usm_priv_aes
+    ].
+
+user_tests_cases() ->
+    [
+     register_user1
+    ].
+
+agent_tests_cases() ->
+    [
+     register_agent_old,
+     register_agent2, 
+     register_agent3
+    ].
+    
+request_tests_cases() ->
     [
-     {start_and_stop_tests, [],
-      [
-       simple_start_and_stop1, 
-       simple_start_and_stop2,
-       simple_start_and_stop3, 
-       simple_start_and_monitor_crash1,
-       simple_start_and_monitor_crash2, 
-       notify_started01,
-       notify_started02
-      ]
-     },
-     {misc_tests, [], 
-      [
-       info,
-       usm_priv_aes
-      ]
-     },
-     {user_tests, [], 
-      [
-       register_user1
-      ]
-     },
-     {agent_tests, [], 
-      [
-       register_agent_old,
-       register_agent2, 
-       register_agent3
-      ]
-     },
-     {request_tests, [],
-      [
-       {group, get_tests}, 
-       {group, get_next_tests}, 
-       {group, set_tests}, 
-       {group, bulk_tests}
-      ]
-     },
-     {request_tests_mt, [],
-      [
-       {group, get_tests}, 
-       {group, get_next_tests},
-       {group, set_tests}, 
-       {group, bulk_tests}
-      ]
-     },
-     {get_tests, [],
-      [
-       simple_sync_get3, 
-       simple_async_get3
-      ]
-     },
-     {get_next_tests, [],
-      [
-       simple_sync_get_next3,
-       simple_async_get_next3_cbp_def,
-       simple_async_get_next3_cbp_temp,
-       simple_async_get_next3_cbp_perm
-      ]
-     },
-     {set_tests, [],
-      [
-       simple_sync_set3, 
-       simple_async_set3_cbp_def,
-       simple_async_set3_cbp_temp,
-       simple_async_set3_cbp_perm
-      ]
-     },
-     {bulk_tests, [],
-      [
-       simple_sync_get_bulk3,
-       simple_async_get_bulk3_cbp_def,
-       simple_async_get_bulk3_cbp_temp,
-       simple_async_get_bulk3_cbp_perm
-      ]
-     },
-     {event_tests, [],
-      [
-       trap1, 
-       trap2, 
-       inform1, 
-       inform2, 
-       inform3, 
-       inform4,
-       inform_swarm_cbp_def,
-       inform_swarm_cbp_temp,
-       inform_swarm_cbp_perm,
-       report
-      ]
-     },
-     {event_tests_mt, [],
-      [
-       trap1, 
-       trap2, 
-       inform1, 
-       inform2, 
-       inform3, 
-       inform4,
-       inform_swarm_cbp_def,
-       inform_swarm_cbp_temp,
-       inform_swarm_cbp_perm,
-       report
-      ]
-     },
-     {tickets, [], 
-      [
-       {group, otp8015}, 
-       {group, otp8395}
-      ]
-     },
-     {otp8015, [], 
-      [
-       otp8015_1
-      ]
-     }, 
-     {otp8395, [], 
-      [
-       otp8395_1
-      ]
-     },
-     {ipv6, [], ipv6_tests()},
-     {ipv6_mt, [], ipv6_tests()}
+     {group, get_tests}, 
+     {group, get_next_tests}, 
+     {group, set_tests}, 
+     {group, bulk_tests}
+    ].
 
+request_tests_mt_cases() -> request_tests_cases().
+
+get_tests_cases() ->
+    [
+     simple_sync_get3, 
+     simple_async_get3
+    ].
+
+get_next_tests_cases() ->
+    [
+     simple_sync_get_next3,
+     simple_async_get_next3_cbp_def,
+     simple_async_get_next3_cbp_temp,
+     simple_async_get_next3_cbp_perm
+    ].
+
+set_tests_cases() ->
+    [
+     simple_sync_set3, 
+     simple_async_set3_cbp_def,
+     simple_async_set3_cbp_temp,
+     simple_async_set3_cbp_perm
+    ].
+
+bulk_tests_cases() ->
+    [
+     simple_sync_get_bulk3,
+     simple_async_get_bulk3_cbp_def,
+     simple_async_get_bulk3_cbp_temp,
+     simple_async_get_bulk3_cbp_perm
     ].
 
 ipv6_tests() ->
@@ -301,7 +297,37 @@ ipv6_tests() ->
      inform_swarm_cbp_perm
     ].
 
