// SPDX-License-Identifier: GPL-2.0-only
/*
 * File: pep.c
 *
 * Phonet pipe protocol end point socket
 *
 * Copyright (C) 2008 Nokia Corporation.
 *
 * Author: Rémi Denis-Courmont
 */

#include <linux/kernel.h>
#include <linux/sched/signal.h>
#include <linux/slab.h>
#include <linux/socket.h>
#include <net/sock.h>
#include <net/tcp_states.h>
#include <asm/ioctls.h>

#include <linux/phonet.h>
#include <linux/module.h>
#include <net/phonet/phonet.h>
#include <net/phonet/pep.h>
#include <net/phonet/gprs.h>

/* sk_state values:
 * TCP_CLOSE            sock not in use yet
 * TCP_CLOSE_WAIT       disconnected pipe
 * TCP_LISTEN           listening pipe endpoint
 * TCP_SYN_RECV         connected pipe in disabled state
 * TCP_ESTABLISHED      connected pipe in enabled state
 *
 * pep_sock locking:
 *  - sk_state, hlist: sock lock needed
 *  - listener: read only
 *  - pipe_handle: read only
 */

#define CREDITS_MAX     10
#define CREDITS_THR     7

#define pep_sb_size(s) (((s) + 5) & ~3) /* 2-bytes head, 32-bits aligned */

/* Get the next TLV sub-block. */
static unsigned char *pep_get_sb(struct sk_buff *skb, u8 *ptype, u8 *plen,
                                        void *buf)
{
        void *data = NULL;
        struct {
                u8 sb_type;
                u8 sb_len;
        } *ph, h;
        int buflen = *plen;

        ph = skb_header_pointer(skb, 0, 2, &h);
        if (ph == NULL || ph->sb_len < 2 || !pskb_may_pull(skb, ph->sb_len))
                return NULL;
        ph->sb_len -= 2;
        *ptype = ph->sb_type;
        *plen = ph->sb_len;

        if (buflen > ph->sb_len)
                buflen = ph->sb_len;
        data = skb_header_pointer(skb, 2, buflen, buf);
        __skb_pull(skb, 2 + ph->sb_len);
        return data;
}

static struct sk_buff *pep_alloc_skb(struct sock *sk, const void *payload,
                                        int len, gfp_t priority)
{
        struct sk_buff *skb = alloc_skb(MAX_PNPIPE_HEADER + len, priority);
        if (!skb)
                return NULL;
        skb_set_owner_w(skb, sk);

        skb_reserve(skb, MAX_PNPIPE_HEADER);
        __skb_put(skb, len);
        skb_copy_to_linear_data(skb, payload, len);
        __skb_push(skb, sizeof(struct pnpipehdr));
        skb_reset_transport_header(skb);
        return skb;
}

static int pep_reply(struct sock *sk, struct sk_buff *oskb, u8 code,
                        const void *data, int len, gfp_t priority)
{
        const struct pnpipehdr *oph = pnp_hdr(oskb);
        struct pnpipehdr *ph;
        struct sk_buff *skb;
        struct sockaddr_pn peer;

        skb = pep_alloc_skb(sk, data, len, priority);
        if (!skb)
                return -ENOMEM;

        ph = pnp_hdr(skb);
        ph->utid = oph->utid;
        ph->message_id = oph->message_id + 1; /* REQ -> RESP */
        ph->pipe_handle = oph->pipe_handle;
        ph->error_code = code;

        pn_skb_get_src_sockaddr(oskb, &peer);
        return pn_skb_send(sk, skb, &peer);
}

static int pep_indicate(struct sock *sk, u8 id, u8 code,
                        const void *data, int len, gfp_t priority)
{
        struct pep_sock *pn = pep_sk(sk);
        struct pnpipehdr *ph;
        struct sk_buff *skb;

        skb = pep_alloc_skb(sk, data, len, priority);
        if (!skb)
                return -ENOMEM;

        ph = pnp_hdr(skb);
        ph->utid = 0;
        ph->message_id = id;
        ph->pipe_handle = pn->pipe_handle;
        ph->error_code = code;
        return pn_skb_send(sk, skb, NULL);
}

#define PAD 0x00

static int pipe_handler_request(struct sock *sk, u8 id, u8 code,
                                const void *data, int len)
{
        struct pep_sock *pn = pep_sk(sk);
        struct pnpipehdr *ph;
        struct sk_buff *skb;

        skb = pep_alloc_skb(sk, data, len, GFP_KERNEL);
        if (!skb)
                return -ENOMEM;

        ph = pnp_hdr(skb);
        ph->utid = id; /* whatever */
        ph->message_id = id;
        ph->pipe_handle = pn->pipe_handle;
        ph->error_code = code;
        return pn_skb_send(sk, skb, NULL);
}

static int pipe_handler_send_created_ind(struct sock *sk)
{
        struct pep_sock *pn = pep_sk(sk);
        u8 data[4] = {
                PN_PIPE_SB_NEGOTIATED_FC, pep_sb_size(2),
                pn->tx_fc, pn->rx_fc,
        };

        return pep_indicate(sk, PNS_PIPE_CREATED_IND, 1 /* sub-blocks */,
                                data, 4, GFP_ATOMIC);
}

static int pep_accept_conn(struct sock *sk, struct sk_buff *skb)
{
        static const u8 data[20] = {
                PAD, PAD, PAD, 2 /* sub-blocks */,
                PN_PIPE_SB_REQUIRED_FC_TX, pep_sb_size(5), 3, PAD,
                        PN_MULTI_CREDIT_FLOW_CONTROL,
                        PN_ONE_CREDIT_FLOW_CONTROL,
                        PN_LEGACY_FLOW_CONTROL,
                        PAD,
                PN_PIPE_SB_PREFERRED_FC_RX, pep_sb_size(5), 3, PAD,
                        PN_MULTI_CREDIT_FLOW_CONTROL,
                        PN_ONE_CREDIT_FLOW_CONTROL,
                        PN_LEGACY_FLOW_CONTROL,
                        PAD,
        };

        might_sleep();
        return pep_reply(sk, skb, PN_PIPE_NO_ERROR, data, sizeof(data),
                                GFP_KERNEL);
}

static int pep_reject_conn(struct sock *sk, struct sk_buff *skb, u8 code,
                                gfp_t priority)
{
        static const u8 data[4] = { PAD, PAD, PAD, 0 /* sub-blocks */ };
        WARN_ON(code == PN_PIPE_NO_ERROR);
        return pep_reply(sk, skb, code, data, sizeof(data), priority);
}

