BGP external announcements: Create a BGP session properties objects for import policy evaluation

projects/batfish-common-protocol/src/main/java/org/batfish/datamodel/routing_policy/RoutingPolicy.java

@@ -202,7 +202,7 @@ public List<Statement> getStatements() {
    */
   public boolean processReadOnly(AbstractRouteDecorator inputRoute) {
     // arbitrarily choose OUT direction, BGP route builder.
-    return process(inputRoute, Bgpv4Route.builder(), null, Direction.OUT, null);
+    return process(inputRoute, Bgpv4Route.builder(), (EigrpProcess) null, Direction.OUT, null);
   }
 
   /** @return True if the policy accepts the route. */

projects/batfish/src/main/java/org/batfish/dataplane/ibdp/BgpRoutingProcess.java

@@ -50,6 +50,7 @@
 import org.batfish.datamodel.AbstractRoute;
 import org.batfish.datamodel.AbstractRouteDecorator;
 import org.batfish.datamodel.AnnotatedRoute;
+import org.batfish.datamodel.BgpActivePeerConfig;
 import org.batfish.datamodel.BgpAdvertisement;
 import org.batfish.datamodel.BgpAdvertisement.BgpAdvertisementType;
 import org.batfish.datamodel.BgpPeerConfig;
@@ -1669,11 +1670,12 @@ Bgpv4Route exportNonBgpRouteToBgp(
     return transformedOutgoingRoute;
   }
 
-  private void processExternalBgpAdvertisement(
+  @VisibleForTesting
+  void processExternalBgpAdvertisement(
       BgpAdvertisement advert, Map<Bgpv4Rib, RibDelta.Builder<Bgpv4Route>> ribDeltas) {
     Ip srcIp = advert.getSrcIp();
     // TODO: support passive and unnumbered bgp connections
-    BgpPeerConfig neighbor = _process.getActiveNeighbors().get(srcIp);
+    BgpActivePeerConfig neighbor = _process.getActiveNeighbors().get(srcIp);
     assert neighbor != null; // invariant of being processed
 
     // Build a route based on the type of this advertisement
@@ -1752,20 +1754,23 @@ private void processExternalBgpAdvertisement(
                   transformedOutgoingRoute.getReceivedFromRouteReflectorClient())
               .setProtocol(targetProtocol)
               .setSrcProtocol(targetProtocol);
-      String importPolicyName = neighbor.getIpv4UnicastAddressFamily().getImportPolicy();
+      String ipv4ImportPolicyName = neighbor.getIpv4UnicastAddressFamily().getImportPolicy();
       // TODO: ensure there is always an import policy
 
       /*
        * CREATE INCOMING ROUTE
        */
       boolean acceptIncoming = true;
-      if (importPolicyName != null) {
-        RoutingPolicy importPolicy = _policies.get(importPolicyName).orElse(null);
-        if (importPolicy != null) {
-          // TODO Figure out whether transformedOutgoingRoute ought to have an annotation
+      if (ipv4ImportPolicyName != null) {
+        RoutingPolicy ipv4ImportPolicy = _policies.get(ipv4ImportPolicyName).orElse(null);
+        if (ipv4ImportPolicy != null) {
           acceptIncoming =
-              importPolicy.process(
-                  transformedOutgoingRoute, transformedIncomingRouteBuilder, IN, _ribExprEvaluator);
+              processExternalBgpAdvertisementImport(
+                  transformedOutgoingRoute,
+                  transformedIncomingRouteBuilder,
+                  neighbor,
+                  ipv4ImportPolicy,
+                  _ribExprEvaluator);
         }
       }
       if (acceptIncoming) {
@@ -1775,6 +1780,35 @@ private void processExternalBgpAdvertisement(
     }
   }
 
