Socket API improvement, patch #6

[Ludovic Courtès]

Hi Kevin,

Kevin Ryde <address@hidden> writes:

> Looks like a memory leak here if scm_to_ulong throws an error.
> Obviously it won't normally, but a vector with any garbage could reach
> here.  Maybe build the addr on the stack then memdup.  Ditto the other
> cases.

Right, I fixed this one.

> What is #f here meant to support?

Mostly, it aims at being consistent with `_scm_from_sockaddr ()' which
may set the `path' element to `#f'.

> How about sizeof(c_unix->sun_path)?

Right, fixed.

> I think scm_to_locale_stringbuf will store nulls from the string but
> then SUN_LEN will truncate at the first one of those.  Maybe nulls in
> the SCM should be an error (per scm_to_locale_stringn).

I added a sanity check for this, too (although I'm unsure if it's really
useful).

I attach a full patch which includes the test-case too, so that we don't
have too much of a hard time keeping track of the thing.  ;-)

BTW, I should receive the papers from the FSF shortly.

Thanks,
Ludovic.


--- orig/ice-9/networking.scm
+++ mod/ice-9/networking.scm
@@ -80,3 +80,5 @@
 (define (sockaddr:path obj) (vector-ref obj 1))
 (define (sockaddr:addr obj) (vector-ref obj 1))
 (define (sockaddr:port obj) (vector-ref obj 2))
+(define (sockaddr:flowinfo obj) (vector-ref obj 3))
+(define (sockaddr:scopeid obj) (vector-ref obj 4))


--- orig/libguile/socket.c
+++ mod/libguile/socket.c
@@ -664,9 +664,9 @@
    proc is the name of the original procedure.
    size returns the size of the structure allocated.  */
 
-static struct sockaddr *
+static SCM_C_INLINE_KEYWORD struct sockaddr *
 scm_fill_sockaddr (int fam, SCM address, SCM *args, int which_arg,
-                  const char *proc, int *size)
+                  const char *proc, size_t *size)
 #define FUNC_NAME proc
 {
   switch (fam)
@@ -682,8 +682,7 @@
        port = scm_to_int (SCM_CAR (*args));
        *args = SCM_CDR (*args);
        soka = (struct sockaddr_in *) scm_malloc (sizeof (struct sockaddr_in));
-       if (!soka)
-         scm_memory_error (proc);
+
 #if HAVE_STRUCT_SOCKADDR_SIN_LEN
        soka->sin_len = sizeof (struct sockaddr_in);
 #endif
@@ -717,8 +716,7 @@
              }
          }
        soka = (struct sockaddr_in6 *) scm_malloc (sizeof (struct 
sockaddr_in6));
-       if (!soka)
-         scm_memory_error (proc);
+
 #if HAVE_STRUCT_SOCKADDR_IN6_SIN6_LEN
        soka->sin6_len = sizeof (struct sockaddr_in6);
 #endif
@@ -768,9 +766,9 @@
     }
 }
 #undef FUNC_NAME
-  
-SCM_DEFINE (scm_connect, "connect", 3, 0, 1,
-            (SCM sock, SCM fam, SCM address, SCM args),
+
+SCM_DEFINE (scm_connect, "connect", 2, 1, 1,
+            (SCM sock, SCM fam_or_sockaddr, SCM address, SCM args),
            "Initiate a connection from a socket using a specified address\n"
            "family to the address\n"
            "specified by @var{address} and possibly @var{args}.\n"
@@ -787,22 +785,32 @@
            "@var{args} may be up to three integers:\n"
            "port [flowinfo] [scope_id],\n"
            "where flowinfo and scope_id default to zero.\n\n"
+           "Alternatively, the second argument can be a socket address object "
+           "as returned by @code{make-socket-address}, in which case the "
+           "no additional arguments should be passed.\n\n"
            "The return value is unspecified.")
 #define FUNC_NAME s_scm_connect
 {
   int fd;
   struct sockaddr *soka;
-  int size;
+  size_t size;
 
