[lwip-devel] [bug #48563] TCP: simultaneous open not supported

[Joel Cunningham]

URL:
  <http://savannah.nongnu.org/bugs/?48563>

                 Summary: TCP: simultaneous open not supported
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: jcunningham
            Submitted on: Tue 19 Jul 2016 07:08:48 PM GMT
                Category: TCP
                Severity: 3 - Normal
              Item Group: Faulty Behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None
            lwIP version: git head

    _______________________________________________________

Details:

During static analysis of the code referenced in patch #9039, I've noticed
that LwIP's TCP implementation doesn't seem to handle simultaneous opens.

A simultaneous open is when two hosts perform an active open at the same time,
going from SYN-SENT to SYN-RCVD by receiving only a SYN packet (no ACK flag is
set). This results in a single TCP connection between the two hosts

This is described in RFC 793, page 32:
https://tools.ietf.org/html/rfc793#page-32.

RFC 1122 (page 87) https://tools.ietf.org/html/rfc1122#page-87, further
clarifies simultaneous opens as a MUST and addresses errata from 793

In our handling of SYN-SENT (in tcp_process) we only check for both SYN and
ACK flags, not making it possible to only receive a SYN





    _______________________________________________________

Reply to this item at:

  <http://savannah.nongnu.org/bugs/?48563>

_______________________________________________
  Message sent via/by Savannah
  http://savannah.nongnu.org/