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mptcp: less aggressive retransmission strategy

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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: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Paolo Abeni
2021-08-13 15:15:42 -07:00
committed by David S. Miller
parent 33d41c9cd7
commit 71b7dec27f
3 changed files with 37 additions and 10 deletions
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25
net/mptcp/protocol.c
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@@ -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)
continue;
return NULL;
/* 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;
}
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)