/* SPDX-License-Identifier: GPL-2.0 */
/* Multipath TCP
 *
 * Copyright (c) 2017 - 2019, Intel Corporation.
 */

#ifndef __MPTCP_PROTOCOL_H
#define __MPTCP_PROTOCOL_H

#include <linux/random.h>
#include <net/tcp.h>
#include <net/inet_connection_sock.h>
#include <uapi/linux/mptcp.h>
#include <net/genetlink.h>
#include <net/rstreason.h>

#define MPTCP_SUPPORTED_VERSION 1

/* MPTCP option bits */
#define OPTION_MPTCP_MPC_SYN    BIT(0)
#define OPTION_MPTCP_MPC_SYNACK BIT(1)
#define OPTION_MPTCP_MPC_ACK    BIT(2)
#define OPTION_MPTCP_MPJ_SYN    BIT(3)
#define OPTION_MPTCP_MPJ_SYNACK BIT(4)
#define OPTION_MPTCP_MPJ_ACK    BIT(5)
#define OPTION_MPTCP_ADD_ADDR   BIT(6)
#define OPTION_MPTCP_RM_ADDR    BIT(7)
#define OPTION_MPTCP_FASTCLOSE  BIT(8)
#define OPTION_MPTCP_PRIO       BIT(9)
#define OPTION_MPTCP_RST        BIT(10)
#define OPTION_MPTCP_DSS        BIT(11)
#define OPTION_MPTCP_FAIL       BIT(12)

#define OPTION_MPTCP_CSUMREQD   BIT(13)

#define OPTIONS_MPTCP_MPC       (OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK | \
                                 OPTION_MPTCP_MPC_ACK)
#define OPTIONS_MPTCP_MPJ       (OPTION_MPTCP_MPJ_SYN | OPTION_MPTCP_MPJ_SYNACK | \
                                 OPTION_MPTCP_MPJ_ACK)

/* MPTCP option subtypes */
#define MPTCPOPT_MP_CAPABLE     0
#define MPTCPOPT_MP_JOIN        1
#define MPTCPOPT_DSS            2
#define MPTCPOPT_ADD_ADDR       3
#define MPTCPOPT_RM_ADDR        4
#define MPTCPOPT_MP_PRIO        5
#define MPTCPOPT_MP_FAIL        6
#define MPTCPOPT_MP_FASTCLOSE   7
#define MPTCPOPT_RST            8

/* MPTCP suboption lengths */
#define TCPOLEN_MPTCP_MPC_SYN           4
#define TCPOLEN_MPTCP_MPC_SYNACK        12
#define TCPOLEN_MPTCP_MPC_ACK           20
#define TCPOLEN_MPTCP_MPC_ACK_DATA      22
#define TCPOLEN_MPTCP_MPJ_SYN           12
#define TCPOLEN_MPTCP_MPJ_SYNACK        16
#define TCPOLEN_MPTCP_MPJ_ACK           24
#define TCPOLEN_MPTCP_DSS_BASE          4
#define TCPOLEN_MPTCP_DSS_ACK32         4
#define TCPOLEN_MPTCP_DSS_ACK64         8
#define TCPOLEN_MPTCP_DSS_MAP32         10
#define TCPOLEN_MPTCP_DSS_MAP64         14
#define TCPOLEN_MPTCP_DSS_CHECKSUM      2
#define TCPOLEN_MPTCP_ADD_ADDR          16
#define TCPOLEN_MPTCP_ADD_ADDR_PORT     18
#define TCPOLEN_MPTCP_ADD_ADDR_BASE     8
#define TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT        10
#define TCPOLEN_MPTCP_ADD_ADDR6         28
#define TCPOLEN_MPTCP_ADD_ADDR6_PORT    30
#define TCPOLEN_MPTCP_ADD_ADDR6_BASE    20
#define TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT       22
#define TCPOLEN_MPTCP_PORT_LEN          2
#define TCPOLEN_MPTCP_PORT_ALIGN        2
#define TCPOLEN_MPTCP_RM_ADDR_BASE      3
#define TCPOLEN_MPTCP_PRIO              3
#define TCPOLEN_MPTCP_PRIO_ALIGN        4
#define TCPOLEN_MPTCP_FASTCLOSE         12
#define TCPOLEN_MPTCP_RST               4
#define TCPOLEN_MPTCP_FAIL              12

#define TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM (TCPOLEN_MPTCP_DSS_CHECKSUM + TCPOLEN_MPTCP_MPC_ACK_DATA)

/* MPTCP MP_JOIN flags */
#define MPTCPOPT_BACKUP         BIT(0)
#define MPTCPOPT_THMAC_LEN      8

/* MPTCP MP_CAPABLE flags */
#define MPTCP_VERSION_MASK      (0x0F)
#define MPTCP_CAP_CHECKSUM_REQD BIT(7)
#define MPTCP_CAP_EXTENSIBILITY BIT(6)
#define MPTCP_CAP_DENY_JOIN_ID0 BIT(5)
#define MPTCP_CAP_HMAC_SHA256   BIT(0)
#define MPTCP_CAP_FLAG_MASK     (0x1F)

/* MPTCP DSS flags */
#define MPTCP_DSS_DATA_FIN      BIT(4)
#define MPTCP_DSS_DSN64         BIT(3)
#define MPTCP_DSS_HAS_MAP       BIT(2)
#define MPTCP_DSS_ACK64         BIT(1)
#define MPTCP_DSS_HAS_ACK       BIT(0)
#define MPTCP_DSS_FLAG_MASK     (0x1F)

/* MPTCP ADD_ADDR flags */
#define MPTCP_ADDR_ECHO         BIT(0)

/* MPTCP MP_PRIO flags */
#define MPTCP_PRIO_BKUP         BIT(0)

/* MPTCP TCPRST flags */
#define MPTCP_RST_TRANSIENT     BIT(0)

/* MPTCP socket atomic flags */
#define MPTCP_WORK_RTX          1
#define MPTCP_FALLBACK_DONE     2
#define MPTCP_WORK_CLOSE_SUBFLOW 3

/* MPTCP socket release cb flags */
#define MPTCP_PUSH_PENDING      1
#define MPTCP_CLEAN_UNA         2
#define MPTCP_ERROR_REPORT      3
#define MPTCP_RETRANSMIT        4
#define MPTCP_FLUSH_JOIN_LIST   5
#define MPTCP_SYNC_STATE        6
#define MPTCP_SYNC_SNDBUF       7

struct mptcp_skb_cb {
        u64 map_seq;
        u64 end_seq;
        u32 offset;
        u8  has_rxtstamp;
        u8  cant_coalesce;
};

#define MPTCP_SKB_CB(__skb)     ((struct mptcp_skb_cb *)&((__skb)->cb[0]))

static inline bool before64(__u64 seq1, __u64 seq2)
{
        return (__s64)(seq1 - seq2) < 0;
}

