Message-id: <20171218215109.38700-7-cpaasch@apple.com>
Date:   Mon, 18 Dec 2017 13:51:01 -0800
From:   Christoph Paasch <cpaasch@...le.com>
To:     netdev@...r.kernel.org
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Ursula Braun <ubraun@...ux.vnet.ibm.com>
Subject: [RFC 06/14] tcp_smc: Make SMC use TCP extra-option framework

Adopt the extra-option framework for SMC.
It allows us to entirely remove SMC-code out of the TCP-stack.

The static key is gone, as this is now covered by the static key of the
extra-option framework.

We allocate state (struct tcp_smc_opt) that indicates whether SMC was
successfully negotiated or not and check this state in the relevant
functions.

Cc: Ursula Braun <ubraun@...ux.vnet.ibm.com>
Signed-off-by: Christoph Paasch <cpaasch@...le.com>
Reviewed-by: Mat Martineau <mathew.j.martineau@...ux.intel.com>
---
 include/linux/tcp.h      |   3 +-
 include/net/inet_sock.h  |   3 +-
 include/net/tcp.h        |   4 -
 net/ipv4/tcp.c           |   5 --
 net/ipv4/tcp_input.c     |  36 ---------
 net/ipv4/tcp_minisocks.c |  18 -----
 net/ipv4/tcp_output.c    |  54 --------------
 net/smc/af_smc.c         | 190 +++++++++++++++++++++++++++++++++++++++++++++--
 8 files changed, 186 insertions(+), 127 deletions(-)

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 4756bd2c4b54..231b352f587f 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -257,8 +257,7 @@ struct tcp_sock {
 		syn_fastopen_ch:1, /* Active TFO re-enabling probe */
 		syn_data_acked:1,/* data in SYN is acked by SYN-ACK */
 		save_syn:1,	/* Save headers of SYN packet */
-		is_cwnd_limited:1,/* forward progress limited by snd_cwnd? */
-		syn_smc:1;	/* SYN includes SMC */
+		is_cwnd_limited:1;/* forward progress limited by snd_cwnd? */
 	u32	tlp_high_seq;	/* snd_nxt at the time of TLP retransmit. */
 
 /* RTT measurement */
diff --git a/include/net/inet_sock.h b/include/net/inet_sock.h
index 39efb968b7a4..8e51b4a69088 100644
--- a/include/net/inet_sock.h
+++ b/include/net/inet_sock.h
@@ -90,8 +90,7 @@ struct inet_request_sock {
 				wscale_ok  : 1,
 				ecn_ok	   : 1,
 				acked	   : 1,
-				no_srccheck: 1,
-				smc_ok	   : 1;
+				no_srccheck: 1;
 	u32                     ir_mark;
 	union {
 		struct ip_options_rcu __rcu	*ireq_opt;
diff --git a/include/net/tcp.h b/include/net/tcp.h
index ac62ceff9815..a5c4856e25c7 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -2062,10 +2062,6 @@ static inline bool tcp_bpf_ca_needs_ecn(struct sock *sk)
 	return (tcp_call_bpf(sk, BPF_SOCK_OPS_NEEDS_ECN) == 1);
 }
 
-#if IS_ENABLED(CONFIG_SMC)
-extern struct static_key_false tcp_have_smc;
-#endif
-
 struct tcp_extopt_store;
 
 struct tcp_extopt_ops {
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 17f38afb4212..0a1cabee6d5e 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -294,11 +294,6 @@ EXPORT_SYMBOL(sysctl_tcp_mem);
 atomic_long_t tcp_memory_allocated;	/* Current allocated memory. */
 EXPORT_SYMBOL(tcp_memory_allocated);
 
-#if IS_ENABLED(CONFIG_SMC)
-DEFINE_STATIC_KEY_FALSE(tcp_have_smc);
-EXPORT_SYMBOL(tcp_have_smc);
-#endif
-
 /*
  * Current number of TCP sockets.
  */
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 1950ff80fb3f..af8f4f9fd098 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3671,24 +3671,6 @@ static void tcp_parse_fastopen_option(int len, const unsigned char *cookie,
 	foc->exp = exp_opt;
 }
 
