From Francois-Xavier Le Bail: suport for the DHCP Classless Static Route

option (RFC 3442).

Just modify the "len" variable as we parse an option - no need for a
separate variable representing the amount of data left (I suspect that's
why the wrong variable appears to have been used in the "trailing data
length" message; I'd expect that message to indicate how much *extra*
data there was in the option, not how much *total* data there was in the
option).

Add checks for too-short options in some cases where they were missing.
In the check for the Client FQDN option, skip past what data there is in
the option if it's too short, so it doesn't show up as extra data in the
option.

For the Agent Circuit option, for each suboption:

	check to make sure the suboption length doesn't go past what's
	left in the option;

	don't reject options with an option type or length of 0 (neither
	are forbidden by RFC 3046, and, in fact, RFC 3046 says "a
	sub-option length may be zero");

	use fn_printn() to print the Agent Circuit ID suboption, rather
	than doing the equivalent ourselves with a safeputchar() loop.

Author: yuguy

bootp.h

@@ -1,4 +1,4 @@
-/* @(#) $Header: /tcpdump/master/tcpdump/bootp.h,v 1.15.4.1 2007-01-29 20:56:00 guy Exp $ (LBL) */
+/* @(#) $Header: /tcpdump/master/tcpdump/bootp.h,v 1.15.4.2 2007-07-24 17:29:43 guy Exp $ (LBL) */
 /*
  * Bootstrap Protocol (BOOTP).  RFC951 and RFC1048.
  *
@@ -161,6 +161,8 @@ struct bootp {
 #define	TAG_NS_SEARCH		((u_int8_t) 117)
 /* RFC 3011 */
 #define	TAG_IP4_SUBNET_SELECT	((u_int8_t) 118)
+/* RFC 3442 */
+#define TAG_CLASSLESS_STATIC_RT	((u_int8_t) 121)
 /* ftp://ftp.isi.edu/.../assignments/bootp-dhcp-extensions */
 #define	TAG_USER_CLASS		((u_int8_t)  77)
 #define	TAG_SLP_NAMING_AUTH	((u_int8_t)  80)