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Commit 6a63df46 authored by Yuchung Cheng's avatar Yuchung Cheng Committed by David S. Miller
Browse files

tcp: refactor undo functions 



Refactor and relocate various functions or variables to prepare the
undo fix.  Remove some unused function arguments. Rename tcp_undo_cwr
to tcp_undo_cwnd_reduction to be consistent with the rest of
CWR related function names.

Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
Acked-by: default avatarNeal Cardwell <ncardwell@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 6804973f

net/ipv4/tcp_input.c

+50 −47
Original line number Diff line number Diff line
@@ -2243,10 +2243,23 @@ static void DBGUNDO(struct sock *sk, const char *msg) 
#define DBGUNDO(x...) do { } while (0)

#endif



static void tcp_undo_cwr(struct sock *sk, const bool undo_ssthresh)

static void tcp_undo_cwnd_reduction(struct sock *sk, const bool undo_ssthresh,

				    bool unmark_loss)

{

	struct tcp_sock *tp = tcp_sk(sk);



	if (unmark_loss) {

		struct sk_buff *skb;



		tcp_for_write_queue(skb, sk) {

			if (skb == tcp_send_head(sk))

				break;

			TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;

		}

		tp->lost_out = 0;

		tcp_clear_all_retrans_hints(tp);

	}



	if (tp->prior_ssthresh) {

		const struct inet_connection_sock *icsk = inet_csk(sk);
@@ -2263,6 +2276,9 @@ static void tcp_undo_cwr(struct sock *sk, const bool undo_ssthresh) 
		tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);

	}

	tp->snd_cwnd_stamp = tcp_time_stamp;



	if (undo_ssthresh)

		tp->undo_marker = 0;

}



static inline bool tcp_may_undo(const struct tcp_sock *tp)
@@ -2282,14 +2298,13 @@ static bool tcp_try_undo_recovery(struct sock *sk) 
		 * or our original transmission succeeded.

		 */

		DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans");

		tcp_undo_cwr(sk, true);

		tcp_undo_cwnd_reduction(sk, true, false);

		if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss)

			mib_idx = LINUX_MIB_TCPLOSSUNDO;

		else

			mib_idx = LINUX_MIB_TCPFULLUNDO;



		NET_INC_STATS_BH(sock_net(sk), mib_idx);

		tp->undo_marker = 0;

	}

	if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) {

		/* Hold old state until something *above* high_seq
@@ -2309,8 +2324,7 @@ static void tcp_try_undo_dsack(struct sock *sk) 


	if (tp->undo_marker && !tp->undo_retrans) {

		DBGUNDO(sk, "D-SACK");

		tcp_undo_cwr(sk, true);

		tp->undo_marker = 0;

		tcp_undo_cwnd_reduction(sk, true, false);

		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKUNDO);

	}

}
@@ -2344,60 +2358,20 @@ static bool tcp_any_retrans_done(const struct sock *sk) 
	return false;

}



/* Undo during fast recovery after partial ACK. */



static int tcp_try_undo_partial(struct sock *sk, int acked)

{

	struct tcp_sock *tp = tcp_sk(sk);

	/* Partial ACK arrived. Force Hoe's retransmit. */

	int failed = tcp_is_reno(tp) || (tcp_fackets_out(tp) > tp->reordering);



	if (tcp_may_undo(tp)) {

		/* Plain luck! Hole if filled with delayed

		 * packet, rather than with a retransmit.

		 */

		if (!tcp_any_retrans_done(sk))

			tp->retrans_stamp = 0;



		tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1);



		DBGUNDO(sk, "Hoe");

		tcp_undo_cwr(sk, false);

		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPARTIALUNDO);



		/* So... Do not make Hoe's retransmit yet.

		 * If the first packet was delayed, the rest

		 * ones are most probably delayed as well.

		 */

		failed = 0;

	}

	return failed;

}



/* Undo during loss recovery after partial ACK or using F-RTO. */

static bool tcp_try_undo_loss(struct sock *sk, bool frto_undo)

{

	struct tcp_sock *tp = tcp_sk(sk);



	if (frto_undo || tcp_may_undo(tp)) {

		struct sk_buff *skb;

		tcp_for_write_queue(skb, sk) {

			if (skb == tcp_send_head(sk))

				break;

			TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;

		}



		tcp_clear_all_retrans_hints(tp);

		tcp_undo_cwnd_reduction(sk, true, true);



		DBGUNDO(sk, "partial loss");

		tp->lost_out = 0;

		tcp_undo_cwr(sk, true);

		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSSUNDO);

		if (frto_undo)

			NET_INC_STATS_BH(sock_net(sk),

					 LINUX_MIB_TCPSPURIOUSRTOS);

		inet_csk(sk)->icsk_retransmits = 0;

		tp->undo_marker = 0;

		if (frto_undo || tcp_is_sack(tp))

			tcp_set_ca_state(sk, TCP_CA_Open);

		return true;
@@ -2669,6 +2643,35 @@ static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack) 
	tcp_xmit_retransmit_queue(sk);

}



/* Undo during fast recovery after partial ACK. */

static bool tcp_try_undo_partial(struct sock *sk, int acked)

{

	struct tcp_sock *tp = tcp_sk(sk);

	/* Partial ACK arrived. Force Hoe's retransmit. */

	bool failed = tcp_is_reno(tp) || (tcp_fackets_out(tp) > tp->reordering);



	if (tcp_may_undo(tp)) {

		/* Plain luck! Hole if filled with delayed

		 * packet, rather than with a retransmit.

		 */

		if (!tcp_any_retrans_done(sk))

			tp->retrans_stamp = 0;



		tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1);



		DBGUNDO(sk, "Hoe");

		tcp_undo_cwnd_reduction(sk, false, false);

		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPARTIALUNDO);



		/* So... Do not make Hoe's retransmit yet.

		 * If the first packet was delayed, the rest

		 * ones are most probably delayed as well.

		 */

		failed = false;

	}

	return failed;

}



/* Process an event, which can update packets-in-flight not trivially.

 * Main goal of this function is to calculate new estimate for left_out,

 * taking into account both packets sitting in receiver's buffer and
@@ -2686,7 +2689,7 @@ static void tcp_fastretrans_alert(struct sock *sk, const int acked, 
{

	struct inet_connection_sock *icsk = inet_csk(sk);

	struct tcp_sock *tp = tcp_sk(sk);

	int do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) &&

	bool do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) &&

				    (tcp_fackets_out(tp) > tp->reordering));

	int fast_rexmit = 0;