Date: Thu, 29 Sep 2011 16:49:54 +0200 From: Damien Fleuriot <ml@my.gd> To: "freebsd-stable@freebsd.org" <freebsd-stable@freebsd.org> Subject: Re: CARP interfaces and mastership issue Message-ID: <4E848592.5050300@my.gd> In-Reply-To: <CAE63ME71mXfHeV7hxvtkv8q-m0rVQ8-z7aNfF61Cb0poVJCpRQ@mail.gmail.com> References: <4E71C059.5060404@hi-media.com> <4E84627B.2050609@my.gd> <CAE63ME71mXfHeV7hxvtkv8q-m0rVQ8-z7aNfF61Cb0poVJCpRQ@mail.gmail.com>
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>
>
>
> Quick follow-up again.
>
> This is the code for sys/netinet/ip_carp.c on FreeBSD 8.2, OpenBSD
> 3.8, OpenBSD 3.9 in function carp_setrun(struct carp_softc *sc,
> sa_family_t af)
>
>
>
> FREEBSD 8.2-PRERELEASE with init + preempt => auto MASTER bug
> Function starts at line 1371.
> ---
> switch (sc->sc_state) {
> case INIT:
> if (carp_opts[CARPCTL_PREEMPT] && !carp_suppress_preempt) {
> carp_send_ad_locked(sc);
> carp_send_arp(sc);
> #ifdef INET6
> carp_send_na(sc);
> #endif /* INET6 */
> CARP_LOG("%s: INIT -> MASTER (preempting)\n",
> SC2IFP(sc)->if_xname);
> carp_set_state(sc, MASTER);
> carp_setroute(sc, RTM_ADD);
> } else {
> CARP_LOG("%s: INIT -> BACKUP\n", SC2IFP(sc)->if_xname);
> carp_set_state(sc, BACKUP);
> carp_setroute(sc, RTM_DELETE);
> carp_setrun(sc, 0);
> }
> break;
> ---
>
> OPENBSD 3.8 with init + preempt => auto MASTER bug
> Function starts at line 1293.
> ---
> case INIT:
> if (carp_opts[CARPCTL_PREEMPT] && !carp_suppress_preempt) {
> carp_set_state(sc, MASTER);
> carp_setroute(sc, RTM_ADD);
> carp_send_ad(sc);
> carp_send_arp(sc);
> #ifdef INET6
> carp_send_na(sc);
> #endif /* INET6 */
> } else {
> carp_set_state(sc, BACKUP);
> carp_setroute(sc, RTM_DELETE);
> carp_setrun(sc, 0);
> }
> break;
> ---
>
>
>
> OPENBSD 3.9 with bug fixed
> Function starts at line 1348.
> ---
> switch (sc->sc_state) {
> case INIT:
> carp_set_state(sc, BACKUP);
> carp_setroute(sc, RTM_DELETE);
> carp_setrun(sc, 0);
> break;
> ---
>
>
> It looks like the root cause is there.
>
> I'll rebuild and test, keep you updated.
Find below my test results with the OpenBSD39 implementation which
forces an INIT -> BACKUP transition regardless of preempt.
# sysctl net.inet.carp.preempt
net.inet.carp.preempt: 1
# sysctl net.inet.carp.suppress_preempt
net.inet.carp.suppress_preempt: 0
# ifconfig carp17
carp17: flags=8<LOOPBACK> metric 0 mtu 1500
inet 46.182.[snip] netmask 0xffffffff
inet 46.182.[snip] netmask 0xffffffff
inet 46.182.[snip] netmask 0xffffffff
inet 46.182.[snip] netmask 0xffffffff
inet 46.182.[snip] netmask 0xffffffff
carp: INIT vhid 117 advbase 1 advskew 200
# ifconfig carp17 up; ./check_carp17_status.sh
count: 0 carp: BACKUP vhid 117 advbase 1 advskew 200
count: 1 carp: BACKUP vhid 117 advbase 1 advskew 200
count: 2 carp: BACKUP vhid 117 advbase 1 advskew 200
count: 3 carp: BACKUP vhid 117 advbase 1 advskew 200
count: 4 carp: BACKUP vhid 117 advbase 1 advskew 200
count: 5 carp: BACKUP vhid 117 advbase 1 advskew 200
count: 6 carp: BACKUP vhid 117 advbase 1 advskew 200
count: 7 carp: BACKUP vhid 117 advbase 1 advskew 200
count: 8 carp: BACKUP vhid 117 advbase 1 advskew 200
count: 9 carp: BACKUP vhid 117 advbase 1 advskew 200
count: 10 carp: BACKUP vhid 117 advbase 1 advskew 200
# dmesg
carp17: INIT -> BACKUP
carp17: link state changed to DOWN
Looks like it works.
I'm afraid I cannot test actual preemption by shutting down a physical
interface on the MASTER, because they're actually used in production and
I've got users logged in to their VPN on pf1.
I see no reason this should break anything however, it only forces the
CARP interface to assume a BACKUP state right after INIT, as it normally
should, regardless of preemption.
I'm filling a PR + patch.
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