Merge pull request #16816 from opensourcerouting/feature/bgp_dual_as

bgpd: Implement BGP dual-as feature

bgpd/bgp_packet.c

@@ -2702,6 +2702,19 @@ static int bgp_notify_receive(struct peer_connection *connection,
 	    inner.subcode == BGP_NOTIFY_OPEN_UNSUP_PARAM)
 		UNSET_FLAG(peer->sflags, PEER_STATUS_CAPABILITY_OPEN);
 
+	/* Resend the next OPEN message with a global AS number if we received
+	 * a `Bad Peer AS` notification. This is only valid if `dual-as` is
+	 * configured.
+	 */
+	if (inner.code == BGP_NOTIFY_OPEN_ERR &&
+	    inner.subcode == BGP_NOTIFY_OPEN_BAD_PEER_AS &&
+	    CHECK_FLAG(peer->flags, PEER_FLAG_DUAL_AS)) {
+		if (peer->change_local_as != peer->bgp->as)
+			peer->change_local_as = peer->bgp->as;
+		else
+			peer->change_local_as = peer->local_as;
+	}
+
 	/* If Graceful-Restart N-bit (Notification) is exchanged,
 	 * and it's not a Hard Reset, let's retain the routes.
 	 */

bgpd/bgp_updgrp.c

@@ -783,8 +783,11 @@ static int update_group_show_walkcb(struct update_group *updgrp, void *arg)
 				json_updgrp, "replaceLocalAs",
 				CHECK_FLAG(updgrp->conf->flags,
 					   PEER_FLAG_LOCAL_AS_REPLACE_AS));
+			json_object_boolean_add(json_updgrp, "dualAs",
+						CHECK_FLAG(updgrp->conf->flags,
+							   PEER_FLAG_DUAL_AS));
 		} else {
-			vty_out(vty, "  Local AS %u%s%s\n",
+			vty_out(vty, "  Local AS %u%s%s%s\n",
 				updgrp->conf->change_local_as,
 				CHECK_FLAG(updgrp->conf->flags,
 					   PEER_FLAG_LOCAL_AS_NO_PREPEND)
@@ -793,6 +796,10 @@ static int update_group_show_walkcb(struct update_group *updgrp, void *arg)
 				CHECK_FLAG(updgrp->conf->flags,
 					   PEER_FLAG_LOCAL_AS_REPLACE_AS)
 					? " replace-as"
+					: "",
+				CHECK_FLAG(updgrp->conf->flags,
+					   PEER_FLAG_DUAL_AS)
+					? " dual-as"
 					: "");
 		}
 	}

bgpd/bgp_vty.c

@@ -5451,7 +5451,7 @@ DEFUN (neighbor_local_as,
 		return CMD_WARNING_CONFIG_FAILED;
 	}
 
-	ret = peer_local_as_set(peer, as, 0, 0, argv[idx_number]->arg);
+	ret = peer_local_as_set(peer, as, 0, 0, 0, argv[idx_number]->arg);
 	return bgp_vty_return(vty, ret);
 }
 
@@ -5480,19 +5480,20 @@ DEFUN (neighbor_local_as_no_prepend,
 		return CMD_WARNING_CONFIG_FAILED;
 	}
 
-	ret = peer_local_as_set(peer, as, 1, 0, argv[idx_number]->arg);
+	ret = peer_local_as_set(peer, as, 1, 0, 0, argv[idx_number]->arg);
 	return bgp_vty_return(vty, ret);
 }
 
-DEFUN (neighbor_local_as_no_prepend_replace_as,
+DEFPY (neighbor_local_as_no_prepend_replace_as,
        neighbor_local_as_no_prepend_replace_as_cmd,
-       "neighbor <A.B.C.D|X:X::X:X|WORD> local-as ASNUM no-prepend replace-as",
+       "neighbor <A.B.C.D|X:X::X:X|WORD> local-as ASNUM no-prepend replace-as [dual-as$dual_as]",
        NEIGHBOR_STR
        NEIGHBOR_ADDR_STR2
        "Specify a local-as number\n"
        "AS number expressed in dotted or plain format used as local AS\n"
        "Do not prepend local-as to updates from ebgp peers\n"
-       "Do not prepend local-as to updates from ibgp peers\n")
+       "Do not prepend local-as to updates from ibgp peers\n"
+       "Allow peering with a global AS number or local-as number\n")
 {
 	int idx_peer = 1;
 	int idx_number = 3;
@@ -5510,20 +5511,21 @@ DEFUN (neighbor_local_as_no_prepend_replace_as,
 		return CMD_WARNING_CONFIG_FAILED;
 	}
 
