net-tcp: Fast Open client - sendmsg(MSG_FASTOPEN)

sendmsg() (or sendto()) with MSG_FASTOPEN is a combo of connect(2)
and write(2). The application should replace connect() with it to
send data in the opening SYN packet.

For blocking socket, sendmsg() blocks until all the data are buffered
locally and the handshake is completed like connect() call. It
returns similar errno like connect() if the TCP handshake fails.

For non-blocking socket, it returns the number of bytes queued (and
transmitted in the SYN-data packet) if cookie is available. If cookie
is not available, it transmits a data-less SYN packet with Fast Open
cookie request option and returns -EINPROGRESS like connect().

Using MSG_FASTOPEN on connecting or connected socket will result in
simlar errno like repeating connect() calls. Therefore the application
should only use this flag on new sockets.

The buffer size of sendmsg() is independent of the MSS of the connection.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index e1e021594cff4a15a5d2f81d2b0b946184c09e20..03964e088180aba20629e5271c9182b47ae6debe 100644 (file)
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -468,6 +468,17 @@ tcp_syncookies - BOOLEAN
        SYN flood warnings in logs not being really flooded, your server
        is seriously misconfigured.
 
+tcp_fastopen - INTEGER
+       Enable TCP Fast Open feature (draft-ietf-tcpm-fastopen) to send data
+       in the opening SYN packet. To use this feature, the client application
+       must not use connect(). Instead, it should use sendmsg() or sendto()
+       with MSG_FASTOPEN flag which performs a TCP handshake automatically.
+
+       The values (bitmap) are:
+       1: Enables sending data in the opening SYN on the client
+
+       Default: 0
+
 tcp_syn_retries - INTEGER
        Number of times initial SYNs for an active TCP connection attempt
        will be retransmitted. Should not be higher than 255. Default value

diff --git a/include/linux/socket.h b/include/linux/socket.h
index 25d6322fb6356a9f5369051384758d9cc0a0492a..ba7b2e817cfa9ac76a19c9e96554efd17f9f4888 100644 (file)
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -268,6 +268,7 @@ struct ucred {
 #define MSG_SENDPAGE_NOTLAST 0x20000 /* sendpage() internal : not the last page */
 #define MSG_EOF         MSG_FIN
 
+#define MSG_FASTOPEN   0x20000000      /* Send data in TCP SYN */
 #define MSG_CMSG_CLOEXEC 0x40000000    /* Set close_on_exit for file
                                           descriptor received through
                                           SCM_RIGHTS */

diff --git a/include/net/inet_common.h b/include/net/inet_common.h
index 22fac9892b160c06cecb83d8b98c9fcef155ebd8..234008782c8cca00e2af6394c17391189abd974a 100644 (file)
--- a/include/net/inet_common.h
+++ b/include/net/inet_common.h
@@ -14,9 +14,11 @@ struct sockaddr;
 struct socket;
 
 extern int inet_release(struct socket *sock);
-extern int inet_stream_connect(struct socket *sock, struct sockaddr * uaddr,
+extern int inet_stream_connect(struct socket *sock, struct sockaddr *uaddr,
                               int addr_len, int flags);
-extern int inet_dgram_connect(struct socket *sock, struct sockaddr * uaddr,
+extern int __inet_stream_connect(struct socket *sock, struct sockaddr *uaddr,
+                                int addr_len, int flags);
+extern int inet_dgram_connect(struct socket *sock, struct sockaddr *uaddr,
                              int addr_len, int flags);
 extern int inet_accept(struct socket *sock, struct socket *newsock, int flags);
 extern int inet_sendmsg(struct kiocb *iocb, struct socket *sock,

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 867557b4244a00c651f25b4729309ef3e537522f..c0258100d70cd8517f68f3a3e9e958a71b7e6143 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -212,6 +212,9 @@ extern void tcp_time_wait(struct sock *sk, int state, int timeo);
 /* TCP initial congestion window as per draft-hkchu-tcpm-initcwnd-01 */
 #define TCP_INIT_CWND          10
 
+/* Bit Flags for sysctl_tcp_fastopen */
+#define        TFO_CLIENT_ENABLE       1
+
 extern struct inet_timewait_death_row tcp_death_row;
 
 /* sysctl variables for tcp */

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index edc414625be28a5f8a19a90ee65efb39a83c7264..fe4582ca969a4ff85c862f8fd96d3b6ec3d03a4d 100644 (file)
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -585,8 +585,8 @@ static long inet_wait_for_connect(struct sock *sk, long timeo, int writebias)
  *     Connect to a remote host. There is regrettably still a little
  *     TCP 'magic' in here.
  */
-int inet_stream_connect(struct socket *sock, struct sockaddr *uaddr,
-                       int addr_len, int flags)
+int __inet_stream_connect(struct socket *sock, struct sockaddr *uaddr,
+                         int addr_len, int flags)
 {
        struct sock *sk = sock->sk;
        int err;
@@ -595,8 +595,6 @@ int inet_stream_connect(struct socket *sock, struct sockaddr *uaddr,
        if (addr_len < sizeof(uaddr->sa_family))
                return -EINVAL;
 
