From 9a622300e88f7c439773fc385c98051796ac67cf Mon Sep 17 00:00:00 2001
From: Philip Withnall <philip.withnall@collabora.co.uk>
Date: Fri, 4 Jul 2014 11:41:52 +0100
Subject: [PATCH] agent: Use getnameinfo() instead of inet_ntop() to stringify
 addresses
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inet_ntop() drops IPv6 link-local scope IDs on the floor, which means
libnice doesn’t generate any IPv6 candidates for link-local connections,
meaning that it will theoretically fail to negotiate a connection on an
IPv6-only network where the two peers are local.

Fix that by using getnameinfo() to convert sockaddrs to strings, which
preserves the scope ID.

There are no portability concerns — getnameinfo() is POSIX.1-2001, and
isn’t used on Windows (although it is supported, surprisingly).
---
 agent/interfaces.c | 40 +++++++++++++++++-----------------------
 1 file changed, 17 insertions(+), 23 deletions(-)

diff --git a/agent/interfaces.c b/agent/interfaces.c
index 2332095..0e0c666 100644
--- a/agent/interfaces.c
+++ b/agent/interfaces.c
@@ -58,6 +58,7 @@
 
 #include <sys/socket.h>
 #include <netinet/in.h>
+#include <netdb.h>
 
 #ifdef __sun
 #include <sys/sockio.h>
@@ -205,36 +206,29 @@ nice_interfaces_get_local_ips (gboolean include_loopback)
   /* Loop through the interface list and get the IP address of each IF */
   for (ifa = results; ifa; ifa = ifa->ifa_next) {
     char addr_as_string[INET6_ADDRSTRLEN+1];
-
-    union {
-      struct sockaddr *addr;
-      struct sockaddr_in *in;
-      struct sockaddr_in6 *in6;
-    } sa;
-
-    sa.addr = ifa->ifa_addr;
+    size_t addr_len;
 
     /* no ip address from interface that is down */
     if ((ifa->ifa_flags & IFF_UP) == 0)
       continue;
 
-    if (ifa->ifa_addr == NULL) {
-      continue;
-    } else if (ifa->ifa_addr->sa_family == AF_INET) {
-      if (inet_ntop (AF_INET, &sa.in->sin_addr, addr_as_string,
-              INET6_ADDRSTRLEN) == NULL)
-        continue;
-    } else if (ifa->ifa_addr->sa_family == AF_INET6) {
-      /* Skip link-local addresses, they require a scope */
-      if (IN6_IS_ADDR_LINKLOCAL (&sa.in6->sin6_addr))
-        continue;
-
-      if (inet_ntop (AF_INET6, &sa.in6->sin6_addr, addr_as_string,
-              INET6_ADDRSTRLEN) == NULL)
-        continue;
-    } else
+    if (ifa->ifa_addr == NULL)
       continue;
 
+    /* Convert to a string. */
+    switch (ifa->ifa_addr->sa_family) {
+      case AF_INET: addr_len = sizeof (struct sockaddr_in); break;
+      case AF_INET6: addr_len = sizeof (struct sockaddr_in6); break;
+      default: g_assert_not_reached ();
+    }
+
+    if (getnameinfo (ifa->ifa_addr, addr_len,
+            addr_as_string, sizeof (addr_as_string), NULL, 0,
+            NI_NUMERICHOST) != 0) {
+      nice_debug ("Failed to convert address to string for interface ‘%s’.",
+          ifa->ifa_name);
+      continue;
+    }
 
     nice_debug ("Interface:  %s", ifa->ifa_name);
     nice_debug ("IP Address: %s", addr_as_string);
-- 
2.7.4