Re: [PATCH mptcp-next v2 2/3] selftests: mptcp: join: tolerate more ADD_ADDR

[Matthieu Baerts <matttbe@kernel.org>]

On 04/09/2025 13:38, Matthieu Baerts (NGI0) wrote:
> ADD_ADDR can be retransmitted, and with, the parent commit, these
> retransmissions can be sent quicker: from 2 minutes to less than one
> second.
> 
> To avoid false positives where retransmitted ADD_ADDR causes higher
> counters than expected, it is required to be more tolerant. Errors are
> now only reported when fewer ADD_ADDRs have been sent/received, except
> if no ADD_ADDR are expected.
> 
> Before the parent commit, the tolerance was present for each tests where
> the ADD_ADDR could be retransmitted in a reasonable time (1 sec). Now
> that all tests can have retransmitted ADD_ADDR, it is normal to apply
> the same tolerance for all tests.
> 
> An alternative could be to disable the ADD_ADDR retransmissions by
> default, but that's changing the default kernel behaviour. Plus,
> ADD_ADDR retransmissions can be required for some tests. To avoid adding
> exceptions to many tests, it seems better to increase the tolerance.
> 
> Later, we could add a new MIB counter to identify the ADD_ADDR
> retransmissions, and remove the tolerance when this counter is
> available.
> 
> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
> ---
>  tools/testing/selftests/net/mptcp/mptcp_join.sh | 19 +++++++------------
>  1 file changed, 7 insertions(+), 12 deletions(-)
> 
> diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
> index 2f046167a0b6cc6fb5531a033d8d95c9ea399cf9..be49712f91155a1f14f6cc21776764d65a897c27 100755
> --- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
> +++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
> @@ -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" -lt "$add_nr" ] ||
> +	     { [ "$count" != "$add_nr" ] && [ "$add_nr" != 0 ]; }; then

Arf, it should be:

  "$add_nr" == 0
>  		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" -lt "$add_tx_nr" ] ||
> +	     { [ "$count" != "$add_tx_nr" ] && [ "$add_tx_nr" != 0 ]; }; then

Same here:

  "$add_tx_nr" == 0

If there is nothing else, I can fix that when applying the patches.

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

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.