[DCCP]: Sample RTT from SYN exchange

Function:
diff --git a/net/dccp/options.c b/net/dccp/options.c
index 9074ca7..14b6212 100644
--- a/net/dccp/options.c
+++ b/net/dccp/options.c
@@ -563,6 +563,14 @@
 	    dccp_insert_options_feat(sk, skb))
 		return -1;
 
+	/*
+	 * Obtain RTT sample from Request/Response exchange.
+	 * This is currently used in CCID 3 initialisation.
+	 */
+	if (DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_REQUEST &&
+	    dccp_insert_option_timestamp(sk, skb))
+		return -1;
+
 	/* XXX: insert other options when appropriate */
 
 	if (DCCP_SKB_CB(skb)->dccpd_opt_len != 0) {