_ebgpv4Rib and _bgpv4Rib of BgpRoutingProcess process two equal-cost EBGP routes differently when multipathIbgp enabled but multipathEbgp disabled

[heroinedd]

Hi, I notice a possible bug of Batfish. That is, when a BgpProcess is multipathIbgp enabled but multipathEbgp disabled (implying multipath enabled, since multipath = multipathIbgp || multipathEbgp), given two equal-cost EBGP routes LEARNED from neighbors, the corresponding BgpRoutingProcess's _ebgpv4Rib will insert only one of them into its RibTree since it is multipath disabled, while its _bgpv4Rib will insert both of the routes into its RibTree since it is multipath enabled.

You can use the following code to find the inconsistency:

    // set up
    NetworkFactory nf = new NetworkFactory();
    Configuration c =
        nf.configurationBuilder()
            .setConfigurationFormat(ConfigurationFormat.CISCO_IOS)
            .setHostname("c1")
            .build();
    Vrf vrf = nf.vrfBuilder().setOwner(c).setName(DEFAULT_VRF_NAME).build();
    BgpProcess bgpProcess = BgpProcess.testBgpProcess(Ip.ZERO);
    bgpProcess.setMultipathIbgp(true);
    bgpProcess.setMultipathEbgp(false);
    vrf.setBgpProcess(bgpProcess);
    Rib mainRib = new Rib();
    mainRib.mergeRouteGetDelta(
        new AnnotatedRoute<>(
            StaticRoute.testBuilder().setNetwork(Prefix.parse("70.0.0.0/24")).build(),
            DEFAULT_VRF_NAME));
    mainRib.mergeRouteGetDelta(
        new AnnotatedRoute<>(
            StaticRoute.testBuilder().setNetwork(Prefix.parse("60.0.0.0/24")).build(),
            DEFAULT_VRF_NAME));

    BgpRoutingProcess routingProcess =
        new BgpRoutingProcess(
            bgpProcess, c, DEFAULT_VRF_NAME, mainRib, BgpTopology.EMPTY, new PrefixTracer());

    // init two equal-cost EBGP routes learned from neighbors
    Prefix pfx = Prefix.parse("10.0.1.0/24");
    Bgpv4Route r1 =
        Bgpv4Route.testBuilder()
            .setNetwork(pfx)
            .setNextHopIp(Ip.parse("70.0.0.1"))
            .setOriginMechanism(OriginMechanism.LEARNED)
            .setReceivedFrom(ReceivedFromIp.of(Ip.parse("70.0.0.1")))
            .build();
    Bgpv4Route r2 =
        Bgpv4Route.testBuilder()
            .setNetwork(pfx)
            .setNextHopIp(Ip.parse("60.0.0.1"))
            .setOriginMechanism(OriginMechanism.LEARNED)
            .setReceivedFrom(ReceivedFromIp.of(Ip.parse("60.0.0.1")))
            .build();

    // insert r1 into _bgpv4Rib and _ebgpv4Rib, the test will success
    routingProcess._bgpv4Rib.mergeRouteGetDelta(r1);
    routingProcess._ebgpv4Rib.mergeRouteGetDelta(r1);
    assertEquals(routingProcess._bgpv4Rib.getRoutes(pfx), routingProcess._ebgpv4Rib.getRoutes(pfx));

    // insert r2 into _bgpv4Rib and _ebgpv4Rib, the test will fail
    routingProcess._bgpv4Rib.mergeRouteGetDelta(r2);
    routingProcess._ebgpv4Rib.mergeRouteGetDelta(r2);
    assertEquals(routingProcess._bgpv4Rib.getRoutes(pfx), routingProcess._ebgpv4Rib.getRoutes(pfx));

[dhalperi]

