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Message-ID: <aPmGHm9qLwqJEtjF@linux.alibaba.com>
Date: Thu, 23 Oct 2025 09:34:22 +0800
From: Dust Li <dust.li@...ux.alibaba.com>
To: "D. Wythe" <alibuda@...ux.alibaba.com>, mjambigi@...ux.ibm.com,
wenjia@...ux.ibm.com, wintera@...ux.ibm.com,
tonylu@...ux.alibaba.com, guwen@...ux.alibaba.com
Cc: 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 2025-10-22 11:23:09, 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.
Tested it with link local ipv6 address, it still doesn't work as
expected, while TCP works fine.
#smc_run ./sockperf tp --tcp -i fe80::c679:7b0:4a4b:d5cc%eth2
sockperf: == version #3.10-23.gited92afb185e6.dirty ==
sockperf: ERROR: Can`t connect socket (errno=104 Connection reset by peer)
Best regards,
Dust
>
>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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