path: root/net/sched/act_api.c

/*
 * net/sched/act_api.c	Packet action API.
 *
 *		This program is free software; you can redistribute it and/or
 *		modify it under the terms of the GNU General Public License
 *		as published by the Free Software Foundation; either version
 *		2 of the License, or (at your option) any later version.
 *
 * Author:	Jamal Hadi Salim
 *
 *
 */

#include <asm/uaccess.h>
#include <asm/system.h>
#include <linux/bitops.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/in.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/rtnetlink.h>
#include <linux/init.h>
#include <linux/kmod.h>
#include <net/sock.h>
#include <net/sch_generic.h>
#include <net/act_api.h>

#if 0 /* control */
#define DPRINTK(format, args...) printk(KERN_DEBUG format, ##args)
#else
#define DPRINTK(format, args...)
#endif
#if 0 /* data */
#define D2PRINTK(format, args...) printk(KERN_DEBUG format, ##args)
#else
#define D2PRINTK(format, args...)
#endif

static struct tc_action_ops *act_base = NULL;
static DEFINE_RWLOCK(act_mod_lock);

int tcf_register_action(struct tc_action_ops *act)
{
	struct tc_action_ops *a, **ap;

	write_lock(&act_mod_lock);
	for (ap = &act_base; (a = *ap) != NULL; ap = &a->next) {
		if (act->type == a->type || (strcmp(act->kind, a->kind) == 0)) {
			write_unlock(&act_mod_lock);
			return -EEXIST;
		}
	}
	act->next = NULL;
	*ap = act;
	write_unlock(&act_mod_lock);
	return 0;
}

int tcf_unregister_action(struct tc_action_ops *act)
{
	struct tc_action_ops *a, **ap;
	int err = -ENOENT;

	write_lock(&act_mod_lock);
	for (ap = &act_base; (a = *ap) != NULL; ap = &a->next)
		if (a == act)
			break;
	if (a) {
		*ap = a->next;
		a->next = NULL;
		err = 0;
	}
	write_unlock(&act_mod_lock);
	return err;
}

/* lookup by name */
static struct tc_action_ops *tc_lookup_action_n(char *kind)
{
	struct tc_action_ops *a = NULL;

	if (kind) {
		read_lock(&act_mod_lock);
		for (a = act_base; a; a = a->next) {
			if (strcmp(kind, a->kind) == 0) {
				if (!try_module_get(a->owner)) {
					read_unlock(&act_mod_lock);
					return NULL;
				}
				break;
			}
		}
		read_unlock(&act_mod_lock);
	}
	return a;
}

/* lookup by rtattr */
static struct tc_action_ops *tc_lookup_action(struct rtattr *kind)
{
	struct tc_action_ops *a = NULL;

	if (kind) {
		read_lock(&act_mod_lock);
		for (a = act_base; a; a = a->next) {
			if (rtattr_strcmp(kind, a->kind) == 0) {
				if (!try_module_get(a->owner)) {
					read_unlock(&act_mod_lock);
					return NULL;
				}
				break;
			}
		}
		read_unlock(&act_mod_lock);
	}
	return a;
}

#if 0
/* lookup by id */
static struct tc_action_ops *tc_lookup_action_id(u32 type)
{
	struct tc_action_ops *a = NULL;

	if (type) {
		read_lock(&act_mod_lock);
		for (a = act_base; a; a = a->next) {
			if (a->type == type) {
				if (!try_module_get(a->owner)) {
					read_unlock(&act_mod_lock);
					return NULL;
				}
				break;
			}
		}
		read_unlock(&act_mod_lock);
	}
	return a;
}
#endif

int tcf_action_exec(struct sk_buff *skb, struct tc_action *act,
                    struct tcf_result *res)
{
	struct tc_action *a;
	int ret = -1;