/* Control requests are not sent by the pipe service and have a specific
 * message format. */
static int pep_ctrlreq_error(struct sock *sk, struct sk_buff *oskb, u8 code,
                                gfp_t priority)
{
        const struct pnpipehdr *oph = pnp_hdr(oskb);
        struct sk_buff *skb;
        struct pnpipehdr *ph;
        struct sockaddr_pn dst;
        u8 data[4] = {
                oph->pep_type, /* PEP type */
                code, /* error code, at an unusual offset */
                PAD, PAD,
        };

        skb = pep_alloc_skb(sk, data, 4, priority);
        if (!skb)
                return -ENOMEM;

        ph = pnp_hdr(skb);
        ph->utid = oph->utid;
        ph->message_id = PNS_PEP_CTRL_RESP;
        ph->pipe_handle = oph->pipe_handle;
        ph->data0 = oph->data[0]; /* CTRL id */

        pn_skb_get_src_sockaddr(oskb, &dst);
        return pn_skb_send(sk, skb, &dst);
}

static int pipe_snd_status(struct sock *sk, u8 type, u8 status, gfp_t priority)
{
        u8 data[4] = { type, PAD, PAD, status };

        return pep_indicate(sk, PNS_PEP_STATUS_IND, PN_PEP_TYPE_COMMON,
                                data, 4, priority);
}

/* Send our RX flow control information to the sender.
 * Socket must be locked. */
static void pipe_grant_credits(struct sock *sk, gfp_t priority)
{
        struct pep_sock *pn = pep_sk(sk);

        BUG_ON(sk->sk_state != TCP_ESTABLISHED);

        switch (pn->rx_fc) {
        case PN_LEGACY_FLOW_CONTROL: /* TODO */
                break;
        case PN_ONE_CREDIT_FLOW_CONTROL:
                if (pipe_snd_status(sk, PN_PEP_IND_FLOW_CONTROL,
                                        PEP_IND_READY, priority) == 0)
                        pn->rx_credits = 1;
                break;
        case PN_MULTI_CREDIT_FLOW_CONTROL:
                if ((pn->rx_credits + CREDITS_THR) > CREDITS_MAX)
                        break;
                if (pipe_snd_status(sk, PN_PEP_IND_ID_MCFC_GRANT_CREDITS,
                                        CREDITS_MAX - pn->rx_credits,
                                        priority) == 0)
                        pn->rx_credits = CREDITS_MAX;
                break;
        }
}

static int pipe_rcv_status(struct sock *sk, struct sk_buff *skb)
{
        struct pep_sock *pn = pep_sk(sk);
        struct pnpipehdr *hdr;
        int wake = 0;

        if (!pskb_may_pull(skb, sizeof(*hdr) + 4))
                return -EINVAL;

        hdr = pnp_hdr(skb);
        if (hdr->pep_type != PN_PEP_TYPE_COMMON) {
                net_dbg_ratelimited("Phonet unknown PEP type: %u\n",
                                    (unsigned int)hdr->pep_type);
                return -EOPNOTSUPP;
        }

        switch (hdr->data[0]) {
        case PN_PEP_IND_FLOW_CONTROL:
                switch (pn->tx_fc) {
                case PN_LEGACY_FLOW_CONTROL:
                        switch (hdr->data[3]) {
                        case PEP_IND_BUSY:
                                atomic_set(&pn->tx_credits, 0);
                                break;
                        case PEP_IND_READY:
                                atomic_set(&pn->tx_credits, wake = 1);
                                break;
                        }
                        break;
                case PN_ONE_CREDIT_FLOW_CONTROL:
                        if (hdr->data[3] == PEP_IND_READY)
                                atomic_set(&pn->tx_credits, wake = 1);
                        break;
                }
                break;

        case PN_PEP_IND_ID_MCFC_GRANT_CREDITS:
                if (pn->tx_fc != PN_MULTI_CREDIT_FLOW_CONTROL)
                        break;
                atomic_add(wake = hdr->data[3], &pn->tx_credits);
                break;

        default:
                net_dbg_ratelimited("Phonet unknown PEP indication: %u\n",
                                    (unsigned int)hdr->data[0]);
                return -EOPNOTSUPP;
        }
        if (wake)
                sk->sk_write_space(sk);
        return 0;
}

static int pipe_rcv_created(struct sock *sk, struct sk_buff *skb)
{
        struct pep_sock *pn = pep_sk(sk);
        struct pnpipehdr *hdr = pnp_hdr(skb);
        u8 n_sb = hdr->data0;

        pn->rx_fc = pn->tx_fc = PN_LEGACY_FLOW_CONTROL;
        __skb_pull(skb, sizeof(*hdr));
        while (n_sb > 0) {
                u8 type, buf[2], len = sizeof(buf);
                u8 *data = pep_get_sb(skb, &type, &len, buf);

                if (data == NULL)
                        return -EINVAL;
                switch (type) {
                case PN_PIPE_SB_NEGOTIATED_FC:
                        if (len < 2 || (data[0] | data[1]) > 3)
                                break;
                        pn->tx_fc = data[0] & 3;
                        pn->rx_fc = data[1] & 3;
                        break;
                }
                n_sb--;
        }
        return 0;
}

