Fix lagg failover due to missing notifications

When using lagg failover mode neither Gratuitous ARP (IPv4) or Unsolicited
Neighbour Advertisements (IPv6) are sent to notify other nodes that the
address may have moved.

This results is slow failover, dropped packets and network outages for the
lagg interface when the primary link goes down.

We now use the new if_link_state_change_cond with the force param set to
allow lagg to force through link state changes and hence fire a
ifnet_link_event which are now monitored by rip and nd6.

Upon receiving these events each protocol trigger the relevant
notifications:
* inet4 => Gratuitous ARP
* inet6 => Unsolicited Neighbour Announce

This also fixes the carp IPv6 NA's that stopped working after r251584 which
added the ipv6_route__llma route.

The new behavour can be controlled using the sysctls:
* net.link.ether.inet.arp_on_link
* net.inet6.icmp6.nd6_on_link

Also removed unused param from lagg_port_state and added descriptions for the
sysctls while here.

PR:		156226
MFC after:	1 month
Sponsored by:	Multiplay
Differential Revision:	https://reviews.freebsd.org/D4111

4 files changed, 30 insertions, 10 deletions

diff --git a/sys/net/if.c b/sys/net/if.c
index b88c05e..177f356 100644
--- a/sys/net/if.c
+++ b/sys/net/if.c
@@ -126,7 +126,7 @@ SX_SYSINIT(ifdescr_sx, &ifdescr_sx, "ifnet descr");
 
 void	(*bridge_linkstate_p)(struct ifnet *ifp);
 void	(*ng_ether_link_state_p)(struct ifnet *ifp, int state);
-void	(*lagg_linkstate_p)(struct ifnet *ifp, int state);
+void	(*lagg_linkstate_p)(struct ifnet *ifp);
 /* These are external hooks for CARP. */
 void	(*carp_linkstate_p)(struct ifnet *ifp);
 void	(*carp_demote_adj_p)(int, char *);
@@ -1984,6 +1984,8 @@ if_unroute(struct ifnet *ifp, int flag, int fam)
 
 	if (ifp->if_carp)
 		(*carp_linkstate_p)(ifp);
+	if (ifp->if_lagg)
+		(*lagg_linkstate_p)(ifp);
 	rt_ifmsg(ifp);
 }
 
@@ -2005,6 +2007,8 @@ if_route(struct ifnet *ifp, int flag, int fam)
 			pfctlinput(PRC_IFUP, ifa->ifa_addr);
 	if (ifp->if_carp)
 		(*carp_linkstate_p)(ifp);
+	if (ifp->if_lagg)
+		(*lagg_linkstate_p)(ifp);
 	rt_ifmsg(ifp);
 #ifdef INET6
 	in6_if_up(ifp);
@@ -2019,17 +2023,27 @@ int	(*vlan_tag_p)(struct ifnet *, uint16_t *);
 int	(*vlan_setcookie_p)(struct ifnet *, void *);
 void	*(*vlan_cookie_p)(struct ifnet *);
 
+void
+if_link_state_change(struct ifnet *ifp, int link_state)
+{
+
+	return if_link_state_change_cond(ifp, link_state, 0);
+}
+
 /*
  * Handle a change in the interface link state. To avoid LORs
  * between driver lock and upper layer locks, as well as possible
  * recursions, we post event to taskqueue, and all job
  * is done in static do_link_state_change().
+ *
+ * If the current link state matches link_state and force isn't
+ * specified no action is taken.
  */
 void
-if_link_state_change(struct ifnet *ifp, int link_state)
+if_link_state_change_cond(struct ifnet *ifp, int link_state, int force)
 {
-	/* Return if state hasn't changed. */
-	if (ifp->if_link_state == link_state)
+
+	if (ifp->if_link_state == link_state && !force)
 		return;
 