	if (skb->tc_verd & TC_NCLS) {
		skb->tc_verd = CLR_TC_NCLS(skb->tc_verd);
		D2PRINTK("(%p)tcf_action_exec: cleared TC_NCLS in %s out %s\n",
		         skb, skb->input_dev ? skb->input_dev->name : "xxx",
		         skb->dev->name);
		ret = TC_ACT_OK;
		goto exec_done;
	}
	while ((a = act) != NULL) {
repeat:
		if (a->ops && a->ops->act) {
			ret = a->ops->act(skb, a, res);
			if (TC_MUNGED & skb->tc_verd) {
				/* copied already, allow trampling */
				skb->tc_verd = SET_TC_OK2MUNGE(skb->tc_verd);
				skb->tc_verd = CLR_TC_MUNGED(skb->tc_verd);
			}
			if (ret == TC_ACT_REPEAT)
				goto repeat;	/* we need a ttl - JHS */
			if (ret != TC_ACT_PIPE)
				goto exec_done;
		}
		act = a->next;
	}
exec_done:
	return ret;
}

void tcf_action_destroy(struct tc_action *act, int bind)
{
	struct tc_action *a;

	for (a = act; a; a = act) {
		if (a->ops && a->ops->cleanup) {
			DPRINTK("tcf_action_destroy destroying %p next %p\n",
			        a, a->next);
			if (a->ops->cleanup(a, bind) == ACT_P_DELETED)
				module_put(a->ops->owner);
			act = act->next;
			kfree(a);
		} else { /*FIXME: Remove later - catch insertion bugs*/
			printk("tcf_action_destroy: BUG? destroying NULL ops\n");
			act = act->next;
			kfree(a);
		}
	}
}

int
tcf_action_dump_old(struct sk_buff *skb, struct tc_action *a, int bind, int ref)
{
	int err = -EINVAL;

	if (a->ops == NULL || a->ops->dump == NULL)
		return err;
	return a->ops->dump(skb, a, bind, ref);
}

int
tcf_action_dump_1(struct sk_buff *skb, struct tc_action *a, int bind, int ref)
{
	int err = -EINVAL;
	unsigned char *b = skb->tail;
	struct rtattr *r;

	if (a->ops == NULL || a->ops->dump == NULL)
		return err;

	RTA_PUT(skb, TCA_KIND, IFNAMSIZ, a->ops->kind);
	if (tcf_action_copy_stats(skb, a, 0))
		goto rtattr_failure;
	r = (struct rtattr*) skb->tail;
	RTA_PUT(skb, TCA_OPTIONS, 0, NULL);
	if ((err = tcf_action_dump_old(skb, a, bind, ref)) > 0) {
		r->rta_len = skb->tail - (u8*)r;
		return err;
	}

rtattr_failure:
	skb_trim(skb, b - skb->data);
	return -1;
}

int
tcf_action_dump(struct sk_buff *skb, struct tc_action *act, int bind, int ref)
{
	struct tc_action *a;
	int err = -EINVAL;
	unsigned char *b = skb->tail;
	struct rtattr *r ;

	while ((a = act) != NULL) {
		r = (struct rtattr*) skb->tail;
		act = a->next;
		RTA_PUT(skb, a->order, 0, NULL);
		err = tcf_action_dump_1(skb, a, bind, ref);
		if (err < 0)
			goto errout;
		r->rta_len = skb->tail - (u8*)r;
	}

	return 0;

rtattr_failure:
	err = -EINVAL;
errout:
	skb_trim(skb, b - skb->data);
	return err;
}

struct tc_action *tcf_action_init_1(struct rtattr *rta, struct rtattr *est,
                                    char *name, int ovr, int bind, int *err)
{
	struct tc_action *a;
	struct tc_action_ops *a_o;
	char act_name[IFNAMSIZ];
	struct rtattr *tb[TCA_ACT_MAX+1];
	struct rtattr *kind;