/* Queue an skb to a connected sock.
 * Socket lock must be held. */
static int pipe_do_rcv(struct sock *sk, struct sk_buff *skb)
{
        struct pep_sock *pn = pep_sk(sk);
        struct pnpipehdr *hdr = pnp_hdr(skb);
        struct sk_buff_head *queue;
        int err = 0;

        BUG_ON(sk->sk_state == TCP_CLOSE_WAIT);

        switch (hdr->message_id) {
        case PNS_PEP_CONNECT_REQ:
                pep_reject_conn(sk, skb, PN_PIPE_ERR_PEP_IN_USE, GFP_ATOMIC);
                break;

        case PNS_PEP_DISCONNECT_REQ:
                pep_reply(sk, skb, PN_PIPE_NO_ERROR, NULL, 0, GFP_ATOMIC);
                sk->sk_state = TCP_CLOSE_WAIT;
                if (!sock_flag(sk, SOCK_DEAD))
                        sk->sk_state_change(sk);
                break;

        case PNS_PEP_ENABLE_REQ:
                /* Wait for PNS_PIPE_(ENABLED|REDIRECTED)_IND */
                pep_reply(sk, skb, PN_PIPE_NO_ERROR, NULL, 0, GFP_ATOMIC);
                break;

        case PNS_PEP_RESET_REQ:
                switch (hdr->state_after_reset) {
                case PN_PIPE_DISABLE:
                        pn->init_enable = 0;
                        break;
                case PN_PIPE_ENABLE:
                        pn->init_enable = 1;
                        break;
                default: /* not allowed to send an error here!? */
                        err = -EINVAL;
                        goto out;
                }
                fallthrough;
        case PNS_PEP_DISABLE_REQ:
                atomic_set(&pn->tx_credits, 0);
                pep_reply(sk, skb, PN_PIPE_NO_ERROR, NULL, 0, GFP_ATOMIC);
                break;

        case PNS_PEP_CTRL_REQ:
                if (skb_queue_len(&pn->ctrlreq_queue) >= PNPIPE_CTRLREQ_MAX) {
                        sk_drops_inc(sk);
                        break;
                }
                __skb_pull(skb, 4);
                queue = &pn->ctrlreq_queue;
                goto queue;

        case PNS_PIPE_ALIGNED_DATA:
                __skb_pull(skb, 1);
                fallthrough;
        case PNS_PIPE_DATA:
                __skb_pull(skb, 3); /* Pipe data header */
                if (!pn_flow_safe(pn->rx_fc)) {
                        err = sock_queue_rcv_skb(sk, skb);
                        if (!err)
                                return NET_RX_SUCCESS;
                        err = -ENOBUFS;
                        break;
                }

                if (pn->rx_credits == 0) {
                        sk_drops_inc(sk);
                        err = -ENOBUFS;
                        break;
                }
                pn->rx_credits--;
                queue = &sk->sk_receive_queue;
                goto queue;

        case PNS_PEP_STATUS_IND:
                pipe_rcv_status(sk, skb);
                break;

        case PNS_PIPE_REDIRECTED_IND:
                err = pipe_rcv_created(sk, skb);
                break;

        case PNS_PIPE_CREATED_IND:
                err = pipe_rcv_created(sk, skb);
                if (err)
                        break;
                fallthrough;
        case PNS_PIPE_RESET_IND:
                if (!pn->init_enable)
                        break;
                fallthrough;
        case PNS_PIPE_ENABLED_IND:
                if (!pn_flow_safe(pn->tx_fc)) {
                        atomic_set(&pn->tx_credits, 1);
                        sk->sk_write_space(sk);
                }
                if (sk->sk_state == TCP_ESTABLISHED)
                        break; /* Nothing to do */
                sk->sk_state = TCP_ESTABLISHED;
                pipe_grant_credits(sk, GFP_ATOMIC);
                break;

        case PNS_PIPE_DISABLED_IND:
                sk->sk_state = TCP_SYN_RECV;
                pn->rx_credits = 0;
                break;

        default:
                net_dbg_ratelimited("Phonet unknown PEP message: %u\n",
                                    hdr->message_id);
                err = -EINVAL;
        }
out:
        kfree_skb(skb);
        return (err == -ENOBUFS) ? NET_RX_DROP : NET_RX_SUCCESS;

queue:
        skb->dev = NULL;
        skb_set_owner_r(skb, sk);
        skb_queue_tail(queue, skb);
        if (!sock_flag(sk, SOCK_DEAD))
                sk->sk_data_ready(sk);
        return NET_RX_SUCCESS;
}

/* Destroy connected sock. */
static void pipe_destruct(struct sock *sk)
{
        struct pep_sock *pn = pep_sk(sk);

        skb_queue_purge(&sk->sk_receive_queue);
        skb_queue_purge(&pn->ctrlreq_queue);
}

static u8 pipe_negotiate_fc(const u8 *fcs, unsigned int n)
{
        unsigned int i;
        u8 final_fc = PN_NO_FLOW_CONTROL;

        for (i = 0; i < n; i++) {
                u8 fc = fcs[i];

                if (fc > final_fc && fc < PN_MAX_FLOW_CONTROL)
                        final_fc = fc;
        }
        return final_fc;
}

static int pep_connresp_rcv(struct sock *sk, struct sk_buff *skb)
{
        struct pep_sock *pn = pep_sk(sk);
        struct pnpipehdr *hdr;
        u8 n_sb;

        if (!pskb_pull(skb, sizeof(*hdr) + 4))
                return -EINVAL;

        hdr = pnp_hdr(skb);
        if (hdr->error_code != PN_PIPE_NO_ERROR)
                return -ECONNREFUSED;

