Code review for connection timeout patch. Avoid unportable assumption

that tv_sec is signed; return a useful error message on timeout failure;
honor PGCONNECT_TIMEOUT environment variable in PQsetdbLogin; make code
obey documentation statement that timeout=0 means no timeout.

Author: tglsfdc

src/interfaces/libpq/fe-connect.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-connect.c,v 1.212 2002/10/16 04:38:00 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-connect.c,v 1.213 2002/10/24 23:35:55 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -507,6 +507,9 @@ PQsetdbLogin(const char *pghost, const char *pgport, const char *pgoptions,
 	else
 		conn->pgpass = strdup(DefaultPassword);
 
+	if ((tmp = getenv("PGCONNECT_TIMEOUT")) != NULL)
+		conn->connect_timeout = strdup(tmp);
+
 #ifdef USE_SSL
 	if ((tmp = getenv("PGREQUIRESSL")) != NULL)
 		conn->require_ssl = (tmp[0] == '1') ? true : false;
@@ -1051,32 +1054,29 @@ static int
 connectDBComplete(PGconn *conn)
 {
 	PostgresPollingStatusType flag = PGRES_POLLING_WRITING;
-
-	time_t			finish_time = -1;
+	time_t			finish_time = ((time_t) -1);
 
 	if (conn == NULL || conn->status == CONNECTION_BAD)
 		return 0;
 
 	/*
-	 * Prepare to time calculations, if connect_timeout isn't zero.
+	 * Set up a time limit, if connect_timeout isn't zero.
 	 */
 	if (conn->connect_timeout != NULL)
 	{
 		int timeout = atoi(conn->connect_timeout);
 
-		if (timeout == 0)
+		if (timeout > 0)
 		{
-			conn->status = CONNECTION_BAD;
-			return 0;
+			/* Rounding could cause connection to fail; need at least 2 secs */
+			if (timeout < 2)
+				timeout = 2;
+			/* calculate the finish time based on start + timeout */
+			finish_time = time(NULL) + timeout;
 		}
-		/* Rounding could cause connection to fail;we need at least 2 secs */
-		if (timeout == 1)
-			timeout++;
-		/* calculate the finish time based on start + timeout */
-		finish_time = time(NULL) + timeout;
 	}
 
-	while (finish_time == -1 || time(NULL) < finish_time)
+	for (;;)
 	{
 		/*
 		 * Wait, if necessary.	Note that the initial state (just after
@@ -1118,8 +1118,6 @@ connectDBComplete(PGconn *conn)
 		 */
 		flag = PQconnectPoll(conn);
 	}
-	conn->status = CONNECTION_BAD;
-	return 0;
 }
 
 /* ----------------

src/interfaces/libpq/fe-misc.c

@@ -25,7 +25,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-misc.c,v 1.84 2002/10/16 02:55:30 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-misc.c,v 1.85 2002/10/24 23:35:55 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -779,18 +779,27 @@ pqFlush(PGconn *conn)
 int
 pqWait(int forRead, int forWrite, PGconn *conn)
 {
-	return pqWaitTimed(forRead, forWrite, conn, -1);
+	return pqWaitTimed(forRead, forWrite, conn, (time_t) -1);
 }
 
+/*
+ * pqWaitTimed: wait, but not past finish_time.
+ *
+ * If finish_time is exceeded then we return failure (EOF).  This is different
+ * from the response for a kernel exception (return 0) because we don't want
+ * the caller to try to read/write in that case.
+ *
+ * finish_time = ((time_t) -1) disables the wait limit.
+ */
 int
 pqWaitTimed(int forRead, int forWrite, PGconn *conn, time_t finish_time)
 {
 	fd_set		input_mask;
 	fd_set		output_mask;
 	fd_set		except_mask;
-
 	struct timeval tmp_timeout;
 	struct timeval *ptmp_timeout = NULL;
+	int			selresult;
 
 	if (conn->sock < 0)
 	{
@@ -820,24 +829,26 @@ pqWaitTimed(int forRead, int forWrite, PGconn *conn, time_t finish_time)
 			FD_SET(conn->sock, &output_mask);
 		FD_SET(conn->sock, &except_mask);
 
-		if (finish_time != -1)
+		if (finish_time != ((time_t) -1))
 		{
 			/*
-			 * 	select() may modify timeout argument on some platforms so
-			 *	use copy.
-			 *	XXX Do we really want to do that?  If select() returns
-			 *	the number of seconds remaining, we are resetting
-			 *	the timeout to its original value.  This will yeild
-			 *	incorrect timings when select() is interrupted.
-			 *	bjm 2002-10-14
+			 * Set up delay.  Assume caller incremented finish_time
+			 * so that we can error out as soon as time() passes it.
+			 * Note we will recalculate delay each time through the loop.
 			 */
-			if ((tmp_timeout.tv_sec = finish_time - time(NULL)) < 0)
-				tmp_timeout.tv_sec = 0;  /* possible? */
+			time_t	now = time(NULL);
+
+			if (finish_time > now)
+				tmp_timeout.tv_sec = finish_time - now;
+			else
+				tmp_timeout.tv_sec = 0;
 			tmp_timeout.tv_usec = 0;
 			ptmp_timeout = &tmp_timeout;
 		}
-		if (select(conn->sock + 1, &input_mask, &output_mask,
-				   &except_mask, ptmp_timeout) < 0)
+
+		selresult = select(conn->sock + 1, &input_mask, &output_mask,
+						   &except_mask, ptmp_timeout);
+		if (selresult < 0)
 		{
 			if (SOCK_ERRNO == EINTR)
 				goto retry5;
@@ -846,6 +857,12 @@ pqWaitTimed(int forRead, int forWrite, PGconn *conn, time_t finish_time)
 							  SOCK_STRERROR(SOCK_ERRNO));
 			return EOF;
 		}
+		if (selresult == 0)
+		{
+			printfPQExpBuffer(&conn->errorMessage,
+							  libpq_gettext("timeout expired\n"));
+			return EOF;
+		}
 	}
 
 	return 0;