tcp: Handle errors from tcp_send_flag()

tcp_send_flag() can fail in two different ways:
   - tcp_prepare_flags() returns -ECONNRESET when getsockopt(TCP_INFO)
     fails: the socket is broken and the connection must be reset.
   - tcp_vu_send_flag() returns -EAGAIN when vu_collect() finds no
     available vhost-user buffers: this is a transient condition
     equivalent to a dropped packet on the wire.

Have tcp_vu_send_flag() return -EAGAIN instead of a bare -1 for the
buffer-unavailable case. Absorb -EAGAIN in the tcp_send_flag()
dispatcher so that callers only see fatal errors.

Check the return value at each call site and handle fatal errors:
   - in tcp_data_from_tap(), return -1 so the caller resets
   - in tcp_tap_handler(), goto reset
   - in tcp_timer_handler()/tcp_sock_handler()/tcp_conn_from_sock_finish(),
     call tcp_rst() and return
   - in tcp_tap_conn_from_sock(), set CLOSING flag, call
     FLOW_ACTIVATE() to avoid leaving the flow in TYPED state, and
     return
   - in tcp_connect_finish(), call tcp_rst() and return
   - in tcp_keepalive(), call tcp_rst() and continue the loop
   - in tcp_flow_migrate_target_ext(), goto fail

The call in tcp_rst_do() is left unchecked: we are already
resetting, and tcp_sock_rst() still needs to run regardless.

Link: https://bugs.passt.top/show_bug.cgi?id=194
Signed-off-by: Anshu Kumari <anskuma@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

0 files changed, 0 insertions, 0 deletions