RE: [PATCH net-next v3] tcp: add TCP_ECN and TCP_ECN_OPTION socket options

-----Original Message-----
From: Jakub Kicinski <kuba@kernel.org>
Sent: 16 September 2026 05:28
To: Irlanki Sandeep <redacted>
Cc: netdev@vger.kernel.org; bpf@vger.kernel.org; davem@davemloft.net;
edumazet@google.com; pabeni@redhat.com; ncardwell@google.com;
ast@kernel.org; daniel@iogearbox.net; andrii@kernel.org; corbet@lwn.net;
linux-kernel@vger.kernel.org; lorenzo@google.com; maze@google.com;
sporeba@google.com; motomuman@google.com; srihari.k@samsung.com;
g.pokhra@samsung.com; r.kumawat@samsung.com;
raj.kumars@samsung.com; ts413.lee@samsung.com
Subject: Re: [PATCH net-next v3] tcp: add TCP_ECN and TCP_ECN_OPTION
socket options

On Fri, 11 Sep 2026 14:41:48 +0530 Irlanki Sandeep wrote:

quoted

Currently, ECN and Accurate ECN (AccECN) configurations in the Linux
kernel are controlled globally via the net.ipv4.tcp_ecn and
net.ipv4.tcp_ecn_option sysctl variables. This global approach lacks
the granularity required for modern multi-application runtimes.

CI (bpf-ci) reports a failure to build tools/testing/selftests/bpf on all

tested

toolchains/architectures (x86-64 gcc-15, x86-64 llvm-21, s390x gcc-15,

aarch64

gcc-15) after this series. The build breaks in
progs/setget_sockopt.c:

    progs/setget_sockopt.c:67:11: error: use of undeclared identifier
'TCP_ECN'
            { .opt = TCP_ECN, .new = 3, .expected = 3, .restore = 255, },
    progs/setget_sockopt.c:68:11: error: use of undeclared identifier
'TCP_ECN_OPTION'
            { .opt = TCP_ECN_OPTION, .new = 2, .expected = 2, .restore =

255, },

Thanks for the report.

TCP_ECN and TCP_ECN_OPTION have been defined in
tools/testing/selftests/bpf/progs/bpf_tracing_net.h to resolve the
compilation failure in progs/setget_sockopt.c.

This has been addressed in v4:
https://lore.kernel.org/all/20260916050255.1379192-1-irlanki.s@samsung.com/ (local)

Thanks,
Sandeep.