* [PATCH net v3 1/2] net: ipv4: fix regression in local-broadcast routes
@ 2025-08-27 6:23 Oscar Maes
2025-08-27 6:23 ` [PATCH net v3 2/2] selftests: net: add test for destination in broadcast packets Oscar Maes
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Oscar Maes @ 2025-08-27 6:23 UTC (permalink / raw)
To: netdev, bacs, brett, kuba; +Cc: davem, dsahern, regressions, stable, Oscar Maes
Commit 9e30ecf23b1b ("net: ipv4: fix incorrect MTU in broadcast routes")
introduced a regression where local-broadcast packets would have their
gateway set in __mkroute_output, which was caused by fi = NULL being
removed.
Fix this by resetting the fib_info for local-broadcast packets. This
preserves the intended changes for directed-broadcast packets.
Cc: stable@vger.kernel.org
Fixes: 9e30ecf23b1b ("net: ipv4: fix incorrect MTU in broadcast routes")
Reported-by: Brett A C Sheffield <bacs@librecast.net>
Closes: https://lore.kernel.org/regressions/20250822165231.4353-4-bacs@librecast.net
Signed-off-by: Oscar Maes <oscmaes92@gmail.com>
---
Link to discussion:
https://lore.kernel.org/netdev/20250822165231.4353-4-bacs@librecast.net/
Thanks to Brett Sheffield for finding the regression and writing
the initial fix!
net/ipv4/route.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index f639a2ae881a..baa43e5966b1 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2575,12 +2575,16 @@ static struct rtable *__mkroute_output(const struct fib_result *res,
!netif_is_l3_master(dev_out))
return ERR_PTR(-EINVAL);
- if (ipv4_is_lbcast(fl4->daddr))
+ if (ipv4_is_lbcast(fl4->daddr)) {
type = RTN_BROADCAST;
- else if (ipv4_is_multicast(fl4->daddr))
+
+ /* reset fi to prevent gateway resolution */
+ fi = NULL;
+ } else if (ipv4_is_multicast(fl4->daddr)) {
type = RTN_MULTICAST;
- else if (ipv4_is_zeronet(fl4->daddr))
+ } else if (ipv4_is_zeronet(fl4->daddr)) {
return ERR_PTR(-EINVAL);
+ }
if (dev_out->flags & IFF_LOOPBACK)
flags |= RTCF_LOCAL;
--
2.39.5
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH net v3 2/2] selftests: net: add test for destination in broadcast packets
2025-08-27 6:23 [PATCH net v3 1/2] net: ipv4: fix regression in local-broadcast routes Oscar Maes
@ 2025-08-27 6:23 ` Oscar Maes
2025-08-27 14:26 ` Brett A C Sheffield
2025-08-27 16:09 ` [PATCH net v3 1/2] net: ipv4: fix regression in local-broadcast routes David Ahern
2025-08-28 9:00 ` patchwork-bot+netdevbpf
2 siblings, 1 reply; 6+ messages in thread
From: Oscar Maes @ 2025-08-27 6:23 UTC (permalink / raw)
To: netdev, bacs, brett, kuba; +Cc: davem, dsahern, regressions, stable, Oscar Maes
Add test to check the broadcast ethernet destination field is set
correctly.
This test sends a broadcast ping, captures it using tcpdump and
ensures that all bits of the 6 octet ethernet destination address
are correctly set by examining the output capture file.
Signed-off-by: Oscar Maes <oscmaes92@gmail.com>
---
Link to discussion:
https://lore.kernel.org/netdev/20250822165231.4353-4-bacs@librecast.net/
Thanks to Brett Sheffield for writing the initial version of this
selftest!
