bgpd: minimum-holdtime knob to prevent session establishment with BGP peer with low holdtime.

Signed-off-by: Takemasa Imada <takemasa.imada@gmail.com>

bgpd/bgp_packet.c

@@ -1353,6 +1353,16 @@ static int bgp_open_receive(struct peer *peer, bgp_size_t size)
 		return BGP_Stop;
 	}
 
+	/* Send notification message when Hold Time received in the OPEN message
+	 * is smaller than configured minimum Hold Time. */
+	if (holdtime < peer->bgp->default_min_holdtime
+	    && peer->bgp->default_min_holdtime != 0) {
+		bgp_notify_send_with_data(peer, BGP_NOTIFY_OPEN_ERR,
+					  BGP_NOTIFY_OPEN_UNACEP_HOLDTIME,
+					  (uint8_t *)holdtime_ptr, 2);
+		return BGP_Stop;
+	}
+
 	/* From the rfc: A reasonable maximum time between KEEPALIVE messages
 	   would be one third of the Hold Time interval.  KEEPALIVE messages
 	   MUST NOT be sent more frequently than one per second.  An

bgpd/bgp_vty.c

@@ -2332,6 +2332,38 @@ DEFUN (no_bgp_timers,
 	return CMD_SUCCESS;
 }
 
+/* BGP minimum holdtime.  */
+
+DEFUN(bgp_minimum_holdtime, bgp_minimum_holdtime_cmd,
+      "bgp minimum-holdtime (1-65535)",
+      "BGP specific commands\n"
+      "BGP minimum holdtime\n"
+      "Seconds\n")
+{
+	VTY_DECLVAR_CONTEXT(bgp, bgp);
+	int idx_number = 2;
+	unsigned long min_holdtime;
+
+	min_holdtime = strtoul(argv[idx_number]->arg, NULL, 10);
+
+	bgp->default_min_holdtime = min_holdtime;
+
+	return CMD_SUCCESS;
+}
+
+DEFUN(no_bgp_minimum_holdtime, no_bgp_minimum_holdtime_cmd,
+      "no bgp minimum-holdtime [(1-65535)]",
+      NO_STR
+      "BGP specific commands\n"
+      "BGP minimum holdtime\n"
+      "Seconds\n")
+{
+	VTY_DECLVAR_CONTEXT(bgp, bgp);
+
+	bgp->default_min_holdtime = 0;
+
+	return CMD_SUCCESS;
+}
 
 DEFUN (bgp_client_to_client_reflection,
        bgp_client_to_client_reflection_cmd,
@@ -17112,6 +17144,12 @@ int bgp_config_write(struct vty *vty)
 			vty_out(vty, " timers bgp %u %u\n",
 				bgp->default_keepalive, bgp->default_holdtime);
 
+		/* BGP minimum holdtime configuration. */
+		if (bgp->default_min_holdtime != SAVE_BGP_HOLDTIME
+		    && bgp->default_min_holdtime != 0)
+			vty_out(vty, " bgp minimum-holdtime %u\n",
+				bgp->default_min_holdtime);
+
 		/* Conditional advertisement timer configuration */
 		if (bgp->condition_check_period
 		    != DEFAULT_CONDITIONAL_ROUTES_POLL_TIME)
@@ -17506,6 +17544,10 @@ void bgp_vty_init(void)
 	install_element(BGP_NODE, &bgp_timers_cmd);
 	install_element(BGP_NODE, &no_bgp_timers_cmd);
 
+	/* "minimum-holdtime" commands. */
+	install_element(BGP_NODE, &bgp_minimum_holdtime_cmd);
+	install_element(BGP_NODE, &no_bgp_minimum_holdtime_cmd);
+
 	/* route-map delay-timer commands - per instance for backwards compat.
 	 */
 	install_element(BGP_NODE, &bgp_set_route_map_delay_timer_cmd);

bgpd/bgpd.c

@@ -3154,6 +3154,7 @@ static struct bgp *bgp_create(as_t *as, const char *name,
 	bgp->default_subgroup_pkt_queue_max =
 		BGP_DEFAULT_SUBGROUP_PKT_QUEUE_MAX;
 	bgp_timers_unset(bgp);
+	bgp->default_min_holdtime = 0;
 	bgp->restart_time = BGP_DEFAULT_RESTART_TIME;
 	bgp->stalepath_time = BGP_DEFAULT_STALEPATH_TIME;
 	bgp->select_defer_time = BGP_DEFAULT_SELECT_DEFERRAL_TIME;

bgpd/bgpd.h

@@ -602,6 +602,9 @@ struct bgp {
 	uint32_t default_connect_retry;
 	uint32_t default_delayopen;
 
