From 06ae2f45ec6e82dfdae7ebca26cfaa039859b79b Mon Sep 17 00:00:00 2001
From: Ulf Wiger <ulf@feuerlabs.com>
Date: Thu, 3 Mar 2016 16:54:48 -0800
Subject: w.i.p. netlink monitor

---
 components/rvi_common/src/rvi_netlink.erl | 113 ++++++++++++++++++++++++++++--
 1 file changed, 107 insertions(+), 6 deletions(-)

(limited to 'components')

diff --git a/components/rvi_common/src/rvi_netlink.erl b/components/rvi_common/src/rvi_netlink.erl
index 2d03a23..5a81ecb 100644
--- a/components/rvi_common/src/rvi_netlink.erl
+++ b/components/rvi_common/src/rvi_netlink.erl
@@ -10,7 +10,7 @@
 -behaviour(gen_server).
 
 -export([is_network_up/0,
-         subscribe/0]).
+         subscribe/0, subscribe/1, subscribe/2]).
 
 -export([start_link/0]).
 
@@ -22,8 +22,16 @@
          terminate/2,
          code_change/3]).
 
+-record(iface, {name,
+                status = down,
+                opts = []}).
+
+-record(sub, {name, field, pid, ref}).
+
 -record(st, {connected = false,
-             subscribers = []}).
+             ifs = [],
+             subscribers = [],
+             poll_ref}).
 
 -define(BADARG, {?MODULE, '__BADARG__'}).
 
@@ -31,25 +39,62 @@ is_network_up() ->
     call(is_network_up).
 
 subscribe() ->
-    call(subscribe).
+    subscribe(all, operstate).
+
+subscribe(Iface) ->
+    subscribe(Iface, operstate).
+
+subscribe(Iface, Field) ->
+    call({subscribe, Iface, Field}).
 
 start_link() ->
     gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
 
 init(_) ->
-    {ok, #st{}}.
+    Ref = case code:is_loaded(netlink_drv) of
+              false ->
+                  %% Must fake event mechanism through polling
+                  start_poll_timer();
+              {file, _} ->
+                  netlink:subscribe("", [operstate], [flush]),
+                  undefined
+          end,
+    Interfaces = get_interfaces(),
+    {ok, #st{ifs = Interfaces,
+             poll_ref = Ref}}.
 
 handle_call(is_network_up, _From, #st{connected = Conn} = St) ->
     {reply, Conn, St};
-handle_call(subscribe, {Pid, _}, #st{subscribers = Subs} = St) ->
+handle_call({subscribe, Iface, Field}, {Pid, _},
+            #st{subscribers = Subs} = St) ->
     Ref = erlang:monitor(process, Pid),
-    {reply, ok, St#st{subscribers = [{Pid, Ref}|Subs]}};
+    {reply, ok, St#st{subscribers = [#sub{name = Iface,
+                                          field = Field,
+                                          pid = Pid,
+                                          ref = Ref}|Subs]}};
 handle_call(_, _From, St) ->
     {reply, ?BADARG, St}.
 
 handle_cast(_, St) ->
     {noreply, St}.
 
+handle_info({timeout, _Ref, poll}, #st{ifs = Ifs} = S) ->
+    NewPollRef = start_poll_timer(),
+    NewIfs = get_interfaces(),
+    Diffs = lists:foldr(
+              fun(#iface{name = Name, status = St}, Acc) ->
+                      case lists:keyfind(Name, #iface.name, Ifs) of
+                          #iface{status = St0} when St0 =/= St ->
+                              [{Name, operstate, St0, St}|Acc];
+                          _ ->
+                              Acc
+                      end
+              end, [], NewIfs),
+    {noreply, tell_subscribers(Diffs, S#st{ifs = NewIfs,
+                                           poll_ref = NewPollRef})};
+handle_info({netlink, NRef, Iface, Field, Prev, New}, St) ->
+    {Prev1, New1} = adjust_status(IFace, Field, Prev, New),
+    {noreply, tell_subscribers([{Iface, Field, Prev1, New1}], St)};
 handle_info(_, St) ->
     {noreply, St}.
 
@@ -66,3 +111,59 @@ call(Req) ->
         Reply ->
             Reply
     end.
+
+tell_subscribers(Evts, #st{subscribers = Subs} = St) ->
+    lists:foreach(
+      fun({Name, Field, Old New}) ->
+              [Pid ! {rvi_netlink, Ref, Name, Field, Old New}
+               || #sub{name = N, pid = Pid, ref = Ref} <- Subs,
+                  match_name(N, Name)]
+      end, Evts),
+    St.
+
+get_interfaces() ->
+    case inet:getifaddrs() of
+        {ok, IFs} ->
+            [if_entry(I) || {_, Flags} <- IFs];
+        Error ->
+            ?error("getifaddrs() -> ~p", [Error]),
+            []
+    end.
+
+if_entry({Name, Opts}) ->
+    #iface{name = Name,
+        status = if_status(Opts),
+        opts = Opts}.
+
+if_status(Opts) ->
+    case lists:member(up, opt(flags, Opts, [])) of
+        true -> up;
+        false -> down
+    end.
+
+adjust_status(IF, operstate, A, B) ->
+    {adjust_operstate(A, IF), adjust_operstate(B, IF)};
+adjust_status(_, A, B) ->
+    {A, B}.
+
+adjust_operstate(undefined,  _) -> down;
+adjust_operstate(unknown, "lo") -> up;
+adjust_operstate(State,      _) -> State.
+
+opt(Key, Opts, Default) ->
+    case lists:keyfind(Key, 1, Opts) of
+        {_, Val} ->
+            Val;
+        false ->
+            Default
+    end.
+
+match_name(_, all) -> true;
+match_name(N, N  ) -> true;
+match_name(A, B) when is_binary(A), is_list(B) ->
+    binary_to_list(A) == B;
+match_name(_, _) ->
+    false.
+            
+start_poll_timer() ->
+    erlang:start_timer(?POLL_INTERVAL, self(), poll).
-- 
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