   sock = SCM_COERCE_OUTPORT (sock);
   SCM_VALIDATE_OPFPORT (1, sock);
   fd = SCM_FPORT_FDES (sock);
-  soka = scm_fill_sockaddr (scm_to_int (fam), address, &args, 3, FUNC_NAME,
-                           &size);
+
+  if (address == SCM_UNDEFINED)
+    /* No third argument was passed to FAM_OR_SOCKADDR must actually be a
+       `socket address' object.  */
+    soka = scm_to_sockaddr (fam_or_sockaddr, &size);
+  else
+    soka = scm_fill_sockaddr (scm_to_int (fam_or_sockaddr), address,
+                             &args, 3, FUNC_NAME, &size);
+
   if (connect (fd, soka, size) == -1)
     {
       int save_errno = errno;
-      
+
       free (soka);
       errno = save_errno;
       SCM_SYSERROR;
@@ -812,8 +820,8 @@
 }
 #undef FUNC_NAME
 
-SCM_DEFINE (scm_bind, "bind", 3, 0, 1,
-            (SCM sock, SCM fam, SCM address, SCM args),
+SCM_DEFINE (scm_bind, "bind", 2, 1, 1,
+            (SCM sock, SCM fam_or_sockaddr, SCM address, SCM args),
            "Assign an address to the socket port @var{sock}.\n"
            "Generally this only needs to be done for server sockets,\n"
            "so they know where to look for incoming connections.  A socket\n"
@@ -846,22 +854,33 @@
            "may be up to three integers:\n"
            "port [flowinfo] [scope_id],\n"
            "where flowinfo and scope_id default to zero.\n\n"
+           "Alternatively, the second argument can be a socket address object "
+           "as returned by @code{make-socket-address}, in which case the "
+           "no additional arguments should be passed.\n\n"
            "The return value is unspecified.")
 #define FUNC_NAME s_scm_bind
 {
   struct sockaddr *soka;
-  int size;
+  size_t size;
   int fd;
 
   sock = SCM_COERCE_OUTPORT (sock);
   SCM_VALIDATE_OPFPORT (1, sock);
-  soka = scm_fill_sockaddr (scm_to_int (fam), address, &args, 3, FUNC_NAME,
-                           &size);
   fd = SCM_FPORT_FDES (sock);
+
+  if (address == SCM_UNDEFINED)
+    /* No third argument was passed to FAM_OR_SOCKADDR must actually be a
+       `socket address' object.  */
+    soka = scm_to_sockaddr (fam_or_sockaddr, &size);
+  else
+    soka = scm_fill_sockaddr (scm_to_int (fam_or_sockaddr), address,
+                             &args, 3, FUNC_NAME, &size);
+
+
   if (bind (fd, soka, size) == -1)
   {
     int save_errno = errno;
-      
+
     free (soka);
     errno = save_errno;
     SCM_SYSERROR;
@@ -893,8 +912,8 @@
 #undef FUNC_NAME
 
 /* Put the components of a sockaddr into a new SCM vector.  */
-static SCM
-scm_addr_vector (const struct sockaddr *address, int addr_size, 
+static SCM_C_INLINE_KEYWORD SCM
+_scm_from_sockaddr (const struct sockaddr *address, unsigned addr_size,
                 const char *proc)
 {
   short int fam = address->sa_family;
@@ -953,12 +972,212 @@
       break;
 #endif
     default:
-      scm_misc_error (proc, "Unrecognised address family: ~A",
+      result = SCM_UNSPECIFIED;
+      scm_misc_error (proc, "unrecognised address family: ~A",
                      scm_list_1 (scm_from_int (fam)));
+
     }
   return result;
 }
 
