[PATCH] IPv4 over IPv6 nexthop support on FreeBSD

[Luiz Amaral]

Hello,

While experimenting in FreeBSD 13.1 with IPv4 over IPv6 nexthop routes, 
I realized that BIRD was unable to read routes from the kernel as well 
as export routes to the kernel. The support for it was implemented in 
FreeBSD 13.1 [1].

I have attached a patch that made it work for me on FreeBSD 13.1, both 
importing and exporting to/from kernel. I believe the patch will still 
need some work, as from a quick look, OpenBSD still has no support for 
it. I'm happy to implement any suggested improvements and send a v2 of it.

Thank you,
Luiz

[1] https://reviews.freebsd.org/D30398
diff --git a/sysdep/bsd/krt-sock.c b/sysdep/bsd/krt-sock.c
index 1f793293..92f8c837 100644
--- a/sysdep/bsd/krt-sock.c
+++ b/sysdep/bsd/krt-sock.c
@@ -314,6 +314,10 @@ krt_send_route(struct krt_proto *p, int cmd, rte *e)
       if (ipa_is_link_local(gw))
 	_I0(gw) = 0xfe800000 | (i->index & 0x0000ffff);
 
+      if (ipa_is_ip6(gw)) {
+        af = AF_INET6;
+      }
+
       sockaddr_fill(&gate, af, gw, NULL, 0);
       msg.rtm.rtm_flags |= RTF_GATEWAY;
       msg.rtm.rtm_addrs |= RTA_GATEWAY;
@@ -469,7 +473,7 @@ krt_read_route(struct ks_msg *msg, struct krt_proto *p, int scan)
 
   idst  = ipa_from_sa(&dst);
   imask = ipa_from_sa(&mask);
-  igate = (gate.sa.sa_family == dst.sa.sa_family) ? ipa_from_sa(&gate) : IPA_NONE;
+  igate = ipa_from_sa(&gate);
 
 #ifdef KRT_SHARED_SOCKET
   if (!scan)