net/ipv6/netfilter/nf_reject_ipv6.c - linux/kernel/git/dhowells/linux-fs - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /* (C) 1999-2001 Paul `Rusty' Russell
  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
  */

 #include <linux/module.h>
 #include <net/ipv6.h>
 #include <net/ip6_route.h>
 #include <net/ip6_fib.h>
 #include <net/ip6_checksum.h>
 #include <net/netfilter/ipv6/nf_reject.h>
 #include <linux/netfilter_ipv6.h>
 #include <linux/netfilter_bridge.h>

 static bool nf_reject_v6_csum_ok(struct sk_buff *skb, int hook)
 {
 	const struct ipv6hdr *ip6h = ipv6_hdr(skb);
 	int thoff;
 	__be16 fo;
 	u8 proto = ip6h->nexthdr;

 	if (skb_csum_unnecessary(skb))
 		return true;

 	if (ip6h->payload_len &&
 	    pskb_trim_rcsum(skb, ntohs(ip6h->payload_len) + sizeof(*ip6h)))
 		return false;

 	ip6h = ipv6_hdr(skb);
 	thoff = ipv6_skip_exthdr(skb, ((u8*)(ip6h+1) - skb->data), &proto, &fo);
 	if (thoff < 0 || thoff >= skb->len || (fo & htons(~0x7)) != 0)
 		return false;

 	if (!nf_reject_verify_csum(skb, thoff, proto))
 		return true;

 	return nf_ip6_checksum(skb, hook, thoff, proto) == 0;
 }

 static int nf_reject_ip6hdr_validate(struct sk_buff *skb)
 {
 	struct ipv6hdr *hdr;
 	u32 pkt_len;

 	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
 		return 0;

 	hdr = ipv6_hdr(skb);
 	if (hdr->version != 6)
 		return 0;

 	pkt_len = ntohs(hdr->payload_len);
 	if (pkt_len + sizeof(struct ipv6hdr) > skb->len)
 		return 0;

 	return 1;
 }

 struct sk_buff *nf_reject_skb_v6_tcp_reset(struct net *net,
 					   struct sk_buff *oldskb,
 					   const struct net_device *dev,
 					   int hook)
 {
 	struct sk_buff *nskb;
 	const struct tcphdr *oth;
 	struct tcphdr _oth;
 	unsigned int otcplen;
 	struct ipv6hdr *nip6h;

 	if (!nf_reject_ip6hdr_validate(oldskb))
 		return NULL;

 	oth = nf_reject_ip6_tcphdr_get(oldskb, &_oth, &otcplen, hook);
 	if (!oth)
 		return NULL;

 	nskb = alloc_skb(sizeof(struct ipv6hdr) + sizeof(struct tcphdr) +
 			 LL_MAX_HEADER, GFP_ATOMIC);
 	if (!nskb)
 		return NULL;

 	nskb->dev = (struct net_device *)dev;

 	skb_reserve(nskb, LL_MAX_HEADER);
 	nip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_TCP,
 				     net->ipv6.devconf_all->hop_limit);
 	nf_reject_ip6_tcphdr_put(nskb, oldskb, oth, otcplen);
 	nip6h->payload_len = htons(nskb->len - sizeof(struct ipv6hdr));

 	return nskb;
 }
 EXPORT_SYMBOL_GPL(nf_reject_skb_v6_tcp_reset);

 struct sk_buff *nf_reject_skb_v6_unreach(struct net *net,
 					 struct sk_buff *oldskb,
 					 const struct net_device *dev,
 					 int hook, u8 code)
 {
 	struct sk_buff *nskb;
 	struct ipv6hdr *nip6h;
 	struct icmp6hdr *icmp6h;
 	unsigned int len;

 	if (!nf_reject_ip6hdr_validate(oldskb))
 		return NULL;

