Support Unix domain sockets and emulate socketpair on Windows

Changes

@@ -10,6 +10,10 @@ Working version
 
 ### Other libraries:
 
+- #10192: Add support for Unix domain sockets on Windows and use them
+  to emulate Unix.socketpair (only available on Windows 1803+)
+  (Antonin Décimo, review by David Allsopp)
+
 ### Tools:
 
 ### Manual and documentation:

configure.ac

@@ -1391,7 +1391,8 @@ sockets=true
 AS_CASE([$host],
   [*-*-mingw32|*-pc-windows],
     [cclibs="$cclibs -lws2_32"
-    AC_SEARCH_LIBS([socket], [ws2_32])],
+    AC_SEARCH_LIBS([socket], [ws2_32])
+    AC_CHECK_FUNC([socketpair], [AC_DEFINE([HAS_SOCKETPAIR])])],
   [*-*-haiku],
     [cclibs="$cclibs -lnetwork"
     AC_SEARCH_LIBS([socket], [network])],
@@ -1420,6 +1421,13 @@ AS_CASE([$host],
 
 AC_CHECK_FUNC([inet_aton], [AC_DEFINE([HAS_INET_ATON])])
 
+## Unix domain sockets support on Windows
+
+AS_CASE([$host],
+  [*-*-mingw32|*-pc-windows],
+    [AC_CHECK_HEADERS([afunix.h], [AC_DEFINE([HAS_AFUNIX_H])], [],
+      [#include <winsock2.h>])])
+
 ## IPv6 support
 
 ipv6=true

manual/src/library/libunix.etex

@@ -90,7 +90,7 @@ processes}
 \entree{"getpwnam", "getpwuid"}{always raise "Not_found"}
 \entree{"getgrnam", "getgrgid"}{always raise "Not_found"}
 \entree{type "socket_domain"}{"PF_INET" is fully supported;
-"PF_INET6" is fully supported (since 4.01.0); "PF_UNIX" is not supported }
+"PF_INET6" is fully supported (since 4.01.0); "PF_UNIX" is supported since 4.14.0, but only works on Windows 10 1803 and later.}
 \entree{"establish_server"}{not implemented; use threads}
 \entree{terminal functions ("tc*")}{not implemented}
 \entree{"setsid"}{not implemented}

otherlibs/unix/socketaddr.c

@@ -55,7 +55,6 @@ void get_sockaddr(value mladr,
                   socklen_param_type * adr_len /*out*/)
 {
   switch(Tag_val(mladr)) {
-#ifndef _WIN32
   case 0:                       /* ADDR_UNIX */
     { value path;
       mlsize_t len;
@@ -75,7 +74,6 @@ void get_sockaddr(value mladr,
         + len;
       break;
     }
-#endif
   case 1:                       /* ADDR_INET */
 #ifdef HAS_IPV6
     if (caml_string_length(Field(mladr, 0)) == 16) {
@@ -114,16 +112,13 @@ value alloc_sockaddr(union sock_addr_union * adr /*in*/,
                      socklen_param_type adr_len, int close_on_error)
 {
   value res;
-#ifndef _WIN32
   if (adr_len < offsetof(struct sockaddr, sa_data)) {
     // Only possible for an unnamed AF_UNIX socket, in
     // which case sa_family might be uninitialized.
     return alloc_unix_sockaddr(caml_alloc_string(0));
   }
-#endif
 
   switch(adr->s_gen.sa_family) {
-#ifndef _WIN32
   case AF_UNIX:
     { /* Based on recommendation in section BUGS of Linux unix(7). See
          http://man7.org/linux/man-pages/man7/unix.7.html. */
@@ -147,7 +142,6 @@ value alloc_sockaddr(union sock_addr_union * adr /*in*/,
       );
       break;
     }
-#endif
   case AF_INET:
     { value a = alloc_inet_addr(&adr->s_inet.sin_addr);
       Begin_root (a);

otherlibs/unix/socketaddr.h

@@ -17,7 +17,27 @@
 #define CAML_SOCKETADDR_H
 
 #include "caml/misc.h"
-#ifndef _WIN32
+
+#ifdef _WIN32
+
+/* Code duplication with runtime/debugger.c is inevitable, because
+ * pulling winsock2.h creates many naming conflicts. */
+#include <winsock2.h>
+#ifdef HAS_AFUNIX_H
+#include <afunix.h>
+#else
+#define UNIX_PATH_MAX 108
+
+struct sockaddr_un {
+  ADDRESS_FAMILY sun_family;
+  char sun_path[UNIX_PATH_MAX];
+};
+
+#define SIO_AF_UNIX_GETPEERPID _WSAIOR(IOC_VENDOR, 256)
+
+#endif
+
+#else
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <sys/un.h>
@@ -27,9 +47,7 @@
 
 union sock_addr_union {
   struct sockaddr s_gen;
-#ifndef _WIN32
   struct sockaddr_un s_unix;
-#endif
   struct sockaddr_in s_inet;
 #ifdef HAS_IPV6
   struct sockaddr_in6 s_inet6;

otherlibs/unix/unix.mli

@@ -1403,7 +1403,8 @@ type socket_domain =
 (** The type of socket domains.  Not all platforms support
     IPv6 sockets (type [PF_INET6]).
 