-static int smc_parse_options(const struct tcphdr *th,
-			     struct tcp_options_received *opt_rx,
-			     const unsigned char *ptr,
-			     int opsize)
-{
-#if IS_ENABLED(CONFIG_SMC)
-	if (static_branch_unlikely(&tcp_have_smc)) {
-		if (th->syn && !(opsize & 1) &&
-		    opsize >= TCPOLEN_EXP_SMC_BASE &&
-		    get_unaligned_be32(ptr) == TCPOPT_SMC_MAGIC) {
-			opt_rx->smc_ok = 1;
-			return 1;
-		}
-	}
-#endif
-	return 0;
-}
-
 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
  * But, this can also be called on packets in the established flow when
  * the fast version below fails.
@@ -3796,9 +3778,6 @@ void tcp_parse_options(const struct net *net,
 					tcp_parse_fastopen_option(opsize -
 						TCPOLEN_EXP_FASTOPEN_BASE,
 						ptr + 2, th->syn, foc, true);
-				else if (smc_parse_options(th, opt_rx, ptr,
-							   opsize))
-					break;
 				else if (opsize >= TCPOLEN_EXP_BASE)
 					tcp_extopt_parse(get_unaligned_be32(ptr),
 							 opsize, ptr, skb,
@@ -5572,16 +5551,6 @@ static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
 	return false;
 }
 
-static void smc_check_reset_syn(struct tcp_sock *tp)
-{
-#if IS_ENABLED(CONFIG_SMC)
-	if (static_branch_unlikely(&tcp_have_smc)) {
-		if (tp->syn_smc && !tp->rx_opt.smc_ok)
-			tp->syn_smc = 0;
-	}
-#endif
-}
-
 static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
 					 const struct tcphdr *th)
 {
@@ -5692,8 +5661,6 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
 		 * is initialized. */
 		tp->copied_seq = tp->rcv_nxt;
 
-		smc_check_reset_syn(tp);
-
 		smp_mb();
 
 		tcp_finish_connect(sk, skb);
@@ -6150,9 +6117,6 @@ static void tcp_openreq_init(struct request_sock *req,
 	ireq->ir_rmt_port = tcp_hdr(skb)->source;
 	ireq->ir_num = ntohs(tcp_hdr(skb)->dest);
 	ireq->ir_mark = inet_request_mark(sk, skb);
-#if IS_ENABLED(CONFIG_SMC)
-	ireq->smc_ok = rx_opt->smc_ok;
-#endif
 }
 
 struct request_sock *inet_reqsk_alloc(const struct request_sock_ops *ops,
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 676ad7ca13ad..aa2ff9aadad0 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -435,21 +435,6 @@ void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst)
 }
 EXPORT_SYMBOL_GPL(tcp_ca_openreq_child);
 
-static void smc_check_reset_syn_req(struct tcp_sock *oldtp,
-				    struct request_sock *req,
-				    struct tcp_sock *newtp)
-{
-#if IS_ENABLED(CONFIG_SMC)
-	struct inet_request_sock *ireq;
-
-	if (static_branch_unlikely(&tcp_have_smc)) {
-		ireq = inet_rsk(req);
-		if (oldtp->syn_smc && !ireq->smc_ok)
-			newtp->syn_smc = 0;
-	}
-#endif
-}
-
 /* This is not only more efficient than what we used to do, it eliminates
  * a lot of code duplication between IPv4/IPv6 SYN recv processing. -DaveM
  *
@@ -467,9 +452,6 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
 		struct tcp_request_sock *treq = tcp_rsk(req);
 		struct inet_connection_sock *newicsk = inet_csk(newsk);
 		struct tcp_sock *newtp = tcp_sk(newsk);
-		struct tcp_sock *oldtp = tcp_sk(sk);
-
-		smc_check_reset_syn_req(oldtp, req, newtp);
 
 		/* Now setup tcp_sock */
 		newtp->pred_flags = 0;
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 6804a9325107..baf1c913ca7f 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -398,21 +398,6 @@ static inline bool tcp_urg_mode(const struct tcp_sock *tp)
 	return tp->snd_una != tp->snd_up;
 }
 
-static void smc_options_write(__be32 *ptr, u16 *options)
-{
-#if IS_ENABLED(CONFIG_SMC)
-	if (static_branch_unlikely(&tcp_have_smc)) {
-		if (unlikely(OPTION_SMC & *options)) {
-			*ptr++ = htonl((TCPOPT_NOP  << 24) |
-				       (TCPOPT_NOP  << 16) |
-				       (TCPOPT_EXP <<  8) |
-				       (TCPOLEN_EXP_SMC_BASE));
-			*ptr++ = htonl(TCPOPT_SMC_MAGIC);
-		}
-	}
-#endif
-}
-
 /* Write previously computed TCP options to the packet.
  *
  * Beware: Something in the Internet is very sensitive to the ordering of
@@ -527,45 +512,10 @@ static void tcp_options_write(__be32 *ptr, struct sk_buff *skb, struct sock *sk,
 		ptr += (len + 3) >> 2;
 	}
 
