From: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Date: Sun, 09 Mar 2014 19:47:55 +0000
> On Wed, 2014-03-05 at 14:49 +0800, Hayes Wang wrote:
>> Support hw IPv6 checksum for TCP and UDP packets.
>>
>> Note that the hw has the limitation of the range of the transport
>> offset. Besides, the TCP Pseudo Header of the IPv6 TSO of the hw
>> bases on the Microsoft document which excludes the packet length.
>>
>> Signed-off-by: Hayes Wang <hayeswang@xxxxxxxxxxx>
>> ---
>> drivers/net/usb/r8152.c | 107 ++++++++++++++++++++++++++++++++++++++++++++++--
>> 1 file changed, 104 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
>> index 8f6d0f8..8e208f30 100644
>> --- a/drivers/net/usb/r8152.c
>> +++ b/drivers/net/usb/r8152.c
> [...]
>> +static int msdn_giant_send_check(struct sk_buff *skb)
>> +{
>> + const struct ipv6hdr *ipv6h;
>> + struct tcphdr *th;
>> +
>> + ipv6h = ipv6_hdr(skb);
>> + th = tcp_hdr(skb);
>> +
>> + th->check = 0;
>> + th->check = ~tcp_v6_check(0, &ipv6h->saddr, &ipv6h->daddr, 0);
> [...]
>
> I think you need to call skb_cow_head() before editing the header here.
This made me notice that several drivers open-code this:
if (skb_header_cloned(skb) &&
pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
goto drop;
If someone is looking for a quick cleanup, transforming these
to use skb_cow_head() would be nice. That way other driver
authors will be less likely to copy the expanded code.
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