	*err = -EINVAL;

	if (name == NULL) {
		if (rtattr_parse_nested(tb, TCA_ACT_MAX, rta) < 0)
			goto err_out;
		kind = tb[TCA_ACT_KIND-1];
		if (kind == NULL)
			goto err_out;
		if (rtattr_strlcpy(act_name, kind, IFNAMSIZ) >= IFNAMSIZ)
			goto err_out;
	} else {
		if (strlcpy(act_name, name, IFNAMSIZ) >= IFNAMSIZ)
			goto err_out;
	}

	a_o = tc_lookup_action_n(act_name);
	if (a_o == NULL) {
#ifdef CONFIG_KMOD
		rtnl_unlock();
		request_module("act_%s", act_name);
		rtnl_lock();

		a_o = tc_lookup_action_n(act_name);

		/* We dropped the RTNL semaphore in order to
		 * perform the module load.  So, even if we
		 * succeeded in loading the module we have to
		 * tell the caller to replay the request.  We
		 * indicate this using -EAGAIN.
		 */
		if (a_o != NULL) {
			*err = -EAGAIN;
			goto err_mod;
		}
#endif
		*err = -ENOENT;
		goto err_out;
	}

	*err = -ENOMEM;
	a = kmalloc(sizeof(*a), GFP_KERNEL);
	if (a == NULL)
		goto err_mod;
	memset(a, 0, sizeof(*a));

	/* backward compatibility for policer */
	if (name == NULL)
		*err = a_o->init(tb[TCA_ACT_OPTIONS-1], est, a, ovr, bind);
	else
		*err = a_o->init(rta, est, a, ovr, bind);
	if (*err < 0)
		goto err_free;

	/* module count goes up only when brand new policy is created
	   if it exists and is only bound to in a_o->init() then
	   ACT_P_CREATED is not returned (a zero is).
	*/
	if (*err != ACT_P_CREATED)
		module_put(a_o->owner);
	a->ops = a_o;
	DPRINTK("tcf_action_init_1: successfull %s\n", act_name);

	*err = 0;
	return a;

err_free:
	kfree(a);
err_mod:
	module_put(a_o->owner);
err_out:
	return NULL;
}

struct tc_action *tcf_action_init(struct rtattr *rta, struct rtattr *est,
                                  char *name, int ovr, int bind, int *err)
{
	struct rtattr *tb[TCA_ACT_MAX_PRIO+1];
	struct tc_action *head = NULL, *act, *act_prev = NULL;
	int i;

	if (rtattr_parse_nested(tb, TCA_ACT_MAX_PRIO, rta) < 0) {
		*err = -EINVAL;
		return head;
	}

	for (i=0; i < TCA_ACT_MAX_PRIO && tb[i]; i++) {
		act = tcf_action_init_1(tb[i], est, name, ovr, bind, err);
		if (act == NULL)
			goto err;
		act->order = i+1;

		if (head == NULL)
			head = act;
		else
			act_prev->next = act;
		act_prev = act;
	}
	return head;

err:
	if (head != NULL)
		tcf_action_destroy(head, bind);
	return NULL;
}

int tcf_action_copy_stats(struct sk_buff *skb, struct tc_action *a,
			  int compat_mode)
{
	int err = 0;
	struct gnet_dump d;
	struct tcf_act_hdr *h = a->priv;
	
	if (h == NULL)
		goto errout;

	/* compat_mode being true specifies a call that is supposed
	 * to add additional backward compatiblity statistic TLVs.
	 */
	if (compat_mode) {
		if (a->type == TCA_OLD_COMPAT)
			err = gnet_stats_start_copy_compat(skb, 0,
				TCA_STATS, TCA_XSTATS, h->stats_lock, &d);
		else
			return 0;
	} else
		err = gnet_stats_start_copy(skb, TCA_ACT_STATS,
			h->stats_lock, &d);

	if (err < 0)
		goto errout;

	if (a->ops != NULL && a->ops->get_stats != NULL)
		if (a->ops->get_stats(skb, a) < 0)
			goto errout;