-	smc_options_write(ptr, &options);
-
 	if (unlikely(!hlist_empty(extopt_list)))
 		tcp_extopt_write(ptr, skb, opts, sk);
 }
 
-static void smc_set_option(const struct tcp_sock *tp,
-			   struct tcp_out_options *opts,
-			   unsigned int *remaining)
-{
-#if IS_ENABLED(CONFIG_SMC)
-	if (static_branch_unlikely(&tcp_have_smc)) {
-		if (tp->syn_smc) {
-			if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
-				opts->options |= OPTION_SMC;
-				*remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
-			}
-		}
-	}
-#endif
-}
-
-static void smc_set_option_cond(const struct tcp_sock *tp,
-				const struct inet_request_sock *ireq,
-				struct tcp_out_options *opts,
-				unsigned int *remaining)
-{
-#if IS_ENABLED(CONFIG_SMC)
-	if (static_branch_unlikely(&tcp_have_smc)) {
-		if (tp->syn_smc && ireq->smc_ok) {
-			if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
-				opts->options |= OPTION_SMC;
-				*remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
-			}
-		}
-	}
-#endif
-}
-
 /* Compute TCP options for SYN packets. This is not the final
  * network wire format yet.
  */
@@ -631,8 +581,6 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
 		}
 	}
 
-	smc_set_option(tp, opts, &remaining);
-
 	if (unlikely(!hlist_empty(&tp->tcp_option_list)))
 		remaining -= tcp_extopt_prepare(skb, TCPHDR_SYN, remaining,
 						opts, tcp_to_sk(tp));
@@ -698,8 +646,6 @@ static unsigned int tcp_synack_options(const struct sock *sk,
 		}
 	}
 
-	smc_set_option_cond(tcp_sk(sk), ireq, opts, &remaining);
-
 	if (unlikely(!hlist_empty(&tcp_rsk(req)->tcp_option_list)))
 		remaining -= tcp_extopt_prepare(skb, TCPHDR_SYN | TCPHDR_ACK,
 						remaining, opts,
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index daf8075f5a4c..14bb84f81a50 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -44,6 +44,149 @@
 #include "smc_rx.h"
 #include "smc_close.h"
 
