L2TP: Modernize packet parsing style.

Enable ND_LONGJMP_FROM_TCHECK. Report invalid packets as invalid with a
reason, not truncated.

diff --git a/CHANGES b/CHANGES
index 4de9f0c24e9c961ccfe5a6677d62d52a0ed16b35..9114ff2e13b17a506fc970a23701950abd1ec450 100644 (file)
--- a/CHANGES
+++ b/CHANGES
@@ -2,7 +2,7 @@ Monthday, Month DD, YYYY by gharris
   Summary for 5.0.0 tcpdump release (so far!)
     Source code:
       Use %zu when printing a sizeof to squelch compiler warnings
-      Geneve, OLSR, PGM, RSVP: Modernize packet parsing style
+      Geneve, L2TP, OLSR, PGM, RSVP: Modernize packet parsing style
       EGP: Replace custom code with tok2str()
 
 Monthday, Month DD, YYYY by gharris

diff --git a/print-l2tp.c b/print-l2tp.c
index 8377d3a796329ad3e517b44bc3474f7960613877..51bb93a04122e6fab17da1c8c020deb03f32b1fb 100644 (file)
--- a/print-l2tp.c
+++ b/print-l2tp.c
@@ -31,6 +31,7 @@
 
 #include "netdissect-stdinc.h"
 
+#define ND_LONGJMP_FROM_TCHECK
 #include "netdissect.h"
 #include "extract.h"
 
@@ -576,13 +577,17 @@ l2tp_avp_print(netdissect_options *ndo, const u_char *dat, u_int length)
        len = GET_BE_U_2(dat) & L2TP_AVP_HDR_LEN_MASK;
 
        /* If it is not long enough to contain the header, we'll give up. */
-       if (len < 6)
-               goto trunc;
+       if (len < 6) {
+               ND_PRINT(" (AVP length %u < 6)", len);
+               goto invalid;
+       }
 
        /* If it goes past the end of the remaining length of the packet,
           we'll give up. */
-       if (len > (u_int)length)
-               goto trunc;
+       if (len > length) {
+               ND_PRINT(" (len > %u)", length);
+               goto invalid;
+       }
 
        /* If it goes past the end of the remaining length of the captured
           data, we'll give up. */
@@ -727,8 +732,7 @@ l2tp_avp_print(netdissect_options *ndo, const u_char *dat, u_int length)
 
        return (len);
 
- trunc:
-       nd_print_trunc(ndo);
+invalid:
        return (0);
 }
 
@@ -813,18 +817,18 @@ l2tp_print(netdissect_options *ndo, const u_char *dat, u_int length)
        if (flag_l) {
                if (length < l2tp_len) {
                        ND_PRINT(" Length %u larger than packet", l2tp_len);
-                       return;
+                       goto invalid;
                }
                length = l2tp_len;
        }
        if (length < cnt) {
                ND_PRINT(" Length %u smaller than header length", length);
-               return;
+               goto invalid;
        }
        if (flag_t) {
                if (!flag_l) {
                        ND_PRINT(" No length");
-                       return;
+                       goto invalid;
                }
                if (length - cnt == 0) {
                        ND_PRINT(" ZLB");
@@ -837,10 +841,7 @@ l2tp_print(netdissect_options *ndo, const u_char *dat, u_int length)
 
                                avp_length = l2tp_avp_print(ndo, ptr, length - cnt);
                                if (avp_length == 0) {
-                                       /*
-                                        * Truncated.
-                                        */
-                                       break;
+                                       goto invalid;
                                }
                                cnt += avp_length;
                                ptr += avp_length;
@@ -851,4 +852,7 @@ l2tp_print(netdissect_options *ndo, const u_char *dat, u_int length)
                ppp_print(ndo, ptr, length - cnt);
                ND_PRINT("}");
        }
+       return;
+invalid:
+       nd_print_invalid(ndo);
 }