[PATCH net-next 0/8] mptcp: pm: in-kernel: increase limits

[PATCH net-next 0/8] mptcp: pm: in-kernel: increase limits

[Matthieu Baerts (NGI0)]

Allow switching from 8 to 64 for the maximum number of subflows and
accepted ADD_ADDR, and from 8 to 255 for the number of MPTCP endpoints.

The previous limit of 8 subflows makes sense in most cases. Using more
subflows will very likely *not* improve the situation, and could even
decrease the performances. But there are no technical limitations nor
performance impact to raise this limit, so let's do it: this will allow
people with very specific use-cases, and researchers to easily create
more subflows, and measure the performance impact by themselves.

- Patches 1-2: increase subflows and accepted ADD_ADDR limits.

- Patches 3-4: increase endpoints limit.

- Patches 5-7: validate the new limits: 64 subflows, 255 endpoints.

- Patch 8: selftests: use send()/recv() instead of sendto()/recvfrom().

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
Matthieu Baerts (NGI0) (8):
      mptcp: pm: in-kernel: explicitly limit batches to array size
      mptcp: pm: in-kernel: increase all limits to 64
      mptcp: pm: kernel: allow flushing more than 8 endpoints
      mptcp: pm: in-kernel: increase endpoints limit
      selftests: mptcp: join: allow changing ifaces nr per test
      selftests: mptcp: join: validate 8x8 subflows
      selftests: mptcp: pm: validate new limits
      selftests: mptcp: pm: use simpler send/recv forms

 net/mptcp/pm_kernel.c                           | 77 +++++++++++++++++--------
 tools/testing/selftests/net/mptcp/mptcp_join.sh | 33 ++++++++++-
 tools/testing/selftests/net/mptcp/pm_netlink.sh | 56 +++++++++++-------
 tools/testing/selftests/net/mptcp/pm_nl_ctl.c   |  8 +--
 4 files changed, 121 insertions(+), 53 deletions(-)
---
base-commit: 6a4c4656b0d2d4056a1f0c35442db4e8a5cf8021
change-id: 20260508-net-next-mptcp-pm-inc-limits-b825af50e400

Best regards,
--  
Matthieu Baerts (NGI0) <matttbe@kernel.org>

[PATCH net-next 5/8] selftests: mptcp: join: allow changing ifaces nr per test

[Matthieu Baerts (NGI0)]

By default, 4 network interfaces are created per subtest in a dedicated
net namespace. Each netns has a dedicated pair of v4 and v6 addresses.
Future tests will need more.

Simply always creating more network interfaces per test will increase
the execution time for all other tests, for no other benefits. So now it
is possible to change this number only when needed, by setting ifaces_nr
when calling 'reset' and 'init_shapers', e.g.

  ifaces_nr=8 reset "Subtest title"
  ifaces_nr=8 init_shapers

Note that it might also be interesting to decrease the default value to
2 to reduce the setup time, especially when a debug kernel config is
being used.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
To: Shuah Khan <shuah@kernel.org>
Cc: linux-kselftest@vger.kernel.org
---
 tools/testing/selftests/net/mptcp/mptcp_join.sh | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index beec41f6662a..28da9df797ae 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -63,6 +63,7 @@ unset fastclose
 unset fullmesh
 unset speed
 unset bind_addr
+unset ifaces_nr
 unset join_syn_rej
 unset join_csum_ns1
 unset join_csum_ns2
@@ -146,7 +147,7 @@ init_partial()
 	# ns1eth4    ns2eth4
 
 	local i
-	for i in $(seq 1 4); do
+	for i in $(seq 1 "${ifaces_nr:-4}"); do
 		ip link add ns1eth$i netns "$ns1" type veth peer name ns2eth$i netns "$ns2"
 		ip -net "$ns1" addr add 10.0.$i.1/24 dev ns1eth$i
 		ip -net "$ns1" addr add dead:beef:$i::1/64 dev ns1eth$i nodad
@@ -165,7 +166,7 @@ init_partial()
 init_shapers()
 {
 	local i
-	for i in $(seq 1 4); do
+	for i in $(seq 1 "${ifaces_nr:-4}"); do
 		tc -n $ns1 qdisc add dev ns1eth$i root netem rate 20mbit delay 1ms
 		tc -n $ns2 qdisc add dev ns2eth$i root netem rate 20mbit delay 1ms
 	done

-- 
2.53.0

[PATCH net-next 6/8] selftests: mptcp: join: validate 8x8 subflows

[Matthieu Baerts (NGI0)]

The limits have been recently increased, it is required to validate that
having 64 subflows is allowed.

