Subject: iproute2: make arpd daemon write pid file on fork

From: Alex Dubov <[email-masked]>
Date: Fri, 12 Aug 2011 16:23:24 +1000

Current version of arpd included with iproute2-2.6.37 will fork 
unconditionally on start-up (using daemon() library call). This causes 
problems with distro start-up scripts, as PID of the started daemon can not be 
reliably obtained, hampering orderly daemon shutdown process.

The included patch makes arpd write it's own pid file after fork, in a common 
LSB fashion, so as to better inter-operate with start up scripts. Removal of 
stale pid files is handled elsewhere.

--- misc/arpd.c.orig	2011-01-08 04:54:30.000000000 +1100
+++ misc/arpd.c	2011-08-12 16:04:51.098754397 +1000
@@ -41,6 +41,7 @@
 
 DB	*dbase;
 char	*dbname = "/var/lib/arpd/arpd.db";
+char	*pidfname = "/var/run/arpd.pid";
 
 int	ifnum;
 int	*ifvec;
@@ -780,6 +781,17 @@
 		goto do_abort;
 	}
 
+	do {
+		FILE *fp = fopen(pidfname, "w");
+		if (fp) {
+			fprintf(fp, "%ld\n", (long)getpid());
+			fclose(fp);
+		} else {
+			perror("arpd: pid fopen");
+			goto do_abort;
+		}
+	} while (0);
+
 	openlog("arpd", LOG_PID | LOG_CONS, LOG_DAEMON);
 	catch_signal(SIGINT, sig_exit);
 	catch_signal(SIGTERM, sig_exit);