+event_tests_cases() ->
+    [
+     trap1, 
+     trap2, 
+     inform1, 
+     inform2, 
+     inform3, 
+     inform4,
+     inform_swarm_cbp_def,
+     inform_swarm_cbp_temp,
+     inform_swarm_cbp_perm,
+     report
+    ].
+
+event_tests_mt_cases() -> event_tests_cases().
+
+tickets_cases() ->
+    [
+     {group, otp8015}, 
+     {group, otp8395}
+    ].
+
+otp8015_cases() ->
+    [
+     otp8015_1
+    ].
 
+otp8395_cases() ->
+    [
+     otp8395_1
+    ].
 
 %%
 %% -----
@@ -310,7 +336,13 @@ ipv6_tests() ->
 init_per_suite(Config0) when is_list(Config0) ->
 
     ?IPRINT("init_per_suite -> entry with"
-            "~n      Config0: ~p", [Config0]),
+            "~n      Config0: ~p"
+            "~n      Nodes:  ~p"
+            "~n      explicit inet backend: ~p"
+            "~n      test inet backends:    ~p",
+            [Config0, erlang:nodes(),
+             ?EXPLICIT_INET_BACKEND(),
+             ?TEST_INET_BACKENDS()]),
 
     case ?LIB:init_per_suite(Config0) of
         {skip, _} = SKIP ->
@@ -363,20 +395,61 @@ end_per_suite(Config0) when is_list(Config0) ->
 %% -----
 %%
 
-init_per_group(request_tests_mt = GroupName, Config) ->
+init_per_group(GroupName, Config0) ->
+    ?IPRINT("init_per_group -> entry with"
+            "~n      GroupName: ~p"
+            "~n      Config:    ~p"
+            "~n   when"
+            "~n      Nodes:     ~p",
+            [GroupName, Config0, nodes()]),
+
+    Config1 = init_per_group2(GroupName, Config0),
+
+    ?IPRINT("init_per_group -> done when"
+            "~n      GroupName: ~p"
+            "~n      Config:    ~p"
+            "~n      Nodes:     ~p",
+            [GroupName, Config1, nodes()]),
+
+    Config1.
+
+
+init_per_group2(inet_backend_default = _GroupName, Config) ->
+    ?LIB:init_group_top_dir(default, [{socket_create_opts, []} | Config]);
+init_per_group2(inet_backend_inet = _GroupName, Config) ->
+    case ?EXPLICIT_INET_BACKEND() of
+        true ->
+            %% The environment trumps us,
+            %% so only the default group should be run!
+            {skip, "explicit inet backend"};
+        false ->
+            ?LIB:init_group_top_dir(inet, [{socket_create_opts, [{inet_backend, inet}]} | Config])
+    end;
+init_per_group2(inet_backend_socket = _GroupName, Config) ->
+    case ?EXPLICIT_INET_BACKEND() of
+        true ->
+            %% The environment trumps us,
+            %% so only the default group should be run!
+            {skip, "explicit inet backend"};
+        false ->
+            ?LIB:init_group_top_dir(socket, [{socket_create_opts, [{inet_backend, socket}]} | Config])
+    end;
+init_per_group2(all = GroupName, Config) ->
+    ?LIB:init_group_top_dir(GroupName, Config);
+init_per_group2(request_tests_mt = GroupName, Config) ->
     ?LIB:init_group_top_dir(
       GroupName, 
       [{manager_net_if_module, snmpm_net_if_mt} | Config]);
-init_per_group(event_tests_mt = GroupName, Config) ->
+init_per_group2(event_tests_mt = GroupName, Config) ->
     ?LIB:init_group_top_dir(
       GroupName, 
       [{manager_net_if_module, snmpm_net_if_mt} | Config]);
-init_per_group(ipv6_mt = GroupName, Config) ->
+init_per_group2(ipv6_mt = GroupName, Config) ->
     init_per_group_ipv6(GroupName,
                         [{manager_net_if_module, snmpm_net_if_mt} | Config]);   
-init_per_group(ipv6 = GroupName, Config) -> 
+init_per_group2(ipv6 = GroupName, Config) -> 
     init_per_group_ipv6(GroupName, Config);   
-init_per_group(GroupName, Config) ->
+init_per_group2(GroupName, Config) ->
     ?LIB:init_group_top_dir(GroupName, Config).
 