Hi Dan, the tl;dr is we don’t support mixing multipath and non-multipath modes, so this is an unsupported use case. I’m sure that Ari can say more. From: dan wang ***@***.***> Reply-To: batfish/batfish ***@***.***> Date: Sunday, April 14, 2024 at 3:33 AM To: batfish/batfish ***@***.***> Cc: Subscribed ***@***.***> Subject: [batfish/batfish] _ebgpv4Rib and _bgpv4Rib of BgpRoutingProcess process two equal-cost EBGP routes differently when multipathIbgp enabled but multipathEbgp disabled (Issue #8990) Hi, I notice a possible bug of Batfish. That is, when a BgpProcess is multipathIbgp enabled but multipathEbgp disabled (implying multipath enabled, since multipath = multipathIbgp || multipathEbgp<https://github.com/batfish/batfish/blob/ab258be3c5d31649d9d2ffa9761bd06963339d42/projects/batfish/src/main/java/org/batfish/dataplane/ibdp/BgpRoutingProcess.java#L440>), given two equal-cost EBGP routes LEARNED<https://github.com/batfish/batfish/blob/ab258be3c5d31649d9d2ffa9761bd06963339d42/projects/batfish-common-protocol/src/main/java/org/batfish/datamodel/OriginMechanism.java#L11> from neighbors, the corresponding BgpRoutingProcess's _ebgpv4Rib will insert only one of them into its RibTree since it is multipath disabled, while its _bgpv4Rib will insert both of the routes into its RibTree since it is multipath enabled. You can use the following code to find the inconsistency: // set up NetworkFactory nf = new NetworkFactory(); Configuration c = nf.configurationBuilder() .setConfigurationFormat(ConfigurationFormat.CISCO_IOS) .setHostname("c1") .build(); Vrf vrf = nf.vrfBuilder().setOwner(c).setName(DEFAULT_VRF_NAME).build(); BgpProcess bgpProcess = BgpProcess.testBgpProcess(Ip.ZERO); bgpProcess.setMultipathIbgp(true); bgpProcess.setMultipathEbgp(false); vrf.setBgpProcess(bgpProcess); Rib mainRib = new Rib(); mainRib.mergeRouteGetDelta( new AnnotatedRoute<>( StaticRoute.testBuilder().setNetwork(Prefix.parse("70.0.0.0/24")).build(), DEFAULT_VRF_NAME)); mainRib.mergeRouteGetDelta( new AnnotatedRoute<>( StaticRoute.testBuilder().setNetwork(Prefix.parse("60.0.0.0/24")).build(), DEFAULT_VRF_NAME)); BgpRoutingProcess routingProcess = new BgpRoutingProcess( bgpProcess, c, DEFAULT_VRF_NAME, mainRib, BgpTopology.EMPTY, new PrefixTracer()); // init two equal-cost EBGP routes learned from neighbors Prefix pfx = Prefix.parse("10.0.1.0/24"); Bgpv4Route r1 = Bgpv4Route.testBuilder() .setNetwork(pfx) .setNextHopIp(Ip.parse("70.0.0.1")) .setOriginMechanism(OriginMechanism.LEARNED) .setReceivedFrom(ReceivedFromIp.of(Ip.parse("70.0.0.1"))) .build(); Bgpv4Route r2 = Bgpv4Route.testBuilder() .setNetwork(pfx) .setNextHopIp(Ip.parse("60.0.0.1")) .setOriginMechanism(OriginMechanism.LEARNED) .setReceivedFrom(ReceivedFromIp.of(Ip.parse("60.0.0.1"))) .build(); // insert r1 into _bgpv4Rib and _ebgpv4Rib, the test will success routingProcess._bgpv4Rib.mergeRouteGetDelta(r1); routingProcess._ebgpv4Rib.mergeRouteGetDelta(r1); assertEquals(routingProcess._bgpv4Rib.getRoutes(pfx), routingProcess._ebgpv4Rib.getRoutes(pfx)); // insert r2 into _bgpv4Rib and _ebgpv4Rib, the test will fail routingProcess._bgpv4Rib.mergeRouteGetDelta(r2); routingProcess._ebgpv4Rib.mergeRouteGetDelta(r2); assertEquals(routingProcess._bgpv4Rib.getRoutes(pfx), routingProcess._ebgpv4Rib.getRoutes(pfx)); — Reply to this email directly, view it on GitHub<#8990>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/AAEAQT4KJXSWPTUO2JW7FLDY5JLMJAVCNFSM6AAAAABGGDLXUGVHI2DSMVQWIX3LMV43ASLTON2WKOZSGI2DEMBYHA3TOMQ>. You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>