-	ret = peer_local_as_set(peer, as, 1, 1, argv[idx_number]->arg);
+	ret = peer_local_as_set(peer, as, 1, 1, dual_as, argv[idx_number]->arg);
 	return bgp_vty_return(vty, ret);
 }
 
 DEFUN (no_neighbor_local_as,
        no_neighbor_local_as_cmd,
-       "no neighbor <A.B.C.D|X:X::X:X|WORD> local-as [ASNUM [no-prepend [replace-as]]]",
+       "no neighbor <A.B.C.D|X:X::X:X|WORD> local-as [ASNUM [no-prepend [replace-as] [dual-as]]]",
        NO_STR
        NEIGHBOR_STR
        NEIGHBOR_ADDR_STR2
        "Specify a local-as number\n"
        "AS number expressed in dotted or plain format used as local AS\n"
        "Do not prepend local-as to updates from ebgp peers\n"
-       "Do not prepend local-as to updates from ibgp peers\n")
+       "Do not prepend local-as to updates from ibgp peers\n"
+       "Allow peering with a global AS number or local-as number\n")
 {
 	int idx_peer = 2;
 	struct peer *peer;
@@ -14051,6 +14053,10 @@ static void bgp_show_peer(struct vty *vty, struct peer *p, bool use_json,
 		if (CHECK_FLAG(p->flags, PEER_FLAG_LOCAL_AS_REPLACE_AS))
 			json_object_boolean_true_add(json_neigh,
 						     "localAsReplaceAs");
+
+		json_object_boolean_add(json_neigh, "localAsReplaceAsDualAs",
+					!!CHECK_FLAG(p->flags,
+						     PEER_FLAG_DUAL_AS));
 	} else {
 		if (p->as_type == AS_SPECIFIED ||
 		    CHECK_FLAG(p->as_type, AS_AUTO) ||
@@ -14065,12 +14071,14 @@ static void bgp_show_peer(struct vty *vty, struct peer *p, bool use_json,
 		vty_out(vty, ASN_FORMAT(bgp->asnotation),
 			p->change_local_as ? &p->change_local_as
 					   : &p->local_as);
-		vty_out(vty, "%s%s, ",
+		vty_out(vty, "%s%s%s, ",
 			CHECK_FLAG(p->flags, PEER_FLAG_LOCAL_AS_NO_PREPEND)
 				? " no-prepend"
 				: "",
 			CHECK_FLAG(p->flags, PEER_FLAG_LOCAL_AS_REPLACE_AS)
 				? " replace-as"
+				: "",
+			CHECK_FLAG(p->flags, PEER_FLAG_DUAL_AS) ? " dual-as"
 								: "");
 	}
 	/* peer type internal or confed-internal */
@@ -18663,6 +18671,8 @@ static void bgp_config_write_peer_global(struct vty *vty, struct bgp *bgp,
 			vty_out(vty, " no-prepend");
 		if (peergroup_flag_check(peer, PEER_FLAG_LOCAL_AS_REPLACE_AS))
 			vty_out(vty, " replace-as");
+		if (peergroup_flag_check(peer, PEER_FLAG_DUAL_AS))
+			vty_out(vty, " dual-as");
 		vty_out(vty, "\n");
 	}
 