        /* Parse sub-blocks */
        n_sb = hdr->data[3];
        while (n_sb > 0) {
                u8 type, buf[6], len = sizeof(buf);
                const u8 *data = pep_get_sb(skb, &type, &len, buf);

                if (data == NULL)
                        return -EINVAL;

                switch (type) {
                case PN_PIPE_SB_REQUIRED_FC_TX:
                        if (len < 2 || len < data[0])
                                break;
                        pn->tx_fc = pipe_negotiate_fc(data + 2, len - 2);
                        break;

                case PN_PIPE_SB_PREFERRED_FC_RX:
                        if (len < 2 || len < data[0])
                                break;
                        pn->rx_fc = pipe_negotiate_fc(data + 2, len - 2);
                        break;

                }
                n_sb--;
        }

        return pipe_handler_send_created_ind(sk);
}

static int pep_enableresp_rcv(struct sock *sk, struct sk_buff *skb)
{
        struct pnpipehdr *hdr = pnp_hdr(skb);

        if (hdr->error_code != PN_PIPE_NO_ERROR)
                return -ECONNREFUSED;

        return pep_indicate(sk, PNS_PIPE_ENABLED_IND, 0 /* sub-blocks */,
                NULL, 0, GFP_ATOMIC);

}

static void pipe_start_flow_control(struct sock *sk)
{
        struct pep_sock *pn = pep_sk(sk);

        if (!pn_flow_safe(pn->tx_fc)) {
                atomic_set(&pn->tx_credits, 1);
                sk->sk_write_space(sk);
        }
        pipe_grant_credits(sk, GFP_ATOMIC);
}

/* Queue an skb to an actively connected sock.
 * Socket lock must be held. */
static int pipe_handler_do_rcv(struct sock *sk, struct sk_buff *skb)
{
        struct pep_sock *pn = pep_sk(sk);
        struct pnpipehdr *hdr = pnp_hdr(skb);
        int err = NET_RX_SUCCESS;

        switch (hdr->message_id) {
        case PNS_PIPE_ALIGNED_DATA:
                __skb_pull(skb, 1);
                fallthrough;
        case PNS_PIPE_DATA:
                __skb_pull(skb, 3); /* Pipe data header */
                if (!pn_flow_safe(pn->rx_fc)) {
                        err = sock_queue_rcv_skb(sk, skb);
                        if (!err)
                                return NET_RX_SUCCESS;
                        err = NET_RX_DROP;
                        break;
                }

                if (pn->rx_credits == 0) {
                        sk_drops_inc(sk);
                        err = NET_RX_DROP;
                        break;
                }
                pn->rx_credits--;
                skb->dev = NULL;
                skb_set_owner_r(skb, sk);
                skb_queue_tail(&sk->sk_receive_queue, skb);
                if (!sock_flag(sk, SOCK_DEAD))
                        sk->sk_data_ready(sk);
                return NET_RX_SUCCESS;

        case PNS_PEP_CONNECT_RESP:
                if (sk->sk_state != TCP_SYN_SENT)
                        break;
                if (!sock_flag(sk, SOCK_DEAD))
                        sk->sk_state_change(sk);
                if (pep_connresp_rcv(sk, skb)) {
                        sk->sk_state = TCP_CLOSE_WAIT;
                        break;
                }
                if (pn->init_enable == PN_PIPE_DISABLE)
                        sk->sk_state = TCP_SYN_RECV;
                else {
                        sk->sk_state = TCP_ESTABLISHED;
                        pipe_start_flow_control(sk);
                }
                break;

        case PNS_PEP_ENABLE_RESP:
                if (sk->sk_state != TCP_SYN_SENT)
                        break;

                if (pep_enableresp_rcv(sk, skb)) {
                        sk->sk_state = TCP_CLOSE_WAIT;
                        break;
                }

                sk->sk_state = TCP_ESTABLISHED;
                pipe_start_flow_control(sk);
                break;

        case PNS_PEP_DISCONNECT_RESP:
                /* sock should already be dead, nothing to do */
                break;

        case PNS_PEP_STATUS_IND:
                pipe_rcv_status(sk, skb);
                break;
        }
        kfree_skb(skb);
        return err;
}

/* Listening sock must be locked */
static struct sock *pep_find_pipe(const struct hlist_head *hlist,
                                        const struct sockaddr_pn *dst,
                                        u8 pipe_handle)
{
        struct sock *sknode;
        u16 dobj = pn_sockaddr_get_object(dst);

        sk_for_each(sknode, hlist) {
                struct pep_sock *pnnode = pep_sk(sknode);

                /* Ports match, but addresses might not: */
                if (pnnode->pn_sk.sobject != dobj)
                        continue;
                if (pnnode->pipe_handle != pipe_handle)
                        continue;
                if (sknode->sk_state == TCP_CLOSE_WAIT)
                        continue;

                sock_hold(sknode);
                return sknode;
        }
        return NULL;
}

/*
 * Deliver an skb to a listening sock.
 * Socket lock must be held.
 * We then queue the skb to the right connected sock (if any).
 */
static int pep_do_rcv(struct sock *sk, struct sk_buff *skb)
{
        struct pep_sock *pn = pep_sk(sk);
        struct sock *sknode;
        struct pnpipehdr *hdr;
        struct sockaddr_pn dst;
        u8 pipe_handle;

        if (!pskb_may_pull(skb, sizeof(*hdr)))
                goto drop;

        hdr = pnp_hdr(skb);
        pipe_handle = hdr->pipe_handle;
        if (pipe_handle == PN_PIPE_INVALID_HANDLE)
                goto drop;

        pn_skb_get_dst_sockaddr(skb, &dst);