Here, both the client and the server have 8 network interfaces. The
server has 8 endpoints marked as 'signal' to announce all its v4
addresses. The client also has 8 endpoints, but marked as 'subflow' and
'fullmesh' in order to create 8 subflows to each address announced by
the server. This means 63 additional subflows will be created after the
initial one.

If it is not possible to increase the limits to 64, it means an older
kernel version is being used, and the test is skipped.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
To: Shuah Khan <shuah@kernel.org>
Cc: linux-kselftest@vger.kernel.org
---
 tools/testing/selftests/net/mptcp/mptcp_join.sh | 28 +++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index 28da9df797ae..c6bb345d056b 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -513,6 +513,19 @@ reset_with_tcp_filter()
 	fi
 }
 
+# For kernel supporting limits above 8
+# $1: title ; $2,4: addrs limit ns1,2 ; $3,5: subflows limit ns1,2
+reset_with_high_limits()
+{
+	reset "${1}" || return 1
+
+	if ! pm_nl_set_limits "${ns1}" "${2}" "${3}" 2>/dev/null ||
+	   ! pm_nl_set_limits "${ns2}" "${4}" "${5}" 2>/dev/null; then
+		mark_as_skipped "unable to set the limits to ${*:2}"
+		return 1
+	fi
+}
+
 # $1: err msg
 fail_test()
 {
@@ -3670,6 +3683,21 @@ fullmesh_tests()
 		chk_prio_nr 0 1 1 0
 		chk_rm_nr 0 1
 	fi
+
+	# fullmesh in 8x8 to create 63 additional subflows
+	if ifaces_nr=8 reset_with_high_limits "fullmesh 8x8" 64 64 64 64; then
+		# higher chance to lose ADD_ADDR: allow retransmissions
+		ip netns exec $ns1 sysctl -q net.mptcp.add_addr_timeout=1
+		local i
+		for i in $(seq 1 8); do
+			pm_nl_add_endpoint $ns2 10.0.$i.2 flags subflow,fullmesh
+			pm_nl_add_endpoint $ns1 10.0.$i.1 flags signal
+		done
+		speed=slow \
+			run_tests $ns1 $ns2 10.0.1.1
+		chk_join_nr 63 63 63
+	fi
+
 }
 
 fastclose_tests()

-- 
2.53.0

[PATCH net-next 7/8] selftests: mptcp: pm: validate new limits

[Matthieu Baerts (NGI0)]

These limits have been recently updated, from 8 to:

- 64 for the subflows and accepted add_addr

- 255 for the MPTCP endpoints

These modifications validate the new limits, but are also compatible
with the previous ones, to be able to continue to validate stable kernel
using the last version of the selftests. That's why new variables are
now used instead of hard-coded values.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
To: Shuah Khan <shuah@kernel.org>
Cc: linux-kselftest@vger.kernel.org
---
 tools/testing/selftests/net/mptcp/pm_netlink.sh | 56 +++++++++++++++----------
 1 file changed, 35 insertions(+), 21 deletions(-)

diff --git a/tools/testing/selftests/net/mptcp/pm_netlink.sh b/tools/testing/selftests/net/mptcp/pm_netlink.sh
index 04594dfc22b1..21bfe1311f11 100755
--- a/tools/testing/selftests/net/mptcp/pm_netlink.sh
+++ b/tools/testing/selftests/net/mptcp/pm_netlink.sh
@@ -66,6 +66,15 @@ get_limits() {
 	fi
 }
 