 
@@ -728,15 +801,16 @@ simple_start_and_stop1(Config) when is_list(Config) ->
 do_simple_start_and_stop1(Config) ->
     ?IPRINT("starting with Config: "
             "~n      ~p", [Config]),
-    ConfDir = ?config(manager_conf_dir, Config),
-    DbDir   = ?config(manager_db_dir, Config),
+    SCO     = ?config(socket_create_opts, Config),
+    ConfDir = ?config(manager_conf_dir,   Config),
+    DbDir   = ?config(manager_db_dir,     Config),
 
     write_manager_conf(ConfDir),
 
-    Opts = [{server, [{verbosity, trace}]},
-	    {net_if, [{verbosity, trace}]},
+    Opts = [{server,     [{verbosity, trace}]},
+	    {net_if,     [{verbosity, trace}, {options, SCO}]},
 	    {note_store, [{verbosity, trace}]},
-	    {config, [{verbosity, trace}, {dir, ConfDir}, {db_dir, DbDir}]}],
+	    {config,     [{verbosity, trace}, {dir, ConfDir}, {db_dir, DbDir}]}],
 
     ?IPRINT("try starting manager"),
     ok = snmpm:start_link(Opts),
@@ -768,15 +842,16 @@ do_simple_start_and_stop2([ManagerNode], Config) ->
             "~n      ~p"
             "~n", [Config]),
 
-    ConfDir = ?config(manager_conf_dir, Config),
-    DbDir   = ?config(manager_db_dir, Config),
+    SCO     = ?config(socket_create_opts, Config),
+    ConfDir = ?config(manager_conf_dir,   Config),
+    DbDir   = ?config(manager_db_dir,     Config),
 
     write_manager_conf(ConfDir),
 
-    Opts = [{server, [{verbosity, trace}]},
-	    {net_if, [{verbosity, trace}]},
+    Opts = [{server,     [{verbosity, trace}]},
+	    {net_if,     [{verbosity, trace}, {options, SCO}]},
 	    {note_store, [{verbosity, trace}]},
-	    {config, [{verbosity, trace}, {dir, ConfDir}, {db_dir, DbDir}]}],
+	    {config,     [{verbosity, trace}, {dir, ConfDir}, {db_dir, DbDir}]}],
 
 
     ?IPRINT("try load snmp application"),
@@ -812,13 +887,15 @@ do_simple_start_and_stop3(Config) ->
     ?IPRINT("starting with Config: "
             "~n      ~p", [Config]),
 
+    SCO     = ?config(socket_create_opts, Config),
     ConfDir = ?config(manager_conf_dir, Config),
     DbDir   = ?config(manager_db_dir, Config),
 
     write_manager_conf(ConfDir),
 
     Opts = [{server,     [{verbosity, trace}]},
-	    {net_if,     [{verbosity, trace}, {options, [{extra_sock_opts, ['this-should-not-work']}]}]},
+	    {net_if,     [{verbosity, trace},
+                          {options,   SCO ++ [{extra_sock_opts, ['this-should-not-work']}]}]},
 	    {note_store, [{verbosity, trace}]},
 	    {config,     [{verbosity, trace}, {dir, ConfDir}, {db_dir, DbDir}]}],
 
@@ -850,15 +927,16 @@ do_simple_start_and_monitor_crash1(Config) ->
     ?IPRINT("starting with Config: "
             "~n      ~p", [Config]),
 
-    ConfDir = ?config(manager_conf_dir, Config),
-    DbDir   = ?config(manager_db_dir, Config),
+    SCO     = ?config(socket_create_opts, Config),
+    ConfDir = ?config(manager_conf_dir,   Config),
+    DbDir   = ?config(manager_db_dir,     Config),
 
     write_manager_conf(ConfDir),
 
-    Opts = [{server, [{verbosity, trace}]},
-	    {net_if, [{verbosity, trace}]},
+    Opts = [{server,     [{verbosity, trace}]},
+	    {net_if,     [{verbosity, trace}, {options, SCO}]},
 	    {note_store, [{verbosity, trace}]},
-	    {config, [{verbosity, trace}, {dir, ConfDir}, {db_dir, DbDir}]}],
+	    {config,     [{verbosity, trace}, {dir, ConfDir}, {db_dir, DbDir}]}],
 
     ?IPRINT("try starting manager"),
     ok = snmpm:start(Opts),
@@ -923,16 +1001,17 @@ do_simple_start_and_monitor_crash2(Config) ->
     ?IPRINT("starting with Config: "
             "~n      ~p", [Config]),
 
