1// SPDX-License-Identifier: GPL-2.0
2/* MPTCP Fast Open Mechanism
3 *
4 * Copyright (c) 2021-2022, Dmytro SHYTYI
5 */
6
7#include "protocol.h"
8
9void mptcp_fastopen_subflow_synack_set_params(struct mptcp_subflow_context *subflow,
10 struct request_sock *req)
11{
12 struct sock *sk, *ssk;
13 struct sk_buff *skb;
14 struct tcp_sock *tp;
15
16 /* on early fallback the subflow context is deleted by
17 * subflow_syn_recv_sock()
18 */
19 if (!subflow)
20 return;
21
22 ssk = subflow->tcp_sock;
23 sk = subflow->conn;
24 tp = tcp_sk(ssk);
25
26 subflow->is_mptfo = 1;
27
28 skb = skb_peek(list_: &ssk->sk_receive_queue);
29 if (WARN_ON_ONCE(!skb))
30 return;
31
32 /* dequeue the skb from sk receive queue */
33 __skb_unlink(skb, list: &ssk->sk_receive_queue);
34 skb_ext_reset(skb);
35
36 mptcp_subflow_lend_fwdmem(subflow, skb);
37
38 /* We copy the fastopen data, but that don't belong to the mptcp sequence
39 * space, need to offset it in the subflow sequence, see mptcp_subflow_get_map_offset()
40 */
41 tp->copied_seq += skb->len;
42 subflow->ssn_offset += skb->len;
43
44 /* Only the sequence delta is relevant */
45 MPTCP_SKB_CB(skb)->map_seq = -skb->len;
46 MPTCP_SKB_CB(skb)->end_seq = 0;
47 MPTCP_SKB_CB(skb)->offset = 0;
48 MPTCP_SKB_CB(skb)->has_rxtstamp = TCP_SKB_CB(skb)->has_rxtstamp;
49 MPTCP_SKB_CB(skb)->cant_coalesce = 1;
50
51 mptcp_data_lock(sk);
52 DEBUG_NET_WARN_ON_ONCE(sock_owned_by_user_nocheck(sk));
53
54 mptcp_borrow_fwdmem(sk, skb);
55 skb_set_owner_r(skb, sk);
56 __skb_queue_tail(list: &sk->sk_receive_queue, newsk: skb);
57 mptcp_sk(sk)->bytes_received += skb->len;
58
59 sk->sk_data_ready(sk);
60
61 mptcp_data_unlock(sk);
62}
63

source code of linux/net/mptcp/fastopen.c