From 7ab604ab79d60b839e2d38020fd6ccbe0be033b8 Mon Sep 17 00:00:00 2001 From: Chirag Shah Date: Mon, 25 Nov 2019 14:34:29 -0800 Subject: [PATCH] bgpd: Handle possible non-selection of local route In rare situations, the local route in a VNI may not get selected as the best route. One situation is during a race between bgp and zebra which was addressed in a prior commit. This change addresses another situation where due to a change of tunnel IP, it is possible that a received route may be selected as the best route if the path selection needs to take next hop IPs into consideration. This is a pretty convoluted scenario, but the code should handle it and delete and withdraw the local route as well as (re)install the received route. Ticket: CM-24114 Reviewed By: CCR-9487 Testing Done: 1. Manual tests - note, problem is not readily reproducible 2. evpn-smoke - results documented in the ticket Signed-off-by: Vivek Venkatraman Signed-off-by: Chirag Shah --- bgpd/bgp_evpn.c | 60 +++++++++++++++++++++++++++++++++---------------- 1 file changed, 41 insertions(+), 19 deletions(-) diff --git a/bgpd/bgp_evpn.c b/bgpd/bgp_evpn.c index f3c514fb15..1b356af6d8 100644 --- a/bgpd/bgp_evpn.c +++ b/bgpd/bgp_evpn.c @@ -1825,9 +1825,15 @@ static int update_evpn_route(struct bgp *bgp, struct bgpevpn *vpn, /* lock ri to prevent freeing in evpn_route_select_install */ bgp_path_info_lock(pi); - /* Perform route selection; this is just to set the flags correctly - * as local route in the VNI always wins. - */ + + /* Perform route selection. Normally, the local route in the + * VNI is expected to win and be the best route. However, if + * there is a race condition where a host moved from local to + * remote and the remote route was received in BGP just prior + * to the local MACIP notification from zebra, the remote + * route would win, and we should evict the defunct local route + * and (re)install the remote route into zebra. + */ evpn_route_select_install(bgp, vpn, rn); /* * If the new local route was not selected evict it and tell zebra @@ -2100,24 +2106,40 @@ static int update_all_type2_routes(struct bgp *bgp, struct bgpevpn *vpn) update_evpn_route_entry(bgp, vpn, afi, safi, rn, &attr, 0, &pi, 0, seq); - /* Perform route selection; this is just to set the flags - * correctly as local route in the VNI always wins. + /* lock ri to prevent freeing in evpn_route_select_install */ + bgp_path_info_lock(pi); + + /* Perform route selection. Normally, the local route in the + * VNI is expected to win and be the best route. However, + * under peculiar situations (e.g., tunnel (next hop) IP change + * that causes best selection to be based on next hop), a + * remote route could win. If the local route is the best, + * ensure it is updated in the global EVPN route table and + * advertised to peers; otherwise, ensure it is evicted and + * (re)install the remote route into zebra. */ evpn_route_select_install(bgp, vpn, rn); - - attr_new = pi->attr; - - /* Update route in global routing table. */ - rd_rn = bgp_afi_node_get(bgp->rib[afi][safi], afi, safi, - (struct prefix *)evp, &vpn->prd); - assert(rd_rn); - update_evpn_route_entry(bgp, vpn, afi, safi, rd_rn, attr_new, 0, - &global_pi, 0, - mac_mobility_seqnum(attr_new)); - - /* Schedule for processing and unlock node. */ - bgp_process(bgp, rd_rn, afi, safi); - bgp_unlock_node(rd_rn); + if (!CHECK_FLAG(pi->flags, BGP_PATH_SELECTED)) { + evpn_cleanup_local_non_best_route(bgp, vpn, rn, pi); + /* unlock pi */ + bgp_path_info_unlock(pi); + } else { + attr_new = pi->attr; + /* unlock pi */ + bgp_path_info_unlock(pi); + + /* Update route in global routing table. */ + rd_rn = bgp_afi_node_get(bgp->rib[afi][safi], afi, safi, + (struct prefix *)evp, &vpn->prd); + assert(rd_rn); + update_evpn_route_entry(bgp, vpn, afi, safi, rd_rn, + attr_new, 0, &global_pi, 0, + mac_mobility_seqnum(attr_new)); + + /* Schedule for processing and unlock node. */ + bgp_process(bgp, rd_rn, afi, safi); + bgp_unlock_node(rd_rn); + } /* Unintern temporary. */ aspath_unintern(&attr.aspath); -- 2.39.5