-       lock_sock(sk);
-
        if (uaddr->sa_family == AF_UNSPEC) {
                err = sk->sk_prot->disconnect(sk, flags);
                sock->state = err ? SS_DISCONNECTING : SS_UNCONNECTED;
@@ -663,7 +661,6 @@ int inet_stream_connect(struct socket *sock, struct sockaddr *uaddr,
        sock->state = SS_CONNECTED;
        err = 0;
 out:
-       release_sock(sk);
        return err;
 
 sock_error:
@@ -673,6 +670,18 @@ sock_error:
                sock->state = SS_DISCONNECTING;
        goto out;
 }
+EXPORT_SYMBOL(__inet_stream_connect);
+
+int inet_stream_connect(struct socket *sock, struct sockaddr *uaddr,
+                       int addr_len, int flags)
+{
+       int err;
+
+       lock_sock(sock->sk);
+       err = __inet_stream_connect(sock, uaddr, addr_len, flags);
+       release_sock(sock->sk);
+       return err;
+}
 EXPORT_SYMBOL(inet_stream_connect);
 
 /*

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 4252cd8f39fdd183c7823ec6320ddaf9ec98db30..581ecf02c6b5c06f473e89c1d644cf5744410402 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -270,6 +270,7 @@
 #include <linux/slab.h>
 
 #include <net/icmp.h>
+#include <net/inet_common.h>
 #include <net/tcp.h>
 #include <net/xfrm.h>
 #include <net/ip.h>
@@ -982,26 +983,67 @@ static inline int select_size(const struct sock *sk, bool sg)
        return tmp;
 }
 
+void tcp_free_fastopen_req(struct tcp_sock *tp)
+{
+       if (tp->fastopen_req != NULL) {
+               kfree(tp->fastopen_req);
+               tp->fastopen_req = NULL;
+       }
+}
+
+static int tcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg, int *size)
+{
+       struct tcp_sock *tp = tcp_sk(sk);
+       int err, flags;
+
+       if (!(sysctl_tcp_fastopen & TFO_CLIENT_ENABLE))
+               return -EOPNOTSUPP;
+       if (tp->fastopen_req != NULL)
+               return -EALREADY; /* Another Fast Open is in progress */
+
+       tp->fastopen_req = kzalloc(sizeof(struct tcp_fastopen_request),
+                                  sk->sk_allocation);
+       if (unlikely(tp->fastopen_req == NULL))
+               return -ENOBUFS;
+       tp->fastopen_req->data = msg;
+
+       flags = (msg->msg_flags & MSG_DONTWAIT) ? O_NONBLOCK : 0;
+       err = __inet_stream_connect(sk->sk_socket, msg->msg_name,
+                                   msg->msg_namelen, flags);
+       *size = tp->fastopen_req->copied;
+       tcp_free_fastopen_req(tp);
+       return err;
+}
+
 int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
                size_t size)
 {
        struct iovec *iov;
        struct tcp_sock *tp = tcp_sk(sk);
        struct sk_buff *skb;
-       int iovlen, flags, err, copied;
-       int mss_now = 0, size_goal;
+       int iovlen, flags, err, copied = 0;
+       int mss_now = 0, size_goal, copied_syn = 0, offset = 0;
        bool sg;
        long timeo;
 
        lock_sock(sk);
 
        flags = msg->msg_flags;
+       if (flags & MSG_FASTOPEN) {
+               err = tcp_sendmsg_fastopen(sk, msg, &copied_syn);
+               if (err == -EINPROGRESS && copied_syn > 0)
+                       goto out;
+               else if (err)
+                       goto out_err;
+               offset = copied_syn;
+       }
+
        timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
 
        /* Wait for a connection to finish. */
        if ((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
                if ((err = sk_stream_wait_connect(sk, &timeo)) != 0)
-                       goto out_err;
+                       goto do_error;
 
        if (unlikely(tp->repair)) {
                if (tp->repair_queue == TCP_RECV_QUEUE) {
@@ -1037,6 +1079,15 @@ int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
                unsigned char __user *from = iov->iov_base;
 
                iov++;
+               if (unlikely(offset > 0)) {  /* Skip bytes copied in SYN */
+                       if (offset >= seglen) {
+                               offset -= seglen;
+                               continue;
+                       }
+                       seglen -= offset;
+                       from += offset;
+                       offset = 0;
+               }
 
                while (seglen > 0) {
                        int copy = 0;
@@ -1199,7 +1250,7 @@ out:
        if (copied && likely(!tp->repair))
                tcp_push(sk, flags, mss_now, tp->nonagle);
        release_sock(sk);
-       return copied;
+       return copied + copied_syn;
 
 do_fault:
        if (!skb->len) {
@@ -1212,7 +1263,7 @@ do_fault:
        }
 
 do_error:
-       if (copied)
+       if (copied + copied_syn)
                goto out;
 out_err:
        err = sk_stream_error(sk, flags, err);

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 01aa77a9702019355691696a59b569a857b03074..1d8b75a58981a211c6cfa8bcb30af673f7a71ffe 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1952,6 +1952,9 @@ void tcp_v4_destroy_sock(struct sock *sk)
                tp->cookie_values = NULL;
        }
 
+       /* If socket is aborted during connect operation */
+       tcp_free_fastopen_req(tp);
+
        sk_sockets_allocated_dec(sk);
        sock_release_memcg(sk);
 }