 	/* Include "As much of invoking packet as possible without the ICMPv6
 	 * packet exceeding the minimum IPv6 MTU" in the ICMP payload.
 	 */
 	len = min_t(unsigned int, 1220, oldskb->len);

 	if (!pskb_may_pull(oldskb, len))
 		return NULL;

 	if (!nf_reject_v6_csum_ok(oldskb, hook))
 		return NULL;

 	nskb = alloc_skb(sizeof(struct ipv6hdr) + sizeof(struct icmp6hdr) +
 			 LL_MAX_HEADER + len, GFP_ATOMIC);
 	if (!nskb)
 		return NULL;

 	nskb->dev = (struct net_device *)dev;

 	skb_reserve(nskb, LL_MAX_HEADER);
 	nip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_ICMPV6,
 				     net->ipv6.devconf_all->hop_limit);

 	skb_reset_transport_header(nskb);
 	icmp6h = skb_put_zero(nskb, sizeof(struct icmp6hdr));
 	icmp6h->icmp6_type = ICMPV6_DEST_UNREACH;
 	icmp6h->icmp6_code = code;

 	skb_put_data(nskb, skb_network_header(oldskb), len);
 	nip6h->payload_len = htons(nskb->len - sizeof(struct ipv6hdr));

 	icmp6h->icmp6_cksum =
 		csum_ipv6_magic(&nip6h->saddr, &nip6h->daddr,
 				nskb->len - sizeof(struct ipv6hdr),
 				IPPROTO_ICMPV6,
 				csum_partial(icmp6h,
 					     nskb->len - sizeof(struct ipv6hdr),
 					     0));

 	return nskb;
 }
 EXPORT_SYMBOL_GPL(nf_reject_skb_v6_unreach);

 const struct tcphdr *nf_reject_ip6_tcphdr_get(struct sk_buff *oldskb,
 					      struct tcphdr *otcph,
 					      unsigned int *otcplen, int hook)
 {
 	const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
 	u8 proto;
 	__be16 frag_off;
 	int tcphoff;

 	proto = oip6h->nexthdr;
 	tcphoff = ipv6_skip_exthdr(oldskb, ((u8 *)(oip6h + 1) - oldskb->data),
 				   &proto, &frag_off);

 	if ((tcphoff < 0) || (tcphoff > oldskb->len)) {
 		pr_debug("Cannot get TCP header.\n");
 		return NULL;
 	}

 	*otcplen = oldskb->len - tcphoff;

 	/* IP header checks: fragment, too short. */
 	if (proto != IPPROTO_TCP || *otcplen < sizeof(struct tcphdr)) {
 		pr_debug("proto(%d) != IPPROTO_TCP or too short (len = %d)\n",
 			 proto, *otcplen);
 		return NULL;
 	}

 	otcph = skb_header_pointer(oldskb, tcphoff, sizeof(struct tcphdr),
 				   otcph);
 	if (otcph == NULL)
 		return NULL;

 	/* No RST for RST. */
 	if (otcph->rst) {
 		pr_debug("RST is set\n");
 		return NULL;
 	}

 	/* Check checksum. */
 	if (nf_ip6_checksum(oldskb, hook, tcphoff, IPPROTO_TCP)) {
 		pr_debug("TCP checksum is invalid\n");
 		return NULL;
 	}

 	return otcph;
 }
 EXPORT_SYMBOL_GPL(nf_reject_ip6_tcphdr_get);

 struct ipv6hdr *nf_reject_ip6hdr_put(struct sk_buff *nskb,
 				     const struct sk_buff *oldskb,
 				     __u8 protocol, int hoplimit)
 {
 	struct ipv6hdr *ip6h;
 	const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
 #define DEFAULT_TOS_VALUE	0x0U
 	const __u8 tclass = DEFAULT_TOS_VALUE;

