Avoid -E and -M options inconsistencies with no libcrypto

[tcpdump] / ntp.c

diff --git a/ntp.c b/ntp.c
index 6c4b7f32fde787c5e31129d4a43e5722702fc766..d1825664bbc7cb565c388b80ba64c0f1f8db3f8a 100644 (file)
--- a/ntp.c
+++ b/ntp.c
@@ -26,7 +26,11 @@
 
 #include "extract.h"
 
-#define        JAN_1970        INT64_T_CONSTANT(2208988800)    /* 1970 - 1900 in seconds */
+/* NTP epoch 1: January 1, 1900, 00:00:00 UTC. */
+#define DIFF_1970_1900 INT64_C(2208988800) /* 1970 - 1900 in seconds */
+/* RFC4330 - 3. NTP Timestamp Format - 6h 28m 16s UTC on 7 February 2036 */
+/* NTP epoch 2: February 7, 2036, 06:28:16 UTC. */
+#define DIFF_2036_1970 INT64_C(2085978496) /* 2036 - 1970 in seconds */
 
 void
 p_ntp_time_fmt(netdissect_options *ndo, const char *fmt,
@@ -50,21 +54,25 @@ p_ntp_time_fmt(netdissect_options *ndo, const char *fmt,
         * print the UTC time in human-readable format.
         */
        if (i) {
-           int64_t seconds_64bit = (int64_t)i - JAN_1970;
+           int64_t seconds_64bit;
            time_t seconds;
            char time_buf[128];
            const char *time_string;
 
+           if ((i & 0x80000000) != 0)
+               seconds_64bit = (int64_t)i - DIFF_1970_1900;
+           else
+               seconds_64bit = (int64_t)i + DIFF_2036_1970;
            seconds = (time_t)seconds_64bit;
            if (seconds != seconds_64bit) {
                /*
                 * It doesn't fit into a time_t, so we can't hand it
                 * to gmtime.
                 */
-               time_string = "[Time is too large to fit into a time_t]";
+               time_string = "[timestamp overflow]";
            } else {
                time_string = nd_format_time(time_buf, sizeof (time_buf),
-                 fmt, gmtime(&seconds));
+                                            fmt, gmtime(&seconds));
            }
            ND_PRINT(" (%s)", time_string);
        }