net/netfilter/nft_exthdr.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
  *
  * Development of this code funded by Astaro AG (http://www.astaro.com/)
  */

 #include <asm/unaligned.h>
 #include <linux/kernel.h>
 #include <linux/netlink.h>
 #include <linux/netfilter.h>
 #include <linux/netfilter/nf_tables.h>
 #include <net/netfilter/nf_tables_core.h>
 #include <net/netfilter/nf_tables.h>
 #include <net/tcp.h>

 struct nft_exthdr {
 	u8			type;
 	u8			offset;
 	u8			len;
 	u8			op;
 	enum nft_registers	dreg:8;
 	enum nft_registers	sreg:8;
 	u8			flags;
 };

 static unsigned int optlen(const u8 *opt, unsigned int offset)
 {
 	/* Beware zero-length options: make finite progress */
 	if (opt[offset] <= TCPOPT_NOP || opt[offset + 1] == 0)
 		return 1;
 	else
 		return opt[offset + 1];
 }

 static void nft_exthdr_ipv6_eval(const struct nft_expr *expr,
 				 struct nft_regs *regs,
 				 const struct nft_pktinfo *pkt)
 {
 	struct nft_exthdr *priv = nft_expr_priv(expr);
 	u32 *dest = &regs->data[priv->dreg];
 	unsigned int offset = 0;
 	int err;

 	err = ipv6_find_hdr(pkt->skb, &offset, priv->type, NULL, NULL);
 	if (priv->flags & NFT_EXTHDR_F_PRESENT) {
 		nft_reg_store8(dest, err >= 0);
 		return;
 	} else if (err < 0) {
 		goto err;
 	}
 	offset += priv->offset;

 	dest[priv->len / NFT_REG32_SIZE] = 0;
 	if (skb_copy_bits(pkt->skb, offset, dest, priv->len) < 0)
 		goto err;
 	return;
 err:
 	regs->verdict.code = NFT_BREAK;
 }

 /* find the offset to specified option.
  *
  * If target header is found, its offset is set in *offset and return option
  * number. Otherwise, return negative error.
  *
  * If the first fragment doesn't contain the End of Options it is considered
  * invalid.
  */
 static int ipv4_find_option(struct net *net, struct sk_buff *skb,
 			    unsigned int *offset, int target)
 {
 	unsigned char optbuf[sizeof(struct ip_options) + 40];
 	struct ip_options *opt = (struct ip_options *)optbuf;
 	struct iphdr *iph, _iph;
 	unsigned int start;
 	bool found = false;
 	__be32 info;
 	int optlen;

 	iph = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
 	if (!iph)
 		return -EBADMSG;
 	start = sizeof(struct iphdr);

 	optlen = iph->ihl * 4 - (int)sizeof(struct iphdr);
 	if (optlen <= 0)
 		return -ENOENT;

 	memset(opt, 0, sizeof(struct ip_options));
 	/* Copy the options since __ip_options_compile() modifies
 	 * the options.
 	 */
 	if (skb_copy_bits(skb, start, opt->__data, optlen))
 		return -EBADMSG;
 	opt->optlen = optlen;

 	if (__ip_options_compile(net, opt, NULL, &info))
 		return -EBADMSG;

 	switch (target) {
 	case IPOPT_SSRR:
 	case IPOPT_LSRR:
 		if (!opt->srr)
 			break;
 		found = target == IPOPT_SSRR ? opt->is_strictroute :
 					       !opt->is_strictroute;
 		if (found)
 			*offset = opt->srr + start;
 		break;
 	case IPOPT_RR:
 		if (!opt->rr)
 			break;
 		*offset = opt->rr + start;
 		found = true;
 		break;
 	case IPOPT_RA:
 		if (!opt->router_alert)
 			break;
 		*offset = opt->router_alert + start;
 		found = true;
 		break;
 	default:
 		return -EOPNOTSUPP;
 	}
 	return found ? target : -ENOENT;
 }

 static void nft_exthdr_ipv4_eval(const struct nft_expr *expr,
 				 struct nft_regs *regs,
 				 const struct nft_pktinfo *pkt)
 {
 	struct nft_exthdr *priv = nft_expr_priv(expr);
 	u32 *dest = &regs->data[priv->dreg];
 	struct sk_buff *skb = pkt->skb;
 	unsigned int offset;
 	int err;

 	if (skb->protocol != htons(ETH_P_IP))
 		goto err;

 	err = ipv4_find_option(nft_net(pkt), skb, &offset, priv->type);
 	if (priv->flags & NFT_EXTHDR_F_PRESENT) {
 		nft_reg_store8(dest, err >= 0);
 		return;
 	} else if (err < 0) {
 		goto err;
 	}
 	offset += priv->offset;

 	dest[priv->len / NFT_REG32_SIZE] = 0;
 	if (skb_copy_bits(pkt->skb, offset, dest, priv->len) < 0)
 		goto err;
 	return;
 err:
 	regs->verdict.code = NFT_BREAK;
 }

 static void *
 nft_tcp_header_pointer(const struct nft_pktinfo *pkt,
 		       unsigned int len, void *buffer, unsigned int *tcphdr_len)
 {
 	struct tcphdr *tcph;

 	if (!pkt->tprot_set || pkt->tprot != IPPROTO_TCP)
 		return NULL;

 	tcph = skb_header_pointer(pkt->skb, pkt->xt.thoff, sizeof(*tcph), buffer);
 	if (!tcph)
 		return NULL;

