Update ND_BYTES_BETWEEN() macro for better accuracy

Update the macro that computes how many bytes are present, starting
at the first argument and running up to (but not including) the second
argument, and returns that as a u_int (cutting it to 32 bits on LP64
and LLP64 platforms).

This reverses, for reasons of readability, the order of the arguments
which was based on old SMB's PTR_DIFF().

With this change the number of bytes "between" given by the macro is 0
when the first argument is greater than or equal to the second argument.

Update ND_BYTES_AVAILABLE_AFTER() accordingly.

This is a follow-up to f9c2c905b118b69a0b102549c1b25cca871947b5.

diff --git a/netdissect.h b/netdissect.h
index 4f917eebb1eeb25ba86d9f3b8bde013e3aa31b11..09845be6402a436930721d83fb91b081a22e8a81 100644 (file)
--- a/netdissect.h
+++ b/netdissect.h
@@ -385,13 +385,13 @@ nd_trunc_longjmp(netdissect_options *ndo)
 /*
  * Number of bytes between two pointers.
  */
-#define ND_BYTES_BETWEEN(p1, p2) ((u_int)(((const uint8_t *)(p1)) - (const uint8_t *)(p2)))
+#define ND_BYTES_BETWEEN(p1, p2) ((const u_char *)(p1) >= (const u_char *)(p2) ? 0 : ((u_int)(((const u_char *)(p2)) - (const u_char *)(p1))))
 
 /*
  * Number of bytes remaining in the captured data, starting at the
  * byte pointed to by the argument.
  */
-#define ND_BYTES_AVAILABLE_AFTER(p) ND_BYTES_BETWEEN(ndo->ndo_snapend, (p))
+#define ND_BYTES_AVAILABLE_AFTER(p) ND_BYTES_BETWEEN((p), ndo->ndo_snapend)
 
 /*
  * Check (expression_1 operator expression_2) for invalid packet with

diff --git a/print-bgp.c b/print-bgp.c
index 694346d733205956ce83733dc7c396eba0c0a3c3..db5b26b0532f21632f8586697eb9c8443a315787 100644 (file)
--- a/print-bgp.c
+++ b/print-bgp.c
@@ -2346,8 +2346,10 @@ bgp_attr_print(netdissect_options *ndo,
             ND_PRINT(", no SNPA");
         }
 
-        add_path4 = check_add_path(ndo, tptr, (len-ND_BYTES_BETWEEN(tptr, pptr)), 32);
-        add_path6 = check_add_path(ndo, tptr, (len-ND_BYTES_BETWEEN(tptr, pptr)), 128);
+        add_path4 = check_add_path(ndo, tptr,
+                                   (len-ND_BYTES_BETWEEN(pptr, tptr)), 32);
+        add_path6 = check_add_path(ndo, tptr,
+                                   (len-ND_BYTES_BETWEEN(pptr, tptr)), 128);
 
         while (tptr < pptr + len) {
             advance = bgp_nlri_print(ndo, af, safi, tptr, len, buf, sizeof(buf),
@@ -2373,8 +2375,10 @@ bgp_attr_print(netdissect_options *ndo,
 
         tptr += 3;
 
-        add_path4 = check_add_path(ndo, tptr, (len-ND_BYTES_BETWEEN(tptr, pptr)), 32);
-        add_path6 = check_add_path(ndo, tptr, (len-ND_BYTES_BETWEEN(tptr, pptr)), 128);
+        add_path4 = check_add_path(ndo, tptr,
+                                   (len-ND_BYTES_BETWEEN(pptr, tptr)), 32);
+        add_path6 = check_add_path(ndo, tptr,
+                                   (len-ND_BYTES_BETWEEN(pptr, tptr)), 128);
 
         while (tptr < pptr + len) {
             advance = bgp_nlri_print(ndo, af, safi, tptr, len, buf, sizeof(buf),

diff --git a/print-isoclns.c b/print-isoclns.c
index f506d4d9fadbb785d71939d877ee46f459c2d2a7..9e5b2234264a14b3dd49239061854e014bb40381 100644 (file)
--- a/print-isoclns.c
+++ b/print-isoclns.c
@@ -1126,9 +1126,10 @@ clnp_print(netdissect_options *ndo,
 
