op-msg.c

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/*
 * Linux WiMAX
 * Generic messaging interface between userspace and driver/device
 *
 *
 * Copyright (C) 2007-2008 Intel Corporation <[email protected]>
 * Inaky Perez-Gonzalez <[email protected]>
 *
 * 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 Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 *
 * This implements a direct communication channel between user space and
 * the driver/device, by which free form messages can be sent back and
 * forth.
 *
 * This is intended for device-specific features, vendor quirks, etc.
 *
 * See include/net/wimax.h
 *
 * GENERIC NETLINK ENCODING AND CAPACITY
 *
 * A destination "pipe name" is added to each message; it is up to the
 * drivers to assign or use those names (if using them at all).
 *
 * Messages are encoded as a binary netlink attribute using nla_put()
 * using type NLA_UNSPEC (as some versions of libnl still in
 * deployment don't yet understand NLA_BINARY).
 *
 * The maximum capacity of this transport is PAGESIZE per message (so
 * the actual payload will be bit smaller depending on the
 * netlink/generic netlink attributes and headers).
 *
 * RECEPTION OF MESSAGES
 *
 * When a message is received from user space, it is passed verbatim
 * to the driver calling wimax_dev->op_msg_from_user(). The return
 * value from this function is passed back to user space as an ack
 * over the generic netlink protocol.
 *
 * The stack doesn't do any processing or interpretation of these
 * messages.
 *
 * SENDING MESSAGES
 *
 * Messages can be sent with wimax_msg().
 *
 * If the message delivery needs to happen on a different context to
 * that of its creation, wimax_msg_alloc() can be used to get a
 * pointer to the message that can be delivered later on with
 * wimax_msg_send().
 *
 * ROADMAP
 *
 * wimax_gnl_doit_msg_from_user()    Process a message from user space
 *   wimax_dev_get_by_genl_info()
 *   wimax_dev->op_msg_from_user()   Delivery of message to the driver
 *
 * wimax_msg()                       Send a message to user space
 *   wimax_msg_alloc()
 *   wimax_msg_send()
 */
#include <linux/device.h>
#include <linux/slab.h>
#include <net/genetlink.h>
#include <linux/netdevice.h>
#include <linux/wimax.h>
#include <linux/security.h>
#include <linux/export.h>
#include "wimax-internal.h"


#define D_SUBMODULE op_msg
#include "debug-levels.h"


struct sk_buff *wimax_msg_alloc(struct wimax_dev *wimax_dev,
                const char *pipe_name,
                const void *msg, size_t size,
                gfp_t gfp_flags)
{
    int result;
    struct device *dev = wimax_dev_to_dev(wimax_dev);
    size_t msg_size;
    void *genl_msg;
    struct sk_buff *skb;

    msg_size = nla_total_size(size)
        + nla_total_size(sizeof(u32))
        + (pipe_name ? nla_total_size(strlen(pipe_name)) : 0);
    result = -ENOMEM;
    skb = genlmsg_new(msg_size, gfp_flags);
    if (skb == NULL)
        goto error_new;
    genl_msg = genlmsg_put(skb, 0, 0, &wimax_gnl_family,
                   0, WIMAX_GNL_OP_MSG_TO_USER);
    if (genl_msg == NULL) {
        dev_err(dev, "no memory to create generic netlink message\n");
        goto error_genlmsg_put;
    }
    result = nla_put_u32(skb, WIMAX_GNL_MSG_IFIDX,
                 wimax_dev->net_dev->ifindex);
    if (result < 0) {
        dev_err(dev, "no memory to add ifindex attribute\n");
        goto error_nla_put;
    }
    if (pipe_name) {
        result = nla_put_string(skb, WIMAX_GNL_MSG_PIPE_NAME,
                    pipe_name);
        if (result < 0) {
            dev_err(dev, "no memory to add pipe_name attribute\n");
            goto error_nla_put;
        }
    }
    result = nla_put(skb, WIMAX_GNL_MSG_DATA, size, msg);
    if (result < 0) {
        dev_err(dev, "no memory to add payload (msg %p size %zu) in "
            "attribute: %d\n", msg, size, result);
        goto error_nla_put;
    }
    genlmsg_end(skb, genl_msg);
    return skb;