bgpd/bgpd.c

@@ -4696,6 +4696,7 @@ static const struct peer_flag_action peer_flag_action_list[] = {
 	{PEER_FLAG_LOCAL_AS, 0, peer_change_reset},
 	{PEER_FLAG_LOCAL_AS_NO_PREPEND, 0, peer_change_reset},
 	{PEER_FLAG_LOCAL_AS_REPLACE_AS, 0, peer_change_reset},
+	{PEER_FLAG_DUAL_AS, 0, peer_change_reset},
 	{PEER_FLAG_UPDATE_SOURCE, 0, peer_change_none},
 	{PEER_FLAG_DISABLE_LINK_BW_ENCODING_IEEE, 0, peer_change_none},
 	{PEER_FLAG_EXTENDED_OPT_PARAMS, 0, peer_change_reset},
@@ -6646,9 +6647,9 @@ int peer_allowas_in_unset(struct peer *peer, afi_t afi, safi_t safi)
 }
 
 int peer_local_as_set(struct peer *peer, as_t as, bool no_prepend,
-		      bool replace_as, const char *as_str)
+		      bool replace_as, bool dual_as, const char *as_str)
 {
-	bool old_no_prepend, old_replace_as;
+	bool old_no_prepend, old_replace_as, old_dual_as;
 	struct bgp *bgp = peer->bgp;
 	struct peer *member;
 	struct listnode *node, *nnode;
@@ -6661,14 +6662,16 @@ int peer_local_as_set(struct peer *peer, as_t as, bool no_prepend,
 		!!CHECK_FLAG(peer->flags, PEER_FLAG_LOCAL_AS_NO_PREPEND);
 	old_replace_as =
 		!!CHECK_FLAG(peer->flags, PEER_FLAG_LOCAL_AS_REPLACE_AS);
+	old_dual_as = !!CHECK_FLAG(peer->flags, PEER_FLAG_DUAL_AS);
 
 	/* Set flag and configuration on peer. */
 	peer_flag_set(peer, PEER_FLAG_LOCAL_AS);
 	peer_flag_modify(peer, PEER_FLAG_LOCAL_AS_NO_PREPEND, no_prepend);
 	peer_flag_modify(peer, PEER_FLAG_LOCAL_AS_REPLACE_AS, replace_as);
+	peer_flag_modify(peer, PEER_FLAG_DUAL_AS, dual_as);
 
-	if (peer->change_local_as == as && old_no_prepend == no_prepend
+	if (peer->change_local_as == as && old_no_prepend == no_prepend &&
-	    && old_replace_as == replace_as)
+	    old_replace_as == replace_as && old_dual_as == dual_as)
 		return 0;
 	peer->change_local_as = as;
 	if (as_str) {
@@ -6697,10 +6700,11 @@ int peer_local_as_set(struct peer *peer, as_t as, bool no_prepend,
 					    PEER_FLAG_LOCAL_AS_NO_PREPEND);
 		old_replace_as = CHECK_FLAG(member->flags,
 					    PEER_FLAG_LOCAL_AS_REPLACE_AS);
-		if (member->change_local_as == as
+		old_dual_as = !!CHECK_FLAG(member->flags, PEER_FLAG_DUAL_AS);
-		    && CHECK_FLAG(member->flags, PEER_FLAG_LOCAL_AS)
+		if (member->change_local_as == as &&
-		    && old_no_prepend == no_prepend
+		    CHECK_FLAG(member->flags, PEER_FLAG_LOCAL_AS) &&
-		    && old_replace_as == replace_as)
+		    old_no_prepend == no_prepend &&
+		    old_replace_as == replace_as && old_dual_as == dual_as)
 			continue;
 
