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Message-ID: <20251027134227.GL12554@unreal>
Date: Mon, 27 Oct 2025 15:42:27 +0200
From: Leon Romanovsky <leon@...nel.org>
To: "D. Wythe" <alibuda@...ux.alibaba.com>
Cc: mjambigi@...ux.ibm.com, wenjia@...ux.ibm.com, wintera@...ux.ibm.com,
dust.li@...ux.alibaba.com, tonylu@...ux.alibaba.com,
guwen@...ux.alibaba.com, kuba@...nel.org, davem@...emloft.net,
netdev@...r.kernel.org, linux-s390@...r.kernel.org,
linux-rdma@...r.kernel.org, pabeni@...hat.com, edumazet@...gle.com,
sidraya@...ux.ibm.com, jaka@...ux.ibm.com
Subject: Re: [PATCH net-next v2] net/smc: add full IPv6 support for SMC
On Wed, Oct 22, 2025 at 11:23:09AM +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.
Why can't you use rdma-cm in-kernel API like any other in-kernel RDMA consumers?
Thanks
>
> Signed-off-by: D. Wythe <alibuda@...ux.alibaba.com>
> ---
> v2: Fix build failure with CONFIG_IPV6 disabled
> ---
> net/smc/af_smc.c | 48 +++++++++++----
> net/smc/smc_core.h | 40 ++++++++++++-
> net/smc/smc_ib.c | 145 ++++++++++++++++++++++++++++++++++++++-------
> net/smc/smc_ib.h | 9 +++
> net/smc/smc_llc.c | 6 +-
> 5 files changed, 209 insertions(+), 39 deletions(-)
>
> diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
> index 77b99e8ef35a..b435c8ba95f5 100644
> --- a/net/smc/af_smc.c
> +++ b/net/smc/af_smc.c
> @@ -1132,12 +1132,15 @@ 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;
> - if (!(ini->smcr_version & SMC_V2) ||
> +
> + if (smc->clcsock->sk->sk_family == AF_INET)
> + smc_ipaddr_from_v4addr(&ini->smcrv2.saddr, smc->clcsock->sk->sk_rcv_saddr);
> #if IS_ENABLED(CONFIG_IPV6)
> - (smc->clcsock->sk->sk_family == AF_INET6 &&
> - !ipv6_addr_v4mapped(&smc->clcsock->sk->sk_v6_rcv_saddr)) ||
> -#endif
> + else
> + smc_ipaddr_from_v6addr(&ini->smcrv2.saddr, &smc->clcsock->sk->sk_v6_rcv_saddr);
> +#endif /* CONFIG_IPV6 */
> +
> + if (!(ini->smcr_version & SMC_V2) ||
> !smc_clc_ueid_count() ||
> smc_find_rdma_device(smc, ini))
> ini->smcr_version &= ~SMC_V2;
> @@ -1230,11 +1233,27 @@ static int smc_connect_rdma_v2_prepare(struct smc_sock *smc,
> memcpy(ini->smcrv2.nexthop_mac, &aclc->r0.lcl.mac, ETH_ALEN);
> ini->smcrv2.uses_gateway = false;
> } else {
> - if (smc_ib_find_route(net, smc->clcsock->sk->sk_rcv_saddr,
> - smc_ib_gid_to_ipv4(aclc->r0.lcl.gid),
> - ini->smcrv2.nexthop_mac,
> - &ini->smcrv2.uses_gateway))
> + struct smc_ipaddr peer_gid;
> +
> + smc_ipaddr_from_gid(&peer_gid, aclc->r0.lcl.gid);
> + if (peer_gid.family == AF_INET) {
> + /* v4-mapped v6 address should also be treated as v4 address. */
> + if (smc_ib_find_route(net, smc->clcsock->sk->sk_rcv_saddr,
> + peer_gid.addr,
> + ini->smcrv2.nexthop_mac,
> + &ini->smcrv2.uses_gateway))
> + return SMC_CLC_DECL_NOROUTE;
> + } else {
> +#if IS_ENABLED(CONFIG_IPV6)
> + if (smc_ib_find_route_v6(net, &smc->clcsock->sk->sk_v6_rcv_saddr,
> + &peer_gid.addr_v6,
> + ini->smcrv2.nexthop_mac,
> + &ini->smcrv2.uses_gateway))
> + return SMC_CLC_DECL_NOROUTE;
> +#else
> return SMC_CLC_DECL_NOROUTE;
> +#endif /* CONFIG_IPV6 */
> + }