	if (gnet_stats_copy_basic(&d, &h->bstats) < 0 ||
#ifdef CONFIG_NET_ESTIMATOR
	    gnet_stats_copy_rate_est(&d, &h->rate_est) < 0 ||
#endif
	    gnet_stats_copy_queue(&d, &h->qstats) < 0)
		goto errout;

	if (gnet_stats_finish_copy(&d) < 0)
		goto errout;

	return 0;

errout:
	return -1;
}

static int
tca_get_fill(struct sk_buff *skb, struct tc_action *a, u32 pid, u32 seq,
             u16 flags, int event, int bind, int ref)
{
	struct tcamsg *t;
	struct nlmsghdr *nlh;
	unsigned char *b = skb->tail;
	struct rtattr *x;

	nlh = NLMSG_NEW(skb, pid, seq, event, sizeof(*t), flags);

	t = NLMSG_DATA(nlh);
	t->tca_family = AF_UNSPEC;
	t->tca__pad1 = 0;
	t->tca__pad2 = 0;
	
	x = (struct rtattr*) skb->tail;
	RTA_PUT(skb, TCA_ACT_TAB, 0, NULL);

	if (tcf_action_dump(skb, a, bind, ref) < 0)
		goto rtattr_failure;

	x->rta_len = skb->tail - (u8*)x;
	
	nlh->nlmsg_len = skb->tail - b;
	return skb->len;

rtattr_failure:
nlmsg_failure:
	skb_trim(skb, b - skb->data);
	return -1;
}

static int
act_get_notify(u32 pid, struct nlmsghdr *n, struct tc_action *a, int event)
{
	struct sk_buff *skb;
	int err = 0;

	skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
	if (!skb)
		return -ENOBUFS;
	if (tca_get_fill(skb, a, pid, n->nlmsg_seq, 0, event, 0, 0) <= 0) {
		kfree_skb(skb);
		return -EINVAL;
	}
	err = netlink_unicast(rtnl, skb, pid, MSG_DONTWAIT);
	if (err > 0)
		err = 0;
	return err;
}

static struct tc_action *
tcf_action_get_1(struct rtattr *rta, struct nlmsghdr *n, u32 pid, int *err)
{
	struct rtattr *tb[TCA_ACT_MAX+1];
	struct tc_action *a;
	int index;

	*err = -EINVAL;
	if (rtattr_parse_nested(tb, TCA_ACT_MAX, rta) < 0)
		return NULL;

	if (tb[TCA_ACT_INDEX - 1] == NULL ||
	    RTA_PAYLOAD(tb[TCA_ACT_INDEX - 1]) < sizeof(index))
		return NULL;
	index = *(int *)RTA_DATA(tb[TCA_ACT_INDEX - 1]);

	*err = -ENOMEM;
	a = kmalloc(sizeof(struct tc_action), GFP_KERNEL);
	if (a == NULL)
		return NULL;
	memset(a, 0, sizeof(struct tc_action));

	*err = -EINVAL;
	a->ops = tc_lookup_action(tb[TCA_ACT_KIND - 1]);
	if (a->ops == NULL)
		goto err_free;
	if (a->ops->lookup == NULL)
		goto err_mod;
	*err = -ENOENT;
	if (a->ops->lookup(a, index) == 0)
		goto err_mod;

	module_put(a->ops->owner);
	*err = 0;
	return a;
err_mod:
	module_put(a->ops->owner);
err_free:
	kfree(a);
	return NULL;
}

static void cleanup_a(struct tc_action *act)
{
	struct tc_action *a;

	for (a = act; a; a = act) {
		act = a->next;
		kfree(a);
	}
}

static struct tc_action *create_a(int i)
{
	struct tc_action *act;

	act = kmalloc(sizeof(*act), GFP_KERNEL);
	if (act == NULL) {
		printk("create_a: failed to alloc!\n");
		return NULL;
	}
	memset(act, 0, sizeof(*act));
	act->order = i;
	return act;
}

