diff -ur postgresql-7.1.2/src/backend/libpq/auth.c postgresql-7.1.2-ident-local/src/backend/libpq/auth.c
--- postgresql-7.1.2/src/backend/libpq/auth.c	Thu Mar 22 04:59:30 2001
+++ postgresql-7.1.2-ident-local/src/backend/libpq/auth.c	Tue Jul 31 11:07:07 2001
@@ -527,8 +527,7 @@
 				break;
 
 			case uaIdent:
-				if (authident(&port->raddr.in, &port->laddr.in,
-							  port->user, port->auth_arg) == STATUS_OK)
+				if (authident(port) == STATUS_OK)
 				{
 					areq = AUTH_REQ_OK;
 					auth_handler = handle_done_auth;
@@ -780,8 +779,7 @@
 			break;
 
 		case uaIdent:
-			status = authident(&port->raddr.in, &port->laddr.in,
-							   port->user, port->auth_arg);
+			status = authident(port);
 			break;
 
 		case uaPassword:
diff -ur postgresql-7.1.2/src/backend/libpq/hba.c postgresql-7.1.2-ident-local/src/backend/libpq/hba.c
--- postgresql-7.1.2/src/backend/libpq/hba.c	Sat Feb 10 03:31:26 2001
+++ postgresql-7.1.2-ident-local/src/backend/libpq/hba.c	Tue Jul 31 11:10:27 2001
@@ -195,8 +195,10 @@
 		 * For now, disallow methods that need AF_INET sockets to work.
 		 */
 
-		if (!*error_p &&
-			(port->auth_method == uaIdent ||
+		if (!*error_p && (
+#ifndef HAVE_SO_PEERCRED
+			 port->auth_method == uaIdent ||
+#endif
 			 port->auth_method == uaKrb4 ||
 			 port->auth_method == uaKrb5))
 			*error_p = true;
@@ -834,34 +836,53 @@
 
 
 int
-authident(struct sockaddr_in * raddr, struct sockaddr_in * laddr,
-		  const char *postgres_username,
-		  const char *auth_arg)
+authident(struct Port *port)
 {
 /*---------------------------------------------------------------------------
-  Talk to the ident server on the remote host and find out who owns the
-  connection described by "port".  Then look in the usermap file under
-  the usermap *auth_arg and see if that user is equivalent to
-  Postgres user *user.
+  Talk to the ident server on the remote host or get peer credentials from
+  kernel and find out who owns the connection described by "port".  Then
+  look in the usermap file under the usermap *auth_arg and see if that user
+  is equivalent to Postgres user *user.
 
   Return STATUS_OK if yes.
 ---------------------------------------------------------------------------*/
 	bool		checks_out;
 	bool		ident_failed;
-
 	/* We were unable to get ident to give us a username */
+	
+#ifdef HAVE_SO_PEERCRED
+	struct ucred	creds;		/* numeric peer credentials */
+	struct passwd	*pw;		/* map uid to name */
+	int		rc, size;
+#endif
+	
 	char		ident_username[IDENT_USERNAME_MAX + 1];
-
 	/* The username returned by ident */
-
-	ident(raddr->sin_addr, laddr->sin_addr,
-		  raddr->sin_port, laddr->sin_port,
-		  &ident_failed, ident_username);
-
-	if (ident_failed)
-		return STATUS_ERROR;
-
-	verify_against_usermap(postgres_username, ident_username, auth_arg,
+	
+	switch (port->laddr.sa.sa_family) {
+		case AF_INET:
+			ident(port->raddr.in.sin_addr, port->laddr.in.sin_addr,
+				port->raddr.in.sin_port, port->laddr.in.sin_port,
+				&ident_failed, ident_username);
+			if (ident_failed) return STATUS_ERROR;
+			break;
+#ifdef HAVE_SO_PEERCRED
+		case AF_UNIX:
+			size=sizeof(creds);
+			rc=getsockopt(port->sock, SOL_SOCKET, SO_PEERCRED,
+				&creds, &size);
+			if (rc || (size!=sizeof(creds))) return STATUS_ERROR;
+			
+			pw=getpwuid(creds.uid);
+			if (!pw) return STATUS_ERROR;
+			
+			strncpy(ident_username, pw->pw_name, IDENT_USERNAME_MAX);
+			break;
+#endif
+		default:
+			return STATUS_ERROR;
+	}
+	verify_against_usermap(port->user, ident_username, port->auth_arg,
 						   &checks_out);
 
 	return checks_out ? STATUS_OK : STATUS_ERROR;
diff -ur postgresql-7.1.2/src/include/libpq/hba.h postgresql-7.1.2-ident-local/src/include/libpq/hba.h
--- postgresql-7.1.2/src/include/libpq/hba.h	Thu Mar 22 05:00:47 2001
+++ postgresql-7.1.2-ident-local/src/include/libpq/hba.h	Tue Jul 31 10:10:30 2001
@@ -41,7 +41,6 @@
 typedef struct Port hbaPort;
 
 int			hba_getauthmethod(hbaPort *port);
-int authident(struct sockaddr_in * raddr, struct sockaddr_in * laddr,
-		  const char *postgres_username, const char *auth_arg);
+int authident(struct Port *port);
 
 #endif