        /* Look for an existing pipe handle */
        sknode = pep_find_pipe(&pn->hlist, &dst, pipe_handle);
        if (sknode)
                return sk_receive_skb(sknode, skb, 1);

        switch (hdr->message_id) {
        case PNS_PEP_CONNECT_REQ:
                if (sk->sk_state != TCP_LISTEN || sk_acceptq_is_full(sk)) {
                        pep_reject_conn(sk, skb, PN_PIPE_ERR_PEP_IN_USE,
                                        GFP_ATOMIC);
                        break;
                }
                skb_queue_head(&sk->sk_receive_queue, skb);
                sk_acceptq_added(sk);
                if (!sock_flag(sk, SOCK_DEAD))
                        sk->sk_data_ready(sk);
                return NET_RX_SUCCESS;

        case PNS_PEP_DISCONNECT_REQ:
                pep_reply(sk, skb, PN_PIPE_NO_ERROR, NULL, 0, GFP_ATOMIC);
                break;

        case PNS_PEP_CTRL_REQ:
                pep_ctrlreq_error(sk, skb, PN_PIPE_INVALID_HANDLE, GFP_ATOMIC);
                break;

        case PNS_PEP_RESET_REQ:
        case PNS_PEP_ENABLE_REQ:
        case PNS_PEP_DISABLE_REQ:
                /* invalid handle is not even allowed here! */
                break;

        default:
                if ((1 << sk->sk_state)
                                & ~(TCPF_CLOSE|TCPF_LISTEN|TCPF_CLOSE_WAIT))
                        /* actively connected socket */
                        return pipe_handler_do_rcv(sk, skb);
        }
drop:
        kfree_skb(skb);
        return NET_RX_SUCCESS;
}

static int pipe_do_remove(struct sock *sk)
{
        struct pep_sock *pn = pep_sk(sk);
        struct pnpipehdr *ph;
        struct sk_buff *skb;

        skb = pep_alloc_skb(sk, NULL, 0, GFP_KERNEL);
        if (!skb)
                return -ENOMEM;

        ph = pnp_hdr(skb);
        ph->utid = 0;
        ph->message_id = PNS_PIPE_REMOVE_REQ;
        ph->pipe_handle = pn->pipe_handle;
        ph->data0 = PAD;
        return pn_skb_send(sk, skb, NULL);
}

/* associated socket ceases to exist */
static void pep_sock_close(struct sock *sk, long timeout)
{
        struct pep_sock *pn = pep_sk(sk);
        int ifindex = 0;

        sock_hold(sk); /* keep a reference after sk_common_release() */
        sk_common_release(sk);

        lock_sock(sk);
        if ((1 << sk->sk_state) & (TCPF_SYN_RECV|TCPF_ESTABLISHED)) {
                if (sk->sk_backlog_rcv == pipe_do_rcv)
                        /* Forcefully remove dangling Phonet pipe */
                        pipe_do_remove(sk);
                else
                        pipe_handler_request(sk, PNS_PEP_DISCONNECT_REQ, PAD,
                                                NULL, 0);
        }
        sk->sk_state = TCP_CLOSE;

        ifindex = pn->ifindex;
        pn->ifindex = 0;
        release_sock(sk);

        if (ifindex)
                gprs_detach(sk);
        sock_put(sk);
}

static struct sock *pep_sock_accept(struct sock *sk,
                                    struct proto_accept_arg *arg)
{
        struct pep_sock *pn = pep_sk(sk), *newpn;
        struct sock *newsk = NULL;
        struct sk_buff *skb;
        struct pnpipehdr *hdr;
        struct sockaddr_pn dst, src;
        int err;
        u16 peer_type;
        u8 pipe_handle, enabled, n_sb;
        u8 aligned = 0;

        skb = skb_recv_datagram(sk, (arg->flags & O_NONBLOCK) ? MSG_DONTWAIT : 0,
                                &arg->err);
        if (!skb)
                return NULL;

        lock_sock(sk);
        if (sk->sk_state != TCP_LISTEN) {
                err = -EINVAL;
                goto drop;
        }
        sk_acceptq_removed(sk);

        err = -EPROTO;
        if (!pskb_may_pull(skb, sizeof(*hdr) + 4))
                goto drop;

        hdr = pnp_hdr(skb);
        pipe_handle = hdr->pipe_handle;
        switch (hdr->state_after_connect) {
        case PN_PIPE_DISABLE:
                enabled = 0;
                break;
        case PN_PIPE_ENABLE:
                enabled = 1;
                break;
        default:
                pep_reject_conn(sk, skb, PN_PIPE_ERR_INVALID_PARAM,
                                GFP_KERNEL);
                goto drop;
        }
        peer_type = hdr->other_pep_type << 8;

        /* Parse sub-blocks (options) */
        n_sb = hdr->data[3];
        while (n_sb > 0) {
                u8 type, buf[1], len = sizeof(buf);
                const u8 *data = pep_get_sb(skb, &type, &len, buf);

                if (data == NULL)
                        goto drop;
                switch (type) {
                case PN_PIPE_SB_CONNECT_REQ_PEP_SUB_TYPE:
                        if (len < 1)
                                goto drop;
                        peer_type = (peer_type & 0xff00) | data[0];
                        break;
                case PN_PIPE_SB_ALIGNED_DATA:
                        aligned = data[0] != 0;
                        break;
                }
                n_sb--;
        }

        /* Check for duplicate pipe handle */
        pn_skb_get_dst_sockaddr(skb, &dst);
        newsk = pep_find_pipe(&pn->hlist, &dst, pipe_handle);
        if (unlikely(newsk)) {
                __sock_put(newsk);
                newsk = NULL;
                pep_reject_conn(sk, skb, PN_PIPE_ERR_PEP_IN_USE, GFP_KERNEL);
                goto drop;
        }

