act_csum.c 13.8 KB
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/*
 * Checksum updating actions
 *
 * Copyright (c) 2010 Gregoire Baron <baronchon@n7mm.org>
 *
 * 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.
 *
 */

#include <linux/types.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/spinlock.h>

#include <linux/netlink.h>
#include <net/netlink.h>
#include <linux/rtnetlink.h>

#include <linux/skbuff.h>

#include <net/ip.h>
#include <net/ipv6.h>
#include <net/icmp.h>
#include <linux/icmpv6.h>
#include <linux/igmp.h>
#include <net/tcp.h>
#include <net/udp.h>
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#include <net/ip6_checksum.h>
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#include <net/act_api.h>

#include <linux/tc_act/tc_csum.h>
#include <net/tc_act/tc_csum.h>

#define CSUM_TAB_MASK 15

static const struct nla_policy csum_policy[TCA_CSUM_MAX + 1] = {
	[TCA_CSUM_PARMS] = { .len = sizeof(struct tc_csum), },
};

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static unsigned int csum_net_id;
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static struct tc_action_ops act_csum_ops;
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static int tcf_csum_init(struct net *net, struct nlattr *nla,
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			 struct nlattr *est, struct tc_action **a, int ovr,
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			 int bind)
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{
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	struct tc_action_net *tn = net_generic(net, csum_net_id);
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	struct nlattr *tb[TCA_CSUM_MAX + 1];
	struct tc_csum *parm;
	struct tcf_csum *p;
	int ret = 0, err;

	if (nla == NULL)
		return -EINVAL;

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	err = nla_parse_nested(tb, TCA_CSUM_MAX, nla, csum_policy);
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	if (err < 0)
		return err;

	if (tb[TCA_CSUM_PARMS] == NULL)
		return -EINVAL;
	parm = nla_data(tb[TCA_CSUM_PARMS]);

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	if (!tcf_hash_check(tn, parm->index, a, bind)) {
		ret = tcf_hash_create(tn, parm->index, est, a,
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				      &act_csum_ops, bind, false);
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		if (ret)
			return ret;
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		ret = ACT_P_CREATED;
	} else {
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		if (bind)/* dont override defaults */
			return 0;
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		tcf_hash_release(*a, bind);
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		if (!ovr)
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			return -EEXIST;
	}

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	p = to_tcf_csum(*a);
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	spin_lock_bh(&p->tcf_lock);
	p->tcf_action = parm->action;
	p->update_flags = parm->update_flags;
	spin_unlock_bh(&p->tcf_lock);

	if (ret == ACT_P_CREATED)
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		tcf_hash_insert(tn, *a);
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	return ret;
}

/**
 * tcf_csum_skb_nextlayer - Get next layer pointer
 * @skb: sk_buff to use
 * @ihl: previous summed headers length
 * @ipl: complete packet length
 * @jhl: next header length
 *
 * Check the expected next layer availability in the specified sk_buff.
 * Return the next layer pointer if pass, NULL otherwise.
 */
static void *tcf_csum_skb_nextlayer(struct sk_buff *skb,
				    unsigned int ihl, unsigned int ipl,
				    unsigned int jhl)
{
	int ntkoff = skb_network_offset(skb);
	int hl = ihl + jhl;

	if (!pskb_may_pull(skb, ipl + ntkoff) || (ipl < hl) ||
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	    skb_try_make_writable(skb, hl + ntkoff))
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		return NULL;
	else
		return (void *)(skb_network_header(skb) + ihl);
}

