Just use a u_char * to go through the packet data; don't try to be

clever and use a u_int16_t * - the generated code will be the same, and
this code works even if the Offset Size field value is odd.

diff --git a/print-l2tp.c b/print-l2tp.c
index 55c2125174ee96f326f5d39361b942a6bffd6cb8..2f726574e4ee3757b493bbdbd9707de6e5855d07 100644 (file)
--- a/print-l2tp.c
+++ b/print-l2tp.c
@@ -606,7 +606,7 @@ l2tp_avp_print(const u_char *dat, int length)
 void
 l2tp_print(const u_char *dat, u_int length)
 {
-       const u_int16_t *ptr = (u_int16_t *)dat;
+       const u_char *ptr = dat;
        u_int cnt = 0;                  /* total octets consumed */
        u_int16_t pad;
        int flag_t, flag_l, flag_s, flag_o;
@@ -614,7 +614,7 @@ l2tp_print(const u_char *dat, u_int length)
 
        flag_t = flag_l = flag_s = flag_o = FALSE;
 
-       TCHECK(*ptr);   /* Flags & Version */
+       TCHECK2(*ptr, 2);       /* Flags & Version */
        if ((EXTRACT_16BITS(ptr) & L2TP_VERSION_MASK) == L2TP_VERSION_L2TP) {
                printf(" l2tp:");
        } else if ((EXTRACT_16BITS(ptr) & L2TP_VERSION_MASK) == L2TP_VERSION_L2F) {
@@ -646,37 +646,42 @@ l2tp_print(const u_char *dat, u_int length)
                printf("P");
        printf("]");
 
-       ptr++;
+       ptr += 2;
        cnt += 2;
 
        if (flag_l) {
-               TCHECK(*ptr);   /* Length */
-               l2tp_len = EXTRACT_16BITS(ptr); ptr++;
+               TCHECK2(*ptr, 2);       /* Length */
+               l2tp_len = EXTRACT_16BITS(ptr);
+               ptr += 2;
                cnt += 2;
        } else {
                l2tp_len = 0;
        }
 
-       TCHECK(*ptr);           /* Tunnel ID */
-       printf("(%u/", EXTRACT_16BITS(ptr)); ptr++;
+       TCHECK2(*ptr, 2);               /* Tunnel ID */
+       printf("(%u/", EXTRACT_16BITS(ptr));
+       ptr += 2;
        cnt += 2;
-       TCHECK(*ptr);           /* Session ID */
-       printf("%u)",  EXTRACT_16BITS(ptr)); ptr++;
+       TCHECK2(*ptr, 2);               /* Session ID */
+       printf("%u)",  EXTRACT_16BITS(ptr));
+       ptr += 2;
        cnt += 2;
 
        if (flag_s) {
-               TCHECK(*ptr);   /* Ns */
-               printf("Ns=%u,", EXTRACT_16BITS(ptr)); ptr++;
+               TCHECK2(*ptr, 2);       /* Ns */
+               printf("Ns=%u,", EXTRACT_16BITS(ptr));
+               ptr += 2;
                cnt += 2;
-               TCHECK(*ptr);   /* Nr */
-               printf("Nr=%u",  EXTRACT_16BITS(ptr)); ptr++;
+               TCHECK2(*ptr, 2);       /* Nr */
+               printf("Nr=%u",  EXTRACT_16BITS(ptr));
+               ptr += 2;
                cnt += 2;
        }
 
        if (flag_o) {
-               TCHECK(*ptr);   /* Offset Size */
-               pad =  EXTRACT_16BITS(ptr); ptr++;
-               ptr += pad / sizeof(*ptr);
+               TCHECK2(*ptr, 2);       /* Offset Size */
+               pad =  EXTRACT_16BITS(ptr);
+               ptr += (2 + pad);
                cnt += (2 + pad);
        }
 
@@ -699,11 +704,11 @@ l2tp_print(const u_char *dat, u_int length)
                if (length - cnt == 0) {
                        printf(" ZLB");
                } else {
-                       l2tp_avp_print((u_char *)ptr, length - cnt);
+                       l2tp_avp_print(ptr, length - cnt);
                }
        } else {
                printf(" {");
-               ppp_print((u_char *)ptr, length - cnt);
+               ppp_print(ptr, length - cnt);
                printf("}");
        }