 		/* Set flag and configuration on peer-group member. */
@@ -6709,6 +6713,7 @@ int peer_local_as_set(struct peer *peer, as_t as, bool no_prepend,
 			  no_prepend);
 		COND_FLAG(member->flags, PEER_FLAG_LOCAL_AS_REPLACE_AS,
 			  replace_as);
+		COND_FLAG(member->flags, PEER_FLAG_DUAL_AS, dual_as);
 		member->change_local_as = as;
 		if (as_str)
 			member->change_local_as_pretty = XSTRDUP(MTYPE_BGP_NAME,
@@ -6731,12 +6736,14 @@ int peer_local_as_unset(struct peer *peer)
 		peer_flag_inherit(peer, PEER_FLAG_LOCAL_AS);
 		peer_flag_inherit(peer, PEER_FLAG_LOCAL_AS_NO_PREPEND);
 		peer_flag_inherit(peer, PEER_FLAG_LOCAL_AS_REPLACE_AS);
+		peer_flag_inherit(peer, PEER_FLAG_DUAL_AS);
 		PEER_ATTR_INHERIT(peer, peer->group, change_local_as);
 	} else {
 		/* Otherwise remove flag and configuration from peer. */
 		peer_flag_unset(peer, PEER_FLAG_LOCAL_AS);
 		peer_flag_unset(peer, PEER_FLAG_LOCAL_AS_NO_PREPEND);
 		peer_flag_unset(peer, PEER_FLAG_LOCAL_AS_REPLACE_AS);
+		peer_flag_unset(peer, PEER_FLAG_DUAL_AS);
 		peer->change_local_as = 0;
 		XFREE(MTYPE_BGP_NAME, peer->change_local_as_pretty);
 	}
@@ -6768,6 +6775,7 @@ int peer_local_as_unset(struct peer *peer)
 		UNSET_FLAG(member->flags, PEER_FLAG_LOCAL_AS);
 		UNSET_FLAG(member->flags, PEER_FLAG_LOCAL_AS_NO_PREPEND);
 		UNSET_FLAG(member->flags, PEER_FLAG_LOCAL_AS_REPLACE_AS);
+		UNSET_FLAG(member->flags, PEER_FLAG_DUAL_AS);
 		member->change_local_as = 0;
 		XFREE(MTYPE_BGP_NAME, member->change_local_as_pretty);
 		member->last_reset = PEER_DOWN_LOCAL_AS_CHANGE;

bgpd/bgpd.h

@@ -1507,6 +1507,7 @@ struct peer {
 #define PEER_FLAG_CAPABILITY_FQDN (1ULL << 37)  /* fqdn capability */
 #define PEER_FLAG_AS_LOOP_DETECTION (1ULL << 38) /* as path loop detection */
 #define PEER_FLAG_EXTENDED_LINK_BANDWIDTH (1ULL << 39)
+#define PEER_FLAG_DUAL_AS		  (1ULL << 40)
 
 	/*
 	 *GR-Disabled mode means unset PEER_FLAG_GRACEFUL_RESTART
@@ -2443,7 +2444,7 @@ extern int peer_allowas_in_set(struct peer *, afi_t, safi_t, int, int);
 extern int peer_allowas_in_unset(struct peer *, afi_t, safi_t);
 
 extern int peer_local_as_set(struct peer *peer, as_t as, bool no_prepend,
-			     bool replace_as, const char *as_str);
+			     bool replace_as, bool dual_as, const char *as_str);
 extern int peer_local_as_unset(struct peer *);
 
 extern int peer_prefix_list_set(struct peer *, afi_t, safi_t, int,

doc/user/bgp.rst

@@ -1818,7 +1818,7 @@ Configuring Peers
    Since sent prefix count is managed by update-groups, this option
    creates a separate update-group for outgoing updates.
 
-.. clicmd:: neighbor PEER local-as AS-NUMBER [no-prepend] [replace-as]
+.. clicmd:: neighbor PEER local-as AS-NUMBER [no-prepend [replace-as [dual-as]]]
 
    Specify an alternate AS for this BGP process when interacting with the
    specified peer. With no modifiers, the specified local-as is prepended to
@@ -1834,6 +1834,10 @@ Configuring Peers
 
    Note that replace-as can only be specified if no-prepend is.
 
+   The ``dual-as`` keyword is used to configure the neighbor to establish a peering
+   session using the real autonomous-system number (``router bgp ASN``) or by using
+   the autonomous system number configured with the ``local-as``.
+
    This command is only allowed for eBGP peers.
 
