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![Dmytro Shytyi](/assets/img/avatar_default.png)
The send_synack() needs to be overridden for MPTCP to support TFO for two reasons: - There is not be enough space in the TCP options if the TFO cookie has to be added in the SYN+ACK with other options: MSS (4), SACK OK (2), Timestamps (10), Window Scale (3+1), TFO (10+2), MP_CAPABLE (12). MPTCPv1 specs -- RFC 8684, section B.1 [1] -- suggest to drop the TCP timestamps option in this case. - The data received in the SYN has to be handled: the SKB can be dequeued from the subflow sk and transferred to the MPTCP sk. Counters need to be updated accordingly and the application can be notified at the end because some bytes have been received. [1] https://www.rfc-editor.org/rfc/rfc8684.html#section-b.1 Co-developed-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: Paolo Abeni <pabeni@redhat.com> Co-developed-by: Matthieu Baerts <matthieu.baerts@tessares.net> Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net> Signed-off-by: Dmytro Shytyi <dmytro@shytyi.net> Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
73 lines
2 KiB
C
73 lines
2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* MPTCP Fast Open Mechanism
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*
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* Copyright (c) 2021-2022, Dmytro SHYTYI
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*/
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#include "protocol.h"
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void mptcp_fastopen_subflow_synack_set_params(struct mptcp_subflow_context *subflow,
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struct request_sock *req)
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{
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struct sock *ssk = subflow->tcp_sock;
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struct sock *sk = subflow->conn;
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struct sk_buff *skb;
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struct tcp_sock *tp;
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tp = tcp_sk(ssk);
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subflow->is_mptfo = 1;
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skb = skb_peek(&ssk->sk_receive_queue);
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if (WARN_ON_ONCE(!skb))
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return;
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/* dequeue the skb from sk receive queue */
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__skb_unlink(skb, &ssk->sk_receive_queue);
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skb_ext_reset(skb);
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skb_orphan(skb);
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/* We copy the fastopen data, but that don't belong to the mptcp sequence
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* space, need to offset it in the subflow sequence, see mptcp_subflow_get_map_offset()
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*/
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tp->copied_seq += skb->len;
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subflow->ssn_offset += skb->len;
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/* initialize a dummy sequence number, we will update it at MPC
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* completion, if needed
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*/
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MPTCP_SKB_CB(skb)->map_seq = -skb->len;
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MPTCP_SKB_CB(skb)->end_seq = 0;
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MPTCP_SKB_CB(skb)->offset = 0;
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MPTCP_SKB_CB(skb)->has_rxtstamp = TCP_SKB_CB(skb)->has_rxtstamp;
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mptcp_data_lock(sk);
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mptcp_set_owner_r(skb, sk);
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__skb_queue_tail(&sk->sk_receive_queue, skb);
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sk->sk_data_ready(sk);
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mptcp_data_unlock(sk);
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}
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void mptcp_fastopen_gen_msk_ackseq(struct mptcp_sock *msk, struct mptcp_subflow_context *subflow,
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const struct mptcp_options_received *mp_opt)
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{
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struct sock *sk = (struct sock *)msk;
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struct sk_buff *skb;
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mptcp_data_lock(sk);
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skb = skb_peek_tail(&sk->sk_receive_queue);
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if (skb) {
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WARN_ON_ONCE(MPTCP_SKB_CB(skb)->end_seq);
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pr_debug("msk %p moving seq %llx -> %llx end_seq %llx -> %llx", sk,
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MPTCP_SKB_CB(skb)->map_seq, MPTCP_SKB_CB(skb)->map_seq + msk->ack_seq,
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MPTCP_SKB_CB(skb)->end_seq, MPTCP_SKB_CB(skb)->end_seq + msk->ack_seq);
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MPTCP_SKB_CB(skb)->map_seq += msk->ack_seq;
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MPTCP_SKB_CB(skb)->end_seq += msk->ack_seq;
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}
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pr_debug("msk=%p ack_seq=%llx", msk, msk->ack_seq);
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mptcp_data_unlock(sk);
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}
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