Index: src/common.c
===================================================================
--- src/common.c
+++ src/common.c	2009-07-26 04:00:42.000000000 +0200
@@ -26,6 +26,7 @@
 #include <string.h>
 #include <ctype.h>
 #include <fcntl.h>
+#include <errno.h>
 
 #ifdef WINDOWS32
 #include <winsock2.h>
@@ -165,6 +166,26 @@
 }
 
 void
+do_pidfile(char *pidfile)
+{
+#ifndef WINDOWS32
+    FILE *file;
+
+    if ((file = fopen(pidfile, "w")) == NULL) {
+            fprintf(stderr, "Unable to open \"%s\" for writing: %s", pidfile, strerror(errno));
+		    err(1, "do_pidfile");
+    } else {
+        fprintf(file, "%d\n", (int)getpid());
+        fclose(file);
+    }
+
+
+#else
+	fprintf(stderr, "Windows version does not support writing the process id to a file\n");
+#endif
+}
+
+void
 do_detach()
 {
 #ifndef WINDOWS32
Index: src/common.h
===================================================================
--- src/common.h
+++ src/common.h	2009-07-26 03:47:24.000000000 +0200
@@ -83,6 +83,7 @@
 
 void do_chroot(char *);
 void do_detach();
+void do_pidfile(char *);
 
 void read_password(char*, size_t);
 
Index: src/iodine.c
===================================================================
--- src/iodine.c
+++ src/iodine.c	2009-07-26 03:47:02.000000000 +0200
@@ -958,7 +958,7 @@
 	extern char *__progname;
 
 	fprintf(stderr, "Usage: %s [-v] [-h] [-f] [-u user] [-t chrootdir] [-d device] "
-			"[-P password] [-m maxfragsize] [nameserver] topdomain\n", __progname);
+			"[-P password] [-m maxfragsize] [-p pidfile] [nameserver] topdomain\n", __progname);
 	exit(2);
 }
 
@@ -968,7 +968,7 @@
 
 	fprintf(stderr, "iodine IP over DNS tunneling client\n");
 	fprintf(stderr, "Usage: %s [-v] [-h] [-f] [-u user] [-t chrootdir] [-d device] "
-			"[-P password] [-m maxfragsize] [nameserver] topdomain\n", __progname);
+			"[-P password] [-m maxfragsize] [-F pidfile] [nameserver] topdomain\n", __progname);
 	fprintf(stderr, "  -v to print version info and exit\n");
 	fprintf(stderr, "  -h to print this help and exit\n");
 	fprintf(stderr, "  -f to keep running in foreground\n");
@@ -977,6 +977,7 @@
 	fprintf(stderr, "  -d device to set tunnel device name\n");
 	fprintf(stderr, "  -P password used for authentication (max 32 chars will be used)\n");
 	fprintf(stderr, "  -m maxfragsize, to limit size of downstream packets\n");
+	fprintf(stderr, "  -F pidfile to write pid to a file\n");
 	fprintf(stderr, "nameserver is the IP number of the relaying nameserver, if absent /etc/resolv.conf is used\n");
 	fprintf(stderr, "topdomain is the FQDN that is delegated to the tunnel endpoint.\n");
 
@@ -1007,6 +1008,7 @@
 	int dns_fd;
 	int max_downstream_frag_size;
 	int autodetect_frag_size;
+	char *pidfile;
 
 	memset(password, 0, 33);
 	username = NULL;
@@ -1014,6 +1016,7 @@
 	newroot = NULL;
 	device = NULL;
 	chunkid = 0;
+    pidfile = NULL;
 
 	outpkt.seqno = 0;
 	inpkt.len = 0;
@@ -1036,7 +1039,7 @@
 		__progname++;
 #endif
 