 	skb_put(nskb, sizeof(struct ipv6hdr));
 	skb_reset_network_header(nskb);
 	ip6h = ipv6_hdr(nskb);
 	ip6_flow_hdr(ip6h, tclass, 0);
 	ip6h->hop_limit = hoplimit;
 	ip6h->nexthdr = protocol;
 	ip6h->saddr = oip6h->daddr;
 	ip6h->daddr = oip6h->saddr;

 	nskb->protocol = htons(ETH_P_IPV6);

 	return ip6h;
 }
 EXPORT_SYMBOL_GPL(nf_reject_ip6hdr_put);

 void nf_reject_ip6_tcphdr_put(struct sk_buff *nskb,
 			      const struct sk_buff *oldskb,
 			      const struct tcphdr *oth, unsigned int otcplen)
 {
 	struct tcphdr *tcph;
 	int needs_ack;

 	skb_reset_transport_header(nskb);
 	tcph = skb_put(nskb, sizeof(struct tcphdr));
 	/* Truncate to length (no data) */
 	tcph->doff = sizeof(struct tcphdr)/4;
 	tcph->source = oth->dest;
 	tcph->dest = oth->source;

 	if (oth->ack) {
 		needs_ack = 0;
 		tcph->seq = oth->ack_seq;
 		tcph->ack_seq = 0;
 	} else {
 		needs_ack = 1;
 		tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
 				      otcplen - (oth->doff<<2));
 		tcph->seq = 0;
 	}

 	/* Reset flags */
 	((u_int8_t *)tcph)[13] = 0;
 	tcph->rst = 1;
 	tcph->ack = needs_ack;
 	tcph->window = 0;
 	tcph->urg_ptr = 0;
 	tcph->check = 0;

 	/* Adjust TCP checksum */
 	tcph->check = csum_ipv6_magic(&ipv6_hdr(nskb)->saddr,
 				      &ipv6_hdr(nskb)->daddr,
 				      sizeof(struct tcphdr), IPPROTO_TCP,
 				      csum_partial(tcph,
 						   sizeof(struct tcphdr), 0));
 }
 EXPORT_SYMBOL_GPL(nf_reject_ip6_tcphdr_put);

 static int nf_reject6_fill_skb_dst(struct sk_buff *skb_in)
 {
 	struct dst_entry *dst = NULL;
 	struct flowi fl;

 	memset(&fl, 0, sizeof(struct flowi));
 	fl.u.ip6.daddr = ipv6_hdr(skb_in)->saddr;
 	nf_ip6_route(dev_net(skb_in->dev), &dst, &fl, false);
 	if (!dst)
 		return -1;

 	skb_dst_set(skb_in, dst);
 	return 0;
 }

 void nf_send_reset6(struct net *net, struct sock *sk, struct sk_buff *oldskb,
 		    int hook)
 {
 	struct sk_buff *nskb;
 	struct tcphdr _otcph;
 	const struct tcphdr *otcph;
 	unsigned int otcplen, hh_len;
 	const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
 	struct ipv6hdr *ip6h;
 	struct dst_entry *dst = NULL;
 	struct flowi6 fl6;

 	if ((!(ipv6_addr_type(&oip6h->saddr) & IPV6_ADDR_UNICAST)) ||
 	    (!(ipv6_addr_type(&oip6h->daddr) & IPV6_ADDR_UNICAST))) {
 		pr_debug("addr is not unicast.\n");
 		return;
 	}

 	otcph = nf_reject_ip6_tcphdr_get(oldskb, &_otcph, &otcplen, hook);
 	if (!otcph)
 		return;

 	memset(&fl6, 0, sizeof(fl6));
 	fl6.flowi6_proto = IPPROTO_TCP;
 	fl6.saddr = oip6h->daddr;
 	fl6.daddr = oip6h->saddr;
 	fl6.fl6_sport = otcph->dest;
 	fl6.fl6_dport = otcph->source;

 	if (hook == NF_INET_PRE_ROUTING || hook == NF_INET_INGRESS) {
 		nf_ip6_route(net, &dst, flowi6_to_flowi(&fl6), false);
 		if (!dst)
 			return;
 		skb_dst_set(oldskb, dst);
 	}

