ripd: switch from sendto() to sendmsg()

For unknown reasons, the IP_MULTICAST_IF sockoption doesn't
seem to work when the given socket is bound to a VRF device on
Linux. Switch from sendto() to sendmsg() so that we can specify the
outgoing interface of multicast packets using IP_PKTINFO ancillary
data. This also makes ripd more consistent with ripngd, which also
uses sendmsg() to send packets on the wire.

Signed-off-by: Renato Westphal <renato@opensourcerouting.org>

diff --git a/ripd/ripd.c b/ripd/ripd.c
index 6b9c5fe886b6c2f9dad33475b1f1b88b9eb0ccc1..916fba2269a4a9a132395c2d6e1cc62a85c286b9 100644 (file)
--- a/ripd/ripd.c
+++ b/ripd/ripd.c
@@ -1386,6 +1386,13 @@ static int rip_send_packet(uint8_t *buf, int size, struct sockaddr_in *to,
        struct rip *rip;
        int ret;
        struct sockaddr_in sin;
+       struct msghdr msg;
+       struct iovec iov;
+#ifdef GNU_LINUX
+       struct cmsghdr *cmsgptr;
+       char adata[256] = {};
+       struct in_pktinfo *pkt;
+#endif /* GNU_LINUX */
 
        assert(ifc != NULL);
        ri = ifc->ifp->info;
@@ -1448,8 +1455,27 @@ static int rip_send_packet(uint8_t *buf, int size, struct sockaddr_in *to,
                rip_interface_multicast_set(rip->sock, ifc);
        }
 
-       ret = sendto(rip->sock, buf, size, 0, (struct sockaddr *)&sin,
-                    sizeof(struct sockaddr_in));
+       memset(&msg, 0, sizeof(msg));
+       msg.msg_name = (void *)&sin;
+       msg.msg_namelen = sizeof(struct sockaddr_in);
+       msg.msg_iov = &iov;
+       msg.msg_iovlen = 1;
+       iov.iov_base = buf;
+       iov.iov_len = size;
+
+#ifdef GNU_LINUX
+       msg.msg_control = (void *)adata;
+       msg.msg_controllen = CMSG_SPACE(sizeof(struct in_pktinfo));
+
+       cmsgptr = (struct cmsghdr *)adata;
+       cmsgptr->cmsg_len = CMSG_LEN(sizeof(struct in_pktinfo));
+       cmsgptr->cmsg_level = IPPROTO_IP;
+       cmsgptr->cmsg_type = IP_PKTINFO;
+       pkt = (struct in_pktinfo *)CMSG_DATA(cmsgptr);
+       pkt->ipi_ifindex = ifc->ifp->ifindex;
+#endif /* GNU_LINUX */
+
+       ret = sendmsg(rip->sock, &msg, 0);
 
        if (IS_RIP_DEBUG_EVENT)
                zlog_debug("SEND to  %s.%d", inet_ntoa(sin.sin_addr),