 	*tcphdr_len = __tcp_hdrlen(tcph);
 	if (*tcphdr_len < sizeof(*tcph) || *tcphdr_len > len)
 		return NULL;

 	return skb_header_pointer(pkt->skb, pkt->xt.thoff, *tcphdr_len, buffer);
 }

 static void nft_exthdr_tcp_eval(const struct nft_expr *expr,
 				struct nft_regs *regs,
 				const struct nft_pktinfo *pkt)
 {
 	u8 buff[sizeof(struct tcphdr) + MAX_TCP_OPTION_SPACE];
 	struct nft_exthdr *priv = nft_expr_priv(expr);
 	unsigned int i, optl, tcphdr_len, offset;
 	u32 *dest = &regs->data[priv->dreg];
 	struct tcphdr *tcph;
 	u8 *opt;

 	tcph = nft_tcp_header_pointer(pkt, sizeof(buff), buff, &tcphdr_len);
 	if (!tcph)
 		goto err;

 	opt = (u8 *)tcph;
 	for (i = sizeof(*tcph); i < tcphdr_len - 1; i += optl) {
 		optl = optlen(opt, i);

 		if (priv->type != opt[i])
 			continue;

 		if (i + optl > tcphdr_len || priv->len + priv->offset > optl)
 			goto err;

 		offset = i + priv->offset;
 		if (priv->flags & NFT_EXTHDR_F_PRESENT) {
 			*dest = 1;
 		} else {
 			dest[priv->len / NFT_REG32_SIZE] = 0;
 			memcpy(dest, opt + offset, priv->len);
 		}

 		return;
 	}

 err:
 	if (priv->flags & NFT_EXTHDR_F_PRESENT)
 		*dest = 0;
 	else
 		regs->verdict.code = NFT_BREAK;
 }

 static void nft_exthdr_tcp_set_eval(const struct nft_expr *expr,
 				    struct nft_regs *regs,
 				    const struct nft_pktinfo *pkt)
 {
 	u8 buff[sizeof(struct tcphdr) + MAX_TCP_OPTION_SPACE];
 	struct nft_exthdr *priv = nft_expr_priv(expr);
 	unsigned int i, optl, tcphdr_len, offset;
 	struct tcphdr *tcph;
 	u8 *opt;

 	tcph = nft_tcp_header_pointer(pkt, sizeof(buff), buff, &tcphdr_len);
 	if (!tcph)
 		return;

 	opt = (u8 *)tcph;
 	for (i = sizeof(*tcph); i < tcphdr_len - 1; i += optl) {
 		union {
 			__be16 v16;
 			__be32 v32;
 		} old, new;

 		optl = optlen(opt, i);

 		if (priv->type != opt[i])
 			continue;

 		if (i + optl > tcphdr_len || priv->len + priv->offset > optl)
 			return;

 		if (skb_ensure_writable(pkt->skb,
 					pkt->xt.thoff + i + priv->len))
 			return;

 		tcph = nft_tcp_header_pointer(pkt, sizeof(buff), buff,
 					      &tcphdr_len);
 		if (!tcph)
 			return;

 		offset = i + priv->offset;

 		switch (priv->len) {
 		case 2:
 			old.v16 = get_unaligned((u16 *)(opt + offset));
 			new.v16 = (__force __be16)nft_reg_load16(
 				&regs->data[priv->sreg]);

 			switch (priv->type) {
 			case TCPOPT_MSS:
 				/* increase can cause connection to stall */
 				if (ntohs(old.v16) <= ntohs(new.v16))
 					return;
 			break;
 			}

 			if (old.v16 == new.v16)
 				return;

 			put_unaligned(new.v16, (u16*)(opt + offset));
 			inet_proto_csum_replace2(&tcph->check, pkt->skb,
 						 old.v16, new.v16, false);
 			break;
 		case 4:
 			new.v32 = regs->data[priv->sreg];
 			old.v32 = get_unaligned((u32 *)(opt + offset));

 			if (old.v32 == new.v32)
 				return;

