[master]

Add a sleep call after trying to kill a previous client.  This
should make the "-r" option to the client work more consistently.
[ISC-Bugs: 18175]

RELNOTES

@@ -92,6 +92,11 @@ work on other platforms. Please report any problems and suggested fixes to
   objects.
   [ISC-Bugs #27452]
 
+- Added a sleep call after killing the old client to allow time
+  for the sockets to be cleaned.  This should allow the -r option
+  to work more consistently.
+  [ISC-Bugs #18175]
+
 			Changes since 4.2.4
 
 - Correct code to calculate timing values in client to compare

client/dhclient.c

@@ -404,8 +404,16 @@ main(int argc, char **argv) {
 			oldpid = (pid_t)temp;
 
 			if (e != 0 && e != EOF) {
-				if (oldpid)
-					kill(oldpid, SIGTERM);
+				if (oldpid && (kill(oldpid, SIGTERM) == 0)) {
+					/*
+					 * wait for the old process to
+					 * cleanly terminate.
+					 * Note kill() with sig=0 could
+					 * detect termination but only
+					 * the parent can be signaled...
+					 */
+					sleep(1);
+				}
 			}
 			fclose(pidfd);
 		}