Commit b90c7ca4 authored by Jakub Kicinski's avatar Jakub Kicinski
Browse files

Merge branch 'mptcp-make-add_addr-retransmission-timeout-adaptive' 

Matthieu Baerts says:

====================
mptcp: make ADD_ADDR retransmission timeout adaptive

Currently, the MPTCP ADD_ADDR notifications are retransmitted after a
fixed timeout controlled by the net.mptcp.add_addr_timeout sysctl knob,
if the corresponding "echo" packets are not received before. This can be
too slow (or too quick), especially with a too cautious default value
set to 2 minutes.

- Patch 1: make ADD_ADDR retransmission timeout adaptive, using the
  TCP's retransmission timeout. The corresponding sysctl knob is now
  used as a maximum value.

- Patch 2: now that these ADD_ADDR retransmissions can happen faster,
  all MPTCP Join subtests checking ADD_ADDR counters accept more
  ADD_ADDR than expected (if any). This is aligned with the previous
  behaviour, when the ADD_ADDR RTO was lowered down to 1 second.

- Patch 3: Some CIs have reported that some MPTCP Join signalling tests
  were unstable. It seems that it is due to the time it can take in slow
  environments to send a bunch of ADD_ADDR notifications and wait each
  time for their echo reply. Use a longer transfer to avoid such errors.

v1: https://lore.kernel.org/d5397026-92eb-4a43-9534-954b43ab9305@kernel.org
====================

Link: https://patch.msgid.link/20250907-net-next-mptcp-add_addr-retrans-adapt-v1-0-824cc805772b@kernel.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parents 4ea83b75 e2cda634

Documentation/networking/mptcp-sysctl.rst

+5 −3
Original line number Diff line number Diff line
@@ -8,9 +8,11 @@ MPTCP Sysfs variables 
===============================



add_addr_timeout - INTEGER (seconds)

	Set the timeout after which an ADD_ADDR control message will be

	resent to an MPTCP peer that has not acknowledged a previous

	ADD_ADDR message.

	Set the maximum value of timeout after which an ADD_ADDR control message

	will be resent to an MPTCP peer that has not acknowledged a previous

	ADD_ADDR message. A dynamically estimated retransmission timeout based

	on the estimated connection round-trip-time is used if this value is

	lower than the maximum one.



	Do not retransmit if set to 0.

net/mptcp/pm.c

+24 −4
Original line number Diff line number Diff line
@@ -268,6 +268,27 @@ int mptcp_pm_mp_prio_send_ack(struct mptcp_sock *msk, 
	return -EINVAL;

}



static unsigned int mptcp_adjust_add_addr_timeout(struct mptcp_sock *msk)

{

	const struct net *net = sock_net((struct sock *)msk);

	unsigned int rto = mptcp_get_add_addr_timeout(net);

	struct mptcp_subflow_context *subflow;

	unsigned int max = 0;



	mptcp_for_each_subflow(msk, subflow) {

		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);

		struct inet_connection_sock *icsk = inet_csk(ssk);



		if (icsk->icsk_rto > max)

			max = icsk->icsk_rto;

	}



	if (max && max < rto)

		rto = max;



	return rto;

}



static void mptcp_pm_add_timer(struct timer_list *timer)

{

	struct mptcp_pm_add_entry *entry = timer_container_of(entry, timer,
@@ -292,7 +313,7 @@ static void mptcp_pm_add_timer(struct timer_list *timer) 
		goto out;

	}



	timeout = mptcp_get_add_addr_timeout(sock_net(sk));

	timeout = mptcp_adjust_add_addr_timeout(msk);

	if (!timeout)

		goto out;
@@ -307,7 +328,7 @@ static void mptcp_pm_add_timer(struct timer_list *timer) 


	if (entry->retrans_times < ADD_ADDR_RETRANS_MAX)

		sk_reset_timer(sk, timer,

			       jiffies + timeout);

			       jiffies + (timeout << entry->retrans_times));



	spin_unlock_bh(&msk->pm.lock);
@@ -348,7 +369,6 @@ bool mptcp_pm_alloc_anno_list(struct mptcp_sock *msk, 
{

	struct mptcp_pm_add_entry *add_entry = NULL;

	struct sock *sk = (struct sock *)msk;