tools/testing/selftests/net/Makefile | 1 +
.../selftests/net/broadcast_ether_dst.sh | 82 +++++++++++++++++++
2 files changed, 83 insertions(+)
create mode 100755 tools/testing/selftests/net/broadcast_ether_dst.sh
diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
index b31a71f2b372..56ad10ea6628 100644
--- a/tools/testing/selftests/net/Makefile
+++ b/tools/testing/selftests/net/Makefile
@@ -115,6 +115,7 @@ TEST_PROGS += skf_net_off.sh
TEST_GEN_FILES += skf_net_off
TEST_GEN_FILES += tfo
TEST_PROGS += tfo_passive.sh
+TEST_PROGS += broadcast_ether_dst.sh
TEST_PROGS += broadcast_pmtu.sh
TEST_PROGS += ipv6_force_forwarding.sh
diff --git a/tools/testing/selftests/net/broadcast_ether_dst.sh b/tools/testing/selftests/net/broadcast_ether_dst.sh
new file mode 100755
index 000000000000..865b5c7c8c8a
--- /dev/null
+++ b/tools/testing/selftests/net/broadcast_ether_dst.sh
@@ -0,0 +1,82 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Author: Brett A C Sheffield <bacs@librecast.net>
+# Author: Oscar Maes <oscmaes92@gmail.com>
+#
+# Ensure destination ethernet field is correctly set for
+# broadcast packets
+
+source lib.sh
+
+CLIENT_IP4="192.168.0.1"
+GW_IP4="192.168.0.2"
+
+setup() {
+ setup_ns CLIENT_NS SERVER_NS
+
+ ip -net "${SERVER_NS}" link add link1 type veth \
+ peer name link0 netns "${CLIENT_NS}"
+
+ ip -net "${CLIENT_NS}" link set link0 up
+ ip -net "${CLIENT_NS}" addr add "${CLIENT_IP4}"/24 dev link0
+
+ ip -net "${SERVER_NS}" link set link1 up
+
+ ip -net "${CLIENT_NS}" route add default via "${GW_IP4}"
+ ip netns exec "${CLIENT_NS}" arp -s "${GW_IP4}" 00:11:22:33:44:55
+}
+
+cleanup() {
+ rm -f "${CAPFILE}"
+ ip -net "${SERVER_NS}" link del link1
+ cleanup_ns "${CLIENT_NS}" "${SERVER_NS}"
+}
+
+test_broadcast_ether_dst() {
+ local rc=0
+ CAPFILE=$(mktemp -u cap.XXXXXXXXXX)
+
+ echo "Testing ethernet broadcast destination"
+
+ # start tcpdump listening for icmp
+ # tcpdump will exit after receiving a single packet
+ # timeout will kill tcpdump if it is still running after 2s
+ timeout 2s ip netns exec "${CLIENT_NS}" \
+ tcpdump -i link0 -c 1 -w "${CAPFILE}" icmp &> /dev/null &
+ pid=$!
+ sleep 0.1 # let tcpdump wake up
+
+ # send broadcast ping
+ ip netns exec "${CLIENT_NS}" \
+ ping -W0.01 -c1 -b 255.255.255.255 &> /dev/null
+
+ # wait for tcpdump for exit after receiving packet
+ wait "${pid}"
+
+ # compare ethernet destination field to ff:ff:ff:ff:ff:ff
+ ether_dst=$(tcpdump -r "${CAPFILE}" -tnne 2>/dev/null | \
+ awk '{sub(/,/,"",$3); print $3}')
+ if [[ "${ether_dst}" == "ff:ff:ff:ff:ff:ff" ]]; then
+ echo "[ OK ]"
+ rc="${ksft_pass}"
+ else
+ echo "[FAIL] expected dst ether addr to be ff:ff:ff:ff:ff:ff," \
+ "got ${ether_dst}"
+ rc="${ksft_fail}"
+ fi
+
+ return "${rc}"
+}
+
+if [ ! -x "$(command -v tcpdump)" ]; then
+ echo "SKIP: Could not run test without tcpdump tool"
+ exit "${ksft_skip}"
+fi
+
+trap cleanup EXIT
+
+setup
+test_broadcast_ether_dst
+
+exit $?
--
2.39.5
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH net v3 2/2] selftests: net: add test for destination in broadcast packets
2025-08-27 6:23 ` [PATCH net v3 2/2] selftests: net: add test for destination in broadcast packets Oscar Maes
@ 2025-08-27 14:26 ` Brett A C Sheffield
2025-08-28 8:51 ` Paolo Abeni
0 siblings, 1 reply; 6+ messages in thread
From: Brett A C Sheffield @ 2025-08-27 14:26 UTC (permalink / raw)
To: Oscar Maes; +Cc: netdev, kuba, davem, dsahern, regressions, stable
On 2025-08-27 08:23, Oscar Maes wrote:
> Add test to check the broadcast ethernet destination field is set
> correctly.
>
> This test sends a broadcast ping, captures it using tcpdump and
> ensures that all bits of the 6 octet ethernet destination address
> are correctly set by examining the output capture file.
>
> Signed-off-by: Oscar Maes <oscmaes92@gmail.com>
> ---
> Link to discussion:
> https://lore.kernel.org/netdev/20250822165231.4353-4-bacs@librecast.net/
>
> Thanks to Brett Sheffield for writing the initial version of this
> selftest!
Thanks for leaving my author name in the file. Perhaps you might consider
adding:
Co-Authored-By: Brett A C Sheffield <bacs@librecast.net>
to your commit message. I spend quite a bit of my Saturday bisecting and
diagnosing, and writing the patch and test.
