ping: Print reply with wrong source with warning

5e052ad ("ping: discard packets with wrong source address") correctly
hid replies with wrong source address to comply RFC 1122 (Section
3.2.1.3: "The IP source address in an ICMP Echo Reply MUST be the same
as the specific-destination address").

This caused to hide reply when pinging Subnet-Router anycast address.
Although it was fixed in the previous commit, relax this to admit the
reply but print warning "DIFFERENT ADDRESS!". ping is diagnostic program,
with insisting on RFC we force people to use tcpdump to see replies.

Link: #371

Reviewed-by: Matteo Croce <mcroce@microsoft.com>
Signed-off-by: Petr Vorel <pvorel@suse.cz>

Author: pevik

ping/ping.c

@@ -1504,6 +1504,7 @@ int ping4_parse_reply(struct ping_rts *rts, struct socket_st *sock,
 	int reply_ttl;
 	uint8_t *opts, *tmp_ttl;
 	int olen;
+	int wrong_source = 0;
 
 	/* Check the IP header */
 	ip = (struct iphdr *)buf;
@@ -1544,15 +1545,16 @@ int ping4_parse_reply(struct ping_rts *rts, struct socket_st *sock,
 	csfailed = in_cksum((unsigned short *)icp, cc, 0);
 
 	if (icp->type == ICMP_ECHOREPLY) {
-		if (!rts->broadcast_pings && !rts->multicast &&
-		    from->sin_addr.s_addr != rts->whereto.sin_addr.s_addr)
-			return 1;
 		if (!is_ours(rts, sock, icp->un.echo.id))
 			return 1;			/* 'Twas not our ECHO */
+
+		if (!rts->broadcast_pings && !rts->multicast &&
+		    from->sin_addr.s_addr != rts->whereto.sin_addr.s_addr)
+			wrong_source = 1;
 		if (gather_statistics(rts, (uint8_t *)icp, sizeof(*icp), cc,
 				      ntohs(icp->un.echo.sequence),
 				      reply_ttl, 0, tv, pr_addr(rts, from, sizeof *from),
-				      pr_echo_reply, rts->multicast)) {
+				      pr_echo_reply, rts->multicast, wrong_source)) {
 			fflush(stdout);
 			return 0;
 		}

ping/ping.h

@@ -389,7 +389,8 @@ extern void common_options(int ch);
 extern int gather_statistics(struct ping_rts *rts, uint8_t *icmph, int icmplen,
 			     int cc, uint16_t seq, int hops,
 			     int csfailed, struct timeval *tv, char *from,
-			     void (*pr_reply)(uint8_t *ptr, int cc), int multicast);
+			     void (*pr_reply)(uint8_t *ptr, int cc), int multicast,
+			     int wrong_source);
 extern void print_timestamp(struct ping_rts *rts);
 void fill(struct ping_rts *rts, char *patp, unsigned char *packet, size_t packet_size);
 

ping/ping6_common.c

@@ -803,6 +803,7 @@ int ping6_parse_reply(struct ping_rts *rts, socket_st *sock,
 	struct cmsghdr *c;
 	struct icmp6_hdr *icmph;
 	int hops = -1;
+	int wrong_source = 0;
 
 	for (c = CMSG_FIRSTHDR(msg); c; c = CMSG_NXTHDR(msg, c)) {
 		if (c->cmsg_level != IPPROTO_IPV6)
@@ -829,16 +830,18 @@ int ping6_parse_reply(struct ping_rts *rts, socket_st *sock,
 	}
 
 	if (icmph->icmp6_type == ICMP6_ECHO_REPLY) {
-		if (!rts->multicast && !rts->subnet_router_anycast &&
-		    memcmp(&from->sin6_addr.s6_addr, &rts->whereto6.sin6_addr.s6_addr, 16))
-			return 1;
 		if (!is_ours(rts, sock, icmph->icmp6_id))
 			return 1;
+
+		if (!rts->multicast && !rts->subnet_router_anycast &&
+		    memcmp(&from->sin6_addr.s6_addr, &rts->whereto6.sin6_addr.s6_addr, 16))
+			wrong_source = 1;
+
 		if (gather_statistics(rts, (uint8_t *)icmph, sizeof(*icmph), cc,
 				      ntohs(icmph->icmp6_seq),
 				      hops, 0, tv, pr_addr(rts, from, sizeof *from),
 				      pr_echo_reply,
-				      rts->multicast)) {
+				      rts->multicast, wrong_source)) {
 			fflush(stdout);
 			return 0;
 		}
@@ -851,7 +854,7 @@ int ping6_parse_reply(struct ping_rts *rts, socket_st *sock,
 				      seq,
 				      hops, 0, tv, pr_addr(rts, from, sizeof *from),
 				      pr_niquery_reply,
-				      rts->multicast))
+				      rts->multicast, 0))
 			return 0;
 	} else {
 		int nexthdr;

ping/ping_common.c

@@ -711,7 +711,8 @@ int main_loop(struct ping_rts *rts, ping_func_set_st *fset, socket_st *sock,
 int gather_statistics(struct ping_rts *rts, uint8_t *icmph, int icmplen,
 		      int cc, uint16_t seq, int hops,
 		      int csfailed, struct timeval *tv, char *from,
-		      void (*pr_reply)(uint8_t *icmph, int cc), int multicast)
+		      void (*pr_reply)(uint8_t *icmph, int cc), int multicast,
+		      int wrong_source)
 {
 	int dupflag = 0;
 	long triptime = 0;
@@ -804,10 +805,13 @@ int gather_statistics(struct ping_rts *rts, uint8_t *icmph, int icmplen,
 				printf(_(" time=%ld.%03ld ms"), triptime / 1000,
 				       triptime % 1000);
 		}
+
 		if (dupflag && (!multicast || rts->opt_verbose))
 			printf(_(" (DUP!)"));
 		if (csfailed)
 			printf(_(" (BAD CHECKSUM!)"));
+		if (wrong_source)
+			printf(_(" (DIFFERENT ADDRESS!)"));
 
 		/* check the data */
 		cp = ((unsigned char *)ptr) + sizeof(struct timeval);