arpd: allow configuring polling interval

A new option -p is added to the arpd command that accepts
a time indicating the number of seconds
to wait between kernel arp table polling attempts.
The minimum value is .1 (100ms).

If not specified, polling defaults to 30 seconds.

Patch by Erik Hugne <erik.hugne@ericsson.com> with
modifications

man/man8/arpd.8

@@ -4,7 +4,7 @@
 arpd \- userspace arp daemon.
 
 .SH SYNOPSIS
-Usage: arpd [ -lkh? ] [ -a N ] [ -b dbase ] [ -B number ] [ -f file ] [ -n time ] [ -R rate ] [ interfaces ]
+Usage: arpd [ -lkh? ] [ -a N ] [ -b dbase ] [ -B number ] [ -f file ] [-p interval ] [ -n time ] [ -R rate ] [ interfaces ]
 
 .SH DESCRIPTION
 The
@@ -34,6 +34,9 @@ Suppress sending broadcast queries by kernel. It takes sense together with optio
 -n <TIME>
 Timeout of negative cache. When resolution fails arpd suppresses further attempts to resolve for this period. It makes sense only together with option -k This timeout should not be too much longer than boot time of a typical host not supporting gratuitous ARP. Default value is 60 seconds.
 .TP
+-p <TIME>
+Time to wait in seconds between polling attempts to the kernel ARP table. TIME may be a floating point number.  The default value is 30.
+.TP
 -R <RATE>
 Maximal steady rate of broadcasts sent by arpd in packets per second. Default value is 1.
 .TP

misc/arpd.c

@@ -90,11 +90,13 @@ int negative_timeout = 60;
 int no_kernel_broadcasts;
 int broadcast_rate = 1000;
 int broadcast_burst = 3000;
+int poll_timeout = 30000;
 
 void usage(void)
 {
 	fprintf(stderr,
-"Usage: arpd [ -lkh? ] [ -a N ] [ -b dbase ] [ -B number ] [ -f file ] [ -n time ] [ -R rate ] [ interfaces ]\n");
+		"Usage: arpd [ -lkh? ] [ -a N ] [ -b dbase ] [ -B number ]"
+		" [ -f file ] [ -n time ] [-p interval ] [ -R rate ] [ interfaces ]\n");
 	exit(1);
 }
 
@@ -591,7 +593,7 @@ int main(int argc, char **argv)
 	int do_list = 0;
 	char *do_load = NULL;
 
-	while ((opt = getopt(argc, argv, "h?b:lf:a:n:kR:B:")) != EOF) {
+	while ((opt = getopt(argc, argv, "h?b:lf:a:n:p:kR:B:")) != EOF) {
 		switch (opt) {
 	        case 'b':
 			dbname = optarg;
@@ -615,6 +617,12 @@ int main(int argc, char **argv)
 		case 'k':
 			no_kernel_broadcasts = 1;
 			break;
+		case 'p':
+			if ((poll_timeout = 1000 * strtod(optarg, NULL)) < 100) {
+				fprintf(stderr,"Invalid poll timeout\n");
+				exit(-1);
+			}
+			break;
 		case 'R':
 			if ((broadcast_rate = atoi(optarg)) <= 0 ||
 			    (broadcast_rate = 1000/broadcast_rate) <= 0) {
@@ -807,7 +815,7 @@ int main(int argc, char **argv)
 		}
 		if (do_stats)
 			send_stats();
-		if (poll(pset, 2, 30000) > 0) {
+		if (poll(pset, 2, poll_timeout) > 0) {
 			in_poll = 0;
 			if (pset[0].revents&EVENTS)
 				get_arp_pkt();