+/* The publicly-visible function.  Return a Scheme object representing
+   ADDRESS, an address of ADDR_SIZE bytes.  */
+SCM
+scm_from_sockaddr (const struct sockaddr *address, unsigned addr_size)
+{
+  return (_scm_from_sockaddr (address, addr_size, "scm_from_sockaddr"));
+}
+
+/* Convert ADDRESS, an address object returned by either
+   `scm_from_sockaddr ()' or `scm_make_socket_address ()', into its C
+   representation.  On success, a non-NULL pointer is returned and
+   ADDRESS_SIZE is updated to the actual size (in bytes) of the returned
+   address.  The result must eventually be freed using `free ()'.  */
+struct sockaddr *
+scm_to_sockaddr (SCM address, size_t *address_size)
+#define FUNC_NAME "scm_to_sockaddr"
+{
+  short int family;
+  struct sockaddr *c_address = NULL;
+
+  SCM_VALIDATE_VECTOR (1, address);
+
+  *address_size = 0;
+  family = scm_to_short (SCM_SIMPLE_VECTOR_REF (address, 0));
+
+  switch (family)
+    {
+    case AF_INET:
+      {
+       if (SCM_SIMPLE_VECTOR_LENGTH (address) != 3)
+         scm_misc_error (FUNC_NAME,
+                         "invalid inet address representation: ~A",
+                         scm_list_1 (address));
+       else
+         {
+           struct sockaddr_in c_inet;
+
+           c_inet.sin_addr.s_addr =
+             htonl (scm_to_ulong (SCM_SIMPLE_VECTOR_REF (address, 1)));
+           c_inet.sin_port =
+             htons (scm_to_ushort (SCM_SIMPLE_VECTOR_REF (address, 2)));
+           c_inet.sin_family = AF_INET;
+
+           *address_size = sizeof (c_inet);
+           c_address = scm_malloc (sizeof (c_inet));
+           memcpy (c_address, &c_inet, sizeof (c_inet));
+         }
+
+       break;
+      }
+
+#ifdef HAVE_IPV6
+    case AF_INET6:
+      {
+       if (SCM_SIMPLE_VECTOR_LENGTH (address) != 5)
+         scm_misc_error (FUNC_NAME, "invalid inet6 address representation: ~A",
+                         scm_list_1 (address));
+       else
+         {
+           struct sockaddr_in6 c_inet6;
+
+           scm_to_ipv6 (c_inet6.sin6_addr.s6_addr, address);
+           c_inet6.sin6_port =
+             htons (scm_to_ushort (SCM_SIMPLE_VECTOR_REF (address, 2)));
+           c_inet6.sin6_flowinfo =
+             scm_to_uint32 (SCM_SIMPLE_VECTOR_REF (address, 3));
+#ifdef HAVE_SIN6_SCOPE_ID
+           c_inet6.sin6_scope_id =
+             scm_to_ulong (SCM_SIMPLE_VECTOR_REF (address, 4));
+#endif
+
+           c_inet6.sin6_family = AF_INET6;
+
+           *address_size = sizeof (c_inet6);
+           c_address = scm_malloc (sizeof (c_inet6));
+           memcpy (c_address, &c_inet6, sizeof (c_inet6));
+         }
+
+       break;
+      }
+#endif
+
+#ifdef HAVE_UNIX_DOMAIN_SOCKETS
+    case AF_UNIX:
+      {
+       if (SCM_SIMPLE_VECTOR_LENGTH (address) != 2)
+         scm_misc_error (FUNC_NAME, "invalid unix address representation: ~A",
+                         scm_list_1 (address));
+       else
+         {
+           SCM path;
+           size_t path_len = 0;
+
+           path = SCM_SIMPLE_VECTOR_REF (address, 1);
+           if ((!scm_is_string (path)) && (path != SCM_BOOL_F))
+             scm_misc_error (FUNC_NAME, "invalid unix address "
+                             "path: ~A", scm_list_1 (path));
+           else
+             {
+               struct sockaddr_un c_unix;
+
+               if (path == SCM_BOOL_F)
+                 path_len = 0;
+               else
+                 path_len = scm_c_string_length (path);
+
+#ifdef UNIX_PATH_MAX
+               if (path_len >= UNIX_PATH_MAX)
+#else
+/* We can hope that this limit will eventually vanish, at least on GNU.
+   However, currently, while glibc doesn't define `UNIX_PATH_MAX', it
