tport_type_udp.c: use IP_MTU_DISCOVER socket option to turn off DF flag

Added check for IP_MTU_DISCOVER in m4/sac-su2.m4

darcs-hash:20080404151504-65a35-fe6a18371e2b2ac525204d8973cb0feab02f304c.gz

libsofia-sip-ua/tport/tport_type_udp.c

@@ -162,6 +162,17 @@ int tport_udp_init_primary(tport_primary_t *pri,
   }
 #endif
 
+#if HAVE_IP_MTU_DISCOVER
+  {
+    /* Turn off DF flag on Linux */
+    int dont = IP_PMTUDISC_DONT;
+    if (setsockopt(s, IPPROTO_IP, IP_MTU_DISCOVER, &dont, sizeof(dont)) < 0) {
+	SU_DEBUG_3(("setsockopt(%s): %s\n",
+		    "IP_MTU_DISCOVER", su_strerror(su_errno())));
+    }
+  }
+#endif
+
 #if HAVE_IP_RECVERR
   if (ai->ai_family == AF_INET || ai->ai_family == AF_INET6) {
     if (setsockopt(s, IPPROTO_IP, IP_RECVERR, &one, sizeof(one)) < 0) {

m4/sac-su2.m4

@@ -317,6 +317,13 @@ AC_DEFINE([HAVE_IP_MULTICAST_LOOP],1,[Define to 1 if you have IP_MULTICAST_LOOP]
 #include <sys/socket.h>
 #include <netinet/in.h>])
 
+AC_CHECK_DECL([IP_MTU_DISCOVER],
+AC_DEFINE([HAVE_IP_MTU_DISCOVER],1,
+[Define to 1 if you have IP_MTU_DISCOVER]),,[
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>])
+
 AC_CACHE_CHECK([for struct addrinfo],
 [ac_cv_struct_addrinfo],[
 ac_cv_struct_addrinfo=no