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static int tcf_csum_ipv4_icmp(struct sk_buff *skb, unsigned int ihl,
			      unsigned int ipl)
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{
	struct icmphdr *icmph;

	icmph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*icmph));
	if (icmph == NULL)
		return 0;

	icmph->checksum = 0;
	skb->csum = csum_partial(icmph, ipl - ihl, 0);
	icmph->checksum = csum_fold(skb->csum);

	skb->ip_summed = CHECKSUM_NONE;

	return 1;
}

static int tcf_csum_ipv4_igmp(struct sk_buff *skb,
			      unsigned int ihl, unsigned int ipl)
{
	struct igmphdr *igmph;

	igmph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*igmph));
	if (igmph == NULL)
		return 0;

	igmph->csum = 0;
	skb->csum = csum_partial(igmph, ipl - ihl, 0);
	igmph->csum = csum_fold(skb->csum);

	skb->ip_summed = CHECKSUM_NONE;

	return 1;
}

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static int tcf_csum_ipv6_icmp(struct sk_buff *skb, unsigned int ihl,
			      unsigned int ipl)
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{
	struct icmp6hdr *icmp6h;
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	const struct ipv6hdr *ip6h;
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	icmp6h = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*icmp6h));
	if (icmp6h == NULL)
		return 0;

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	ip6h = ipv6_hdr(skb);
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	icmp6h->icmp6_cksum = 0;
	skb->csum = csum_partial(icmp6h, ipl - ihl, 0);
	icmp6h->icmp6_cksum = csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
					      ipl - ihl, IPPROTO_ICMPV6,
					      skb->csum);

	skb->ip_summed = CHECKSUM_NONE;

	return 1;
}

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static int tcf_csum_ipv4_tcp(struct sk_buff *skb, unsigned int ihl,
			     unsigned int ipl)
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{
	struct tcphdr *tcph;
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	const struct iphdr *iph;
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	tcph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*tcph));
	if (tcph == NULL)
		return 0;

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	iph = ip_hdr(skb);
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	tcph->check = 0;
	skb->csum = csum_partial(tcph, ipl - ihl, 0);
	tcph->check = tcp_v4_check(ipl - ihl,
				   iph->saddr, iph->daddr, skb->csum);

	skb->ip_summed = CHECKSUM_NONE;

	return 1;
}

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static int tcf_csum_ipv6_tcp(struct sk_buff *skb, unsigned int ihl,
			     unsigned int ipl)
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{
	struct tcphdr *tcph;
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	const struct ipv6hdr *ip6h;
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	tcph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*tcph));
	if (tcph == NULL)
		return 0;

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	ip6h = ipv6_hdr(skb);
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	tcph->check = 0;
	skb->csum = csum_partial(tcph, ipl - ihl, 0);
	tcph->check = csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
				      ipl - ihl, IPPROTO_TCP,
				      skb->csum);

	skb->ip_summed = CHECKSUM_NONE;

	return 1;
}

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static int tcf_csum_ipv4_udp(struct sk_buff *skb, unsigned int ihl,
			     unsigned int ipl, int udplite)
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{
	struct udphdr *udph;
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	const struct iphdr *iph;
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	u16 ul;

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	/*
	 * Support both UDP and UDPLITE checksum algorithms, Don't use
	 * udph->len to get the real length without any protocol check,
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	 * UDPLITE uses udph->len for another thing,
	 * Use iph->tot_len, or just ipl.
	 */

	udph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*udph));
	if (udph == NULL)
		return 0;

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	iph = ip_hdr(skb);
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	ul = ntohs(udph->len);

	if (udplite || udph->check) {

		udph->check = 0;

		if (udplite) {
			if (ul == 0)
				skb->csum = csum_partial(udph, ipl - ihl, 0);
			else if ((ul >= sizeof(*udph)) && (ul <= ipl - ihl))
				skb->csum = csum_partial(udph, ul, 0);
			else
				goto ignore_obscure_skb;
		} else {
			if (ul != ipl - ihl)
				goto ignore_obscure_skb;

			skb->csum = csum_partial(udph, ul, 0);
		}

		udph->check = csum_tcpudp_magic(iph->saddr, iph->daddr,
						ul, iph->protocol,
						skb->csum);

		if (!udph->check)
			udph->check = CSUM_MANGLED_0;
	}

	skb->ip_summed = CHECKSUM_NONE;

ignore_obscure_skb:
	return 1;
}

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static int tcf_csum_ipv6_udp(struct sk_buff *skb, unsigned int ihl,
			     unsigned int ipl, int udplite)
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{
	struct udphdr *udph;
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	const struct ipv6hdr *ip6h;
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	u16 ul;

