LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Petr Vandrovec <vandrove@vc.cvut.cz>
To: Pierre Ossman <drzeus-list@drzeus.cx>
Cc: LKML <linux-kernel@vger.kernel.org>
Subject: Re: NCPFS and brittle connections
Date: Thu, 25 Jan 2007 00:22:45 -0800	[thread overview]
Message-ID: <45B868D5.9070409@vc.cvut.cz> (raw)
In-Reply-To: <45B7D750.1040501@drzeus.cx>

Pierre Ossman wrote:
> Petr Vandrovec wrote:
>> Hello,
>>   create test scenario where first transmit of NCP request is lost by
>> network, and before resend you kill this process.  So it stops
>> resending, but local sequence count is already incremented.  Then when
>> next process tries to access ncpfs, server will ignore its requests as
>> it expects packet with sequence X, while packet with sequence X+1
>> arrived.
> 
> Figured something along those lines, but I couldn't find any docs on the
> protocol so I wasn't sure. You wouldn't happen to have any pointers to
> such docs?

You can download NCP documentation from Novell website.  Or you could, 
couple of months ago.  Unfortunately that documentation just describes 
different NCP calls, not transport - to my knowledge transport layer was 
never documented outside of Novell.

>> And unfortunately it is not possible to simple not increment sequence
>> number unless you get reply - when server receives two packets with
>> same sequence number, it simple resends answer it gave to first
>> request, without looking at request's body at all.  So in this case
>> server would answer, but would gave you bogus answer.
> 
> This sounds promising though. In that case it wouldn't be necessary to
> store the entire request, just the sequence number, right?

Not quite.  If packet signatures are on then server needs to know packet 
you sent so it can correctly compute secret used for next packet (it is 
function of old secret, and data in current packet).  As current 
signatures implementation implement only partial signatures, you need 
just first 64bytes of the packet same - but at that point it may be 
better to just resend packet completely, as write request with correct 
file handle, length, and offset, but with only ~50 bytes of valid data 
is going to do lot of damage on the server.  So I would recommend 
resending original request...
							Petr



  reply	other threads:[~2007-01-25  8:22 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-04 15:04 Pierre Ossman
2007-01-04 17:26 ` Petr Vandrovec
2007-01-04 19:30   ` Pierre Ossman
2007-01-05  7:43     ` Petr Vandrovec
2007-01-24 15:27       ` Pierre Ossman
2007-01-24 17:49         ` Petr Vandrovec
2007-01-24 22:01           ` Pierre Ossman
2007-01-25  8:22             ` Petr Vandrovec [this message]
2007-01-25 10:20               ` Pierre Ossman
2007-02-01  8:39                 ` Pierre Ossman
2007-02-04  6:00                 ` Petr Vandrovec
2007-02-04 17:17                   ` Pierre Ossman
2007-02-05  3:50                     ` Petr Vandrovec
2007-02-19 10:37                       ` Pierre Ossman
2007-02-20  2:47                         ` Petr Vandrovec
2007-02-20  6:37                           ` Pierre Ossman

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=45B868D5.9070409@vc.cvut.cz \
    --to=vandrove@vc.cvut.cz \
    --cc=drzeus-list@drzeus.cx \
    --cc=linux-kernel@vger.kernel.org \
    --subject='Re: NCPFS and brittle connections' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).