Commit 71b7dec2 authored by Paolo Abeni's avatar Paolo Abeni Committed by David S. Miller
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mptcp: less aggressive retransmission strategy 

The current mptcp re-inject strategy is very aggressive,
we have mptcp-level retransmissions even on single subflow
connection, if the link in-use is lossy.

Let's be a little more conservative: we do retransmit
only if at least a subflow has write and rtx queue empty.

Additionally use the backup subflows only if the active
subflows are stale - no progresses in at least an rtx period
and ignore stale subflows for rtx timeout update

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/207


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
Signed-off-by: default avatarMat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 33d41c9c

net/mptcp/pm.c

+17 −0
Original line number Diff line number Diff line
@@ -308,6 +308,23 @@ int mptcp_pm_get_local_id(struct mptcp_sock *msk, struct sock_common *skc) 
	return mptcp_pm_nl_get_local_id(msk, skc);

}



void mptcp_pm_subflow_chk_stale(const struct mptcp_sock *msk, struct sock *ssk)

{

	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);

	u32 rcv_tstamp = READ_ONCE(tcp_sk(ssk)->rcv_tstamp);



	/* keep track of rtx periods with no progress */

	if (!subflow->stale_count) {

		subflow->stale_rcv_tstamp = rcv_tstamp;

		subflow->stale_count++;

	} else if (subflow->stale_rcv_tstamp == rcv_tstamp) {

		if (subflow->stale_count < U8_MAX)

			subflow->stale_count++;

	} else {

		subflow->stale_count = 0;

	}

}



void mptcp_pm_data_init(struct mptcp_sock *msk)

{

	msk->pm.add_addr_signaled = 0;

net/mptcp/protocol.c

+16 −9
Original line number Diff line number Diff line
@@ -420,7 +420,8 @@ static long mptcp_timeout_from_subflow(const struct mptcp_subflow_context *subfl 
{

	const struct sock *ssk = mptcp_subflow_tcp_sock(subflow);



	return inet_csk(ssk)->icsk_pending ? inet_csk(ssk)->icsk_timeout - jiffies : 0;

	return inet_csk(ssk)->icsk_pending && !subflow->stale_count ?

	       inet_csk(ssk)->icsk_timeout - jiffies : 0;

}



static void mptcp_set_timeout(struct sock *sk)
@@ -2100,8 +2101,9 @@ static void mptcp_timeout_timer(struct timer_list *t) 
 */

static struct sock *mptcp_subflow_get_retrans(const struct mptcp_sock *msk)

{

	struct sock *backup = NULL, *pick = NULL;

	struct mptcp_subflow_context *subflow;

	struct sock *backup = NULL;

	int min_stale_count = INT_MAX;



	sock_owned_by_me((const struct sock *)msk);
@@ -2114,11 +2116,11 @@ static struct sock *mptcp_subflow_get_retrans(const struct mptcp_sock *msk) 
		if (!mptcp_subflow_active(subflow))

			continue;



		/* still data outstanding at TCP level?  Don't retransmit. */

		if (!tcp_write_queue_empty(ssk)) {

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

		/* still data outstanding at TCP level? skip this */

		if (!tcp_rtx_and_write_queues_empty(ssk)) {

			mptcp_pm_subflow_chk_stale(msk, ssk);

			min_stale_count = min_t(int, min_stale_count, subflow->stale_count);

			continue;

			return NULL;

		}



		if (subflow->backup) {
@@ -2127,10 +2129,15 @@ static struct sock *mptcp_subflow_get_retrans(const struct mptcp_sock *msk) 
			continue;

		}



		return ssk;

		if (!pick)

			pick = ssk;

	}



	return backup;

	if (pick)

		return pick;



	/* use backup only if there are no progresses anywhere */

	return min_stale_count > 1 ? backup : NULL;

}



static void mptcp_dispose_initial_subflow(struct mptcp_sock *msk)

net/mptcp/protocol.h

+4 −1
Original line number Diff line number Diff line
@@ -439,11 +439,13 @@ struct mptcp_subflow_context { 
	u8	reset_seen:1;

	u8	reset_transient:1;

	u8	reset_reason:4;

	u8	stale_count;



	long	delegated_status;

	struct	list_head delegated_node;   /* link into delegated_action, protected by local BH */



	u32	setsockopt_seq;

	u32	stale_rcv_tstamp;



	struct	sock *tcp_sock;	    /* tcp sk backpointer */

	struct	sock *conn;	    /* parent mptcp_sock */
@@ -690,6 +692,7 @@ void mptcp_crypto_hmac_sha(u64 key1, u64 key2, u8 *msg, int len, void *hmac); 


void __init mptcp_pm_init(void);

void mptcp_pm_data_init(struct mptcp_sock *msk);

void mptcp_pm_subflow_chk_stale(const struct mptcp_sock *msk, struct sock *ssk);

void mptcp_pm_new_connection(struct mptcp_sock *msk, const struct sock *ssk, int server_side);

void mptcp_pm_fully_established(struct mptcp_sock *msk, const struct sock *ssk, gfp_t gfp);

bool mptcp_pm_allow_new_subflow(struct mptcp_sock *msk);