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-rw-r--r--bgpd/bgp_packet.c45
1 files changed, 45 insertions, 0 deletions
diff --git a/bgpd/bgp_packet.c b/bgpd/bgp_packet.c
index 4d7f32de..271a21a0 100644
--- a/bgpd/bgp_packet.c
+++ b/bgpd/bgp_packet.c
@@ -1307,6 +1307,51 @@ bgp_open_receive (struct peer *peer, bgp_size_t size)
&& realpeer->status != OpenConfirm)
{
+ /* XXX: This is an awful problem..
+ *
+ * According to the RFC we should just let this connection (of the
+ * accepted 'peer') continue on to Established if the other
+ * connection (the 'realpeer' one) is in state Connect, and deal
+ * with the more larval FSM as/when it gets far enough to receive
+ * an Open. We don't do that though, we instead close the (more
+ * developed) accepted connection.
+ *
+ * This means there's a race, which if hit, can loop:
+ *
+ * FSM for A FSM for B
+ * realpeer accept-peer realpeer accept-peer
+ *
+ * Connect Connect
+ * Active
+ * OpenSent OpenSent
+ * <arrive here,
+ * Notify, delete>
+ * Idle Active
+ * OpenSent OpenSent
+ * <arrive here,
+ * Notify, delete>
+ * Idle
+ * <wait> <wait>
+ * Connect Connect
+ *
+ *
+ * If both sides are Quagga, they're almost certain to wait for
+ * the same amount of time of course (which doesn't preclude other
+ * implementations also waiting for same time). The race is
+ * exacerbated by high-latency (in bgpd and/or the network).
+ *
+ * The reason we do this is because our FSM is tied to our peer
+ * structure, which carries our configuration information, etc.
+ * I.e. we can't let the accepted-peer FSM continue on as it is,
+ * cause it's not associated with any actual peer configuration -
+ * it's just a dummy.
+ *
+ * It's possible we could hack-fix this by just bgp_stop'ing the
+ * realpeer and continueing on with the 'transfer FSM' below.
+ * Ideally, we need to seperate FSMs from struct peer.
+ *
+ * Setting one side to passive avoids the race, as a workaround.
+ */
if (BGP_DEBUG (events, EVENTS))
zlog_debug ("%s peer status is %s close connection",
realpeer->host, LOOKUP (bgp_status_msg,