Input buffer for DTLS move to struct conn.

FossilOrigin-Name: 54e254312a0fad891b3c76ea5b8cfdb1284c2cdcb0bc7f71189fc3315dace9dd

src/capwap/conn.h

@@ -101,6 +101,10 @@ struct conn{
 	uint8_t dtls_cookie[8];
 	int dtls_verify_peer;
 
+	uint8_t dtls_buffer[2048];
+	int dtls_buffer_len;
+	int dtls_buffer_pos;
+
 	/* capwap timers */
 	int retransmit_interval;
 	int max_retransmit;