	struct net *net = sock_net(sk);

	unsigned int timeout;



	lockdep_assert_held(&msk->pm.lock);
@@ -374,7 +394,7 @@ bool mptcp_pm_alloc_anno_list(struct mptcp_sock *msk, 


	timer_setup(&add_entry->add_timer, mptcp_pm_add_timer, 0);

reset_timer:

	timeout = mptcp_get_add_addr_timeout(net);

	timeout = mptcp_adjust_add_addr_timeout(msk);

	if (timeout)

		sk_reset_timer(sk, &add_entry->add_timer, jiffies + timeout);

tools/testing/selftests/net/mptcp/mptcp_join.sh

+11 −14
Original line number Diff line number Diff line
@@ -358,6 +358,7 @@ reset_with_add_addr_timeout() 
		tables="${ip6tables}"

	fi



	# set a maximum, to avoid too long timeout with exponential backoff

	ip netns exec $ns1 sysctl -q net.mptcp.add_addr_timeout=1



	if ! ip netns exec $ns2 $tables -A OUTPUT -p tcp \
@@ -1669,7 +1670,6 @@ chk_add_nr() 
	local tx=""

	local rx=""

	local count

	local timeout



	if [[ $ns_invert = "invert" ]]; then

		ns_tx=$ns2
@@ -1678,15 +1678,13 @@ chk_add_nr() 
		rx=" server"

	fi



	timeout=$(ip netns exec ${ns_tx} sysctl -n net.mptcp.add_addr_timeout)



	print_check "add addr rx${rx}"

	count=$(mptcp_lib_get_counter ${ns_rx} "MPTcpExtAddAddr")

	if [ -z "$count" ]; then

		print_skip

	# if the test configured a short timeout tolerate greater then expected

	# add addrs options, due to retransmissions

	elif [ "$count" != "$add_nr" ] && { [ "$timeout" -gt 1 ] || [ "$count" -lt "$add_nr" ]; }; then

	# Tolerate more ADD_ADDR then expected (if any), due to retransmissions

	elif [ "$count" != "$add_nr" ] &&

	     { [ "$add_nr" -eq 0 ] || [ "$count" -lt "$add_nr" ]; }; then

		fail_test "got $count ADD_ADDR[s] expected $add_nr"

	else

		print_ok
@@ -1774,18 +1772,15 @@ chk_add_tx_nr() 
{

	local add_tx_nr=$1

	local echo_tx_nr=$2

	local timeout

	local count



	timeout=$(ip netns exec $ns1 sysctl -n net.mptcp.add_addr_timeout)



	print_check "add addr tx"

	count=$(mptcp_lib_get_counter ${ns1} "MPTcpExtAddAddrTx")

	if [ -z "$count" ]; then

		print_skip

	# if the test configured a short timeout tolerate greater then expected

	# add addrs options, due to retransmissions

	elif [ "$count" != "$add_tx_nr" ] && { [ "$timeout" -gt 1 ] || [ "$count" -lt "$add_tx_nr" ]; }; then

	# Tolerate more ADD_ADDR then expected (if any), due to retransmissions

	elif [ "$count" != "$add_tx_nr" ] &&

	     { [ "$add_tx_nr" -eq 0 ] || [ "$count" -lt "$add_tx_nr" ]; }; then

		fail_test "got $count ADD_ADDR[s] TX, expected $add_tx_nr"

	else

		print_ok
@@ -2273,6 +2268,7 @@ signal_address_tests() 
		pm_nl_add_endpoint $ns1 10.0.3.1 flags signal

		pm_nl_add_endpoint $ns1 10.0.4.1 flags signal

		pm_nl_set_limits $ns2 3 3

		speed=slow \

			run_tests $ns1 $ns2 10.0.1.1

		chk_join_nr 3 3 3

		chk_add_nr 3 3
@@ -2285,6 +2281,7 @@ signal_address_tests() 
		pm_nl_add_endpoint $ns1 10.0.3.1 flags signal

		pm_nl_add_endpoint $ns1 10.0.14.1 flags signal

		pm_nl_set_limits $ns2 3 3

		speed=slow \

			run_tests $ns1 $ns2 10.0.1.1

		join_syn_tx=3 \

			chk_join_nr 1 1 1