bgpd: fix fast external fallover behavior
ISSUES
1. When an interface goes down, the zclient callbacks are invoked
in the following order: (a) address_delete() that removes the
connected address list: ifp->connected, (b) interface_down()
that performs "fast external fallover" operation. The operation
relies on ifp->connected to look for peers that should be brought
down. That's a cyclic dependency.
2. 'ttl-security' configuration handler sets peer->ttl to
MAXTTL (so that BGP packets are sent with TTL=255, as per the
requirement of ttl-security). This, however, is incompatible
with 'fast external fallover' as the fallover operation checks
for (ttl == 1) to determine directly connected peers.
3. The current fallover operation does not work for IPv6 address family.
PATCH
1. The patch removes the dependency on 'ifp->connected' list for fast
fallover. The peer already contains a nexthop structure that reflects
the peering address. The nexthop structure has a pointer to the
interface (ifp) that peering address resolves to. Everytime the TCP
connection succeeds, the ifp is updated. The patch uses this ifp in
the interface_down() callback for a match for the peers that should be
brought down.
2. The evaluation for directly connected peering is enhanced as
'peer->ttl == 1' OR 'peer->gtsm_hops == 1'. Thus a ttl-security
configuration on the peer with one hop is directly connected and
should be brought down under 'fast external fallover'.
3. Because of fix (1), IPv6 address family works automatically.
Signed-off-by: Pradosh Mohapatra <pmohapat@cumulusnetworks.com>
Reviewed-by: Dinesh G Dutt <ddutt@cumulusnetworks.com>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/bgpd/bgp_zebra.c b/bgpd/bgp_zebra.c
index 26b97c2..0f21232 100644
--- a/bgpd/bgp_zebra.c
+++ b/bgpd/bgp_zebra.c
@@ -147,12 +147,11 @@
for (ALL_LIST_ELEMENTS (ifp->connected, node, nnode, c))
bgp_connected_delete (c);
- /* Fast external-failover (Currently IPv4 only) */
+ /* Fast external-failover */
{
struct listnode *mnode;
struct bgp *bgp;
struct peer *peer;
- struct interface *peer_if;
for (ALL_LIST_ELEMENTS_RO (bm->bgp, mnode, bgp))
{
@@ -161,15 +160,10 @@
for (ALL_LIST_ELEMENTS (bgp->peer, node, nnode, peer))
{
- if (peer->ttl != 1)
+ if ((peer->ttl != 1) && (peer->gtsm_hops != 1))
continue;
- if (peer->su.sa.sa_family == AF_INET)
- peer_if = if_lookup_by_ipv4 (&peer->su.sin.sin_addr);
- else
- continue;
-
- if (ifp == peer_if)
+ if (ifp == peer->nexthop.ifp)
BGP_EVENT_ADD (peer, BGP_Stop);
}
}