Merge pull request #12861 from opensourcerouting/fix/bgp_confederation_with_astype

bgpd: Confederation fixes with remote-as external/internal

bgpd/bgp_attr.c

@@ -1645,6 +1645,14 @@ static enum bgp_attr_parse_ret bgp_attr_aspath_check(struct peer *const peer,
 	 */
 	struct aspath *aspath;
 
+	/* Refresh peer's type. If we set e.g.: AS_EXTERNAL/AS_INTERNAL,
+	 * then peer->sort remains BGP_PEER_EBGP/IBGP, hence we need to
+	 * have an actual type before checking.
+	 * This is especially a case for BGP confederation peers, to avoid
+	 * receiving and treating AS_PATH as malformed.
+	 */
+	(void)peer_sort(peer);
+
 	/* Confederation sanity check. */
 	if ((peer->sort == BGP_PEER_CONFED
 	     && !aspath_left_confed_check(attr->aspath))
@@ -4295,8 +4303,22 @@ bgp_size_t bgp_packet_attribute(struct bgp *bgp, struct peer *peer,
 		aspath = aspath_delete_confed_seq(aspath);
 
 		if (CHECK_FLAG(bgp->config, BGP_CONFIG_CONFEDERATION)) {
+			/* A confed member, so we need to do the
+			 * AS_CONFED_SEQUENCE thing if it's outside a common
+			 * administration.
+			 * Configured confederation peers MUST be validated
+			 * under BGP_PEER_CONFED, but if we have configured
+			 * remote-as as AS_EXTERNAL, we need to check again
+			 * if the peer belongs to us.
+			 */
+			if (bgp_confederation_peers_check(bgp, peer->as)) {
+				aspath = aspath_dup(attr->aspath);
+				aspath = aspath_add_confed_seq(aspath,
+							       peer->local_as);
+			} else {
 				/* Stuff our path CONFED_ID on the front */
 				aspath = aspath_add_seq(aspath, bgp->confed_id);
+			}
 		} else {
 			if (peer->change_local_as) {
 				/* If replace-as is specified, we only use the

bgpd/bgpd.c

@@ -2041,9 +2041,9 @@ int peer_remote_as(struct bgp *bgp, union sockunion *su, const char *conf_if,
 
 		/* If the peer is not part of our confederation, and its not an
 		   iBGP peer then spoof the source AS */
-		if (bgp_config_check(bgp, BGP_CONFIG_CONFEDERATION)
-		    && !bgp_confederation_peers_check(bgp, *as)
-		    && bgp->as != *as)
+		if (bgp_config_check(bgp, BGP_CONFIG_CONFEDERATION) &&
+		    !bgp_confederation_peers_check(bgp, *as) && *as &&
+		    bgp->as != *as)
 			local_as = bgp->confed_id;
 		else
 			local_as = bgp->as;

tests/topotests/bgp_confederation_astype/r1/bgpd.conf

@@ -0,0 +1,12 @@
+router bgp 65001
+ no bgp ebgp-requires-policy
+ bgp confederation identifier 65300
+ bgp confederation peers 65002 65003
+ neighbor fabric peer-group
+ neighbor fabric remote-as external
+ neighbor 192.168.1.2 peer-group fabric
+ neighbor 192.168.2.2 remote-as external
+ address-family ipv4 unicast
+  neighbor fabric activate
+ exit-address-family
+!

tests/topotests/bgp_confederation_astype/r1/zebra.conf

@@ -0,0 +1,7 @@
+!
+int r1-eth0
+ ip address 192.168.1.1/24
+!
+int r1-eth1
+ ip address 192.168.2.1/24
+!

tests/topotests/bgp_confederation_astype/r2/bgpd.conf

@@ -0,0 +1,13 @@
+router bgp 65002
+ no bgp ebgp-requires-policy
+ no bgp network import-check
+ bgp confederation identifier 65300
+ bgp confederation peers 65001
+ neighbor fabric peer-group
+ neighbor fabric remote-as external
+ neighbor 192.168.1.1 peer-group fabric
+ address-family ipv4 unicast
+  network 172.16.255.254/32
+  neighbor fabric activate
+ exit-address-family
+!

tests/topotests/bgp_confederation_astype/r2/zebra.conf

@@ -0,0 +1,4 @@
+!
+int r2-eth0
+ ip address 192.168.1.2/24
+!