 	fl6.flowi6_oif = l3mdev_master_ifindex(skb_dst(oldskb)->dev);
 	fl6.flowi6_mark = IP6_REPLY_MARK(net, oldskb->mark);
 	security_skb_classify_flow(oldskb, flowi6_to_flowi_common(&fl6));
 	dst = ip6_route_output(net, NULL, &fl6);
 	if (dst->error) {
 		dst_release(dst);
 		return;
 	}
 	dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0);
 	if (IS_ERR(dst))
 		return;

 	hh_len = (dst->dev->hard_header_len + 15)&~15;
 	nskb = alloc_skb(hh_len + 15 + dst->header_len + sizeof(struct ipv6hdr)
 			 + sizeof(struct tcphdr) + dst->trailer_len,
 			 GFP_ATOMIC);

 	if (!nskb) {
 		net_dbg_ratelimited("cannot alloc skb\n");
 		dst_release(dst);
 		return;
 	}

 	skb_dst_set(nskb, dst);

 	nskb->mark = fl6.flowi6_mark;

 	skb_reserve(nskb, hh_len + dst->header_len);
 	ip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_TCP,
 				    ip6_dst_hoplimit(dst));
 	nf_reject_ip6_tcphdr_put(nskb, oldskb, otcph, otcplen);

 	nf_ct_attach(nskb, oldskb);
 	nf_ct_set_closing(skb_nfct(oldskb));

 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 	/* If we use ip6_local_out for bridged traffic, the MAC source on
 	 * the RST will be ours, instead of the destination's.  This confuses
 	 * some routers/firewalls, and they drop the packet.  So we need to
 	 * build the eth header using the original destination's MAC as the
 	 * source, and send the RST packet directly.
 	 */
 	if (nf_bridge_info_exists(oldskb)) {
 		struct ethhdr *oeth = eth_hdr(oldskb);
 		struct net_device *br_indev;

 		br_indev = nf_bridge_get_physindev(oldskb, net);
 		if (!br_indev) {
 			kfree_skb(nskb);
 			return;
 		}

 		nskb->dev = br_indev;
 		nskb->protocol = htons(ETH_P_IPV6);
 		ip6h->payload_len = htons(sizeof(struct tcphdr));
 		if (dev_hard_header(nskb, nskb->dev, ntohs(nskb->protocol),
 				    oeth->h_source, oeth->h_dest, nskb->len) < 0) {
 			kfree_skb(nskb);
 			return;
 		}
 		dev_queue_xmit(nskb);
 	} else
 #endif
 		ip6_local_out(net, sk, nskb);
 }
 EXPORT_SYMBOL_GPL(nf_send_reset6);

 static bool reject6_csum_ok(struct sk_buff *skb, int hook)
 {
 	const struct ipv6hdr *ip6h = ipv6_hdr(skb);
 	int thoff;
 	__be16 fo;
 	u8 proto;

 	if (skb_csum_unnecessary(skb))
 		return true;

 	proto = ip6h->nexthdr;
 	thoff = ipv6_skip_exthdr(skb, ((u8 *)(ip6h + 1) - skb->data), &proto, &fo);

 	if (thoff < 0 || thoff >= skb->len || (fo & htons(~0x7)) != 0)
 		return false;

 	if (!nf_reject_verify_csum(skb, thoff, proto))
 		return true;

 	return nf_ip6_checksum(skb, hook, thoff, proto) == 0;
 }

 void nf_send_unreach6(struct net *net, struct sk_buff *skb_in,
 		      unsigned char code, unsigned int hooknum)
 {
 	if (!reject6_csum_ok(skb_in, hooknum))
 		return;

 	if (hooknum == NF_INET_LOCAL_OUT && skb_in->dev == NULL)
 		skb_in->dev = net->loopback_dev;

 	if ((hooknum == NF_INET_PRE_ROUTING || hooknum == NF_INET_INGRESS) &&
 	    nf_reject6_fill_skb_dst(skb_in) < 0)
 		return;

 	icmpv6_send(skb_in, ICMPV6_DEST_UNREACH, code, 0);
 }
 EXPORT_SYMBOL_GPL(nf_send_unreach6);

