connect: implement TCP Fast Open for Linux

Closes #660

4 files changed, 20 insertions, 6 deletions

diff --git a/docs/libcurl/opts/CURLOPT_TCP_FASTOPEN.3 b/docs/libcurl/opts/CURLOPT_TCP_FASTOPEN.3
index 6f6ddba72..f8f934384 100644
--- a/docs/libcurl/opts/CURLOPT_TCP_FASTOPEN.3
+++ b/docs/libcurl/opts/CURLOPT_TCP_FASTOPEN.3
@@ -40,7 +40,8 @@ All
 .SH EXAMPLE
 TODO
 .SH AVAILABILITY
-Added in 7.49.0. This option is currently only supported on OS X El Capitan.
+Added in 7.49.0. This option is currently only supported on Linux and  OS X
+El Capitan.
 .SH RETURN VALUE
 Returns CURLE_OK if fast open is supported by the operating system, otherwise
 returns CURLE_NOT_BUILT_IN.
diff --git a/lib/connect.c b/lib/connect.c
index a4eb56d00..bfc22992c 100644
--- a/lib/connect.c
+++ b/lib/connect.c
@@ -668,7 +668,7 @@ void Curl_updateconninfo(struct connectdata *conn, curl_socket_t sockfd)
     /* there's no connection! */
     return;
 
-  if(!conn->bits.reuse) {
+  if(!conn->bits.reuse && !conn->bits.tcp_fastopen) {
     int error;
 
     len = sizeof(struct Curl_sockaddr_storage);
@@ -776,7 +776,7 @@ CURLcode Curl_is_connected(struct connectdata *conn,
         trynextip(conn, sockindex, 1);
       }
     }
-    else if(rc == CURL_CSELECT_OUT) {
+    else if(rc == CURL_CSELECT_OUT || conn->bits.tcp_fastopen) {
       if(verifyconnect(conn->tempsock[i], &error)) {
         /* we are connected with TCP, awesome! */
 
@@ -1109,6 +1109,8 @@ static CURLcode singleipconnect(struct connectdata *conn,
       rc = connectx(sockfd, &endpoints, SAE_ASSOCID_ANY,
                     CONNECT_RESUME_ON_READ_WRITE | CONNECT_DATA_IDEMPOTENT,
                     NULL, 0, NULL, NULL);
+#elif defined(MSG_FASTOPEN) /* Linux */
+      rc = 0; /* Do nothing */
 #endif
     }
     else {
diff --git a/lib/sendf.c b/lib/sendf.c
index ea04ae83e..a75c5c743 100644
--- a/lib/sendf.c
+++ b/lib/sendf.c
@@ -254,7 +254,17 @@ ssize_t Curl_send_plain(struct connectdata *conn, int num,
                         const void *mem, size_t len, CURLcode *code)
 {
   curl_socket_t sockfd = conn->sock[num];
-  ssize_t bytes_written = swrite(sockfd, mem, len);
+  ssize_t bytes_written;
+
+#ifdef MSG_FASTOPEN /* Linux */
+  if(conn->bits.tcp_fastopen) {
+    bytes_written = sendto(sockfd, mem, len, MSG_FASTOPEN,
+                           conn->ip_addr->ai_addr, conn->ip_addr->ai_addrlen);
+    conn->bits.tcp_fastopen = FALSE;
+  }
+  else
+#endif
+    bytes_written = swrite(sockfd, mem, len);
 
   *code = CURLE_OK;
   if(-1 == bytes_written) {
@@ -268,7 +278,8 @@ ssize_t Curl_send_plain(struct connectdata *conn, int num,
       /* errno may be EWOULDBLOCK or on some systems EAGAIN when it returned
          due to its inability to send off data without blocking. We therefor
          treat both error codes the same here */
-      (EWOULDBLOCK == err) || (EAGAIN == err) || (EINTR == err)
+      (EWOULDBLOCK == err) || (EAGAIN == err) || (EINTR == err) ||
+      (EINPROGRESS == err)
 #endif
       ) {
       /* this is just a case of EWOULDBLOCK */
diff --git a/lib/url.c b/lib/url.c
index e76d4e8e0..f1028f34c 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -2633,7 +2633,7 @@ CURLcode Curl_setopt(struct SessionHandle *data, CURLoption option,
     data->set.tcp_keepintvl = va_arg(param, long);
     break;
   case CURLOPT_TCP_FASTOPEN:
-#if defined(CONNECT_DATA_IDEMPOTENT)
+#if defined(CONNECT_DATA_IDEMPOTENT) || defined(MSG_FASTOPEN)
     data->set.tcp_fastopen = (0 != va_arg(param, long))?TRUE:FALSE;
 #else
     result = CURLE_NOT_BUILT_IN;