resolved: rework synthesizing logic

With this change we'll now also generate synthesized RRs for the local
LLMNR hostname (first label of system hostname), the local mDNS hostname
(first label of system hostname suffixed with .local), the "gateway"
hostname and all the reverse PTRs. This hence takes over part of what
nss-myhostname already implemented.

Local hostnames resolve to the set of local IP addresses. Since the
addresses are possibly on different interfaces it is necessary to change
the internal DnsAnswer object to track per-RR interface indexes, and to
change the bus API to always return the interface per-address rather than
per-reply. This change also patches  the existing clients for resolved
accordingly (nss-resolve + systemd-resolve-host).

This also changes the routing logic for queries slightly: we now ensure
that the local hostname is never resolved via LLMNR, thus making it
trustable on the local system.

1 files changed, 65 insertions, 68 deletions

diff --git a/src/resolve-host/resolve-host.c b/src/resolve-host/resolve-host.c
index 7525d7c32f..3f45a9f0e8 100644
--- a/src/resolve-host/resolve-host.c
+++ b/src/resolve-host/resolve-host.c
@@ -41,13 +41,13 @@ static uint16_t arg_class = 0;
 static bool arg_legend = true;
 static uint64_t arg_flags = 0;
 
-static void print_source(int ifindex, uint64_t flags, usec_t rtt) {
+static void print_source(uint64_t flags, usec_t rtt) {
         char rtt_str[FORMAT_TIMESTAMP_MAX];
 
         if (!arg_legend)
                 return;
 
-        if (ifindex <= 0 && flags == 0)
+        if (flags == 0)
                 return;
 
         fputs("\n-- Information acquired via", stdout);
@@ -58,11 +58,6 @@ static void print_source(int ifindex, uint64_t flags, usec_t rtt) {
                        flags & SD_RESOLVED_LLMNR_IPV4 ? " LLMNR/IPv4" : "",
                        flags & SD_RESOLVED_LLMNR_IPV6 ? " LLMNR/IPv6" : "");
 
-        if (ifindex > 0) {
-                char ifname[IF_NAMESIZE] = "";
-                printf(" interface %s", strna(if_indextoname(ifindex, ifname)));
-        }
-
         assert_se(format_timespan(rtt_str, sizeof(rtt_str), rtt, 100));
 
         printf(" in %s", rtt_str);
@@ -76,14 +71,18 @@ static int resolve_host(sd_bus *bus, const char *name) {
         _cleanup_bus_message_unref_ sd_bus_message *req = NULL, *reply = NULL;
         _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
         const char *canonical = NULL;
+        char ifname[IF_NAMESIZE] = "";
         unsigned c = 0;
-        int r, ifindex;
+        int r;
         uint64_t flags;
         usec_t ts;
 
         assert(name);
 
-        log_debug("Resolving %s (family %s, ifindex %i).", name, af_to_name(arg_family) ?: "*", arg_ifindex);
+        if (arg_ifindex > 0 && !if_indextoname(arg_ifindex, ifname))
+                return log_error_errno(errno, "Failed to resolve interface name for index %i: %m", arg_ifindex);
+
+        log_debug("Resolving %s (family %s, interface %s).", name, af_to_name(arg_family) ?: "*", isempty(ifname) ? "*" : ifname);
 
         r = sd_bus_message_new_method_call(
                         bus,
@@ -109,22 +108,19 @@ static int resolve_host(sd_bus *bus, const char *name) {
 
         ts = now(CLOCK_MONOTONIC) - ts;
 
-        r = sd_bus_message_read(reply, "i", &ifindex);
+        r = sd_bus_message_enter_container(reply, 'a', "(iiay)");
         if (r < 0)
                 return bus_log_parse_error(r);
 
-        r = sd_bus_message_enter_container(reply, 'a', "(iay)");
-        if (r < 0)
-                return bus_log_parse_error(r);
-
-        while ((r = sd_bus_message_enter_container(reply, 'r', "iay")) > 0) {
+        while ((r = sd_bus_message_enter_container(reply, 'r', "iiay")) > 0) {
                 const void *a;
-                int family;
                 size_t sz;
                 _cleanup_free_ char *pretty = NULL;
-                char ifname[IF_NAMESIZE] = "";
+                int ifindex, family;
+
+                assert_cc(sizeof(int) == sizeof(int32_t));
 