-    ConfDir = ?config(manager_conf_dir, Config),
-    DbDir   = ?config(manager_db_dir, Config),
+    SCO     = ?config(socket_create_opts, Config),
+    ConfDir = ?config(manager_conf_dir,   Config),
+    DbDir   = ?config(manager_db_dir,     Config),
 
     write_manager_conf(ConfDir),
 
     Opts = [{restart_type, permanent},
-	    {server, [{verbosity, trace}]},
-	    {net_if, [{verbosity, trace}]},
+	    {server,     [{verbosity, trace}]},
+	    {net_if,     [{verbosity, trace}, {options, SCO}]},
 	    {note_store, [{verbosity, trace}]},
-	    {config, [{verbosity, trace}, {dir, ConfDir}, {db_dir, DbDir}]}],
+	    {config,     [{verbosity, trace}, {dir, ConfDir}, {db_dir, DbDir}]}],
 
     ?IPRINT("try starting manager"),
     ok = snmpm:start(Opts),
@@ -1018,15 +1097,16 @@ do_notify_started01(Config) ->
     ?IPRINT("starting with Config: "
             "~n      ~p", [Config]),
 
-    ConfDir = ?config(manager_conf_dir, Config),
-    DbDir   = ?config(manager_db_dir, Config),
+    SCO     = ?config(socket_create_opts, Config),
+    ConfDir = ?config(manager_conf_dir,   Config),
+    DbDir   = ?config(manager_db_dir,     Config),
 
     write_manager_conf(ConfDir),
 
-    Opts = [{server, [{verbosity, log}]},
-	    {net_if, [{verbosity, silence}]},
+    Opts = [{server,     [{verbosity, log}]},
+	    {net_if,     [{verbosity, silence}, {options, SCO}]},
 	    {note_store, [{verbosity, silence}]},
-	    {config, [{verbosity, log}, {dir, ConfDir}, {db_dir, DbDir}]}],
+	    {config,     [{verbosity, log}, {dir, ConfDir}, {db_dir, DbDir}]}],
 
     ?IPRINT("request start notification (1)"),
     Pid1 = snmpm:notify_started(10000),
@@ -1128,13 +1208,14 @@ do_notify_started02(Config) ->
     ?IPRINT("starting with Config: "
             "~n      ~p", [Config]),
 
-    ConfDir = ?config(manager_conf_dir, Config),
-    DbDir   = ?config(manager_db_dir, Config),
+    SCO     = ?config(socket_create_opts, Config),
+    ConfDir = ?config(manager_conf_dir,   Config),
+    DbDir   = ?config(manager_db_dir,     Config),
 
     write_manager_conf(ConfDir),
 
     Opts = [{server,     [{verbosity, log}]},
-	    {net_if,     [{verbosity, silence}]},
+	    {net_if,     [{verbosity, silence}, {options, SCO}]},
 	    {note_store, [{verbosity, silence}]},
 	    {config,     [{verbosity, debug}, {dir, ConfDir}, {db_dir, DbDir}]}],
 
@@ -1328,17 +1409,18 @@ ns02_ctrl_loop(Opts, N) ->
 info(suite) -> [];
 info(Config) when is_list(Config) ->
     Pre = fun() ->
-                  ConfDir = ?config(manager_conf_dir, Config),
-                  DbDir   = ?config(manager_db_dir, Config),
+                  SCO     = ?config(socket_create_opts, Config),
+                  ConfDir = ?config(manager_conf_dir,   Config),
+                  DbDir   = ?config(manager_db_dir,     Config),
 
                   write_manager_conf(ConfDir),
 
-                  Opts = [{server, [{verbosity, trace}]},
-                          {net_if, [{verbosity, trace}]},
+                  Opts = [{server,     [{verbosity, trace}]},
+                          {net_if,     [{verbosity, trace}, {options, SCO}]},
                           {note_store, [{verbosity, trace}]},
-                          {config, [{verbosity, trace}, 
-                                    {dir,       ConfDir}, 
-                                    {db_dir,    DbDir}]}],
+                          {config,    [{verbosity, trace}, 
+                                       {dir,       ConfDir}, 
+                                       {db_dir,    DbDir}]}],
                   ?IPRINT("try starting manager"),
                   ok = snmpm:start(Opts),
                   ?SLEEP(1000),
@@ -1370,32 +1452,54 @@ do_info(Config) ->
 verify_info(Info) when is_list(Info) ->
     Keys = [{server,     [process_memory, db_memory]},
 	    {config,     [process_memory, db_memory]},
-	    {net_if,     [process_memory, port_info]},
+	    {net_if,     [process_memory, transport_info]},
 	    {note_store, [process_memory, db_memory]},
 	    stats_counters],
-    verify_info(Keys, Info);
+    try verify_info(Keys, Info)
+    catch
+        C:E:S ->
+            ?IPRINT("Verification Failed: "
+                    "~n      Class: ~p"
+                    "~n      Error: ~p"
+                    "~n      Stack: ~p", [C, E, S]),
+            {error, {verification_failed, C, E, S}}
+    end;
 verify_info(BadInfo) ->
     {error, {bad_info, BadInfo}}.
 