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	/*
	 * Support both UDP and UDPLITE checksum algorithms, Don't use
	 * udph->len to get the real length without any protocol check,
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	 * UDPLITE uses udph->len for another thing,
	 * Use ip6h->payload_len + sizeof(*ip6h) ... , or just ipl.
	 */

	udph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*udph));
	if (udph == NULL)
		return 0;

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	ip6h = ipv6_hdr(skb);
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	ul = ntohs(udph->len);

	udph->check = 0;

	if (udplite) {
		if (ul == 0)
			skb->csum = csum_partial(udph, ipl - ihl, 0);

		else if ((ul >= sizeof(*udph)) && (ul <= ipl - ihl))
			skb->csum = csum_partial(udph, ul, 0);

		else
			goto ignore_obscure_skb;
	} else {
		if (ul != ipl - ihl)
			goto ignore_obscure_skb;

		skb->csum = csum_partial(udph, ul, 0);
	}

	udph->check = csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr, ul,
				      udplite ? IPPROTO_UDPLITE : IPPROTO_UDP,
				      skb->csum);

	if (!udph->check)
		udph->check = CSUM_MANGLED_0;

	skb->ip_summed = CHECKSUM_NONE;

ignore_obscure_skb:
	return 1;
}

static int tcf_csum_ipv4(struct sk_buff *skb, u32 update_flags)
{
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	const struct iphdr *iph;
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	int ntkoff;

	ntkoff = skb_network_offset(skb);

	if (!pskb_may_pull(skb, sizeof(*iph) + ntkoff))
		goto fail;

	iph = ip_hdr(skb);

	switch (iph->frag_off & htons(IP_OFFSET) ? 0 : iph->protocol) {
	case IPPROTO_ICMP:
		if (update_flags & TCA_CSUM_UPDATE_FLAG_ICMP)
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			if (!tcf_csum_ipv4_icmp(skb, iph->ihl * 4,
						ntohs(iph->tot_len)))
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				goto fail;
		break;
	case IPPROTO_IGMP:
		if (update_flags & TCA_CSUM_UPDATE_FLAG_IGMP)
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			if (!tcf_csum_ipv4_igmp(skb, iph->ihl * 4,
						ntohs(iph->tot_len)))
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				goto fail;
		break;
	case IPPROTO_TCP:
		if (update_flags & TCA_CSUM_UPDATE_FLAG_TCP)
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			if (!tcf_csum_ipv4_tcp(skb, iph->ihl * 4,
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					       ntohs(iph->tot_len)))
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				goto fail;
		break;
	case IPPROTO_UDP:
		if (update_flags & TCA_CSUM_UPDATE_FLAG_UDP)
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			if (!tcf_csum_ipv4_udp(skb, iph->ihl * 4,
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					       ntohs(iph->tot_len), 0))
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				goto fail;
		break;
	case IPPROTO_UDPLITE:
		if (update_flags & TCA_CSUM_UPDATE_FLAG_UDPLITE)
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			if (!tcf_csum_ipv4_udp(skb, iph->ihl * 4,
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					       ntohs(iph->tot_len), 1))
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				goto fail;
		break;
	}

	if (update_flags & TCA_CSUM_UPDATE_FLAG_IPV4HDR) {
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		if (skb_try_make_writable(skb, sizeof(*iph) + ntkoff))
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			goto fail;