#define after64(seq2, seq1)     before64(seq1, seq2)

struct mptcp_options_received {
        u64     sndr_key;
        u64     rcvr_key;
        u64     data_ack;
        u64     data_seq;
        u32     subflow_seq;
        u16     data_len;
        __sum16 csum;
        struct_group(status,
                u16 suboptions;
                u16 use_map:1,
                    dsn64:1,
                    data_fin:1,
                    use_ack:1,
                    ack64:1,
                    mpc_map:1,
                    reset_reason:4,
                    reset_transient:1,
                    echo:1,
                    backup:1,
                    deny_join_id0:1,
                    __unused:2;
        );
        u8      join_id;
        u32     token;
        u32     nonce;
        u64     thmac;
        u8      hmac[MPTCPOPT_HMAC_LEN];
        struct mptcp_addr_info addr;
        struct mptcp_rm_list rm_list;
        u64     ahmac;
        u64     fail_seq;
};

static inline __be32 mptcp_option(u8 subopt, u8 len, u8 nib, u8 field)
{
        return htonl((TCPOPT_MPTCP << 24) | (len << 16) | (subopt << 12) |
                     ((nib & 0xF) << 8) | field);
}

enum mptcp_pm_status {
        MPTCP_PM_ADD_ADDR_RECEIVED,
        MPTCP_PM_ADD_ADDR_SEND_ACK,
        MPTCP_PM_RM_ADDR_RECEIVED,
        MPTCP_PM_ESTABLISHED,
        MPTCP_PM_SUBFLOW_ESTABLISHED,
        MPTCP_PM_ALREADY_ESTABLISHED,   /* persistent status, set after ESTABLISHED event */
        MPTCP_PM_MPC_ENDPOINT_ACCOUNTED /* persistent status, set after MPC local address is
                                         * accounted int id_avail_bitmap
                                         */
};

enum mptcp_pm_type {
        MPTCP_PM_TYPE_KERNEL = 0,
        MPTCP_PM_TYPE_USERSPACE,

        __MPTCP_PM_TYPE_NR,
        __MPTCP_PM_TYPE_MAX = __MPTCP_PM_TYPE_NR - 1,
};

/* Status bits below MPTCP_PM_ALREADY_ESTABLISHED need pm worker actions */
#define MPTCP_PM_WORK_MASK ((1 << MPTCP_PM_ALREADY_ESTABLISHED) - 1)

enum mptcp_addr_signal_status {
        MPTCP_ADD_ADDR_SIGNAL,
        MPTCP_ADD_ADDR_ECHO,
        MPTCP_RM_ADDR_SIGNAL,
};

/* max value of mptcp_addr_info.id */
#define MPTCP_PM_MAX_ADDR_ID            U8_MAX

struct mptcp_pm_data {
        struct mptcp_addr_info local;
        struct mptcp_addr_info remote;
        struct list_head anno_list;
        struct list_head userspace_pm_local_addr_list;

        spinlock_t      lock;           /*protects the whole PM data */

        struct_group(reset,

        u8              addr_signal;
        bool            server_side;
        bool            work_pending;
        bool            accept_addr;
        bool            accept_subflow;
        bool            remote_deny_join_id0;
        u8              add_addr_signaled;
        u8              add_addr_accepted;
        u8              local_addr_used;
        u8              pm_type;
        u8              extra_subflows;
        u8              status;

        );

        DECLARE_BITMAP(id_avail_bitmap, MPTCP_PM_MAX_ADDR_ID + 1);
        struct mptcp_rm_list rm_list_tx;
        struct mptcp_rm_list rm_list_rx;
};

struct mptcp_pm_local {
        struct mptcp_addr_info  addr;
        u32                     flags;
        int                     ifindex;
};

struct mptcp_pm_addr_entry {
        struct list_head        list;
        struct mptcp_addr_info  addr;
        u32                     flags;
        int                     ifindex;
        struct socket           *lsk;
};

struct mptcp_data_frag {
        struct list_head list;
        u64 data_seq;
        u16 data_len;
        u16 offset;
        u16 overhead;
        u16 already_sent;
        struct page *page;
};

/* MPTCP connection sock */
struct mptcp_sock {
        /* inet_connection_sock must be the first member */
        struct inet_connection_sock sk;
        u64             local_key;              /* protected by the first subflow socket lock
                                                 * lockless access read
                                                 */
        u64             remote_key;             /* same as above */
        u64             write_seq;
        u64             bytes_sent;
        u64             snd_nxt;
        u64             bytes_received;
        u64             ack_seq;
        atomic64_t      rcv_wnd_sent;
        u64             rcv_data_fin_seq;
        u64             bytes_retrans;
        u64             bytes_consumed;
        int             snd_burst;
        int             old_wspace;
        u64             recovery_snd_nxt;       /* in recovery mode accept up to this seq;
                                                 * recovery related fields are under data_lock
                                                 * protection
                                                 */
        u64             bytes_acked;
        u64             snd_una;
        u64             wnd_end;
        u32             last_data_sent;
        u32             last_data_recv;
        u32             last_ack_recv;
        unsigned long   timer_ival;
        u32             token;
        unsigned long   flags;
        unsigned long   cb_flags;
        bool            recovery;               /* closing subflow write queue reinjected */
        bool            can_ack;
        bool            fully_established;
        bool            rcv_data_fin;
        bool            snd_data_fin_enable;
        bool            rcv_fastclose;
        bool            use_64bit_ack; /* Set when we received a 64-bit DSN */
        bool            csum_enabled;
        bool            allow_infinite_fallback;
        u8              pending_state; /* A subflow asked to set this sk_state,
                                        * protected by the msk data lock
                                        */
        u8              mpc_endpoint_id;
        u8              recvmsg_inq:1,
                        cork:1,
                        nodelay:1,
                        fastopening:1,
                        in_accept_queue:1,
                        free_first:1,
                        rcvspace_init:1,
                        fastclosing:1;
        u32             notsent_lowat;
        int             keepalive_cnt;
        int             keepalive_idle;
        int             keepalive_intvl;
        int             maxseg;
        struct work_struct work;
        struct sk_buff  *ooo_last_skb;
        struct rb_root  out_of_order_queue;
        struct list_head conn_list;
        struct list_head rtx_queue;
        struct mptcp_data_frag *first_pending;
        struct list_head join_list;
        struct sock     *first; /* The mptcp ops can safely dereference, using suitable
                                 * ONCE annotation, the subflow outside the socket
                                 * lock as such sock is freed after close().
                                 */
        struct mptcp_pm_data    pm;
        struct mptcp_sched_ops  *sched;
        struct {
                int     space;  /* bytes copied in last measurement window */
                int     copied; /* bytes copied in this measurement window */
                u64     time;   /* start time of measurement window */
                u64     rtt_us; /* last maximum rtt of subflows */
        } rcvq_space;
        u8              scaling_ratio;
        bool            allow_subflows;

        u32             subflow_id;
        u32             setsockopt_seq;
        char            ca_name[TCP_CA_NAME_MAX];

        spinlock_t      fallback_lock;  /* protects fallback,
                                         * allow_infinite_fallback and
                                         * allow_join
                                         */

        struct list_head backlog_list;  /* protected by the data lock */
        u32             backlog_len;
        u32             backlog_unaccounted;
};

