Hi Amaury, Thank you for the review. Here are my answers, with two questions before I send a v2.
1. OK for both: src will come before dst, and addr will be renamed to dst. 2. OK, the new emission function will be introduced without the EINTR loop, which will come in a separate patch at the end of the series. 3. The listener socket is already non-blocking, as fd_set_nonblock() is called in sock_inet_bind_receiver(), including for inherited FDs, so MSG_DONTWAIT does not change anything here. As for MSG_NOSIGNAL, send(2) only mentions it for stream-oriented sockets, and haproxy ignores SIGPIPE anyway (signal_register_fct(SIGPIPE, NULL, 0) in haproxy.c). So I would rather drop both flags, which keeps the exact behavior of the current sendto() calls, and add a comment stating that a datagram is simply lost when the socket buffer is full, as there is no connection to retry its emission later. Would that be fine with you? If you prefer to keep MSG_DONTWAIT for consistency with qc_snd_buf(), I can do that instead, with the same comment. 4. Your approach is clearer, so I will follow it, including the quic_lstnr_sock_send() name. A first patch will make send_retry() and send_version_negotiation() take the listener (send_stateless_reset() already does), and quic_lstnr_sock_send() will take it as well and check quic_lstnr_may_set_src() itself. Callers will then always pass dgram->daddr as source, the same way they already pass dgram->saddr as destination. The v2 would thus be: listener argument, quic_lstnr_sock_send(), the three fixes, the regtest, and the EINTR retry last. There is also one behavior change to report. When a client targets an IPv4 broadcast address (255.255.255.255 or a subnet broadcast), Linux rejects it as an explicit source address and sendmsg() fails with EINVAL. In connection socket mode, such a connection currently works, even with Retry, because the connection socket is bound on the broadcast address and the kernel then selects the source address itself. With the series, Retry, VN and Stateless Reset are no longer emitted to these clients. In listener socket mode, these connections already fail without the series, as qc_snd_buf() hits the same EINVAL. I do not think this matters in practice, but if you prefer, quic_lstnr_sock_send() could retry once without source address on EINVAL, so that emission never regresses. What do you think? Regards, Yeonggi Kim