 			put_unaligned(new.v32, (u32*)(opt + offset));
 			inet_proto_csum_replace4(&tcph->check, pkt->skb,
 						 old.v32, new.v32, false);
 			break;
 		default:
 			WARN_ON_ONCE(1);
 			break;
 		}

 		return;
 	}
 }

 static const struct nla_policy nft_exthdr_policy[NFTA_EXTHDR_MAX + 1] = {
 	[NFTA_EXTHDR_DREG]		= { .type = NLA_U32 },
 	[NFTA_EXTHDR_TYPE]		= { .type = NLA_U8 },
 	[NFTA_EXTHDR_OFFSET]		= { .type = NLA_U32 },
 	[NFTA_EXTHDR_LEN]		= { .type = NLA_U32 },
 	[NFTA_EXTHDR_FLAGS]		= { .type = NLA_U32 },
 	[NFTA_EXTHDR_OP]		= { .type = NLA_U32 },
 	[NFTA_EXTHDR_SREG]		= { .type = NLA_U32 },
 };

 static int nft_exthdr_init(const struct nft_ctx *ctx,
 			   const struct nft_expr *expr,
 			   const struct nlattr * const tb[])
 {
 	struct nft_exthdr *priv = nft_expr_priv(expr);
 	u32 offset, len, flags = 0, op = NFT_EXTHDR_OP_IPV6;
 	int err;

 	if (!tb[NFTA_EXTHDR_DREG] ||
 	    !tb[NFTA_EXTHDR_TYPE] ||
 	    !tb[NFTA_EXTHDR_OFFSET] ||
 	    !tb[NFTA_EXTHDR_LEN])
 		return -EINVAL;

 	err = nft_parse_u32_check(tb[NFTA_EXTHDR_OFFSET], U8_MAX, &offset);
 	if (err < 0)
 		return err;

 	err = nft_parse_u32_check(tb[NFTA_EXTHDR_LEN], U8_MAX, &len);
 	if (err < 0)
 		return err;

 	if (tb[NFTA_EXTHDR_FLAGS]) {
 		err = nft_parse_u32_check(tb[NFTA_EXTHDR_FLAGS], U8_MAX, &flags);
 		if (err < 0)
 			return err;

 		if (flags & ~NFT_EXTHDR_F_PRESENT)
 			return -EINVAL;
 	}

 	if (tb[NFTA_EXTHDR_OP]) {
 		err = nft_parse_u32_check(tb[NFTA_EXTHDR_OP], U8_MAX, &op);
 		if (err < 0)
 			return err;
 	}

 	priv->type   = nla_get_u8(tb[NFTA_EXTHDR_TYPE]);
 	priv->offset = offset;
 	priv->len    = len;
 	priv->dreg   = nft_parse_register(tb[NFTA_EXTHDR_DREG]);
 	priv->flags  = flags;
 	priv->op     = op;

 	return nft_validate_register_store(ctx, priv->dreg, NULL,
 					   NFT_DATA_VALUE, priv->len);
 }

 static int nft_exthdr_tcp_set_init(const struct nft_ctx *ctx,
 				   const struct nft_expr *expr,
 				   const struct nlattr * const tb[])
 {
 	struct nft_exthdr *priv = nft_expr_priv(expr);
 	u32 offset, len, flags = 0, op = NFT_EXTHDR_OP_IPV6;
 	int err;

 	if (!tb[NFTA_EXTHDR_SREG] ||
 	    !tb[NFTA_EXTHDR_TYPE] ||
 	    !tb[NFTA_EXTHDR_OFFSET] ||
 	    !tb[NFTA_EXTHDR_LEN])
 		return -EINVAL;

 	if (tb[NFTA_EXTHDR_DREG] || tb[NFTA_EXTHDR_FLAGS])
 		return -EINVAL;

 	err = nft_parse_u32_check(tb[NFTA_EXTHDR_OFFSET], U8_MAX, &offset);
 	if (err < 0)
 		return err;

 	err = nft_parse_u32_check(tb[NFTA_EXTHDR_LEN], U8_MAX, &len);
 	if (err < 0)
 		return err;

 	if (offset < 2)
 		return -EOPNOTSUPP;

 	switch (len) {
 	case 2: break;
 	case 4: break;
 	default:
 		return -EOPNOTSUPP;
 	}

 	err = nft_parse_u32_check(tb[NFTA_EXTHDR_OP], U8_MAX, &op);
 	if (err < 0)
 		return err;

 	priv->type   = nla_get_u8(tb[NFTA_EXTHDR_TYPE]);
 	priv->offset = offset;
 	priv->len    = len;
 	priv->sreg   = nft_parse_register(tb[NFTA_EXTHDR_SREG]);
 	priv->flags  = flags;
 	priv->op     = op;