+get_limits_nb() {
+	if mptcp_lib_is_ip_mptcp; then
+		ip -n "${ns1}" mptcp limits | awk '{ print $2" "$4 }'
+	else
+		ip netns exec "${ns1}" ./pm_nl_ctl limits | \
+			awk '{ printf "%s ", $2 }'
+	fi
+}
+
 format_endpoints() {
 	mptcp_lib_pm_nl_format_endpoints "${@}"
 }
@@ -164,6 +173,7 @@ check "get_endpoint 2" "" "simple del addr" 1
 check "show_endpoints" \
 	"$(format_endpoints "1,10.0.1.1" \
 			    "3,10.0.1.3,signal backup")" "dump addrs after del"
+add_endpoint 10.0.1.2 id 2
 
 add_endpoint 10.0.1.3 2>/dev/null
 check "get_endpoint 4" "" "duplicate addr" 1
@@ -171,25 +181,29 @@ check "get_endpoint 4" "" "duplicate addr" 1
 add_endpoint 10.0.1.4 flags signal
 check "get_endpoint 4" "$(format_endpoints "4,10.0.1.4,signal")" "id addr increment"
 
-for i in $(seq 5 9); do
-	add_endpoint "10.0.1.${i}" flags signal >/dev/null 2>&1
-done
-check "get_endpoint 9" "$(format_endpoints "9,10.0.1.9,signal")" "hard addr limit"
-check "get_endpoint 10" "" "above hard addr limit" 1
+read -r -a default_limits_nb <<< "$(get_limits_nb)"
+# limits have been increased: from 8 to 64 for subflows/add_addr & 255 for endp
+if mptcp_lib_expect_all_features || set_limits 9 9 2>/dev/null; then
+	max_endp=255
+	max_limits=64
+else
+	max_endp=8
+	max_limits=8
+fi
+set_limits "${default_limits_nb[@]}"
 
-del_endpoint 9
-for i in $(seq 10 255); do
-	add_endpoint 10.0.0.9 id "${i}"
-	del_endpoint "${i}"
+for i in $(seq 5 ${max_endp}); do
+	add_endpoint "10.0.0.${i}" id "${i}"
 done
-check "show_endpoints" \
-	"$(format_endpoints "1,10.0.1.1" \
-			    "3,10.0.1.3,signal backup" \
-			    "4,10.0.1.4,signal" \
-			    "5,10.0.1.5,signal" \
-			    "6,10.0.1.6,signal" \
-			    "7,10.0.1.7,signal" \
-			    "8,10.0.1.8,signal")" "id limit"
+check "get_endpoint ${max_endp}" \
+	"$(format_endpoints "${max_endp},10.0.0.${max_endp}")" "id limit"
+
+if add_endpoint '10.0.0.1' &>/dev/null; then
+	hardlimit="no error"
+else
+	hardlimit="error"
+fi
+check "echo ${hardlimit}" "error" "above hard addr limit"
 
 flush_endpoint
 check "show_endpoints" "" "flush addrs"
@@ -202,15 +216,15 @@ if ! mptcp_lib_is_ip_mptcp; then
 	flush_endpoint
 fi
 
-set_limits 9 1 2>/dev/null
+set_limits $((max_limits + 1)) 1 2>/dev/null
 check "get_limits" "${default_limits}" "rcv addrs above hard limit"
 
-set_limits 1 9 2>/dev/null
+set_limits 1 $((max_limits + 1)) 2>/dev/null
 check "get_limits" "${default_limits}" "subflows above hard limit"
 
-set_limits 8 8
+set_limits ${max_limits} ${max_limits}
 flush_endpoint  ## to make sure it doesn't affect the limits
-check "get_limits" "$(format_limits 8 8)" "set limits"
+check "get_limits" "$(format_limits ${max_limits} ${max_limits})" "set limits"
 
 flush_endpoint
 add_endpoint 10.0.1.1

-- 
2.53.0

[PATCH net-next 8/8] selftests: mptcp: pm: use simpler send/recv forms

[Matthieu Baerts (NGI0)]

Instead of sendto() and recvfrom() which the NL address that was already
provided before.

Just simpler and easier to read without the to/from variants.

