net/linux/addrs: fix point-to-point peer address bug (#1239)

For point-to-point interfaces IFA_ADDRESS points to the peer address instead of the local address.

>  Important comment:
>  IFA_ADDRESS is prefix address, rather than local interface address.
>  It makes no difference for normally configured broadcast interfaces,
>  but for point-to-point IFA_ADDRESS is DESTINATION address,
>  local address is supplied in IFA_LOCAL attribute.

src/net/linux/addrs.c

@@ -81,6 +81,7 @@ static bool parse_msg_addr(struct nlmsghdr *msg, ssize_t len,
 	for (nlh = msg; NLMSG_OK(nlh, len); nlh = NLMSG_NEXT(nlh, len)) {
 		struct sa sa;
 		uint32_t flags;
+		void *addr;
 		char if_name[IF_NAMESIZE];
 
 		if (nlh->nlmsg_type == NLMSG_DONE) {
@@ -109,13 +110,19 @@ static bool parse_msg_addr(struct nlmsghdr *msg, ssize_t len,
 				continue;
 		}
 
+		if (rta_tb[IFA_LOCAL])
+			/* looks like point-to-point network, use local
+			 * address, instead of peer */
+			addr = RTA_DATA(rta_tb[IFA_LOCAL]);
+		else
+			addr = RTA_DATA(rta_tb[IFA_ADDRESS]);
+
 		if (ifa->ifa_family == AF_INET) {
 			sa_init(&sa, AF_INET);
-			sa.u.in.sin_addr.s_addr =
-				*(uint32_t *)RTA_DATA(rta_tb[IFA_ADDRESS]);
+			sa.u.in.sin_addr.s_addr = *(uint32_t *)addr;
 		}
 		else if (ifa->ifa_family == AF_INET6) {
-			sa_set_in6(&sa, RTA_DATA(rta_tb[IFA_ADDRESS]), 0);
+			sa_set_in6(&sa, addr, 0);
 			sa_set_scopeid(&sa, ifa->ifa_index);
 		}
 		else