Handle the absence of IP_MTU_DISCOVER

configure.ac

@@ -89,6 +89,11 @@ AC_CHECK_DECL([htobe64],
      [[#include <libkern/OSByteOrder.h>]])],
   [[#include <endian.h>]])
 
+AC_CHECK_DECL([IP_MTU_DISCOVER],
+  [AC_DEFINE([HAVE_IP_MTU_DISCOVER], [1],
+     [Define if IP_MTU_DISCOVER is a valid sockopt.])],
+  , [[#include <netinet/ip.h>]])
+
 # Checks for protobuf
 PKG_CHECK_MODULES([protobuf], [protobuf])
 

src/network/network.cc

@@ -106,11 +106,13 @@ void Connection::setup( void )
   }
 
   /* Disable path MTU discovery */
+#ifdef HAVE_IP_MTU_DISCOVER
   char flag = IP_PMTUDISC_DONT;
   socklen_t optlen = sizeof( flag );
   if ( setsockopt( sock, IPPROTO_IP, IP_MTU_DISCOVER, &flag, optlen ) < 0 ) {
     throw NetworkException( "setsockopt", errno );
   }
+#endif
 }
 
 Connection::Connection( const char *desired_ip ) /* server */