        /* Create a new to-be-accepted sock */
        newsk = sk_alloc(sock_net(sk), PF_PHONET, GFP_KERNEL, sk->sk_prot,
                         arg->kern);
        if (!newsk) {
                pep_reject_conn(sk, skb, PN_PIPE_ERR_OVERLOAD, GFP_KERNEL);
                err = -ENOBUFS;
                goto drop;
        }

        sock_init_data(NULL, newsk);
        newsk->sk_state = TCP_SYN_RECV;
        newsk->sk_backlog_rcv = pipe_do_rcv;
        newsk->sk_protocol = sk->sk_protocol;
        newsk->sk_destruct = pipe_destruct;

        newpn = pep_sk(newsk);
        pn_skb_get_src_sockaddr(skb, &src);
        newpn->pn_sk.sobject = pn_sockaddr_get_object(&dst);
        newpn->pn_sk.dobject = pn_sockaddr_get_object(&src);
        newpn->pn_sk.resource = pn_sockaddr_get_resource(&dst);
        sock_hold(sk);
        newpn->listener = sk;
        skb_queue_head_init(&newpn->ctrlreq_queue);
        newpn->pipe_handle = pipe_handle;
        atomic_set(&newpn->tx_credits, 0);
        newpn->ifindex = 0;
        newpn->peer_type = peer_type;
        newpn->rx_credits = 0;
        newpn->rx_fc = newpn->tx_fc = PN_LEGACY_FLOW_CONTROL;
        newpn->init_enable = enabled;
        newpn->aligned = aligned;

        err = pep_accept_conn(newsk, skb);
        if (err) {
                __sock_put(sk);
                sock_put(newsk);
                newsk = NULL;
                goto drop;
        }
        sk_add_node(newsk, &pn->hlist);
drop:
        release_sock(sk);
        kfree_skb(skb);
        arg->err = err;
        return newsk;
}

static int pep_sock_connect(struct sock *sk, struct sockaddr_unsized *addr,
                            int len)
{
        struct pep_sock *pn = pep_sk(sk);
        int err;
        u8 data[4] = { 0 /* sub-blocks */, PAD, PAD, PAD };

        if (pn->pipe_handle == PN_PIPE_INVALID_HANDLE)
                pn->pipe_handle = 1; /* anything but INVALID_HANDLE */

        err = pipe_handler_request(sk, PNS_PEP_CONNECT_REQ,
                                pn->init_enable, data, 4);
        if (err) {
                pn->pipe_handle = PN_PIPE_INVALID_HANDLE;
                return err;
        }

        sk->sk_state = TCP_SYN_SENT;

        return 0;
}

static int pep_sock_enable(struct sock *sk, struct sockaddr *addr, int len)
{
        int err;

        err = pipe_handler_request(sk, PNS_PEP_ENABLE_REQ, PAD,
                                NULL, 0);
        if (err)
                return err;

        sk->sk_state = TCP_SYN_SENT;

        return 0;
}

static unsigned int pep_first_packet_length(struct sock *sk)
{
        struct pep_sock *pn = pep_sk(sk);
        struct sk_buff_head *q;
        struct sk_buff *skb;
        unsigned int len = 0;
        bool found = false;

        if (sock_flag(sk, SOCK_URGINLINE)) {
                q = &pn->ctrlreq_queue;
                spin_lock_bh(&q->lock);
                skb = skb_peek(q);
                if (skb) {
                        len = skb->len;
                        found = true;
                }
                spin_unlock_bh(&q->lock);
        }

        if (likely(!found)) {
                q = &sk->sk_receive_queue;
                spin_lock_bh(&q->lock);
                skb = skb_peek(q);
                if (skb)
                        len = skb->len;
                spin_unlock_bh(&q->lock);
        }

        return len;
}

static int pep_ioctl(struct sock *sk, int cmd, int *karg)
{
        struct pep_sock *pn = pep_sk(sk);
        int ret = -ENOIOCTLCMD;

        switch (cmd) {
        case SIOCINQ:
                if (sk->sk_state == TCP_LISTEN) {
                        ret = -EINVAL;
                        break;
                }

                *karg = pep_first_packet_length(sk);
                ret = 0;
                break;

        case SIOCPNENABLEPIPE:
                lock_sock(sk);
                if (sk->sk_state == TCP_SYN_SENT)
                        ret =  -EBUSY;
                else if (sk->sk_state == TCP_ESTABLISHED)
                        ret = -EISCONN;
                else if (!pn->pn_sk.sobject)
                        ret = -EADDRNOTAVAIL;
                else
                        ret = pep_sock_enable(sk, NULL, 0);
                release_sock(sk);
                break;
        }

        return ret;
}

static int pep_init(struct sock *sk)
{
        struct pep_sock *pn = pep_sk(sk);

        sk->sk_destruct = pipe_destruct;
        INIT_HLIST_HEAD(&pn->hlist);
        pn->listener = NULL;
        skb_queue_head_init(&pn->ctrlreq_queue);
        atomic_set(&pn->tx_credits, 0);
        pn->ifindex = 0;
        pn->peer_type = 0;
        pn->pipe_handle = PN_PIPE_INVALID_HANDLE;
        pn->rx_credits = 0;
        pn->rx_fc = pn->tx_fc = PN_LEGACY_FLOW_CONTROL;
        pn->init_enable = 1;
        pn->aligned = 0;
        return 0;
}

static int pep_setsockopt(struct sock *sk, int level, int optname,
                          sockptr_t optval, unsigned int optlen)
{
        struct pep_sock *pn = pep_sk(sk);
        int val = 0, err = 0;

        if (level != SOL_PNPIPE)
                return -ENOPROTOOPT;
        if (optlen >= sizeof(int)) {
                if (copy_from_sockptr(&val, optval, sizeof(int)))
                        return -EFAULT;
        }