         default:
             /* dump the PDU specific data */
-            if (length > ND_BYTES_BETWEEN(pptr, optr)) {
+            if (length > ND_BYTES_BETWEEN(optr, pptr)) {
                 ND_PRINT("\n\t  undecoded non-header data, length %u", length-li);
-                print_unknown_data(ndo, pptr, "\n\t  ", length - ND_BYTES_BETWEEN(pptr, optr));
+                print_unknown_data(ndo, pptr, "\n\t  ",
+                                   length - ND_BYTES_BETWEEN(optr, pptr));
             }
         }
 

diff --git a/print-lwres.c b/print-lwres.c
index b8f9b49ae598c3b410de1bfa31032b0b5f54310b..f252275fc34ec8d54fbdcb7fbabbae3e3b11029e 100644 (file)
--- a/print-lwres.c
+++ b/print-lwres.c
@@ -267,7 +267,7 @@ lwres_printaddr(netdissect_options *ndo,
                }
        }
 
-       return ND_BYTES_BETWEEN(p, p0);
+       return ND_BYTES_BETWEEN(p0, p);
 }
 
 void
@@ -548,7 +548,7 @@ lwres_print(netdissect_options *ndo,
                ND_PRINT(" [len: %u != %u]", GET_BE_U_4(np->length),
                          length);
        }
-       if (!unsupported && ND_BYTES_BETWEEN(s, bp) < GET_BE_U_4(np->length))
+       if (!unsupported && ND_BYTES_BETWEEN(bp, s) < GET_BE_U_4(np->length))
                ND_PRINT("[extra]");
        return;
 

diff --git a/print-resp.c b/print-resp.c
index 37a386e3122c96f501266ef688a21beb75d1e180..7388a73fbd573dcb5c4779c9f720d871482a19d4 100644 (file)
--- a/print-resp.c
+++ b/print-resp.c
@@ -306,7 +306,7 @@ resp_print_string_error_integer(netdissect_options *ndo, const u_char *bp, int l
      * preceding the \r\n.  That includes the opcode, so don't print
      * that.
      */
-    len = ND_BYTES_BETWEEN(bp_ptr, bp);
+    len = ND_BYTES_BETWEEN(bp, bp_ptr);
     RESP_PRINT_SEGMENT(ndo, bp, len);
     ret_len = 1 /*<opcode>*/ + len /*<string>*/ + 2 /*<CRLF>*/;
 
@@ -431,7 +431,7 @@ resp_print_inline(netdissect_options *ndo, const u_char *bp, int length) {
      * Found it; bp_ptr points to the \r or \n, so bp_ptr - bp is the
      * Length of the line text that precedes it.  Print it.
      */
-    len = ND_BYTES_BETWEEN(bp_ptr, bp);
+    len = ND_BYTES_BETWEEN(bp, bp_ptr);
     RESP_PRINT_SEGMENT(ndo, bp, len);
 
     /*

diff --git a/print-smb.c b/print-smb.c
index bcd7363dec955c22a7cb42db4ee8bdd2d26f7fb0..fa7a2c024782d64ab23f34d2c075cfd494988d0a 100644 (file)
--- a/print-smb.c
+++ b/print-smb.c
@@ -414,7 +414,8 @@ print_negprot(netdissect_options *ndo,
        smb_fdata(ndo, words + 1, f1, ND_MIN(words + 1 + wct * 2, maxbuf),
            unicodestr);
     else
-       smb_data_print(ndo, words + 1, ND_MIN(wct * 2, ND_BYTES_BETWEEN(maxbuf, words + 1)));
+       smb_data_print(ndo, words + 1,
+                       ND_MIN(wct * 2, ND_BYTES_BETWEEN(words + 1, maxbuf)));
 
     bcc = GET_LE_U_2(data);
     ND_PRINT("smb_bcc=%u\n", bcc);
@@ -424,7 +425,7 @@ print_negprot(netdissect_options *ndo,
                                              maxbuf), unicodestr);
        else
            smb_data_print(ndo, data + 2,
-                           ND_MIN(GET_LE_U_2(data), ND_BYTES_BETWEEN(maxbuf, data + 2)));
+                           ND_MIN(GET_LE_U_2(data), ND_BYTES_BETWEEN(data + 2, maxbuf)));
     }
 }
 