#define mptcp_data_lock(sk) spin_lock_bh(&(sk)->sk_lock.slock)
#define mptcp_data_unlock(sk) spin_unlock_bh(&(sk)->sk_lock.slock)

#define mptcp_for_each_subflow(__msk, __subflow)                        \
        list_for_each_entry(__subflow, &((__msk)->conn_list), node)
#define mptcp_for_each_subflow_safe(__msk, __subflow, __tmp)                    \
        list_for_each_entry_safe(__subflow, __tmp, &((__msk)->conn_list), node)
#define mptcp_next_subflow(__msk, __subflow)                            \
        list_next_entry_circular(__subflow, &((__msk)->conn_list), node)

extern struct genl_family mptcp_genl_family;

static inline void msk_owned_by_me(const struct mptcp_sock *msk)
{
        sock_owned_by_me((const struct sock *)msk);
}

#ifdef CONFIG_DEBUG_NET
/* MPTCP-specific: we might (indirectly) call this helper with the wrong sk */
#undef tcp_sk
#define tcp_sk(ptr) ({                                                          \
        typeof(ptr) _ptr = (ptr);                                               \
        WARN_ON(_ptr->sk_protocol != IPPROTO_TCP);                              \
        container_of_const(_ptr, struct tcp_sock, inet_conn.icsk_inet.sk);      \
})
#define mptcp_sk(ptr) ({                                                \
        typeof(ptr) _ptr = (ptr);                                       \
        WARN_ON(_ptr->sk_protocol != IPPROTO_MPTCP);                    \
        container_of_const(_ptr, struct mptcp_sock, sk.icsk_inet.sk);   \
})

#else /* !CONFIG_DEBUG_NET */
#define mptcp_sk(ptr) container_of_const(ptr, struct mptcp_sock, sk.icsk_inet.sk)
#endif

static inline int mptcp_win_from_space(const struct sock *sk, int space)
{
        return __tcp_win_from_space(mptcp_sk(sk)->scaling_ratio, space);
}

static inline int mptcp_space_from_win(const struct sock *sk, int win)
{
        return __tcp_space_from_win(mptcp_sk(sk)->scaling_ratio, win);
}

static inline int __mptcp_space(const struct sock *sk)
{
        return mptcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf) -
                                    READ_ONCE(mptcp_sk(sk)->backlog_len) -
                                    sk_rmem_alloc_get(sk));
}

static inline struct mptcp_data_frag *mptcp_send_head(const struct sock *sk)
{
        const struct mptcp_sock *msk = mptcp_sk(sk);

        return msk->first_pending;
}

static inline struct mptcp_data_frag *mptcp_send_next(struct sock *sk)
{
        struct mptcp_sock *msk = mptcp_sk(sk);
        struct mptcp_data_frag *cur;

        cur = msk->first_pending;
        return list_is_last(&cur->list, &msk->rtx_queue) ? NULL :
                                                     list_next_entry(cur, list);
}

static inline struct mptcp_data_frag *mptcp_pending_tail(const struct sock *sk)
{
        const struct mptcp_sock *msk = mptcp_sk(sk);

        if (!msk->first_pending)
                return NULL;

        if (WARN_ON_ONCE(list_empty(&msk->rtx_queue)))
                return NULL;

        return list_last_entry(&msk->rtx_queue, struct mptcp_data_frag, list);
}

static inline struct mptcp_data_frag *mptcp_rtx_head(struct sock *sk)
{
        struct mptcp_sock *msk = mptcp_sk(sk);

        if (msk->snd_una == msk->snd_nxt)
                return NULL;

        return list_first_entry_or_null(&msk->rtx_queue, struct mptcp_data_frag, list);
}

struct csum_pseudo_header {
        __be64 data_seq;
        __be32 subflow_seq;
        __be16 data_len;
        __sum16 csum;
};

struct mptcp_subflow_request_sock {
        struct  tcp_request_sock sk;
        u16     mp_capable : 1,
                mp_join : 1,
                backup : 1,
                request_bkup : 1,
                csum_reqd : 1,
                allow_join_id0 : 1;
        u8      local_id;
        u8      remote_id;
        u64     local_key;
        u64     idsn;
        u32     token;
        u32     ssn_offset;
        u64     thmac;
        u32     local_nonce;
        u32     remote_nonce;
        struct mptcp_sock       *msk;
        struct hlist_nulls_node token_node;
};

static inline struct mptcp_subflow_request_sock *
mptcp_subflow_rsk(const struct request_sock *rsk)
{
        return (struct mptcp_subflow_request_sock *)rsk;
}

struct mptcp_delegated_action {
        struct napi_struct napi;
        local_lock_t bh_lock;
        struct list_head head;
};

DECLARE_PER_CPU(struct mptcp_delegated_action, mptcp_delegated_actions);

#define MPTCP_DELEGATE_SCHEDULED        0
#define MPTCP_DELEGATE_SEND             1
#define MPTCP_DELEGATE_ACK              2
#define MPTCP_DELEGATE_SNDBUF           3

#define MPTCP_DELEGATE_ACTIONS_MASK     (~BIT(MPTCP_DELEGATE_SCHEDULED))
/* MPTCP subflow context */
struct mptcp_subflow_context {
        struct  list_head node;/* conn_list of subflows */

        struct_group(reset,

        unsigned long avg_pacing_rate; /* protected by msk socket lock */
        u64     local_key;
        u64     remote_key;
        u64     idsn;
        u64     map_seq;
        u64     rcv_wnd_sent;
        u32     snd_isn;
        u32     token;
        u32     rel_write_seq;
        u32     map_subflow_seq;
        u32     ssn_offset;
        u32     map_data_len;
        __wsum  map_data_csum;
        u32     map_csum_len;
        u32     request_mptcp : 1,  /* send MP_CAPABLE */
                request_join : 1,   /* send MP_JOIN */
                request_bkup : 1,
                mp_capable : 1,     /* remote is MPTCP capable */
                mp_join : 1,        /* remote is JOINing */
                pm_notified : 1,    /* PM hook called for established status */
                conn_finished : 1,
                map_valid : 1,
                map_csum_reqd : 1,
                map_data_fin : 1,
                mpc_map : 1,
                backup : 1,
                send_mp_prio : 1,
                send_mp_fail : 1,
                send_fastclose : 1,
                send_infinite_map : 1,
                remote_key_valid : 1,        /* received the peer key from */
                disposable : 1,     /* ctx can be free at ulp release time */
                closing : 1,        /* must not pass rx data to msk anymore */
                stale : 1,          /* unable to snd/rcv data, do not use for xmit */
                valid_csum_seen : 1,        /* at least one csum validated */
                is_mptfo : 1,       /* subflow is doing TFO */
                close_event_done : 1,       /* has done the post-closed part */
                mpc_drop : 1,       /* the MPC option has been dropped in a rtx */
                __unused : 8;
        bool    data_avail;
        bool    scheduled;
        bool    pm_listener;        /* a listener managed by the kernel PM? */
        bool    fully_established;  /* path validated */
        u32     lent_mem_frag;
        u32     remote_nonce;
        u64     thmac;
        u32     local_nonce;
        u32     remote_token;
        union {
                u8      hmac[MPTCPOPT_HMAC_LEN]; /* MPJ subflow only */
                u64     iasn;       /* initial ack sequence number, MPC subflows only */
        };
        s16     local_id;           /* if negative not initialized yet */
        u8      remote_id;
        u8      reset_seen:1;
        u8      reset_transient:1;
        u8      reset_reason:4;
        u8      stale_count;

        u32     subflow_id;

        long    delegated_status;
        unsigned long   fail_tout;

