pep.c

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/*
 * File: pep.c
 *
 * Phonet pipe protocol end point socket
 *
 * Copyright (C) 2008 Nokia Corporation.
 *
 * Author: Rémi Denis-Courmont
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA
 */

#include <linux/kernel.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->data[0] = 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->data[0] = 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->data[0], /* 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->data[0] = oph->data[1]; /* 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->data[0] != PN_PEP_TYPE_COMMON) {
        LIMIT_NETDEBUG(KERN_DEBUG"Phonet unknown PEP type: %u\n",
                (unsigned int)hdr->data[0]);
        return -EOPNOTSUPP;
    }

    switch (hdr->data[1]) {
    case PN_PEP_IND_FLOW_CONTROL:
        switch (pn->tx_fc) {
        case PN_LEGACY_FLOW_CONTROL:
            switch (hdr->data[4]) {
            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[4] == 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[4], &pn->tx_credits);
        break;

    default:
        LIMIT_NETDEBUG(KERN_DEBUG"Phonet unknown PEP indication: %u\n",
                (unsigned int)hdr->data[1]);
        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->data[0];

    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;
        }
        /* fall through */
    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) {
            atomic_inc(&sk->sk_drops);
            break;
        }
        __skb_pull(skb, 4);
        queue = &pn->ctrlreq_queue;
        goto queue;

    case PNS_PIPE_ALIGNED_DATA:
        __skb_pull(skb, 1);
        /* fall through */
    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) {
            atomic_inc(&sk->sk_drops);
            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;
        /* fall through */
    case PNS_PIPE_RESET_IND:
        if (!pn->init_enable)
            break;
        /* fall through */
    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:
        LIMIT_NETDEBUG(KERN_DEBUG"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);
    err = skb->len;
    skb_queue_tail(queue, skb);
    if (!sock_flag(sk, SOCK_DEAD))
        sk->sk_data_ready(sk, err);
    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[4];
    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);
        /* fall through */
    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) {
            atomic_inc(&sk->sk_drops);
            err = NET_RX_DROP;
            break;
        }
        pn->rx_credits--;
        skb->dev = NULL;
        skb_set_owner_r(skb, sk);
        err = skb->len;
        skb_queue_tail(&sk->sk_receive_queue, skb);
        if (!sock_flag(sk, SOCK_DEAD))
            sk->sk_data_ready(sk, err);
        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 hlist_node *node;
    struct sock *sknode;
    u16 dobj = pn_sockaddr_get_object(dst);

    sk_for_each(sknode, node, 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, 0);
        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->data[0] = 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, int flags, int *errp)
{
    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, 0, flags & O_NONBLOCK, errp);
    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[4];
    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 */
    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);
    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_dst_sockaddr(skb, &dst);
    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(newsk);
        newsk = NULL;
        goto drop;
    }
    sk_add_node(newsk, &pn->hlist);
drop:
    release_sock(sk);
    kfree_skb(skb);
    *errp = err;
    return newsk;
}

static int pep_sock_connect(struct sock *sk, struct sockaddr *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 int pep_ioctl(struct sock *sk, int cmd, unsigned long arg)
{
    struct pep_sock *pn = pep_sk(sk);
    int answ;
    int ret = -ENOIOCTLCMD;

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

        lock_sock(sk);
        if (sock_flag(sk, SOCK_URGINLINE) &&
            !skb_queue_empty(&pn->ctrlreq_queue))
            answ = skb_peek(&pn->ctrlreq_queue)->len;
        else if (!skb_queue_empty(&sk->sk_receive_queue))
            answ = skb_peek(&sk->sk_receive_queue)->len;
        else
            answ = 0;
        release_sock(sk);
        ret = put_user(answ, (int __user *)arg);
        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
            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,
                char __user *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 (get_user(val, (int __user *) optval))
            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->data[0] = 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 kiocb *iocb, 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_fromiovec(skb_put(skb, len), msg->msg_iov, 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(wait);

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

        prepare_to_wait(sk_sleep(sk), &wait,
                TASK_INTERRUPTIBLE);
        done = sk_wait_event(sk, &timeo, atomic_read(&pn->tx_credits));
        finish_wait(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 kiocb *iocb, struct sock *sk,
            struct msghdr *msg, size_t len, int noblock,
            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, noblock, &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_iovec(skb, 0, msg->msg_iov, 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 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);