tests/topotests/bgp_confederation_astype/r3/bgpd.conf

@@ -0,0 +1,10 @@
+router bgp 65003
+ no bgp ebgp-requires-policy
+ no bgp network import-check
+ bgp confederation identifier 65300
+ bgp confederation peers 65001
+ neighbor 192.168.2.1 remote-as external
+ address-family ipv4 unicast
+  network 172.16.255.254/32
+ exit-address-family
+!

tests/topotests/bgp_confederation_astype/r3/zebra.conf

@@ -0,0 +1,4 @@
+!
+int r3-eth0
+ ip address 192.168.2.2/24
+!

tests/topotests/bgp_confederation_astype/test_bgp_confederation_astype.py

@@ -0,0 +1,140 @@
+#!/usr/bin/env python
+# SPDX-License-Identifier: ISC
+
+# Copyright (c) 2022 by
+# Donatas Abraitis <donatas@opensourcerouting.org>
+#
+
+"""
+Test if BGP confederation works properly when using
+remote-as internal/external.
+
+Also, check if the same works with peer-groups as well.
+"""
+
+import os
+import sys
+import json
+import pytest
+import functools
+
+pytestmark = pytest.mark.bgpd
+
+CWD = os.path.dirname(os.path.realpath(__file__))
+sys.path.append(os.path.join(CWD, "../"))
+
+# pylint: disable=C0413
+from lib import topotest
+from lib.topogen import Topogen, TopoRouter, get_topogen
+
+pytestmark = [pytest.mark.bgpd]
+
+
+def setup_module(mod):
+    topodef = {"s1": ("r1", "r2"), "s2": ("r1", "r3")}
+    tgen = Topogen(topodef, mod.__name__)
+    tgen.start_topology()
+
+    router_list = tgen.routers()
+
+    for i, (rname, router) in enumerate(router_list.items(), 1):
+        router.load_config(
+            TopoRouter.RD_ZEBRA, os.path.join(CWD, "{}/zebra.conf".format(rname))
+        )
+        router.load_config(
+            TopoRouter.RD_BGP, os.path.join(CWD, "{}/bgpd.conf".format(rname))
+        )
+
+    tgen.start_router()
+
+
+def teardown_module(mod):
+    tgen = get_topogen()
+    tgen.stop_topology()
+
+
+def test_bgp_confederation_astype():
+    tgen = get_topogen()
+
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    r1 = tgen.gears["r1"]
+
+    def _bgp_converge():
+        output = json.loads(r1.vtysh_cmd("show bgp summary json"))
+        expected = {
+            "ipv4Unicast": {
+                "peerCount": 2,
+                "peers": {
+                    "192.168.1.2": {
+                        "hostname": "r2",
+                        "remoteAs": 65002,
+                        "localAs": 65001,
+                        "pfxRcd": 1,
+                        "state": "Established",
+                    },
+                    "192.168.2.2": {
+                        "hostname": "r3",
+                        "remoteAs": 65003,
+                        "localAs": 65001,
+                        "pfxRcd": 1,
+                        "state": "Established",
+                    },
+                },
+            }
+        }
+        return topotest.json_cmp(output, expected)
+
+    test_func = functools.partial(_bgp_converge)
+    _, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
+    assert result is None, "Can't converge"
+
+    def _bgp_check_neighbors():
+        output = json.loads(r1.vtysh_cmd("show bgp neighbors json"))
+        expected = {
+            "192.168.1.2": {
+                "nbrCommonAdmin": True,
+                "nbrConfedExternalLink": True,
+                "hostname": "r2",
+            },
+            "192.168.2.2": {
+                "nbrCommonAdmin": True,
+                "nbrConfedExternalLink": True,
+                "hostname": "r3",
+            },
+        }
+        return topotest.json_cmp(output, expected)
+
+    test_func = functools.partial(_bgp_check_neighbors)
+    _, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
+    assert result is None, "Can't see neighbors to be in BGP confederation"
+
+    def _bgp_check_routes():
+        output = json.loads(r1.vtysh_cmd("show bgp ipv4 unicast json"))
+        expected = {
+            "routes": {
+                "172.16.255.254/32": [
+                    {
+                        "valid": True,
+                        "pathFrom": "external",
+                        "path": "(65003)",
+                    },
+                    {
+                        "valid": True,
+                        "pathFrom": "external",
+                        "path": "(65002)",
+                    },
+                ]
+            }
+        }
+        return topotest.json_cmp(output, expected)
+
+    test_func = functools.partial(_bgp_check_routes)
+    _, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
+    assert result is None, "Can't see routes to be in BGP confederation"
+
+
+if __name__ == "__main__":
+    args = ["-s"] + sys.argv[1:]
+    sys.exit(pytest.main(args))