error_nla_put:
error_genlmsg_put:
error_new:
    nlmsg_free(skb);
    return ERR_PTR(result);
}
EXPORT_SYMBOL_GPL(wimax_msg_alloc);


const void *wimax_msg_data_len(struct sk_buff *msg, size_t *size)
{
    struct nlmsghdr *nlh = (void *) msg->head;
    struct nlattr *nla;

    nla = nlmsg_find_attr(nlh, sizeof(struct genlmsghdr),
                  WIMAX_GNL_MSG_DATA);
    if (nla == NULL) {
        printk(KERN_ERR "Cannot find attribute WIMAX_GNL_MSG_DATA\n");
        return NULL;
    }
    *size = nla_len(nla);
    return nla_data(nla);
}
EXPORT_SYMBOL_GPL(wimax_msg_data_len);


const void *wimax_msg_data(struct sk_buff *msg)
{
    struct nlmsghdr *nlh = (void *) msg->head;
    struct nlattr *nla;

    nla = nlmsg_find_attr(nlh, sizeof(struct genlmsghdr),
                  WIMAX_GNL_MSG_DATA);
    if (nla == NULL) {
        printk(KERN_ERR "Cannot find attribute WIMAX_GNL_MSG_DATA\n");
        return NULL;
    }
    return nla_data(nla);
}
EXPORT_SYMBOL_GPL(wimax_msg_data);


ssize_t wimax_msg_len(struct sk_buff *msg)
{
    struct nlmsghdr *nlh = (void *) msg->head;
    struct nlattr *nla;

    nla = nlmsg_find_attr(nlh, sizeof(struct genlmsghdr),
                  WIMAX_GNL_MSG_DATA);
    if (nla == NULL) {
        printk(KERN_ERR "Cannot find attribute WIMAX_GNL_MSG_DATA\n");
        return -EINVAL;
    }
    return nla_len(nla);
}
EXPORT_SYMBOL_GPL(wimax_msg_len);


int wimax_msg_send(struct wimax_dev *wimax_dev, struct sk_buff *skb)
{
    struct device *dev = wimax_dev_to_dev(wimax_dev);
    void *msg = skb->data;
    size_t size = skb->len;
    might_sleep();

    d_printf(1, dev, "CTX: wimax msg, %zu bytes\n", size);
    d_dump(2, dev, msg, size);
    genlmsg_multicast(skb, 0, wimax_gnl_mcg.id, GFP_KERNEL);
    d_printf(1, dev, "CTX: genl multicast done\n");
    return 0;
}
EXPORT_SYMBOL_GPL(wimax_msg_send);


int wimax_msg(struct wimax_dev *wimax_dev, const char *pipe_name,
          const void *buf, size_t size, gfp_t gfp_flags)
{
    int result = -ENOMEM;
    struct sk_buff *skb;

    skb = wimax_msg_alloc(wimax_dev, pipe_name, buf, size, gfp_flags);
    if (IS_ERR(skb))
        result = PTR_ERR(skb);
    else
        result = wimax_msg_send(wimax_dev, skb);
    return result;
}
EXPORT_SYMBOL_GPL(wimax_msg);


static const struct nla_policy wimax_gnl_msg_policy[WIMAX_GNL_ATTR_MAX + 1] = {
    [WIMAX_GNL_MSG_IFIDX] = {
        .type = NLA_U32,
    },
    [WIMAX_GNL_MSG_DATA] = {
        .type = NLA_UNSPEC, /* libnl doesn't grok BINARY yet */
    },
};


