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Thanks for the quick response. I'll fix up these issues and repost.
On Tue, Jul 23, 2013 at 4:14 PM, Julian Anastasov <ja@xxxxxx> wrote:
>
> Hello,
>
> On Tue, 23 Jul 2013, Joe Stringer wrote:
>
>> This patch consolidates the SCTP checksum calculation code from various
>> places to a single new function, sctp_compute_cksum(skb, offset).
>>
>> Signed-off-by: Joe Stringer <joe@xxxxxxxxxxx>
>> ---
>> include/net/sctp/checksum.h | 15 +++++++++++++++
>> net/netfilter/ipvs/ip_vs_proto_sctp.c | 23 ++++-------------------
>> net/netfilter/nf_nat_proto_sctp.c | 8 +-------
>> net/sctp/input.c | 10 +---------
>> 4 files changed, 21 insertions(+), 35 deletions(-)
>>
>> diff --git a/include/net/sctp/checksum.h b/include/net/sctp/checksum.h
>> index 0cb08e6..8675564 100644
>> --- a/include/net/sctp/checksum.h
>> +++ b/include/net/sctp/checksum.h
>> @@ -85,4 +85,19 @@ static inline __le32 sctp_end_cksum(__u32 crc32)
>> return cpu_to_le32(~crc32);
>> }
>>
>> +/* Calculate the CRC32C checksum of an SCTP packet. */
>> +static inline __le32 sctp_compute_cksum(const struct sk_buff *skb,
>> + unsigned int offset)
>> +{
>> + const struct sk_buff *iter;
>> +
>> + __u32 crc32 = sctp_start_cksum((__u8 *)sctp_hdr(skb),
>> + skb_headlen(skb) - offset);
>
> sctp_hdr() is valid in INPUT hook after commit
> 21d1196a35f5686c4323e42a62fdb4b23b0ab4a3 (ipv4: set transport header
> earlier) but I'm not sure for the OUTPUT hook where
> IPVS is working. I guess the same is valid for Netfilter.
>
> IPVS uses skb_network_header(skb) + offset but
> I guess it can work with skb->data, just like Netfilter:
>
> __u32 crc32 = sctp_start_cksum(skb->data + offset,
>
> This should work also in SCTP where skb->data points
> to the SCTP header when sctp_rcv_checksum() is called.
>
>> + skb_walk_frags(skb, iter)
>> + crc32 = sctp_update_cksum((__u8 *) iter->data,
>> + skb_headlen(iter), crc32);
>> +
>> + return sctp_end_cksum(crc32);
>> +}
>> +
>> #endif /* __sctp_checksum_h__ */
>> diff --git a/net/netfilter/ipvs/ip_vs_proto_sctp.c
>> b/net/netfilter/ipvs/ip_vs_proto_sctp.c
>> index 3c0da87..b2e422d 100644
>> --- a/net/netfilter/ipvs/ip_vs_proto_sctp.c
>> +++ b/net/netfilter/ipvs/ip_vs_proto_sctp.c
>> @@ -66,15 +66,9 @@ sctp_conn_schedule(int af, struct sk_buff *skb, struct
>> ip_vs_proto_data *pd,
>> static void sctp_nat_csum(struct sk_buff *skb, sctp_sctphdr_t *sctph,
>> unsigned int sctphoff)
>> {
>> - __u32 crc32;
>> - struct sk_buff *iter;
>> -
>> - crc32 = sctp_start_cksum((__u8 *)sctph, skb_headlen(skb) - sctphoff);
>> - skb_walk_frags(skb, iter)
>> - crc32 = sctp_update_cksum((u8 *) iter->data,
>> - skb_headlen(iter), crc32);
>> - sctph->checksum = sctp_end_cksum(crc32);
>> + __le32 crc32 = sctp_compute_cksum(skb, sctphoff);
>
> crc32 var is not needed anymore, eg:
>
> sctph->checksum = sctp_compute_cksum(skb, sctphoff);
>
>> + sctph->checksum = crc32;
>> skb->ip_summed = CHECKSUM_UNNECESSARY;
>> }
>>
>> @@ -151,10 +145,7 @@ sctp_csum_check(int af, struct sk_buff *skb, struct
>> ip_vs_protocol *pp)
>> {
>> unsigned int sctphoff;
>> struct sctphdr *sh, _sctph;
>> - struct sk_buff *iter;
>> - __le32 cmp;
>> - __le32 val;
>> - __u32 tmp;
>> + __le32 cmp, val;
>>
>> #ifdef CONFIG_IP_VS_IPV6
>> if (af == AF_INET6)
>> @@ -168,13 +159,7 @@ sctp_csum_check(int af, struct sk_buff *skb, struct
>> ip_vs_protocol *pp)
>> return 0;
>>
>> cmp = sh->checksum;
>> -
>> - tmp = sctp_start_cksum((__u8 *) sh, skb_headlen(skb));
>> - skb_walk_frags(skb, iter)
>> - tmp = sctp_update_cksum((__u8 *) iter->data,
>> - skb_headlen(iter), tmp);
>> -
>> - val = sctp_end_cksum(tmp);
>> + val = sctp_compute_cksum(skb, 0);
>
> The original code has bug here, still the code
> was never used because there are no IPVS apps with
> SCTP support. You can safely use sctphoff here, not 0, eg:
>
> val = sctp_compute_cksum(skb, sctphoff);
>
>> if (val != cmp) {
>> /* CRC failure, dump it. */
>
> Regards
>
> --
> Julian Anastasov <ja@xxxxxx>
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