socketpair: an implemention for Windows and more

Curl_socketpair() is designed to be used and work everywhere if there's
no native version or the native version isn't good enough.

Closes #4466

lib/Makefile.inc

@@ -61,7 +61,7 @@ LIB_CFILES = file.c timeval.c base64.c hostip.c progress.c formdata.c   \
   curl_multibyte.c hostcheck.c conncache.c dotdot.c                     \
   x509asn1.c http2.c smb.c curl_endian.c curl_des.c system_win32.c      \
   mime.c sha256.c setopt.c curl_path.c curl_ctype.c curl_range.c psl.c  \
-  doh.c urlapi.c curl_get_line.c altsvc.c
+  doh.c urlapi.c curl_get_line.c altsvc.c socketpair.c
 
 LIB_HFILES = arpa_telnet.h netrc.h file.h timeval.h hostip.h progress.h \
   formdata.h cookie.h http.h sendf.h ftp.h url.h dict.h if2ip.h         \
@@ -82,7 +82,7 @@ LIB_HFILES = arpa_telnet.h netrc.h file.h timeval.h hostip.h progress.h \
   x509asn1.h http2.h sigpipe.h smb.h curl_endian.h curl_des.h           \
   curl_printf.h system_win32.h rand.h mime.h curl_sha256.h setopt.h     \
   curl_path.h curl_ctype.h curl_range.h psl.h doh.h urlapi-int.h        \
-  curl_get_line.h altsvc.h quic.h
+  curl_get_line.h altsvc.h quic.h socketpair.h
 
 LIB_RCFILES = libcurl.rc
 

lib/socketpair.c

@@ -0,0 +1,112 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+
+#include "curl_setup.h"
+#include "socketpair.h"
+
+#ifndef HAVE_SOCKETPAIR
+#ifdef WIN32
+/*
+ * This is a socketpair() implementation for Windows.
+ */
+#include <string.h>
+#include <winsock2.h>
+#include <ws2tcpip.h>
+#include <windows.h>
+#include <io.h>
+#else
+#ifdef HAVE_NETDB_H
+#include <netdb.h>
+#endif
+#endif /* !WIN32 */
+
+/* The last 3 #include files should be in this order */
+#include "curl_printf.h"
+#include "curl_memory.h"
+#include "memdebug.h"
+
+int Curl_socketpair(int domain, int type, int protocol,
+                    curl_socket_t socks[2])
+{
+  union {
+    struct sockaddr_in inaddr;
+    struct sockaddr addr;
+  } a;
+  curl_socket_t listener;
+  curl_socklen_t addrlen = sizeof(a.inaddr);
+  int reuse = 1;
+  char data[2][12];
+  ssize_t dlen;
+  (void)domain;
+  (void)type;
+  (void)protocol;
+
+  listener = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
+  if(listener == CURL_SOCKET_BAD)
+    return -1;
+
+  memset(&a, 0, sizeof(a));
+  a.inaddr.sin_family = AF_INET;
+  a.inaddr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+  a.inaddr.sin_port = 0;
+
+  socks[0] = socks[1] = CURL_SOCKET_BAD;
+
+  if(setsockopt(listener, SOL_SOCKET, SO_REUSEADDR,
+                (char *)&reuse, (curl_socklen_t)sizeof(reuse)) == -1)
+    goto error;
+  if(bind(listener, &a.addr, sizeof(a.inaddr)) == -1)
+    goto error;
+  if(getsockname(listener, &a.addr, &addrlen) == -1)
+    goto error;
+  if(listen(listener, 1) == -1)
+    goto error;
+  socks[0] = socket(AF_INET, SOCK_STREAM, 0);
+  if(socks[0] == CURL_SOCKET_BAD)
+    goto error;
+  if(connect(socks[0], &a.addr, sizeof(a.inaddr)) == -1)
+    goto error;
+  socks[1] = accept(listener, NULL, NULL);
+  if(socks[1] == CURL_SOCKET_BAD)
+    goto error;
+
+  sclose(listener);
+
+  /* verify that nothing else connected */
+  msnprintf(data[0], sizeof(data[0]), "%p", socks);
+  dlen = strlen(data[0]);
+  if(swrite(socks[0], data[0], dlen) != dlen)
+    goto error;
+  if(sread(socks[1], data[1], sizeof(data[1])) != dlen)
+    goto error;
+  if(memcmp(data[0], data[1], dlen))
+    goto error;
+  return 0;
+
+  error:
+  sclose(listener);
+  sclose(socks[0]);
+  sclose(socks[1]);
+  return -1;
+}
+
+#endif /* ! HAVE_SOCKETPAIR */

lib/socketpair.h

@@ -0,0 +1,36 @@
+#ifndef HEADER_CURL_SOCKETPAIR_H
+#define HEADER_CURL_SOCKETPAIR_H
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+
+#include "curl_setup.h"
+#ifndef HAVE_SOCKETPAIR
+int Curl_socketpair(int domain, int type, int protocol,
+                    curl_socket_t socks[2]);
+#else
+#define Curl_socketpair(a,b,c,d) socketpair(a,b,c,d)
+#endif
+
+/* Defined here to allow specific build configs to disable it completely */
+#define USE_SOCKETPAIR 1
+
+#endif /* HEADER_CURL_SOCKETPAIR_H */