buglwIP - A Lightweight TCP/IP stack - Bugs: bug #42737, TCP_SND_QUEUELEN check in init.c...

 
 

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bug #42737: TCP_SND_QUEUELEN check in init.c (and comment in opt.h) are slighlty wrong

Submitted by:  Valery Ushakov <uwe>
Submitted on:  Sat 12 Jul 2014 01:04:44 AM UTC  
 
Category: TCPSeverity: 3 - Normal
Item Group: Faulty BehaviourStatus: Works For Me
Privacy: PublicAssigned to: Simon Goldschmidt <goldsimon>
Open/Closed: ClosedPlanned Release: None
lwIP version: git head

Thu 12 Feb 2015 08:46:33 PM UTC, comment #2:

On 2nd thought, I don't think there's a problem here: you might not be able to write the full TCP_SND_BUF, but that's how it's meant to be these are 2 independent limitations to prevent one connection from hogging too much memory. The comment in opt.h and check in init.c are to ensure you can write at least 2 segments (to not break the delayed ACK mechanisms). For this, TCP_MSS is correct.

Simon Goldschmidt <goldsimon>
Project AdministratorIn charge of this item.
Tue 02 Sep 2014 06:22:29 PM UTC, comment #1:

Any suggestions on how to fix this? I'm tempted to leave it as it is...

Simon Goldschmidt <goldsimon>
Project AdministratorIn charge of this item.
Sat 12 Jul 2014 01:04:44 AM UTC, original submission:

init.c checks that
since for each mss-sized pbuf with data there's another pbuf with header, hence the factor of two.

The problem is that TCP_MSS is static maximum and actual mss may be smaller - e.g. IPv6 header is larger than IPv4, so IPv6 mss is smaller. This leads to a situation where a write of full TCP_SND_BUF bytes does not fit into TCP_SND_QUEUELEN limit

Valery Ushakov <uwe>

 

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  • -unavailable- added by goldsimon (Posted a comment)
  • -unavailable- added by uwe (Submitted the item)
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    Follow 4 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Thu 12 Feb 2015 08:46:33 PM UTCgoldsimonStatusNeed Info=>Works For Me
      Assigned toNone=>goldsimon
      Open/ClosedOpen=>Closed
    Tue 02 Sep 2014 06:22:29 PM UTCgoldsimonStatusNone=>Need Info

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