Commit 3541f9e8 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

tcp: add tcp_mss_clamp() helper 



Small cleanup factorizing code doing the TCP_MAXSEG clamping.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ff3edc9b

include/linux/tcp.h

+9 −0
Original line number Diff line number Diff line
@@ -445,4 +445,13 @@ static inline void tcp_saved_syn_free(struct tcp_sock *tp) 


struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk);



static inline u16 tcp_mss_clamp(const struct tcp_sock *tp, u16 mss)

{

	/* We use READ_ONCE() here because socket might not be locked.

	 * This happens for listeners.

	 */

	u16 user_mss = READ_ONCE(tp->rx_opt.user_mss);



	return (user_mss && user_mss < mss) ? user_mss : mss;

}

#endif	/* _LINUX_TCP_H */

net/ipv4/tcp_ipv4.c

+1 −4
Original line number Diff line number Diff line
@@ -1324,10 +1324,7 @@ struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb, 
	tcp_ca_openreq_child(newsk, dst);



	tcp_sync_mss(newsk, dst_mtu(dst));

	newtp->advmss = dst_metric_advmss(dst);

	if (tcp_sk(sk)->rx_opt.user_mss &&

	    tcp_sk(sk)->rx_opt.user_mss < newtp->advmss)

		newtp->advmss = tcp_sk(sk)->rx_opt.user_mss;

	newtp->advmss = tcp_mss_clamp(tcp_sk(sk), dst_metric_advmss(dst));



	tcp_initialize_rcv_mss(newsk);

net/ipv4/tcp_minisocks.c

+2 −5
Original line number Diff line number Diff line
@@ -360,15 +360,12 @@ void tcp_openreq_init_rwin(struct request_sock *req, 
{

	struct inet_request_sock *ireq = inet_rsk(req);

	const struct tcp_sock *tp = tcp_sk(sk_listener);

	u16 user_mss = READ_ONCE(tp->rx_opt.user_mss);

	int full_space = tcp_full_space(sk_listener);

	int mss = dst_metric_advmss(dst);

	u32 window_clamp;

	__u8 rcv_wscale;

	int mss;



	if (user_mss && user_mss < mss)

		mss = user_mss;



	mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));

	window_clamp = READ_ONCE(tp->window_clamp);

	/* Set this up on the first call only */

	req->rsk_window_clamp = window_clamp ? : dst_metric(dst, RTAX_WINDOW);

net/ipv4/tcp_output.c

+4 −10
Original line number Diff line number Diff line
@@ -3062,7 +3062,6 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst, 
	struct sk_buff *skb;

	int tcp_header_size;

	struct tcphdr *th;

	u16 user_mss;

	int mss;



	skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
@@ -3092,10 +3091,7 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst, 
	}

	skb_dst_set(skb, dst);



	mss = dst_metric_advmss(dst);

	user_mss = READ_ONCE(tp->rx_opt.user_mss);

	if (user_mss && user_mss < mss)

		mss = user_mss;

	mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));



	memset(&opts, 0, sizeof(opts));

#ifdef CONFIG_SYN_COOKIES
@@ -3201,9 +3197,7 @@ static void tcp_connect_init(struct sock *sk) 


	if (!tp->window_clamp)

		tp->window_clamp = dst_metric(dst, RTAX_WINDOW);

	tp->advmss = dst_metric_advmss(dst);

	if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->advmss)

		tp->advmss = tp->rx_opt.user_mss;

	tp->advmss = tcp_mss_clamp(tp, dst_metric_advmss(dst));



	tcp_initialize_rcv_mss(sk);
@@ -3280,8 +3274,8 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn) 
	 * user-MSS. Reserve maximum option space for middleboxes that add

	 * private TCP options. The cost is reduced data space in SYN :(

	 */

	if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->rx_opt.mss_clamp)

		tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;

	tp->rx_opt.mss_clamp = tcp_mss_clamp(tp, tp->rx_opt.mss_clamp);



	space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -

		MAX_TCP_OPTION_SPACE;

net/ipv6/tcp_ipv6.c

+1 −4
Original line number Diff line number Diff line
@@ -1147,10 +1147,7 @@ static struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff * 
	tcp_ca_openreq_child(newsk, dst);



	tcp_sync_mss(newsk, dst_mtu(dst));

	newtp->advmss = dst_metric_advmss(dst);

	if (tcp_sk(sk)->rx_opt.user_mss &&

	    tcp_sk(sk)->rx_opt.user_mss < newtp->advmss)

		newtp->advmss = tcp_sk(sk)->rx_opt.user_mss;

	newtp->advmss = tcp_mss_clamp(tcp_sk(sk), dst_metric_advmss(dst));



	tcp_initialize_rcv_mss(newsk);