+static unsigned int tcp_smc_opt_prepare(struct sk_buff *skb, u8 flags,
+					unsigned int remaining,
+					struct tcp_out_options *opts,
+					const struct sock *sk,
+					struct tcp_extopt_store *store);
+static __be32 *tcp_smc_opt_write(__be32 *ptr, struct sk_buff *skb,
+				 struct tcp_out_options *opts,
+				 struct sock *sk,
+				 struct tcp_extopt_store *store);
+static void tcp_smc_opt_parse(int opsize, const unsigned char *opptr,
+			      const struct sk_buff *skb,
+			      struct tcp_options_received *opt_rx,
+			      struct sock *sk,
+			      struct tcp_extopt_store *store);
+static void tcp_smc_opt_post_process(struct sock *sk,
+				     struct tcp_options_received *opt,
+				     struct tcp_extopt_store *store);
+static struct tcp_extopt_store *tcp_smc_opt_copy(struct sock *listener,
+						 struct request_sock *req,
+						 struct tcp_options_received *opt,
+						 struct tcp_extopt_store *store);
+static void tcp_smc_opt_destroy(struct tcp_extopt_store *store);
+
+struct tcp_smc_opt {
+	struct tcp_extopt_store	store;
+	int			smc_ok:1; /* SMC supported on this connection */
+	struct rcu_head		rcu;
+};
+
+static const struct tcp_extopt_ops tcp_smc_extra_ops = {
+	.option_kind	= TCPOPT_SMC_MAGIC,
+	.parse		= tcp_smc_opt_parse,
+	.post_process	= tcp_smc_opt_post_process,
+	.prepare	= tcp_smc_opt_prepare,
+	.write		= tcp_smc_opt_write,
+	.copy		= tcp_smc_opt_copy,
+	.destroy	= tcp_smc_opt_destroy,
+	.owner		= THIS_MODULE,
+};
+
+static struct tcp_smc_opt *tcp_extopt_to_smc(struct tcp_extopt_store *store)
+{
+	return container_of(store, struct tcp_smc_opt, store);
+}
+
+static struct tcp_smc_opt *tcp_smc_opt_find(struct sock *sk)
+{
+	struct tcp_extopt_store *ext_opt;
+
+	ext_opt = tcp_extopt_find_kind(TCPOPT_SMC_MAGIC, sk);
+
+	return tcp_extopt_to_smc(ext_opt);
+}
+
+static unsigned int tcp_smc_opt_prepare(struct sk_buff *skb, u8 flags,
+					unsigned int remaining,
+					struct tcp_out_options *opts,
+					const struct sock *sk,
+					struct tcp_extopt_store *store)
+{
+	if (!(flags & TCPHDR_SYN))
+		return 0;
+
+	if (remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
+		opts->options |= OPTION_SMC;
+		return TCPOLEN_EXP_SMC_BASE_ALIGNED;
+	}
+
+	return 0;
+}
+
+static __be32 *tcp_smc_opt_write(__be32 *ptr, struct sk_buff *skb,
+				 struct tcp_out_options *opts,
+				 struct sock *sk,
+				 struct tcp_extopt_store *store)
+{
+	if (unlikely(OPTION_SMC & opts->options)) {
+		*ptr++ = htonl((TCPOPT_NOP  << 24) |
+			       (TCPOPT_NOP  << 16) |
+			       (TCPOPT_EXP <<  8) |
+			       (TCPOLEN_EXP_SMC_BASE));
+		*ptr++ = htonl(TCPOPT_SMC_MAGIC);
+	}
+
+	return ptr;
+}
+
+static void tcp_smc_opt_parse(int opsize, const unsigned char *opptr,
+			      const struct sk_buff *skb,
+			      struct tcp_options_received *opt_rx,
+			      struct sock *sk,
+			      struct tcp_extopt_store *store)
+{
+	struct tcphdr *th = tcp_hdr(skb);
+
+	if (th->syn && !(opsize & 1) && opsize >= TCPOLEN_EXP_SMC_BASE)
+		opt_rx->smc_ok = 1;
+}
+
+static void tcp_smc_opt_post_process(struct sock *sk,
+				     struct tcp_options_received *opt,
+				     struct tcp_extopt_store *store)
+{
+	struct tcp_smc_opt *smc_opt = tcp_extopt_to_smc(store);
+
+	if (sk->sk_state != TCP_SYN_SENT)
+		return;
+
+	if (opt->smc_ok)
+		smc_opt->smc_ok = 1;
+	else
+		smc_opt->smc_ok = 0;
+}
+
+static struct tcp_extopt_store *tcp_smc_opt_copy(struct sock *listener,
+						 struct request_sock *req,
+						 struct tcp_options_received *opt,
+						 struct tcp_extopt_store *store)
+{
+	struct tcp_smc_opt *smc_opt;
+
+	/* First, check if the peer sent us the smc-opt */
+	if (!opt->smc_ok)
+		return NULL;
+
+	smc_opt = kzalloc(sizeof(*smc_opt), GFP_ATOMIC);
+	if (!smc_opt)
+		return NULL;
+
+	smc_opt->store.ops = &tcp_smc_extra_ops;
+
+	smc_opt->smc_ok = 1;
+
+	return (struct tcp_extopt_store *)smc_opt;
+}
+
+static void tcp_smc_opt_destroy(struct tcp_extopt_store *store)
+{
+	struct tcp_smc_opt *smc_opt = tcp_extopt_to_smc(store);
+
+	kfree_rcu(smc_opt, rcu);
+}
+
 static DEFINE_MUTEX(smc_create_lgr_pending);	/* serialize link group
 						 * creation
 						 */
@@ -384,13 +527,15 @@ static int smc_connect_rdma(struct smc_sock *smc)
 	struct smc_clc_msg_accept_confirm aclc;
 	int local_contact = SMC_FIRST_CONTACT;
 	struct smc_ib_device *smcibdev;
+	struct tcp_smc_opt *smc_opt;
 	struct smc_link *link;
 	u8 srv_first_contact;
 	int reason_code = 0;
 	int rc = 0;
 	u8 ibport;
 
-	if (!tcp_sk(smc->clcsock->sk)->syn_smc) {
+	smc_opt = tcp_smc_opt_find(smc->clcsock->sk);
+	if (!smc_opt || !smc_opt->smc_ok) {
 		/* peer has not signalled SMC-capability */
 		smc->use_fallback = true;
 		goto out_connected;
@@ -535,6 +680,7 @@ static int smc_connect_rdma(struct smc_sock *smc)
 static int smc_connect(struct socket *sock, struct sockaddr *addr,
 		       int alen, int flags)
 {
+	struct tcp_smc_opt *smc_opt;
 	struct sock *sk = sock->sk;
 	struct smc_sock *smc;
 	int rc = -EINVAL;
@@ -548,9 +694,17 @@ static int smc_connect(struct socket *sock, struct sockaddr *addr,
 		goto out_err;
 	smc->addr = addr;	/* needed for nonblocking connect */
 
