Hi Guillaume, Thank you for sharing this fix!
> The mptcpify BPF prog upgrades eligible TCP sockets to MPTCP, but only > when the socket type is exactly SOCK_STREAM. Its update_socket_protocol() > hook runs on the raw type from userspace, before the socket core masks > it with SOCK_TYPE_MASK, so the type may still carry SOCK_CLOEXEC or > SOCK_NONBLOCK in its upper bits and the equality check fails. > > As a result, a socket(AF_INET, SOCK_STREAM | SOCK_CLOEXEC, 0) -- what > common libraries do by default -- is silently left as plain TCP. This > was hit in practice with curl. Since mptcpify.c is referenced as example > code for enabling MPTCP transparently, the same mistake is likely to be > copied into real deployments where it fails the same way and is hard to > diagnose. Good idea to fix this code in mptcpify.c, which is indeed used as a reference, and ends up in real deployments. The modifications look good to me: Reviewed-by: Matthieu Baerts (NGI0) <[email protected]> -- Matthieu Baerts (NGI0) <[email protected]>