+	/* BGP minimum holdtime.  */
+	uint16_t default_min_holdtime;
+
 	/* BGP graceful restart */
 	uint32_t restart_time;
 	uint32_t stalepath_time;

doc/user/bgp.rst

@@ -1693,6 +1693,12 @@ Configuring Peers
    default, the DelayOpenTimer is disabled. The timer interval may be set to a
    duration of 1 to 240 seconds.
 
+.. clicmd:: bgp minimum-holdtime (1-65535)
+
+   This command allows user to prevent session establishment with BGP peers
+   with lower holdtime less than configured minimum holdtime.
+   When this command is not set, minimum holdtime does not work.
+
 Displaying Information about Peers
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 

tests/topotests/bgp_minimum_holdtime/r1/bgpd.conf

@@ -0,0 +1,6 @@
+router bgp 65000
+  bgp minimum-holdtime 20
+  neighbor 192.168.255.2 remote-as 65001
+  neighbor 192.168.255.2 timers 3 10
+  neighbor 192.168.255.2 timers connect 10
+!

tests/topotests/bgp_minimum_holdtime/r1/zebra.conf

@@ -0,0 +1,6 @@
+!
+interface r1-eth0
+ ip address 192.168.255.1/24
+!
+ip forwarding
+!

tests/topotests/bgp_minimum_holdtime/r2/bgpd.conf

@@ -0,0 +1,5 @@
+router bgp 65001
+  no bgp ebgp-requires-policy
+  neighbor 192.168.255.1 remote-as 65000
+  neighbor 192.168.255.1 timers 3 10
+!

tests/topotests/bgp_minimum_holdtime/r2/zebra.conf

@@ -0,0 +1,6 @@
+!
+interface r2-eth0
+ ip address 192.168.255.2/24
+!
+ip forwarding
+!

tests/topotests/bgp_minimum_holdtime/test_bgp_minimum_holdtime.py

@@ -0,0 +1,104 @@
+#!/usr/bin/env python
+
+# Copyright (c) 2021 by
+# Takemasa Imada <takemasa.imada@gmail.com>
+#
+# 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.
+#
+
+"""
+Test if minimum-holdtime works.
+"""
+
+import os
+import sys
+import json
+import time
+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.topolog import logger
+from mininet.topo import Topo
+
+pytestmark = [pytest.mark.bgpd]
+
+
+class TemplateTopo(Topo):
+    def build(self, *_args, **_opts):
+        tgen = get_topogen(self)
+
+        for routern in range(1, 3):
+            tgen.add_router("r{}".format(routern))
+
+        switch = tgen.add_switch("s1")
+        switch.add_link(tgen.gears["r1"])
+        switch.add_link(tgen.gears["r2"])
+
+
+def setup_module(mod):
+    tgen = Topogen(TemplateTopo, 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_minimum_holdtime():
+    tgen = get_topogen()
+
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    def _bgp_neighbor_check_if_notification_sent():
+        output = json.loads(
+            tgen.gears["r1"].vtysh_cmd("show ip bgp neighbor 192.168.255.2 json")
+        )
+        expected = {
+            "192.168.255.2": {
+                "connectionsEstablished": 0,
+                "lastNotificationReason": "OPEN Message Error/Unacceptable Hold Time",
+                "lastResetDueTo": "BGP Notification send",
+            }
+        }
+        return topotest.json_cmp(output, expected)
+
+    test_func = functools.partial(_bgp_neighbor_check_if_notification_sent)
+    success, result = topotest.run_and_expect(test_func, None, count=40, wait=0.5)
+    assert result is None, "Failed to send notification message\n"
+
+
+if __name__ == "__main__":
+    args = ["-s"] + sys.argv[1:]
+    sys.exit(pytest.main(args))