 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> as-override

tests/topotests/bgp_dual_as/r1/frr.conf

@@ -0,0 +1,11 @@
+!
+interface r1-eth0
+ ip address 10.0.0.1/24
+!
+router bgp 65000
+ no bgp ebgp-requires-policy
+ neighbor 10.0.0.2 remote-as 65002
+ neighbor 10.0.0.2 local-as 65001 no-prepend replace-as dual-as
+ neighbor 10.0.0.2 timers 3 10
+ neighbor 10.0.0.2 timers connect 1
+!

tests/topotests/bgp_dual_as/r2/frr.conf

@@ -0,0 +1,10 @@
+!
+interface r2-eth0
+ ip address 10.0.0.2/24
+!
+router bgp 65002
+ no bgp ebgp-requires-policy
+ neighbor 10.0.0.1 remote-as 65001
+ neighbor 10.0.0.1 timers 3 10
+ neighbor 10.0.0.1 timers connect 1
+!

tests/topotests/bgp_dual_as/test_bgp_dual_as.py

@@ -0,0 +1,124 @@
+#!/usr/bin/env python
+# SPDX-License-Identifier: ISC
+
+#
+# Copyright (c) 2024 by
+# Donatas Abraitis <donatas@opensourcerouting.org>
+#
+
+import os
+import sys
+import json
+import pytest
+import functools
+
+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, get_topogen
+from lib.common_config import step
+
+pytestmark = [pytest.mark.bgpd]
+
+
+def build_topo(tgen):
+    r1 = tgen.add_router("r1")
+    r2 = tgen.add_router("r2")
+
+    switch = tgen.add_switch("s1")
+    switch.add_link(r1)
+    switch.add_link(r2)
+
+
+def setup_module(mod):
+    tgen = Topogen(build_topo, mod.__name__)
+    tgen.start_topology()
+
+    for _, (rname, router) in enumerate(tgen.routers().items(), 1):
+        router.load_frr_config(os.path.join(CWD, "{}/frr.conf".format(rname)))
+
+    tgen.start_router()
+
+
+def teardown_module(mod):
+    tgen = get_topogen()
+    tgen.stop_topology()
+
+
+def test_bgp_dual_as():
+    tgen = get_topogen()
+
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    r1 = tgen.gears["r1"]
+    r2 = tgen.gears["r2"]
+
+    def _bgp_converge_65001():
+        output = json.loads(r1.vtysh_cmd("show bgp ipv4 summary json"))
+        expected = {
+            "ipv4Unicast": {
+                "as": 65000,
+                "peers": {
+                    "10.0.0.2": {
+                        "hostname": "r2",
+                        "remoteAs": 65002,
+                        "localAs": 65001,
+                        "state": "Established",
+                        "peerState": "OK",
+                    }
+                },
+            }
+        }
+        return topotest.json_cmp(output, expected)
+
+    test_func = functools.partial(_bgp_converge_65001)
+    _, result = topotest.run_and_expect(test_func, None, count=30, wait=1)
+    assert result is None, "Can't establish BGP session using local-as AS 65001"
+
+    step("Change remote-as from r2 to use global AS 65000")
+    r2.vtysh_cmd(
+        """
+    configure terminal
+     router bgp
+      neighbor 10.0.0.1 remote-as 65000
+    """
+    )
+
+    def _bgp_converge_65000():
+        output = json.loads(r1.vtysh_cmd("show bgp ipv4 summary json"))
+        expected = {
+            "ipv4Unicast": {
+                "as": 65000,
+                "peers": {
+                    "10.0.0.2": {
+                        "hostname": "r2",
+                        "remoteAs": 65002,
+                        "localAs": 65000,
+                        "state": "Established",
+                        "peerState": "OK",
+                    }
+                },
+            }
+        }
+        return topotest.json_cmp(output, expected)
+
+    test_func = functools.partial(_bgp_converge_65000)
+    _, result = topotest.run_and_expect(test_func, None, count=30, wait=1)
+    assert result is None, "Can't establish BGP session using global AS 65000"
+
+
+def test_memory_leak():
+    "Run the memory leak test and report results."
+    tgen = get_topogen()
+    if not tgen.is_memleak_enabled():
+        pytest.skip("Memory leak test/report is disabled")
+
+    tgen.report_memory_leaks()
+
+
+if __name__ == "__main__":
+    args = ["-s"] + sys.argv[1:]
+    sys.exit(pytest.main(args))