> if (!ini->smcrv2.uses_gateway) {
> /* mismatch: peer claims indirect, but its direct */
> return SMC_CLC_DECL_NOINDIRECT;
> @@ -2307,8 +2326,15 @@ 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);
> +
> + if (new_smc->clcsock->sk->sk_family == AF_INET)
> + smc_ipaddr_from_v4addr(&ini->smcrv2.saddr, new_smc->clcsock->sk->sk_rcv_saddr);
> +#if IS_ENABLED(CONFIG_IPV6)
> + else
> + smc_ipaddr_from_v6addr(&ini->smcrv2.saddr, &new_smc->clcsock->sk->sk_v6_rcv_saddr);
> +#endif /* CONFIG_IPV6 */
> + 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
> index a5a78cbff341..6b07785f9874 100644
> --- a/net/smc/smc_core.h
> +++ b/net/smc/smc_core.h
> @@ -279,6 +279,14 @@ struct smc_llc_flow {
> struct smc_llc_qentry *qentry;
> };
>
> +struct smc_ipaddr {
> + sa_family_t family;
> + union {
> + __be32 addr;
> + struct in6_addr addr_v6;
> + };
> +};
> +
> struct smc_link_group {
> struct list_head list;
> struct rb_root conns_all; /* connection tree */
> @@ -359,7 +367,7 @@ struct smc_link_group {
> /* rsn code for termination */
> u8 nexthop_mac[ETH_ALEN];
> u8 uses_gateway;
> - __be32 saddr;
> + struct smc_ipaddr saddr;
> /* net namespace */
> struct net *net;
> u8 max_conns;
> @@ -389,9 +397,9 @@ struct smc_gidlist {
>
> struct smc_init_info_smcrv2 {
> /* Input fields */
> - __be32 saddr;
> + struct smc_ipaddr saddr;
> struct sock *clc_sk;
> - __be32 daddr;
> + struct smc_ipaddr daddr;
>
> /* Output fields when saddr is set */
> struct smc_ib_device *ib_dev_v2;
> @@ -618,4 +626,30 @@ static inline struct smc_link_group *smc_get_lgr(struct smc_link *link)
> {
> return link->lgr;
> }
> +
> +static inline void smc_ipaddr_from_v4addr(struct smc_ipaddr *ipaddr, __be32 v4_addr)
> +{
> + ipaddr->family = AF_INET;
> + ipaddr->addr = v4_addr;
> +}
> +
> +static inline void smc_ipaddr_from_v6addr(struct smc_ipaddr *ipaddr, const struct in6_addr *v6_addr)
> +{
> + ipaddr->family = AF_INET6;
> + ipaddr->addr_v6 = *v6_addr;
> +}
> +
> +static inline void smc_ipaddr_from_gid(struct smc_ipaddr *ipaddr, u8 gid[SMC_GID_SIZE])
> +{
> + __be32 gid_v4 = smc_ib_gid_to_ipv4(gid);
> +
> + if (gid_v4 != cpu_to_be32(INADDR_NONE)) {
> + ipaddr->family = AF_INET;
> + ipaddr->addr = gid_v4;
> + } else {
> + ipaddr->family = AF_INET6;
> + ipaddr->addr_v6 = *smc_ib_gid_to_ipv6(gid);
> + }
> +}
> +
> #endif
> diff --git a/net/smc/smc_ib.c b/net/smc/smc_ib.c
> index 0052f02756eb..9c4c53be7bfc 100644
> --- a/net/smc/smc_ib.c
> +++ b/net/smc/smc_ib.c
> @@ -22,6 +22,7 @@
> #include <linux/inetdevice.h>
> #include <rdma/ib_verbs.h>
> #include <rdma/ib_cache.h>
> +#include <net/ip6_route.h>
>
> #include "smc_pnet.h"
> #include "smc_ib.h"
> @@ -225,48 +226,148 @@ int smc_ib_find_route(struct net *net, __be32 saddr, __be32 daddr,
> return -ENOENT;
> }
>
> -static int smc_ib_determine_gid_rcu(const struct net_device *ndev,
> +#if IS_ENABLED(CONFIG_IPV6)
> +int smc_ib_find_route_v6(struct net *net, struct in6_addr *saddr,
> + struct in6_addr *daddr, u8 nexthop_mac[],
> + u8 *uses_gateway)
> +{
> + struct dst_entry *dst;
> + struct rt6_info *rt;