        );

        struct  list_head delegated_node;   /* link into delegated_action, protected by local BH */

        u32     setsockopt_seq;
        u32     stale_rcv_tstamp;
        int     cached_sndbuf;      /* sndbuf size when last synced with the msk sndbuf,
                                     * protected by the msk socket lock
                                     */

        struct  sock *tcp_sock;     /* tcp sk backpointer */
        struct  sock *conn;         /* parent mptcp_sock */
        const   struct inet_connection_sock_af_ops *icsk_af_ops;
        void    (*tcp_state_change)(struct sock *sk);
        void    (*tcp_error_report)(struct sock *sk);

        struct  rcu_head rcu;
};

static inline struct mptcp_subflow_context *
mptcp_subflow_ctx(const struct sock *sk)
{
        const struct inet_connection_sock *icsk = inet_csk(sk);

        /* Use RCU on icsk_ulp_data only for sock diag code */
        return (__force struct mptcp_subflow_context *)icsk->icsk_ulp_data;
}

static inline struct sock *
mptcp_subflow_tcp_sock(const struct mptcp_subflow_context *subflow)
{
        return subflow->tcp_sock;
}

static inline void
mptcp_subflow_ctx_reset(struct mptcp_subflow_context *subflow)
{
        memset(&subflow->reset, 0, sizeof(subflow->reset));
        subflow->request_mptcp = 1;
        WRITE_ONCE(subflow->local_id, -1);
}

/* Convert reset reasons in MPTCP to enum sk_rst_reason type */
static inline enum sk_rst_reason
sk_rst_convert_mptcp_reason(u32 reason)
{
        switch (reason) {
        case MPTCP_RST_EUNSPEC:
                return SK_RST_REASON_MPTCP_RST_EUNSPEC;
        case MPTCP_RST_EMPTCP:
                return SK_RST_REASON_MPTCP_RST_EMPTCP;
        case MPTCP_RST_ERESOURCE:
                return SK_RST_REASON_MPTCP_RST_ERESOURCE;
        case MPTCP_RST_EPROHIBIT:
                return SK_RST_REASON_MPTCP_RST_EPROHIBIT;
        case MPTCP_RST_EWQ2BIG:
                return SK_RST_REASON_MPTCP_RST_EWQ2BIG;
        case MPTCP_RST_EBADPERF:
                return SK_RST_REASON_MPTCP_RST_EBADPERF;
        case MPTCP_RST_EMIDDLEBOX:
                return SK_RST_REASON_MPTCP_RST_EMIDDLEBOX;
        default:
                /* It should not happen, or else errors may occur
                 * in MPTCP layer
                 */
                return SK_RST_REASON_ERROR;
        }
}

static inline void
mptcp_send_active_reset_reason(struct sock *sk)
{
        struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
        enum sk_rst_reason reason;

        reason = sk_rst_convert_mptcp_reason(subflow->reset_reason);
        tcp_send_active_reset(sk, GFP_ATOMIC, reason);
}

/* Made the fwd mem carried by the given skb available to the msk,
 * To be paired with a previous mptcp_subflow_lend_fwdmem() before freeing
 * the skb or setting the skb ownership.
 */
static inline void mptcp_borrow_fwdmem(struct sock *sk, struct sk_buff *skb)
{
        struct sock *ssk = skb->sk;

        /* The subflow just lend the skb fwd memory; if the subflow meanwhile
         * closed, mptcp_close_ssk() already released the ssk rcv memory.
         */
        DEBUG_NET_WARN_ON_ONCE(skb->destructor);
        sk_forward_alloc_add(sk, skb->truesize);
        if (!ssk)
                return;

        atomic_sub(skb->truesize, &ssk->sk_rmem_alloc);
        skb->sk = NULL;
}

static inline void
__mptcp_subflow_lend_fwdmem(struct mptcp_subflow_context *subflow, int size)
{
        int frag = (subflow->lent_mem_frag + size) & (PAGE_SIZE - 1);

        subflow->lent_mem_frag = frag;
}

static inline void
mptcp_subflow_lend_fwdmem(struct mptcp_subflow_context *subflow,
                          struct sk_buff *skb)
{
        __mptcp_subflow_lend_fwdmem(subflow, skb->truesize);
        skb->destructor = NULL;
}

static inline u64
mptcp_subflow_get_map_offset(const struct mptcp_subflow_context *subflow)
{
        return tcp_sk(mptcp_subflow_tcp_sock(subflow))->copied_seq -
                      subflow->ssn_offset -
                      subflow->map_subflow_seq;
}

static inline u64
mptcp_subflow_get_mapped_dsn(const struct mptcp_subflow_context *subflow)
{
        return subflow->map_seq + mptcp_subflow_get_map_offset(subflow);
}

void mptcp_subflow_process_delegated(struct sock *ssk, long actions);

static inline void mptcp_subflow_delegate(struct mptcp_subflow_context *subflow, int action)
{
        long old, set_bits = BIT(MPTCP_DELEGATE_SCHEDULED) | BIT(action);
        struct mptcp_delegated_action *delegated;
        bool schedule;

        /* the caller held the subflow bh socket lock */
        lockdep_assert_in_softirq();

