netdev - [PATCH v1 net-next 01/12] selftest: packetdrill: Require explicit setsockopt(TCP

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Message-ID: <20250926212929.1469257-2-kuniyu@google.com>
Date: Fri, 26 Sep 2025 21:28:55 +0000
From: Kuniyuki Iwashima <kuniyu@...gle.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, Kuniyuki Iwashima <kuniyu@...gle.com>, 
	Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org
Subject: [PATCH v1 net-next 01/12] selftest: packetdrill: Require explicit setsockopt(TCP_FASTOPEN).

To enable TCP Fast Open on a server, net.ipv4.tcp_fastopen must
have 0x2 (TFO_SERVER_ENABLE), and we need to do either

  1. Call setsockopt(TCP_FASTOPEN) for the socket
  2. Set 0x400 (TFO_SERVER_WO_SOCKOPT1) additionally to net.ipv4.tcp_fastopen

The default.sh sets 0x70403 so that each test does not need setsockopt().
(0x1 is TFO_CLIENT_ENABLE, and 0x70000 is ...???)

However, some tests overwrite net.ipv4.tcp_fastopen without
TFO_SERVER_WO_SOCKOPT1 and forgot setsockopt(TCP_FASTOPEN).

For example, pure-syn-data.pkt [0] tests non-TFO servers unintentionally,
except in the first scenario.

To prevent such an accident, let's require explicit setsockopt().

TFO_CLIENT_ENABLE will be restored when client tests are added.

Link: https://github.com/google/packetdrill/blob/bfc96251310f/gtests/net/tcp/fastopen/server/opt34/pure-syn-data.pkt #[0]
Signed-off-by: Kuniyuki Iwashima <kuniyu@...gle.com>
---
 tools/testing/selftests/net/packetdrill/defaults.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/net/packetdrill/defaults.sh b/tools/testing/selftests/net/packetdrill/defaults.sh
index 1095a7b22f44..6b0ca8e738a2 100755
--- a/tools/testing/selftests/net/packetdrill/defaults.sh
+++ b/tools/testing/selftests/net/packetdrill/defaults.sh
@@ -51,7 +51,7 @@ sysctl -q net.ipv4.tcp_pacing_ss_ratio=200
 sysctl -q net.ipv4.tcp_pacing_ca_ratio=120
 sysctl -q net.ipv4.tcp_notsent_lowat=4294967295 > /dev/null 2>&1
 
-sysctl -q net.ipv4.tcp_fastopen=0x70403
+sysctl -q net.ipv4.tcp_fastopen=0x2
 sysctl -q net.ipv4.tcp_fastopen_key=a1a1a1a1-b2b2b2b2-c3c3c3c3-d4d4d4d4
 
 sysctl -q net.ipv4.tcp_syncookies=1
-- 
2.51.0.536.g15c5d4f767-goog