X-Git-Url: https://git.tcpdump.org/tcpdump/blobdiff_plain/7ceb6016de4e188a215427bc035a941ad1fceb1c..0023eaa78f123676bfa9c5fba72ea4b8a59aaa70:/ntp.c?ds=sidebyside

diff --git a/ntp.c b/ntp.c
index 10fabe4b..d1825664 100644
--- a/ntp.c
+++ b/ntp.c
@@ -20,18 +20,20 @@
  *
  */
 
-#ifdef HAVE_CONFIG_H
 #include <config.h>
-#endif
 
 #include "ntp.h"
 
 #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(netdissect_options *ndo,
+p_ntp_time_fmt(netdissect_options *ndo, const char *fmt,
 	   const struct l_fixedpt *lfp)
 {
 	uint32_t i;
@@ -52,32 +54,33 @@ p_ntp_time(netdissect_options *ndo,
 	 * 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;
-	    struct tm *tm;
 	    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.
 		 */
-		ND_PRINT(" (unrepresentable)");
+		time_string = "[timestamp overflow]";
 	    } 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(" (unrepresentable)");
-		} else {
-		    /* use ISO 8601 (RFC3339) format */
-		    strftime(time_buf, sizeof (time_buf), "%Y-%m-%dT%H:%M:%SZ", tm);
-		    ND_PRINT(" (%s)", time_buf);
-		}
+		time_string = nd_format_time(time_buf, sizeof (time_buf),
+					     fmt, gmtime(&seconds));
 	    }
+	    ND_PRINT(" (%s)", time_string);
 	}
 }
+
+void
+p_ntp_time(netdissect_options *ndo, const struct l_fixedpt *lfp)
+{
+	/* use ISO 8601 (RFC3339) format */
+	p_ntp_time_fmt(ndo, "%Y-%m-%dT%H:%M:%SZ", lfp);
+}