Do time stamp deltas with unsigned arithmetic.

First, check whether the originate timestamp is greater than the other
timestamp and, if so, calculate (originate - other) and print a -
instead of a + before it.  This means we're not trying to stuff the
difference between two unsigned values into a signed value of the same
width (the result of which is undefined if the difference doesn't fit in
the signed variable).

diff --git a/print-ntp.c b/print-ntp.c
index 7643ade1bb6f7a82080bd04ea5149bd8921b500e..faa31fa40b42e81e6dfc48ab3d6e2170c9c9631c 100644 (file)
--- a/print-ntp.c
+++ b/print-ntp.c
@@ -536,7 +536,7 @@ p_ntp_time(netdissect_options *ndo,
                ff += FMAXINT;
        ff = ff / FMAXINT;                      /* shift radix point by 32 bits */
        f = (uint32_t)(ff * 1000000000.0);      /* treat fraction as parts per billion */
-       ND_PRINT("%u.%09d", i, f);
+       ND_PRINT("%u.%09u", i, f);
 
 #ifdef HAVE_STRFTIME
        /*
@@ -580,9 +580,9 @@ p_ntp_delta(netdissect_options *ndo,
             const struct l_fixedpt *olfp,
             const struct l_fixedpt *lfp)
 {
-       int32_t i;
        uint32_t u, uf;
        uint32_t ou, ouf;
+       uint32_t i;
        uint32_t f;
        double ff;
        int signbit;
@@ -596,20 +596,20 @@ p_ntp_delta(netdissect_options *ndo,
                return;
        }
 
-       i = u - ou;
-
-       if (i > 0) {            /* new is definitely greater than old */
+       if (u > ou) {           /* new is definitely greater than old */
                signbit = 0;
+               i = u - ou;
                f = uf - ouf;
                if (ouf > uf)   /* must borrow from high-order bits */
                        i -= 1;
-       } else if (i < 0) {     /* new is definitely less than old */
+       } else if (u < ou) {    /* new is definitely less than old */
                signbit = 1;
+               i = ou - u;
                f = ouf - uf;
-               if (uf > ouf)   /* must carry into the high-order bits */
-                       i += 1;
-               i = -i;
+               if (uf > ouf)   /* must borrow from the high-order bits */
+                       i -= 1;
        } else {                /* int_part is zero */
+               i = 0;
                if (uf > ouf) {
                        signbit = 0;
                        f = uf - ouf;
@@ -624,7 +624,7 @@ p_ntp_delta(netdissect_options *ndo,
                ff += FMAXINT;
        ff = ff / FMAXINT;                      /* shift radix point by 32 bits */
        f = (uint32_t)(ff * 1000000000.0);      /* treat fraction as parts per billion */
-       ND_PRINT("%s%d.%09d", signbit ? "-" : "+", i, f);
+       ND_PRINT("%s%u.%09u", signbit ? "-" : "+", i, f);
 }
 
 /* Prints polling interval in log2 as seconds or fraction of second */