[altq 805] Re: help on using RED & mark_ecn

[Kenjiro Cho <kjc@csl.sony.co.jp>]

Shiv Saxena wrote:
> I am new to ALTQ. I successfully compiled ALTQ patches for FreeBSD 4.2 and
> compiled it using ALTQ, ALTQ_RED and ALTQ_ECN for a router.
> 
> I also manually patched the source and sink sources to use ECN as given in
> an earlier ALTQ patch. Now when I run this setup, with multiple (5) TCP
> streams between source and sink being routed through the router, the q_len
> remains <= 1 and the packet never gets marked or dropped. If I do a flood
> ping to the router, then the q_len (as shown by altqd) increases to
> numbers between 7 & 25.
> 
> However, none of the packets are marked with CE bit set in the IP header
> (even though I am sure that the ECT bit is being set correctly by the
> source).
> 
> Two questions, (1). Can I simply use RED or do I have to combine RED with
> CBQ etc. (2). I am only looking for the router to set the CE bit in the IP
> header of tcp packets. Will flooding ping ever be able to achieve this?

There was a bug in the ECN support for FreeBSD-4.2.
It was fixed as follows:

kjc         2001/03/01 18:29:50 JST

  Modified files:
    freebsd4/sys/net     if_ethersubr.c 
  Log:
  always call altq_etherclassify() when altq is enabled
  to set packet attribute.
  ECN support in standalone RED/RIO doesn't need a classifier
  but uses address family and header info.
  
  reported by Martin Karsten <Martin.Karsten@KOM.tu-darmstadt.de>
  
  Revision  Changes    Path
  1.13      +4 -3      kame/freebsd4/sys/net/if_ethersubr.c

You can get a diff from
http://orange.kame.net/dev/cvsweb.cgi/kame/freebsd4/sys/net/if_ethersubr.c

-Kenjiro