Rewrite receive code to support TTL

crude/main.c

@@ -937,31 +937,62 @@ static void get_str_addr(struct sockaddr_storage src_addr,char buffer[]){
  */
 static int rec_n_print(unsigned short port, unsigned long limit)
 {
-	long               rec_bytes = 0;     /* Bytes read            */
+	ssize_t            rec_bytes = 0;     /* Bytes read            */
 	int                src_len   = sizeof(struct sockaddr_storage);
+	int                ttl = 64;
+	int                received_ttl;
 	struct sockaddr_storage src_addr;
+	struct msghdr msgh;
+	struct iovec iov;
 	struct timeval     time1;
 	struct udp_data    *udp_ptr;
 	struct sockaddr_storage  d_add;
+	struct cmsghdr *cmptr = NULL;
+	#define CONTROLLEN (sizeof(struct cmsghdr) + sizeof(int))
 	char buffer[PMAXSIZE], str1[INET6_ADDRSTRLEN], str2[INET6_ADDRSTRLEN];
 
 	/* Initialize some variables */
 	memset(buffer,0,PMAXSIZE);
 	memset(str1,0,INET6_ADDRSTRLEN);
 	memset(str2,0,INET6_ADDRSTRLEN);
-	char srcport[10];
-
-	while(1)
+	cmptr = malloc(CONTROLLEN);
+
+	iov.iov_base       = &buffer;
+	iov.iov_len        = sizeof(buffer);
+	memset(&msgh, 0, sizeof(msgh));
+	msgh.msg_name       = &src_addr;
+	msgh.msg_namelen    = sizeof(src_addr);
+	msgh.msg_iov        = &iov;
+	msgh.msg_iovlen     = 1;
+	msgh.msg_control    = (caddr_t) cmptr;
+	msgh.msg_controllen = CONTROLLEN;
+
+	if(setsockopt(main_socket, IPPROTO_IP, IP_RECVTTL, &ttl,sizeof(ttl))>0) 
 	{
-		rec_bytes = recvfrom(main_socket, buffer, PMAXSIZE, 0,
-		                     (struct sockaddr *)&src_addr, (socklen_t *)&src_len);
+		RUDEBUG1("crude: unable to receive TTL values: %s\n",strerror(errno));
+	}
+	for( ; ; )
+	{
+		rec_bytes = recvmsg(main_socket, &msgh, MSG_WAITALL);
 		if(rec_bytes <= 0)
 		{
 			RUDEBUG1("crude: error when receiving packet: %s\n",strerror(errno));
 		}
 		else
 		{
-			gettimeofday(&time1, NULL);
+			struct cmsghdr *cmsg;
+			int *ttlptr;
+			received_ttl = -1;
+			for (cmsg = CMSG_FIRSTHDR(&msgh); cmsg != NULL;
+					cmsg = CMSG_NXTHDR(&msgh,cmsg)) {
+				if ((cmsg->cmsg_level == IPPROTO_IP) && (cmsg->cmsg_type == IP_TTL) &&
+						(cmsg->cmsg_len) ){
+					ttlptr = (int *) CMSG_DATA(cmsg);
+					received_ttl = *ttlptr;
+					break;
+				}
+			}
+ 			gettimeofday(&time1, NULL);
 			pkt_count++;
 			udp_ptr = (struct udp_data*)buffer;
 			d_add = udp_ptr->dest_addr;
@@ -970,13 +1001,13 @@ static int rec_n_print(unsigned short port, unsigned long limit)
 			get_str_addr(d_add,str2);
 
 			printf("ID=%lu SEQ=%lu SRC=%s:%hu DST=%s:%hu "
-			       "Tx=%lu.%06lu Rx=%ld.%06ld SIZE=%ld\n",
+			       "Tx=%lu.%06lu Rx=%ld.%06ld TTL=%d SIZE=%ld\n",
 			       (unsigned long)ntohl(udp_ptr->flow_id),
 			       (unsigned long)ntohl(udp_ptr->sequence_number),
 			       str1, ntohs(((struct sockaddr_in *)&src_addr)->sin_port), str2, port,
 			       (unsigned long)ntohl(udp_ptr->tx_time_seconds),
 			       (unsigned long)ntohl(udp_ptr->tx_time_useconds),
-			       time1.tv_sec, time1.tv_usec, rec_bytes);
+			       time1.tv_sec, time1.tv_usec, received_ttl, rec_bytes);
 			fflush(stdout);
 		}