dccp_send_sync(sk, dp->dccps_gsr);
dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
static inline void dccp_do_pmtu_discovery(struct sock *sk,					  const struct iphdr *iph,					  u32 mtu){	struct dst_entry *dst;	const struct inet_sock *inet = inet_sk(sk);	const struct dccp_sock *dp = dccp_sk(sk);	/* We are not interested in DCCP_LISTEN and request_socks (RESPONSEs	 * send out by Linux are always < 576bytes so they should go through	 * unfragmented).	 */	if (sk->sk_state == DCCP_LISTEN)		return;	/* We don't check in the destentry if pmtu discovery is forbidden	 * on this route. We just assume that no packet_to_big packets	 * are send back when pmtu discovery is not active.     	 * There is a small race when the user changes this flag in the	 * route, but I think that's acceptable.	 */	if ((dst = __sk_dst_check(sk, 0)) == NULL)		return;	dst->ops->update_pmtu(dst, mtu);	/* Something is about to be wrong... Remember soft error	 * for the case, if this connection will not able to recover.	 */	if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))		sk->sk_err_soft = EMSGSIZE;	mtu = dst_mtu(dst);	if (inet->pmtudisc != IP_PMTUDISC_DONT &&	    dp->dccps_pmtu_cookie > mtu) {		dccp_sync_mss(sk, mtu);		/*		 * From: draft-ietf-dccp-spec-11.txt		 *		 *	DCCP-Sync packets are the best choice for upward		 *	probing, since DCCP-Sync probes do not risk application		 *	data loss.		 */		dccp_send_sync(sk, dp->dccps_gsr);	} /* else let the usual retransmit timer handle it */}