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		ip_send_check(ip_hdr(skb));
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	}

	return 1;

fail:
	return 0;
}

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static int tcf_csum_ipv6_hopopts(struct ipv6_opt_hdr *ip6xh, unsigned int ixhl,
				 unsigned int *pl)
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{
	int off, len, optlen;
	unsigned char *xh = (void *)ip6xh;

	off = sizeof(*ip6xh);
	len = ixhl - off;

	while (len > 1) {
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		switch (xh[off]) {
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		case IPV6_TLV_PAD1:
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			optlen = 1;
			break;
		case IPV6_TLV_JUMBO:
			optlen = xh[off + 1] + 2;
			if (optlen != 6 || len < 6 || (off & 3) != 2)
				/* wrong jumbo option length/alignment */
				return 0;
			*pl = ntohl(*(__be32 *)(xh + off + 2));
			goto done;
		default:
			optlen = xh[off + 1] + 2;
			if (optlen > len)
				/* ignore obscure options */
				goto done;
			break;
		}
		off += optlen;
		len -= optlen;
	}

done:
	return 1;
}

static int tcf_csum_ipv6(struct sk_buff *skb, u32 update_flags)
{
	struct ipv6hdr *ip6h;
	struct ipv6_opt_hdr *ip6xh;
	unsigned int hl, ixhl;
	unsigned int pl;
	int ntkoff;
	u8 nexthdr;

	ntkoff = skb_network_offset(skb);

	hl = sizeof(*ip6h);

	if (!pskb_may_pull(skb, hl + ntkoff))
		goto fail;

	ip6h = ipv6_hdr(skb);

	pl = ntohs(ip6h->payload_len);
	nexthdr = ip6h->nexthdr;

	do {
		switch (nexthdr) {
		case NEXTHDR_FRAGMENT:
			goto ignore_skb;
		case NEXTHDR_ROUTING:
		case NEXTHDR_HOP:
		case NEXTHDR_DEST:
			if (!pskb_may_pull(skb, hl + sizeof(*ip6xh) + ntkoff))
				goto fail;
			ip6xh = (void *)(skb_network_header(skb) + hl);
			ixhl = ipv6_optlen(ip6xh);
			if (!pskb_may_pull(skb, hl + ixhl + ntkoff))
				goto fail;
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			ip6xh = (void *)(skb_network_header(skb) + hl);
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			if ((nexthdr == NEXTHDR_HOP) &&
			    !(tcf_csum_ipv6_hopopts(ip6xh, ixhl, &pl)))
				goto fail;
			nexthdr = ip6xh->nexthdr;
			hl += ixhl;
			break;
		case IPPROTO_ICMPV6:
			if (update_flags & TCA_CSUM_UPDATE_FLAG_ICMP)
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				if (!tcf_csum_ipv6_icmp(skb,
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							hl, pl + sizeof(*ip6h)))
					goto fail;
			goto done;
		case IPPROTO_TCP:
			if (update_flags & TCA_CSUM_UPDATE_FLAG_TCP)
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				if (!tcf_csum_ipv6_tcp(skb,
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						       hl, pl + sizeof(*ip6h)))
					goto fail;
			goto done;
		case IPPROTO_UDP:
			if (update_flags & TCA_CSUM_UPDATE_FLAG_UDP)
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				if (!tcf_csum_ipv6_udp(skb, hl,
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						       pl + sizeof(*ip6h), 0))
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					goto fail;
			goto done;
		case IPPROTO_UDPLITE:
			if (update_flags & TCA_CSUM_UPDATE_FLAG_UDPLITE)
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				if (!tcf_csum_ipv6_udp(skb, hl,
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						       pl + sizeof(*ip6h), 1))
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					goto fail;
			goto done;
		default:
			goto ignore_skb;
		}
	} while (pskb_may_pull(skb, hl + 1 + ntkoff));

done:
ignore_skb:
	return 1;

fail:
	return 0;
}

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static int tcf_csum(struct sk_buff *skb, const struct tc_action *a,
		    struct tcf_result *res)
499
{
500
	struct tcf_csum *p = to_tcf_csum(a);
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	int action;
	u32 update_flags;

	spin_lock(&p->tcf_lock);
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	tcf_lastuse_update(&p->tcf_tm);
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	bstats_update(&p->tcf_bstats, skb);
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	action = p->tcf_action;
	update_flags = p->update_flags;
	spin_unlock(&p->tcf_lock);

	if (unlikely(action == TC_ACT_SHOT))
		goto drop;