 	return nft_validate_register_load(priv->sreg, priv->len);
 }

 static int nft_exthdr_ipv4_init(const struct nft_ctx *ctx,
 				const struct nft_expr *expr,
 				const struct nlattr * const tb[])
 {
 	struct nft_exthdr *priv = nft_expr_priv(expr);
 	int err = nft_exthdr_init(ctx, expr, tb);

 	if (err < 0)
 		return err;

 	switch (priv->type) {
 	case IPOPT_SSRR:
 	case IPOPT_LSRR:
 	case IPOPT_RR:
 	case IPOPT_RA:
 		break;
 	default:
 		return -EOPNOTSUPP;
 	}
 	return 0;
 }

 static int nft_exthdr_dump_common(struct sk_buff *skb, const struct nft_exthdr *priv)
 {
 	if (nla_put_u8(skb, NFTA_EXTHDR_TYPE, priv->type))
 		goto nla_put_failure;
 	if (nla_put_be32(skb, NFTA_EXTHDR_OFFSET, htonl(priv->offset)))
 		goto nla_put_failure;
 	if (nla_put_be32(skb, NFTA_EXTHDR_LEN, htonl(priv->len)))
 		goto nla_put_failure;
 	if (nla_put_be32(skb, NFTA_EXTHDR_FLAGS, htonl(priv->flags)))
 		goto nla_put_failure;
 	if (nla_put_be32(skb, NFTA_EXTHDR_OP, htonl(priv->op)))
 		goto nla_put_failure;
 	return 0;

 nla_put_failure:
 	return -1;
 }

 static int nft_exthdr_dump(struct sk_buff *skb, const struct nft_expr *expr)
 {
 	const struct nft_exthdr *priv = nft_expr_priv(expr);

 	if (nft_dump_register(skb, NFTA_EXTHDR_DREG, priv->dreg))
 		return -1;

 	return nft_exthdr_dump_common(skb, priv);
 }

 static int nft_exthdr_dump_set(struct sk_buff *skb, const struct nft_expr *expr)
 {
 	const struct nft_exthdr *priv = nft_expr_priv(expr);

 	if (nft_dump_register(skb, NFTA_EXTHDR_SREG, priv->sreg))
 		return -1;

 	return nft_exthdr_dump_common(skb, priv);
 }

 static const struct nft_expr_ops nft_exthdr_ipv6_ops = {
 	.type		= &nft_exthdr_type,
 	.size		= NFT_EXPR_SIZE(sizeof(struct nft_exthdr)),
 	.eval		= nft_exthdr_ipv6_eval,
 	.init		= nft_exthdr_init,
 	.dump		= nft_exthdr_dump,
 };

 static const struct nft_expr_ops nft_exthdr_ipv4_ops = {
 	.type		= &nft_exthdr_type,
 	.size		= NFT_EXPR_SIZE(sizeof(struct nft_exthdr)),
 	.eval		= nft_exthdr_ipv4_eval,
 	.init		= nft_exthdr_ipv4_init,
 	.dump		= nft_exthdr_dump,
 };

 static const struct nft_expr_ops nft_exthdr_tcp_ops = {
 	.type		= &nft_exthdr_type,
 	.size		= NFT_EXPR_SIZE(sizeof(struct nft_exthdr)),
 	.eval		= nft_exthdr_tcp_eval,
 	.init		= nft_exthdr_init,
 	.dump		= nft_exthdr_dump,
 };

 static const struct nft_expr_ops nft_exthdr_tcp_set_ops = {
 	.type		= &nft_exthdr_type,
 	.size		= NFT_EXPR_SIZE(sizeof(struct nft_exthdr)),
 	.eval		= nft_exthdr_tcp_set_eval,
 	.init		= nft_exthdr_tcp_set_init,
 	.dump		= nft_exthdr_dump_set,
 };

 static const struct nft_expr_ops *
 nft_exthdr_select_ops(const struct nft_ctx *ctx,
 		      const struct nlattr * const tb[])
 {
 	u32 op;

 	if (!tb[NFTA_EXTHDR_OP])
 		return &nft_exthdr_ipv6_ops;

 	if (tb[NFTA_EXTHDR_SREG] && tb[NFTA_EXTHDR_DREG])
 		return ERR_PTR(-EOPNOTSUPP);

 	op = ntohl(nla_get_be32(tb[NFTA_EXTHDR_OP]));
 	switch (op) {
 	case NFT_EXTHDR_OP_TCPOPT:
 		if (tb[NFTA_EXTHDR_SREG])
 			return &nft_exthdr_tcp_set_ops;
 		if (tb[NFTA_EXTHDR_DREG])
 			return &nft_exthdr_tcp_ops;
 		break;
 	case NFT_EXTHDR_OP_IPV6:
 		if (tb[NFTA_EXTHDR_DREG])
 			return &nft_exthdr_ipv6_ops;
 		break;
 	case NFT_EXTHDR_OP_IPV4:
 		if (ctx->family != NFPROTO_IPV6) {
 			if (tb[NFTA_EXTHDR_DREG])
 				return &nft_exthdr_ipv4_ops;
 		}
 		break;
 	}

 	return ERR_PTR(-EOPNOTSUPP);
 }

 struct nft_expr_type nft_exthdr_type __read_mostly = {
 	.name		= "exthdr",
 	.select_ops	= nft_exthdr_select_ops,
 	.policy		= nft_exthdr_policy,
 	.maxattr	= NFTA_EXTHDR_MAX,
 	.owner		= THIS_MODULE,
 };
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
	*
	* Development of this code funded by Astaro AG (http://www.astaro.com/)
	*/

