netdev - Re: [PATCHv2 1/2 ] {xfrm, sctp} Stick to software crc32 even if hardware is capable of that

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Date:	Fri, 11 Oct 2013 13:12:03 -0400
From:	Vlad Yasevich <vyasevich@...il.com>
To:	Fan Du <fan.du@...driver.com>, Neil Horman <nhorman@...driver.com>,
	steffen.klassert@...unet.com, davem@...emloft.net
CC:	netdev@...r.kernel.org
Subject: Re: [PATCHv2 1/2 ] {xfrm, sctp} Stick to software crc32 even if hardware
 is capable of that

On 10/11/2013 10:04 AM, Vlad Yasevich wrote:
> On 10/11/2013 03:05 AM, Fan Du wrote:
>>
>>
>> On 2013年10月10日 21:11, Neil Horman wrote:
>>> On Thu, Oct 10, 2013 at 01:51:36PM +0800, Fan Du wrote:
>>>> igb/ixgbe have hardware sctp checksum support, when this feature is
>>>> enabled
>>>> and also IPsec is armed to protect sctp traffic, ugly things
>>>> happened as
>>>> xfrm_output checks CHECKSUM_PARTIAL to do check sum operation(sum
>>>> every thing
>>>> up and pack the 16bits result in the checksum field). The result is
>>>> fail
>>>> establishment of sctp communication.
>>>>
>>> Shouldn't this be fixed in the xfrm code then?  E.g. check the device
>>> features
>>> for SCTP checksum offloading and and skip the checksum during xfrm
>>> output if its
>>> available?
>>>
>>> Or am I missing something?
>>> Neil
>>>
>>>
>>
>>
>>  From 014276de0877f11d46e1704114a7d91f19221a63 Mon Sep 17 00:00:00 2001
>> From: Fan Du <fan.du@...driver.com>
>> Date: Fri, 11 Oct 2013 14:24:33 +0800
>> Subject: [PATCH 1/2] {xfrm, sctp} Stick to software crc32 even if
>> hardware is
>>   capable of that
>>
>> igb/ixgbe have hardware sctp checksum support, when this feature is
>> enabled
>> and also IPsec is armed to protect sctp traffic, ugly things happened as
>> xfrm_output checks CHECKSUM_PARTIAL to do check sum operation(sum every
>> thing
>> up and pack the 16bits result in the checksum field). The result is fail
>> establishment of sctp communication.
>>
>> Signed-off-by: Fan Du <fan.du@...driver.com>
>> ---
>> v2:
>>    Leave ip_summed as CHECKSUM_PARTIAL as before, the second patch will
>> fix this.
>>
>> ---
>>   net/sctp/output.c |   14 +++++++++++++-
>>   1 file changed, 13 insertions(+), 1 deletion(-)
>>
>> diff --git a/net/sctp/output.c b/net/sctp/output.c
>> index 0ac3a65..6de6402 100644
>> --- a/net/sctp/output.c
>> +++ b/net/sctp/output.c
>> @@ -372,6 +372,16 @@ static void sctp_packet_set_owner_w(struct sk_buff
>> *skb, struct sock *sk)
>>       atomic_inc(&sk->sk_wmem_alloc);
>>   }
>>
>> +static int is_xfrm_armed(struct dst_entry *dst)
>> +{
>> +#ifdef CONFIG_XFRM
>> +    /* If dst->xfrm is valid, this skb needs to be transformed */
>> +    return dst->xfrm != NULL;
>> +#else
>> +    return 0;
>> +#endif
>> +}
>> +
>
> I would really prefer to have an accessor function to dst->xfrm, but
> I see that everyone codes it inside the #ifdef.  Gack.
>
>>   /* All packets are sent to the network through this function from
>>    * sctp_outq_tail().
>>    *
>> @@ -536,7 +546,9 @@ int sctp_packet_transmit(struct sctp_packet *packet)
>>        * by CRC32-C as described in <draft-ietf-tsvwg-sctpcsum-02.txt>.
>>        */
>>       if (!sctp_checksum_disable) {
>> -        if (!(dst->dev->features & NETIF_F_SCTP_CSUM)) {
>> +        if ((!(dst->dev->features & NETIF_F_SCTP_CSUM)) ||
>> +            is_xfrm_armed(dst)) {
>> +
>>               __u32 crc32 = sctp_start_cksum((__u8 *)sh, cksum_buf_len);
>>
>>               /* 3) Put the resultant value into the checksum field in
>> the
>
> Acked-by: Vlad Yasevich <vyasevich@...il.com>

This patch doesn't seem to apply to net.git.


-vlad

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