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	switch (tc_skb_protocol(skb)) {
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	case cpu_to_be16(ETH_P_IP):
		if (!tcf_csum_ipv4(skb, update_flags))
			goto drop;
		break;
	case cpu_to_be16(ETH_P_IPV6):
		if (!tcf_csum_ipv6(skb, update_flags))
			goto drop;
		break;
	}

	return action;

drop:
	spin_lock(&p->tcf_lock);
	p->tcf_qstats.drops++;
	spin_unlock(&p->tcf_lock);
	return TC_ACT_SHOT;
}

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static int tcf_csum_dump(struct sk_buff *skb, struct tc_action *a, int bind,
			 int ref)
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{
	unsigned char *b = skb_tail_pointer(skb);
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	struct tcf_csum *p = to_tcf_csum(a);
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	struct tc_csum opt = {
		.update_flags = p->update_flags,
		.index   = p->tcf_index,
		.action  = p->tcf_action,
		.refcnt  = p->tcf_refcnt - ref,
		.bindcnt = p->tcf_bindcnt - bind,
	};
	struct tcf_t t;

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	if (nla_put(skb, TCA_CSUM_PARMS, sizeof(opt), &opt))
		goto nla_put_failure;
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	tcf_tm_dump(&t, &p->tcf_tm);
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	if (nla_put_64bit(skb, TCA_CSUM_TM, sizeof(t), &t, TCA_CSUM_PAD))
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		goto nla_put_failure;
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	return skb->len;

nla_put_failure:
	nlmsg_trim(skb, b);
	return -1;
}

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static int tcf_csum_walker(struct net *net, struct sk_buff *skb,
			   struct netlink_callback *cb, int type,
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			   const struct tc_action_ops *ops)
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{
	struct tc_action_net *tn = net_generic(net, csum_net_id);

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	return tcf_generic_walker(tn, skb, cb, type, ops);
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}

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static int tcf_csum_search(struct net *net, struct tc_action **a, u32 index)
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{
	struct tc_action_net *tn = net_generic(net, csum_net_id);

	return tcf_hash_search(tn, a, index);
}

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static struct tc_action_ops act_csum_ops = {
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	.kind		= "csum",
	.type		= TCA_ACT_CSUM,
	.owner		= THIS_MODULE,
	.act		= tcf_csum,
	.dump		= tcf_csum_dump,
	.init		= tcf_csum_init,
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	.walk		= tcf_csum_walker,
	.lookup		= tcf_csum_search,
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	.size		= sizeof(struct tcf_csum),
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};

static __net_init int csum_init_net(struct net *net)
{
	struct tc_action_net *tn = net_generic(net, csum_net_id);

	return tc_action_net_init(tn, &act_csum_ops, CSUM_TAB_MASK);
}

static void __net_exit csum_exit_net(struct net *net)
{
	struct tc_action_net *tn = net_generic(net, csum_net_id);

	tc_action_net_exit(tn);
}

static struct pernet_operations csum_net_ops = {
	.init = csum_init_net,
	.exit = csum_exit_net,
	.id   = &csum_net_id,
	.size = sizeof(struct tc_action_net),
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};

MODULE_DESCRIPTION("Checksum updating actions");
MODULE_LICENSE("GPL");

static int __init csum_init_module(void)
{
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	return tcf_register_action(&act_csum_ops, &csum_net_ops);
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}

static void __exit csum_cleanup_module(void)
{
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	tcf_unregister_action(&act_csum_ops, &csum_net_ops);
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}

module_init(csum_init_module);
module_exit(csum_cleanup_module);