> + struct neighbour *neigh;
> + struct in6_addr *nexthop_addr;
> + int rc = -ENOENT;
> +
> + struct flowi6 fl6 = {
> + .daddr = *daddr,
> + .saddr = *saddr,
> + };
> +
> + if (ipv6_addr_any(daddr))
> + return -EINVAL;
> +
> + dst = ip6_route_output(net, NULL, &fl6);
> + if (!dst || dst->error) {
> + rc = dst ? dst->error : -EINVAL;
> + goto out;
> + }
> + rt = (struct rt6_info *)dst;
> +
> + if (ipv6_addr_type(&rt->rt6i_gateway) != IPV6_ADDR_ANY) {
> + *uses_gateway = 1;
> + nexthop_addr = &rt->rt6i_gateway;
> + } else {
> + *uses_gateway = 0;
> + nexthop_addr = daddr;
> + }
> +
> + neigh = dst_neigh_lookup(dst, nexthop_addr);
> + if (!neigh)
> + goto out;
> +
> + read_lock_bh(&neigh->lock);
> + if (neigh->nud_state & NUD_VALID) {
> + memcpy(nexthop_mac, neigh->ha, ETH_ALEN);
> + rc = 0;
> + }
> + read_unlock_bh(&neigh->lock);
> +
> + neigh_release(neigh);
> +out:
> + dst_release(dst);
> + return rc;
> +}
> +#endif /* CONFIG_IPV6 */
> +
> +static bool smc_ib_match_gid_rocev2(const struct net_device *ndev,
> const struct ib_gid_attr *attr,
> - u8 gid[], u8 *sgid_index,
> struct smc_init_info_smcrv2 *smcrv2)
> {
> - if (!smcrv2 && attr->gid_type == IB_GID_TYPE_ROCE) {
> - if (gid)
> - memcpy(gid, &attr->gid, SMC_GID_SIZE);
> - if (sgid_index)
> - *sgid_index = attr->index;
> - return 0;
> - }
> - if (smcrv2 && attr->gid_type == IB_GID_TYPE_ROCE_UDP_ENCAP &&
> - smc_ib_gid_to_ipv4((u8 *)&attr->gid) != cpu_to_be32(INADDR_NONE)) {
> + struct net *net = dev_net(ndev);
> + bool subnet_match = false;
> +
> + if (smc_ib_gid_to_ipv4((u8 *)&attr->gid) != cpu_to_be32(INADDR_NONE)) {
> struct in_device *in_dev = __in_dev_get_rcu(ndev);
> - struct net *net = dev_net(ndev);
> const struct in_ifaddr *ifa;
> - bool subnet_match = false;
>
> if (!in_dev)
> - goto out;
> + return false;
> +
> + if (smcrv2->saddr.family != AF_INET)
> + return false;
> +
> in_dev_for_each_ifa_rcu(ifa, in_dev) {
> - if (!inet_ifa_match(smcrv2->saddr, ifa))
> + if (!inet_ifa_match(smcrv2->saddr.addr, ifa))
> continue;
> subnet_match = true;
> break;
> }
> +
> if (!subnet_match)
> - goto out;
> - if (smcrv2->daddr && smc_ib_find_route(net, smcrv2->saddr,
> - smcrv2->daddr,
> - smcrv2->nexthop_mac,
> - &smcrv2->uses_gateway))
> - goto out;
> + return false;
> +
> + if (smcrv2->daddr.addr &&
> + smc_ib_find_route(net, smcrv2->saddr.addr,
> + smcrv2->daddr.addr,
> + smcrv2->nexthop_mac,
> + &smcrv2->uses_gateway))
> + return false;
> +#if IS_ENABLED(CONFIG_IPV6)
> + } else if (!(ipv6_addr_type(smc_ib_gid_to_ipv6((u8 *)&attr->gid)) & IPV6_ADDR_LINKLOCAL)) {
> + struct inet6_dev *in6_dev = __in6_dev_get(ndev);
> + const struct inet6_ifaddr *if6;
> +
> + if (!in6_dev)
> + return false;
> +
> + if (smcrv2->saddr.family != AF_INET6)
> + return false;
> +
> + list_for_each_entry_rcu(if6, &in6_dev->addr_list, if_list) {
> + if (ipv6_addr_type(&if6->addr) & IPV6_ADDR_LINKLOCAL)
> + continue;
> + if (!ipv6_prefix_equal(&if6->addr, &smcrv2->saddr.addr_v6, if6->prefix_len))
> + continue;
> + subnet_match = true;
> + break;
> + }
>
> + if (!subnet_match)
