connect: Add TCP Fast Open support for WindowsTFO-windows

This is the former PR #3327, saved by Johannes Schindelin, rebased, squashed
and pushed again.

Requires Windows 10 ver 1607 or newer

1 files changed, 31 insertions, 0 deletions

diff --git a/lib/sendf.c b/lib/sendf.c
index e8598e617..2a4db3971 100644
--- a/lib/sendf.c
+++ b/lib/sendf.c
@@ -387,6 +387,37 @@ ssize_t Curl_send_plain(struct connectdata *conn, int num,
     conn->bits.tcp_fastopen = FALSE;
   }
   else
+#elif defined(HAVE_CONNECTEX)
+  if(conn->bits.tcp_fastopen && !conn->fastopen_connected) {
+    conn->fastopen_connected = TRUE;
+    bytes_written = 0;
+
+    if(!Curl_ConnectEx(sockfd,
+                       conn->ip_addr->ai_addr, conn->ip_addr->ai_addrlen,
+                       (void *)mem, (DWORD)len,
+                       (LPDWORD)&bytes_written,
+                       &conn->fastopen_state)) {
+      if(SOCKERRNO != WSA_IO_PENDING)
+        bytes_written = -1;
+      else
+        if(!GetOverlappedResult((HANDLE)sockfd, &conn->fastopen_state,
+                                (LPDWORD)&bytes_written, TRUE)) {
+          int err = GetLastError();
+          failf(conn->data, "Send failure: %s",
+                Curl_strerror(conn, err));
+          conn->data->state.os_errno = err;
+          *code = CURLE_SEND_ERROR;
+          return 0;
+        }
+    }
+
+    /* socket in default state; enable previously-set socket params */
+    if(setsockopt(sockfd, SOL_SOCKET, SO_UPDATE_CONNECT_CONTEXT, NULL, 0))
+      infof(conn->data,
+            "setsockopt() failed after TCP Fast Open for fd %d, errno: %d",
+            sockfd, SOCKERRNO);
+  }
+  else
 #endif
     bytes_written = swrite(sockfd, mem, len);