X-Git-Url: https://git.tcpdump.org/tcpdump/blobdiff_plain/b5cbb4d2bbca5fda7fc3ab5996d416aaf727df30..refs/pull/1034/head:/print-ppp.c

diff --git a/print-ppp.c b/print-ppp.c
index baeb4f00..aba243dd 100644
--- a/print-ppp.c
+++ b/print-ppp.c
@@ -1363,7 +1363,7 @@ ppp_hdlc(netdissect_options *ndo,
 	u_char *b, *t, c;
 	const u_char *s;
 	u_int i, proto;
-	const void *se;
+	const void *sb, *se;
 
 	if (caplen == 0)
 		return;
@@ -1395,8 +1395,11 @@ ppp_hdlc(netdissect_options *ndo,
 
 	/*
 	 * Change the end pointer, so bounds checks work.
+	 * Change the pointer to packet data to help debugging.
 	 */
+	sb = ndo->ndo_packetp;
 	se = ndo->ndo_snapend;
+	ndo->ndo_packetp = b;
 	ndo->ndo_snapend = t;
 	length = ND_BYTES_AVAILABLE_AFTER(b);
 
@@ -1425,18 +1428,26 @@ ppp_hdlc(netdissect_options *ndo,
             if (length < 4)
                 goto trunc;
             proto = GET_BE_U_2(b + 2); /* load the PPP proto-id */
-            handle_ppp(ndo, proto, b + 4, length - 4);
+            if ((proto & 0xff00) == 0x7e00)
+                ND_PRINT("(protocol 0x%04x invalid)", proto);
+            else
+                handle_ppp(ndo, proto, b + 4, length - 4);
             break;
         default: /* last guess - proto must be a PPP proto-id */
-            handle_ppp(ndo, proto, b + 2, length - 2);
+            if ((proto & 0xff00) == 0x7e00)
+                ND_PRINT("(protocol 0x%04x invalid)", proto);
+            else
+                handle_ppp(ndo, proto, b + 2, length - 2);
             break;
         }
 
 cleanup:
+	ndo->ndo_packetp = sb;
 	ndo->ndo_snapend = se;
         return;
 
 trunc:
+	ndo->ndo_packetp = sb;
 	ndo->ndo_snapend = se;
 	nd_print_trunc(ndo);
 }
@@ -1559,11 +1570,18 @@ ppp_print(netdissect_options *ndo,
 		hdr_len += 2;
 	}
 
-	if (ndo->ndo_eflag)
-		ND_PRINT("%s (0x%04x), length %u: ",
-		          tok2str(ppptype2str, "unknown", proto),
+	if (ndo->ndo_eflag) {
+		const char *typestr;
+		typestr = tok2str(ppptype2str, "unknown", proto);
+		ND_PRINT("%s (0x%04x), length %u",
+		          typestr,
 		          proto,
 		          olen);
+		if (*typestr == 'u')	/* "unknown" */
+			return hdr_len;
+
+		ND_PRINT(": ");
+	}
 
 	handle_ppp(ndo, proto, p, length);
 	return (hdr_len);