        lock_sock(sk);
        switch (optname) {
        case PNPIPE_ENCAP:
                if (val && val != PNPIPE_ENCAP_IP) {
                        err = -EINVAL;
                        break;
                }
                if (!pn->ifindex == !val)
                        break; /* Nothing to do! */
                if (!capable(CAP_NET_ADMIN)) {
                        err = -EPERM;
                        break;
                }
                if (val) {
                        release_sock(sk);
                        err = gprs_attach(sk);
                        if (err > 0) {
                                pn->ifindex = err;
                                err = 0;
                        }
                } else {
                        pn->ifindex = 0;
                        release_sock(sk);
                        gprs_detach(sk);
                        err = 0;
                }
                goto out_norel;

        case PNPIPE_HANDLE:
                if ((sk->sk_state == TCP_CLOSE) &&
                        (val >= 0) && (val < PN_PIPE_INVALID_HANDLE))
                        pn->pipe_handle = val;
                else
                        err = -EINVAL;
                break;

        case PNPIPE_INITSTATE:
                pn->init_enable = !!val;
                break;

        default:
                err = -ENOPROTOOPT;
        }
        release_sock(sk);

out_norel:
        return err;
}

static int pep_getsockopt(struct sock *sk, int level, int optname,
                                char __user *optval, int __user *optlen)
{
        struct pep_sock *pn = pep_sk(sk);
        int len, val;

        if (level != SOL_PNPIPE)
                return -ENOPROTOOPT;
        if (get_user(len, optlen))
                return -EFAULT;

        switch (optname) {
        case PNPIPE_ENCAP:
                val = pn->ifindex ? PNPIPE_ENCAP_IP : PNPIPE_ENCAP_NONE;
                break;

        case PNPIPE_IFINDEX:
                val = pn->ifindex;
                break;

        case PNPIPE_HANDLE:
                val = pn->pipe_handle;
                if (val == PN_PIPE_INVALID_HANDLE)
                        return -EINVAL;
                break;

        case PNPIPE_INITSTATE:
                val = pn->init_enable;
                break;

        default:
                return -ENOPROTOOPT;
        }

        len = min_t(unsigned int, sizeof(int), len);
        if (put_user(len, optlen))
                return -EFAULT;
        if (put_user(val, (int __user *) optval))
                return -EFAULT;
        return 0;
}

static int pipe_skb_send(struct sock *sk, struct sk_buff *skb)
{
        struct pep_sock *pn = pep_sk(sk);
        struct pnpipehdr *ph;
        int err;

        if (pn_flow_safe(pn->tx_fc) &&
            !atomic_add_unless(&pn->tx_credits, -1, 0)) {
                kfree_skb(skb);
                return -ENOBUFS;
        }

        skb_push(skb, 3 + pn->aligned);
        skb_reset_transport_header(skb);
        ph = pnp_hdr(skb);
        ph->utid = 0;
        if (pn->aligned) {
                ph->message_id = PNS_PIPE_ALIGNED_DATA;
                ph->data0 = 0; /* padding */
        } else
                ph->message_id = PNS_PIPE_DATA;
        ph->pipe_handle = pn->pipe_handle;
        err = pn_skb_send(sk, skb, NULL);

        if (err && pn_flow_safe(pn->tx_fc))
                atomic_inc(&pn->tx_credits);
        return err;

}

static int pep_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
{
        struct pep_sock *pn = pep_sk(sk);
        struct sk_buff *skb;
        long timeo;
        int flags = msg->msg_flags;
        int err, done;

        if (len > USHRT_MAX)
                return -EMSGSIZE;

        if ((msg->msg_flags & ~(MSG_DONTWAIT|MSG_EOR|MSG_NOSIGNAL|
                                MSG_CMSG_COMPAT)) ||
                        !(msg->msg_flags & MSG_EOR))
                return -EOPNOTSUPP;

        skb = sock_alloc_send_skb(sk, MAX_PNPIPE_HEADER + len,
                                        flags & MSG_DONTWAIT, &err);
        if (!skb)
                return err;

        skb_reserve(skb, MAX_PHONET_HEADER + 3 + pn->aligned);
        err = memcpy_from_msg(skb_put(skb, len), msg, len);
        if (err < 0)
                goto outfree;

        lock_sock(sk);
        timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
        if ((1 << sk->sk_state) & (TCPF_LISTEN|TCPF_CLOSE)) {
                err = -ENOTCONN;
                goto out;
        }
        if (sk->sk_state != TCP_ESTABLISHED) {
                /* Wait until the pipe gets to enabled state */
disabled:
                err = sk_stream_wait_connect(sk, &timeo);
                if (err)
                        goto out;

                if (sk->sk_state == TCP_CLOSE_WAIT) {
                        err = -ECONNRESET;
                        goto out;
                }
        }
        BUG_ON(sk->sk_state != TCP_ESTABLISHED);

