VTP: Modernize packet parsing style.

Enable ND_LONGJMP_FROM_TCHECK. Constify an argument. Add a standard
"invalid" label and use it in packet validation. Test whether the packet
is truncated even if it is not fully printed. Lose a few excess
ND_TCHECK*() instances. Replace a hard-coded value with a named constant.
Update two tests.

3 files changed, 17 insertions, 20 deletions

diff --git a/print-vtp.c b/print-vtp.c
index e1b8377a..e0c7ded2 100644
--- a/print-vtp.c
+++ b/print-vtp.c
@@ -27,6 +27,7 @@
 
 #include "netdissect-stdinc.h"
 
+#define ND_LONGJMP_FROM_TCHECK
 #include "netdissect.h"
 #include "addrtoname.h"
 #include "extract.h"
@@ -117,7 +118,7 @@ static const struct tok vtp_stp_type_values[] = {
 
 void
 vtp_print(netdissect_options *ndo,
-          const u_char *pptr, u_int length)
+          const u_char *pptr, const u_int length)
 {
     u_int type, len, name_len, tlv_len, tlv_value, mgmtd_len;
     const u_char *tptr;
@@ -125,7 +126,7 @@ vtp_print(netdissect_options *ndo,
 
     ndo->ndo_protocol = "vtp";
     if (length < VTP_HEADER_LEN)
-        goto trunc;
+        goto invalid;
 
     tptr = pptr;
 
@@ -140,15 +141,15 @@ vtp_print(netdissect_options *ndo,
 
     /* In non-verbose mode, just print version and message type */
     if (ndo->ndo_vflag < 1) {
-        return;
+        goto tcheck_full_packet;
     }
 
     /* verbose mode print all fields */
     ND_PRINT("\n\tDomain name: ");
     mgmtd_len = GET_U_1(tptr + 3);
-    if (mgmtd_len < 1 ||  mgmtd_len > 32) {
+    if (mgmtd_len < 1 ||  mgmtd_len > VTP_DOMAIN_NAME_LEN) {
 	ND_PRINT(" [invalid MgmtD Len %u]", mgmtd_len);
-	return;
+	goto invalid;
     }
     nd_printzp(ndo, tptr + 4, mgmtd_len, NULL);
     ND_PRINT(", %s: %u",
@@ -181,18 +182,15 @@ vtp_print(netdissect_options *ndo,
 	 *
 	 */
 
-	ND_TCHECK_8(tptr);
 	ND_PRINT("\n\t  Config Rev %x, Updater %s",
 	       GET_BE_U_4(tptr),
 	       GET_IPADDR_STRING(tptr+4));
 	tptr += 8;
-	ND_TCHECK_LEN(tptr, VTP_UPDATE_TIMESTAMP_LEN);
 	ND_PRINT(", Timestamp 0x%08x 0x%08x 0x%08x",
 	       GET_BE_U_4(tptr),
 	       GET_BE_U_4(tptr + 4),
 	       GET_BE_U_4(tptr + 8));
 	tptr += VTP_UPDATE_TIMESTAMP_LEN;
-	ND_TCHECK_LEN(tptr, VTP_MD5_DIGEST_LEN);
 	ND_PRINT(", MD5 digest: %08x%08x%08x%08x",
 	       GET_BE_U_4(tptr),
 	       GET_BE_U_4(tptr + 4),
@@ -251,8 +249,7 @@ vtp_print(netdissect_options *ndo,
 
 	    vtp_vlan = (const struct vtp_vlan_*)tptr;
 	    if (len < VTP_VLAN_INFO_FIXED_PART_LEN)
-		goto trunc;
-	    ND_TCHECK_SIZE(vtp_vlan);
+		goto invalid;
 	    ND_PRINT("\n\tVLAN info status %s, type %s, VLAN-id %u, MTU %u, SAID 0x%08x, Name ",
 		   tok2str(vtp_vlan_status,"Unknown",GET_U_1(vtp_vlan->status)),
 		   tok2str(vtp_vlan_type_values,"Unknown",GET_U_1(vtp_vlan->type)),
@@ -263,8 +260,7 @@ vtp_print(netdissect_options *ndo,
 	    tptr += VTP_VLAN_INFO_FIXED_PART_LEN;
 	    name_len = GET_U_1(vtp_vlan->name_len);
 	    if (len < 4*((name_len + 3)/4))
-		goto trunc;
-	    ND_TCHECK_LEN(tptr, name_len);
+		goto invalid;
 	    nd_printzp(ndo, tptr, name_len, NULL);
 
 	    /*
@@ -285,8 +281,7 @@ vtp_print(netdissect_options *ndo,
                  * what we do.
                  */
                 if (len < 2)
-                    goto trunc;
-                ND_TCHECK_2(tptr);
+                    goto invalid;
                 type = GET_U_1(tptr);
                 tlv_len = GET_U_1(tptr + 1);
 
@@ -296,7 +291,7 @@ vtp_print(netdissect_options *ndo,
 
                 if (len < tlv_len * 2 + 2) {
                     ND_PRINT(" (TLV goes past the end of the packet)");
-                    return;
+                    goto invalid;
                 }
                 ND_TCHECK_LEN(tptr, tlv_len * 2 + 2);
 
@@ -306,7 +301,7 @@ vtp_print(netdissect_options *ndo,
                  */
                 if (tlv_len != 1) {
                     ND_PRINT(" (invalid TLV length %u != 1)", tlv_len);
-                    return;
+                    goto invalid;
                 } else {
                     tlv_value = GET_BE_U_2(tptr + 2);
 
@@ -390,6 +385,8 @@ vtp_print(netdissect_options *ndo,
 
     return;
 
- trunc:
-    nd_print_trunc(ndo);
+invalid:
+    nd_print_invalid(ndo);
+tcheck_full_packet:
+    ND_TCHECK_LEN(pptr, length);
 }
diff --git a/tests/vtp_asan-2.out b/tests/vtp_asan-2.out
index 52417801..cb4b051a 100644
--- a/tests/vtp_asan-2.out
+++ b/tests/vtp_asan-2.out
@@ -1,2 +1,2 @@
     1  11:13:40.2148532227 FRF.16 Frag, seq 193, Flags [Begin, End], UI 08! VTPv69, Message Subset advertisement (0x02), length 262131
-	Domain name: , Seq number: 0, Config Rev fb499603 [|vtp]
+	Domain name: , Seq number: 0, Config Rev fb499603 (invalid) [|vtp]
diff --git a/tests/vtp_asan-3.out b/tests/vtp_asan-3.out
index 02ded296..5a8cf267 100644
--- a/tests/vtp_asan-3.out
+++ b/tests/vtp_asan-3.out
@@ -1,2 +1,2 @@
     1  11:13:40.2148532227 FRF.16 Frag, seq 193, Flags [Begin, End], UI 08! VTPv69, Message Subset advertisement (0x02), length 262131
-	Domain name: , Seq number: 0, Config Rev 4040404 [|vtp]
+	Domain name: , Seq number: 0, Config Rev 4040404 (invalid) [|vtp]