Re: TCP LAST-ACK state broken in 2.4.17-pre2 [NEW DATA]

Mika Liljeberg
2001-12-18T20:22:54Z

kuznet@ms2.inr.ac.ru wrote:
>
> Hello!
>
> > from the SYN exchange (about 200 ms). So, something is wrong?
>
> Well, the guess was right and this is pleasant.

Yes. We also saw a case, where the RTO was quite high but not quite 120,
so we got exactly one retransmission.

> The only minor :-) question remained is to guess how rto could happen
> to be at this value. I will think. Well, if you have some guesses,
> please, tell me.

Sorry, I'm not really trying to debug Linux so I haven't given it much
thought. We're exercising retransmission algorithms with a packet loss
ratio of 5% if that's any help.

> Is this intel btw?

It's ARM in little endian mode.

> I just see that other side
> sends bogus misaligned tcp options... not a problem, but it can
> be reason of funnyies with some probability.

Heh, they're not bogus, just differently aligned. :) This is an
implementation where packet processing latency is not highest
item on the list of optimization targets.

Now that you mention it, tcp_parse_options() in input.c seems to expect
that the timestamps are word aligned, which is not the case here, and a
false assumption in any case. I would have expected a bus error for
that, unless the pointer cast generates code that magically word aligns
the resulting pointer...

Cheers,

MikaL