lacp: fix link state with multiple aggregators

When we have multiple aggregators, the link state should reflect the
state of the active aggregator.

This change was prompted by a script pruning 10GbE interfaces from an
lacp bundle with 100GbE interfaces. Mixing speeds like this creates multiple
aggregators.  When the last 10GbE interface was removed, lagg0 would loose
link because the current aggregator's port count would drop to 0, even
though the 100GbE aggregator had active ports. This left the system in a
hard to diagnose state where lagg0 reported "active", but all outgoing
IP traffic was dropped, due to the RT_LINK_IS_UP() check noticing lagg0's
if_link_state was marked as down.

Reviewed by: zlei
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D56579

1 files changed, 6 insertions, 2 deletions

diff --git a/sys/net/ieee8023ad_lacp.c b/sys/net/ieee8023ad_lacp.c
index 281d16bc6c05..8c695f71cc0f 100644
--- a/sys/net/ieee8023ad_lacp.c
+++ b/sys/net/ieee8023ad_lacp.c
@@ -682,6 +682,7 @@ static void
 lacp_disable_distributing(struct lacp_port *lp)
 {
 	struct lacp_aggregator *la = lp->lp_aggregator;
+	struct lacp_aggregator *la_active;
 	struct lacp_softc *lsc = lp->lp_lsc;
 	struct lagg_softc *sc = lsc->lsc_softc;
 	char buf[LACP_LAGIDSTR_MAX+1];
@@ -703,7 +704,6 @@ lacp_disable_distributing(struct lacp_port *lp)
 
 	TAILQ_REMOVE(&la->la_ports, lp, lp_dist_q);
 	la->la_nports--;
-	sc->sc_active = la->la_nports;
 
 	if (lsc->lsc_active_aggregator == la) {
 		lacp_suppress_distributing(lsc, la);
@@ -713,6 +713,8 @@ lacp_disable_distributing(struct lacp_port *lp)
 	}
 
 	lp->lp_state &= ~LACP_STATE_DISTRIBUTING;
+	la_active = lsc->lsc_active_aggregator;
+	sc->sc_active = la_active != NULL ? la_active->la_nports : 0;
 	if_link_state_change(sc->sc_ifp,
 	    sc->sc_active ? LINK_STATE_UP : LINK_STATE_DOWN);
 }
@@ -721,6 +723,7 @@ static void
 lacp_enable_distributing(struct lacp_port *lp)
 {
 	struct lacp_aggregator *la = lp->lp_aggregator;
+	struct lacp_aggregator *la_active;
 	struct lacp_softc *lsc = lp->lp_lsc;
 	struct lagg_softc *sc = lsc->lsc_softc;
 	char buf[LACP_LAGIDSTR_MAX+1];
@@ -739,7 +742,6 @@ lacp_enable_distributing(struct lacp_port *lp)
 	KASSERT(la->la_refcnt > la->la_nports, ("aggregator refcnt invalid"));
 	TAILQ_INSERT_HEAD(&la->la_ports, lp, lp_dist_q);
 	la->la_nports++;
-	sc->sc_active = la->la_nports;
 
 	lp->lp_state |= LACP_STATE_DISTRIBUTING;
 
@@ -750,6 +752,8 @@ lacp_enable_distributing(struct lacp_port *lp)
 		/* try to become the active aggregator */
 		lacp_select_active_aggregator(lsc);
 
+	la_active = lsc->lsc_active_aggregator;
+	sc->sc_active = la_active != NULL ? la_active->la_nports : 0;
 	if_link_state_change(sc->sc_ifp,
 	    sc->sc_active ? LINK_STATE_UP : LINK_STATE_DOWN);
 }