 verify_info([], _) ->
+    ?IPRINT("verified"),
     ok;
 verify_info([Key|Keys], Info) when is_atom(Key) ->
+    ?IPRINT("try verify '~p'", [Key]),
     case lists:keymember(Key, 1, Info) of
 	true ->
 	    verify_info(Keys, Info);
 	false ->
+            ?IPRINT("Verification of '~p' failed", [Key]),
 	    {error, {missing_info, {Key, Info}}}
     end;
 verify_info([{Key, SubKeys}|Keys], Info) ->
+    ?IPRINT("try verify '~p' with sub-keys: "
+            "~n      ~p", [Key, SubKeys]),    
     case lists:keysearch(Key, 1, Info) of
 	{value, {Key, SubInfo}} ->
-	    case verify_info(SubKeys, SubInfo) of
+            SubInfo2 =
+                if is_list(SubInfo) -> SubInfo;
+                   is_map(SubInfo)  -> maps:to_list(SubInfo)
+                end,
+            ?IPRINT("try verify sub-key(s) with sub-info: "
+                    "~n      (Sub-) Keys: ~p"
+                    "~n      (Sub-) Info: ~p", [SubKeys, SubInfo2]),
+	    case verify_info(SubKeys, SubInfo2) of
 		ok ->
 		    verify_info(Keys, Info);
 		{error, {missing_info, {SubKey, _}}} ->
+                    ?IPRINT("Verification of sub-key '~p' failed", [SubKey]),
 		    {error, {missing_subinfo, {Key, SubKey, Info}}}
 	    end;
 	false ->
+            ?IPRINT("Verification of key '~p' failed", [Key]),
 	    {error, {missing_info, {Key, Info}}}
     end.
 
@@ -1408,13 +1512,14 @@ verify_info([{Key, SubKeys}|Keys], Info) ->
 usm_priv_aes(suite) -> [];
 usm_priv_aes(Config) when is_list(Config) ->
     Pre = fun() ->
-                  ConfDir = ?config(manager_conf_dir, Config),
-                  DbDir   = ?config(manager_db_dir, Config),
+                  SCO     = ?config(socket_create_opts, Config),
+                  ConfDir = ?config(manager_conf_dir,   Config),
+                  DbDir   = ?config(manager_db_dir,     Config),
 
                   write_manager_conf(ConfDir),
 
                   Opts = [{server,     [{verbosity, trace}]},
-                          {net_if,     [{verbosity, trace}]},
+                          {net_if,     [{verbosity, trace}, {options, SCO}]},
                           {note_store, [{verbosity, trace}]},
                           {config,     [{verbosity, trace},
                                         {dir,       ConfDir},
@@ -1505,11 +1610,11 @@ do_usm_priv_aes(Config) ->
     ?IPRINT("encode scoped pdu"),
     Message =
       { message,
-        _Version = 'version-3',
+        'version-3',
         { v3_hdr,
-          _MsgID = 1,
+          1, % MsgID1 
           MsgMaxSize,
-          _MsgFlags = snmp_misc:mk_msg_flags(PduType, 2),
+          snmp_misc:mk_msg_flags(PduType, 2), % MsgFlags1
           _MsgSecurityModel = 3,  % SEC_USM
           MsgSecurityParameters,
           0
@@ -1587,13 +1692,14 @@ do_register_user1([ManagerNode], Config) ->
             "~n   ~p"
             "~n", [Config]),
 
-    ConfDir = ?config(manager_conf_dir, Config),
-    DbDir   = ?config(manager_db_dir, Config),
+    SCO     = ?config(socket_create_opts, Config),
+    ConfDir = ?config(manager_conf_dir,   Config),
+    DbDir   = ?config(manager_db_dir,     Config),
 
     write_manager_conf(ConfDir),
 
     Opts = [{server,     [{verbosity, trace}]},
-	    {net_if,     [{verbosity, trace}]},
+	    {net_if,     [{verbosity, trace}, {options, SCO}]},
 	    {note_store, [{verbosity, trace}]},
 	    {config, [{verbosity, trace}, {dir, ConfDir}, {db_dir, DbDir}]}],
 
@@ -1687,13 +1793,14 @@ do_register_agent_old([ManagerNode], Config) ->
             "~n      ~p"
             "~n", [Config]),
 
