From: David Monro <davidm@davidmonro•net>
To: netdev@vger•kernel.org
Cc: asun@darksunrising•com
Subject: Re: cassini driver and IPv6
Date: Mon, 10 Mar 2008 15:51:22 +1030 [thread overview]
Message-ID: <47D4C552.5050704@davidmonro.net> (raw)
In-Reply-To: <20051114.214848.83997631.davem@davemloft.net>
Well, I thought I would take another look at this, since I saw lots of
cassini-related code going into the kernel and its been some time since
I last played with this...
I'm using a board with Natsemi Saturn chips (one of the gigaswifts with
2xGig ether and 2x scsi), on a little-endian PC rather than a sparc box
(not that that should matter...). _Most_ IPV6 packets don't seem to get
checksummed correctly (they trigger the eth1: hw csum failure message
and a traceback as follows:
[<c010505a>] show_trace_log_lvl+0x1a/0x30
[<c0105a72>] show_trace+0x12/0x20
[<c010642a>] dump_stack+0x6a/0x70
[<c0292f01>] netdev_rx_csum_fault+0x31/0x40
[<c028f300>] __skb_checksum_complete_head+0x60/0x70
[<c028f31b>] __skb_checksum_complete+0xb/0x10
[<e0fba769>] tcp_v6_rcv+0x459/0x920 [ipv6]
[<e0f9aa4f>] ip6_input_finish+0x12f/0x340 [ipv6]
[<e0f9ac7f>] ip6_input+0x1f/0x60 [ipv6]
[<e0f9af55>] ipv6_rcv+0x1f5/0x340 [ipv6]
[<c0292b54>] netif_receive_skb+0x364/0x510
[<c02958f6>] process_backlog+0x66/0xd0
[<c02953ee>] net_rx_action+0x15e/0x210
[<c0123f52>] __do_softirq+0x52/0xb0
[<c0123ff6>] do_softirq+0x46/0x50
[<c012445c>] irq_exit+0x6c/0x80
[<c01065b3>] do_IRQ+0x53/0x90
[<c0104afa>] common_interrupt+0x2e/0x34
[<c0116971>] do_page_fault+0xa1/0x5f0
[<c03081e2>] error_code+0x6a/0x70
).
(Not all packets trigger it; eg I sent a ping6 with a length of 2000,
and as far as I can tell only the 2nd packet in each ping triggers the
failure - odd. Does it depend on the v6 extension headers present or
something I wonder. Actually, how on earth does the hardware produce the
pseudo header for tcp? And even odder - how could it possibly go wrong
with non-tcp packets like ping?)
Has anyone else ever tested a saturn (or actually any cassini device)
using ipv6?
I've spent a while looking at the packet parser stuff but I have only a
vague idea what it is doing and am certainly not in a position to debug
it. My current solution is simply to only do the checksumming stuff at
the bottom of cas_rx_process_pkt if ntohs(skb->protocol) == 0x0800 (ie,
IPv4), else set skb->csum to CHECKSUM_NONE, which is kinda dirty. If
someone with a non-saturn cassini can confirm that they don't get hw
csum errors with ipv6, then I'd have to assume a saturn-only hardware
bug and could wrap it with (cp->cas_flags & CAS_FLAG_SATURN) as well.
Does this seem reasonable?
Cheers,
David
David S. Miller wrote:
> From: David Monro <davidm@davidmonro•net>
> Date: Mon, 14 Nov 2005 13:02:42 +1030
>
>> I don't know if it just needs to be told not to calulate the checksums
>> for v6 packets, or what.
>
> It generates a generic checksum calculation on all packets,
> similarly to the Sun GEM chip, which ought to be totally
> protocol agnostic.
>
> The Cassini is a very complex chip, so debugging this without docs
> will be a chore. There are many things that influence how this chip
> looks at the packet, including a packet parsing engine which tells it
> where to split packets up into header and data portions for zero-copy
> stuff.
>
> Special versions of this packet parser are needed to workaround bugs
> in certain revisions of the chip, and I bet there are buffer alignment
> constraints on receive and other odd things that need to be right.
>
> The only thing I can do to work on this bug is to use the driver
> source, and reproduce the bug here and just tinker around, which
> you can also do. :-)
>
>
next parent reply other threads:[~2008-03-10 6:17 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <4377F74A.8090707@davidmonro.net>
[not found] ` <20051114.214848.83997631.davem@davemloft.net>
2008-03-10 5:21 ` David Monro [this message]
2008-03-10 9:04 ` cassini driver and IPv6 David Monro
2008-05-22 0:09 ` David Miller
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