[bgpd] low-impact DoS: crash on malformed community with debug set

[bgpd] low-impact DoS: crash on malformed community with debug set

2007-09-07 Paul Jakma <paul.jakma@sun.com>

	* (general) bgpd can be made crash by remote peers if debug
	  bgp updates is set, due to NULL pointer dereference.
	  Reported by "Mu Security Research Team",
	  <security@musecurity.com>.
	* bgp_attr.c: (bgp_attr_community) If community length is 0,
	  don't set the community-present attribute bit, just return
	  early.
	* bgp_debug.c: (community_str,community_com2str) Check com
	  pointer before dereferencing.