BGP: Improve handling of hold and keepalive timers

The effective keepalive time now scales relative to the negotiated
hold time, to maintain proportion between the keepalive time and the
hold time. This avoids issues when both keepalive and hold times
were configured, the hold time was negotiated to a smaller value,
but the keepalive time stayed the same.

Add new options 'min hold time' and 'min keepalive time', which reject
session attempts with too small hold time.

Improve validation of config options an their documentation.

Thanks to Alexander Zubkov and Sergei Goriunov for suggestions.

1 files changed, 15 insertions, 0 deletions

diff --git a/proto/bgp/bgp.c b/proto/bgp/bgp.c
index ad78d5e5..f4098e04 100644
--- a/proto/bgp/bgp.c
+++ b/proto/bgp/bgp.c
@@ -2007,6 +2007,21 @@ bgp_postconfig(struct proto_config *CF)
   if (internal && cf->enforce_first_as)
     cf_error("Enforce first AS check is requires EBGP sessions");
 
+  if (cf->keepalive_time > cf->hold_time)
+    cf_error("Keepalive time must be at most hold time");
+
+  if (cf->keepalive_time > (cf->hold_time / 2))
+    log(L_WARN "Keepalive time should be at most 1/2 of hold time");
+
+  if (cf->min_hold_time > cf->hold_time)
+    cf_error("Min hold time (%u) exceeds hold time (%u)",
+	     cf->min_hold_time, cf->hold_time);
+
+  uint keepalive_time = cf->keepalive_time ?: cf->hold_time / 3;
+  if (cf->min_keepalive_time > keepalive_time)
+    cf_error("Min keepalive time (%u) exceeds keepalive time (%u)",
+	     cf->min_keepalive_time, keepalive_time);
+
 
   struct bgp_channel_config *cc;
   BGP_CF_WALK_CHANNELS(cf, cc)