+/* `sockaddr_un.sun_path' typical size usually ranges between 92 and 108 */
+#define INITIAL_SOCKNAME_SLACK 108
+
+/* Return a dynamically allocated socket address structure according
+ to the value returned by either getpeername() or getsockname()
+ (according to POSIX, applications should not assume a particular
+ length for `sockaddr_un.sun_path') */
+static struct sockaddr *get_peer_sock_name(int (*socket_func)(int,
+ struct sockaddr *,
+ socklen_t *),
+ int fd)
+{
+ socklen_t socknamelen = sizeof(struct sockaddr) + INITIAL_SOCKNAME_SLACK;
+ socklen_t actual_socknamelen = socknamelen;
+ struct sockaddr *sockname = malloc(socknamelen);
+
+ if (sockname == NULL)
+ return NULL;
+
+ /* Both getpeername() and getsockname() truncates sockname if
+ there is not enough space and set the required length in
+ actual_socknamelen */
+ if (socket_func(fd, sockname, &actual_socknamelen) == -1)
+ goto sock_or_realloc_error;
+
+ if (actual_socknamelen > socknamelen)
+ {
+ struct sockaddr *new_sockname = NULL;
+ socknamelen = actual_socknamelen;
+
+ if ((new_sockname = realloc(sockname, actual_socknamelen)) == NULL)
+ goto sock_or_realloc_error;
+
+ sockname = new_sockname;
+
+ if (socket_func(fd, sockname, &actual_socknamelen) == -1 ||
+ actual_socknamelen > socknamelen)
+ goto sock_or_realloc_error;
+ }
+
+ return sockname;
+
+ sock_or_realloc_error:
+ free(sockname);
+ return NULL;
+}
+