From ce0d5605591573087d7331a4858453b45244a3bb Mon Sep 17 00:00:00 2001 From: Donald Sharp Date: Fri, 31 Jan 2025 18:53:30 -0500 Subject: [PATCH] bgpd: With suppress-fib-pending ensure withdrawal is sent When you have suppress-fib-pending turned on it is possible to end up in a situation where the prefix is not withdrawn from downstream peers. Here is the timing that I believe is happening: a) have 2 paths to a peer. b) receive a withdrawal from 1 path, set BGP_NODE_FIB_INSTALL_PENDING and send the route install to zebra. c) receive a withdrawal from the other path. d) At this point we have a dest->flags set BGP_NODE_FIB_INSTALL_PENDING old_select the path_info going away, new_select is NULL e) A bit further down we call group_announce_route() which calls the code to see if we should advertise the path. It sees the BGP_NODE_FIB_INSTALL_PENDING flag and says, nope. f) the route is sent to zebra to withdraw, which unsets the BGP_NODE_FIB_INSTALL_PENDING. g) This function winds up and deletes the path_info. Dest now has no path infos. h) BGP receives the route install(from step b) and unsets the BGP_NODE_FIB_INSTALL_PENDING flag i) BGP receives the route removed from zebra (from step f) and unsets the flag again. We know if there is no new_select, let's go ahead and just unset the PENDING flag to allow the withdrawal to go out at the time when the second withdrawal is received. Signed-off-by: Donald Sharp (cherry picked from commit 4e8eda74ec7d30ba84e7f53f077f4b896728505a) --- bgpd/bgp_route.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/bgpd/bgp_route.c b/bgpd/bgp_route.c index 35c9937a060d..aa2c3a6a560e 100644 --- a/bgpd/bgp_route.c +++ b/bgpd/bgp_route.c @@ -3482,6 +3482,12 @@ static void bgp_process_main_one(struct bgp *bgp, struct bgp_dest *dest, BGP_PATH_ATTR_CHANGED); UNSET_FLAG(new_select->flags, BGP_PATH_MULTIPATH_CHG); UNSET_FLAG(new_select->flags, BGP_PATH_LINK_BW_CHG); + } else { + /* + * Ensure that on uninstall that the INSTALL_PENDING + * is no longer set + */ + UNSET_FLAG(dest->flags, BGP_NODE_FIB_INSTALL_PENDING); } /* call bmp hook for loc-rib route update / withdraw after flags were