Subject: Re: [PATCH net-next] net/smc: add full IPv6 support for SMC

From: Simon Horman <[email-masked]>
Date: Thu, 16 Oct 2025 14:35:39 +0100

On Thu, Oct 16, 2025 at 01:45:41PM +0800, D. Wythe wrote:
> The current SMC implementation is IPv4-centric. While it contains a
> workaround for IPv4-mapped IPv6 addresses, it lacks a functional path
> for native IPv6, preventing its use in modern dual-stack or IPv6-only
> networks.
> 
> This patch introduces full, native IPv6 support by refactoring the
> address handling mechanism to be IP-version agnostic, which is
> achieved by:
> 
> - Introducing a generic `struct smc_ipaddr` to abstract IP addresses.
> - Implementing an IPv6-specific route lookup function.
> - Extend GID matching logic for both IPv4 and IPv6 addresses
> 
> With these changes, SMC can now discover RDMA devices and establish
> connections over both native IPv4 and IPv6 networks.
> 
> Signed-off-by: D. Wythe <[email-masked]>
> ---
>  net/smc/af_smc.c   |  35 +++++++----
>  net/smc/smc_core.h |  40 ++++++++++++-
>  net/smc/smc_ib.c   | 143 ++++++++++++++++++++++++++++++++++++++-------
>  net/smc/smc_ib.h   |   9 +++
>  net/smc/smc_llc.c  |   6 +-
>  5 files changed, 193 insertions(+), 40 deletions(-)
> 
> diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
> index 77b99e8ef35a..cbff0b29ad5b 100644
> --- a/net/smc/af_smc.c
> +++ b/net/smc/af_smc.c
> @@ -1132,12 +1132,9 @@ static int smc_find_proposal_devices(struct smc_sock *smc,
>  
>  	/* check if there is an rdma v2 device available */
>  	ini->check_smcrv2 = true;
> -	ini->smcrv2.saddr = smc->clcsock->sk->sk_rcv_saddr;
> +
> +	smc_ipaddr_from(&ini->smcrv2.saddr, smc->clcsock->sk, sk_rcv_saddr, sk_v6_rcv_saddr);

Hi,

Unfortunately this introduces a compilation error when CONFIG_IPV6=n.

In file included from smc_wr.h:20,
                 from smc_llc.h:16,
                 from af_smc.c:47:
af_smc.c: In function ‘smc_find_proposal_devices’:
/home/horms/projects/linux/linux/include/net/sock.h:388:37: error: ‘struct sock_common’ has no member named ‘skc_v6_rcv_saddr’; did you mean ‘skc_rcv_saddr’?
  388 | #define sk_v6_rcv_saddr __sk_common.skc_v6_rcv_saddr
      |                                     ^~~~~~~~~~~~~~~~
smc_core.h:639:51: note: in definition of macro ‘smc_ipaddr_from’
  639 |                         __ipaddr->addr_v6 = __sk->_v6_member;   \
      |                                                   ^~~~~~~~~~
af_smc.c:1136:77: note: in expansion of macro ‘sk_v6_rcv_saddr’
 1136 |         smc_ipaddr_from(&ini->smcrv2.saddr, smc->clcsock->sk, sk_rcv_saddr, sk_v6_rcv_saddr);
      |                                                                             ^~~~~~~~~~~~~~~

>  	if (!(ini->smcr_version & SMC_V2) ||
> -#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;

...

> @@ -2307,8 +2316,10 @@ static void smc_find_rdma_v2_device_serv(struct smc_sock *new_smc,
>  	memcpy(ini->peer_mac, pclc->lcl.mac, ETH_ALEN);
>  	ini->check_smcrv2 = true;
>  	ini->smcrv2.clc_sk = new_smc->clcsock->sk;
> -	ini->smcrv2.saddr = new_smc->clcsock->sk->sk_rcv_saddr;
> -	ini->smcrv2.daddr = smc_ib_gid_to_ipv4(smc_v2_ext->roce);
> +
> +	smc_ipaddr_from(&ini->smcrv2.saddr, new_smc->clcsock->sk, sk_rcv_saddr, sk_v6_rcv_saddr);
> +	smc_ipaddr_from_gid(&ini->smcrv2.daddr, smc_v2_ext->roce);
> +
>  	rc = smc_find_rdma_device(new_smc, ini);
>  	if (rc) {
>  		smc_find_ism_store_rc(rc, ini);

> diff --git a/net/smc/smc_core.h b/net/smc/smc_core.h

...

> @@ -618,4 +626,30 @@ static inline struct smc_link_group *smc_get_lgr(struct smc_link *link)
>  {
>  	return link->lgr;
>  }
> +
> +#define smc_ipaddr_from(_ipaddr, _sk, _v4_member, _v6_member)	\
> +	do {							\
> +		struct smc_ipaddr *__ipaddr = (_ipaddr);	\
> +		struct sock *__sk = (_sk);			\
> +		int __family = __sk->sk_family;			\
> +		__ipaddr->family = __family;			\
> +		if (__family == AF_INET)			\
> +			__ipaddr->addr = __sk->_v4_member;	\
> +		else						\
> +			__ipaddr->addr_v6 = __sk->_v6_member;	\
> +	} while (0)
> +

...

-- 
pw-bot: changes-requested