[PATCH net-next v4 0/2] bareudp: Enable BIG TCP packets

[PATCH net-next v4 0/2] bareudp: Enable BIG TCP packets

[Haishuang Yan]

This series allows BIG TCP on bareudp, the same way as on vxlan and
geneve, and extends the big_tcp_tunnels.sh selftest to cover it.

Patch 1 bumps tso_max_size of bareudp devices to GSO_MAX_SIZE.

Patch 2 adds bareudp to big_tcp_tunnels.sh. bareudp only works in
external mode, so the test attaches the tunnel metadata with a tc
tunnel_key action on egress.

Patch 2 depends on commit c57b2e60d4bf ("bareudp: set the inner protocol
to the protocol of the packet"), now in net-next.

v4:
- Patch 2: do not use "A && B || C" in setup_bareudp(), which shellcheck
  flags (SC2015), and Cc Simon.
v3: https://lore.kernel.org/netdev/20261008055513.1560739-1-yanhaishuang@cmss.chinamobile.com/
- Patch 2: create the bareudp device in setup_bareudp() and return an
  error if any step fails, update the comments that only mentioned VXLAN
  and GENEVE (Sashiko).
- Repost now that the bareudp fix is in net-next.
v2: https://lore.kernel.org/netdev/20261003100939.468181-1-yanhaishuang@cmss.chinamobile.com/
- Add Acked-by from Alice to patch 1.
- New patch 2, as Alice asked for selftest coverage.

v1: https://lore.kernel.org/netdev/20261001042336.224343-1-yanhaishuang@cmss.chinamobile.com/

Haishuang Yan (2):
  bareudp: Enable BIG TCP packets
  selftests: net: big_tcp_tunnels: Cover bareudp

 drivers/net/bareudp.c                         |  1 +
 .../testing/selftests/net/big_tcp_tunnels.sh  | 55 ++++++++++++++++---
 2 files changed, 47 insertions(+), 9 deletions(-)

-- 
2.43.0

[PATCH net-next v4 1/2] bareudp: Enable BIG TCP packets

[Haishuang Yan]

Commit f3d0f753f066 ("vxlan: Enable BIG TCP packets") and commit
03ebe91b0f61 ("geneve: Enable BIG TCP packets") allowed BIG TCP on vxlan
and geneve, after the preceding patches of that series made the common
UDP tunnel transmit path handle GSO packets larger than 64KB.

bareudp transmits through the same helpers, udp_tunnel_handle_offloads()
followed by udp_tunnel_xmit_skb() or udp_tunnel6_xmit_skb(), and does
not fill in any length field itself. Bump tso_max_size up to
GSO_MAX_SIZE so that the admin can use BIG TCP with bareudp too.

The default gso_max_size and gso_ipv4_max_size stay at 64KB, so nothing
changes unless they are raised explicitly.

iperf3 TCP over bareudp (ethertype ipv4, IPv4 outer) between two netns
connected by veth, MTU 1600 on veth, 3 runs of 20 seconds each. This
was measured in a QEMU TCG guest, so only the relative numbers are
meaningful:

  gso_max_size/gso_ipv4_max_size 65536:
    4380.6, 4404.2, 4354.5 Mbit/s, average 4379.8 Mbit/s

  gso_max_size/gso_ipv4_max_size 196608:
    5509.4, 5454.7, 5497.4 Mbit/s, average 5487.2 Mbit/s (+25%)

With 196608, about 90k to 100k packets larger than 64KB were
transmitted on the bareudp device per run, none with 65536. Without
this patch, setting gso_max_size to 196608 is rejected.

Assisted-by: LLM
Acked-by: Alice Mikityanska <alice.kernel@fastmail.im>
Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
---
 drivers/net/bareudp.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/bareudp.c b/drivers/net/bareudp.c
index c3b5ed52d877..fcc33e302b9c 100644
--- a/drivers/net/bareudp.c
+++ b/drivers/net/bareudp.c
@@ -589,6 +589,7 @@ static void bareudp_setup(struct net_device *dev)
 	dev->max_mtu = IP_MAX_MTU - BAREUDP_BASE_HLEN;
 	dev->type = ARPHRD_NONE;
 	netif_keep_dst(dev);
+	netif_set_tso_max_size(dev, GSO_MAX_SIZE);
 	dev->priv_flags |= IFF_NO_QUEUE;
 	dev->lltx = true;
 	dev->flags = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;
-- 
2.43.0

[PATCH net-next v4 2/2] selftests: net: big_tcp_tunnels: Cover bareudp

[Haishuang Yan]

Now that bareudp allows BIG TCP too, run the same checks over bareudp as
for vxlan and geneve.

bareudp only works in external mode, so attach the tunnel metadata to
all packets sent through the device with a tc tunnel_key action on
egress. The device uses ethertype ipv4 with multiproto, so that both
IPv4 and IPv6 traffic can go through it. Its MTU does not account for
the encapsulation, so lower it to leave room for the IPv6 and UDP
headers, otherwise the encapsulated packets would be fragmented.