-    ConfDir = ?config(manager_conf_dir, Config),
-    DbDir   = ?config(manager_db_dir, Config),
+    SCO     = ?config(socket_create_opts, Config),
+    ConfDir = ?config(manager_conf_dir,   Config),
+    DbDir   = ?config(manager_db_dir,     Config),
 
     write_manager_conf(ConfDir),
 
     Opts = [{server,     [{verbosity, trace}]},
-	    {net_if,     [{verbosity, trace}]},
+	    {net_if,     [{verbosity, trace}, {options, SCO}]},
 	    {note_store, [{verbosity, trace}]},
 	    {config, [{verbosity, trace}, {dir, ConfDir}, {db_dir, DbDir}]}],
 
@@ -1820,14 +1927,15 @@ do_register_agent2([ManagerNode], Config) ->
     ?IPRINT("starting with Config: "
             "~n      ~p", [Config]),
 
-    ConfDir   = ?config(manager_conf_dir, Config),
-    DbDir     = ?config(manager_db_dir, Config),
+    SCO       = ?config(socket_create_opts, Config),
+    ConfDir   = ?config(manager_conf_dir,   Config),
+    DbDir     = ?config(manager_db_dir,     Config),
     LocalHost = snmp_test_lib:localhost(), 
 
     write_manager_conf(ConfDir),
 
     Opts = [{server,     [{verbosity, trace}]},
-	    {net_if,     [{verbosity, trace}]},
+	    {net_if,     [{verbosity, trace}, {options, SCO}]},
 	    {note_store, [{verbosity, trace}]},
 	    {config, [{verbosity, trace}, {dir, ConfDir}, {db_dir, DbDir}]}],
 
@@ -1965,15 +2073,16 @@ do_register_agent3([ManagerNode], Config) ->
     ?IPRINT("starting with Config: "
             "~n      ~p", [Config]),
 
-    ConfDir   = ?config(manager_conf_dir, Config),
-    DbDir     = ?config(manager_db_dir, Config),
+    SCO       = ?config(socket_create_opts, Config),
+    ConfDir   = ?config(manager_conf_dir,   Config),
+    DbDir     = ?config(manager_db_dir,     Config),
     LocalHost = snmp_test_lib:localhost(), 
 
 
     write_manager_conf(ConfDir),
 
     Opts = [{server,     [{verbosity, trace}]},
-	    {net_if,     [{verbosity, trace}]},
+	    {net_if,     [{verbosity, trace}, {options, SCO}]},
 	    {note_store, [{verbosity, trace}]},
 	    {config, [{verbosity, trace}, {dir, ConfDir}, {db_dir, DbDir}]}],
 
@@ -4490,13 +4599,14 @@ otp8015_1(doc) -> ["OTP-8015:1 - testing the new api-function."];
 otp8015_1(suite) -> [];
 otp8015_1(Config) when is_list(Config) ->
     Pre = fun() ->
-                  ConfDir = ?config(manager_conf_dir, Config),
-                  DbDir   = ?config(manager_db_dir, Config),
+                  SCO     = ?config(socket_create_opts, Config),
+                  ConfDir = ?config(manager_conf_dir,   Config),
+                  DbDir   = ?config(manager_db_dir,     Config),
 
                   write_manager_conf(ConfDir),
 
                   Opts = [{server,     [{verbosity, trace}]},
-                          {net_if,     [{verbosity, trace}]},
+                          {net_if,     [{verbosity, trace}, {options, SCO}]},
                           {note_store, [{verbosity, trace}]},
                           {config,     [{verbosity, trace},
                                         {dir,       ConfDir},
@@ -5349,10 +5459,12 @@ start_manager(Node, Vsns, Conf0, _Opts) ->
             "~n   Conf0:  ~p"
             "~n   Opts:   ~p", [Node, Vsns, Conf0, _Opts]),
 
-    AtlDir  = ?config(manager_log_dir,  Conf0),
-    ConfDir = ?config(manager_conf_dir, Conf0),
-    DbDir   = ?config(manager_db_dir,   Conf0),
-    IRB     = ?config(irb,              Conf0),
+    SCO     = ?config(socket_create_opts, Conf0),
+
+    AtlDir  = ?config(manager_log_dir,    Conf0),
+    ConfDir = ?config(manager_conf_dir,   Conf0),
+    DbDir   = ?config(manager_db_dir,     Conf0),
+    IRB     = ?config(irb,                Conf0),
 