	#include <asm/unaligned.h>
	#include <linux/kernel.h>
	#include <linux/netlink.h>
	#include <linux/netfilter.h>
	#include <linux/netfilter/nf_tables.h>
	#include <net/netfilter/nf_tables_core.h>
	#include <net/netfilter/nf_tables.h>
	#include <net/tcp.h>

	struct nft_exthdr {
	u8 type;
	u8 offset;
	u8 len;
	u8 op;
	enum nft_registers dreg:8;
	enum nft_registers sreg:8;
	u8 flags;
	};

	static unsigned int optlen(const u8 *opt, unsigned int offset)
	{
	/* Beware zero-length options: make finite progress */
	if (opt[offset] <= TCPOPT_NOP \|\| opt[offset + 1] == 0)
	return 1;
	else
	return opt[offset + 1];
	}

	static void nft_exthdr_ipv6_eval(const struct nft_expr *expr,
	struct nft_regs *regs,
	const struct nft_pktinfo *pkt)
	{
	struct nft_exthdr *priv = nft_expr_priv(expr);
	u32 *dest = &regs->data[priv->dreg];
	unsigned int offset = 0;
	int err;

	err = ipv6_find_hdr(pkt->skb, &offset, priv->type, NULL, NULL);
	if (priv->flags & NFT_EXTHDR_F_PRESENT) {
	nft_reg_store8(dest, err >= 0);
	return;
	} else if (err < 0) {
	goto err;
	}
	offset += priv->offset;

	dest[priv->len / NFT_REG32_SIZE] = 0;
	if (skb_copy_bits(pkt->skb, offset, dest, priv->len) < 0)
	goto err;
	return;
	err:
	regs->verdict.code = NFT_BREAK;
	}

	/* find the offset to specified option.
	*
	* If target header is found, its offset is set in *offset and return option
	* number. Otherwise, return negative error.
	*
	* If the first fragment doesn't contain the End of Options it is considered
	* invalid.
	*/
	static int ipv4_find_option(struct net net, struct sk_buff skb,
	unsigned int *offset, int target)
	{
	unsigned char optbuf[sizeof(struct ip_options) + 40];
	struct ip_options opt = (struct ip_options )optbuf;
	struct iphdr *iph, _iph;
	unsigned int start;
	bool found = false;
	__be32 info;
	int optlen;

	iph = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
	if (!iph)
	return -EBADMSG;
	start = sizeof(struct iphdr);

	optlen = iph->ihl * 4 - (int)sizeof(struct iphdr);
	if (optlen <= 0)
	return -ENOENT;

	memset(opt, 0, sizeof(struct ip_options));
	/* Copy the options since __ip_options_compile() modifies
	* the options.
	*/
	if (skb_copy_bits(skb, start, opt->__data, optlen))
	return -EBADMSG;
	opt->optlen = optlen;

	if (__ip_options_compile(net, opt, NULL, &info))
	return -EBADMSG;

	switch (target) {
	case IPOPT_SSRR:
	case IPOPT_LSRR:
	if (!opt->srr)
	break;
	found = target == IPOPT_SSRR ? opt->is_strictroute :
	!opt->is_strictroute;
	if (found)
	*offset = opt->srr + start;
	break;
	case IPOPT_RR:
	if (!opt->rr)
	break;
	*offset = opt->rr + start;
	found = true;
	break;
	case IPOPT_RA:
	if (!opt->router_alert)
	break;
	*offset = opt->router_alert + start;
	found = true;
	break;
	default:
	return -EOPNOTSUPP;
	}
	return found ? target : -ENOENT;
	}

	static void nft_exthdr_ipv4_eval(const struct nft_expr *expr,
	struct nft_regs *regs,
	const struct nft_pktinfo *pkt)
	{
	struct nft_exthdr *priv = nft_expr_priv(expr);
	u32 *dest = &regs->data[priv->dreg];
	struct sk_buff *skb = pkt->skb;
	unsigned int offset;
	int err;

	if (skb->protocol != htons(ETH_P_IP))
	goto err;

