Commit a2754d41 authored by Nick Mathewson's avatar Nick Mathewson 🦀
Browse files

Try using INT_MAX, not SOMAXCONN, to set listen() backlog. 

Fall back to SOMAXCONN if INT_MAX doesn't work.

We'd like to do this because the actual maximum is overrideable by the
kernel, and the value in the header file might not be right at all.
All implementations I can find out about claim that this is supported.

Fix for 9716; bugfix on every Tor.
parent a60d21a8

changes/bug9716

0 → 100644
+4 −0
Original line number Diff line number Diff line 
  o Bugfixes (performance):

    - Set the listen() backlog limit to the largest actually supported

      on the system, not to the value in a header file. Fixes bug 9716;

      bugfix on every released Tor.

src/or/connection.c

+22 −1
Original line number Diff line number Diff line
@@ -926,6 +926,27 @@ make_socket_reuseable(tor_socket_t sock) 
#endif

}



/** Max backlog to pass to listen.  We start at */

static int listen_limit = INT_MAX;



/* Listen on <b>fd</b> with appropriate backlog. Return as for listen. */

static int

tor_listen(tor_socket_t fd)

{

  int r;



  if ((r = listen(fd, listen_limit)) < 0) {

    if (listen_limit == SOMAXCONN)

      return r;

    if ((r = listen(fd, SOMAXCONN)) == 0) {

      listen_limit = SOMAXCONN;

      log_warn(LD_NET, "Setting listen backlog to INT_MAX connections "

               "didn't work, but SOMAXCONN did. Lowering backlog limit.");

    }

  }

  return r;

}



/** Bind a new non-blocking socket listening to the socket described

 * by <b>listensockaddr</b>.

 *
@@ -1009,7 +1030,7 @@ connection_listener_new(const struct sockaddr *listensockaddr, 
    }



    if (is_tcp) {

      if (listen(s,SOMAXCONN) < 0) {

      if (tor_listen(s) < 0) {

        log_warn(LD_NET, "Could not listen on %s:%u: %s", address, usePort,

                 tor_socket_strerror(tor_socket_errno(s)));

        tor_close_socket(s);