dn_rtmsg.c

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/*
 * DECnet       An implementation of the DECnet protocol suite for the LINUX
 *              operating system.  DECnet is implemented using the  BSD Socket
 *              interface as the means of communication with the user level.
 *
 *              DECnet Routing Message Grabulator
 *
 *              (C) 2000 ChyGwyn Limited  -  http://www.chygwyn.com/
 *              This code may be copied under the GPL v.2 or at your option
 *              any later version.
 *
 * Author:      Steven Whitehouse <[email protected]>
 *
 */
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/netdevice.h>
#include <linux/netfilter.h>
#include <linux/spinlock.h>
#include <linux/netlink.h>
#include <linux/netfilter_decnet.h>

#include <net/sock.h>
#include <net/flow.h>
#include <net/dn.h>
#include <net/dn_route.h>

static struct sock *dnrmg = NULL;


static struct sk_buff *dnrmg_build_message(struct sk_buff *rt_skb, int *errp)
{
    struct sk_buff *skb = NULL;
    size_t size;
    sk_buff_data_t old_tail;
    struct nlmsghdr *nlh;
    unsigned char *ptr;
    struct nf_dn_rtmsg *rtm;

    size = NLMSG_SPACE(rt_skb->len);
    size += NLMSG_ALIGN(sizeof(struct nf_dn_rtmsg));
    skb = alloc_skb(size, GFP_ATOMIC);
    if (!skb) {
        *errp = -ENOMEM;
        return NULL;
    }
    old_tail = skb->tail;
    nlh = nlmsg_put(skb, 0, 0, 0, size - sizeof(*nlh), 0);
    if (!nlh) {
        kfree_skb(skb);
        *errp = -ENOMEM;
        return NULL;
    }
    rtm = (struct nf_dn_rtmsg *)NLMSG_DATA(nlh);
    rtm->nfdn_ifindex = rt_skb->dev->ifindex;
    ptr = NFDN_RTMSG(rtm);
    skb_copy_from_linear_data(rt_skb, ptr, rt_skb->len);
    nlh->nlmsg_len = skb->tail - old_tail;
    return skb;
}

static void dnrmg_send_peer(struct sk_buff *skb)
{
    struct sk_buff *skb2;
    int status = 0;
    int group = 0;
    unsigned char flags = *skb->data;

    switch (flags & DN_RT_CNTL_MSK) {
    case DN_RT_PKT_L1RT:
        group = DNRNG_NLGRP_L1;
        break;
    case DN_RT_PKT_L2RT:
        group = DNRNG_NLGRP_L2;
        break;
    default:
        return;
    }

    skb2 = dnrmg_build_message(skb, &status);
    if (skb2 == NULL)
        return;
    NETLINK_CB(skb2).dst_group = group;
    netlink_broadcast(dnrmg, skb2, 0, group, GFP_ATOMIC);
}


static unsigned int dnrmg_hook(unsigned int hook,
            struct sk_buff *skb,
            const struct net_device *in,
            const struct net_device *out,
            int (*okfn)(struct sk_buff *))
{
    dnrmg_send_peer(skb);
    return NF_ACCEPT;
}


#define RCV_SKB_FAIL(err) do { netlink_ack(skb, nlh, (err)); return; } while (0)

static inline void dnrmg_receive_user_skb(struct sk_buff *skb)
{
    struct nlmsghdr *nlh = nlmsg_hdr(skb);

    if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len)
        return;

    if (!capable(CAP_NET_ADMIN))
        RCV_SKB_FAIL(-EPERM);

    /* Eventually we might send routing messages too */

    RCV_SKB_FAIL(-EINVAL);
}

static struct nf_hook_ops dnrmg_ops __read_mostly = {
    .hook       = dnrmg_hook,
    .pf     = NFPROTO_DECNET,
    .hooknum    = NF_DN_ROUTE,
    .priority   = NF_DN_PRI_DNRTMSG,
};

static int __init dn_rtmsg_init(void)
{
    int rv = 0;
    struct netlink_kernel_cfg cfg = {
        .groups = DNRNG_NLGRP_MAX,
        .input  = dnrmg_receive_user_skb,
    };

    dnrmg = netlink_kernel_create(&init_net, NETLINK_DNRTMSG, &cfg);
    if (dnrmg == NULL) {
        printk(KERN_ERR "dn_rtmsg: Cannot create netlink socket");
        return -ENOMEM;
    }

    rv = nf_register_hook(&dnrmg_ops);
    if (rv) {
        netlink_kernel_release(dnrmg);
    }

    return rv;
}

static void __exit dn_rtmsg_fini(void)
{
    nf_unregister_hook(&dnrmg_ops);
    netlink_kernel_release(dnrmg);
}


MODULE_DESCRIPTION("DECnet Routing Message Grabulator");
MODULE_AUTHOR("Steven Whitehouse <[email protected]>");
MODULE_LICENSE("GPL");
MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_DNRTMSG);

module_init(dn_rtmsg_init);
module_exit(dn_rtmsg_fini);