> tools/testing/selftests/net/Makefile | 1 +
> .../selftests/net/broadcast_ether_dst.sh | 82 +++++++++++++++++++
> 2 files changed, 83 insertions(+)
> create mode 100755 tools/testing/selftests/net/broadcast_ether_dst.sh
>
> diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
> index b31a71f2b372..56ad10ea6628 100644
> --- a/tools/testing/selftests/net/Makefile
> +++ b/tools/testing/selftests/net/Makefile
> @@ -115,6 +115,7 @@ TEST_PROGS += skf_net_off.sh
> TEST_GEN_FILES += skf_net_off
> TEST_GEN_FILES += tfo
> TEST_PROGS += tfo_passive.sh
> +TEST_PROGS += broadcast_ether_dst.sh
> TEST_PROGS += broadcast_pmtu.sh
> TEST_PROGS += ipv6_force_forwarding.sh
>
> diff --git a/tools/testing/selftests/net/broadcast_ether_dst.sh b/tools/testing/selftests/net/broadcast_ether_dst.sh
> new file mode 100755
> index 000000000000..865b5c7c8c8a
> --- /dev/null
> +++ b/tools/testing/selftests/net/broadcast_ether_dst.sh
> @@ -0,0 +1,82 @@
> +#!/bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +#
> +# Author: Brett A C Sheffield <bacs@librecast.net>
> +# Author: Oscar Maes <oscmaes92@gmail.com>
> +#
> +# Ensure destination ethernet field is correctly set for
> +# broadcast packets
> +
> +source lib.sh
> +
> +CLIENT_IP4="192.168.0.1"
> +GW_IP4="192.168.0.2"
> +
> +setup() {
> + setup_ns CLIENT_NS SERVER_NS
> +
> + ip -net "${SERVER_NS}" link add link1 type veth \
> + peer name link0 netns "${CLIENT_NS}"
> +
> + ip -net "${CLIENT_NS}" link set link0 up
> + ip -net "${CLIENT_NS}" addr add "${CLIENT_IP4}"/24 dev link0
> +
> + ip -net "${SERVER_NS}" link set link1 up
> +
> + ip -net "${CLIENT_NS}" route add default via "${GW_IP4}"
> + ip netns exec "${CLIENT_NS}" arp -s "${GW_IP4}" 00:11:22:33:44:55
> +}
> +
> +cleanup() {
> + rm -f "${CAPFILE}"
> + ip -net "${SERVER_NS}" link del link1
> + cleanup_ns "${CLIENT_NS}" "${SERVER_NS}"
> +}
> +
> +test_broadcast_ether_dst() {
> + local rc=0
> + CAPFILE=$(mktemp -u cap.XXXXXXXXXX)
> +
> + echo "Testing ethernet broadcast destination"
> +
> + # start tcpdump listening for icmp
> + # tcpdump will exit after receiving a single packet
> + # timeout will kill tcpdump if it is still running after 2s
> + timeout 2s ip netns exec "${CLIENT_NS}" \
> + tcpdump -i link0 -c 1 -w "${CAPFILE}" icmp &> /dev/null &
> + pid=$!
> + sleep 0.1 # let tcpdump wake up
> +
> + # send broadcast ping
> + ip netns exec "${CLIENT_NS}" \
> + ping -W0.01 -c1 -b 255.255.255.255 &> /dev/null
> +
> + # wait for tcpdump for exit after receiving packet
> + wait "${pid}"
> +
> + # compare ethernet destination field to ff:ff:ff:ff:ff:ff
> + ether_dst=$(tcpdump -r "${CAPFILE}" -tnne 2>/dev/null | \
> + awk '{sub(/,/,"",$3); print $3}')
> + if [[ "${ether_dst}" == "ff:ff:ff:ff:ff:ff" ]]; then
> + echo "[ OK ]"
> + rc="${ksft_pass}"
> + else
> + echo "[FAIL] expected dst ether addr to be ff:ff:ff:ff:ff:ff," \
> + "got ${ether_dst}"
> + rc="${ksft_fail}"
> + fi
> +
> + return "${rc}"
> +}
> +
> +if [ ! -x "$(command -v tcpdump)" ]; then
> + echo "SKIP: Could not run test without tcpdump tool"
> + exit "${ksft_skip}"
> +fi
> +
> +trap cleanup EXIT
> +
> +setup
> +test_broadcast_ether_dst
> +
> +exit $?
