buglwIP - A Lightweight TCP/IP stack - Bugs: bug #51663, tcp_out rto: delay re-transmission...

 
 

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bug #51663: tcp_out rto: delay re-transmission earlier if link writes are deferred.

Submitted by:  Douglas <ourairquality>
Submitted on:  Sat 05 Aug 2017 09:37:33 AM UTC  
 
Category: TCPSeverity: 3 - Normal
Item Group: Change RequestStatus: Fixed
Privacy: PublicAssigned to: Simon Goldschmidt <goldsimon>
Open/Closed: ClosedPlanned Release: None
lwIP version: git head

Tue 08 Aug 2017 09:33:32 PM UTC, comment #2:

Thank you. Yes I was seeing delays of 20 seconds on the wifi TX link layer, and the pre-existing pbuf ref guard was needed. The etharp layer can also queue buffers (defer transmission) and that also tickles this code path, so it is not exclusive to marginal wifi links.

Douglas <ourairquality>
Tue 08 Aug 2017 09:03:01 PM UTC, comment #1:

Did you actually see this in real life or is this from reading the code only?

Whatever, I've pushed your patch plus some additions...

Simon Goldschmidt <goldsimon>
Project AdministratorIn charge of this item.
Sat 05 Aug 2017 09:37:33 AM UTC, original submission:

There is already a guard in tcp_output_segment() for a pbuf still being referenced by the netif driver due to deferred transmission, however the callers are modifying state even when this gives up.

It seems cleaner to have the callers guard this case and avoid modifying their state.

tcp_rexmit_rto() might better avoid re-transmission of any segments if any of the unacked segments are deferred, to avoid loading the link further if it is struggling to flush its buffered writes. Link level queues can be limited on some devices and need spares for link management.

Douglas <ourairquality>

 

 

Depends on the following items: None found

Items that depend on this one: None found

 

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  • -unavailable- added by goldsimon (Posted a comment)
  • -unavailable- added by ourairquality (Submitted the item)
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    Follow 5 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Tue 08 Aug 2017 09:03:01 PM UTCgoldsimonStatusNone=>Fixed
      Assigned toNone=>goldsimon
      Open/ClosedOpen=>Closed
    Sat 05 Aug 2017 10:28:14 AM UTCourairqualityAttached File-=>Added 0002-tcp_out-rto-delay-re-transmission-earlier-if-link-wr.patch, #41423
    Sat 05 Aug 2017 09:37:33 AM UTCourairqualityAttached File-=>Added 0001-tcp_out-rto-delay-re-transmission-earlier-if-link-wr.patch, #41421

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