From 5e80932275419e688b3ad608d6371867953fe4b9 Mon Sep 17 00:00:00 2001 From: Ethan Jackson Date: Wed, 11 May 2011 17:55:41 -0700 Subject: [PATCH] cfm: No longer trigger fault upon unexpected ccm_interval. According to the 802.1ag specification, when a CCM is received which advertises a misconfigured transmission interval, a fault should be triggered. This patch goes against the spec by simply warning when this happens. This is done for several reasons. - Faults can cause controllers to make potentially expensive changes in the network topology. - Faults can be maliciously triggered by crafting invalid CCMs. - Reducing the number of places in the code where rmp->fault and cfm->fault are changed makes the code easier to debug and reason about. --- lib/cfm.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/lib/cfm.c b/lib/cfm.c index a504714cf..943cfc10d 100644 --- a/lib/cfm.c +++ b/lib/cfm.c @@ -378,6 +378,15 @@ cfm_process_heartbeat(struct cfm *cfm, const struct ofpbuf *p) return; } + /* According to the 802.1ag specification, reception of a CCM with an + * incorrect ccm_interval should trigger a fault. We ignore this + * requirement for several reasons. + * + * Faults can cause a controller or Open vSwitch to make potentially + * expensive changes to the network topology. It seems prudent to trigger + * them judiciously, especially when CFM is used to check slave status of + * bonds. Furthermore, faults can be maliciously triggered by crafting + * invalid CCMs. */ if (memcmp(ccm->maid, cfm->maid, sizeof ccm->maid)) { cfmi->x_recv_time = time_msec(); cfm->fault = true; @@ -391,8 +400,12 @@ cfm_process_heartbeat(struct cfm *cfm, const struct ofpbuf *p) if (rmp) { rmp->recv_time = time_msec(); - rmp->fault = ccm_interval != cfmi->ccm_interval; - cfm->fault = rmp->fault || cfm->fault; + + if (ccm_interval != cfmi->ccm_interval) { + VLOG_WARN_RL(&rl, "received a CCM with an invalid interval" + " (%"PRIu8") from RMP %"PRIu16, ccm_interval, + rmp->mpid); + } } else { cfmi->x_recv_time = time_msec(); cfm->fault = true; -- 2.43.0