static int tca_action_flush(struct rtattr *rta, struct nlmsghdr *n, u32 pid)
{
	struct sk_buff *skb;
	unsigned char *b;
	struct nlmsghdr *nlh;
	struct tcamsg *t;
	struct netlink_callback dcb;
	struct rtattr *x;
	struct rtattr *tb[TCA_ACT_MAX+1];
	struct rtattr *kind;
	struct tc_action *a = create_a(0);
	int err = -EINVAL;

	if (a == NULL) {
		printk("tca_action_flush: couldnt create tc_action\n");
		return err;
	}

	skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
	if (!skb) {
		printk("tca_action_flush: failed skb alloc\n");
		kfree(a);
		return -ENOBUFS;
	}

	b = (unsigned char *)skb->tail;

	if (rtattr_parse_nested(tb, TCA_ACT_MAX, rta) < 0)
		goto err_out;

	kind = tb[TCA_ACT_KIND-1];
	a->ops = tc_lookup_action(kind);
	if (a->ops == NULL)
		goto err_out;

	nlh = NLMSG_PUT(skb, pid, n->nlmsg_seq, RTM_DELACTION, sizeof(*t));
	t = NLMSG_DATA(nlh);
	t->tca_family = AF_UNSPEC;
	t->tca__pad1 = 0;
	t->tca__pad2 = 0;

	x = (struct rtattr *) skb->tail;
	RTA_PUT(skb, TCA_ACT_TAB, 0, NULL);

	err = a->ops->walk(skb, &dcb, RTM_DELACTION, a);
	if (err < 0)
		goto rtattr_failure;

	x->rta_len = skb->tail - (u8 *) x;

	nlh->nlmsg_len = skb->tail - b;
	nlh->nlmsg_flags |= NLM_F_ROOT;
	module_put(a->ops->owner);
	kfree(a);
	err = rtnetlink_send(skb, pid, RTNLGRP_TC, n->nlmsg_flags&NLM_F_ECHO);
	if (err > 0)
		return 0;

	return err;

rtattr_failure:
nlmsg_failure:
	module_put(a->ops->owner);
err_out:
	kfree_skb(skb);
	kfree(a);
	return err;
}

static int
tca_action_gd(struct rtattr *rta, struct nlmsghdr *n, u32 pid, int event)
{
	int i, ret = 0;
	struct rtattr *tb[TCA_ACT_MAX_PRIO+1];
	struct tc_action *head = NULL, *act, *act_prev = NULL;

	if (rtattr_parse_nested(tb, TCA_ACT_MAX_PRIO, rta) < 0)
		return -EINVAL;

	if (event == RTM_DELACTION && n->nlmsg_flags&NLM_F_ROOT) {
		if (tb[0] != NULL && tb[1] == NULL)
			return tca_action_flush(tb[0], n, pid);
	}

	for (i=0; i < TCA_ACT_MAX_PRIO && tb[i]; i++) {
		act = tcf_action_get_1(tb[i], n, pid, &ret);
		if (act == NULL)
			goto err;
		act->order = i+1;

		if (head == NULL)
			head = act;
		else
			act_prev->next = act;
		act_prev = act;
	}

	if (event == RTM_GETACTION)
		ret = act_get_notify(pid, n, head, event);
	else { /* delete */
		struct sk_buff *skb;

		skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
		if (!skb) {
			ret = -ENOBUFS;
			goto err;
		}

		if (tca_get_fill(skb, head, pid, n->nlmsg_seq, 0, event,
		                 0, 1) <= 0) {
			kfree_skb(skb);
			ret = -EINVAL;
			goto err;
		}

