[PATCH net] selftests: cmsg_ipv6: repeat the exact packet

[PATCH net] selftests: cmsg_ipv6: repeat the exact packet

[Jakub Kicinski]

cmsg_ipv6 test requests tcpdump to capture 4 packets,
and sends until tcpdump quits. Only the first packet
is "real", however, and the rest are basic UDP packets.
So if tcpdump doesn't start in time it will miss
the real packet and only capture the UDP ones.

This makes the test fail on slow machine (no KVM or with
debug enabled) 100% of the time, while it passes in fast
environments.

Repeat the "real" / expected packet.

Fixes: 9657ad09e1fa ("selftests: net: test IPV6_TCLASS")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
CC: shuah@kernel.org
CC: linux-kselftest@vger.kernel.org
---
 tools/testing/selftests/net/cmsg_ipv6.sh | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/net/cmsg_ipv6.sh b/tools/testing/selftests/net/cmsg_ipv6.sh
index f30bd57d5e38..8bc23fb4c82b 100755
--- a/tools/testing/selftests/net/cmsg_ipv6.sh
+++ b/tools/testing/selftests/net/cmsg_ipv6.sh
@@ -89,7 +89,7 @@ for ovr in setsock cmsg both diff; do
 	check_result $? 0 "TCLASS $prot $ovr - pass"
 
 	while [ -d /proc/$BG ]; do
-	    $NSEXE ./cmsg_sender -6 -p u $TGT6 1234
+	    $NSEXE ./cmsg_sender -6 -p $p $m $((TOS2)) $TGT6 1234
 	done
 
 	tcpdump -r $TMPF -v 2>&1 | grep "class $TOS2" >> /dev/null
@@ -126,7 +126,7 @@ for ovr in setsock cmsg both diff; do
 	check_result $? 0 "HOPLIMIT $prot $ovr - pass"
 
 	while [ -d /proc/$BG ]; do
-	    $NSEXE ./cmsg_sender -6 -p u $TGT6 1234
+	    $NSEXE ./cmsg_sender -6 -p $p $m $LIM $TGT6 1234
 	done
 
 	tcpdump -r $TMPF -v 2>&1 | grep "hlim $LIM[^0-9]" >> /dev/null
-- 
2.43.0

Re: [PATCH net] selftests: cmsg_ipv6: repeat the exact packet

[Simon Horman]

On Sun, Feb 04, 2024 at 08:56:18AM -0800, Jakub Kicinski wrote:
> cmsg_ipv6 test requests tcpdump to capture 4 packets,
> and sends until tcpdump quits. Only the first packet
> is "real", however, and the rest are basic UDP packets.
> So if tcpdump doesn't start in time it will miss
> the real packet and only capture the UDP ones.
> 
> This makes the test fail on slow machine (no KVM or with
> debug enabled) 100% of the time, while it passes in fast
> environments.
> 
> Repeat the "real" / expected packet.
> 
> Fixes: 9657ad09e1fa ("selftests: net: test IPV6_TCLASS")
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>

I'm not sure if it is important, but doesn't this also:

Fixes: 05ae83d5a4a2 ("selftests: net: test IPV6_HOPLIMIT")

In any case, this looks good to me.

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

Re: [PATCH net] selftests: cmsg_ipv6: repeat the exact packet

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by David S. Miller <davem@davemloft.net>:

On Sun,  4 Feb 2024 08:56:18 -0800 you wrote:
> cmsg_ipv6 test requests tcpdump to capture 4 packets,
> and sends until tcpdump quits. Only the first packet
> is "real", however, and the rest are basic UDP packets.
> So if tcpdump doesn't start in time it will miss
> the real packet and only capture the UDP ones.
> 
> This makes the test fail on slow machine (no KVM or with
> debug enabled) 100% of the time, while it passes in fast
> environments.
> 
> [...]

Here is the summary with links:
  - [net] selftests: cmsg_ipv6: repeat the exact packet
    https://git.kernel.org/netdev/net/c/4b00d0c513da

You are awesome, thank you!
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