ip_queue.c

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static inline int dev_cmp(ipq_queue_element_t *e, unsigned long ifindex)
{
	if (e->info->indev)
		if (e->info->indev->ifindex == ifindex)
			return 1;
	if (e->info->outdev)
		if (e->info->outdev->ifindex == ifindex)
			return 1;
	return 0;
}

/* Drop any queued packets associated with device ifindex */
static void ipq_dev_drop(ipq_queue_t *q, int ifindex)
{
	ipq_queue_element_t *e;
	
	while ((e = ipq_dequeue(q, dev_cmp, ifindex))) {
		e->verdict = NF_DROP;
		nf_reinject(e->skb, e->info, e->verdict);
		kfree(e);
	}
}

/****************************************************************************
 *
 * Netfilter interface
 *
 ****************************************************************************/

/*
 * Packets arrive here from netfilter for queuing to userspace.
 * All of them must be fed back via nf_reinject() or Alexey will kill Rusty.
 */
static int netfilter_receive(struct sk_buff *skb,
                             struct nf_info *info, void *data)
{
	return ipq_enqueue((ipq_queue_t *)data, skb, info);
}

/****************************************************************************
 *
 * Netlink interface.
 *
 ****************************************************************************/

static struct sock *nfnl = NULL;
ipq_queue_t *nlq = NULL;

static struct sk_buff *netlink_build_message(ipq_queue_element_t *e, int *errp)
{
	unsigned char *old_tail;
	size_t size = 0;
	size_t data_len = 0;
	struct sk_buff *skb;
	ipq_packet_msg_t *pm;
	struct nlmsghdr *nlh;

	switch (nlq->peer.copy_mode) {
		size_t copy_range;

		case IPQ_COPY_META:
			size = NLMSG_SPACE(sizeof(*pm));
			data_len = 0;
			break;
		case IPQ_COPY_PACKET:
			copy_range = nlq->peer.copy_range;
			if (copy_range == 0 || copy_range > e->skb->len)
				data_len = e->skb->len;
			else
				data_len = copy_range;
			size = NLMSG_SPACE(sizeof(*pm) + data_len);
			
			break;
		case IPQ_COPY_NONE:
		default:
			*errp = -EINVAL;
			return NULL;
	}
	skb = alloc_skb(size, GFP_ATOMIC);
	if (!skb)
		goto nlmsg_failure;
	old_tail = skb->tail;
	nlh = NLMSG_PUT(skb, 0, 0, IPQM_PACKET, size - sizeof(*nlh));
	pm = NLMSG_DATA(nlh);
	memset(pm, 0, sizeof(*pm));
	pm->packet_id = (unsigned long )e;
	pm->data_len = data_len;
	pm->timestamp_sec = e->skb->stamp.tv_sec;
	pm->timestamp_usec = e->skb->stamp.tv_usec;
	pm->mark = e->skb->nfmark;
	pm->hook = e->info->hook;
	if (e->info->indev) strcpy(pm->indev_name, e->info->indev->name);
	else pm->indev_name[0] = '\0';
	if (e->info->outdev) strcpy(pm->outdev_name, e->info->outdev->name);
	else pm->outdev_name[0] = '\0';
	pm->hw_protocol = e->skb->protocol;
	if (data_len)
		memcpy(pm->payload, e->skb->data, data_len);
	nlh->nlmsg_len = skb->tail - old_tail;
	NETLINK_CB(skb).dst_groups = 0;
	return skb;
nlmsg_failure:
	if (skb)
		kfree_skb(skb);
	*errp = 0;
	printk(KERN_ERR "ip_queue: error creating netlink message\n");
	return NULL;
}

static int netlink_send_peer(ipq_queue_element_t *e)
{
	int status = 0;
	struct sk_buff *skb;

	skb = netlink_build_message(e, &status);
	if (skb == NULL)
		return status;
	return netlink_unicast(nfnl, skb, nlq->peer.pid, MSG_DONTWAIT);
}

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

extern __inline__ void netlink_receive_user_skb(struct sk_buff *skb)
{
	int status, type;
	struct nlmsghdr *nlh;

	nlh = (struct nlmsghdr *)skb->data;
	if (nlh->nlmsg_len < sizeof(*nlh)
	    || skb->len < nlh->nlmsg_len
	    || nlh->nlmsg_pid <= 0
	    || !(nlh->nlmsg_flags & NLM_F_REQUEST)
	    || nlh->nlmsg_flags & NLM_F_MULTI)
		RCV_SKB_FAIL(-EINVAL);
	if (nlh->nlmsg_flags & MSG_TRUNC)
		RCV_SKB_FAIL(-ECOMM);
	type = nlh->nlmsg_type;
	if (type < NLMSG_NOOP || type >= IPQM_MAX)
		RCV_SKB_FAIL(-EINVAL);
	if (type <= IPQM_BASE)
		return;
	if(!cap_raised(NETLINK_CB(skb).eff_cap, CAP_NET_ADMIN))
		RCV_SKB_FAIL(-EPERM);
	if (nlq->peer.pid && !nlq->peer.died
	    && (nlq->peer.pid != nlh->nlmsg_pid)) {
	    	printk(KERN_WARNING "ip_queue: peer pid changed from %d to "
	    	      "%d, flushing queue\n", nlq->peer.pid, nlh->nlmsg_pid);
		ipq_flush(nlq);
	}	
	nlq->peer.pid = nlh->nlmsg_pid;
	nlq->peer.died = 0;
	status = ipq_receive_peer(nlq, NLMSG_DATA(nlh),
	                          type, skb->len - NLMSG_LENGTH(0));
	if (status < 0)
		RCV_SKB_FAIL(status);
	if (nlh->nlmsg_flags & NLM_F_ACK)
		netlink_ack(skb, nlh, 0);
        return;
}

