From 2677b1b73610b0a1aabe0f743e24fd955d6434b3 Mon Sep 17 00:00:00 2001 From: Enke Chen Date: Thu, 24 Oct 2024 10:50:37 -0700 Subject: [PATCH] bgpd: compare aigp after local route check in bgp_path_info_cmp() For consistency between RIB and BGP, the aigp comparison should be made after the local route check in bgp bestpath selection. Signed-off-by: Enke Chen (cherry picked from commit 6a7049aaacc32e6a473a4d56ca61444d1e1eb45d) --- bgpd/bgp_route.c | 55 +++++++++++++++++++++++------------------------- doc/user/bgp.rst | 8 +++---- 2 files changed, 30 insertions(+), 33 deletions(-) diff --git a/bgpd/bgp_route.c b/bgpd/bgp_route.c index 96eabe1f4e..c60c4357be 100644 --- a/bgpd/bgp_route.c +++ b/bgpd/bgp_route.c @@ -1063,7 +1063,32 @@ int bgp_path_info_cmp(struct bgp *bgp, struct bgp_path_info *new, } } - /* Tie-breaker - AIGP (Metric TLV) attribute */ + /* 3. Local route check. We prefer: + * - BGP_ROUTE_STATIC + * - BGP_ROUTE_AGGREGATE + * - BGP_ROUTE_REDISTRIBUTE + */ + new_origin = !(new->sub_type == BGP_ROUTE_NORMAL || new->sub_type == BGP_ROUTE_IMPORTED); + exist_origin = !(exist->sub_type == BGP_ROUTE_NORMAL || + exist->sub_type == BGP_ROUTE_IMPORTED); + + if (new_origin && !exist_origin) { + *reason = bgp_path_selection_local_route; + if (debug) + zlog_debug("%s: %s wins over %s due to preferred BGP_ROUTE type", pfx_buf, + new_buf, exist_buf); + return 1; + } + + if (!new_origin && exist_origin) { + *reason = bgp_path_selection_local_route; + if (debug) + zlog_debug("%s: %s loses to %s due to preferred BGP_ROUTE type", pfx_buf, + new_buf, exist_buf); + return 0; + } + + /* 3.5. Tie-breaker - AIGP (Metric TLV) attribute */ if (CHECK_FLAG(newattr->flag, ATTR_FLAG_BIT(BGP_ATTR_AIGP)) && CHECK_FLAG(existattr->flag, ATTR_FLAG_BIT(BGP_ATTR_AIGP)) && CHECK_FLAG(bgp->flags, BGP_FLAG_COMPARE_AIGP)) { @@ -1093,34 +1118,6 @@ int bgp_path_info_cmp(struct bgp *bgp, struct bgp_path_info *new, } } - /* 3. Local route check. We prefer: - * - BGP_ROUTE_STATIC - * - BGP_ROUTE_AGGREGATE - * - BGP_ROUTE_REDISTRIBUTE - */ - new_origin = !(new->sub_type == BGP_ROUTE_NORMAL || - new->sub_type == BGP_ROUTE_IMPORTED); - exist_origin = !(exist->sub_type == BGP_ROUTE_NORMAL || - exist->sub_type == BGP_ROUTE_IMPORTED); - - if (new_origin && !exist_origin) { - *reason = bgp_path_selection_local_route; - if (debug) - zlog_debug( - "%s: %s wins over %s due to preferred BGP_ROUTE type", - pfx_buf, new_buf, exist_buf); - return 1; - } - - if (!new_origin && exist_origin) { - *reason = bgp_path_selection_local_route; - if (debug) - zlog_debug( - "%s: %s loses to %s due to preferred BGP_ROUTE type", - pfx_buf, new_buf, exist_buf); - return 0; - } - /* Here if these are imported routes then get ultimate pi for * path compare. */ diff --git a/doc/user/bgp.rst b/doc/user/bgp.rst index 49d5cac4a5..2e993aa7c1 100644 --- a/doc/user/bgp.rst +++ b/doc/user/bgp.rst @@ -154,16 +154,16 @@ bottom until one of the factors can be used. Prefer higher local preference routes to lower. +3. **Local route check** + + Prefer local routes (statics, aggregates, redistributed) to received routes. + If ``bgp bestpath aigp`` is enabled, and both paths that are compared have AIGP attribute, BGP uses AIGP tie-breaking unless both of the paths have the AIGP metric attribute. This means that the AIGP attribute is not evaluated during the best path selection process between two paths when one path does not have the AIGP attribute. -3. **Local route check** - - Prefer local routes (statics, aggregates, redistributed) to received routes. - 4. **AS path length check** Prefer shortest hop-count AS_PATHs. -- 2.39.5