Address an edge condition that we found at work, where the carp(4)

interface goes to issue LINK_UP, then LINK_DOWN, then LINK_UP at
cold boot.  This behavior is not observed when carp(4) interface
is created slightly later, when the underlying interface is fully
up.

Before this change what happen at boot is roughly:

 - ifconfig creates em0 interface;
 - ifconfig clones a carp device using em0;
   (em0's link state is DOWN at this point)
 - carp state: INIT -> BACKUP [*]
 - carp state: BACKUP -> MASTER
 - [Some negotiate between em0 and switch]
 - em0 kicks up link state change event
   (em0's link state is now up DOWN at this point)
 - do_link_state_change() -> carp_carpdev_state()
 - carp state: MASTER -> INIT (via carp_set_state(sc, INIT)) [+]
 - carp state: INIT -> BACKUP
 - carp state: BACKUP -> MASTER

At the [*] stage, em0 did not received any broadcast message from other
node, and assume our node is the master, thus carp(4) sets the link
state to "UP" after becoming a master.  At [+], the master status
is forcely set to "INIT", then an election is casted, after which our
node would actually become a master.

We believe that at the [*] stage, the master status should remain as
"INIT" since the underlying parent interface's link state is not up.

Obtained from:	iXsystems, Inc.
Reported by:	jpaetzel
MFC after:	2 months

1 files changed, 2 insertions, 1 deletions

diff --git a/sys/netinet/ip_carp.c b/sys/netinet/ip_carp.c
index 433c0f0..743a901 100644
--- a/sys/netinet/ip_carp.c
+++ b/sys/netinet/ip_carp.c
@@ -1369,7 +1369,8 @@ carp_setrun(struct carp_softc *sc, sa_family_t af)
 		CARP_SCLOCK_ASSERT(sc);
 
 	if (SC2IFP(sc)->if_flags & IFF_UP &&
-	    sc->sc_vhid > 0 && (sc->sc_naddrs || sc->sc_naddrs6))
+	    sc->sc_vhid > 0 && (sc->sc_naddrs || sc->sc_naddrs6) &&
+	    sc->sc_carpdev->if_link_state == LINK_STATE_UP)
 		SC2IFP(sc)->if_drv_flags |= IFF_DRV_RUNNING;
 	else {
 		SC2IFP(sc)->if_drv_flags &= ~IFF_DRV_RUNNING;