		/* now do the delete */
		tcf_action_destroy(head, 0);
		ret = rtnetlink_send(skb, pid, RTNLGRP_TC,
		                     n->nlmsg_flags&NLM_F_ECHO);
		if (ret > 0)
			return 0;
		return ret;
	}
err:
	cleanup_a(head);
	return ret;
}

static int tcf_add_notify(struct tc_action *a, u32 pid, u32 seq, int event,
                          u16 flags)
{
	struct tcamsg *t;
	struct nlmsghdr *nlh;
	struct sk_buff *skb;
	struct rtattr *x;
	unsigned char *b;
	int err = 0;

	skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
	if (!skb)
		return -ENOBUFS;

	b = (unsigned char *)skb->tail;

	nlh = NLMSG_NEW(skb, pid, seq, event, sizeof(*t), flags);
	t = NLMSG_DATA(nlh);
	t->tca_family = AF_UNSPEC;
	t->tca__pad1 = 0;
	t->tca__pad2 = 0;

	x = (struct rtattr*) skb->tail;
	RTA_PUT(skb, TCA_ACT_TAB, 0, NULL);

	if (tcf_action_dump(skb, a, 0, 0) < 0)
		goto rtattr_failure;

	x->rta_len = skb->tail - (u8*)x;
	
	nlh->nlmsg_len = skb->tail - b;
	NETLINK_CB(skb).dst_group = RTNLGRP_TC;
	
	err = rtnetlink_send(skb, pid, RTNLGRP_TC, flags&NLM_F_ECHO);
	if (err > 0)
		err = 0;
	return err;

rtattr_failure:
nlmsg_failure:
	kfree_skb(skb);
	return -1;
}

	
static int
tcf_action_add(struct rtattr *rta, struct nlmsghdr *n, u32 pid, int ovr)
{
	int ret = 0;
	struct tc_action *act;
	struct tc_action *a;
	u32 seq = n->nlmsg_seq;

	act = tcf_action_init(rta, NULL, NULL, ovr, 0, &ret);
	if (act == NULL)
		goto done;

	/* dump then free all the actions after update; inserted policy
	 * stays intact
	 * */
	ret = tcf_add_notify(act, pid, seq, RTM_NEWACTION, n->nlmsg_flags);
	for (a = act; a; a = act) {
		act = a->next;
		kfree(a);
	}
done:
	return ret;
}

static int tc_ctl_action(struct sk_buff *skb, struct nlmsghdr *n, void *arg)
{
	struct rtattr **tca = arg;
	u32 pid = skb ? NETLINK_CB(skb).pid : 0;
	int ret = 0, ovr = 0;

	if (tca[TCA_ACT_TAB-1] == NULL) {
		printk("tc_ctl_action: received NO action attribs\n");
		return -EINVAL;
	}

	/* n->nlmsg_flags&NLM_F_CREATE
	 * */
	switch (n->nlmsg_type) {
	case RTM_NEWACTION:
		/* we are going to assume all other flags
		 * imply create only if it doesnt exist
		 * Note that CREATE | EXCL implies that
		 * but since we want avoid ambiguity (eg when flags
		 * is zero) then just set this
		 */
		if (n->nlmsg_flags&NLM_F_REPLACE)
			ovr = 1;
replay:
		ret = tcf_action_add(tca[TCA_ACT_TAB-1], n, pid, ovr);
		if (ret == -EAGAIN)
			goto replay;
		break;
	case RTM_DELACTION:
		ret = tca_action_gd(tca[TCA_ACT_TAB-1], n, pid, RTM_DELACTION);
		break;
	case RTM_GETACTION:
		ret = tca_action_gd(tca[TCA_ACT_TAB-1], n, pid, RTM_GETACTION);
		break;
	default:
		BUG();
	}

	return ret;
}

static struct rtattr *
find_dump_kind(struct nlmsghdr *n)
{
	struct rtattr *tb1, *tb2[TCA_ACT_MAX+1];
	struct rtattr *tb[TCA_ACT_MAX_PRIO + 1];
	struct rtattr *rta[TCAA_MAX + 1];
	struct rtattr *kind;
	int min_len = NLMSG_LENGTH(sizeof(struct tcamsg));
	int attrlen = n->nlmsg_len - NLMSG_ALIGN(min_len);
	struct rtattr *attr = (void *) n + NLMSG_ALIGN(min_len);