     ConfigVerbosity    = get_opt(manager_config_verbosity,     Conf0, trace),
     NoteStoreVerbosity = get_opt(manager_note_store_verbosity, Conf0, log),
@@ -5367,27 +5479,29 @@ start_manager(Node, Vsns, Conf0, _Opts) ->
     NetIfConf = 
 	case get_opt(manager_net_if_module, Conf0, no_module) of
 	    no_module ->
-		[{verbosity, NetIfVerbosity}];
+		[{verbosity, NetIfVerbosity},
+                 {options,   SCO}];
 	    NetIfModule ->
 		[{module,    NetIfModule}, 
-		 {verbosity, NetIfVerbosity}]
+		 {verbosity, NetIfVerbosity},
+                 {options,   SCO}]
 	end,
 
-    Env = [{versions,                     Vsns},
-	   {inform_request_behaviour,     IRB},
-	   {audit_trail_log, [{type,      read_write},
-			      {dir,       AtlDir},
-			      {size,      {10240, 10}},
-			      {repair,    true},
-			      {seqno,     AtlSeqNo}]},
-	   {config,          [{dir,       ConfDir}, 
-			      {db_dir,    DbDir}, 
-			      {verbosity, ConfigVerbosity}]},
-	   {note_store,      [{verbosity, NoteStoreVerbosity}]},
-	   {server,          [{verbosity, ServerVerbosity},
-                              {cbproxy,   CBP},
-                              {netif_sup, NIS}]},
-	   {net_if,          NetIfConf}],
+    Env = [{versions,                 Vsns},
+	   {inform_request_behaviour, IRB},
+	   {audit_trail_log,          [{type,      read_write},
+                                       {dir,       AtlDir},
+                                       {size,      {10240, 10}},
+                                       {repair,    true},
+                                       {seqno,     AtlSeqNo}]},
+	   {config,                   [{dir,       ConfDir}, 
+                                       {db_dir,    DbDir}, 
+                                       {verbosity, ConfigVerbosity}]},
+	   {note_store,               [{verbosity, NoteStoreVerbosity}]},
+	   {server,                   [{verbosity, ServerVerbosity},
+                                       {cbproxy,   CBP},
+                                       {netif_sup, NIS}]},
+	   {net_if,                   NetIfConf}],
     ?line ok = set_mgr_env(Node, Env),
 
     ?line ok = try start_snmp(Node) of
diff --git a/lib/snmp/test/snmp_test_global_sys_monitor.erl b/lib/snmp/test/snmp_test_global_sys_monitor.erl
index c3f2e24096..c77b118d18 100644
--- a/lib/snmp/test/snmp_test_global_sys_monitor.erl
+++ b/lib/snmp/test/snmp_test_global_sys_monitor.erl
@@ -240,13 +240,13 @@ call(Req, Timeout1, Timeout2) ->
                     NamePid when is_pid(NamePid) ->
                         receive
                             {?MODULE, Ref, Rep} ->
-                                Rep
+                                exit(Rep)
                         after Timeout2 ->
-                                {error, timeout}
+                                exit({error, timeout})
                         end
                 catch
                     C:E:_ ->
-                        {error, {catched, C, E}}
+                        exit({error, {catched, C, E}})
                 end
         end,
     {Pid, Mon} = spawn_monitor(F),
diff --git a/lib/snmp/test/snmp_test_lib.erl b/lib/snmp/test/snmp_test_lib.erl
index c2c720fdb4..bbf53f8f3e 100644
--- a/lib/snmp/test/snmp_test_lib.erl
+++ b/lib/snmp/test/snmp_test_lib.erl
@@ -51,6 +51,8 @@
 -export([f/2, formated_timestamp/0]).
 -export([p/2, print1/2, print2/2, print/5]).
 -export([eprint/2, wprint/2, nprint/2, iprint/2]).
+-export([explicit_inet_backend/0, test_inet_backends/0]).
+-export([which_host_ip/2]).
 
 
 -define(SKIP(R), skip(R, ?MODULE, ?LINE)).
@@ -258,6 +260,45 @@ tc_which_name() ->
 %% Misc functions
 %%
 