-                r = sd_bus_message_read(reply, "i", &family);
+                r = sd_bus_message_read(reply, "ii", &ifindex, &family);
                 if (r < 0)
                         return bus_log_parse_error(r);
 
@@ -142,26 +138,17 @@ static int resolve_host(sd_bus *bus, const char *name) {
                 }
 
                 if (sz != FAMILY_ADDRESS_SIZE(family)) {
-                        log_error("%s: systemd-resolved returned address of invalid size %zu for family %s",
-                                  name, sz, af_to_name(family) ?: "unknown");
+                        log_error("%s: systemd-resolved returned address of invalid size %zu for family %s", name, sz, af_to_name(family) ?: "unknown");
                         continue;
                 }
 
-                if (ifindex > 0) {
-                        char *t;
-
-                        t = if_indextoname(ifindex, ifname);
-                        if (!t) {
-                                log_error("Failed to resolve interface name for index %i", ifindex);
-                                continue;
-                        }
-                }
+                ifname[0] = 0;
+                if (ifindex > 0 && !if_indextoname(ifindex, ifname))
+                        log_warning_errno(errno, "Failed to resolve interface name for index %i: %m", ifindex);
 
                 r = in_addr_to_string(family, a, &pretty);
-                if (r < 0) {
-                        log_error_errno(r, "%s: failed to print address: %m", name);
-                        continue;
-                }
+                if (r < 0)
+                        return log_error_errno(r, "Failed to print address for %s: %m", name);
 
                 printf("%*s%s %s%s%s\n",
                        (int) strlen(name), c == 0 ? name : "", c == 0 ? ":" : " ",
@@ -192,7 +179,7 @@ static int resolve_host(sd_bus *bus, const char *name) {
                 return -ESRCH;
         }
 
-        print_source(ifindex, flags, ts);
+        print_source(flags, ts);
 
         return 0;
 }
@@ -204,7 +191,6 @@ static int resolve_address(sd_bus *bus, int family, const union in_addr_union *a
         char ifname[IF_NAMESIZE] = "";
         uint64_t flags;
         unsigned c = 0;
-        const char *n;
         usec_t ts;
         int r;
 
@@ -212,19 +198,15 @@ static int resolve_address(sd_bus *bus, int family, const union in_addr_union *a
         assert(IN_SET(family, AF_INET, AF_INET6));
         assert(address);
 
+        if (ifindex <= 0)
+                ifindex = arg_ifindex;
+
         r = in_addr_to_string(family, address, &pretty);
         if (r < 0)
                 return log_oom();
 
-        if (ifindex > 0) {
-                char *t;
-
-                t = if_indextoname(ifindex, ifname);
-                if (!t) {
-                        log_error("Failed to resolve interface name for index %i", ifindex);
-                        return -errno;
-                }
-        }
+        if (ifindex > 0 && !if_indextoname(ifindex, ifname))
+                return log_error_errno(errno, "Failed to resolve interface name for index %i: %m", ifindex);
 
         log_debug("Resolving %s%s%s.", pretty, isempty(ifname) ? "" : "%", ifname);
 
@@ -238,10 +220,6 @@ static int resolve_address(sd_bus *bus, int family, const union in_addr_union *a
         if (r < 0)
                 return bus_log_create_error(r);
 
-        r = sd_bus_message_set_auto_start(req, false);
-        if (r < 0)
-                return bus_log_create_error(r);
-
         r = sd_bus_message_append(req, "ii", ifindex, family);
         if (r < 0)
                 return bus_log_create_error(r);
@@ -264,19 +242,31 @@ static int resolve_address(sd_bus *bus, int family, const union in_addr_union *a
 
         ts = now(CLOCK_MONOTONIC) - ts;
 
-        r = sd_bus_message_read(reply, "i", &ifindex);
-        if (r < 0)
-                return bus_log_parse_error(r);
-
-        r = sd_bus_message_enter_container(reply, 'a', "s");
+        r = sd_bus_message_enter_container(reply, 'a', "(is)");
         if (r < 0)
                 return bus_log_create_error(r);
 
-        while ((r = sd_bus_message_read(reply, "s", &n)) > 0) {
+        while ((r = sd_bus_message_enter_container(reply, 'r', "is")) > 0) {
+                const char *n;
+
+                assert_cc(sizeof(int) == sizeof(int32_t));
 