        /* The implied barrier pairs with tcp_release_cb_override()
         * mptcp_napi_poll(), and ensures the below list check sees list
         * updates done prior to delegated status bits changes
         */
        old = set_mask_bits(&subflow->delegated_status, 0, set_bits);
        if (!(old & BIT(MPTCP_DELEGATE_SCHEDULED))) {
                if (WARN_ON_ONCE(!list_empty(&subflow->delegated_node)))
                        return;

                local_lock_nested_bh(&mptcp_delegated_actions.bh_lock);
                delegated = this_cpu_ptr(&mptcp_delegated_actions);
                schedule = list_empty(&delegated->head);
                list_add_tail(&subflow->delegated_node, &delegated->head);
                local_unlock_nested_bh(&mptcp_delegated_actions.bh_lock);
                sock_hold(mptcp_subflow_tcp_sock(subflow));
                if (schedule)
                        napi_schedule(&delegated->napi);
        }
}

static inline struct mptcp_subflow_context *
mptcp_subflow_delegated_next(struct mptcp_delegated_action *delegated)
{
        struct mptcp_subflow_context *ret;

        local_lock_nested_bh(&mptcp_delegated_actions.bh_lock);
        if (list_empty(&delegated->head)) {
                local_unlock_nested_bh(&mptcp_delegated_actions.bh_lock);
                return NULL;
        }

        ret = list_first_entry(&delegated->head, struct mptcp_subflow_context, delegated_node);
        list_del_init(&ret->delegated_node);
        local_unlock_nested_bh(&mptcp_delegated_actions.bh_lock);
        return ret;
}

void __mptcp_inherit_memcg(struct sock *sk, struct sock *ssk, gfp_t gfp);
void __mptcp_inherit_cgrp_data(struct sock *sk, struct sock *ssk);

int mptcp_is_enabled(const struct net *net);
unsigned int mptcp_get_add_addr_timeout(const struct net *net);
int mptcp_is_checksum_enabled(const struct net *net);
int mptcp_allow_join_id0(const struct net *net);
unsigned int mptcp_stale_loss_cnt(const struct net *net);
unsigned int mptcp_close_timeout(const struct sock *sk);
int mptcp_get_pm_type(const struct net *net);
const char *mptcp_get_path_manager(const struct net *net);
const char *mptcp_get_scheduler(const struct net *net);

void mptcp_active_disable(struct sock *sk);
bool mptcp_active_should_disable(struct sock *ssk);
void mptcp_active_enable(struct sock *sk);

void mptcp_get_available_schedulers(char *buf, size_t maxlen);
void __mptcp_subflow_fully_established(struct mptcp_sock *msk,
                                       struct mptcp_subflow_context *subflow,
                                       const struct mptcp_options_received *mp_opt);
bool __mptcp_retransmit_pending_data(struct sock *sk);
void mptcp_check_and_set_pending(struct sock *sk);
void __mptcp_push_pending(struct sock *sk, unsigned int flags);
bool mptcp_subflow_data_available(struct sock *sk);
void __init mptcp_subflow_init(void);
void mptcp_subflow_shutdown(struct sock *sk, struct sock *ssk, int how);
void mptcp_close_ssk(struct sock *sk, struct sock *ssk,
                     struct mptcp_subflow_context *subflow);
void __mptcp_subflow_send_ack(struct sock *ssk);
void mptcp_subflow_reset(struct sock *ssk);
void mptcp_subflow_queue_clean(struct sock *sk, struct sock *ssk);
void mptcp_sock_graft(struct sock *sk, struct socket *parent);
struct sock *__mptcp_nmpc_sk(struct mptcp_sock *msk);
bool __mptcp_close(struct sock *sk, long timeout);
void mptcp_cancel_work(struct sock *sk);
void __mptcp_unaccepted_force_close(struct sock *sk);
void mptcp_set_state(struct sock *sk, int state);

bool mptcp_addresses_equal(const struct mptcp_addr_info *a,
                           const struct mptcp_addr_info *b, bool use_port);
void mptcp_local_address(const struct sock_common *skc,
                         struct mptcp_addr_info *addr);
void mptcp_remote_address(const struct sock_common *skc,
                          struct mptcp_addr_info *addr);

/* called with sk socket lock held */
int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_pm_local *local,
                            const struct mptcp_addr_info *remote);
int mptcp_subflow_create_socket(struct sock *sk, unsigned short family,
                                struct socket **new_sock);
void mptcp_info2sockaddr(const struct mptcp_addr_info *info,
                         struct sockaddr_storage *addr,
                         unsigned short family);
struct mptcp_sched_ops *mptcp_sched_find(const char *name);
int mptcp_validate_scheduler(struct mptcp_sched_ops *sched);
int mptcp_register_scheduler(struct mptcp_sched_ops *sched);
void mptcp_unregister_scheduler(struct mptcp_sched_ops *sched);
void mptcp_sched_init(void);
int mptcp_init_sched(struct mptcp_sock *msk,
                     struct mptcp_sched_ops *sched);
void mptcp_release_sched(struct mptcp_sock *msk);
void mptcp_subflow_set_scheduled(struct mptcp_subflow_context *subflow,
                                 bool scheduled);
struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk);
struct sock *mptcp_subflow_get_retrans(struct mptcp_sock *msk);
int mptcp_sched_get_send(struct mptcp_sock *msk);
int mptcp_sched_get_retrans(struct mptcp_sock *msk);

static inline u64 mptcp_data_avail(const struct mptcp_sock *msk)
{
        return READ_ONCE(msk->bytes_received) - READ_ONCE(msk->bytes_consumed);
}

static inline bool mptcp_epollin_ready(const struct sock *sk)
{
        u64 data_avail = mptcp_data_avail(mptcp_sk(sk));

        if (!data_avail)
                return false;

        /* mptcp doesn't have to deal with small skbs in the receive queue,
         * as it can always coalesce them
         */
        return (data_avail >= sk->sk_rcvlowat) ||
                tcp_under_memory_pressure(sk);
}

int mptcp_set_rcvlowat(struct sock *sk, int val);

static inline bool __tcp_can_send(const struct sock *ssk)
{
        /* only send if our side has not closed yet */
        return ((1 << inet_sk_state_load(ssk)) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT));
}

static inline bool __mptcp_subflow_active(struct mptcp_subflow_context *subflow)
{
        /* can't send if JOIN hasn't completed yet (i.e. is usable for mptcp) */
        if (subflow->request_join && !READ_ONCE(subflow->fully_established))
                return false;

        return __tcp_can_send(mptcp_subflow_tcp_sock(subflow));
}

void mptcp_subflow_set_active(struct mptcp_subflow_context *subflow);

bool mptcp_subflow_active(struct mptcp_subflow_context *subflow);

void mptcp_subflow_drop_ctx(struct sock *ssk);

static inline void mptcp_subflow_tcp_fallback(struct sock *sk,
                                              struct mptcp_subflow_context *ctx)
{
        sk->sk_data_ready = sock_def_readable;
        sk->sk_state_change = ctx->tcp_state_change;
        sk->sk_write_space = sk_stream_write_space;
        sk->sk_error_report = ctx->tcp_error_report;

        inet_csk(sk)->icsk_af_ops = ctx->icsk_af_ops;
}

void __init mptcp_proto_init(void);
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
int __init mptcp_proto_v6_init(void);
#endif

struct sock *mptcp_sk_clone_init(const struct sock *sk,
                                 const struct mptcp_options_received *mp_opt,
                                 struct sock *ssk,
                                 struct request_sock *req);
void mptcp_get_options(const struct sk_buff *skb,
                       struct mptcp_options_received *mp_opt);

void mptcp_finish_connect(struct sock *sk);
void __mptcp_sync_state(struct sock *sk, int state);
void mptcp_reset_tout_timer(struct mptcp_sock *msk, unsigned long fail_tout);

