From 1e1d9d6f119c55c05e8ea78ed3e49046690abffd Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Fri, 13 Aug 2021 15:15:43 -0700 Subject: [PATCH] mptcp: handle pending data on closed subflow The PM can close active subflow, e.g. due to ingress RM_ADDR option. Such subflow could carry data still unacked at the MPTCP-level, both in the write and the rtx_queue, which has never reached the other peer. Currently the mptcp-level retransmission will deliver such data, but at a very low rate (at most 1 DSM for each MPTCP rtx interval). We can speed-up the recovery a lot, moving all the unacked in the tcp write_queue, so that it will be pushed again via other subflows, at the speed allowed by them. Also make available the new helper for later patches. Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/207 Signed-off-by: Paolo Abeni Signed-off-by: Mat Martineau Signed-off-by: David S. Miller --- net/mptcp/options.c | 8 +++-- net/mptcp/protocol.c | 76 +++++++++++++++++++++++++++++++++++++++++--- net/mptcp/protocol.h | 6 ++++ 3 files changed, 82 insertions(+), 8 deletions(-) diff --git a/net/mptcp/options.c b/net/mptcp/options.c index 4452455aef7f..e37b6f2fb514 100644 --- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -975,9 +975,11 @@ static void ack_update_msk(struct mptcp_sock *msk, old_snd_una = msk->snd_una; new_snd_una = mptcp_expand_seq(old_snd_una, mp_opt->data_ack, mp_opt->ack64); - /* ACK for data not even sent yet? Ignore. */ - if (after64(new_snd_una, snd_nxt)) - new_snd_una = old_snd_una; + /* ACK for data not even sent yet and even above recovery bound? Ignore.*/ + if (unlikely(after64(new_snd_una, snd_nxt))) { + if (!msk->recovery || after64(new_snd_una, msk->recovery_snd_nxt)) + new_snd_una = old_snd_una; + } new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd; diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index decbb4295ae1..5fafa7a4cd69 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -1055,8 +1055,14 @@ static void __mptcp_clean_una(struct sock *sk) if (after64(dfrag->data_seq + dfrag->data_len, snd_una)) break; - if (WARN_ON_ONCE(dfrag == msk->first_pending)) - break; + if (unlikely(dfrag == msk->first_pending)) { + /* in recovery mode can see ack after the current snd head */ + if (WARN_ON_ONCE(!msk->recovery)) + break; + + WRITE_ONCE(msk->first_pending, mptcp_send_next(sk)); + } + dfrag_clear(sk, dfrag); cleaned = true; } @@ -1065,8 +1071,14 @@ static void __mptcp_clean_una(struct sock *sk) if (dfrag && after64(snd_una, dfrag->data_seq)) { u64 delta = snd_una - dfrag->data_seq; - if (WARN_ON_ONCE(delta > dfrag->already_sent)) - goto out; + /* prevent wrap around in recovery mode */ + if (unlikely(delta > dfrag->already_sent)) { + if (WARN_ON_ONCE(!msk->recovery)) + goto out; + if (WARN_ON_ONCE(delta > dfrag->data_len)) + goto out; + dfrag->already_sent += delta - dfrag->already_sent; + } dfrag->data_seq += delta; dfrag->offset += delta; @@ -1077,6 +1089,10 @@ static void __mptcp_clean_una(struct sock *sk) cleaned = true; } + /* all retransmitted data acked, recovery completed */ + if (unlikely(msk->recovery) && after64(msk->snd_una, msk->recovery_snd_nxt)) + msk->recovery = false; + out: if (cleaned) { if (tcp_under_memory_pressure(sk)) { @@ -1085,7 +1101,7 @@ out: } } - if (snd_una == READ_ONCE(msk->snd_nxt)) { + if (snd_una == READ_ONCE(msk->snd_nxt) && !msk->recovery) { if (mptcp_timer_pending(sk) && !mptcp_data_fin_enabled(msk)) mptcp_stop_timer(sk); } else { @@ -2148,6 +2164,50 @@ static void mptcp_dispose_initial_subflow(struct mptcp_sock *msk) } } +bool __mptcp_retransmit_pending_data(struct sock *sk) +{ + struct mptcp_data_frag *cur, *rtx_head; + struct mptcp_sock *msk = mptcp_sk(sk); + + if (__mptcp_check_fallback(mptcp_sk(sk))) + return false; + + if (tcp_rtx_and_write_queues_empty(sk)) + return false; + + /* the closing socket has some data untransmitted and/or unacked: + * some data in the mptcp rtx queue has not really xmitted yet. + * keep it simple and re-inject the whole mptcp level rtx queue + */ + mptcp_data_lock(sk); + __mptcp_clean_una_wakeup(sk); + rtx_head = mptcp_rtx_head(sk); + if (!rtx_head) { + mptcp_data_unlock(sk); + return false; + } + + /* will accept ack for reijected data before re-sending them */ + if (!msk->recovery || after64(msk->snd_nxt, msk->recovery_snd_nxt)) + msk->recovery_snd_nxt = msk->snd_nxt; + msk->recovery = true; + mptcp_data_unlock(sk); + + msk->first_pending = rtx_head; + msk->tx_pending_data += msk->snd_nxt - rtx_head->data_seq; + msk->snd_nxt = rtx_head->data_seq; + msk->snd_burst = 0; + + /* be sure to clear the "sent status" on all re-injected fragments */ + list_for_each_entry(cur, &msk->rtx_queue, list) { + if (!cur->already_sent) + break; + cur->already_sent = 0; + } + + return true; +} + /* subflow sockets can be either outgoing (connect) or incoming * (accept). * @@ -2160,6 +2220,7 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk, struct mptcp_subflow_context *subflow) { struct mptcp_sock *msk = mptcp_sk(sk); + bool need_push; list_del(&subflow->node); @@ -2171,6 +2232,7 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk, if (ssk->sk_socket) sock_orphan(ssk); + need_push = __mptcp_retransmit_pending_data(sk); subflow->disposable = 1; /* if ssk hit tcp_done(), tcp_cleanup_ulp() cleared the related ops @@ -2198,6 +2260,9 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk, if (msk->subflow && ssk == msk->subflow->sk) mptcp_dispose_initial_subflow(msk); + + if (need_push) + __mptcp_push_pending(sk, 0); } void mptcp_close_ssk(struct sock *sk, struct sock *ssk, @@ -2410,6 +2475,7 @@ static int __mptcp_init_sock(struct sock *sk) msk->first = NULL; inet_csk(sk)->icsk_sync_mss = mptcp_sync_mss; WRITE_ONCE(msk->csum_enabled, mptcp_is_checksum_enabled(sock_net(sk))); + msk->recovery = false; mptcp_pm_data_init(msk); diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 6a3cbdb597e2..6f55784a2efd 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -230,12 +230,17 @@ struct mptcp_sock { struct sock *last_snd; int snd_burst; int old_wspace; + u64 recovery_snd_nxt; /* in recovery mode accept up to this seq; + * recovery related fields are under data_lock + * protection + */ u64 snd_una; u64 wnd_end; unsigned long timer_ival; u32 token; int rmem_released; unsigned long flags; + bool recovery; /* closing subflow write queue reinjected */ bool can_ack; bool fully_established; bool rcv_data_fin; @@ -557,6 +562,7 @@ int mptcp_is_checksum_enabled(struct net *net); int mptcp_allow_join_id0(struct net *net); void mptcp_subflow_fully_established(struct mptcp_subflow_context *subflow, struct mptcp_options_received *mp_opt); +bool __mptcp_retransmit_pending_data(struct sock *sk); bool mptcp_subflow_data_available(struct sock *sk); void __init mptcp_subflow_init(void); void mptcp_subflow_shutdown(struct sock *sk, struct sock *ssk, int how);