l2tp: Add Last Sent/Received LCP ConfReq in ICCN

To support proxy LCP negotiation.

l2tpns.h

@@ -393,6 +393,9 @@ fragmentationt;
 #define AUTHPAP		1	// allow PAP
 #define AUTHCHAP	2	// allow CHAP
 
+#define MAXLCPLENGTH 128 // Arbitrary, not too large to avoid consuming too
+                         // much memory, but not too short for actual uses
+
 typedef struct
 {
 	// packet counters
@@ -416,6 +419,13 @@ typedef struct
 	// authentication to use
 	int lcp_authtype;
 
+	// Last Received LCP ConfReq and its length
+	uint8_t lcp_last_received_confreq[MAXLCPLENGTH];
+	int lcp_last_received_confreq_n;
+	// Last Sent LCP ConfReq and its length
+	uint8_t lcp_last_sent_confreq[MAXLCPLENGTH];
+	int lcp_last_sent_confreq_n;
+
 	// our MRU
 	uint16_t ppp_mru;