Re: [lwip-users] Problem with ftp session

[Thomas Taranowski]

On Jan 15, 2008 8:43 AM, Jonathan Larmour <address@hidden> wrote:
>
>
>
> Thomas Taranowski wrote:
> > 95% of the time my ftp/telnet apps work fine.  However, once in awhile I
> > get into a cycle where the tcp connections totally hose up.  The cause
> > appears to be related to the fact that in sys_mbox_fetch(), the
> > again:/goto again loop is spinning with wild abandon.  I put a counter
> > inside sys_mbox_fetch, which easily upticks into the several hundreds
> > within seconds of stack startup.  I've verified that the
> > sys_arch_mbox_fetch is returning sane values.  The odd thing is that
> > this only crops up once in awhile, and will stay around.  Last time I
> > thought I had a bad ethernet card, and switched test targets, and
> > everything started working.  However, now that I'm seeing it again on
> > different hardware/ethernet card combo, I'm concerned that I've got a
> > critical bug floating around somewhere.
> >
> > I've attached a wireshark capture of the link output.  It's a portion of
> > the ftp session.  You'll see that it basically works, but will spew out
> > loads of TCP Dup ACK, TCP Retransmits, and finally drops the connection
> > at the end with a series of 7 RSTs in a row.  Presumably I'm seeing
> > these cause the timers are firing way to fast.
> >
> > Note: This is a custom port of lwIP to an OS I'm working on.
> >
> > Any ideas on how to debug this, or what the issue is?  When this occurs,
> > I do have an inetd server start listening on several tcp ports at system
> > startup.
>
> Given sys_mbox_fetch is spinning, I would initially suspect your port's
> sys_arch_timeouts() call. It should return a list of timeouts only for the
> current thread.
>
> Jifl
> --

I do return a list of timeouts for only the current thread, but I'm
returning a pointer to the list of timeouts.  More timeouts *could* be
added while I'm in the midst of processing the list, potentially
creating a situation where I never return, which seems to be what is
happening.  Hmm, It's almost like it keeps rerunning stale timeout
handlers.  Anyway, thanks for the pointer.  I will check out that
area.