+   documents it has being limited to 108 bytes.  */
+               if (path_len >= sizeof (c_unix.sun_path))
+#endif
+                 scm_misc_error (FUNC_NAME, "unix address path "
+                                 "too long: ~A", scm_list_1 (path));
+               else
+                 {
+                   if (path_len)
+                     {
+                       scm_to_locale_stringbuf (path, c_unix.sun_path,
+#ifdef UNIX_PATH_MAX
+                                                UNIX_PATH_MAX);
+#else
+                                                sizeof (c_unix.sun_path));
+#endif
+                       c_unix.sun_path[path_len] = '\0';
+
+                       /* Sanity check.  */
+                       if (strlen (c_unix.sun_path) != path_len)
+                         scm_misc_error (FUNC_NAME, "unix address path "
+                                         "contains nul characters: ~A",
+                                         scm_list_1 (path));
+                     }
+                   else
+                     c_unix.sun_path[0] = '\0';
+
+                   c_unix.sun_family = AF_UNIX;
+
+                   *address_size = SUN_LEN (&c_unix);
+                   c_address = scm_malloc (sizeof (c_unix));
+                   memcpy (c_address, &c_unix, sizeof (c_unix));
+                 }
+             }
+         }
+
+       break;
+      }
+#endif
+
+    default:
+      scm_misc_error (FUNC_NAME, "unrecognised address family: ~A",
+                     scm_list_1 (scm_from_ushort (family)));
+    }
+
+  return c_address;
+}
+#undef FUNC_NAME
+
+
+/* Return a newly-allocated `sockaddr' structure that reflects ADDRESS, being
+   an address of family FAMILY, with the family-specific parameters ARGS (see
+   the description of `connect' for details).  The returned structure may be
+   freed using `free ()'.  */
+struct sockaddr *
+scm_c_make_socket_address (SCM family, SCM address, SCM args,
+                          size_t *address_size)
+{
+  size_t size;
+  struct sockaddr *soka;
+
+  soka = scm_fill_sockaddr (scm_to_ushort (family), address, &args, 1,
+                           "scm_c_make_socket_address", &size);
+
+  return soka;
+}
+
+SCM_DEFINE (scm_make_socket_address, "make-socket-address", 2, 0, 1,
+           (SCM family, SCM address, SCM args),
+           "Return a Scheme address object that reflects @var{address}, "
+           "being an address of family @var{family}, with the "
+           "family-specific parameters @var{args} (see the description of "
+           "@code{connect} for details).")
+#define FUNC_NAME s_scm_make_socket_address
+{
+  struct sockaddr *c_address;
+  size_t c_address_size;
+
+  c_address = scm_c_make_socket_address (family, address, args,
+                                        &c_address_size);
+  if (!c_address)
+    return SCM_BOOL_F;
+
+  return (scm_from_sockaddr (c_address, c_address_size));
+}
+#undef FUNC_NAME
+
+
 /* calculate the size of a buffer large enough to hold any supported
    sockaddr type.  if the buffer isn't large enough, certain system
    calls will return a truncated address.  */
@@ -1009,7 +1228,7 @@
   if (newfd == -1)
     SCM_SYSERROR;
   newsock = SCM_SOCK_FD_TO_PORT (newfd);
-  address = scm_addr_vector (addr, addr_size, FUNC_NAME);
+  address = _scm_from_sockaddr (addr, addr_size, FUNC_NAME);
   return scm_cons (newsock, address);
 }
 #undef FUNC_NAME
@@ -1031,7 +1250,7 @@
   fd = SCM_FPORT_FDES (sock);
   if (getsockname (fd, addr, &addr_size) == -1)
     SCM_SYSERROR;
-  return scm_addr_vector (addr, addr_size, FUNC_NAME);
+  return _scm_from_sockaddr (addr, addr_size, FUNC_NAME);
 }
 #undef FUNC_NAME
 