 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("IPv6 packet rejection core");
	// SPDX-License-Identifier: GPL-2.0-only
	/* (C) 1999-2001 Paul `Rusty' Russell
	* (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
	*/

	#include <linux/module.h>
	#include <net/ipv6.h>
	#include <net/ip6_route.h>
	#include <net/ip6_fib.h>
	#include <net/ip6_checksum.h>
	#include <net/netfilter/ipv6/nf_reject.h>
	#include <linux/netfilter_ipv6.h>
	#include <linux/netfilter_bridge.h>

	static bool nf_reject_v6_csum_ok(struct sk_buff *skb, int hook)
	{
	const struct ipv6hdr *ip6h = ipv6_hdr(skb);
	int thoff;
	__be16 fo;
	u8 proto = ip6h->nexthdr;

	if (skb_csum_unnecessary(skb))
	return true;

	if (ip6h->payload_len &&
	pskb_trim_rcsum(skb, ntohs(ip6h->payload_len) + sizeof(*ip6h)))
	return false;

	ip6h = ipv6_hdr(skb);
	thoff = ipv6_skip_exthdr(skb, ((u8*)(ip6h+1) - skb->data), &proto, &fo);
	if (thoff < 0 \|\| thoff >= skb->len \|\| (fo & htons(~0x7)) != 0)
	return false;

	if (!nf_reject_verify_csum(skb, thoff, proto))
	return true;

	return nf_ip6_checksum(skb, hook, thoff, proto) == 0;
	}

	static int nf_reject_ip6hdr_validate(struct sk_buff *skb)
	{
	struct ipv6hdr *hdr;
	u32 pkt_len;

	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
	return 0;

	hdr = ipv6_hdr(skb);
	if (hdr->version != 6)
	return 0;

	pkt_len = ntohs(hdr->payload_len);
	if (pkt_len + sizeof(struct ipv6hdr) > skb->len)
	return 0;

	return 1;
	}

	struct sk_buff nf_reject_skb_v6_tcp_reset(struct net net,
	struct sk_buff *oldskb,
	const struct net_device *dev,
	int hook)
	{
	struct sk_buff *nskb;
	const struct tcphdr *oth;
	struct tcphdr _oth;
	unsigned int otcplen;
	struct ipv6hdr *nip6h;

	if (!nf_reject_ip6hdr_validate(oldskb))
	return NULL;

	oth = nf_reject_ip6_tcphdr_get(oldskb, &_oth, &otcplen, hook);
	if (!oth)
	return NULL;

	nskb = alloc_skb(sizeof(struct ipv6hdr) + sizeof(struct tcphdr) +
	LL_MAX_HEADER, GFP_ATOMIC);
	if (!nskb)
	return NULL;

	nskb->dev = (struct net_device *)dev;

	skb_reserve(nskb, LL_MAX_HEADER);
	nip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_TCP,
	net->ipv6.devconf_all->hop_limit);
	nf_reject_ip6_tcphdr_put(nskb, oldskb, oth, otcplen);
	nip6h->payload_len = htons(nskb->len - sizeof(struct ipv6hdr));

	return nskb;
	}
	EXPORT_SYMBOL_GPL(nf_reject_skb_v6_tcp_reset);

	struct sk_buff nf_reject_skb_v6_unreach(struct net net,
	struct sk_buff *oldskb,
	const struct net_device *dev,
	int hook, u8 code)
	{
	struct sk_buff *nskb;
	struct ipv6hdr *nip6h;
	struct icmp6hdr *icmp6h;
	unsigned int len;

	if (!nf_reject_ip6hdr_validate(oldskb))
	return NULL;

