Get rid of a null-pointer dereference when dissecting DNS requests with

a query count of 0 (no, such a request makes no sense, but that's what
tcpdump thought it saw in one DNS-over-TCP capture).

diff --git a/print-domain.c b/print-domain.c
index 2e73a8e50fcfa1e4fe52a4e47b3e2f20a90161e5..b8ff06b8129ba5c2881e536f12a208f44adfa974 100644 (file)
--- a/print-domain.c
+++ b/print-domain.c
@@ -21,7 +21,7 @@
 
 #ifndef lint
 static const char rcsid[] =
-    "@(#) $Header: /tcpdump/master/tcpdump/print-domain.c,v 1.77 2001-09-17 21:58:00 fenner Exp $ (LBL)";
+    "@(#) $Header: /tcpdump/master/tcpdump/print-domain.c,v 1.78 2001-10-19 09:00:48 guy Exp $ (LBL)";
 #endif
 
 #ifdef HAVE_CONFIG_H
@@ -508,7 +508,7 @@ ns_print(register const u_char *bp, u_int length)
 {
        register const HEADER *np;
        register int qdcount, ancount, nscount, arcount;
-       register const u_char *cp = NULL;
+       register const u_char *cp;
 
        np = (const HEADER *)bp;
        TCHECK(*np);
@@ -538,12 +538,10 @@ ns_print(register const u_char *bp, u_int length)
                                putchar(',');
                        if (vflag > 1) {
                                fputs(" q:", stdout);
-                               if ((cp = ns_qprint((const u_char *)(np + 1), bp))
-                                   == NULL)
+                               if ((cp = ns_qprint(cp, bp)) == NULL)
                                        goto trunc;
                        } else {
-                               if ((cp = ns_nskip((const u_char *)(np + 1), bp))
-                                   == NULL)
+                               if ((cp = ns_nskip(cp, bp)) == NULL)
                                        goto trunc;
                                cp += 4;        /* skip QTYPE and QCLASS */
                        }
@@ -615,9 +613,9 @@ ns_print(register const u_char *bp, u_int length)
                if (arcount)
                        printf(" [%dau]", arcount);
 
+               cp = (const u_char *)(np + 1);
                if (qdcount--) {
-                       cp = ns_qprint((const u_char *)(np + 1),
-                                      (const u_char *)np);
+                       cp = ns_qprint(cp, (const u_char *)np);
                        if (!cp)
                                goto trunc;
                        while (cp < snapend && qdcount--) {