Add code to write pidfile, and -i option to specify pid file.

Add -u option to specify the user. Do the uid flip here instead of in
the perl wrapper, but only if root of course. Otherwise runs as the
user that invoked the program-agent.
Add mandatory -e option to speicfy the pid/eid to use in event tuple
instead of the ipaddr, since in jails without their own IP address,
using the ipaddr is broken (all jails see all program events).
Add mandatory -a option to specify a list of object names, so that the
agent will get just the events it should. There is a corresponding new
tmcc command that specifies the list of program objects for the node
(or vnode).

event/program-agent/program-agent.c

 /*
  * EMULAB-COPYRIGHT
- * Copyright (c) 2000-2002 University of Utah and the Flux Group.
+ * Copyright (c) 2000-2003 University of Utah and the Flux Group.
  * All rights reserved.
  */
 
@@ -19,13 +19,16 @@
 #include <netinet/in.h>
 #include <arpa/inet.h>
 #include <signal.h>
+#include <pwd.h>
 #include <time.h>
 #include "tbdefs.h"
 #include "log.h"
 #include "event.h"
+#define MAXAGENTS	100
 
-static char 		*logfile;
 static char		debug;
+static char		*agentnames[MAXAGENTS];
+static int		numagents;
 
 struct proginfo {
 	char		name[TBDB_FLEN_EVOBJNAME];
@@ -46,25 +49,32 @@ void
 usage(char *progname)
 {
 	fprintf(stderr,
-		"Usage: %s [-s server] [-p port] [-l logfile]\n", progname);
+		"Usage: %s [-s server] [-p port] [-l logfile] "
+		"[-u login] [-i pidfile] -e pid/eid -a agent [-a agent ...]\n",
+		progname);
 	exit(-1);
 }
 
 int
 main(int argc, char **argv)
 {
+	FILE *fp;
 	event_handle_t handle;
 	address_tuple_t	tuple;
 	char *progname;
 	char *server = NULL;
 	char *port = NULL;
-	char *ipaddr = NULL;
-	char buf[BUFSIZ], ipbuf[BUFSIZ];
+	char *logfile = NULL;
+	char *user = NULL;
+	char *pidfile = NULL;
+	char *pideid = NULL;
+	char buf[BUFSIZ], agentlist[BUFSIZ];
 	int c;
 
 	progname = argv[0];
+	bzero(agentlist, sizeof(agentlist));
 	
-	while ((c = getopt(argc, argv, "s:p:l:d")) != -1) {
+	while ((c = getopt(argc, argv, "s:p:l:du:i:e:a:")) != -1) {
 		switch (c) {
 		case 's':
 			server = optarg;
@@ -78,6 +88,24 @@ main(int argc, char **argv)
 		case 'd':
 			debug++;
 			break;
+		case 'u':
+			user = optarg;
+			break;
+		case 'i':
+			pidfile = optarg;
+			break;
+		case 'e':
+			pideid = optarg;
+			break;
+		case 'a':
+			if (numagents >= MAXAGENTS)
+				fatal("Too many agents listed");
+			agentnames[numagents] = optarg;
+			numagents++;
+			if (!strlen(agentlist))
+				strcat(agentlist, ",");
+			strcpy(agentlist, optarg);
+			break;
 		default:
 			usage(progname);
 		}
@@ -85,8 +113,13 @@ main(int argc, char **argv)
 	argc -= optind;
 	argv += optind;
 
+	if (!pideid || !numagents)
+		usage(progname);
+	if (!getuid() && !user)
+		usage(progname);
+
 	if (debug) 
-		loginit(0, 0);
+		loginit(0, logfile);
 	else {
 		/* Become a daemon */
 		daemon(0, 0);
@@ -98,25 +131,42 @@ main(int argc, char **argv)
 	}
 
 	/*
-	 * Get our IP address. Thats how we name ourselves to the
-	 * Testbed Event System. 
+	 * Write out a pidfile if root.
 	 */
-	if (ipaddr == NULL) {
-	    struct hostent	*he;
-	    struct in_addr	myip;
-	    
-	    if (gethostname(buf, sizeof(buf)) < 0) {
-		fatal("could not get hostname");
-	    }
-
-	    if (! (he = gethostbyname(buf))) {
-		fatal("could not get IP address from hostname: %s", buf);
-	    }
-	    memcpy((char *)&myip, he->h_addr, he->h_length);
-	    strcpy(ipbuf, inet_ntoa(myip));
-	    ipaddr = ipbuf;
+	if (!getuid()) {
+		if (pidfile)
+			strcpy(buf, pidfile);
+		else
+			sprintf(buf, "%s/progagent.pid", _PATH_VARRUN);
+		fp = fopen(buf, "w");
+		if (fp != NULL) {
+			fprintf(fp, "%d\n", getpid());
+			(void) fclose(fp);
+		}
 	}
 
+	/*
+	 * Flip to the user, but only if we are currently root.
+	 */
+	if (! getuid()) {
+		struct passwd *pw;
+
+		/*
+		 * Must be a valid user of course.
+		 */
+		if ((pw = getpwnam(user)) == NULL)
+			fatal("invalid user: %s", user);
+
+		/*
+		 * Initialize the group list, and then flip to uid.
+		 */
+		if (setgid(pw->pw_gid) ||
+		    initgroups(user, pw->pw_gid) ||
+		    setuid(pw->pw_uid)) {
+			fatal("Could not become user: %s", user);
+		}
+	}
+	
 	/*
 	 * Convert server/port to elvin thing.
 	 *
@@ -139,13 +189,11 @@ main(int argc, char **argv)
 		fatal("could not allocate an address tuple");
 	}
 	/*
-	 * We want to get all program events for this node. We will
-	 * suck out the objname from the notification, and use that
-	 * as the handle while it is running.
+	 * Ask for just the program agents we care about. 
 	 */
-	tuple->host	 = ipaddr;
+	tuple->expt      = pideid;
 	tuple->objtype   = TBDB_OBJECTTYPE_PROGRAM;
-	tuple->objname   = ADDRESSTUPLE_ANY;
+	tuple->objname   = agentlist;
 	tuple->eventtype = ADDRESSTUPLE_ANY;
 
 	/*