	if (rtattr_parse(rta, TCAA_MAX, attr, attrlen) < 0)
		return NULL;
	tb1 = rta[TCA_ACT_TAB - 1];
	if (tb1 == NULL)
		return NULL;

	if (rtattr_parse(tb, TCA_ACT_MAX_PRIO, RTA_DATA(tb1),
	                 NLMSG_ALIGN(RTA_PAYLOAD(tb1))) < 0)
		return NULL;
	if (tb[0] == NULL)
		return NULL;

	if (rtattr_parse(tb2, TCA_ACT_MAX, RTA_DATA(tb[0]),
	                 RTA_PAYLOAD(tb[0])) < 0)
		return NULL;
	kind = tb2[TCA_ACT_KIND-1];

	return kind;
}

static int
tc_dump_action(struct sk_buff *skb, struct netlink_callback *cb)
{
	struct nlmsghdr *nlh;
	unsigned char *b = skb->tail;
	struct rtattr *x;
	struct tc_action_ops *a_o;
	struct tc_action a;
	int ret = 0;
	struct tcamsg *t = (struct tcamsg *) NLMSG_DATA(cb->nlh);
	struct rtattr *kind = find_dump_kind(cb->nlh);

	if (kind == NULL) {
		printk("tc_dump_action: action bad kind\n");
		return 0;
	}

	a_o = tc_lookup_action(kind);
	if (a_o == NULL) {
		return 0;
	}

	memset(&a, 0, sizeof(struct tc_action));
	a.ops = a_o;

	if (a_o->walk == NULL) {
		printk("tc_dump_action: %s !capable of dumping table\n", a_o->kind);
		goto rtattr_failure;
	}

	nlh = NLMSG_PUT(skb, NETLINK_CB(cb->skb).pid, cb->nlh->nlmsg_seq,
	                cb->nlh->nlmsg_type, sizeof(*t));
	t = NLMSG_DATA(nlh);
	t->tca_family = AF_UNSPEC;
	t->tca__pad1 = 0;
	t->tca__pad2 = 0;

	x = (struct rtattr *) skb->tail;
	RTA_PUT(skb, TCA_ACT_TAB, 0, NULL);

	ret = a_o->walk(skb, cb, RTM_GETACTION, &a);
	if (ret < 0)
		goto rtattr_failure;

	if (ret > 0) {
		x->rta_len = skb->tail - (u8 *) x;
		ret = skb->len;
	} else
		skb_trim(skb, (u8*)x - skb->data);

	nlh->nlmsg_len = skb->tail - b;
	if (NETLINK_CB(cb->skb).pid && ret)
		nlh->nlmsg_flags |= NLM_F_MULTI;
	module_put(a_o->owner);
	return skb->len;

rtattr_failure:
nlmsg_failure:
	module_put(a_o->owner);
	skb_trim(skb, b - skb->data);
	return skb->len;
}

static int __init tc_action_init(void)
{
	struct rtnetlink_link *link_p = rtnetlink_links[PF_UNSPEC];

	if (link_p) {
		link_p[RTM_NEWACTION-RTM_BASE].doit = tc_ctl_action;
		link_p[RTM_DELACTION-RTM_BASE].doit = tc_ctl_action;
		link_p[RTM_GETACTION-RTM_BASE].doit = tc_ctl_action;
		link_p[RTM_GETACTION-RTM_BASE].dumpit = tc_dump_action;
	}

	return 0;
}

subsys_initcall(tc_action_init);

EXPORT_SYMBOL(tcf_register_action);
EXPORT_SYMBOL(tcf_unregister_action);
EXPORT_SYMBOL(tcf_action_exec);
EXPORT_SYMBOL(tcf_action_dump_1);