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

1 files changed, 22 insertions, 5 deletions

diff --git a/networking/udhcp/dumpleases.c b/networking/udhcp/dumpleases.c
index 2d16ec1..c0d515d 100644
--- a/networking/udhcp/dumpleases.c
+++ b/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;
-	leasetime_t curr;
+	int64_t written_at, curr, expires_abs;
 	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);
 		}
 	}