Add cookies to the heartbeat packet for added safety.v1.10-1

Two factors forced this change.
 1. ports were being re-used so quickly that we could get lingering
    packets from past hosts when getting the btime for a new host.
 2. We can't control which IP a btime response is sent from if a system
    has more than one interface.  Adding a cookie allows us to know that
    a response came from whom we sent it.

1 files changed, 18 insertions, 5 deletions

diff --git a/btimed.c b/btimed.c
index 544d108..c02b0bc 100644
--- a/btimed.c
+++ b/btimed.c
@@ -22,9 +22,11 @@ main(int argc, char **argv)
 {
 	int sd;
 	char inmsg[BTIME_MSGLEN];
-	char outmsg[BTIME_MSGLEN];
+	char btimeonly[BTIME_MSGLEN];
+	char cookiemsg[BTIME_MSGLEN];
+	char *outmsg;
 	struct sockaddr_in cli_addr;
-	int cli_addr_len;
+	socklen_t cli_addr_len;
 	ssize_t nbytes;
 	unsigned int local_btime;
 
@@ -37,13 +39,14 @@ main(int argc, char **argv)
 	alarm(30);
 
 	/* Generate the standard btime message */
-	memset(outmsg, 0, BTIME_MSGLEN);
+	memset(btimeonly, 0, BTIME_MSGLEN);
 	local_btime = get_btime();
-	sprintf(outmsg, "%u\n", local_btime);
+	sprintf(btimeonly, "%u\n", local_btime);
 
 	syslog(LOG_INFO, "started with btime = %u", local_btime);
 	for (;;) {
 		memset(&cli_addr, 0, sizeof cli_addr);
+		memset(inmsg, 0, BTIME_MSGLEN);
 		cli_addr_len = sizeof cli_addr;
 		nbytes = recvfrom(sd, &inmsg, BTIME_MSGLEN, MSG_WAITALL, 
 		         (struct sockaddr *)&cli_addr, &cli_addr_len);
@@ -55,8 +58,18 @@ main(int argc, char **argv)
 			syslog(LOG_INFO, "exitting");
 			exit(0);
 		}
+		if (inmsg[0] == 'B' && inmsg[1] == 'T' ) {
+			/* New style heartbeat with cookie */
+			/* Copy cookie to message and append timestamp */
+			memset(cookiemsg, 0, BTIME_MSGLEN);
+			memcpy(cookiemsg, inmsg, COOKIE_LEN);
+			strcpy(cookiemsg + COOKIE_LEN, btimeonly);
+			outmsg = cookiemsg;
+		} else {
+			outmsg = btimeonly;
+		}
 
-		sendto(sd, &outmsg, BTIME_MSGLEN, MSG_DONTWAIT, 
+		sendto(sd, outmsg, BTIME_MSGLEN, MSG_DONTWAIT, 
 		       (struct sockaddr *)&cli_addr, cli_addr_len);
 		/* We want to exit after 30 seconds of inactivity */
 		alarm(30);