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Commit c887e6d2 authored by Ilpo Järvinen's avatar Ilpo Järvinen Committed by David S. Miller
Browse files

tcp: consolidate paws check 



Wow, it was quite tricky to merge that stream of negations
but I think I finally got it right:

check & replace_ts_recent:
(s32)(rcv_tsval - ts_recent) >= 0                  => 0
(s32)(ts_recent - rcv_tsval) <= 0                  => 0

discard:
(s32)(ts_recent - rcv_tsval)  > TCP_PAWS_WINDOW    => 1
(s32)(ts_recent - rcv_tsval) <= TCP_PAWS_WINDOW    => 0

I toggled the return values of tcp_paws_check around since
the old encoding added yet-another negation making tracking
of truth-values really complicated.

Signed-off-by: default avatarIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c43d558a

include/net/tcp.h

+14 −4
Original line number Diff line number Diff line
@@ -997,11 +997,21 @@ static inline int tcp_fin_time(const struct sock *sk) 
	return fin_timeout;

}



static inline int tcp_paws_check(const struct tcp_options_received *rx_opt, int rst)

static inline int tcp_paws_check(const struct tcp_options_received *rx_opt,

				 int paws_win)

{

	if ((s32)(rx_opt->rcv_tsval - rx_opt->ts_recent) >= 0)

	if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)

		return 1;

	if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))

		return 1;



	return 0;

	if (get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS)

}



static inline int tcp_paws_reject(const struct tcp_options_received *rx_opt,

				  int rst)

{

	if (tcp_paws_check(rx_opt, 0))

		return 0;



	/* RST segments are not recommended to carry timestamp,

net/ipv4/tcp_input.c

+5 −6
Original line number Diff line number Diff line
@@ -3883,8 +3883,7 @@ static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq) 
		 * Not only, also it occurs for expired timestamps.

		 */



		if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 ||

		   get_seconds() >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS)

		if (tcp_paws_check(&tp->rx_opt, 0))

			tcp_store_ts_recent(tp);

	}

}
@@ -3936,9 +3935,9 @@ static inline int tcp_paws_discard(const struct sock *sk, 
				   const struct sk_buff *skb)

{

	const struct tcp_sock *tp = tcp_sk(sk);

	return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW &&

		get_seconds() < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS &&

		!tcp_disordered_ack(sk, skb));



	return !tcp_paws_check(&tp->rx_opt, TCP_PAWS_WINDOW) &&

	       !tcp_disordered_ack(sk, skb);

}



/* Check segment sequence number for validity.
@@ -5513,7 +5512,7 @@ discard: 


	/* PAWS check. */

	if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp &&

	    tcp_paws_check(&tp->rx_opt, 0))

	    tcp_paws_reject(&tp->rx_opt, 0))

		goto discard_and_undo;



	if (th->syn) {

net/ipv4/tcp_minisocks.c

+2 −2
Original line number Diff line number Diff line
@@ -107,7 +107,7 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb, 
		if (tmp_opt.saw_tstamp) {

			tmp_opt.ts_recent	= tcptw->tw_ts_recent;

			tmp_opt.ts_recent_stamp	= tcptw->tw_ts_recent_stamp;

			paws_reject = tcp_paws_check(&tmp_opt, th->rst);

			paws_reject = tcp_paws_reject(&tmp_opt, th->rst);

		}

	}
@@ -511,7 +511,7 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb, 
			 * from another data.

			 */

			tmp_opt.ts_recent_stamp = get_seconds() - ((TCP_TIMEOUT_INIT/HZ)<<req->retrans);

			paws_reject = tcp_paws_check(&tmp_opt, th->rst);

			paws_reject = tcp_paws_reject(&tmp_opt, th->rst);

		}

	}