buglwIP - A Lightweight TCP/IP stack - Bugs: bug #27847, TCP fast retransmit error

 
 

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bug #27847: TCP fast retransmit error

Submitted by:  hanhui <hanhui03>
Submitted on:  Thu 29 Oct 2009 02:28:15 PM UTC  
 
Category: TCPSeverity: 3 - Normal
Item Group: Faulty BehaviourStatus: Duplicate
Privacy: PublicAssigned to: None
Open/Closed: ClosedPlanned Release: None
lwIP version: CVS Head

Thu 29 Oct 2009 02:40:24 PM UTC, comment #1:

This is a duplicate of bug #27329

Kieran Mansley <kieranm>
Project Administrator
Thu 29 Oct 2009 02:28:15 PM UTC, original submission:

In recent days, I use a TCP echo server test lwip stack.
When I use a mass of data test and check the packet. I found many TCP "Out-Of-Order" and "Retransmit" packet(lwip send).
After detailed investigation, then I found the problem is in lwip's Fast Retransmit arithmetic.
lwip has error in decide duplicate ACK!
windows send large amounts of data, usually send consecutive packets and has same ACK(> 3 packets). then lwip decide that need fast retransmit.

These are the rules BSD stacks use to determine if an ACK is a
duplicate:

An ACK is a duplicate if:

(1) it has the same sequence number as the largest number we've seen,
(2) it has the same window as the last ACK,
(3) we have outstanding data that has not been ACKed
(4) The packet was not carrying any data.

hanhui <hanhui03>

 

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  • -unavailable- added by kieranm (Posted a comment)
  • -unavailable- added by hanhui03 (Submitted the item)
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    Follow 2 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Thu 29 Oct 2009 02:40:24 PM UTCkieranmOpen/ClosedOpen=>Closed
      StatusNone=>Duplicate

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