static inline void mptcp_stop_tout_timer(struct sock *sk)
{
        if (!inet_csk(sk)->icsk_mtup.probe_timestamp)
                return;

        sk_stop_timer(sk, &inet_csk(sk)->mptcp_tout_timer);
        inet_csk(sk)->icsk_mtup.probe_timestamp = 0;
}

static inline void mptcp_set_close_tout(struct sock *sk, unsigned long tout)
{
        /* avoid 0 timestamp, as that means no close timeout */
        inet_csk(sk)->icsk_mtup.probe_timestamp = tout ? : 1;
}

static inline void mptcp_start_tout_timer(struct sock *sk)
{
        mptcp_set_close_tout(sk, tcp_jiffies32);
        mptcp_reset_tout_timer(mptcp_sk(sk), 0);
}

static inline bool mptcp_is_fully_established(struct sock *sk)
{
        return inet_sk_state_load(sk) == TCP_ESTABLISHED &&
               READ_ONCE(mptcp_sk(sk)->fully_established);
}

static inline u64 mptcp_stamp(void)
{
        return div_u64(tcp_clock_ns(), NSEC_PER_USEC);
}

void mptcp_data_ready(struct sock *sk, struct sock *ssk);
bool mptcp_finish_join(struct sock *sk);
bool mptcp_schedule_work(struct sock *sk);
int mptcp_setsockopt(struct sock *sk, int level, int optname,
                     sockptr_t optval, unsigned int optlen);
int mptcp_getsockopt(struct sock *sk, int level, int optname,
                     char __user *optval, int __user *option);

u64 __mptcp_expand_seq(u64 old_seq, u64 cur_seq);
static inline u64 mptcp_expand_seq(u64 old_seq, u64 cur_seq, bool use_64bit)
{
        if (use_64bit)
                return cur_seq;

        return __mptcp_expand_seq(old_seq, cur_seq);
}
void __mptcp_check_push(struct sock *sk, struct sock *ssk);
void __mptcp_data_acked(struct sock *sk);
void __mptcp_error_report(struct sock *sk);
bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit);
static inline bool mptcp_data_fin_enabled(const struct mptcp_sock *msk)
{
        return READ_ONCE(msk->snd_data_fin_enable) &&
               READ_ONCE(msk->write_seq) == READ_ONCE(msk->snd_nxt);
}

static inline u32 mptcp_notsent_lowat(const struct sock *sk)
{
        struct net *net = sock_net(sk);
        u32 val;

        val = READ_ONCE(mptcp_sk(sk)->notsent_lowat);
        return val ?: READ_ONCE(net->ipv4.sysctl_tcp_notsent_lowat);
}

static inline bool mptcp_stream_memory_free(const struct sock *sk, int wake)
{
        const struct mptcp_sock *msk = mptcp_sk(sk);
        u32 notsent_bytes;

        notsent_bytes = READ_ONCE(msk->write_seq) - READ_ONCE(msk->snd_nxt);
        return (notsent_bytes << wake) < mptcp_notsent_lowat(sk);
}

static inline bool __mptcp_stream_is_writeable(const struct sock *sk, int wake)
{
        return mptcp_stream_memory_free(sk, wake) &&
               __sk_stream_is_writeable(sk, wake);
}

static inline void mptcp_write_space(struct sock *sk)
{
        /* pairs with memory barrier in mptcp_poll */
        smp_mb();
        if (mptcp_stream_memory_free(sk, 1))
                INDIRECT_CALL_1(sk->sk_write_space, sk_stream_write_space, sk);
}

static inline void __mptcp_sync_sndbuf(struct sock *sk)
{
        struct mptcp_subflow_context *subflow;
        int ssk_sndbuf, new_sndbuf;

        if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
                return;

        new_sndbuf = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_wmem[0]);
        mptcp_for_each_subflow(mptcp_sk(sk), subflow) {
                ssk_sndbuf =  READ_ONCE(mptcp_subflow_tcp_sock(subflow)->sk_sndbuf);

                subflow->cached_sndbuf = ssk_sndbuf;
                new_sndbuf += ssk_sndbuf;
        }

        /* the msk max wmem limit is <nr_subflows> * tcp wmem[2] */
        WRITE_ONCE(sk->sk_sndbuf, new_sndbuf);
        mptcp_write_space(sk);
}

/* The called held both the msk socket and the subflow socket locks,
 * possibly under BH
 */
static inline void __mptcp_propagate_sndbuf(struct sock *sk, struct sock *ssk)
{
        struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);

        if (READ_ONCE(ssk->sk_sndbuf) != subflow->cached_sndbuf)
                __mptcp_sync_sndbuf(sk);
}

/* the caller held only the subflow socket lock, either in process or
 * BH context. Additionally this can be called under the msk data lock,
 * so we can't acquire such lock here: let the delegate action acquires
 * the needed locks in suitable order.
 */
static inline void mptcp_propagate_sndbuf(struct sock *sk, struct sock *ssk)
{
        struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);

        if (likely(READ_ONCE(ssk->sk_sndbuf) == subflow->cached_sndbuf))
                return;

        local_bh_disable();
        mptcp_subflow_delegate(subflow, MPTCP_DELEGATE_SNDBUF);
        local_bh_enable();
}

#define MPTCP_TOKEN_MAX_RETRIES 4

void __init mptcp_token_init(void);
static inline void mptcp_token_init_request(struct request_sock *req)
{
        mptcp_subflow_rsk(req)->token_node.pprev = NULL;
}

int mptcp_token_new_request(struct request_sock *req);
void mptcp_token_destroy_request(struct request_sock *req);
int mptcp_token_new_connect(struct sock *ssk);
void mptcp_token_accept(struct mptcp_subflow_request_sock *r,
                        struct mptcp_sock *msk);
bool mptcp_token_exists(u32 token);
struct mptcp_sock *mptcp_token_get_sock(struct net *net, u32 token);
struct mptcp_sock *mptcp_token_iter_next(const struct net *net, long *s_slot,
                                         long *s_num);
void mptcp_token_destroy(struct mptcp_sock *msk);

void mptcp_crypto_key_sha(u64 key, u32 *token, u64 *idsn);

void mptcp_crypto_hmac_sha(u64 key1, u64 key2, u8 *msg, int len, void *hmac);
__sum16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum);

