// SPDX-License-Identifier: GPL-2.0
/* MPTCP Fast Open Mechanism
 *
 * Copyright (c) 2021-2022, Dmytro SHYTYI
 */

#include "protocol.h"

void mptcp_fastopen_subflow_synack_set_params(struct mptcp_subflow_context *subflow,
                                              struct request_sock *req)
{
        struct sock *sk, *ssk;
        struct sk_buff *skb;
        struct tcp_sock *tp;
        bool has_rxtstamp;

        /* on early fallback the subflow context is deleted by
         * subflow_syn_recv_sock()
         */
        if (!subflow)
                return;

        ssk = subflow->tcp_sock;
        sk = subflow->conn;
        tp = tcp_sk(ssk);

        subflow->is_mptfo = 1;

        skb = skb_peek(&ssk->sk_receive_queue);
        if (WARN_ON_ONCE(!skb))
                return;

        /* dequeue the skb from sk receive queue */
        __skb_unlink(skb, &ssk->sk_receive_queue);
        skb_ext_reset(skb);

        mptcp_subflow_lend_fwdmem(subflow, skb);

        /* We copy the fastopen data, but that don't belong to the mptcp sequence
         * space, need to offset it in the subflow sequence, see mptcp_subflow_get_map_offset()
         */
        tp->copied_seq += skb->len;
        subflow->ssn_offset += skb->len;
        has_rxtstamp = TCP_SKB_CB(skb)->has_rxtstamp;

        /* 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 = has_rxtstamp;
        MPTCP_SKB_CB(skb)->cant_coalesce = 1;

        mptcp_data_lock(sk);
        DEBUG_NET_WARN_ON_ONCE(sock_owned_by_user_nocheck(sk));

        mptcp_borrow_fwdmem(sk, skb);
        skb_set_owner_r(skb, sk);
        __skb_queue_tail(&sk->sk_receive_queue, skb);
        mptcp_sk(sk)->bytes_received += skb->len;

        sk->sk_data_ready(sk);

        mptcp_data_unlock(sk);
}