ensure that IAX2 and SIP sockets allow UDP fragmentation when running on Linux (thanks to Brian Candler on the asterisk-dev list for the tip)

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.2@44955 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -12856,10 +12856,13 @@ static int reload_config(void)
 		} else {
 			/* Allow SIP clients on the same host to access us: */
 			const int reuseFlag = 1;
+
 			setsockopt(sipsock, SOL_SOCKET, SO_REUSEADDR,
 				   (const char*)&reuseFlag,
 				   sizeof reuseFlag);
 
+			ast_enable_packet_fragmentation(sipsock);
+
 			if (bind(sipsock, (struct sockaddr *)&bindaddr, sizeof(bindaddr)) < 0) {
 				ast_log(LOG_WARNING, "Failed to bind to %s:%d: %s\n",
 				ast_inet_ntoa(iabuf, sizeof(iabuf), bindaddr.sin_addr), ntohs(bindaddr.sin_port),

include/asterisk/utils.h

@@ -235,4 +235,19 @@ char *ast_process_quotes_and_slashes(char *start, char find, char replace_with);
 int getloadavg(double *list, int nelem);
 #endif
 
+/*!
+  \brief Disable PMTU discovery on a socket
+  \param sock The socket to manipulate
+  \return Nothing
+
+  On Linux, UDP sockets default to sending packets with the Dont Fragment (DF)
+  bit set. This is supposedly done to allow the application to do PMTU
+  discovery, but Asterisk does not do this.
+
+  Because of this, UDP packets sent by Asterisk that are larger than the MTU
+  of any hop in the path will be lost. This function can be called on a socket
+  to ensure that the DF bit will not be set.
+ */
+void ast_enable_packet_fragmentation(int sock);
+
 #endif /* _ASTERISK_UTILS_H */

netsock.c

@@ -147,6 +147,8 @@ struct ast_netsock *ast_netsock_bindaddr(struct ast_netsock_list *list, struct i
 	if (setsockopt(netsocket, IPPROTO_IP, IP_TOS, &tos, sizeof(tos))) 
 		ast_log(LOG_WARNING, "Unable to set TOS to %d\n", tos);
 
+	ast_enable_packet_fragmentation(netsocket);
+
 	ns = malloc(sizeof(struct ast_netsock));
 	if (ns) {
 		/* Establish I/O callback for socket read */

utils.c

@@ -895,3 +895,14 @@ char *ast_process_quotes_and_slashes(char *start, char find, char replace_with)
 		*dataPut = 0;
 	return dataPut;
 }
+
+void ast_enable_packet_fragmentation(int sock)
+{
+#ifdef __linux__
+	int val = IP_PMTUDISC_DONT;
+	
+	if (setsockopt(sock, IPPROTO_IP, IP_MTU_DISCOVER, &val, sizeof(val)))
+		ast_log(LOG_WARNING, "Unable to disable PMTU discovery. Large UDP packets may fail to be delivered when sent from this socket.\n");
+#endif
+}
+