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

 
 

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bug #27847: TCP fast retransmit error

Submitter:  hanhui <hanhui03>
Submitted:  Thu 29 Oct 2009 02:28:15 PM UTC
   
 
Category:  TCP Severity:  3 - Normal
Item Group:  Faulty Behaviour Status:  Duplicate
Privacy:  Public Assigned to:  None
Open/Closed:  Closed Planned 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>
Group Member
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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Depends on the following items: None found

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    Follow 2 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2009-10-29 kieranm Open/ClosedOpen Closed
        StatusNone Duplicate

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