	/* Include "As much of invoking packet as possible without the ICMPv6
	* packet exceeding the minimum IPv6 MTU" in the ICMP payload.
	*/
	len = min_t(unsigned int, 1220, oldskb->len);

	if (!pskb_may_pull(oldskb, len))
	return NULL;

	if (!nf_reject_v6_csum_ok(oldskb, hook))
	return NULL;

	nskb = alloc_skb(sizeof(struct ipv6hdr) + sizeof(struct icmp6hdr) +
	LL_MAX_HEADER + len, GFP_ATOMIC);
	if (!nskb)
	return NULL;

	nskb->dev = (struct net_device *)dev;

	skb_reserve(nskb, LL_MAX_HEADER);
	nip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_ICMPV6,
	net->ipv6.devconf_all->hop_limit);

	skb_reset_transport_header(nskb);
	icmp6h = skb_put_zero(nskb, sizeof(struct icmp6hdr));
	icmp6h->icmp6_type = ICMPV6_DEST_UNREACH;
	icmp6h->icmp6_code = code;

	skb_put_data(nskb, skb_network_header(oldskb), len);
	nip6h->payload_len = htons(nskb->len - sizeof(struct ipv6hdr));

	icmp6h->icmp6_cksum =
	csum_ipv6_magic(&nip6h->saddr, &nip6h->daddr,
	nskb->len - sizeof(struct ipv6hdr),
	IPPROTO_ICMPV6,
	csum_partial(icmp6h,
	nskb->len - sizeof(struct ipv6hdr),
	0));

	return nskb;
	}
	EXPORT_SYMBOL_GPL(nf_reject_skb_v6_unreach);

	const struct tcphdr nf_reject_ip6_tcphdr_get(struct sk_buff oldskb,
	struct tcphdr *otcph,
	unsigned int *otcplen, int hook)
	{
	const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
	u8 proto;
	__be16 frag_off;
	int tcphoff;

	proto = oip6h->nexthdr;
	tcphoff = ipv6_skip_exthdr(oldskb, ((u8 *)(oip6h + 1) - oldskb->data),
	&proto, &frag_off);

	if ((tcphoff < 0) \|\| (tcphoff > oldskb->len)) {
	pr_debug("Cannot get TCP header.\n");
	return NULL;
	}

	*otcplen = oldskb->len - tcphoff;

	/* IP header checks: fragment, too short. */
	if (proto != IPPROTO_TCP \|\| *otcplen < sizeof(struct tcphdr)) {
	pr_debug("proto(%d) != IPPROTO_TCP or too short (len = %d)\n",
	proto, *otcplen);
	return NULL;
	}

	otcph = skb_header_pointer(oldskb, tcphoff, sizeof(struct tcphdr),
	otcph);
	if (otcph == NULL)
	return NULL;

	/* No RST for RST. */
	if (otcph->rst) {
	pr_debug("RST is set\n");
	return NULL;
	}

	/* Check checksum. */
	if (nf_ip6_checksum(oldskb, hook, tcphoff, IPPROTO_TCP)) {
	pr_debug("TCP checksum is invalid\n");
	return NULL;
	}

	return otcph;
	}
	EXPORT_SYMBOL_GPL(nf_reject_ip6_tcphdr_get);

	struct ipv6hdr nf_reject_ip6hdr_put(struct sk_buff nskb,
	const struct sk_buff *oldskb,
	__u8 protocol, int hoplimit)
	{
	struct ipv6hdr *ip6h;
	const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
	#define DEFAULT_TOS_VALUE 0x0U
	const __u8 tclass = DEFAULT_TOS_VALUE;

	skb_put(nskb, sizeof(struct ipv6hdr));
	skb_reset_network_header(nskb);
	ip6h = ipv6_hdr(nskb);
	ip6_flow_hdr(ip6h, tclass, 0);
	ip6h->hop_limit = hoplimit;
	ip6h->nexthdr = protocol;
	ip6h->saddr = oip6h->daddr;
	ip6h->daddr = oip6h->saddr;