+explicit_inet_backend() ->
+    %% This is intentional!
+    %% This is a kernel flag, which if set disables
+    %% our own special handling of the inet_backend
+    %% in our test suites.
+    case application:get_all_env(kernel) of
+        Env when is_list(Env) ->
+            case lists:keysearch(inet_backend, 1, Env) of
+                {value, {inet_backend, _}} ->
+                    true;
+                _ ->
+                    false
+            end;
+        _ ->
+            false
+    end.
+
+test_inet_backends() ->
+    case init:get_argument(snmp) of
+        {ok, SnmpArgs} when is_list(SnmpArgs) ->
+            test_inet_backends(SnmpArgs, atom_to_list(?FUNCTION_NAME));
+        error ->
+            false
+    end.
+
+test_inet_backends([], _) ->
+    false;
+test_inet_backends([[Key, Val] | _], Key) ->
+    case list_to_atom(string:to_lower(Val)) of
+        Bool when is_boolean(Bool) ->
+            Bool;
+        _ ->
+            false
+    end;
+test_inet_backends([_|Args], Key) ->
+    test_inet_backends(Args, Key).
+
+
+
 proxy_call(F, Timeout, Default)
   when is_function(F, 0) andalso is_integer(Timeout) andalso (Timeout > 0) ->
     {P, M} = erlang:spawn_monitor(fun() -> exit(F()) end),
@@ -282,6 +323,29 @@ hostname(Node) ->
             []
     end.
 
+
+which_host_ip(Hostname, Family) ->
+    case snmp_misc:ip(Hostname, Family) of
+        {ok, {A, _, _, _}} = OK
+          when (A =/= 127) ->
+            OK;
+        {ok, {A, _, _, _, _, _, _, _}} = OK 
+          when (A =/= 0) andalso 
+               (A =/= 16#fe80) ->
+            OK;
+        {ok, _} ->
+            try localhost(Family) of
+                Addr ->
+                    {ok, Addr}
+            catch
+                C:E:S ->
+                    {error, {C, E, S}}
+            end;
+        {error, _} = ERROR ->
+            ERROR
+    end.
+
+
 localhost() ->
     localhost(inet).
 
@@ -315,6 +379,8 @@ which_addr(_Family, []) ->
     fail(no_valid_addr, ?MODULE, ?LINE);
 which_addr(Family, [{"lo", _} | IfList]) ->
     which_addr(Family, IfList);
+which_addr(Family, [{"tun" ++ _, _} | IfList]) ->
+    which_addr(Family, IfList);
 which_addr(Family, [{"docker" ++ _, _} | IfList]) ->
     which_addr(Family, IfList);
 which_addr(Family, [{"br-" ++ _, _} | IfList]) ->
@@ -624,6 +690,17 @@ old_is_ipv6_host(Hostname) ->
 
 init_per_suite(Config) ->
 
+    iprint("snmp environment: "
+           "~n   (snmp) app:  ~p"
+           "~n   (all)  init: ~p"
+           "~n   (snmp) init: ~p",
+           [application:get_all_env(snmp),
+            init:get_arguments(),
+            case init:get_argument(snmp) of
+                {ok, Args} -> Args;
+                error -> undefined
+            end]),
+
     ct:timetrap(minutes(2)),
 
     try analyze_and_print_host_info() of
@@ -781,6 +858,7 @@ init_group_top_dir(GroupName, Config) ->
 	    [{snmp_group_top_dir, GroupTopDir} | Config];
 
 	_ ->
+            %% This is a "top level" group, that is, there is only the suite
 	    case lists:keysearch(snmp_suite_top_dir, 1, Config) of
 		{value, {_Key, Dir}} ->
 		    GroupTopDir = filename:join(Dir, GroupName),
diff --git a/lib/snmp/test/snmp_test_lib.hrl b/lib/snmp/test/snmp_test_lib.hrl
index 78d1453c12..a6b1be76ea 100644
--- a/lib/snmp/test/snmp_test_lib.hrl
+++ b/lib/snmp/test/snmp_test_lib.hrl
@@ -41,6 +41,9 @@
 -define(OSTYPE(),                 ?LIB:os_type()).
 -define(DISPLAY_SUITE_INFO(),     ?LIB:display_suite_info(?MODULE)).
 
+-define(EXPLICIT_INET_BACKEND(),  ?LIB:explicit_inet_backend()).
+-define(TEST_INET_BACKENDS(),     ?LIB:test_inet_backends()).
+
 
 %% - Test case macros - 
 
diff --git a/lib/snmp/test/snmp_test_mgr.erl b/lib/snmp/test/snmp_test_mgr.erl
index fe2852c573..7fab69c043 100644
--- a/lib/snmp/test/snmp_test_mgr.erl
+++ b/lib/snmp/test/snmp_test_mgr.erl
@@ -262,7 +262,7 @@ init({Options, CallerPid}) ->
 			   Addr;
 		       {value, Host} when is_list(Host) ->
                            ?IPRINT("init -> Host: ~p", [Host]),
-			   {ok, Ip} = snmp_misc:ip(Host, IpFamily),
+			   {ok, Ip} = ?LIB:which_host_ip(Host, IpFamily),
 			   Ip
 		   end,
 	    ?IPRINT("init -> AgIp: ~p", [AgIp]),