Patch from Gert Doering <gert@greenie.muc.de> to handle IPv6 addresses

in CDP packets.

Changes to use EXTRACT_ macros rather than extracting by hand, and to
use the "protocol type" field as well as the protocol and address
lengths and the protocol field when determining the address type.

1 files changed, 52 insertions, 8 deletions

diff --git a/print-cdp.c b/print-cdp.c
index a44a28d2..b8ede526 100644
--- a/print-cdp.c
+++ b/print-cdp.c
@@ -26,7 +26,7 @@
 
 #ifndef lint
 static const char rcsid[] =
-    "@(#) $Header: /tcpdump/master/tcpdump/print-cdp.c,v 1.9 2001-07-04 20:56:39 fenner Exp $";
+    "@(#) $Header: /tcpdump/master/tcpdump/print-cdp.c,v 1.10 2001-08-25 09:46:33 guy Exp $";
 #endif
 
 #ifdef HAVE_CONFIG_H
@@ -142,13 +142,29 @@ trunc:
 	printf("[|cdp]");
 }
 
+/*
+ * Protocol type values.
+ *
+ * PT_NLPID means that the protocol type field contains an OSI NLPID.
+ *
+ * PT_IEEE_802_2 means that the protocol type field contains an IEEE 802.2
+ * LLC header that specifies that the payload is for that protocol.
+ */
+#define PT_NLPID		1	/* OSI NLPID */
+#define PT_IEEE_802_2		2	/* IEEE 802.2 LLC header */
+
 static int
 cdp_print_addr(const u_char * p, int l)
 {
-	int pl, al, num;
+	int pt, pl, al, num;
 	const u_char *endp = p + l;
+#ifdef INET6
+	static u_char prot_ipv6[] = {
+		0xaa, 0xaa, 0x03, 0x00, 0x00, 0x00, 0x86, 0xdd
+	};
+#endif
 
-	num = (p[0] << 24) + (p[1] << 16) + (p[2] << 8) + p[3];
+	num = EXTRACT_32BITS(p);
 	p += 4;
 
 	printf(" (%d): ", num);
@@ -156,20 +172,48 @@ cdp_print_addr(const u_char * p, int l)
 	while (p < endp && num >= 0) {
 		if (p + 2 > endp)
 			goto trunc;
-		pl = p[1];
+		pt = p[0];		/* type of "protocol" field */
+		pl = p[1];		/* length of "protocol" field */
 		p += 2;
 
-		/* special case: IPv4, protocol type=0xcc, addr. length=4 */
-		if (p + 3 > endp)
+		if (p + pl + 2 > endp)
 			goto trunc;
-		if (pl == 1 && *p == 0xcc && p[1] == 0 && p[2] == 4) {
+		al = EXTRACT_16BITS(&p[pl]);	/* address length */
+
+		if (pt == PT_NLPID && pl == 1 && *p == 0xcc && al == 4) {
+			/*
+			 * IPv4: protocol type = NLPID, protocol length = 1
+			 * (1-byte NLPID), protocol = 0xcc (NLPID for IPv4),
+			 * address length = 4
+			 */
 			p += 3;
 
 			if (p + 4 > endp)
 				goto trunc;
 			printf("IPv4 %u.%u.%u.%u", p[0], p[1], p[2], p[3]);
 			p += 4;
-		} else {	/* generic case: just print raw data */
+		}
+#ifdef INET6
+		else if (pt == PT_IEEE_802_2 && pl == 8 &&
+		    memcmp(p, prot_ipv6, 8) == 0 && al == 16) {
+			/*
+			 * IPv6: protocol type = IEEE 802.2 header,
+			 * protocol length = 8 (size of LLC+SNAP header),
+			 * protocol = LLC+SNAP header with the IPv6
+			 * Ethertype, address length = 16
+			 */
+			p += 10; 
+			if (p + al > endp)
+				goto trunc;
+
+			printf("IPv6 %s", ip6addr_string(p));
+			p += al;
+		}
+#endif
+		else {
+			/*
+			 * Generic case: just print raw data
+			 */
 			if (p + pl > endp)
 				goto trunc;
 			printf("pt=0x%02x, pl=%d, pb=", *(p - 2), pl);