[gssdp] Use if_nametoindex if available

[Jens Georg <jensgeorg src gnome org>]

commit 8bdb91cf436e5bc0ac59cf1a7582947a0df61dd9
Author: Jens Georg <mail jensge org>
Date:   Fri Feb 19 17:09:04 2016 +0100

    Use if_nametoindex if available
    
    Signed-off-by: Jens Georg <mail jensge org>
    
    https://bugzilla.gnome.org/show_bug.cgi?id=762324

 configure.ac            |   12 ++++++++++++
 libgssdp/gssdp-client.c |    5 ++++-
 2 files changed, 16 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index b0f72b9..8cfbfc5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -133,6 +133,18 @@ AC_CHECK_TYPE(struct in_pktinfo,
               ], [#include <netinet/ip.h>])
 AM_CONDITIONAL([HAVE_PKTINFO], [test $HAVE_PKTINFO = yes], [])
 
+dnl Check for if_nametoindex
+AC_MSG_CHECKING([for if_nametoindex])
+AC_TRY_COMPILE([#include <net/if.h>],
+               [if_nametoindex("lo")],
+               [HAVE_IFNAMETOINDEX=yes
+                AC_DEFINE([HAVE_IFNAMETOINDEX], [1], [Whether we have if_nametoindex])
+               ],
+               [
+                HAVE_IFNAMETOINDEX=no
+               ])
+AC_MSG_RESULT([$HAVE_IFNAMETOINDEX])
+
 dnl Check for SIOCGIFINDEX
 AC_MSG_CHECKING([for SIOCGIFINDEX])
 AC_TRY_COMPILE([#include <sys/ioctl.h>],
diff --git a/libgssdp/gssdp-client.c b/libgssdp/gssdp-client.c
index ad46780..e5d0c01 100644
--- a/libgssdp/gssdp-client.c
+++ b/libgssdp/gssdp-client.c
@@ -1382,7 +1382,10 @@ extract_address_and_prefix (PIP_ADAPTER_UNICAST_ADDRESS  adapter,
 static int
 query_ifindex (const char *iface_name)
 {
-#ifdef HAVE_SIOCGIFINDEX
+#if defined(HAVE_IFNAMETOINDEX)
+        return if_nametoindex (iface_name);
+
+#elif defied(HAVE_SIOCGIFINDEX)
         int fd;
         int result;
         struct ifreq ifr;