-                printf("%*s%s%s%s %s\n",
+                r = sd_bus_message_read(reply, "is", &ifindex, &n);
+                if (r < 0)
+                        return r;
+
+                r = sd_bus_message_exit_container(reply);
+                if (r < 0)
+                        return r;
+
+                ifname[0] = 0;
+                if (ifindex > 0 && !if_indextoname(ifindex, ifname))
+                        log_warning_errno(errno, "Failed to resolve interface name for index %i: %m", ifindex);
+
+                printf("%*s%*s%*s%s %s\n",
                        (int) strlen(pretty), c == 0 ? pretty : "",
-                       isempty(ifname) ? "" : "%", ifname,
+                       isempty(ifname) ? 0 : 1, c > 0 || isempty(ifname) ? "" : "%",
+                       (int) strlen(ifname), c == 0 ? ifname : "",
                        c == 0 ? ":" : " ",
                        n);
 
@@ -298,7 +288,7 @@ static int resolve_address(sd_bus *bus, int family, const union in_addr_union *a
                 return -ESRCH;
         }
 
-        print_source(ifindex, flags, ts);
+        print_source(flags, ts);
 
         return 0;
 }
@@ -333,14 +323,18 @@ static int resolve_record(sd_bus *bus, const char *name) {
 
         _cleanup_bus_message_unref_ sd_bus_message *req = NULL, *reply = NULL;
         _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
+        char ifname[IF_NAMESIZE] = "";
         unsigned n = 0;
         uint64_t flags;
-        int r, ifindex;
+        int r;
         usec_t ts;
 
         assert(name);
 
-        log_debug("Resolving %s %s %s.", name, dns_class_to_string(arg_class), dns_type_to_string(arg_type));
+        if (arg_ifindex > 0 && !if_indextoname(arg_ifindex, ifname))
+                return log_error_errno(errno, "Failed to resolve interface name for index %i: %m", arg_ifindex);
+
+        log_debug("Resolving %s %s %s (interface %s).", name, dns_class_to_string(arg_class), dns_type_to_string(arg_type), isempty(ifname) ? "*" : ifname);
 
         r = sd_bus_message_new_method_call(
                         bus,
@@ -367,23 +361,22 @@ static int resolve_record(sd_bus *bus, const char *name) {
 
         ts = now(CLOCK_MONOTONIC) - ts;
 
-        r = sd_bus_message_read(reply, "i", &ifindex);
+        r = sd_bus_message_enter_container(reply, 'a', "(iqqay)");
         if (r < 0)
                 return bus_log_parse_error(r);
 
-        r = sd_bus_message_enter_container(reply, 'a', "(qqay)");
-        if (r < 0)
-                return bus_log_parse_error(r);
-
-        while ((r = sd_bus_message_enter_container(reply, 'r', "qqay")) > 0) {
+        while ((r = sd_bus_message_enter_container(reply, 'r', "iqqay")) > 0) {
                 _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
                 _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
                 _cleanup_free_ char *s = NULL;
                 uint16_t c, t;
+                int ifindex;
                 const void *d;
                 size_t l;
 
-                r = sd_bus_message_read(reply, "qq", &c, &t);
+                assert_cc(sizeof(int) == sizeof(int32_t));
+
+                r = sd_bus_message_read(reply, "iqq", &ifindex, &c, &t);
                 if (r < 0)
                         return bus_log_parse_error(r);
 
@@ -415,7 +408,11 @@ static int resolve_record(sd_bus *bus, const char *name) {
                         return r;
                 }
 
-                printf("%s\n", s);
+                ifname[0] = 0;
+                if (ifindex > 0 && !if_indextoname(ifindex, ifname))
+                        log_warning_errno(errno, "Failed to resolve interface name for index %i: %m", ifindex);
+
+                printf("%s%s%s\n", s, isempty(ifname) ? "" : " # interface ", ifname);
                 n++;
         }
         if (r < 0)
@@ -434,7 +431,7 @@ static int resolve_record(sd_bus *bus, const char *name) {
                 return -ESRCH;
         }
 
-        print_source(ifindex, flags, ts);
+        print_source(flags, ts);
 
         return 0;
 }