dhcpd,dumpleases: write and use 64-bit current time in lease file.

without it, determination of remaining lease time is unreliable.
 Yes, it's costly in code size, but without it, dumpleases output
 is misleading!

function                                             old     new   delta
read_leases                                          143     282    +139
dumpleases_main                                      447     572    +125
write_leases                                         193     233     +40
hton64                                                29      58     +29
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 4/0 up/down: 333/0)             Total: 333 bytes

networking/udhcp/dumpleases.c

@@ -6,14 +6,24 @@
 #include "common.h"
 #include "dhcpd.h"
 
+#if BB_LITTLE_ENDIAN
+static inline uint64_t hton64(uint64_t v)
+{
+        return (((uint64_t)htonl(v)) << 32) | htonl(v >> 32);
+}
+#else
+#define hton64(v) (v)
+#endif
+#define ntoh64(v) hton64(v)
+
+
 int dumpleases_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int dumpleases_main(int argc UNUSED_PARAM, char **argv)
 {
 	int fd;
 	int i;
 	unsigned opt;
-	leasetime_t expires;
+	int64_t written_at, curr, expires_abs;
-	leasetime_t curr;
 	const char *file = LEASES_FILE;
 	struct dhcpOfferedAddr lease;
 	struct in_addr addr;
@@ -40,7 +50,13 @@ int dumpleases_main(int argc UNUSED_PARAM, char **argv)
 	printf("Mac Address       IP-Address      Expires %s\n", (opt & OPT_a) ? "at" : "in");
 	/*     "00:00:00:00:00:00 255.255.255.255 Wed Jun 30 21:49:08 1993" */
 
+	if (full_read(fd, &written_at, sizeof(written_at)) != sizeof(written_at))
+		return 0;
+	written_at = ntoh64(written_at);
 	curr = time(NULL);
+	if (curr < written_at)
+		written_at = curr; /* lease file from future! :) */
+
 	while (full_read(fd, &lease, sizeof(lease)) == sizeof(lease)) {
 		const char *fmt = ":%02x" + 1;
 		for (i = 0; i < 6; i++) {
@@ -49,13 +65,14 @@ int dumpleases_main(int argc UNUSED_PARAM, char **argv)
 		}
 		addr.s_addr = lease.yiaddr;
 		printf(" %-15s ", inet_ntoa(addr));
-		if (lease.expires == 0) {
+		expires_abs = ntohl(lease.expires) + written_at;
+		if (expires_abs <= curr) {
 			puts("expired");
 			continue;
 		}
-		expires = ntohl(lease.expires);
 		if (!(opt & OPT_a)) { /* no -a */
 			unsigned d, h, m;
+			unsigned expires = expires_abs - curr;
 			d = expires / (24*60*60); expires %= (24*60*60);
 			h = expires / (60*60); expires %= (60*60);
 			m = expires / 60; expires %= 60;
@@ -63,7 +80,7 @@ int dumpleases_main(int argc UNUSED_PARAM, char **argv)
 				printf("%u days ", d);
 			printf("%02u:%02u:%02u\n", h, m, (unsigned)expires);
 		} else { /* -a */
-			time_t t = expires + curr;
+			time_t t = expires_abs;
 			fputs(ctime(&t), stdout);
 		}
 	}

networking/udhcp/files.c

@@ -12,6 +12,16 @@
 #include "dhcpd.h"
 #include "options.h"
 
+#if BB_LITTLE_ENDIAN
+static inline uint64_t hton64(uint64_t v)
+{
+        return (((uint64_t)htonl(v)) << 32) | htonl(v >> 32);
+}
+#else
+#define hton64(v) (v)
+#endif
+#define ntoh64(v) hton64(v)
+
 
 /* on these functions, make sure your datatype matches */
 static int read_ip(const char *line, void *arg)
@@ -335,14 +345,16 @@ void FAST_FUNC write_leases(void)
 	int fd;
 	unsigned i;
 	leasetime_t curr;
+	int64_t written_at;
 
 	fd = open_or_warn(server_config.lease_file, O_WRONLY|O_CREAT|O_TRUNC);
 	if (fd < 0)
 		return;
 
-	curr = time(NULL);
+	curr = written_at = time(NULL);
-//TODO: write out current time? Readers need to adjust .expires field
+
-// to account for time between file was written and when it was read back.
+	written_at = hton64(written_at);
+	full_write(fd, &written_at, sizeof(written_at));
 
 	for (i = 0; i < server_config.max_leases; i++) {
 		leasetime_t tmp_time;
@@ -353,11 +365,9 @@ void FAST_FUNC write_leases(void)
 		/* screw with the time in the struct, for easier writing */
 		tmp_time = leases[i].expires;
 
-		//if (server_config.remaining) {
+		leases[i].expires -= curr;
-			leases[i].expires -= curr;
+		if ((signed_leasetime_t) leases[i].expires < 0)
-			if ((signed_leasetime_t) leases[i].expires < 0)
+			leases[i].expires = 0;
-				leases[i].expires = 0;
-		//} /* else stick with the time we got */
 		leases[i].expires = htonl(leases[i].expires);
 
 		/* No error check. If the file gets truncated,
@@ -382,14 +392,20 @@ void FAST_FUNC read_leases(const char *file)
 {
 	int fd;
 	unsigned i;
-//	leasetime_t curr;
 	struct dhcpOfferedAddr lease;
+	int64_t written_at, curr;
 
 	fd = open_or_warn(file, O_RDONLY);
 	if (fd < 0)
 		return;
 
-//	curr = time(NULL);
+	if (full_read(fd, &written_at, sizeof(written_at)) != sizeof(written_at))
+		goto ret;
+	written_at = ntoh64(written_at);
+	curr = time(NULL);
+	if (curr < written_at)
+		written_at = curr; /* lease file from future! :) */
+
 	i = 0;
 	while (i < server_config.max_leases
 	 && full_read(fd, &lease, sizeof(lease)) == sizeof(lease)
@@ -397,9 +413,9 @@ void FAST_FUNC read_leases(const char *file)
 		/* ADDME: what if it matches some static lease? */
 		uint32_t y = ntohl(lease.yiaddr);
 		if (y >= server_config.start_ip && y <= server_config.end_ip) {
-			leasetime_t expires = ntohl(lease.expires);
+			int64_t expires = ntohl(lease.expires) + written_at - curr;
-//			if (!server_config.remaining)
+			if (expires <= 0)
-//				expires -= curr;
+				continue;
 			/* NB: add_lease takes "relative time", IOW,
 			 * lease duration, not lease deadline. */
 			if (!(add_lease(lease.chaddr, lease.yiaddr, expires))) {
@@ -410,5 +426,6 @@ void FAST_FUNC read_leases(const char *file)
 		}
 	}
 	DEBUG("Read %d leases", i);
+ ret:
 	close(fd);
 }