[lwip-devel] [bug #64780] sockets.c: avoid useless events on accept

[renzo davoli]

URL:
  <https://savannah.nongnu.org/bugs/?64780>

                 Summary: sockets.c: avoid useless events on accept
                   Group: lwIP - A Lightweight TCP/IP stack
               Submitter: rd235
               Submitted: Mon 16 Oct 2023 03:40:14 PM CEST
                Category: Contrib
                Severity: 3 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None
            lwIP version: 2.2.0


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Follow-up Comments:


-------------------------------------------------------
Date: Mon 16 Oct 2023 03:40:14 PM CEST By: renzo davoli <rd235>
In src/api/sockets.c, in function lwip_accept, around line 700 the code has
the following structure:

---

send pending RECVPLUS events  <---------------------------- XXX

if ((addr != NULL) && (addrlen != NULL)) {
  /* get the IP address and port of the remote host */
  err = netconn_peer(newconn, &naddr, &port);
  if (err != ERR_OK) {  <----------------------------------- YYY
    abort
    return -1
  }
  ...
  ... print debug msg including addr and port
} else
  ... print debug msg (without addr/port)
...
return newsock

----

the code at XXX can send events to a socket that will never exist because
netconn_peer fails at YYY

This patch simply moves the code at XXX after YYY so that events will be
generated only for sockets that will be "seen" by the caller.

So the modified code is just

-----

if ((addr != NULL) && (addrlen != NULL)) {
  /* get the IP address and port of the remote host */
  err = netconn_peer(newconn, &naddr, &port);
  if (err != ERR_OK) {  <----------------------------------- YYY
    abort
    return -1
  }
}

send pending RECVPLUS events  <---------------------------- XXX

if ((addr != NULL) && (addrlen != NULL)) {
  ... print debug msg including addr and port
} else
  ... print debug msg (without addr/port)
...
return newsock

----

It is a simple, clean, reasonable, and, as far as I can see, safe patch.






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File Attachments:


-------------------------------------------------------
Date: Mon 16 Oct 2023 03:40:14 PM CEST  Name:
socket_accept_avoid_useless_events.patch  Size: 2KiB   By: rd235

<http://savannah.nongnu.org/bugs/download.php?file_id=55245>

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