BSD: Use MSG_DONTROUTE for unicast packets on FreeBSD

BSD systems cannot use SO_DONTROUTE, because it does not work properly
with multicast packets (perhaps it tries to find iface based on multicast
group address). But we can use MSG_DONTROUTE sendmsg() flag for unicast
packets. Works on FreeBSD, is ignored on OpenBSD and is broken on NetBSD
(i guess due to integrated routing table and ARP table).

1 files changed, 7 insertions, 1 deletions

diff --git a/sysdep/unix/io.c b/sysdep/unix/io.c
index 11a0d6f1..a960b7f8 100644
--- a/sysdep/unix/io.c
+++ b/sysdep/unix/io.c
@@ -1541,6 +1541,7 @@ sk_sendmsg(sock *s)
   struct iovec iov = {s->tbuf, s->tpos - s->tbuf};
   byte cmsg_buf[CMSG_TX_SPACE];
   sockaddr dst;
+  int flags = 0;
 
   sockaddr_fill(&dst, s->af, s->daddr, s->iface, s->dport);
 
@@ -1551,6 +1552,11 @@ sk_sendmsg(sock *s)
     .msg_iovlen = 1
   };
 
+#ifdef CONFIG_DONTROUTE_UNICAST
+  if (ipa_is_ip4(s->daddr) && ip4_is_unicast(ipa_to_ip4(s->daddr)))
+    flags = MSG_DONTROUTE;
+#endif
+
 #ifdef CONFIG_USE_HDRINCL
   byte hdr[20];
   struct iovec iov2[2] = { {hdr, 20}, iov };
@@ -1566,7 +1572,7 @@ sk_sendmsg(sock *s)
   if (s->flags & SKF_PKTINFO)
     sk_prepare_cmsgs(s, &msg, cmsg_buf, sizeof(cmsg_buf));
 
-  return sendmsg(s->fd, &msg, 0);
+  return sendmsg(s->fd, &msg, flags);
 }
 
 static inline int