text: /*
   * 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 <steve@chygwyn.com>
   *
   */
  #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)
  		goto nlmsg_failure;
  	old_tail = skb->tail;
  	nlh = NLMSG_PUT(skb, 0, 0, 0, size - sizeof(*nlh));
  	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;
  
  nlmsg_failure:
  	if (skb)
  		kfree_skb(skb);
  	*errp = -ENOMEM;
  	net_err_ratelimited("dn_rtmsg: error creating netlink message\n");
  	return NULL;
  }
  
  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		= PF_DECnet,
  	.hooknum	= NF_DN_ROUTE,
  	.priority	= NF_DN_PRI_DNRTMSG,
  };
  
  static int __init dn_rtmsg_init(void)
  {
  	int rv = 0;
  
  	dnrmg = netlink_kernel_create(&init_net,
  				      NETLINK_DNRTMSG, DNRNG_NLGRP_MAX,
  				      dnrmg_receive_user_skb,
  				      NULL, THIS_MODULE);
  	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 <steve@chygwyn.com>");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_DNRTMSG);
  
  module_init(dn_rtmsg_init);
  module_exit(dn_rtmsg_fini);
  
  