tcp: Configure TFO without cookie per socket and/or per route

We already allow to enable TFO without a cookie by using the
fastopen-sysctl and setting it to TFO_SERVER_COOKIE_NOT_REQD (or
TFO_CLIENT_NO_COOKIE).
This is safe to do in certain environments where we know that there
isn't a malicous host (aka., data-centers) or when the
application-protocol already provides an authentication mechanism in the
first flight of data.

A server however might be providing multiple services or talking to both
sides (public Internet and data-center). So, this server would want to
enable cookie-less TFO for certain services and/or for connections that
go to the data-center.

This patch exposes a socket-option and a per-route attribute to enable such
fine-grained configurations.

Signed-off-by: Christoph Paasch <cpaasch@apple.com>
Reviewed-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 1d2c44e..173a7c2 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -215,7 +215,8 @@ struct tcp_sock {
 	u8	chrono_type:2,	/* current chronograph type */
 		rate_app_limited:1,  /* rate_{delivered,interval_us} limited? */
 		fastopen_connect:1, /* FASTOPEN_CONNECT sockopt */
-		unused:4;
+		fastopen_no_cookie:1, /* Allow send/recv SYN+data without a cookie */
+		unused:3;
 	u8	nonagle     : 4,/* Disable Nagle algorithm?             */
 		thin_lto    : 1,/* Use linear timeouts for thin streams */
 		unused1	    : 1,
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 2c13484..2392f74 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1567,7 +1567,8 @@ int tcp_fastopen_reset_cipher(struct net *net, struct sock *sk,
 void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb);
 struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
 			      struct request_sock *req,
-			      struct tcp_fastopen_cookie *foc);
+			      struct tcp_fastopen_cookie *foc,
+			      const struct dst_entry *dst);
 void tcp_fastopen_init_key_once(struct net *net);
 bool tcp_fastopen_cookie_check(struct sock *sk, u16 *mss,
 			     struct tcp_fastopen_cookie *cookie);
diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
index dab7dad..fe667926 100644
--- a/include/uapi/linux/rtnetlink.h
+++ b/include/uapi/linux/rtnetlink.h
@@ -430,6 +430,8 @@ enum {
 #define RTAX_QUICKACK RTAX_QUICKACK
 	RTAX_CC_ALGO,
 #define RTAX_CC_ALGO RTAX_CC_ALGO
+	RTAX_FASTOPEN_NO_COOKIE,
+#define RTAX_FASTOPEN_NO_COOKIE RTAX_FASTOPEN_NO_COOKIE
 	__RTAX_MAX
 };
 
diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index 69c7493..d67e1d4 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -120,6 +120,7 @@ enum {
 #define TCP_ULP			31	/* Attach a ULP to a TCP connection */
 #define TCP_MD5SIG_EXT		32	/* TCP MD5 Signature with extensions */
 #define TCP_FASTOPEN_KEY	33	/* Set the key for Fast Open (cookie) */
+#define TCP_FASTOPEN_NO_COOKIE	34	/* Enable TFO without a TFO cookie */
 
 struct tcp_repair_opt {
 	__u32	opt_code;