Assisted-by: LLM
Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
---
 .../testing/selftests/net/big_tcp_tunnels.sh  | 55 ++++++++++++++++---
 1 file changed, 46 insertions(+), 9 deletions(-)

diff --git a/tools/testing/selftests/net/big_tcp_tunnels.sh b/tools/testing/selftests/net/big_tcp_tunnels.sh
index cc0875e52fb9..b0390b2c9f11 100755
--- a/tools/testing/selftests/net/big_tcp_tunnels.sh
+++ b/tools/testing/selftests/net/big_tcp_tunnels.sh
@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 # SPDX-License-Identifier: GPL-2.0
 #
-# Testing for IPv4 and IPv6 BIG TCP over VXLAN and GENEVE tunnels.
+# Testing for IPv4 and IPv6 BIG TCP over VXLAN, GENEVE and bareudp tunnels.
 
 source "$(dirname "$0")/lib.sh"
 
@@ -53,6 +53,24 @@ setup() {
 	DEFAULT_TCP_MIN_TSO_SEGS=$(ip netns exec "$CLIENT_NS" sysctl -n net.ipv4.tcp_min_tso_segs)
 }
 
+# Create a bareudp device. bareudp only works in external mode: attach the
+# tunnel metadata to all packets sent through the device. Its MTU does not
+# account for the encapsulation either, so leave room for IPv6 and UDP
+# headers.
+# $1: netns, $2: device, $3: local underlay address, $4: remote one
+setup_bareudp() {
+	ip -netns "$1" link add "$2" type bareudp \
+		dstport 6635 ethertype ipv4 multiproto &&
+	ip -netns "$1" link set "$2" mtu 1452 &&
+	tc -netns "$1" qdisc add dev "$2" clsact &&
+	tc -netns "$1" filter add dev "$2" egress matchall \
+		action tunnel_key set src_ip "$3" dst_ip "$4" id 0 ttl 64 &&
+	return 0
+
+	echo "Failed to set up bareudp device $2" >&2
+	return 1
+}
+
 setup_tunnel() {
 	if [ "$2" = 4 ]; then
 		SERVER_IP="$SERVER_IP4"
@@ -64,26 +82,40 @@ setup_tunnel() {
 		echo "Setting up ${1^^} over IPv6, veth tx csum offload $3"
 	fi
 
-	if [ "$1" = vxlan ]; then
+	case "$1" in
+	vxlan)
 		ip -netns "$CLIENT_NS" link add tun0 type vxlan \
 			id 5001 remote "$SERVER_IP" local "$CLIENT_IP" dev link0 dstport 4789
-	else
+		;;
+	geneve)
 		ip -netns "$CLIENT_NS" link add tun0 type geneve \
 			id 5001 remote "$SERVER_IP"
-	fi
+		;;
+	bareudp)
+		setup_bareudp "$CLIENT_NS" tun0 "$CLIENT_IP" "$SERVER_IP" ||
+			return 1
+		;;
+	esac
 	ip -netns "$CLIENT_NS" link set tun0 up
 	ip -netns "$CLIENT_NS" addr replace "$CLIENT_IP4_TUN/24" dev tun0
 	ip -netns "$CLIENT_NS" addr replace "$CLIENT_IP6_TUN/112" dev tun0 nodad
 	ip -netns "$CLIENT_NS" link set tun0 \
 		gso_max_size 196608 gso_ipv4_max_size 196608 \
 		gro_max_size 196608 gro_ipv4_max_size 196608
-	if [ "$1" = vxlan ]; then
+	case "$1" in
+	vxlan)
 		ip -netns "$SERVER_NS" link add tun1 type vxlan \
 			id 5001 remote "$CLIENT_IP" local "$SERVER_IP" dev link1 dstport 4789
-	else
+		;;
+	geneve)
 		ip -netns "$SERVER_NS" link add tun1 type geneve \
 			id 5001 remote "$CLIENT_IP"
-	fi
+		;;
+	bareudp)
+		setup_bareudp "$SERVER_NS" tun1 "$SERVER_IP" "$CLIENT_IP" ||
+			return 1
+		;;
+	esac
 	ip -netns "$SERVER_NS" link set tun1 up
 	ip -netns "$SERVER_NS" addr replace "$SERVER_IP4_TUN/24" dev tun1
 	ip -netns "$SERVER_NS" addr replace "$SERVER_IP6_TUN/112" dev tun1 nodad
@@ -112,7 +144,7 @@ do_test() {
 	local packets_threshold="$PACKETS_THRESHOLD"
 