+  @VisibleForTesting
+  static boolean processExternalBgpAdvertisementImport(
+      Bgpv4Route inputRoute,
+      Bgpv4Route.Builder outputRouteBuilder,
+      BgpActivePeerConfig neighbor,
+      RoutingPolicy ipv4ImportPolicy,
+      RibExprEvaluator ribExprEvaluator) {
+    // concoct a minimal session properties object: helps with route map constructs like
+    // next-hop peer-address
+    BgpSessionProperties bgpSessionProperties =
+        (neighbor.getLocalAs() != null
+                && !neighbor.getRemoteAsns().isEmpty()
+                && neighbor.getLocalIp() != null
+                && neighbor.getPeerAddress() != null)
+            ? BgpSessionProperties.builder()
+                .setHeadAs(neighbor.getLocalAs())
+                .setTailAs(neighbor.getRemoteAsns().least())
+                .setHeadIp(neighbor.getLocalIp())
+                .setTailIp(neighbor.getPeerAddress())
+                .setAddressFamilies(
+                    ImmutableSet.of(Type.IPV4_UNICAST)) // the import policy is IPV4 itself
+                .build()
+            : null;
+
+    // TODO Figure out whether transformedOutgoingRoute ought to have an annotation
+    return ipv4ImportPolicy.processBgpRoute(
+        inputRoute, outputRouteBuilder, bgpSessionProperties, IN, ribExprEvaluator);
+  }
+
   /**
    * Identifies the given external advertisements for this node and saves them. They will be
    * processed at the start of the BGP computation.

projects/batfish/src/test/java/org/batfish/dataplane/ibdp/BgpRoutingProcessTest.java

@@ -13,6 +13,7 @@
 import static org.batfish.datamodel.matchers.BgpRouteMatchers.isBgpv4RouteThat;
 import static org.batfish.datamodel.vxlan.Layer2Vni.testBuilder;
 import static org.batfish.dataplane.ibdp.BgpRoutingProcess.initEvpnType3Route;
+import static org.batfish.dataplane.ibdp.BgpRoutingProcess.processExternalBgpAdvertisementImport;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.allOf;
 import static org.hamcrest.Matchers.contains;
@@ -73,11 +74,13 @@
 import org.batfish.datamodel.route.nh.NextHopInterface;
 import org.batfish.datamodel.route.nh.NextHopVrf;
 import org.batfish.datamodel.routing_policy.RoutingPolicy;
+import org.batfish.datamodel.routing_policy.expr.BgpPeerAddressNextHop;
 import org.batfish.datamodel.routing_policy.expr.DestinationNetwork;
 import org.batfish.datamodel.routing_policy.expr.ExplicitPrefixSet;
 import org.batfish.datamodel.routing_policy.expr.MatchPrefixSet;
 import org.batfish.datamodel.routing_policy.expr.MatchProtocol;
 import org.batfish.datamodel.routing_policy.statement.If;
+import org.batfish.datamodel.routing_policy.statement.SetNextHop;
 import org.batfish.datamodel.routing_policy.statement.Statements;
 import org.batfish.datamodel.vxlan.Layer2Vni;
 import org.batfish.dataplane.rib.Rib;
@@ -841,4 +844,44 @@ public void testInitBgpAggregateRoutesMustPassGenerationPolicy() {
     deltaAdverts.forEach(advert -> assertThat(advert.getReason(), equalTo(Reason.ADD)));
     return deltaAdverts;
   }
+
+  @Test
+  public void testProcessExternalBgpAdvertisementImport() {
+    Ip neighborIp = Ip.parse("1.1.1.1");
+
+    BgpActivePeerConfig peer =
+        BgpActivePeerConfig.builder()
+            .setLocalIp(Ip.parse("1.1.1.2"))
+            .setLocalAs(1L)
+            .setRemoteAs(2L)
+            .setPeerAddress(neighborIp)
+            .setIpv4UnicastAddressFamily(Ipv4UnicastAddressFamily.builder().build())
+            .build();
+
+    // Create a routing policy that sets next-hop peer-address, which relies on method under test
+    // having created a BGP session properties object
+    RoutingPolicy policy =
+        RoutingPolicy.builder()
+            .setOwner(_c)
+            .setName("policy")
+            .setStatements(
+                Collections.singletonList(new SetNextHop(BgpPeerAddressNextHop.getInstance())))
+            .build();
+
+    Bgpv4Route.Builder routeBuilder =
+        Bgpv4Route.builder()
+            .setNetwork(Prefix.ZERO)
+            .setOriginatorIp(neighborIp)
+            .setOriginType(OriginType.EGP)
+            .setProtocol(RoutingProtocol.BGP)
+            .setNextHopIp(Ip.parse("2.2.2.2"));
+
+    Bgpv4Route inputRoute = routeBuilder.build();
+    Bgpv4Route.Builder outputRouteBuilder = routeBuilder;
+
+    processExternalBgpAdvertisementImport(inputRoute, outputRouteBuilder, peer, policy, null);
+
+    // policy application will overwrite the next hop ip
+    assertThat(outputRouteBuilder.build().getNextHopIp(), equalTo(neighborIp));
+  }
 }