@@ -1053,7 +1272,7 @@
   fd = SCM_FPORT_FDES (sock);
   if (getpeername (fd, addr, &addr_size) == -1)
     SCM_SYSERROR;
-  return scm_addr_vector (addr, addr_size, FUNC_NAME);
+  return _scm_from_sockaddr (addr, addr_size, FUNC_NAME);
 }
 #undef FUNC_NAME
 
@@ -1207,7 +1426,7 @@
   if (rv == -1)
     SCM_SYSERROR;
   if (addr->sa_family != AF_UNSPEC)
-    address = scm_addr_vector (addr, addr_size, FUNC_NAME);
+    address = _scm_from_sockaddr (addr, addr_size, FUNC_NAME);
   else
     address = SCM_BOOL_F;
 
@@ -1216,13 +1435,14 @@
 }
 #undef FUNC_NAME
 
-SCM_DEFINE (scm_sendto, "sendto", 4, 0, 1,
-            (SCM sock, SCM message, SCM fam, SCM address, SCM args_and_flags),
+SCM_DEFINE (scm_sendto, "sendto", 3, 1, 1,
+            (SCM sock, SCM message, SCM fam_or_sockaddr, SCM address, SCM 
args_and_flags),
            "Transmit the string @var{message} on the socket port\n"
            "@var{sock}.  The\n"
            "destination address is specified using the @var{fam},\n"
            "@var{address} and\n"
-           "@var{args_and_flags} arguments, in a similar way to the\n"
+           "@var{args_and_flags} arguments, or just a socket address object "
+           "returned by @code{make-socket-address}, in a similar way to the\n"
            "@code{connect} procedure.  @var{args_and_flags} contains\n"
            "the usual connection arguments optionally followed by\n"
            "a flags argument, which is a value or\n"
@@ -1241,14 +1461,26 @@
   int fd;
   int flg;
   struct sockaddr *soka;
-  int size;
+  size_t size;
 
   sock = SCM_COERCE_OUTPORT (sock);
   SCM_VALIDATE_FPORT (1, sock);
   SCM_VALIDATE_STRING (2, message);
   fd = SCM_FPORT_FDES (sock);
-  soka = scm_fill_sockaddr (scm_to_int (fam), address, &args_and_flags, 4,
-                           FUNC_NAME, &size);
+
+  if (!scm_is_number (fam_or_sockaddr))
+    {
+      /* FAM_OR_SOCKADDR must actually be a `socket address' object.  This
+        means that the following arguments, i.e. ADDRESS and those listed in
+        ARGS_AND_FLAGS, are the `MSG_' flags.  */
+      soka = scm_to_sockaddr (fam_or_sockaddr, &size);
+      if (address != SCM_UNDEFINED)
+       args_and_flags = scm_cons (address, args_and_flags);
+    }
+  else
+    soka = scm_fill_sockaddr (scm_to_int (fam_or_sockaddr), address,
+                             &args_and_flags, 3, FUNC_NAME, &size);
+
   if (scm_is_null (args_and_flags))
     flg = 0;
   else


--- orig/libguile/socket.h
+++ mod/libguile/socket.h
@@ -54,6 +54,16 @@
 SCM_API SCM scm_sendto (SCM sockfd, SCM message, SCM fam, SCM address, SCM 
args_and_flags);
 SCM_API void scm_init_socket (void);
 