 	# When tx csum offload is off, software GSO is performed before passing the
-	# packet to veth. Check BIG TCP packets inside the VXLAN tunnel to verify
+	# packet to veth. Check BIG TCP packets inside the tunnel to verify
 	# the software checksum path: if the checksum code is broken, these packets
 	# will be dropped.
 	if [ "$3" = on ]; then
@@ -192,6 +224,11 @@ if ! iptables --version &> /dev/null; then
 	exit "$ksft_skip"
 fi
 
+if ! tc -V &> /dev/null; then
+	echo "SKIP: Could not run test without tc tool"
+	exit "$ksft_skip"
+fi
+
 if ! ethtool --version &> /dev/null; then
 	echo "SKIP: Could not run test without ethtool tool"
 	exit "$ksft_skip"
@@ -205,7 +242,7 @@ fi
 WORKDIR=$(mktemp -d)
 trap cleanup EXIT
 setup
-for tunnel in vxlan geneve; do
+for tunnel in vxlan geneve bareudp; do
 	for tun_family in 4 6; do
 		for traffic_family in 4 6; do
 			for csum_offload in on off; do
-- 
2.43.0

Re: [PATCH net-next v4 1/2] bareudp: Enable BIG TCP packets

[Simon Horman]

On Sun, Oct 11, 2026 at 06:20:22PM +0800, Haishuang Yan wrote:
> Commit f3d0f753f066 ("vxlan: Enable BIG TCP packets") and commit
> 03ebe91b0f61 ("geneve: Enable BIG TCP packets") allowed BIG TCP on vxlan
> and geneve, after the preceding patches of that series made the common
> UDP tunnel transmit path handle GSO packets larger than 64KB.
> 
> bareudp transmits through the same helpers, udp_tunnel_handle_offloads()
> followed by udp_tunnel_xmit_skb() or udp_tunnel6_xmit_skb(), and does
> not fill in any length field itself. Bump tso_max_size up to
> GSO_MAX_SIZE so that the admin can use BIG TCP with bareudp too.
> 
> The default gso_max_size and gso_ipv4_max_size stay at 64KB, so nothing
> changes unless they are raised explicitly.
> 
> iperf3 TCP over bareudp (ethertype ipv4, IPv4 outer) between two netns
> connected by veth, MTU 1600 on veth, 3 runs of 20 seconds each. This
> was measured in a QEMU TCG guest, so only the relative numbers are
> meaningful:
> 
>   gso_max_size/gso_ipv4_max_size 65536:
>     4380.6, 4404.2, 4354.5 Mbit/s, average 4379.8 Mbit/s
> 
>   gso_max_size/gso_ipv4_max_size 196608:
>     5509.4, 5454.7, 5497.4 Mbit/s, average 5487.2 Mbit/s (+25%)
> 
> With 196608, about 90k to 100k packets larger than 64KB were
> transmitted on the bareudp device per run, none with 65536. Without
> this patch, setting gso_max_size to 196608 is rejected.
> 
> Assisted-by: LLM
> Acked-by: Alice Mikityanska <alice.kernel@fastmail.im>
> Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [PATCH net-next v4 2/2] selftests: net: big_tcp_tunnels: Cover bareudp

[Simon Horman]

On Sun, Oct 11, 2026 at 06:20:23PM +0800, Haishuang Yan wrote:
> Now that bareudp allows BIG TCP too, run the same checks over bareudp as
> for vxlan and geneve.
> 
> bareudp only works in external mode, so attach the tunnel metadata to
> all packets sent through the device with a tc tunnel_key action on
> egress. The device uses ethertype ipv4 with multiproto, so that both
> IPv4 and IPv6 traffic can go through it. Its MTU does not account for
> the encapsulation, so lower it to leave room for the IPv6 and UDP
> headers, otherwise the encapsulated packets would be fragmented.
> 
> Assisted-by: LLM
> Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>

Reviewed-by: Simon Horman <horms@kernel.org>