+	smc_opt = kzalloc(sizeof(*smc_opt), GFP_KERNEL);
+	if (!smc_opt) {
+		rc = -ENOMEM;
+		goto out_err;
+	}
+	smc_opt->store.ops = &tcp_smc_extra_ops;
+
 	lock_sock(sk);
 	switch (sk->sk_state) {
 	default:
+		rc = -EINVAL;
 		goto out;
 	case SMC_ACTIVE:
 		rc = -EISCONN;
@@ -560,8 +714,15 @@ static int smc_connect(struct socket *sock, struct sockaddr *addr,
 		break;
 	}
 
+	/* We are the only owner of smc->clcsock->sk, so we can be lockless */
+	rc = tcp_register_extopt(&smc_opt->store, smc->clcsock->sk);
+	if (rc) {
+		release_sock(smc->clcsock->sk);
+		kfree(smc_opt);
+		goto out_err;
+	}
+
 	smc_copy_sock_settings_to_clc(smc);
-	tcp_sk(smc->clcsock->sk)->syn_smc = 1;
 	rc = kernel_connect(smc->clcsock, addr, alen, flags);
 	if (rc)
 		goto out;
@@ -760,6 +921,7 @@ static void smc_listen_work(struct work_struct *work)
 	struct smc_clc_msg_proposal *pclc;
 	struct smc_ib_device *smcibdev;
 	struct sockaddr_in peeraddr;
+	struct tcp_smc_opt *smc_opt;
 	u8 buf[SMC_CLC_MAX_LEN];
 	struct smc_link *link;
 	int reason_code = 0;
@@ -769,7 +931,8 @@ static void smc_listen_work(struct work_struct *work)
 	u8 ibport;
 
 	/* check if peer is smc capable */
-	if (!tcp_sk(newclcsock->sk)->syn_smc) {
+	smc_opt = tcp_smc_opt_find(newclcsock->sk);
+	if (!smc_opt || !smc_opt->smc_ok) {
 		new_smc->use_fallback = true;
 		goto out_connected;
 	}
@@ -962,10 +1125,18 @@ static void smc_tcp_listen_work(struct work_struct *work)
 
 static int smc_listen(struct socket *sock, int backlog)
 {
+	struct tcp_smc_opt *smc_opt;
 	struct sock *sk = sock->sk;
 	struct smc_sock *smc;
 	int rc;
 
+	smc_opt = kzalloc(sizeof(*smc_opt), GFP_KERNEL);
+	if (!smc_opt) {
+		rc = -ENOMEM;
+		goto out_err;
+	}
+	smc_opt->store.ops = &tcp_smc_extra_ops;
+
 	smc = smc_sk(sk);
 	lock_sock(sk);
 
@@ -978,11 +1149,19 @@ static int smc_listen(struct socket *sock, int backlog)
 		sk->sk_max_ack_backlog = backlog;
 		goto out;
 	}
+
+	/* We are the only owner of smc->clcsock->sk, so we can be lockless */
+	rc = tcp_register_extopt(&smc_opt->store, smc->clcsock->sk);
+	if (rc) {
+		release_sock(smc->clcsock->sk);
+		kfree(smc_opt);
+		goto out_err;
+	}
+
 	/* some socket options are handled in core, so we could not apply
 	 * them to the clc socket -- copy smc socket options to clc socket
 	 */
 	smc_copy_sock_settings_to_clc(smc);
-	tcp_sk(smc->clcsock->sk)->syn_smc = 1;
 
 	rc = kernel_listen(smc->clcsock, backlog);
 	if (rc)
@@ -995,6 +1174,7 @@ static int smc_listen(struct socket *sock, int backlog)
 
 out:
 	release_sock(sk);
+out_err:
 	return rc;
 }
 
@@ -1425,7 +1605,6 @@ static int __init smc_init(void)
 		goto out_sock;
 	}
 
-	static_branch_enable(&tcp_have_smc);
 	return 0;
 
 out_sock:
@@ -1450,7 +1629,6 @@ static void __exit smc_exit(void)
 		list_del_init(&lgr->list);
 		smc_lgr_free(lgr); /* free link group */
 	}
-	static_branch_disable(&tcp_have_smc);
 	smc_ib_unregister_client();
 	sock_unregister(PF_SMC);
 	proto_unregister(&smc_proto);
-- 
2.15.0

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