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

[Jakub Kicinski]

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