	nskb->protocol = htons(ETH_P_IPV6);

	return ip6h;
	}
	EXPORT_SYMBOL_GPL(nf_reject_ip6hdr_put);

	void nf_reject_ip6_tcphdr_put(struct sk_buff *nskb,
	const struct sk_buff *oldskb,
	const struct tcphdr *oth, unsigned int otcplen)
	{
	struct tcphdr *tcph;
	int needs_ack;

	skb_reset_transport_header(nskb);
	tcph = skb_put(nskb, sizeof(struct tcphdr));
	/* Truncate to length (no data) */
	tcph->doff = sizeof(struct tcphdr)/4;
	tcph->source = oth->dest;
	tcph->dest = oth->source;

	if (oth->ack) {
	needs_ack = 0;
	tcph->seq = oth->ack_seq;
	tcph->ack_seq = 0;
	} else {
	needs_ack = 1;
	tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
	otcplen - (oth->doff<<2));
	tcph->seq = 0;
	}

	/* Reset flags */
	((u_int8_t *)tcph)[13] = 0;
	tcph->rst = 1;
	tcph->ack = needs_ack;
	tcph->window = 0;
	tcph->urg_ptr = 0;
	tcph->check = 0;

	/* Adjust TCP checksum */
	tcph->check = csum_ipv6_magic(&ipv6_hdr(nskb)->saddr,
	&ipv6_hdr(nskb)->daddr,
	sizeof(struct tcphdr), IPPROTO_TCP,
	csum_partial(tcph,
	sizeof(struct tcphdr), 0));
	}
	EXPORT_SYMBOL_GPL(nf_reject_ip6_tcphdr_put);

	static int nf_reject6_fill_skb_dst(struct sk_buff *skb_in)
	{
	struct dst_entry *dst = NULL;
	struct flowi fl;

	memset(&fl, 0, sizeof(struct flowi));
	fl.u.ip6.daddr = ipv6_hdr(skb_in)->saddr;
	nf_ip6_route(dev_net(skb_in->dev), &dst, &fl, false);
	if (!dst)
	return -1;

	skb_dst_set(skb_in, dst);
	return 0;
	}

	void nf_send_reset6(struct net net, struct sock sk, struct sk_buff *oldskb,
	int hook)
	{
	struct sk_buff *nskb;
	struct tcphdr _otcph;
	const struct tcphdr *otcph;
	unsigned int otcplen, hh_len;
	const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
	struct ipv6hdr *ip6h;
	struct dst_entry *dst = NULL;
	struct flowi6 fl6;

	if ((!(ipv6_addr_type(&oip6h->saddr) & IPV6_ADDR_UNICAST)) \|\|
	(!(ipv6_addr_type(&oip6h->daddr) & IPV6_ADDR_UNICAST))) {
	pr_debug("addr is not unicast.\n");
	return;
	}

	otcph = nf_reject_ip6_tcphdr_get(oldskb, &_otcph, &otcplen, hook);
	if (!otcph)
	return;

	memset(&fl6, 0, sizeof(fl6));
	fl6.flowi6_proto = IPPROTO_TCP;
	fl6.saddr = oip6h->daddr;
	fl6.daddr = oip6h->saddr;
	fl6.fl6_sport = otcph->dest;
	fl6.fl6_dport = otcph->source;

	if (hook == NF_INET_PRE_ROUTING \|\| hook == NF_INET_INGRESS) {
	nf_ip6_route(net, &dst, flowi6_to_flowi(&fl6), false);
	if (!dst)
	return;
	skb_dst_set(oldskb, dst);
	}