/* Note: we are only dealing with single part messages at the moment. */
static void netlink_receive_user_sk(struct sock *sk, int len)
{
	do {
		struct sk_buff *skb;

		if (rtnl_shlock_nowait())
			return;
		while ((skb = skb_dequeue(&sk->receive_queue)) != NULL) {
			netlink_receive_user_skb(skb);
			kfree_skb(skb);
		}
		up(&rtnl_sem);
	} while (nfnl && nfnl->receive_queue.qlen);
}

/****************************************************************************
 *
 * System events
 *
 ****************************************************************************/

static int receive_event(struct notifier_block *this,
                         unsigned long event, void *ptr)
{
	struct net_device *dev = ptr;

	/* Drop any packets associated with the downed device */
	if (event == NETDEV_DOWN)
		ipq_dev_drop(nlq, dev->ifindex);
	return NOTIFY_DONE;
}

struct notifier_block ipq_dev_notifier = {
	receive_event,
	NULL,
	0
};

/****************************************************************************
 *
 * Sysctl - queue tuning.
 *
 ****************************************************************************/

static int sysctl_maxlen = IPQ_QMAX_DEFAULT;

static struct ctl_table_header *ipq_sysctl_header;

static ctl_table ipq_table[] = {
	{ NET_IPQ_QMAX, NET_IPQ_QMAX_NAME, &sysctl_maxlen,
	  sizeof(sysctl_maxlen), 0644,  NULL, proc_dointvec },
 	{ 0 }
};

static ctl_table ipq_dir_table[] = {
	{NET_IPV4, "ipv4", NULL, 0, 0555, ipq_table, 0, 0, 0, 0, 0},
	{ 0 }
};

static ctl_table ipq_root_table[] = {
	{CTL_NET, "net", NULL, 0, 0555, ipq_dir_table, 0, 0, 0, 0, 0},
	{ 0 }
};

/****************************************************************************
 *
 * Procfs - debugging info.
 *
 ****************************************************************************/

static int ipq_get_info(char *buffer, char **start, off_t offset, int length)
{
	int len;

	spin_lock_bh(&nlq->lock);
	len = sprintf(buffer,
	              "Peer pid            : %d\n"
	              "Peer died           : %d\n"
	              "Peer copy mode      : %d\n"
	              "Peer copy range     : %Zu\n"
	              "Queue length        : %d\n"
	              "Queue max. length   : %d\n"
	              "Queue flushing      : %d\n"
	              "Queue terminate     : %d\n",
	              nlq->peer.pid,
	              nlq->peer.died,
	              nlq->peer.copy_mode,
	              nlq->peer.copy_range,
	              nlq->len,
	              *nlq->maxlen,
	              nlq->flushing,
	              nlq->terminate);
	spin_unlock_bh(&nlq->lock);
	*start = buffer + offset;
	len -= offset;
	if (len > length)
		len = length;
	else if (len < 0)
		len = 0;
	return len;
}

/****************************************************************************
 *
 * Module stuff.
 *
 ****************************************************************************/

static int __init init(void)
{
	int status = 0;
	
	nfnl = netlink_kernel_create(NETLINK_FIREWALL, netlink_receive_user_sk);
	if (nfnl == NULL) {
		printk(KERN_ERR "ip_queue: initialisation failed: unable to "
		       "create kernel netlink socket\n");
		return -ENOMEM;
	}
	nlq = ipq_create_queue(netfilter_receive,
	                       netlink_send_peer, &status, &sysctl_maxlen);
	if (nlq == NULL) {
		printk(KERN_ERR "ip_queue: initialisation failed: unable to "
		       "create queue\n");
		sock_release(nfnl->socket);
		return status;
	}
	register_netdevice_notifier(&ipq_dev_notifier);
	proc_net_create(IPQ_PROC_FS_NAME, 0, ipq_get_info);
	ipq_sysctl_header = register_sysctl_table(ipq_root_table, 0);
	return status;
}

static void __exit fini(void)
{
	unregister_sysctl_table(ipq_sysctl_header);
	proc_net_remove(IPQ_PROC_FS_NAME);
	unregister_netdevice_notifier(&ipq_dev_notifier);
	ipq_destroy_queue(nlq);
	sock_release(nfnl->socket);
}

MODULE_DESCRIPTION("IPv4 packet queue handler");
module_init(init);
module_exit(fini);