tree a133aebf83ec36a0c935e4cc3662cf0e76f11051
parent 7b8aac443988345d4e6309aa9bf77e66f81e0b2c
author Amaury Denoyelle <adenoyelle@haproxy.com> 1677147518 +0100
committer Amaury Denoyelle <adenoyelle@haproxy.com> 1677577885 +0100

MEDIUM: quic: improve fatal error handling on send

Send is conducted through qc_send_ppkts() for a QUIC connection. There
is two types of error which can be encountered on sendto() or affiliated
syscalls :
* transient error. In this case, sending is simulated with the remaining
  data and retransmission process is used to have the opportunity to
  retry emission
* fatal error. If this happens, the connection should be closed as soon
  as possible. This is done via qc_kill_conn() function. Until this
  patch, only ECONNREFUSED errno was considered as fatal.

Modify the QUIC send API to be able to differentiate transient and fatal
errors more easily. This is done by fixing the return value of the
sendto() wrapper qc_snd_buf() :
* on fatal error, a negative error code is returned. This is now the
  case for every errno except EAGAIN, EWOULDBLOCK, ENOTCONN, EINPROGRESS
  and EBADF.
* on a transient error, 0 is returned. This is the case for the listed
  errno values above and also if a partial send has been conducted by
  the kernel.
* on success, the return value of sendto() syscall is returned.

This commit will be useful to be able to handle transient error with a
quic-conn owned socket. In this case, the socket should be subscribed to
the poller and no simulated send will be conducted.

This commit allows errno management to be confined in the quic-sock
module which is a nice cleanup.

On a final note, EBADF should be considered as fatal. This will be the
subject of a next commit.

This should be backported up to 2.7.