netlink_k.c

Go to the documentation of this file.

/*
 * Copyright (c) 2012 GCT Semiconductor, Inc. All rights reserved.
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * 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.
 */

#include <linux/module.h>
#include <linux/etherdevice.h>
#include <linux/netlink.h>
#include <asm/byteorder.h>
#include <net/sock.h>

#if !defined(NLMSG_HDRLEN)
#define NLMSG_HDRLEN     ((int) NLMSG_ALIGN(sizeof(struct nlmsghdr)))
#endif

#define ND_MAX_GROUP            30
#define ND_IFINDEX_LEN          sizeof(int)
#define ND_NLMSG_SPACE(len)     (NLMSG_SPACE(len) + ND_IFINDEX_LEN)
#define ND_NLMSG_DATA(nlh) \
    ((void *)((char *)NLMSG_DATA(nlh) + ND_IFINDEX_LEN))
#define ND_NLMSG_S_LEN(len)     (len+ND_IFINDEX_LEN)
#define ND_NLMSG_R_LEN(nlh)     (nlh->nlmsg_len-ND_IFINDEX_LEN)
#define ND_NLMSG_IFIDX(nlh)     NLMSG_DATA(nlh)
#define ND_MAX_MSG_LEN          8096

#if defined(DEFINE_MUTEX)
static DEFINE_MUTEX(netlink_mutex);
#else
static struct semaphore netlink_mutex;
#define mutex_lock(x)       down(x)
#define mutex_unlock(x)     up(x)
#endif

static void (*rcv_cb)(struct net_device *dev, u16 type, void *msg, int len);

static void netlink_rcv_cb(struct sk_buff *skb)
{
    struct nlmsghdr *nlh;
    struct net_device *dev;
    u32 mlen;
    void *msg;
    int ifindex;

    if (skb->len >= NLMSG_SPACE(0)) {
        nlh = (struct nlmsghdr *)skb->data;

        if (skb->len < nlh->nlmsg_len ||
        nlh->nlmsg_len > ND_MAX_MSG_LEN) {
            printk(KERN_ERR "Invalid length (%d,%d)\n", skb->len,
                nlh->nlmsg_len);
            return;
        }

        memcpy(&ifindex, ND_NLMSG_IFIDX(nlh), ND_IFINDEX_LEN);
        msg = ND_NLMSG_DATA(nlh);
        mlen = ND_NLMSG_R_LEN(nlh);

        if (rcv_cb) {
            dev = dev_get_by_index(&init_net, ifindex);
            if (dev) {
                rcv_cb(dev, nlh->nlmsg_type, msg, mlen);
                dev_put(dev);
            } else
                printk(KERN_ERR "dev_get_by_index(%d) "
                    "is not found.\n", ifindex);
        } else
            printk(KERN_ERR "Unregistered Callback\n");
    }
}

static void netlink_rcv(struct sk_buff *skb)
{
    mutex_lock(&netlink_mutex);
    netlink_rcv_cb(skb);
    mutex_unlock(&netlink_mutex);
}

struct sock *netlink_init(int unit, void (*cb)(struct net_device *dev, u16 type,
                        void *msg, int len))
{
    struct sock *sock;
    struct netlink_kernel_cfg cfg = {
        .input  = netlink_rcv,
    };

#if !defined(DEFINE_MUTEX)
    init_MUTEX(&netlink_mutex);
#endif

    sock = netlink_kernel_create(&init_net, unit, &cfg);

    if (sock)
        rcv_cb = cb;

    return sock;
}

void netlink_exit(struct sock *sock)
{
    netlink_kernel_release(sock);
}

int netlink_send(struct sock *sock, int group, u16 type, void *msg, int len)
{
    static u32 seq;
    struct sk_buff *skb = NULL;
    struct nlmsghdr *nlh;
    int ret = 0;

    if (group > ND_MAX_GROUP) {
        printk(KERN_ERR "Group %d is invalied.\n", group);
        printk(KERN_ERR "Valid group is 0 ~ %d.\n", ND_MAX_GROUP);
        return -EINVAL;
    }

    skb = alloc_skb(NLMSG_SPACE(len), GFP_ATOMIC);
    if (!skb) {
        printk(KERN_ERR "netlink_broadcast ret=%d\n", ret);
        return -ENOMEM;
    }

    seq++;
    nlh = nlmsg_put(skb, 0, seq, type, len, 0);
    if (!nlh) {
        kfree_skb(skb);
        return -EMSGSIZE;
    }
    memcpy(nlmsg_data(nlh), msg, len);

    NETLINK_CB(skb).portid = 0;
    NETLINK_CB(skb).dst_group = 0;

    ret = netlink_broadcast(sock, skb, 0, group+1, GFP_ATOMIC);

    if (!ret)
        return len;
    else {
        if (ret != -ESRCH) {
            printk(KERN_ERR "netlink_broadcast g=%d, t=%d, l=%d, r=%d\n",
                group, type, len, ret);
        }
        ret = 0;
    }
    return ret;
}