Date: Fri, 27 Oct 2006 15:14:52 +0200
From: Olivier MATZ <olivier.matz@6wind.com>
Subject: [users:00251] Computed checksum is wrong
To: users@tahi.org
Message-Id: <4542064C.6000302@6wind.com>
X-Mail-Count: 00251

Hi all,

I have a FAIL in ready logo phase2 host tests :

Here is a part of the log, as you can see checksum is not the one expected :

| | ICMPv6_ParameterProblem         (length:64)
| | | Type                             = 4
| | | Code                             = 1
| | | Checksum                         = 65535 calc(0)
[...]
ng compare _ICMPV6_icmperr.Checksum received:65535 = 0


This fail occurs in :
Section 1: RFC 2460 - IPv6 Specification
TEST 13, Part A: Unrecognized Next Header in Extension Header (Multiple
Values)

In this test, multiple values of Next Header are tested, so the nut
generates each time a different packet with a different checksum... on
my nut I have no luck, the processed checksum is 0.

But as you know (from RFC):
     o  Unlike IPv4, when UDP packets are originated by an IPv6 node,
         the UDP checksum is not optional.  That is, whenever
         originating a UDP packet, an IPv6 node must compute a UDP
         checksum over the packet and the pseudo-header, and, if that
         computation yields a result of zero, it must be changed to hex
         FFFF for placement in the UDP header.  IPv6 receivers must
         discard UDP packets containing a zero checksum, and should log
         the error.

I made a patch that fixes the problem, but I'm not really sure of it,
since I'm not very familiar with TAHI development. Can someone have a
look at it ? There are 2 fixes in it :
- first I replaced '~checksum' by 0xFFFF, because ~checksum is
0xFFFFFFFF as it is an uint32_t.
- I also invert the optionable test, because I think we should replace
the value only if the checksum field is not an option.

Olivier


	
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