 	ifp->if_link_state = link_state;
@@ -2057,7 +2071,7 @@ do_link_state_change(void *arg, int pending)
 	if (ifp->if_bridge)
 		(*bridge_linkstate_p)(ifp);
 	if (ifp->if_lagg)
-		(*lagg_linkstate_p)(ifp, link_state);
+		(*lagg_linkstate_p)(ifp);
 
 	if (IS_DEFAULT_VNET(curvnet))
 		devctl_notify("IFNET", ifp->if_xname,
diff --git a/sys/net/if_lagg.c b/sys/net/if_lagg.c
index 730a044..6ca3f22 100644
--- a/sys/net/if_lagg.c
+++ b/sys/net/if_lagg.c
@@ -106,7 +106,7 @@ static int	lagg_port_create(struct lagg_softc *, struct ifnet *);
 static int	lagg_port_destroy(struct lagg_port *, int);
 static struct mbuf *lagg_input(struct ifnet *, struct mbuf *);
 static void	lagg_linkstate(struct lagg_softc *);
-static void	lagg_port_state(struct ifnet *, int);
+static void	lagg_port_state(struct ifnet *);
 static int	lagg_port_ioctl(struct ifnet *, u_long, caddr_t);
 static int	lagg_port_output(struct ifnet *, struct mbuf *,
 		    const struct sockaddr *, struct route *);
@@ -1774,7 +1774,12 @@ lagg_linkstate(struct lagg_softc *sc)
 			break;
 		}
 	}
-	if_link_state_change(sc->sc_ifp, new_link);
+
+	/*
+	 * Force state change to ensure ifnet_link_event is generated allowing
+	 * protocols to notify other nodes of potential address move.
+	 */
+	if_link_state_change_cond(sc->sc_ifp, new_link, 1);
 
 	/* Update if_baudrate to reflect the max possible speed */
 	switch (sc->sc_proto) {
@@ -1797,7 +1802,7 @@ lagg_linkstate(struct lagg_softc *sc)
 }
 
 static void
-lagg_port_state(struct ifnet *ifp, int state)
+lagg_port_state(struct ifnet *ifp)
 {
 	struct lagg_port *lp = (struct lagg_port *)ifp->if_lagg;
 	struct lagg_softc *sc = NULL;
@@ -1813,7 +1818,7 @@ lagg_port_state(struct ifnet *ifp, int state)
 	LAGG_WUNLOCK(sc);
 }
 
-struct lagg_port *
+static struct lagg_port *
 lagg_link_active(struct lagg_softc *sc, struct lagg_port *lp)
 {
 	struct lagg_port *lp_next, *rval = NULL;
diff --git a/sys/net/if_lagg.h b/sys/net/if_lagg.h
index 195ac3a..ea59762 100644
--- a/sys/net/if_lagg.h
+++ b/sys/net/if_lagg.h
@@ -281,7 +281,7 @@ struct lagg_port {
 #define	LAGG_UNLOCK_ASSERT(_sc)	rm_assert(&(_sc)->sc_mtx, RA_UNLOCKED)
 
 extern struct mbuf *(*lagg_input_p)(struct ifnet *, struct mbuf *);
-extern void	(*lagg_linkstate_p)(struct ifnet *, int );
+extern void	(*lagg_linkstate_p)(struct ifnet *);
 
 int		lagg_enqueue(struct ifnet *, struct mbuf *);
 
diff --git a/sys/net/if_var.h b/sys/net/if_var.h
index 5911cec..2cbd76c 100644
--- a/sys/net/if_var.h
+++ b/sys/net/if_var.h
@@ -500,6 +500,7 @@ struct ifmultiaddr *
 void	if_free(struct ifnet *);
 void	if_initname(struct ifnet *, const char *, int);
 void	if_link_state_change(struct ifnet *, int);
+void	if_link_state_change_cond(struct ifnet *, int, int);
 int	if_printf(struct ifnet *, const char *, ...) __printflike(2, 3);
 void	if_ref(struct ifnet *);
 void	if_rele(struct ifnet *);