From 71b7dec27f340c4ab90ef39ae096d8bb2e1c851c Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Fri, 13 Aug 2021 15:15:42 -0700 Subject: 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: Paolo Abeni Signed-off-by: Mat Martineau Signed-off-by: David S. Miller --- net/mptcp/pm.c | 17 +++++++++++++++++ net/mptcp/protocol.c | 25 ++++++++++++++++--------- net/mptcp/protocol.h | 5 ++++- 3 files changed, 37 insertions(+), 10 deletions(-) (limited to 'net/mptcp') diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c index 639271e09604..9ff17c5205ce 100644 --- a/net/mptcp/pm.c +++ b/net/mptcp/pm.c @@ -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; diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 08fa2c73a7e5..decbb4295ae1 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -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) diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 0f0c026c5f8b..6a3cbdb597e2 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -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 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); -- cgit