> --
> 2.39.5
>
>
--
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH net v3 1/2] net: ipv4: fix regression in local-broadcast routes
2025-08-27 6:23 [PATCH net v3 1/2] net: ipv4: fix regression in local-broadcast routes Oscar Maes
2025-08-27 6:23 ` [PATCH net v3 2/2] selftests: net: add test for destination in broadcast packets Oscar Maes
@ 2025-08-27 16:09 ` David Ahern
2025-08-28 9:00 ` patchwork-bot+netdevbpf
2 siblings, 0 replies; 6+ messages in thread
From: David Ahern @ 2025-08-27 16:09 UTC (permalink / raw)
To: Oscar Maes, netdev, bacs, brett, kuba; +Cc: davem, regressions, stable
On 8/27/25 12:23 AM, Oscar Maes wrote:
> Commit 9e30ecf23b1b ("net: ipv4: fix incorrect MTU in broadcast routes")
> introduced a regression where local-broadcast packets would have their
> gateway set in __mkroute_output, which was caused by fi = NULL being
> removed.
>
> Fix this by resetting the fib_info for local-broadcast packets. This
> preserves the intended changes for directed-broadcast packets.
>
> Cc: stable@vger.kernel.org
> Fixes: 9e30ecf23b1b ("net: ipv4: fix incorrect MTU in broadcast routes")
> Reported-by: Brett A C Sheffield <bacs@librecast.net>
> Closes: https://lore.kernel.org/regressions/20250822165231.4353-4-bacs@librecast.net
> Signed-off-by: Oscar Maes <oscmaes92@gmail.com>
> ---
> Link to discussion:
> https://lore.kernel.org/netdev/20250822165231.4353-4-bacs@librecast.net/
>
> Thanks to Brett Sheffield for finding the regression and writing
> the initial fix!
>
> net/ipv4/route.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
Reviewed-by: David Ahern <dsahern@kernel.org>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH net v3 2/2] selftests: net: add test for destination in broadcast packets
2025-08-27 14:26 ` Brett A C Sheffield
@ 2025-08-28 8:51 ` Paolo Abeni
0 siblings, 0 replies; 6+ messages in thread
From: Paolo Abeni @ 2025-08-28 8:51 UTC (permalink / raw)
To: Brett A C Sheffield, Oscar Maes
Cc: netdev, kuba, davem, dsahern, regressions, stable
On 8/27/25 4:26 PM, Brett A C Sheffield wrote:
> On 2025-08-27 08:23, Oscar Maes wrote:
>> Add test to check the broadcast ethernet destination field is set
>> correctly.
>>
>> This test sends a broadcast ping, captures it using tcpdump and
>> ensures that all bits of the 6 octet ethernet destination address
>> are correctly set by examining the output capture file.
>>
>> Signed-off-by: Oscar Maes <oscmaes92@gmail.com>
>> ---
>> Link to discussion:
>> https://lore.kernel.org/netdev/20250822165231.4353-4-bacs@librecast.net/
>>
>> Thanks to Brett Sheffield for writing the initial version of this
>> selftest!
>
> Thanks for leaving my author name in the file. Perhaps you might consider
> adding:
>
> Co-Authored-By: Brett A C Sheffield <bacs@librecast.net>
>
> to your commit message. I spend quite a bit of my Saturday bisecting and
> diagnosing, and writing the patch and test.
I don't want to delay the fix, since I received other reports for the
same problem, but I think proper recognition should be agreed by all the
involved parties.
I'm going to apply patch 1/2 standalone, to allow repost for this one.