While at it, fix a checkpatch warning by removing multiple assignments.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
To: Shuah Khan <shuah@kernel.org>
Cc: linux-kselftest@vger.kernel.org
---
 tools/testing/selftests/net/mptcp/pm_nl_ctl.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/net/mptcp/pm_nl_ctl.c b/tools/testing/selftests/net/mptcp/pm_nl_ctl.c
index 99eecccbf0c8..78180da1efcc 100644
--- a/tools/testing/selftests/net/mptcp/pm_nl_ctl.c
+++ b/tools/testing/selftests/net/mptcp/pm_nl_ctl.c
@@ -217,8 +217,6 @@ static int capture_events(int fd, int event_group)
 /* do a netlink command and, if max > 0, fetch the reply ; nh's size >1024B */
 static int do_nl_req(int fd, struct nlmsghdr *nh, int len, int max)
 {
-	struct sockaddr_nl nladdr = { .nl_family = AF_NETLINK };
-	socklen_t addr_len;
 	void *data = nh;
 	int rem, ret;
 	int err = 0;
@@ -230,15 +228,15 @@ static int do_nl_req(int fd, struct nlmsghdr *nh, int len, int max)
 	}
 
 	nh->nlmsg_len = len;
-	ret = sendto(fd, data, len, 0, (void *)&nladdr, sizeof(nladdr));
+	ret = send(fd, data, len, 0);
 	if (ret != len)
 		error(1, errno, "send netlink: %uB != %uB\n", ret, len);
 
-	addr_len = sizeof(nladdr);
-	rem = ret = recvfrom(fd, data, max, 0, (void *)&nladdr, &addr_len);
+	ret = recv(fd, data, max, 0);
 	if (ret < 0)
 		error(1, errno, "recv netlink: %uB\n", ret);
 
+	rem = ret;
 	/* Beware: the NLMSG_NEXT macro updates the 'rem' argument */
 	for (; NLMSG_OK(nh, rem); nh = NLMSG_NEXT(nh, rem)) {
 		if (nh->nlmsg_type == NLMSG_DONE)

-- 
2.53.0

Re: [PATCH net-next 0/8] mptcp: pm: in-kernel: increase limits

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Fri, 08 May 2026 17:40:45 +0200 you wrote:
> Allow switching from 8 to 64 for the maximum number of subflows and
> accepted ADD_ADDR, and from 8 to 255 for the number of MPTCP endpoints.
> 
> The previous limit of 8 subflows makes sense in most cases. Using more
> subflows will very likely *not* improve the situation, and could even
> decrease the performances. But there are no technical limitations nor
> performance impact to raise this limit, so let's do it: this will allow
> people with very specific use-cases, and researchers to easily create
> more subflows, and measure the performance impact by themselves.
> 
> [...]

Here is the summary with links:
  - [net-next,1/8] mptcp: pm: in-kernel: explicitly limit batches to array size
    https://git.kernel.org/netdev/net-next/c/9031e5e31d5d
  - [net-next,2/8] mptcp: pm: in-kernel: increase all limits to 64
    https://git.kernel.org/netdev/net-next/c/c8646664fbf1
  - [net-next,3/8] mptcp: pm: kernel: allow flushing more than 8 endpoints
    https://git.kernel.org/netdev/net-next/c/607f16ab462b
  - [net-next,4/8] mptcp: pm: in-kernel: increase endpoints limit
    https://git.kernel.org/netdev/net-next/c/e845e6397d78
  - [net-next,5/8] selftests: mptcp: join: allow changing ifaces nr per test
    https://git.kernel.org/netdev/net-next/c/e1515a1a494b
  - [net-next,6/8] selftests: mptcp: join: validate 8x8 subflows
    https://git.kernel.org/netdev/net-next/c/1697837a67fa
  - [net-next,7/8] selftests: mptcp: pm: validate new limits
    https://git.kernel.org/netdev/net-next/c/c9b581e619d2
  - [net-next,8/8] selftests: mptcp: pm: use simpler send/recv forms
    https://git.kernel.org/netdev/net-next/c/ed5372634c5b

You are awesome, thank you!
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