/*
 * Relays a message from user space to the driver
 *
 * The skb is passed to the driver-specific function with the netlink
 * and generic netlink headers already stripped.
 *
 * This call will block while handling/relaying the message.
 */
static
int wimax_gnl_doit_msg_from_user(struct sk_buff *skb, struct genl_info *info)
{
    int result, ifindex;
    struct wimax_dev *wimax_dev;
    struct device *dev;
    struct nlmsghdr *nlh = info->nlhdr;
    char *pipe_name;
    void *msg_buf;
    size_t msg_len;

    might_sleep();
    d_fnstart(3, NULL, "(skb %p info %p)\n", skb, info);
    result = -ENODEV;
    if (info->attrs[WIMAX_GNL_MSG_IFIDX] == NULL) {
        printk(KERN_ERR "WIMAX_GNL_MSG_FROM_USER: can't find IFIDX "
               "attribute\n");
        goto error_no_wimax_dev;
    }
    ifindex = nla_get_u32(info->attrs[WIMAX_GNL_MSG_IFIDX]);
    wimax_dev = wimax_dev_get_by_genl_info(info, ifindex);
    if (wimax_dev == NULL)
        goto error_no_wimax_dev;
    dev = wimax_dev_to_dev(wimax_dev);

    /* Unpack arguments */
    result = -EINVAL;
    if (info->attrs[WIMAX_GNL_MSG_DATA] == NULL) {
        dev_err(dev, "WIMAX_GNL_MSG_FROM_USER: can't find MSG_DATA "
            "attribute\n");
        goto error_no_data;
    }
    msg_buf = nla_data(info->attrs[WIMAX_GNL_MSG_DATA]);
    msg_len = nla_len(info->attrs[WIMAX_GNL_MSG_DATA]);

    if (info->attrs[WIMAX_GNL_MSG_PIPE_NAME] == NULL)
        pipe_name = NULL;
    else {
        struct nlattr *attr = info->attrs[WIMAX_GNL_MSG_PIPE_NAME];
        size_t attr_len = nla_len(attr);
        /* libnl-1.1 does not yet support NLA_NUL_STRING */
        result = -ENOMEM;
        pipe_name = kstrndup(nla_data(attr), attr_len + 1, GFP_KERNEL);
        if (pipe_name == NULL)
            goto error_alloc;
        pipe_name[attr_len] = 0;
    }
    mutex_lock(&wimax_dev->mutex);
    result = wimax_dev_is_ready(wimax_dev);
    if (result == -ENOMEDIUM)
        result = 0;
    if (result < 0)
        goto error_not_ready;
    result = -ENOSYS;
    if (wimax_dev->op_msg_from_user == NULL)
        goto error_noop;

    d_printf(1, dev,
         "CRX: nlmsghdr len %u type %u flags 0x%04x seq 0x%x pid %u\n",
         nlh->nlmsg_len, nlh->nlmsg_type, nlh->nlmsg_flags,
         nlh->nlmsg_seq, nlh->nlmsg_pid);
    d_printf(1, dev, "CRX: wimax message %zu bytes\n", msg_len);
    d_dump(2, dev, msg_buf, msg_len);

    result = wimax_dev->op_msg_from_user(wimax_dev, pipe_name,
                         msg_buf, msg_len, info);
error_noop:
error_not_ready:
    mutex_unlock(&wimax_dev->mutex);
error_alloc:
    kfree(pipe_name);
error_no_data:
    dev_put(wimax_dev->net_dev);
error_no_wimax_dev:
    d_fnend(3, NULL, "(skb %p info %p) = %d\n", skb, info, result);
    return result;
}


/*
 * Generic Netlink glue
 */

struct genl_ops wimax_gnl_msg_from_user = {
    .cmd = WIMAX_GNL_OP_MSG_FROM_USER,
    .flags = GENL_ADMIN_PERM,
    .policy = wimax_gnl_msg_policy,
    .doit = wimax_gnl_doit_msg_from_user,
    .dumpit = NULL,
};