pytest: add test for connection ratelimiting.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

connectd/connectd.c

@@ -1607,7 +1607,7 @@ static void connect_init(struct daemon *daemon, const u8 *msg)
 	enum addr_listen_announce *proposed_listen_announce;
 	struct wireaddr *announceable;
 	char *tor_password;
-	bool dev_disconnect, dev_throttle_gossip;
+	bool dev_disconnect, dev_throttle_gossip, dev_limit_connections_inflight;
 	char *errstr;
 
 	/* Fields which require allocation are allocated off daemon */
@@ -1631,7 +1631,8 @@ static void connect_init(struct daemon *daemon, const u8 *msg)
 				    &daemon->dev_handshake_no_reply,
 				    &dev_throttle_gossip,
 				    &daemon->dev_no_reconnect,
-				    &daemon->dev_fast_reconnect)) {
+				    &daemon->dev_fast_reconnect,
+				    &dev_limit_connections_inflight)) {
 		/* This is a helper which prints the type expected and the actual
 		 * message, then exits (it should never be called!). */
 		master_badmsg(WIRE_CONNECTD_INIT, msg);
@@ -1702,6 +1703,9 @@ static void connect_init(struct daemon *daemon, const u8 *msg)
 	if (dev_throttle_gossip)
 		daemon->gossip_stream_limit = 500;
 
+	if (dev_limit_connections_inflight)
+		daemon->max_connect_in_flight = 1;
+
 	/* Does nothing (no peers yet!) but arms timer */
 	release_one_connection_from_timer(daemon);
 }
@@ -1912,7 +1916,8 @@ static void try_connect_peer(struct daemon *daemon,
 
 	/* We wait for another to be destroyed if too many are in
 	 * progress (useful for startup of large nodes) */
-	connect->waiting = (connecting_htable_count(daemon->connecting) > 10);
+	connect->waiting = (connecting_htable_count(daemon->connecting)
+			    > daemon->max_connect_in_flight);
 	if (connect->waiting)
 		status_peer_debug(id, "Too many connections, waiting...");
 	else
@@ -2516,6 +2521,7 @@ int main(int argc, char *argv[])
 	timers_init(&daemon->timers, time_mono());
 	daemon->gossmap_raw = NULL;
 	daemon->shutting_down = false;
+	daemon->max_connect_in_flight = 10;
 	daemon->dev_suppress_gossip = false;
 	daemon->custom_msgs = NULL;
 	daemon->dev_exhausted_fds = false;

connectd/connectd.h

@@ -327,6 +327,10 @@ struct daemon {
 	/* Timer which releases one pending connection per second. */
 	struct oneshot *connect_release_timer;
 
+	/* How many connection attempts do we allow at once
+	 * (--dev-limit-connectsion-inflight sets this to 1 for testing). */
+	size_t max_connect_in_flight;
+
 	/* Hack to speed up gossip timer */
 	bool dev_fast_gossip;
 	/* Hack to avoid ping timeouts */

connectd/connectd_wire.csv

@@ -30,6 +30,7 @@ msgdata,connectd_init,dev_noreply,bool,
 msgdata,connectd_init,dev_throttle_gossip,bool,
 msgdata,connectd_init,dev_no_reconnect,bool,
 msgdata,connectd_init,dev_fast_reconnect,bool,
+msgdata,connectd_init,dev_limit_connections_inflight,bool,
 
 # Connectd->master, here are the addresses I bound, can announce.
 msgtype,connectd_init_reply,2100

lightningd/connect_control.c

@@ -607,7 +607,8 @@ int connectd_init(struct lightningd *ld)
 				   ld->dev_handshake_no_reply,
 				   ld->dev_throttle_gossip,
 				   !ld->reconnect,
-				   ld->dev_fast_reconnect);
+				   ld->dev_fast_reconnect,
+				   ld->dev_limit_connections_inflight);
 
 	subd_req(ld->connectd, ld->connectd, take(msg), -1, 0,
 		 connect_init_done, NULL);

lightningd/lightningd.c

@@ -151,6 +151,7 @@ static struct lightningd *new_lightningd(const tal_t *ctx)
 	ld->dev_hsmd_no_preapprove_check = false;
 	ld->dev_hsmd_fail_preapprove = false;
 	ld->dev_handshake_no_reply = false;
+	ld->dev_limit_connections_inflight = false;
 
 	/*~ We try to ensure enough fds for twice the number of channels
 	 * we start with.  We have a developer option to change that factor

lightningd/lightningd.h

@@ -357,6 +357,9 @@ struct lightningd {
 	/* Tell connectd not to talk after handshake */
 	bool dev_handshake_no_reply;
 
+	/* Tell connectd to block more than 1 simultanous connection attempt */
+	bool dev_limit_connections_inflight;
+
 	/* tor support */
 	struct wireaddr *proxyaddr;
 	bool always_use_proxy;

lightningd/options.c

@@ -960,6 +960,10 @@ static void dev_register_opts(struct lightningd *ld)
 		     opt_set_bool,
 		     &ld->dev_throttle_gossip,
 		     "Throttle gossip right down, for testing");
+	clnopt_noarg("--dev-limit-connections-inflight", OPT_DEV,
+		     opt_set_bool,
+		     &ld->dev_limit_connections_inflight,
+		     "Throttle connection limiting down for testing.");
 	/* This is handled directly in daemon_developer_mode(), so we ignore it here */
 	clnopt_noarg("--dev-debug-self", OPT_DEV,
 		     opt_ignore,

tests/test_connection.py

@@ -4655,3 +4655,38 @@ def test_connect_transient_pending(node_factory, bitcoind, executor):
             fut1.result(TIMEOUT)
         else:
             fut2.result(TIMEOUT)
+
+
+def test_connect_ratelimit(node_factory, bitcoind):
+    """l1 has 5 peers, restarts, make sure we limit"""
+    nodes = node_factory.get_nodes(6,
+                                   opts=[{'dev-limit-connections-inflight': None, 'may_reconnect': True}] + [{'may_reconnect': True}] * 5)
+
+    l1 = nodes[0]
+    nodes = nodes[1:]
+
+    addr = l1.rpc.newaddr()['bech32']
+    for n in nodes:
+        bitcoind.rpc.sendtoaddress(addr, (FUNDAMOUNT + 1000000) / 10**8)
+    bitcoind.generate_block(1, wait_for_mempool=len(nodes))
+    sync_blockheight(bitcoind, [l1])
+
+    for n in nodes:
+        l1.rpc.connect(n.info['id'], 'localhost', n.port)
+        l1.rpc.fundchannel(n.info['id'], FUNDAMOUNT)
+
+    # Make sure all channels are established and announced.
+    bitcoind.generate_block(6, wait_for_mempool=len(nodes))
+    wait_for(lambda: len(l1.rpc.listchannels()['channels']) == len(nodes) * 2)
+
+    assert not l1.daemon.is_in_log('Unblocking for')
+
+    l1.restart()
+
+    # The first will be ok, but others should block and be unblocked.
+    l1.daemon.wait_for_logs((['Unblocking for ']
+                             + ['Too many connections, waiting'])
+                            * (len(nodes) - 1))
+
+    # And now they're all connected
+    wait_for(lambda: [p['connected'] for p in l1.rpc.listpeers()['peers']] == [True] * len(nodes))