+/* Wrapping/unwrapping address objects.  */
+struct sockaddr;
+SCM_API SCM scm_from_sockaddr (const struct sockaddr *address,
+                              unsigned addr_size);
+SCM_API struct sockaddr *scm_to_sockaddr (SCM address, size_t *adress_size);
+SCM_API struct sockaddr *scm_c_make_socket_address (SCM family, SCM address,
+                                                   SCM args,
+                                                   size_t *address_size);
+SCM_API SCM scm_make_socket_address (SCM family, SCM address, SCM args);
+
 #endif  /* SCM_SOCKET_H */
 
 /*

--- orig/test-suite/tests/socket.test
+++ mod/test-suite/tests/socket.test
@@ -6,12 +6,12 @@
 ;;;; modify it under the terms of the GNU Lesser General Public
 ;;;; License as published by the Free Software Foundation; either
 ;;;; version 2.1 of the License, or (at your option) any later version.
-;;;; 
+;;;;
 ;;;; This library is distributed in the hope that it will be useful,
 ;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
 ;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 ;;;; Lesser General Public License for more details.
-;;;; 
+;;;;
 ;;;; You should have received a copy of the GNU Lesser General Public
 ;;;; License along with this library; if not, write to the Free Software
 ;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 
USA
@@ -19,6 +19,7 @@
 (define-module (test-suite test-numbers)
   #:use-module (test-suite lib))
 
