By default we have a route to reject compatible addresses:
::/96 ::1 UGRS 0 0 32768 8 lo0
But the corresponding check in ip6_input() is still commented because it
is "stronger than RFC1933". However since 1996 this RFC has been
obsoleted twice and the newer one, RFC4213 says:
The following changes have been performed since RFC 2893:
- Removed automatic tunneling and use of IPv4-compatible
addresses.
- [...]
Then later it explicitly documents:
After the decapsulation, the node MUST silently discard a packet with
an invalid IPv6 source address. The list of invalid source addresses
SHOULD include at least:
- all the IPv4-compatible IPv6 addresses [RFC3513] (::/96),
excluding the unspecified address for Duplicate Address Detection
(::/128)
- [...]
Do I understand correctly that it is time to enable this check?
Index: netinet6/ip6_input.c
===================================================================
RCS file: /cvs/src/sys/netinet6/ip6_input.c,v
retrieving revision 1.162
diff -u -p -r1.162 ip6_input.c
--- netinet6/ip6_input.c 6 Jul 2016 15:50:00 -0000 1.162
+++ netinet6/ip6_input.c 12 Jul 2016 09:17:04 -0000
@@ -299,20 +299,17 @@ ip6_input(struct mbuf *m)
ip6stat.ip6s_badscope++;
goto bad;
}
-#if 0
+
/*
* Reject packets with IPv4 compatible addresses (auto tunnel).
*
- * The code forbids auto tunnel relay case in RFC1933 (the check is
- * stronger than RFC1933). We may want to re-enable it if mech-xx
- * is revised to forbid relaying case.
+ * The code forbids automatic tunneling as per RFC4213.
*/
if (IN6_IS_ADDR_V4COMPAT(&ip6->ip6_src) ||
IN6_IS_ADDR_V4COMPAT(&ip6->ip6_dst)) {
ip6stat.ip6s_badscope++;
goto bad;
}
-#endif
/*
* If the packet has been received on a loopback interface it