-	while ((choice = getopt(argc, argv, "vfhu:t:d:P:m:")) != -1) {
+	while ((choice = getopt(argc, argv, "vfhu:t:d:P:m:F:")) != -1) {
 		switch(choice) {
 		case 'v':
 			version();
@@ -1069,6 +1072,9 @@
 			autodetect_frag_size = 0;
 			max_downstream_frag_size = atoi(optarg);
 			break;
+		case 'F':
+			pidfile = optarg;
+			break;    
 		default:
 			usage();
 			/* NOTREACHED */
@@ -1148,6 +1154,9 @@
 	if (foreground == 0) 
 		do_detach();
 
+	if (pidfile != NULL)
+		do_pidfile(pidfile);
+
 	if (newroot != NULL)
 		do_chroot(newroot);
 	
Index: src/iodined.c
===================================================================
--- src/iodined.c
+++ src/iodined.c	2009-07-26 14:24:32.000000000 +0200
@@ -892,7 +892,7 @@
 	fprintf(stderr, "Usage: %s [-v] [-h] [-c] [-s] [-f] [-D] [-u user] "
 		"[-t chrootdir] [-d device] [-m mtu] "
 		"[-l ip address to listen on] [-p port] [-n external ip] [-b dnsport] [-P password]"
-		" tunnel_ip[/netmask] topdomain\n", __progname);
+		"[-F pidfile] tunnel_ip[/netmask] topdomain\n", __progname);
 	exit(2);
 }
 
@@ -904,7 +904,7 @@
 	fprintf(stderr, "Usage: %s [-v] [-h] [-c] [-s] [-f] [-D] [-u user] "
 		"[-t chrootdir] [-d device] [-m mtu] "
 		"[-l ip address to listen on] [-p port] [-n external ip] [-b dnsport] [-P password]"
-		" tunnel_ip[/netmask] topdomain\n", __progname);
+		"[-F pidfile] tunnel_ip[/netmask] topdomain\n", __progname);
 	fprintf(stderr, "  -v to print version info and exit\n");
 	fprintf(stderr, "  -h to print this help and exit\n");
 	fprintf(stderr, "  -c to disable check of client IP/port on each request\n");
@@ -922,6 +922,7 @@
 	fprintf(stderr, "  -n ip to respond with to NS queries\n");
 	fprintf(stderr, "  -b port to forward normal DNS queries to (on localhost)\n");
 	fprintf(stderr, "  -P password used for authentication (max 32 chars will be used)\n");
+	fprintf(stderr, "  -F pidfile to write pid to a file\n");
 	fprintf(stderr, "tunnel_ip is the IP number of the local tunnel interface.\n");
 	fprintf(stderr, "   /netmask sets the size of the tunnel network.\n");
 	fprintf(stderr, "topdomain is the FQDN that is delegated to this server.\n");
@@ -960,6 +961,7 @@
 	int mtu;
 	int skipipconfig;
 	char *netsize;
+	char *pidfile;
 
 	username = NULL;
 	newroot = NULL;
@@ -975,6 +977,7 @@
 	skipipconfig = 0;
 	debug = 0;
 	netmask = 27;
+	pidfile = NULL;
 
 	b32 = get_base32_encoder();
 	
@@ -994,7 +997,7 @@
 	srand(time(NULL));
 	fw_query_init();
 	
-	while ((choice = getopt(argc, argv, "vcsfhDu:t:d:m:l:p:n:b:P:")) != -1) {
+	while ((choice = getopt(argc, argv, "vcsfhDu:t:d:m:l:p:n:b:P:F:")) != -1) {
 		switch(choice) {
 		case 'v':
 			version();
@@ -1039,6 +1042,9 @@
 			bind_enable = 1;
 			bind_port = atoi(optarg);
 			break;
+		case 'F':
+			pidfile = optarg;
+			break;    
 		case 'P':
 			strncpy(password, optarg, sizeof(password));
 			password[sizeof(password)-1] = 0;
@@ -1165,7 +1171,10 @@
 
 	if (foreground == 0) 
 		do_detach();
-	
+
+	if (pidfile != NULL)
+		do_pidfile(pidfile);
+
 	if (newroot != NULL)
 		do_chroot(newroot);