+
 ;;;
 ;;; inet-ntop
 ;;;
@@ -78,3 +79,177 @@
          (eqv? #xF0
                (inet-pton AF_INET6
                           "0000:0000:0000:0000:0000:0000:0000:00F0"))))))
+
+
+;;;
+;;; make-socket-address
+;;;
+
+(with-test-prefix "make-socket-address"
+  (if (defined? 'AF_INET)
+      (pass-if "AF_INET"
+       (let ((sa (make-socket-address AF_INET 123456 80)))
+         (and (= (sockaddr:fam  sa) AF_INET)
+              (= (sockaddr:addr sa) 123456)
+              (= (sockaddr:port sa) 80)))))
+
+  (if (defined? 'AF_INET6)
+      (pass-if "AF_INET6"
+       ;; Since the platform doesn't necessarily support `scopeid', we won't
+        ;; test it.
+       (let ((sa* (make-socket-address AF_INET6 123456 80 1))
+             (sa+ (make-socket-address AF_INET6 123456 80)))
+         (and (= (sockaddr:fam  sa*) (sockaddr:fam  sa+) AF_INET6)
+              (= (sockaddr:addr sa*) (sockaddr:addr sa+) 123456)
+              (= (sockaddr:port sa*) (sockaddr:port sa+) 80)
+              (= (sockaddr:flowinfo sa*) 1)))))
+
+  (if (defined? 'AF_UNIX)
+      (pass-if "AF_UNIX"
+       (let ((sa (make-socket-address AF_UNIX "/tmp/unix-socket")))
+         (and (= (sockaddr:fam sa) AF_UNIX)
+              (string=? (sockaddr:path sa) "/tmp/unix-socket"))))))
+
+
+
+;;;
+;;; AF_UNIX sockets and `make-socket-address'
+;;;
+
+(if (defined? 'AF_UNIX)
+    (with-test-prefix "AF_UNIX/SOCK_DGRAM"
+
+      ;; testing `bind' and `sendto' and datagram sockets
+
+      (let ((server-socket (socket AF_UNIX SOCK_DGRAM 0))
+           (server-bound? #f)
+           (path (tmpnam)))
+
+       (pass-if "bind"
+         (catch 'system-error
+           (lambda ()
+             (bind server-socket AF_UNIX path)
+             (set! server-bound? #t)
+             #t)
+           (lambda args
+             (let ((errno (system-error-errno args)))
+               (cond ((= errno EADDRINUSE) (throw 'unresolved))
+                     (else (apply throw args)))))))
+
+       (pass-if "bind/sockaddr"
+         (let* ((sock (socket AF_UNIX SOCK_STREAM 0))
+                (path (tmpnam))
+                (sockaddr (make-socket-address AF_UNIX path)))
+           (catch 'system-error
+             (lambda ()
+               (bind sock sockaddr)
+               (false-if-exception (delete-file path))
+               #t)
+             (lambda args
+               (let ((errno (system-error-errno args)))
+                 (cond ((= errno EADDRINUSE) (throw 'unresolved))
+                       (else (apply throw args))))))))
+
+       (pass-if "sendto"
+         (if (not server-bound?)
+             (throw 'unresolved)
+             (let ((client (socket AF_UNIX SOCK_DGRAM 0)))
+               (> (sendto client "hello" AF_UNIX path) 0))))
+
+       (pass-if "sendto/sockaddr"
+         (if (not server-bound?)
+             (throw 'unresolved)
+             (let ((client (socket AF_UNIX SOCK_DGRAM 0))
+                   (sockaddr (make-socket-address AF_UNIX path)))
+               (> (sendto client "hello" sockaddr) 0))))
+
+       (false-if-exception (delete-file path)))))
+
+
+(if (defined? 'AF_UNIX)
+    (with-test-prefix "AF_UNIX/SOCK_STREAM"
+
+      ;; testing `bind', `listen' and `connect' on stream-oriented sockets
+
+      (let ((server-socket (socket AF_UNIX SOCK_STREAM 0))
+           (server-bound? #f)
+           (server-listening? #f)
+           (server-pid #f)
+           (path (tmpnam)))
+
+       (pass-if "bind"
+         (catch 'system-error
+           (lambda ()
+             (bind server-socket AF_UNIX path)
+             (set! server-bound? #t)
+             #t)
+           (lambda args
+             (let ((errno (system-error-errno args)))
+               (cond ((= errno EADDRINUSE) (throw 'unresolved))
+                     (else (apply throw args)))))))
+
+       (pass-if "bind/sockaddr"
+         (let* ((sock (socket AF_UNIX SOCK_STREAM 0))
+                (path (tmpnam))
+                (sockaddr (make-socket-address AF_UNIX path)))
+           (catch 'system-error
+             (lambda ()
+               (bind sock sockaddr)
+               (false-if-exception (delete-file path))
+               #t)
+             (lambda args
+               (let ((errno (system-error-errno args)))
+                 (cond ((= errno EADDRINUSE) (throw 'unresolved))
+                       (else (apply throw args))))))))
+
+       (pass-if "listen"
+         (if (not server-bound?)
+             (throw 'unresolved)
+             (begin
+               (listen server-socket 123)
+               (set! server-listening? #t)
+               #t)))
+
+       (if server-listening?
+           (let ((pid (primitive-fork)))
+             ;; Spawn a server process.
+             (case pid
+               ((-1) (throw 'unresolved))
+               ((0)   ;; the kid:  serve two connections and exit
+                (let serve ((conn
+                             (false-if-exception (accept server-socket)))
+                            (count 1))
+                  (if (not conn)
+                      (exit 1)
+                      (if (> count 0)
+                          (serve (false-if-exception (accept server-socket))
+                                 (- count 1)))))
+                (exit 0))
+               (else  ;; the parent
+                (set! server-pid pid)
+                #t))))
+
+       (pass-if "connect"
+         (if (not server-pid)
+             (throw 'unresolved)
+             (let ((s (socket AF_UNIX SOCK_STREAM 0)))
+               (connect s AF_UNIX path)
+               #t)))
+
+       (pass-if "connect/sockaddr"
+         (if (not server-pid)
+             (throw 'unresolved)
+             (let ((s (socket AF_UNIX SOCK_STREAM 0)))
+               (connect s (make-socket-address AF_UNIX path))
+               #t)))
+
+       (pass-if "accept"
+         (if (not server-pid)
+             (throw 'unresolved)
+             (let ((status (cdr (waitpid server-pid))))
+               (eq? 0 (status:exit-val status)))))
+
+       (false-if-exception (delete-file path))
+
+       #t)))
+