void __init mptcp_pm_init(void);
void mptcp_pm_data_init(struct mptcp_sock *msk);
void mptcp_pm_data_reset(struct mptcp_sock *msk);
void mptcp_pm_destroy(struct mptcp_sock *msk);
int mptcp_pm_parse_addr(struct nlattr *attr, struct genl_info *info,
                        struct mptcp_addr_info *addr);
int mptcp_pm_parse_entry(struct nlattr *attr, struct genl_info *info,
                         bool require_family,
                         struct mptcp_pm_addr_entry *entry);
bool mptcp_pm_addr_families_match(const struct sock *sk,
                                  const struct mptcp_addr_info *loc,
                                  const struct mptcp_addr_info *rem);
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);
bool mptcp_pm_allow_new_subflow(struct mptcp_sock *msk);
void mptcp_pm_connection_closed(struct mptcp_sock *msk);
void mptcp_pm_subflow_established(struct mptcp_sock *msk);
bool mptcp_pm_nl_check_work_pending(struct mptcp_sock *msk);
void mptcp_pm_subflow_check_next(struct mptcp_sock *msk,
                                 const struct mptcp_subflow_context *subflow);
void mptcp_pm_add_addr_received(const struct sock *ssk,
                                const struct mptcp_addr_info *addr);
void mptcp_pm_add_addr_echoed(struct mptcp_sock *msk,
                              const struct mptcp_addr_info *addr);
void mptcp_pm_add_addr_send_ack(struct mptcp_sock *msk);
void mptcp_pm_send_ack(struct mptcp_sock *msk,
                       struct mptcp_subflow_context *subflow,
                       bool prio, bool backup);
void mptcp_pm_addr_send_ack(struct mptcp_sock *msk);
void mptcp_pm_nl_rm_addr(struct mptcp_sock *msk, u8 rm_id);
void mptcp_pm_rm_subflow(struct mptcp_sock *msk,
                         const struct mptcp_rm_list *rm_list);
void mptcp_pm_rm_addr_received(struct mptcp_sock *msk,
                               const struct mptcp_rm_list *rm_list);
void mptcp_pm_mp_prio_received(struct sock *sk, u8 bkup);
void mptcp_pm_mp_fail_received(struct sock *sk, u64 fail_seq);
int mptcp_pm_mp_prio_send_ack(struct mptcp_sock *msk,
                              struct mptcp_addr_info *addr,
                              struct mptcp_addr_info *rem,
                              u8 bkup);
bool mptcp_pm_alloc_anno_list(struct mptcp_sock *msk,
                              const struct mptcp_addr_info *addr);
bool mptcp_pm_sport_in_anno_list(struct mptcp_sock *msk, const struct sock *sk);
struct mptcp_pm_add_entry *
mptcp_pm_del_add_timer(struct mptcp_sock *msk,
                       const struct mptcp_addr_info *addr, bool check_id);
bool mptcp_lookup_subflow_by_saddr(const struct list_head *list,
                                   const struct mptcp_addr_info *saddr);
bool mptcp_remove_anno_list_by_saddr(struct mptcp_sock *msk,
                                     const struct mptcp_addr_info *addr);
int mptcp_pm_nl_set_flags(struct mptcp_pm_addr_entry *local,
                          struct genl_info *info);
int mptcp_userspace_pm_set_flags(struct mptcp_pm_addr_entry *local,
                                 struct genl_info *info);
int mptcp_pm_announce_addr(struct mptcp_sock *msk,
                           const struct mptcp_addr_info *addr,
                           bool echo);
int mptcp_pm_remove_addr(struct mptcp_sock *msk, const struct mptcp_rm_list *rm_list);
void mptcp_pm_remove_addr_entry(struct mptcp_sock *msk,
                                struct mptcp_pm_addr_entry *entry);

/* the default path manager, used in mptcp_pm_unregister */
extern struct mptcp_pm_ops mptcp_pm_kernel;

struct mptcp_pm_ops *mptcp_pm_find(const char *name);
int mptcp_pm_register(struct mptcp_pm_ops *pm_ops);
void mptcp_pm_unregister(struct mptcp_pm_ops *pm_ops);
int mptcp_pm_validate(struct mptcp_pm_ops *pm_ops);
void mptcp_pm_get_available(char *buf, size_t maxlen);

void mptcp_userspace_pm_free_local_addr_list(struct mptcp_sock *msk);

void mptcp_event(enum mptcp_event_type type, const struct mptcp_sock *msk,
                 const struct sock *ssk, gfp_t gfp);
void mptcp_event_addr_announced(const struct sock *ssk, const struct mptcp_addr_info *info);
void mptcp_event_addr_removed(const struct mptcp_sock *msk, u8 id);
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_subflow_synack_set_params(struct mptcp_subflow_context *subflow,
                                              struct request_sock *req);
int mptcp_pm_genl_fill_addr(struct sk_buff *msg,
                            struct netlink_callback *cb,
                            struct mptcp_pm_addr_entry *entry);

static inline bool mptcp_pm_should_add_signal(struct mptcp_sock *msk)
{
        return READ_ONCE(msk->pm.addr_signal) &
                (BIT(MPTCP_ADD_ADDR_SIGNAL) | BIT(MPTCP_ADD_ADDR_ECHO));
}

static inline bool mptcp_pm_should_add_signal_addr(struct mptcp_sock *msk)
{
        return READ_ONCE(msk->pm.addr_signal) & BIT(MPTCP_ADD_ADDR_SIGNAL);
}

static inline bool mptcp_pm_should_add_signal_echo(struct mptcp_sock *msk)
{
        return READ_ONCE(msk->pm.addr_signal) & BIT(MPTCP_ADD_ADDR_ECHO);
}

static inline bool mptcp_pm_should_rm_signal(struct mptcp_sock *msk)
{
        return READ_ONCE(msk->pm.addr_signal) & BIT(MPTCP_RM_ADDR_SIGNAL);
}

static inline bool mptcp_pm_is_userspace(const struct mptcp_sock *msk)
{
        return READ_ONCE(msk->pm.pm_type) == MPTCP_PM_TYPE_USERSPACE;
}

static inline bool mptcp_pm_is_kernel(const struct mptcp_sock *msk)
{
        return READ_ONCE(msk->pm.pm_type) == MPTCP_PM_TYPE_KERNEL;
}

static inline unsigned int mptcp_add_addr_len(int family, bool echo, bool port)
{
        u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;

        if (family == AF_INET6)
                len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
        if (!echo)
                len += MPTCPOPT_THMAC_LEN;
        /* account for 2 trailing 'nop' options */
        if (port)
                len += TCPOLEN_MPTCP_PORT_LEN + TCPOLEN_MPTCP_PORT_ALIGN;

        return len;
}

static inline int mptcp_rm_addr_len(const struct mptcp_rm_list *rm_list)
{
        if (rm_list->nr == 0 || rm_list->nr > MPTCP_RM_IDS_MAX)
                return -EINVAL;

