Re: [PATCH net-next v3 2/2] net/smc: support ipv4 mapped ipv6 addr client for smc-r v2

[Guangguan Wang <guangguan.wang@linux.alibaba.com>]

On 2024/12/9 22:10, Wenjia Zhang wrote:
> 
> 
> On 09.12.24 14:06, Guangguan Wang wrote:
>> AF_INET6 is not supported for smc-r v2 client before, even if the
>> ipv6 addr is ipv4 mapped. Thus, when using AF_INET6, smc-r connection
>> will fallback to tcp, especially for java applications running smc-r.
>> This patch support ipv4 mapped ipv6 addr client for smc-r v2. Clients
>> using real global ipv6 addr is still not supported yet.
>>
>> Signed-off-by: Guangguan Wang <guangguan.wang@linux.alibaba.com>
>> Reviewed-by: Wen Gu <guwen@linux.alibaba.com>
>> Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
>> Reviewed-by: D. Wythe <alibuda@linux.alibaba.com>
>> Reviewed-by: Wenjia Zhang <wenjia@linux.ibm.com>
>> ---
>>   net/smc/af_smc.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
>> index 9d76e902fd77..c3f9c0457418 100644
>> --- a/net/smc/af_smc.c
>> +++ b/net/smc/af_smc.c
>> @@ -1116,7 +1116,10 @@ static int smc_find_proposal_devices(struct smc_sock *smc,
>>       ini->check_smcrv2 = true;
>>       ini->smcrv2.saddr = smc->clcsock->sk->sk_rcv_saddr;
>>       if (!(ini->smcr_version & SMC_V2) ||
>> -        smc->clcsock->sk->sk_family != AF_INET ||
>> +#if IS_ENABLED(CONFIG_IPV6)
>> +        (smc->clcsock->sk->sk_family == AF_INET6 &&
>> +         !ipv6_addr_v4mapped(&smc->clcsock->sk->sk_v6_rcv_saddr)) ||
>> +#endif
>>           !smc_clc_ueid_count() ||
>>           smc_find_rdma_device(smc, ini))
>>           ini->smcr_version &= ~SMC_V2;
> 
> @Guangguan, I think Halil's point is valid, and we need to verify if checking on saddr is sufficient before this patch is applied. i.e. what about one peer with ipv4 mapped ipv6 communicates with another peer with a real ipv6 address? Is it possible? If yes, would SMCRv2 be used? I still haven't thought much on this yet, but it is worth to verify. Maybe you already have the answer?

Hi, Wenjia

I have replied the answer to the thread of v2 patch(https://lore.kernel.org/netdev/58075d86-b43a-4d58-bf64-c29418f99143@linux.alibaba.com/)

If there are still any doubts or any other points to clarification, please let me know.

Thanks,
Guangguan Wang

> 
> @Jakub, could you please give us some more time to verify the issue mentioned above?
> 
> Thanks,
> Wenjia