Merge pull request FRRouting#17240 from opensourcerouting/fix/backpor…

…t_d46511d4456ccaccfdac34b456c1c225a29609c8_10.0 bgpd: compare aigp after local route check in bgp_path_info_cmp()
opensourcerouting · Oct 25, 2024 · 4287007 · 4287007
2 parents 4f43c13 + acc673d
commit 4287007
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Showing 2 changed files with 30 additions and 33 deletions.
diff --git a/bgpd/bgp_route.c b/bgpd/bgp_route.c
@@ -966,7 +966,32 @@ 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)) {
@@ -996,34 +1021,6 @@ 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
@@ -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.