From f03afb3aeb9d81f6c5ab728a61a040012923e3b3 Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Tue, 18 Feb 2025 19:36:13 +0100 Subject: [PATCH] mptcp: drop __mptcp_fastopen_gen_msk_ackseq() When we will move the whole RX path under the msk socket lock, updating the already queued skb for passive fastopen socket at 3rd ack time will be extremely painful and race prone The map_seq for already enqueued skbs is used only to allow correct coalescing with later data; preventing collapsing to the first skb of a fastopen connect we can completely remove the __mptcp_fastopen_gen_msk_ackseq() helper. Before dropping this helper, a new item had to be added to the mptcp_skb_cb structure. Because this item will be frequently tested in the fast path -- almost on every packet -- and because there is free space there, a single byte is used instead of a bitfield. This micro optimisation slightly reduces the number of CPU operations to do the associated check. Signed-off-by: Paolo Abeni Reviewed-by: Matthieu Baerts (NGI0) Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20250218-net-next-mptcp-rx-path-refactor-v1-2-4a47d90d7998@kernel.org Signed-off-by: Jakub Kicinski --- net/mptcp/fastopen.c | 24 ++---------------------- net/mptcp/protocol.c | 4 +++- net/mptcp/protocol.h | 5 ++--- net/mptcp/subflow.c | 3 --- 4 files changed, 7 insertions(+), 29 deletions(-) diff --git a/net/mptcp/fastopen.c b/net/mptcp/fastopen.c index a29ff901df758..7777f5a2d1437 100644 --- a/net/mptcp/fastopen.c +++ b/net/mptcp/fastopen.c @@ -40,13 +40,12 @@ void mptcp_fastopen_subflow_synack_set_params(struct mptcp_subflow_context *subf tp->copied_seq += skb->len; subflow->ssn_offset += skb->len; - /* initialize a dummy sequence number, we will update it at MPC - * completion, if needed - */ + /* Only the sequence delta is relevant */ MPTCP_SKB_CB(skb)->map_seq = -skb->len; MPTCP_SKB_CB(skb)->end_seq = 0; MPTCP_SKB_CB(skb)->offset = 0; MPTCP_SKB_CB(skb)->has_rxtstamp = TCP_SKB_CB(skb)->has_rxtstamp; + MPTCP_SKB_CB(skb)->cant_coalesce = 1; mptcp_data_lock(sk); @@ -58,22 +57,3 @@ void mptcp_fastopen_subflow_synack_set_params(struct mptcp_subflow_context *subf mptcp_data_unlock(sk); } - -void __mptcp_fastopen_gen_msk_ackseq(struct mptcp_sock *msk, struct mptcp_subflow_context *subflow, - const struct mptcp_options_received *mp_opt) -{ - struct sock *sk = (struct sock *)msk; - struct sk_buff *skb; - - skb = skb_peek_tail(&sk->sk_receive_queue); - if (skb) { - WARN_ON_ONCE(MPTCP_SKB_CB(skb)->end_seq); - pr_debug("msk %p moving seq %llx -> %llx end_seq %llx -> %llx\n", sk, - MPTCP_SKB_CB(skb)->map_seq, MPTCP_SKB_CB(skb)->map_seq + msk->ack_seq, - MPTCP_SKB_CB(skb)->end_seq, MPTCP_SKB_CB(skb)->end_seq + msk->ack_seq); - MPTCP_SKB_CB(skb)->map_seq += msk->ack_seq; - MPTCP_SKB_CB(skb)->end_seq += msk->ack_seq; - } - - pr_debug("msk=%p ack_seq=%llx\n", msk, msk->ack_seq); -} diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 6bd8190474706..55f9698f3c22f 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -135,7 +135,8 @@ static bool mptcp_try_coalesce(struct sock *sk, struct sk_buff *to, bool fragstolen; int delta; - if (MPTCP_SKB_CB(from)->offset || + if (unlikely(MPTCP_SKB_CB(to)->cant_coalesce) || + MPTCP_SKB_CB(from)->offset || ((to->len + from->len) > (sk->sk_rcvbuf >> 3)) || !skb_try_coalesce(to, from, &fragstolen, &delta)) return false; @@ -366,6 +367,7 @@ static bool __mptcp_move_skb(struct mptcp_sock *msk, struct sock *ssk, MPTCP_SKB_CB(skb)->end_seq = MPTCP_SKB_CB(skb)->map_seq + copy_len; MPTCP_SKB_CB(skb)->offset = offset; MPTCP_SKB_CB(skb)->has_rxtstamp = has_rxtstamp; + MPTCP_SKB_CB(skb)->cant_coalesce = 0; if (MPTCP_SKB_CB(skb)->map_seq == msk->ack_seq) { /* in sequence */ diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 37226cdd9e371..3c3e9b185ae35 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -129,7 +129,8 @@ struct mptcp_skb_cb { u64 map_seq; u64 end_seq; u32 offset; - u8 has_rxtstamp:1; + u8 has_rxtstamp; + u8 cant_coalesce; }; #define MPTCP_SKB_CB(__skb) ((struct mptcp_skb_cb *)&((__skb)->cb[0])) @@ -1059,8 +1060,6 @@ void mptcp_event_pm_listener(const struct sock *ssk, enum mptcp_event_type event); bool mptcp_userspace_pm_active(const struct mptcp_sock *msk); -void __mptcp_fastopen_gen_msk_ackseq(struct mptcp_sock *msk, struct mptcp_subflow_context *subflow, - const struct mptcp_options_received *mp_opt); void mptcp_fastopen_subflow_synack_set_params(struct mptcp_subflow_context *subflow, struct request_sock *req); int mptcp_nl_fill_addr(struct sk_buff *skb, diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index 2926bdf88e42c..d2caffa56bdd9 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -802,9 +802,6 @@ void __mptcp_subflow_fully_established(struct mptcp_sock *msk, subflow_set_remote_key(msk, subflow, mp_opt); WRITE_ONCE(subflow->fully_established, true); WRITE_ONCE(msk->fully_established, true); - - if (subflow->is_mptfo) - __mptcp_fastopen_gen_msk_ackseq(msk, subflow, mp_opt); } static struct sock *subflow_syn_recv_sock(const struct sock *sk,