Fix handling of NTP time stamps.

[tcpdump] / print-ntp.c

diff --git a/print-ntp.c b/print-ntp.c
index 3ccf9833bb2dce16d83000955e0fb68c980533e8..cf403c0c0472fa843efd028b0a18a05fc191a069 100644 (file)
--- a/print-ntp.c
+++ b/print-ntp.c
@@ -48,7 +48,7 @@ static const char tstr[] = " [|ntp]";
 /*
  *  Definitions for the masses
  */
-#define        JAN_1970        2208988800U     /* 1970 - 1900 in seconds */
+#define        JAN_1970        2208988800      /* 1970 - 1900 in seconds */
 
 /*
  * Structure definitions for NTP fixed point values
@@ -498,7 +498,7 @@ static void
 p_ntp_time(netdissect_options *ndo,
            register const struct l_fixedpt *lfp)
 {
-       register int32_t i;
+       register uint32_t i;
        register uint32_t uf;
        register uint32_t f;
        register double ff;
@@ -517,14 +517,33 @@ p_ntp_time(netdissect_options *ndo,
         * print the UTC time in human-readable format.
         */
        if (i) {
-           time_t seconds = i - JAN_1970;
+           int64_t seconds_64bit = (int64_t)i - JAN_1970;
+           time_t seconds;
            struct tm *tm;
            char time_buf[128];
 
-           tm = gmtime(&seconds);
-           /* use ISO 8601 (RFC3339) format */
-           strftime(time_buf, sizeof (time_buf), "%Y-%m-%dT%H:%M:%S", tm);
-           ND_PRINT((ndo, " (%s)", time_buf));
+           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.
+                */
+               ND_PRINT((ndo, " (unrepresentable)"));
+           } else {
+               tm = gmtime(&seconds);
+               if (tm == NULL) {
+                   /*
+                    * gmtime() can't handle it.
+                    * (Yes, that might happen with some version of
+                    * Microsoft's C library.)
+                    */
+                   ND_PRINT((ndo, " (unrepresentable)"));
+               } else {
+                   /* use ISO 8601 (RFC3339) format */
+                   strftime(time_buf, sizeof (time_buf), "%Y-%m-%dT%H:%M:%S", tm);
+                   ND_PRINT((ndo, " (%s)", time_buf));
+               }
+           }
        }
 #endif
 }