Re: [PATCH net v2] net: ipv6: fix TCP GSO segmentation with NAT

[Felix Fietkau <nbd@nbd.name>]

On 10.03.25 14:50, Eric Dumazet wrote:
> On Mon, Mar 10, 2025 at 12:21 PM Felix Fietkau <nbd@nbd.name> wrote:
>>
>> When updating the source/destination address, the TCP/UDP checksum needs to
>> be updated as well.
>>
>> Fixes: bee88cd5bd83 ("net: add support for segmenting TCP fraglist GSO packets")
>> Signed-off-by: Felix Fietkau <nbd@nbd.name>
>> ---
>> v2: move code to make it similar to __tcpv4_gso_segment_list_csum
>>
>>  net/ipv6/tcpv6_offload.c | 18 ++++++++++++++----
>>  1 file changed, 14 insertions(+), 4 deletions(-)
>>
>> diff --git a/net/ipv6/tcpv6_offload.c b/net/ipv6/tcpv6_offload.c
>> index a45bf17cb2a1..34dd0cee3ba6 100644
>> --- a/net/ipv6/tcpv6_offload.c
>> +++ b/net/ipv6/tcpv6_offload.c
>> @@ -94,10 +94,20 @@ INDIRECT_CALLABLE_SCOPE int tcp6_gro_complete(struct sk_buff *skb, int thoff)
>>  }
>>
>>  static void __tcpv6_gso_segment_csum(struct sk_buff *seg,
>> +                                    struct in6_addr *oldip,
>> +                                    const struct in6_addr *newip,
>>                                      __be16 *oldport, __be16 newport)
>>  {
>>         struct tcphdr *th;
>>
>> +       if (!ipv6_addr_equal(oldip, newip)) {
>> +               inet_proto_csum_replace16(&th->check, seg,
> 
> th is not initialized yet.

Sorry, I had this fixed locally, but forgot to add it before sending. 
Will send v3 later.

- Felix