	err = ipv4_find_option(nft_net(pkt), skb, &offset, priv->type);
	if (priv->flags & NFT_EXTHDR_F_PRESENT) {
	nft_reg_store8(dest, err >= 0);
	return;
	} else if (err < 0) {
	goto err;
	}
	offset += priv->offset;

	dest[priv->len / NFT_REG32_SIZE] = 0;
	if (skb_copy_bits(pkt->skb, offset, dest, priv->len) < 0)
	goto err;
	return;
	err:
	regs->verdict.code = NFT_BREAK;
	}

	static void *
	nft_tcp_header_pointer(const struct nft_pktinfo *pkt,
	unsigned int len, void buffer, unsigned int tcphdr_len)
	{
	struct tcphdr *tcph;

	if (!pkt->tprot_set \|\| pkt->tprot != IPPROTO_TCP)
	return NULL;

	tcph = skb_header_pointer(pkt->skb, pkt->xt.thoff, sizeof(*tcph), buffer);
	if (!tcph)
	return NULL;

	*tcphdr_len = __tcp_hdrlen(tcph);
	if (tcphdr_len < sizeof(tcph) \|\| *tcphdr_len > len)
	return NULL;

	return skb_header_pointer(pkt->skb, pkt->xt.thoff, *tcphdr_len, buffer);
	}

	static void nft_exthdr_tcp_eval(const struct nft_expr *expr,
	struct nft_regs *regs,
	const struct nft_pktinfo *pkt)
	{
	u8 buff[sizeof(struct tcphdr) + MAX_TCP_OPTION_SPACE];
	struct nft_exthdr *priv = nft_expr_priv(expr);
	unsigned int i, optl, tcphdr_len, offset;
	u32 *dest = &regs->data[priv->dreg];
	struct tcphdr *tcph;
	u8 *opt;

	tcph = nft_tcp_header_pointer(pkt, sizeof(buff), buff, &tcphdr_len);
	if (!tcph)
	goto err;

	opt = (u8 *)tcph;
	for (i = sizeof(*tcph); i < tcphdr_len - 1; i += optl) {
	optl = optlen(opt, i);

	if (priv->type != opt[i])
	continue;

	if (i + optl > tcphdr_len \|\| priv->len + priv->offset > optl)
	goto err;

	offset = i + priv->offset;
	if (priv->flags & NFT_EXTHDR_F_PRESENT) {
	*dest = 1;
	} else {
	dest[priv->len / NFT_REG32_SIZE] = 0;
	memcpy(dest, opt + offset, priv->len);
	}

	return;
	}

	err:
	if (priv->flags & NFT_EXTHDR_F_PRESENT)
	*dest = 0;
	else
	regs->verdict.code = NFT_BREAK;
	}

	static void nft_exthdr_tcp_set_eval(const struct nft_expr *expr,
	struct nft_regs *regs,
	const struct nft_pktinfo *pkt)
	{
	u8 buff[sizeof(struct tcphdr) + MAX_TCP_OPTION_SPACE];
	struct nft_exthdr *priv = nft_expr_priv(expr);
	unsigned int i, optl, tcphdr_len, offset;
	struct tcphdr *tcph;
	u8 *opt;

	tcph = nft_tcp_header_pointer(pkt, sizeof(buff), buff, &tcphdr_len);
	if (!tcph)
	return;

	opt = (u8 *)tcph;
	for (i = sizeof(*tcph); i < tcphdr_len - 1; i += optl) {
	union {
	__be16 v16;
	__be32 v32;
	} old, new;

	optl = optlen(opt, i);

	if (priv->type != opt[i])
	continue;

	if (i + optl > tcphdr_len \|\| priv->len + priv->offset > optl)
	return;

	if (skb_ensure_writable(pkt->skb,
	pkt->xt.thoff + i + priv->len))
	return;

	tcph = nft_tcp_header_pointer(pkt, sizeof(buff), buff,
	&tcphdr_len);
	if (!tcph)
	return;

	offset = i + priv->offset;

	switch (priv->len) {
	case 2:
	old.v16 = get_unaligned((u16 *)(opt + offset));
	new.v16 = (__force __be16)nft_reg_load16(
	&regs->data[priv->sreg]);

	switch (priv->type) {
	case TCPOPT_MSS:
	/* increase can cause connection to stall */
	if (ntohs(old.v16) <= ntohs(new.v16))
	return;
	break;
	}

	if (old.v16 == new.v16)
	return;

	put_unaligned(new.v16, (u16*)(opt + offset));
	inet_proto_csum_replace2(&tcph->check, pkt->skb,
	old.v16, new.v16, false);
	break;
	case 4:
	new.v32 = regs->data[priv->sreg];
	old.v32 = get_unaligned((u32 *)(opt + offset));

	if (old.v32 == new.v32)
	return;

	put_unaligned(new.v32, (u32*)(opt + offset));
	inet_proto_csum_replace4(&tcph->check, pkt->skb,
	old.v32, new.v32, false);
	break;
	default:
	WARN_ON_ONCE(1);
	break;
	}

