net/smc: Add global configure for handshake limitation by netlink

Although we can control SMC handshake limitation through socket options,
which means that applications who need it must modify their code. It's
quite troublesome for many existing applications. This patch modifies
the global default value of SMC handshake limitation through netlink,
providing a way to put constraint on handshake without modifies any code
for applications.

Suggested-by: Tony Lu <tonylu@linux.alibaba.com>
Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
Reviewed-by: Tony Lu <tonylu@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

6 files changed, 79 insertions, 0 deletions

diff --git a/include/net/netns/smc.h b/include/net/netns/smc.h
index ea8a9cf2619b..47b166684fd8 100644
--- a/include/net/netns/smc.h
+++ b/include/net/netns/smc.h
@@ -12,5 +12,7 @@ struct netns_smc {
 	/* protect fback_rsn */
 	struct mutex			mutex_fback_rsn;
 	struct smc_stats_rsn		*fback_rsn;
+
+	bool				limit_smc_hs;	/* constraint on handshake */
 };
 #endif
diff --git a/include/uapi/linux/smc.h b/include/uapi/linux/smc.h
index 343e7450c3a3..693f549f6966 100644
--- a/include/uapi/linux/smc.h
+++ b/include/uapi/linux/smc.h
@@ -59,6 +59,9 @@ enum {
 	SMC_NETLINK_DUMP_SEID,
 	SMC_NETLINK_ENABLE_SEID,
 	SMC_NETLINK_DISABLE_SEID,
+	SMC_NETLINK_DUMP_HS_LIMITATION,
+	SMC_NETLINK_ENABLE_HS_LIMITATION,
+	SMC_NETLINK_DISABLE_HS_LIMITATION,
 };
 
 /* SMC_GENL_FAMILY top level attributes */
@@ -285,6 +288,14 @@ enum {
 	SMC_NLA_SEID_TABLE_MAX = __SMC_NLA_SEID_TABLE_MAX - 1
 };
 
+/* SMC_NETLINK_HS_LIMITATION attributes */
+enum {
+	SMC_NLA_HS_LIMITATION_UNSPEC,
+	SMC_NLA_HS_LIMITATION_ENABLED,	/* u8 */
+	__SMC_NLA_HS_LIMITATION_MAX,
+	SMC_NLA_HS_LIMITATION_MAX = __SMC_NLA_HS_LIMITATION_MAX - 1
+};
+
 /* SMC socket options */
 #define SMC_LIMIT_HS 1	/* constraint on smc handshake */
 
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 97dcdc0a2107..246c874de629 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -66,6 +66,45 @@ struct workqueue_struct	*smc_close_wq;	/* wq for close work */
 static void smc_tcp_listen_work(struct work_struct *);
 static void smc_connect_work(struct work_struct *);
 
+int smc_nl_dump_hs_limitation(struct sk_buff *skb, struct netlink_callback *cb)
+{
+	struct smc_nl_dmp_ctx *cb_ctx = smc_nl_dmp_ctx(cb);
+	void *hdr;
+
+	if (cb_ctx->pos[0])
+		goto out;
+
+	hdr = genlmsg_put(skb, NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq,
+			  &smc_gen_nl_family, NLM_F_MULTI,
+			  SMC_NETLINK_DUMP_HS_LIMITATION);
+	if (!hdr)
+		return -ENOMEM;
+
+	if (nla_put_u8(skb, SMC_NLA_HS_LIMITATION_ENABLED,
+		       sock_net(skb->sk)->smc.limit_smc_hs))
+		goto err;
+
+	genlmsg_end(skb, hdr);
+	cb_ctx->pos[0] = 1;
+out:
+	return skb->len;
+err:
+	genlmsg_cancel(skb, hdr);
+	return -EMSGSIZE;
+}
+
+int smc_nl_enable_hs_limitation(struct sk_buff *skb, struct genl_info *info)
+{
+	sock_net(skb->sk)->smc.limit_smc_hs = true;
+	return 0;
+}
+
+int smc_nl_disable_hs_limitation(struct sk_buff *skb, struct genl_info *info)
+{
+	sock_net(skb->sk)->smc.limit_smc_hs = false;
+	return 0;
+}
+
 static void smc_set_keepalive(struct sock *sk, int val)
 {
 	struct smc_sock *smc = smc_sk(sk);
@@ -3007,6 +3046,9 @@ static int __smc_create(struct net *net, struct socket *sock, int protocol,
 	smc->use_fallback = false; /* assume rdma capability first */
 	smc->fallback_rsn = 0;
 
+	/* default behavior from limit_smc_hs in every net namespace */
+	smc->limit_smc_hs = net->smc.limit_smc_hs;
+
 	rc = 0;
 	if (!clcsock) {
 		rc = sock_create_kern(net, family, SOCK_STREAM, IPPROTO_TCP,
diff --git a/net/smc/smc.h b/net/smc/smc.h
index 7e2693832a1b..a096d8af21a0 100644
--- a/net/smc/smc.h
+++ b/net/smc/smc.h
@@ -14,6 +14,7 @@
 #include <linux/socket.h>
 #include <linux/types.h>
 #include <linux/compiler.h> /* __aligned */
+#include <net/genetlink.h>
 #include <net/sock.h>
 
 #include "smc_ib.h"
@@ -336,4 +337,9 @@ void smc_fill_gid_list(struct smc_link_group *lgr,
 		       struct smc_gidlist *gidlist,
 		       struct smc_ib_device *known_dev, u8 *known_gid);
 
+/* smc handshake limitation interface for netlink  */
+int smc_nl_dump_hs_limitation(struct sk_buff *skb, struct netlink_callback *cb);
+int smc_nl_enable_hs_limitation(struct sk_buff *skb, struct genl_info *info);
+int smc_nl_disable_hs_limitation(struct sk_buff *skb, struct genl_info *info);
+
 #endif	/* __SMC_H */
diff --git a/net/smc/smc_netlink.c b/net/smc/smc_netlink.c
index f13ab0661ed5..c5a62f6f52ba 100644
--- a/net/smc/smc_netlink.c
+++ b/net/smc/smc_netlink.c
@@ -111,6 +111,21 @@ static const struct genl_ops smc_gen_nl_ops[] = {
 		.flags = GENL_ADMIN_PERM,
 		.doit = smc_nl_disable_seid,
 	},
+	{
+		.cmd = SMC_NETLINK_DUMP_HS_LIMITATION,
+		/* can be retrieved by unprivileged users */
+		.dumpit = smc_nl_dump_hs_limitation,
+	},
+	{
+		.cmd = SMC_NETLINK_ENABLE_HS_LIMITATION,
+		.flags = GENL_ADMIN_PERM,
+		.doit = smc_nl_enable_hs_limitation,
+	},
+	{
+		.cmd = SMC_NETLINK_DISABLE_HS_LIMITATION,
+		.flags = GENL_ADMIN_PERM,
+		.doit = smc_nl_disable_hs_limitation,
+	},
 };
 
 static const struct nla_policy smc_gen_nl_policy[2] = {
diff --git a/net/smc/smc_pnet.c b/net/smc/smc_pnet.c
index 0599246c0376..ff61b7b95875 100644
--- a/net/smc/smc_pnet.c
+++ b/net/smc/smc_pnet.c
@@ -870,6 +870,9 @@ int smc_pnet_net_init(struct net *net)
 
 	smc_pnet_create_pnetids_list(net);
 
+	/* disable handshake limitation by default */
+	net->smc.limit_smc_hs = 0;
+
 	return 0;
 }