> + return false;
> +
> + if ((ipv6_addr_type(&smcrv2->daddr.addr_v6) != IPV6_ADDR_ANY) &&
> + smc_ib_find_route_v6(net, &smcrv2->saddr.addr_v6,
> + &smcrv2->daddr.addr_v6,
> + smcrv2->nexthop_mac,
> + &smcrv2->uses_gateway))
> + return false;
> +#endif /* CONFIG_IPV6 */
> + } else {
> + return false;
> + }
> +
> + return true;
> +}
> +
> +static int smc_ib_determine_gid_rcu(const struct net_device *ndev,
> + const struct ib_gid_attr *attr,
> + u8 gid[], u8 *sgid_index,
> + struct smc_init_info_smcrv2 *smcrv2)
> +{
> + bool gid_match = false;
> +
> + if (!smcrv2 && attr->gid_type == IB_GID_TYPE_ROCE)
> + gid_match = true;
> + else if (smcrv2 && attr->gid_type == IB_GID_TYPE_ROCE_UDP_ENCAP)
> + gid_match = smc_ib_match_gid_rocev2(ndev, attr, smcrv2);
> +
> + if (gid_match) {
> if (gid)
> memcpy(gid, &attr->gid, SMC_GID_SIZE);
> if (sgid_index)
> *sgid_index = attr->index;
> return 0;
> }
> -out:
> +
> return -ENODEV;
> }
>
> diff --git a/net/smc/smc_ib.h b/net/smc/smc_ib.h
> index ef8ac2b7546d..7cbeb7350478 100644
> --- a/net/smc/smc_ib.h
> +++ b/net/smc/smc_ib.h
> @@ -69,6 +69,12 @@ static inline __be32 smc_ib_gid_to_ipv4(u8 gid[SMC_GID_SIZE])
> return cpu_to_be32(INADDR_NONE);
> }
>
> +static inline struct in6_addr *smc_ib_gid_to_ipv6(u8 gid[SMC_GID_SIZE])
> +{
> + struct in6_addr *addr6 = (struct in6_addr *)gid;
> + return addr6;
> +}
> +
> static inline struct net *smc_ib_net(struct smc_ib_device *smcibdev)
> {
> if (smcibdev && smcibdev->ibdev)
> @@ -114,6 +120,9 @@ int smc_ib_determine_gid(struct smc_ib_device *smcibdev, u8 ibport,
> struct smc_init_info_smcrv2 *smcrv2);
> int smc_ib_find_route(struct net *net, __be32 saddr, __be32 daddr,
> u8 nexthop_mac[], u8 *uses_gateway);
> +int smc_ib_find_route_v6(struct net *net, struct in6_addr *saddr,
> + struct in6_addr *daddr, u8 nexthop_mac[],
> + u8 *uses_gateway);
> bool smc_ib_is_valid_local_systemid(void);
> int smcr_nl_get_device(struct sk_buff *skb, struct netlink_callback *cb);
> #endif
> diff --git a/net/smc/smc_llc.c b/net/smc/smc_llc.c
> index f865c58c3aa7..f2a02611ab25 100644
> --- a/net/smc/smc_llc.c
> +++ b/net/smc/smc_llc.c
> @@ -1055,8 +1055,9 @@ int smc_llc_cli_add_link(struct smc_link *link, struct smc_llc_qentry *qentry)
> if (lgr->smc_version == SMC_V2) {
> ini->check_smcrv2 = true;
> ini->smcrv2.saddr = lgr->saddr;
> - ini->smcrv2.daddr = smc_ib_gid_to_ipv4(llc->sender_gid);
> + smc_ipaddr_from_gid(&ini->smcrv2.daddr, llc->sender_gid);
> }
> +
> smc_pnet_find_alt_roce(lgr, ini, link->smcibdev);
> if (!memcmp(llc->sender_gid, link->peer_gid, SMC_GID_SIZE) &&
> (lgr->smc_version == SMC_V2 ||
> @@ -1438,8 +1439,7 @@ int smc_llc_srv_add_link(struct smc_link *link,
> if (send_req_add_link_resp) {
> struct smc_llc_msg_req_add_link_v2 *req_add =
> &req_qentry->msg.req_add_link;
> -
> - ini->smcrv2.daddr = smc_ib_gid_to_ipv4(req_add->gid[0]);
> + smc_ipaddr_from_gid(&ini->smcrv2.daddr, req_add->gid[0]);
> }
> }
> smc_pnet_find_alt_roce(lgr, ini, link->smcibdev);
> --
> 2.45.0
>
>
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