>> tools/testing/selftests/net/Makefile | 1 +
>> .../selftests/net/broadcast_ether_dst.sh | 82 +++++++++++++++++++
>> 2 files changed, 83 insertions(+)
>> create mode 100755 tools/testing/selftests/net/broadcast_ether_dst.sh
>>
>> diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
>> index b31a71f2b372..56ad10ea6628 100644
>> --- a/tools/testing/selftests/net/Makefile
>> +++ b/tools/testing/selftests/net/Makefile
>> @@ -115,6 +115,7 @@ TEST_PROGS += skf_net_off.sh
>> TEST_GEN_FILES += skf_net_off
>> TEST_GEN_FILES += tfo
>> TEST_PROGS += tfo_passive.sh
>> +TEST_PROGS += broadcast_ether_dst.sh
>> TEST_PROGS += broadcast_pmtu.sh
>> TEST_PROGS += ipv6_force_forwarding.sh
>>
>> diff --git a/tools/testing/selftests/net/broadcast_ether_dst.sh b/tools/testing/selftests/net/broadcast_ether_dst.sh
>> new file mode 100755
>> index 000000000000..865b5c7c8c8a
>> --- /dev/null
>> +++ b/tools/testing/selftests/net/broadcast_ether_dst.sh
>> @@ -0,0 +1,82 @@
>> +#!/bin/bash
>> +# SPDX-License-Identifier: GPL-2.0
>> +#
>> +# Author: Brett A C Sheffield <bacs@librecast.net>
>> +# Author: Oscar Maes <oscmaes92@gmail.com>
>> +#
>> +# Ensure destination ethernet field is correctly set for
>> +# broadcast packets
>> +
>> +source lib.sh
>> +
>> +CLIENT_IP4="192.168.0.1"
>> +GW_IP4="192.168.0.2"
>> +
>> +setup() {
>> + setup_ns CLIENT_NS SERVER_NS
>> +
>> + ip -net "${SERVER_NS}" link add link1 type veth \
>> + peer name link0 netns "${CLIENT_NS}"
>> +
>> + ip -net "${CLIENT_NS}" link set link0 up
>> + ip -net "${CLIENT_NS}" addr add "${CLIENT_IP4}"/24 dev link0
>> +
>> + ip -net "${SERVER_NS}" link set link1 up
>> +
>> + ip -net "${CLIENT_NS}" route add default via "${GW_IP4}"
>> + ip netns exec "${CLIENT_NS}" arp -s "${GW_IP4}" 00:11:22:33:44:55
>> +}
>> +
>> +cleanup() {
>> + rm -f "${CAPFILE}"
>> + ip -net "${SERVER_NS}" link del link1
>> + cleanup_ns "${CLIENT_NS}" "${SERVER_NS}"
>> +}
>> +
>> +test_broadcast_ether_dst() {
>> + local rc=0
>> + CAPFILE=$(mktemp -u cap.XXXXXXXXXX)
>> +
>> + echo "Testing ethernet broadcast destination"
>> +
>> + # start tcpdump listening for icmp
>> + # tcpdump will exit after receiving a single packet
>> + # timeout will kill tcpdump if it is still running after 2s
>> + timeout 2s ip netns exec "${CLIENT_NS}" \
>> + tcpdump -i link0 -c 1 -w "${CAPFILE}" icmp &> /dev/null &
>> + pid=$!
>> + sleep 0.1 # let tcpdump wake up
Here you could use slowwait checking for packet socket creation, to be
more robust WRT very slow env.
/P
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH net v3 1/2] net: ipv4: fix regression in local-broadcast routes
2025-08-27 6:23 [PATCH net v3 1/2] net: ipv4: fix regression in local-broadcast routes Oscar Maes
2025-08-27 6:23 ` [PATCH net v3 2/2] selftests: net: add test for destination in broadcast packets Oscar Maes
2025-08-27 16:09 ` [PATCH net v3 1/2] net: ipv4: fix regression in local-broadcast routes David Ahern
@ 2025-08-28 9:00 ` patchwork-bot+netdevbpf
2 siblings, 0 replies; 6+ messages in thread
From: patchwork-bot+netdevbpf @ 2025-08-28 9:00 UTC (permalink / raw)
To: Oscar Maes; +Cc: netdev, bacs, brett, kuba, davem, dsahern, regressions, stable
Hello:
This series was applied to netdev/net.git (main)
by Paolo Abeni <pabeni@redhat.com>:
On Wed, 27 Aug 2025 08:23:21 +0200 you wrote:
> Commit 9e30ecf23b1b ("net: ipv4: fix incorrect MTU in broadcast routes")
> introduced a regression where local-broadcast packets would have their
> gateway set in __mkroute_output, which was caused by fi = NULL being
> removed.
>
> Fix this by resetting the fib_info for local-broadcast packets. This
> preserves the intended changes for directed-broadcast packets.
>
> [...]
Here is the summary with links:
- [net,v3,1/2] net: ipv4: fix regression in local-broadcast routes
https://git.kernel.org/netdev/net/c/5189446ba995
- [net,v3,2/2] selftests: net: add test for destination in broadcast packets
(no matching commit)
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html
^ permalink raw reply [flat|nested] 6+ messages in thread
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2025-08-27 6:23 [PATCH net v3 1/2] net: ipv4: fix regression in local-broadcast routes Oscar Maes
2025-08-27 6:23 ` [PATCH net v3 2/2] selftests: net: add test for destination in broadcast packets Oscar Maes
2025-08-27 14:26 ` Brett A C Sheffield
2025-08-28 8:51 ` Paolo Abeni
2025-08-27 16:09 ` [PATCH net v3 1/2] net: ipv4: fix regression in local-broadcast routes David Ahern
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