@@ -454,7 +455,8 @@ print_sesssetup(netdissect_options *ndo,
        smb_fdata(ndo, words + 1, f1, ND_MIN(words + 1 + wct * 2, maxbuf),
            unicodestr);
     else
-       smb_data_print(ndo, words + 1, ND_MIN(wct * 2, ND_BYTES_BETWEEN(maxbuf, words + 1)));
+       smb_data_print(ndo, words + 1,
+                       ND_MIN(wct * 2, ND_BYTES_BETWEEN(words + 1, maxbuf)));
 
     bcc = GET_LE_U_2(data);
     ND_PRINT("smb_bcc=%u\n", bcc);
@@ -464,7 +466,7 @@ print_sesssetup(netdissect_options *ndo,
                                              maxbuf), unicodestr);
        else
            smb_data_print(ndo, data + 2,
-                           ND_MIN(GET_LE_U_2(data), ND_BYTES_BETWEEN(maxbuf, data + 2)));
+                           ND_MIN(GET_LE_U_2(data), ND_BYTES_BETWEEN(data + 2, maxbuf)));
     }
 }
 
@@ -499,7 +501,7 @@ print_lockingandx(netdissect_options *ndo,
                                              maxbuf), unicodestr);
        else
            smb_data_print(ndo, data + 2,
-                           ND_MIN(GET_LE_U_2(data), ND_BYTES_BETWEEN(maxbuf, data + 2)));
+                           ND_MIN(GET_LE_U_2(data), ND_BYTES_BETWEEN(data + 2, maxbuf)));
     }
 }
 
@@ -871,7 +873,8 @@ print_smb(netdissect_options *ndo,
            } else {
                if (bcc > 0) {
                    ND_PRINT("smb_buf[]=\n");
-                   smb_data_print(ndo, data + 2, ND_MIN(bcc, ND_BYTES_BETWEEN(maxbuf, data + 2)));
+                   smb_data_print(ndo, data + 2,
+                                   ND_MIN(bcc, ND_BYTES_BETWEEN(data + 2, maxbuf)));
                }
            }
        }
@@ -1194,7 +1197,8 @@ nbt_udp137_print(netdissect_options *ndo,
                } else {
                    if (p >= maxbuf)
                        goto out;
-                   smb_data_print(ndo, p, ND_MIN(rdlen, length - ND_BYTES_BETWEEN(p, data)));
+                   smb_data_print(ndo, p,
+                                   ND_MIN(rdlen, length - ND_BYTES_BETWEEN(data, p)));
                    p += rdlen;
                }
            }

diff --git a/smbutil.c b/smbutil.c
index 97217a8d9fc6a8a4def9fbd160b9217e37cd2d92..e512e324d6a056a11853ba362d6e25b3faa3a5b4 100644 (file)
--- a/smbutil.c
+++ b/smbutil.c
@@ -251,7 +251,7 @@ name_len(netdissect_options *ndo,
        s += GET_U_1(s) + 1;
        ND_TCHECK_1(s);
     }
-    return(ND_BYTES_BETWEEN(s, s0) + 1);
+    return(ND_BYTES_BETWEEN(s0, s) + 1);
 
 trunc:
     return(-1);        /* name goes past the end of the buffer */
@@ -334,7 +334,7 @@ write_bits(netdissect_options *ndo,
     u_int i = 0;
 
     while ((p = strchr(fmt, '|'))) {
-       u_int l = ND_BYTES_BETWEEN(p, fmt);
+       u_int l = ND_BYTES_BETWEEN(fmt, p);
        if (l && (val & (1 << i)))
            ND_PRINT("%.*s ", (int)l, fmt);
        fmt = p + 1;
@@ -493,7 +493,7 @@ smb_fdata1(netdissect_options *ndo,
            u_int l;
 
            p = strchr(++fmt, '}');
-           l = ND_BYTES_BETWEEN(p, fmt);
+           l = ND_BYTES_BETWEEN(fmt, p);
 
            if (l > sizeof(bitfmt) - 1)
                l = sizeof(bitfmt)-1;
@@ -742,8 +742,9 @@ smb_fdata1(netdissect_options *ndo,
 
            switch (t) {
            case 1:
-               name_type = name_extract(ndo, startbuf, ND_BYTES_BETWEEN(buf, startbuf),
-                   maxbuf, nbuf);
+               name_type = name_extract(ndo, startbuf,
+                                         ND_BYTES_BETWEEN(startbuf, buf),
+                                         maxbuf, nbuf);
                if (name_type < 0)
                    goto trunc;
                len = name_len(ndo, buf, maxbuf);
@@ -933,7 +934,7 @@ smb_fdata(netdissect_options *ndo,
        }
     }
     if (!depth && buf < maxbuf) {
-       u_int len = ND_BYTES_BETWEEN(maxbuf, buf);
+       u_int len = ND_BYTES_BETWEEN(buf, maxbuf);
        ND_PRINT("Data: (%u bytes)\n", len);
        smb_data_print(ndo, buf, len);
        return(buf + len);