buglwIP - A Lightweight TCP/IP stack - Bugs: bug #48563, TCP: simultaneous open not...

 
 

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bug #48563: TCP: simultaneous open not supported

Submitted by:  Joel Cunningham <jcunningham>
Submitted on:  Tue 19 Jul 2016 07:08:48 PM UTC  
 
Category: TCPSeverity: 3 - Normal
Item Group: Faulty BehaviourStatus: Duplicate
Privacy: PublicAssigned to: Simon Goldschmidt <goldsimon>
Open/Closed: ClosedPlanned Release: None
lwIP version: git head

Tue 19 Jul 2016 08:22:17 PM UTC, comment #2:

Thanks for the follow up. I agree I can't think of a real-world use case either

Joel Cunningham <jcunningham>
Project Member
Tue 19 Jul 2016 07:22:15 PM UTC, comment #1:

Actually, this is a duplicate to bug #35845 (please continue there if there's anything to add). That one was closed as simultaneous open is theroetically possible, but given the fact that most (if not all) protocols have client & server roles, there's no real use for simultaneous open.

Of course, if there's a real requirement, I'm still open to support this, but until now, there wasn't.

Simon Goldschmidt <goldsimon>
Project AdministratorIn charge of this item.
Tue 19 Jul 2016 07:08:48 PM UTC, original submission:

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

Joel Cunningham <jcunningham>
Project Member

 

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  • -unavailable- added by goldsimon (Posted a comment)
  • -unavailable- added by jcunningham (Submitted the item)
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    Follow 3 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Tue 19 Jul 2016 07:22:15 PM UTCgoldsimonStatusNone=>Duplicate
      Assigned toNone=>goldsimon
      Open/ClosedOpen=>Closed

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