netdev - Re: panics in tcp

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Date:	Sun, 02 Jun 2013 22:41:02 -0500
From:	Rob Herring <robherring2@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	netdev@...r.kernel.org
Subject: Re: panics in tcp_ack

On 06/02/2013 10:32 PM, Eric Dumazet wrote:
> On Sun, 2013-06-02 at 22:18 -0500, Rob Herring wrote:
> 
>> Ah, missed that there are 2 versions of skb_transport_header. So on
>> 32-bit it is skb->transport_header.
>>
>> Here's the ARM disassembly:
>>
>> c040796c <tcp_rcv_established>:
>> c040796c:       e92d45f0        push    {r4, r5, r6, r7, r8, sl, lr}
>> c0407970:       e1a06002        mov     r6, r2
>> c0407974:       e5d023e4        ldrb    r2, [r0, #996]  ; 0x3e4
>> c0407978:       e1a05001        mov     r5, r1
>> c040797c:       e5901344        ldr     r1, [r0, #836]  ; 0x344
>> c0407980:       e24dd014        sub     sp, sp, #20
>> c0407984:       e7c0201f        bfc     r2, #0, #1
>> c0407988:       e5c023e4        strb    r2, [r0, #996]  ; 0x3e4
>> panic>c040798c:       e596200c        ldr     r2, [r6, #12]
>>
>> r6 is NULL. r6 came from r2 which is the 3rd function argument.
>>
>> The 3rd arg is tcp_hdr(skb) which is skb->transport_header.
>>
>> Rob
> 
> Interesting. transport header should be set in IP stack before TCP.
> 
> What is the driver delivering this packet ?

Calxeda xgmac

> Do you have commit fda55eca5a33f33ffcd4192c6b2d75179714a52c
> ("net: introduce skb_transport_header_was_set()")

No.

Rob

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