Hi,
as far as I can see a dual stack carp interface does not care whether it
receives advertisements addressed to IPv4 or IPv6. Any one will do.
So I propose to send IPv6 advertisements only when IPv4 is not possible.
Why?
- Noise can be reduced by using unicast advertisements.
This is only possible for IPv4 by ``ifconfig carppeer``.
I don't like flooding the whole network with carp advertisements when
I may also unicast them.
- breaking IPv6 connectivity (for example by running iked without -6)
will start a preempt-war, because failing ip6_output will cause the
demote counter to be increased. That's what hit me.
I would suggest a change like this:
Index: ip_carp.c
===================================================================
RCS file: /cvs/src/sys/netinet/ip_carp.c,v
retrieving revision 1.342
diff -u -p -r1.342 ip_carp.c
--- ip_carp.c 8 Nov 2019 07:51:41 -0000 1.342
+++ ip_carp.c 15 Jan 2020 10:45:56 -0000
@@ -1175,7 +1175,7 @@ carp_send_ad(struct carp_vhost_entry *vh
}
}
#ifdef INET6
- if (sc->sc_naddrs6) {
+ else if (sc->sc_naddrs6) {
struct ip6_hdr *ip6;
MGETHDR(m, M_DONTWAIT, MT_HEADER);
one could also use a slightly smaller hammer and only avoid sending IPv6
if the user requested an IPv4 unicast address:
- if (sc->sc_naddrs6) {
+ if (sc->sc_naddrs6 &&
+ (! sc->sc_naddrs ||
+ sc->sc_peer.s_addr == INADDR_CARP_GROUP) ) {
Christopher
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