	fl6.flowi6_oif = l3mdev_master_ifindex(skb_dst(oldskb)->dev);
	fl6.flowi6_mark = IP6_REPLY_MARK(net, oldskb->mark);
	security_skb_classify_flow(oldskb, flowi6_to_flowi_common(&fl6));
	dst = ip6_route_output(net, NULL, &fl6);
	if (dst->error) {
	dst_release(dst);
	return;
	}
	dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0);
	if (IS_ERR(dst))
	return;

	hh_len = (dst->dev->hard_header_len + 15)&~15;
	nskb = alloc_skb(hh_len + 15 + dst->header_len + sizeof(struct ipv6hdr)
	+ sizeof(struct tcphdr) + dst->trailer_len,
	GFP_ATOMIC);

	if (!nskb) {
	net_dbg_ratelimited("cannot alloc skb\n");
	dst_release(dst);
	return;
	}

	skb_dst_set(nskb, dst);

	nskb->mark = fl6.flowi6_mark;

	skb_reserve(nskb, hh_len + dst->header_len);
	ip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_TCP,
	ip6_dst_hoplimit(dst));
	nf_reject_ip6_tcphdr_put(nskb, oldskb, otcph, otcplen);

	nf_ct_attach(nskb, oldskb);
	nf_ct_set_closing(skb_nfct(oldskb));

	#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
	/* If we use ip6_local_out for bridged traffic, the MAC source on
	* the RST will be ours, instead of the destination's. This confuses
	* some routers/firewalls, and they drop the packet. So we need to
	* build the eth header using the original destination's MAC as the
	* source, and send the RST packet directly.
	*/
	if (nf_bridge_info_exists(oldskb)) {
	struct ethhdr *oeth = eth_hdr(oldskb);
	struct net_device *br_indev;

	br_indev = nf_bridge_get_physindev(oldskb, net);
	if (!br_indev) {
	kfree_skb(nskb);
	return;
	}

	nskb->dev = br_indev;
	nskb->protocol = htons(ETH_P_IPV6);
	ip6h->payload_len = htons(sizeof(struct tcphdr));
	if (dev_hard_header(nskb, nskb->dev, ntohs(nskb->protocol),
	oeth->h_source, oeth->h_dest, nskb->len) < 0) {
	kfree_skb(nskb);
	return;
	}
	dev_queue_xmit(nskb);
	} else
	#endif
	ip6_local_out(net, sk, nskb);
	}
	EXPORT_SYMBOL_GPL(nf_send_reset6);

	static bool reject6_csum_ok(struct sk_buff *skb, int hook)
	{
	const struct ipv6hdr *ip6h = ipv6_hdr(skb);
	int thoff;
	__be16 fo;
	u8 proto;

	if (skb_csum_unnecessary(skb))
	return true;

	proto = ip6h->nexthdr;
	thoff = ipv6_skip_exthdr(skb, ((u8 *)(ip6h + 1) - skb->data), &proto, &fo);

	if (thoff < 0 \|\| thoff >= skb->len \|\| (fo & htons(~0x7)) != 0)
	return false;

	if (!nf_reject_verify_csum(skb, thoff, proto))
	return true;

	return nf_ip6_checksum(skb, hook, thoff, proto) == 0;
	}

	void nf_send_unreach6(struct net net, struct sk_buff skb_in,
	unsigned char code, unsigned int hooknum)
	{
	if (!reject6_csum_ok(skb_in, hooknum))
	return;

	if (hooknum == NF_INET_LOCAL_OUT && skb_in->dev == NULL)
	skb_in->dev = net->loopback_dev;

	if ((hooknum == NF_INET_PRE_ROUTING \|\| hooknum == NF_INET_INGRESS) &&
	nf_reject6_fill_skb_dst(skb_in) < 0)
	return;

	icmpv6_send(skb_in, ICMPV6_DEST_UNREACH, code, 0);
	}
	EXPORT_SYMBOL_GPL(nf_send_unreach6);

	MODULE_LICENSE("GPL");
	MODULE_DESCRIPTION("IPv6 packet rejection core");