	return;
	}
	}

	static const struct nla_policy nft_exthdr_policy[NFTA_EXTHDR_MAX + 1] = {
	[NFTA_EXTHDR_DREG] = { .type = NLA_U32 },
	[NFTA_EXTHDR_TYPE] = { .type = NLA_U8 },
	[NFTA_EXTHDR_OFFSET] = { .type = NLA_U32 },
	[NFTA_EXTHDR_LEN] = { .type = NLA_U32 },
	[NFTA_EXTHDR_FLAGS] = { .type = NLA_U32 },
	[NFTA_EXTHDR_OP] = { .type = NLA_U32 },
	[NFTA_EXTHDR_SREG] = { .type = NLA_U32 },
	};

	static int nft_exthdr_init(const struct nft_ctx *ctx,
	const struct nft_expr *expr,
	const struct nlattr * const tb[])
	{
	struct nft_exthdr *priv = nft_expr_priv(expr);
	u32 offset, len, flags = 0, op = NFT_EXTHDR_OP_IPV6;
	int err;

	if (!tb[NFTA_EXTHDR_DREG] \|\|
	!tb[NFTA_EXTHDR_TYPE] \|\|
	!tb[NFTA_EXTHDR_OFFSET] \|\|
	!tb[NFTA_EXTHDR_LEN])
	return -EINVAL;

	err = nft_parse_u32_check(tb[NFTA_EXTHDR_OFFSET], U8_MAX, &offset);
	if (err < 0)
	return err;

	err = nft_parse_u32_check(tb[NFTA_EXTHDR_LEN], U8_MAX, &len);
	if (err < 0)
	return err;

	if (tb[NFTA_EXTHDR_FLAGS]) {
	err = nft_parse_u32_check(tb[NFTA_EXTHDR_FLAGS], U8_MAX, &flags);
	if (err < 0)
	return err;

	if (flags & ~NFT_EXTHDR_F_PRESENT)
	return -EINVAL;
	}

	if (tb[NFTA_EXTHDR_OP]) {
	err = nft_parse_u32_check(tb[NFTA_EXTHDR_OP], U8_MAX, &op);
	if (err < 0)
	return err;
	}

	priv->type = nla_get_u8(tb[NFTA_EXTHDR_TYPE]);
	priv->offset = offset;
	priv->len = len;
	priv->dreg = nft_parse_register(tb[NFTA_EXTHDR_DREG]);
	priv->flags = flags;
	priv->op = op;

	return nft_validate_register_store(ctx, priv->dreg, NULL,
	NFT_DATA_VALUE, priv->len);
	}

	static int nft_exthdr_tcp_set_init(const struct nft_ctx *ctx,
	const struct nft_expr *expr,
	const struct nlattr * const tb[])
	{
	struct nft_exthdr *priv = nft_expr_priv(expr);
	u32 offset, len, flags = 0, op = NFT_EXTHDR_OP_IPV6;
	int err;

	if (!tb[NFTA_EXTHDR_SREG] \|\|
	!tb[NFTA_EXTHDR_TYPE] \|\|
	!tb[NFTA_EXTHDR_OFFSET] \|\|
	!tb[NFTA_EXTHDR_LEN])
	return -EINVAL;

	if (tb[NFTA_EXTHDR_DREG] \|\| tb[NFTA_EXTHDR_FLAGS])
	return -EINVAL;

	err = nft_parse_u32_check(tb[NFTA_EXTHDR_OFFSET], U8_MAX, &offset);
	if (err < 0)
	return err;

	err = nft_parse_u32_check(tb[NFTA_EXTHDR_LEN], U8_MAX, &len);
	if (err < 0)
	return err;

	if (offset < 2)
	return -EOPNOTSUPP;

	switch (len) {
	case 2: break;
	case 4: break;
	default:
	return -EOPNOTSUPP;
	}

	err = nft_parse_u32_check(tb[NFTA_EXTHDR_OP], U8_MAX, &op);
	if (err < 0)
	return err;

	priv->type = nla_get_u8(tb[NFTA_EXTHDR_TYPE]);
	priv->offset = offset;
	priv->len = len;
	priv->sreg = nft_parse_register(tb[NFTA_EXTHDR_SREG]);
	priv->flags = flags;
	priv->op = op;

	return nft_validate_register_load(priv->sreg, priv->len);
	}

	static int nft_exthdr_ipv4_init(const struct nft_ctx *ctx,
	const struct nft_expr *expr,
	const struct nlattr * const tb[])
	{
	struct nft_exthdr *priv = nft_expr_priv(expr);
	int err = nft_exthdr_init(ctx, expr, tb);

	if (err < 0)
	return err;