-    On Windows: [PF_UNIX] not implemented.  *)
+   On Windows: [PF_UNIX] supported since 4.14.0 on Windows 10 1803
+   and later.  *)
 
 type socket_type =
     SOCK_STREAM                 (** Stream socket *)

otherlibs/unix/unixLabels.mli

@@ -1403,7 +1403,8 @@ type socket_domain = Unix.socket_domain =
 (** The type of socket domains.  Not all platforms support
     IPv6 sockets (type [PF_INET6]).
 
-    On Windows: [PF_UNIX] not implemented.  *)
+   On Windows: [PF_UNIX] supported since 4.14.0 on Windows 10 1803
+   and later.  *)
 
 type socket_type = Unix.socket_type =
     SOCK_STREAM                 (** Stream socket *)

otherlibs/win32unix/Makefile

@@ -24,7 +24,7 @@ WIN_FILES = accept.c bind.c channels.c close.c \
   link.c listen.c lockf.c lseek.c nonblock.c \
   mmap.c open.c pipe.c read.c readlink.c rename.c \
   realpath.c select.c sendrecv.c \
-  shutdown.c sleep.c socket.c sockopt.c startup.c stat.c \
+  shutdown.c sleep.c socket.c socketpair.c sockopt.c startup.c stat.c \
   symlink.c system.c times.c truncate.c unixsupport.c windir.c winwait.c \
   write.c winlist.c winworker.c windbug.c utimes.c
 

otherlibs/win32unix/accept.c

@@ -38,10 +38,7 @@ CAMLprim value unix_accept(value cloexec, value sock)
     win32_maperr(err);
     uerror("accept", Nothing);
   }
-  /* This is a best effort, not guaranteed to work, so don't fail on error */
-  SetHandleInformation((HANDLE) snew,
-                       HANDLE_FLAG_INHERIT,
-                       unix_cloexec_p(cloexec) ? 0 : HANDLE_FLAG_INHERIT);
+  win_set_cloexec((HANDLE) snew, cloexec);
   Begin_roots2 (fd, adr)
     fd = win_alloc_socket(snew);
     adr = alloc_sockaddr(&addr, addr_len, snew);

otherlibs/win32unix/close_on.c

@@ -17,27 +17,16 @@
 #include "unixsupport.h"
 #include <windows.h>
 
-int win_set_inherit(value fd, BOOL inherit)
-{
-  /* According to the MSDN, SetHandleInformation may not work
-     for console handles on WinNT4 and earlier versions. */
-  if (! SetHandleInformation(Handle_val(fd),
-                             HANDLE_FLAG_INHERIT,
-                             inherit ? HANDLE_FLAG_INHERIT : 0)) {
-    win32_maperr(GetLastError());
-    return -1;
-  }
-  return 0;
-}
-
 CAMLprim value win_set_close_on_exec(value fd)
 {
-  if (win_set_inherit(fd, FALSE) == -1) uerror("set_close_on_exec", Nothing);
+  if (win_set_inherit(Handle_val(fd), FALSE) == -1)
+    uerror("set_close_on_exec", Nothing);
   return Val_unit;
 }
 
 CAMLprim value win_clear_close_on_exec(value fd)
 {
-  if (win_set_inherit(fd, TRUE) == -1) uerror("clear_close_on_exec", Nothing);
+  if (win_set_inherit(Handle_val(fd), TRUE) == -1)
+    uerror("clear_close_on_exec", Nothing);
   return Val_unit;
 }

otherlibs/win32unix/socket.c

@@ -35,9 +35,6 @@ CAMLprim value unix_socket(value cloexec, value domain, value type, value proto)
     win32_maperr(WSAGetLastError());
     uerror("socket", Nothing);
   }
-  /* This is a best effort, not guaranteed to work, so don't fail on error */
-  SetHandleInformation((HANDLE) s,
-                       HANDLE_FLAG_INHERIT,
-                       unix_cloexec_p(cloexec) ? 0 : HANDLE_FLAG_INHERIT);
+  win_set_cloexec((HANDLE) s, cloexec);
   return win_alloc_socket(s);
 }