BGP: handle implicit confederation membership (#4990)

* handle case where BGP peer is implicitly in a confederation with its peer
batfish · Oct 15, 2019 · d9245fb · d9245fb
1 parent 569ba14
commit d9245fb
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Showing 2 changed files with 24 additions and 2 deletions.
diff --git a/...cts/batfish-common-protocol/src/main/java/org/batfish/datamodel/bgp/BgpTopologyUtils.java b/...cts/batfish-common-protocol/src/main/java/org/batfish/datamodel/bgp/BgpTopologyUtils.java
@@ -512,15 +512,31 @@ static AsPair computeAsPair(
     }
     // Initiator is inside a confederation
     if (initiatorConfed != null) {
-      if (listenerRemoteAsns.contains(initiatorConfed)
+      // Initiator and listener are in the same AS, so they're in the same confederation
+      if (initiatorLocalAs.equals(listenerLocalAs)) {
+        if (listenerRemoteAsns.contains(initiatorLocalAs)
+            && initiatorRemoteAsns.contains(listenerLocalAs)) {
+          return new AsPair(initiatorLocalAs, listenerLocalAs);
+        } else {
+          return null;
+        }
+      } else if (listenerRemoteAsns.contains(initiatorConfed)
           && initiatorRemoteAsns.contains(listenerLocalAs)) {
         return new AsPair(initiatorConfed, listenerLocalAs);
       } else {
         return null;
       }
     } else {
       // Listener is inside a confederation
-      if (listenerRemoteAsns.contains(initiatorLocalAs)
+      // Initiator and listener are in the same AS, so they're in the same confederation
+      if (initiatorLocalAs.equals(listenerLocalAs)) {
+        if (listenerRemoteAsns.contains(initiatorLocalAs)
+            && initiatorRemoteAsns.contains(listenerLocalAs)) {
+          return new AsPair(initiatorLocalAs, listenerLocalAs);
+        } else {
+          return null;
+        }
+      } else if (listenerRemoteAsns.contains(initiatorLocalAs)
           && initiatorRemoteAsns.contains(listenerConfed)) {
         return new AsPair(initiatorLocalAs, listenerConfed);
       }

diff --git a/...batfish-common-protocol/src/test/java/org/batfish/datamodel/bgp/BgpTopologyUtilsTest.java b/...batfish-common-protocol/src/test/java/org/batfish/datamodel/bgp/BgpTopologyUtilsTest.java
@@ -393,5 +393,11 @@ public void testComputeAsPair() {
     // Confed no match
     assertPair(1L, 3L, LongSpace.of(4), 4L, null, LongSpace.of(5), null);
     assertPair(1L, 3L, LongSpace.of(4), 4L, 9L, LongSpace.of(5), null);
+
+    // One peer implicitly matches other's confed, they shares same AS
+    assertPair(1L, 3L, LongSpace.of(1L), 1L, null, LongSpace.of(1L), new AsPair(1, 1));
+    // One peer implicitly matches other's confed, but remote ASN doesn't overlap local AS
+    assertPair(1L, 3L, LongSpace.of(2L), 1L, null, LongSpace.of(1L), null);
+    assertPair(1L, 3L, LongSpace.of(1L), 1L, null, LongSpace.of(2L), null);
   }
 }