	switch (priv->type) {
	case IPOPT_SSRR:
	case IPOPT_LSRR:
	case IPOPT_RR:
	case IPOPT_RA:
	break;
	default:
	return -EOPNOTSUPP;
	}
	return 0;
	}

	static int nft_exthdr_dump_common(struct sk_buff skb, const struct nft_exthdr priv)
	{
	if (nla_put_u8(skb, NFTA_EXTHDR_TYPE, priv->type))
	goto nla_put_failure;
	if (nla_put_be32(skb, NFTA_EXTHDR_OFFSET, htonl(priv->offset)))
	goto nla_put_failure;
	if (nla_put_be32(skb, NFTA_EXTHDR_LEN, htonl(priv->len)))
	goto nla_put_failure;
	if (nla_put_be32(skb, NFTA_EXTHDR_FLAGS, htonl(priv->flags)))
	goto nla_put_failure;
	if (nla_put_be32(skb, NFTA_EXTHDR_OP, htonl(priv->op)))
	goto nla_put_failure;
	return 0;

	nla_put_failure:
	return -1;
	}

	static int nft_exthdr_dump(struct sk_buff skb, const struct nft_expr expr)
	{
	const struct nft_exthdr *priv = nft_expr_priv(expr);

	if (nft_dump_register(skb, NFTA_EXTHDR_DREG, priv->dreg))
	return -1;

	return nft_exthdr_dump_common(skb, priv);
	}

	static int nft_exthdr_dump_set(struct sk_buff skb, const struct nft_expr expr)
	{
	const struct nft_exthdr *priv = nft_expr_priv(expr);

	if (nft_dump_register(skb, NFTA_EXTHDR_SREG, priv->sreg))
	return -1;

	return nft_exthdr_dump_common(skb, priv);
	}

	static const struct nft_expr_ops nft_exthdr_ipv6_ops = {
	.type = &nft_exthdr_type,
	.size = NFT_EXPR_SIZE(sizeof(struct nft_exthdr)),
	.eval = nft_exthdr_ipv6_eval,
	.init = nft_exthdr_init,
	.dump = nft_exthdr_dump,
	};

	static const struct nft_expr_ops nft_exthdr_ipv4_ops = {
	.type = &nft_exthdr_type,
	.size = NFT_EXPR_SIZE(sizeof(struct nft_exthdr)),
	.eval = nft_exthdr_ipv4_eval,
	.init = nft_exthdr_ipv4_init,
	.dump = nft_exthdr_dump,
	};

	static const struct nft_expr_ops nft_exthdr_tcp_ops = {
	.type = &nft_exthdr_type,
	.size = NFT_EXPR_SIZE(sizeof(struct nft_exthdr)),
	.eval = nft_exthdr_tcp_eval,
	.init = nft_exthdr_init,
	.dump = nft_exthdr_dump,
	};

	static const struct nft_expr_ops nft_exthdr_tcp_set_ops = {
	.type = &nft_exthdr_type,
	.size = NFT_EXPR_SIZE(sizeof(struct nft_exthdr)),
	.eval = nft_exthdr_tcp_set_eval,
	.init = nft_exthdr_tcp_set_init,
	.dump = nft_exthdr_dump_set,
	};

	static const struct nft_expr_ops *
	nft_exthdr_select_ops(const struct nft_ctx *ctx,
	const struct nlattr * const tb[])
	{
	u32 op;

	if (!tb[NFTA_EXTHDR_OP])
	return &nft_exthdr_ipv6_ops;

	if (tb[NFTA_EXTHDR_SREG] && tb[NFTA_EXTHDR_DREG])
	return ERR_PTR(-EOPNOTSUPP);

	op = ntohl(nla_get_be32(tb[NFTA_EXTHDR_OP]));
	switch (op) {
	case NFT_EXTHDR_OP_TCPOPT:
	if (tb[NFTA_EXTHDR_SREG])
	return &nft_exthdr_tcp_set_ops;
	if (tb[NFTA_EXTHDR_DREG])
	return &nft_exthdr_tcp_ops;
	break;
	case NFT_EXTHDR_OP_IPV6:
	if (tb[NFTA_EXTHDR_DREG])
	return &nft_exthdr_ipv6_ops;
	break;
	case NFT_EXTHDR_OP_IPV4:
	if (ctx->family != NFPROTO_IPV6) {
	if (tb[NFTA_EXTHDR_DREG])
	return &nft_exthdr_ipv4_ops;
	}
	break;
	}

	return ERR_PTR(-EOPNOTSUPP);
	}

	struct nft_expr_type nft_exthdr_type __read_mostly = {
	.name = "exthdr",
	.select_ops = nft_exthdr_select_ops,
	.policy = nft_exthdr_policy,
	.maxattr = NFTA_EXTHDR_MAX,
	.owner = THIS_MODULE,
	};