        /* Wait until flow control allows TX */
        done = atomic_read(&pn->tx_credits);
        while (!done) {
                DEFINE_WAIT_FUNC(wait, woken_wake_function);

                if (!timeo) {
                        err = -EAGAIN;
                        goto out;
                }
                if (signal_pending(current)) {
                        err = sock_intr_errno(timeo);
                        goto out;
                }

                add_wait_queue(sk_sleep(sk), &wait);
                done = sk_wait_event(sk, &timeo, atomic_read(&pn->tx_credits), &wait);
                remove_wait_queue(sk_sleep(sk), &wait);

                if (sk->sk_state != TCP_ESTABLISHED)
                        goto disabled;
        }

        err = pipe_skb_send(sk, skb);
        if (err >= 0)
                err = len; /* success! */
        skb = NULL;
out:
        release_sock(sk);
outfree:
        kfree_skb(skb);
        return err;
}

int pep_writeable(struct sock *sk)
{
        struct pep_sock *pn = pep_sk(sk);

        return atomic_read(&pn->tx_credits);
}

int pep_write(struct sock *sk, struct sk_buff *skb)
{
        struct sk_buff *rskb, *fs;
        int flen = 0;

        if (pep_sk(sk)->aligned)
                return pipe_skb_send(sk, skb);

        rskb = alloc_skb(MAX_PNPIPE_HEADER, GFP_ATOMIC);
        if (!rskb) {
                kfree_skb(skb);
                return -ENOMEM;
        }
        skb_shinfo(rskb)->frag_list = skb;
        rskb->len += skb->len;
        rskb->data_len += rskb->len;
        rskb->truesize += rskb->len;

        /* Avoid nested fragments */
        skb_walk_frags(skb, fs)
                flen += fs->len;
        skb->next = skb_shinfo(skb)->frag_list;
        skb_frag_list_init(skb);
        skb->len -= flen;
        skb->data_len -= flen;
        skb->truesize -= flen;

        skb_reserve(rskb, MAX_PHONET_HEADER + 3);
        return pipe_skb_send(sk, rskb);
}

struct sk_buff *pep_read(struct sock *sk)
{
        struct sk_buff *skb = skb_dequeue(&sk->sk_receive_queue);

        if (sk->sk_state == TCP_ESTABLISHED)
                pipe_grant_credits(sk, GFP_ATOMIC);
        return skb;
}

static int pep_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
                       int flags, int *addr_len)
{
        struct sk_buff *skb;
        int err;

        if (flags & ~(MSG_OOB|MSG_PEEK|MSG_TRUNC|MSG_DONTWAIT|MSG_WAITALL|
                        MSG_NOSIGNAL|MSG_CMSG_COMPAT))
                return -EOPNOTSUPP;

        if (unlikely(1 << sk->sk_state & (TCPF_LISTEN | TCPF_CLOSE)))
                return -ENOTCONN;

        if ((flags & MSG_OOB) || sock_flag(sk, SOCK_URGINLINE)) {
                /* Dequeue and acknowledge control request */
                struct pep_sock *pn = pep_sk(sk);

                if (flags & MSG_PEEK)
                        return -EOPNOTSUPP;
                skb = skb_dequeue(&pn->ctrlreq_queue);
                if (skb) {
                        pep_ctrlreq_error(sk, skb, PN_PIPE_NO_ERROR,
                                                GFP_KERNEL);
                        msg->msg_flags |= MSG_OOB;
                        goto copy;
                }
                if (flags & MSG_OOB)
                        return -EINVAL;
        }

        skb = skb_recv_datagram(sk, flags, &err);
        lock_sock(sk);
        if (skb == NULL) {
                if (err == -ENOTCONN && sk->sk_state == TCP_CLOSE_WAIT)
                        err = -ECONNRESET;
                release_sock(sk);
                return err;
        }

        if (sk->sk_state == TCP_ESTABLISHED)
                pipe_grant_credits(sk, GFP_KERNEL);
        release_sock(sk);
copy:
        msg->msg_flags |= MSG_EOR;
        if (skb->len > len)
                msg->msg_flags |= MSG_TRUNC;
        else
                len = skb->len;

        err = skb_copy_datagram_msg(skb, 0, msg, len);
        if (!err)
                err = (flags & MSG_TRUNC) ? skb->len : len;

        skb_free_datagram(sk, skb);
        return err;
}

static void pep_sock_unhash(struct sock *sk)
{
        struct pep_sock *pn = pep_sk(sk);
        struct sock *skparent = NULL;

        lock_sock(sk);

        if (pn->listener != NULL) {
                skparent = pn->listener;
                pn->listener = NULL;
                release_sock(sk);

                pn = pep_sk(skparent);
                lock_sock(skparent);
                sk_del_node_init(sk);
                sk = skparent;
        }

        /* Unhash a listening sock only when it is closed
         * and all of its active connected pipes are closed. */
        if (hlist_empty(&pn->hlist))
                pn_sock_unhash(&pn->pn_sk.sk);
        release_sock(sk);

        if (skparent)
                sock_put(skparent);
}

static struct proto pep_proto = {
        .close          = pep_sock_close,
        .accept         = pep_sock_accept,
        .connect        = pep_sock_connect,
        .ioctl          = pep_ioctl,
        .init           = pep_init,
        .setsockopt     = pep_setsockopt,
        .getsockopt     = pep_getsockopt,
        .sendmsg        = pep_sendmsg,
        .recvmsg        = pep_recvmsg,
        .backlog_rcv    = pep_do_rcv,
        .hash           = pn_sock_hash,
        .unhash         = pep_sock_unhash,
        .get_port       = pn_sock_get_port,
        .obj_size       = sizeof(struct pep_sock),
        .owner          = THIS_MODULE,
        .name           = "PNPIPE",
};

static const struct phonet_protocol pep_pn_proto = {
        .ops            = &phonet_stream_ops,
        .prot           = &pep_proto,
        .sock_type      = SOCK_SEQPACKET,
};

static int __init pep_register(void)
{
        return phonet_proto_register(PN_PROTO_PIPE, &pep_pn_proto);
}

static void __exit pep_unregister(void)
{
        phonet_proto_unregister(PN_PROTO_PIPE, &pep_pn_proto);
}

module_init(pep_register);
module_exit(pep_unregister);
MODULE_AUTHOR("Remi Denis-Courmont, Nokia");
MODULE_DESCRIPTION("Phonet pipe protocol");
MODULE_LICENSE("GPL");
MODULE_ALIAS_NET_PF_PROTO(PF_PHONET, PN_PROTO_PIPE);