tcp: ULP infrastructure

Add the infrustructure for attaching Upper Layer Protocols (ULPs) over TCP
sockets. Based on a similar infrastructure in tcp_cong.  The idea is that any
ULP can add its own logic by changing the TCP proto_ops structure to its own
methods.

Example usage:

setsockopt(sock, SOL_TCP, TCP_ULP, "tls", sizeof("tls"));

modules will call:
tcp_register_ulp(&tcp_tls_ulp_ops);

to register/unregister their ulp, with an init function and name.

A list of registered ulps will be returned by tcp_get_available_ulp, which is
hooked up to /proc.  Example:

$ cat /proc/sys/net/ipv4/tcp_available_ulp
tls

There is currently no functionality to remove or chain ULPs, but
it should be possible to add these in the future if needed.

Signed-off-by: Boris Pismenny <borisp@mellanox.com>
Signed-off-by: Dave Watson <davejwatson@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 30 insertions, 0 deletions

diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
index c7a577976bec..13e4c89a8231 100644
--- a/include/net/inet_connection_sock.h
+++ b/include/net/inet_connection_sock.h
@@ -75,6 +75,8 @@ struct inet_connection_sock_af_ops {
  * @icsk_pmtu_cookie	   Last pmtu seen by socket
  * @icsk_ca_ops		   Pluggable congestion control hook
  * @icsk_af_ops		   Operations which are AF_INET{4,6} specific
+ * @icsk_ulp_ops	   Pluggable ULP control hook
+ * @icsk_ulp_data	   ULP private data
  * @icsk_ca_state:	   Congestion control state
  * @icsk_retransmits:	   Number of unrecovered [RTO] timeouts
  * @icsk_pending:	   Scheduled timer event
@@ -97,6 +99,8 @@ struct inet_connection_sock {
 	__u32			  icsk_pmtu_cookie;
 	const struct tcp_congestion_ops *icsk_ca_ops;
 	const struct inet_connection_sock_af_ops *icsk_af_ops;
+	const struct tcp_ulp_ops  *icsk_ulp_ops;
+	void			  *icsk_ulp_data;
 	unsigned int		  (*icsk_sync_mss)(struct sock *sk, u32 pmtu);
 	__u8			  icsk_ca_state:6,
 				  icsk_ca_setsockopt:1,
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 3ab677d11d02..b439f46f149c 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1991,4 +1991,29 @@ static inline void tcp_listendrop(const struct sock *sk)
 
 enum hrtimer_restart tcp_pace_kick(struct hrtimer *timer);
 
+/*
+ * Interface for adding Upper Level Protocols over TCP
+ */
+
+#define TCP_ULP_NAME_MAX	16
+#define TCP_ULP_MAX		128
+#define TCP_ULP_BUF_MAX		(TCP_ULP_NAME_MAX*TCP_ULP_MAX)
+
+struct tcp_ulp_ops {
+	struct list_head	list;
+
+	/* initialize ulp */
+	int (*init)(struct sock *sk);
+	/* cleanup ulp */
+	void (*release)(struct sock *sk);
+
+	char		name[TCP_ULP_NAME_MAX];
+	struct module	*owner;
+};
+int tcp_register_ulp(struct tcp_ulp_ops *type);
+void tcp_unregister_ulp(struct tcp_ulp_ops *type);
+int tcp_set_ulp(struct sock *sk, const char *name);
+void tcp_get_available_ulp(char *buf, size_t len);
+void tcp_cleanup_ulp(struct sock *sk);
+
 #endif	/* _TCP_H */
diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index 38a2b07afdff..8204dcebc6f3 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -117,6 +117,7 @@ enum {
 #define TCP_SAVED_SYN		28	/* Get SYN headers recorded for connection */
 #define TCP_REPAIR_WINDOW	29	/* Get/set window parameters */
 #define TCP_FASTOPEN_CONNECT	30	/* Attempt FastOpen with connect */
+#define TCP_ULP		31	/* Attach a ULP to a TCP connection */
 
 struct tcp_repair_opt {
 	__u32	opt_code;