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mptcp: Retransmit DATA_FIN
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With this change, the MPTCP-level retransmission timer is used to resend
DATA_FIN. The retranmit timer is not stopped while waiting for a
MPTCP-level ACK of DATA_FIN, and retransmitted DATA_FINs are sent on all
subflows. The retry interval starts at TCP_RTO_MIN and then doubles on
each attempt, up to TCP_RTO_MAX.

Closes: multipath-tcp/mptcp_net-next#146
Fixes: 43b54c6 ("mptcp: Use full MPTCP-level disconnect state machine")
Acked-by: Paolo Abeni <[email protected]>
Signed-off-by: Mat Martineau <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
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mjmartineau authored and davem330 committed Apr 23, 2021
1 parent d13f048 commit 6477dd3
Showing 1 changed file with 23 additions and 2 deletions.
25 changes: 23 additions & 2 deletions net/mptcp/protocol.c
Original file line number Diff line number Diff line change
Expand Up @@ -399,6 +399,14 @@ static bool mptcp_pending_data_fin(struct sock *sk, u64 *seq)
return false;
}

static void mptcp_set_datafin_timeout(const struct sock *sk)
{
struct inet_connection_sock *icsk = inet_csk(sk);

mptcp_sk(sk)->timer_ival = min(TCP_RTO_MAX,
TCP_RTO_MIN << icsk->icsk_retransmits);
}

static void mptcp_set_timeout(const struct sock *sk, const struct sock *ssk)
{
long tout = ssk && inet_csk(ssk)->icsk_pending ?
Expand Down Expand Up @@ -1052,7 +1060,7 @@ static void __mptcp_clean_una(struct sock *sk)
}

if (snd_una == READ_ONCE(msk->snd_nxt)) {
if (msk->timer_ival)
if (msk->timer_ival && !mptcp_data_fin_enabled(msk))
mptcp_stop_timer(sk);
} else {
mptcp_reset_timer(sk);
Expand Down Expand Up @@ -2276,8 +2284,19 @@ static void __mptcp_retrans(struct sock *sk)

__mptcp_clean_una_wakeup(sk);
dfrag = mptcp_rtx_head(sk);
if (!dfrag)
if (!dfrag) {
if (mptcp_data_fin_enabled(msk)) {
struct inet_connection_sock *icsk = inet_csk(sk);

icsk->icsk_retransmits++;
mptcp_set_datafin_timeout(sk);
mptcp_send_ack(msk);

goto reset_timer;
}

return;
}

ssk = mptcp_subflow_get_retrans(msk);
if (!ssk)
Expand Down Expand Up @@ -2460,6 +2479,8 @@ void mptcp_subflow_shutdown(struct sock *sk, struct sock *ssk, int how)
pr_debug("Sending DATA_FIN on subflow %p", ssk);
mptcp_set_timeout(sk, ssk);
tcp_send_ack(ssk);
if (!mptcp_timer_pending(sk))
mptcp_reset_timer(sk);
}
break;
}
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