        return TCPOLEN_MPTCP_RM_ADDR_BASE + roundup(rm_list->nr - 1, 4) + 1;
}

bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, const struct sk_buff *skb,
                              unsigned int opt_size, unsigned int remaining,
                              struct mptcp_addr_info *addr, bool *echo,
                              bool *drop_other_suboptions);
bool mptcp_pm_rm_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
                             struct mptcp_rm_list *rm_list);
int mptcp_pm_get_local_id(struct mptcp_sock *msk, struct sock_common *skc);
int mptcp_pm_nl_get_local_id(struct mptcp_sock *msk,
                             struct mptcp_pm_addr_entry *skc);
int mptcp_userspace_pm_get_local_id(struct mptcp_sock *msk,
                                    struct mptcp_pm_addr_entry *skc);
bool mptcp_pm_is_backup(struct mptcp_sock *msk, struct sock_common *skc);
bool mptcp_pm_nl_is_backup(struct mptcp_sock *msk, struct mptcp_addr_info *skc);
bool mptcp_userspace_pm_is_backup(struct mptcp_sock *msk, struct mptcp_addr_info *skc);
int mptcp_pm_nl_dump_addr(struct sk_buff *msg,
                          struct netlink_callback *cb);
int mptcp_userspace_pm_dump_addr(struct sk_buff *msg,
                                 struct netlink_callback *cb);
int mptcp_pm_nl_get_addr(u8 id, struct mptcp_pm_addr_entry *addr,
                         struct genl_info *info);
int mptcp_userspace_pm_get_addr(u8 id, struct mptcp_pm_addr_entry *addr,
                                struct genl_info *info);

static inline u8 subflow_get_local_id(const struct mptcp_subflow_context *subflow)
{
        int local_id = READ_ONCE(subflow->local_id);

        if (local_id < 0)
                return 0;
        return local_id;
}

void __init mptcp_pm_kernel_register(void);
void __init mptcp_pm_userspace_register(void);
void __init mptcp_pm_nl_init(void);
void mptcp_pm_worker(struct mptcp_sock *msk);
void __mptcp_pm_kernel_worker(struct mptcp_sock *msk);
u8 mptcp_pm_get_endp_signal_max(const struct mptcp_sock *msk);
u8 mptcp_pm_get_endp_subflow_max(const struct mptcp_sock *msk);
u8 mptcp_pm_get_endp_laminar_max(const struct mptcp_sock *msk);
u8 mptcp_pm_get_endp_fullmesh_max(const struct mptcp_sock *msk);
u8 mptcp_pm_get_limit_add_addr_accepted(const struct mptcp_sock *msk);
u8 mptcp_pm_get_limit_extra_subflows(const struct mptcp_sock *msk);

/* called under PM lock */
static inline void __mptcp_pm_close_subflow(struct mptcp_sock *msk)
{
        if (--msk->pm.extra_subflows < mptcp_pm_get_limit_extra_subflows(msk))
                WRITE_ONCE(msk->pm.accept_subflow, true);
}

static inline void mptcp_pm_close_subflow(struct mptcp_sock *msk)
{
        spin_lock_bh(&msk->pm.lock);
        __mptcp_pm_close_subflow(msk);
        spin_unlock_bh(&msk->pm.lock);
}

static inline bool mptcp_pm_add_addr_c_flag_case(struct mptcp_sock *msk)
{
        return READ_ONCE(msk->pm.remote_deny_join_id0) &&
               msk->pm.local_addr_used == 0 &&
               mptcp_pm_get_limit_add_addr_accepted(msk) == 0 &&
               msk->pm.extra_subflows < mptcp_pm_get_limit_extra_subflows(msk);
}

void mptcp_sockopt_sync_locked(struct mptcp_sock *msk, struct sock *ssk);

static inline struct mptcp_ext *mptcp_get_ext(const struct sk_buff *skb)
{
        return (struct mptcp_ext *)skb_ext_find(skb, SKB_EXT_MPTCP);
}

void mptcp_diag_subflow_init(struct tcp_ulp_ops *ops);

static inline bool __mptcp_check_fallback(const struct mptcp_sock *msk)
{
        return test_bit(MPTCP_FALLBACK_DONE, &msk->flags);
}

static inline bool mptcp_check_fallback(const struct sock *sk)
{
        struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
        struct mptcp_sock *msk = mptcp_sk(subflow->conn);

        return __mptcp_check_fallback(msk);
}

static inline bool __mptcp_has_initial_subflow(const struct mptcp_sock *msk)
{
        struct sock *ssk = READ_ONCE(msk->first);

        return ssk && ((1 << inet_sk_state_load(ssk)) &
                       (TCPF_ESTABLISHED | TCPF_SYN_SENT |
                        TCPF_SYN_RECV | TCPF_LISTEN));
}

bool __mptcp_try_fallback(struct mptcp_sock *msk, int fb_mib);

static inline bool mptcp_try_fallback(struct sock *ssk, int fb_mib)
{
        struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
        struct sock *sk = subflow->conn;
        struct mptcp_sock *msk;

        msk = mptcp_sk(sk);
        if (!__mptcp_try_fallback(msk, fb_mib))
                return false;
        if (READ_ONCE(msk->snd_data_fin_enable) && !(ssk->sk_shutdown & SEND_SHUTDOWN)) {
                gfp_t saved_allocation = ssk->sk_allocation;

                /* we are in a atomic (BH) scope, override ssk default for data
                 * fin allocation
                 */
                ssk->sk_allocation = GFP_ATOMIC;
                ssk->sk_shutdown |= SEND_SHUTDOWN;
                tcp_shutdown(ssk, SEND_SHUTDOWN);
                ssk->sk_allocation = saved_allocation;
        }
        return true;
}

static inline void mptcp_early_fallback(struct mptcp_sock *msk,
                                        struct mptcp_subflow_context *subflow,
                                        int fb_mib)
{
        subflow->request_mptcp = 0;
        WARN_ON_ONCE(!__mptcp_try_fallback(msk, fb_mib));
}

static inline bool mptcp_check_infinite_map(struct sk_buff *skb)
{
        struct mptcp_ext *mpext;

        mpext = skb ? mptcp_get_ext(skb) : NULL;
        if (mpext && mpext->infinite_map)
                return true;

        return false;
}

static inline bool is_active_ssk(struct mptcp_subflow_context *subflow)
{
        return (subflow->request_mptcp || subflow->request_join);
}

static inline bool subflow_simultaneous_connect(struct sock *sk)
{
        struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);

        /* Note that the sk state implies !subflow->conn_finished. */
        return sk->sk_state == TCP_SYN_RECV && is_active_ssk(subflow);
}

#ifdef CONFIG_SYN_COOKIES
void subflow_init_req_cookie_join_save(const struct mptcp_subflow_request_sock *subflow_req,
                                       struct sk_buff *skb);
bool mptcp_token_join_cookie_init_state(struct mptcp_subflow_request_sock *subflow_req,
                                        struct sk_buff *skb);
void __init mptcp_join_cookie_init(void);
#else
static inline void
subflow_init_req_cookie_join_save(const struct mptcp_subflow_request_sock *subflow_req,
                                  struct sk_buff *skb) {}
static inline bool
mptcp_token_join_cookie_init_state(struct mptcp_subflow_request_sock *subflow_req,
                                   struct sk_buff *skb)
{
        return false;
}

static inline void mptcp_join_cookie_init(void) {}
#endif

#endif /* __MPTCP_PROTOCOL_H */