net/ipv6/seg6_iptunnel.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *  SR-IPv6 implementation
  *
  *  Author:
  *  David Lebrun <david.lebrun@uclouvain.be>
  */

 #include <linux/types.h>
 #include <linux/skbuff.h>
 #include <linux/net.h>
 #include <linux/module.h>
 #include <net/ip.h>
 #include <net/ip_tunnels.h>
 #include <net/lwtunnel.h>
 #include <net/netevent.h>
 #include <net/netns/generic.h>
 #include <net/ip6_fib.h>
 #include <net/route.h>
 #include <net/seg6.h>
 #include <linux/seg6.h>
 #include <linux/seg6_iptunnel.h>
 #include <net/addrconf.h>
 #include <net/ip6_route.h>
 #include <net/dst_cache.h>
 #ifdef CONFIG_IPV6_SEG6_HMAC
 #include <net/seg6_hmac.h>
 #endif
 #include <linux/netfilter.h>

 static size_t seg6_lwt_headroom(struct seg6_iptunnel_encap *tuninfo)
 {
 	int head = 0;

 	switch (tuninfo->mode) {
 	case SEG6_IPTUN_MODE_INLINE:
 		break;
 	case SEG6_IPTUN_MODE_ENCAP:
 		head = sizeof(struct ipv6hdr);
 		break;
 	case SEG6_IPTUN_MODE_L2ENCAP:
 		return 0;
 	}

 	return ((tuninfo->srh->hdrlen + 1) << 3) + head;
 }

 struct seg6_lwt {
 	struct dst_cache cache;
 	struct seg6_iptunnel_encap tuninfo[];
 };

 static inline struct seg6_lwt *seg6_lwt_lwtunnel(struct lwtunnel_state *lwt)
 {
 	return (struct seg6_lwt *)lwt->data;
 }

 static inline struct seg6_iptunnel_encap *
 seg6_encap_lwtunnel(struct lwtunnel_state *lwt)
 {
 	return seg6_lwt_lwtunnel(lwt)->tuninfo;
 }

 static const struct nla_policy seg6_iptunnel_policy[SEG6_IPTUNNEL_MAX + 1] = {
 	[SEG6_IPTUNNEL_SRH]	= { .type = NLA_BINARY },
 };

 static int nla_put_srh(struct sk_buff *skb, int attrtype,
 		       struct seg6_iptunnel_encap *tuninfo)
 {
 	struct seg6_iptunnel_encap *data;
 	struct nlattr *nla;
 	int len;

 	len = SEG6_IPTUN_ENCAP_SIZE(tuninfo);

 	nla = nla_reserve(skb, attrtype, len);
 	if (!nla)
 		return -EMSGSIZE;

 	data = nla_data(nla);
 	memcpy(data, tuninfo, len);

 	return 0;
 }

 static void set_tun_src(struct net *net, struct net_device *dev,
 			struct in6_addr *daddr, struct in6_addr *saddr)
 {
 	struct seg6_pernet_data *sdata = seg6_pernet(net);
 	struct in6_addr *tun_src;

 	rcu_read_lock();

 	tun_src = rcu_dereference(sdata->tun_src);

 	if (!ipv6_addr_any(tun_src)) {
 		memcpy(saddr, tun_src, sizeof(struct in6_addr));
 	} else {
 		ipv6_dev_get_saddr(net, dev, daddr, IPV6_PREFER_SRC_PUBLIC,
 				   saddr);
 	}

 	rcu_read_unlock();
 }

 /* Compute flowlabel for outer IPv6 header */
 static __be32 seg6_make_flowlabel(struct net *net, struct sk_buff *skb,
 				  struct ipv6hdr *inner_hdr)
 {
 	int do_flowlabel = net->ipv6.sysctl.seg6_flowlabel;
 	__be32 flowlabel = 0;
 	u32 hash;

 	if (do_flowlabel > 0) {
 		hash = skb_get_hash(skb);
 		hash = rol32(hash, 16);
 		flowlabel = (__force __be32)hash & IPV6_FLOWLABEL_MASK;
 	} else if (!do_flowlabel && skb->protocol == htons(ETH_P_IPV6)) {
 		flowlabel = ip6_flowlabel(inner_hdr);
 	}
 	return flowlabel;
 }

 /* encapsulate an IPv6 packet within an outer IPv6 header with a given SRH */
 int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh, int proto)
 {
 	struct dst_entry *dst = skb_dst(skb);
 	struct net *net = dev_net(dst->dev);
 	struct ipv6hdr *hdr, *inner_hdr;
 	struct ipv6_sr_hdr *isrh;
 	int hdrlen, tot_len, err;
 	__be32 flowlabel;

 	hdrlen = (osrh->hdrlen + 1) << 3;
 	tot_len = hdrlen + sizeof(*hdr);

 	err = skb_cow_head(skb, tot_len + skb->mac_len);
 	if (unlikely(err))
 		return err;

 	inner_hdr = ipv6_hdr(skb);
 	flowlabel = seg6_make_flowlabel(net, skb, inner_hdr);

 	skb_push(skb, tot_len);
 	skb_reset_network_header(skb);
 	skb_mac_header_rebuild(skb);
 	hdr = ipv6_hdr(skb);

 	/* inherit tc, flowlabel and hlim
 	 * hlim will be decremented in ip6_forward() afterwards and
 	 * decapsulation will overwrite inner hlim with outer hlim
 	 */

 	if (skb->protocol == htons(ETH_P_IPV6)) {
 		ip6_flow_hdr(hdr, ip6_tclass(ip6_flowinfo(inner_hdr)),
 			     flowlabel);
 		hdr->hop_limit = inner_hdr->hop_limit;
 	} else {
 		ip6_flow_hdr(hdr, 0, flowlabel);
 		hdr->hop_limit = ip6_dst_hoplimit(skb_dst(skb));

 		memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));

 		/* the control block has been erased, so we have to set the
 		 * iif once again.
 		 * We read the receiving interface index directly from the
 		 * skb->skb_iif as it is done in the IPv4 receiving path (i.e.:
 		 * ip_rcv_core(...)).
 		 */
 		IP6CB(skb)->iif = skb->skb_iif;
 	}

 	hdr->nexthdr = NEXTHDR_ROUTING;

 	isrh = (void *)hdr + sizeof(*hdr);
 	memcpy(isrh, osrh, hdrlen);

 	isrh->nexthdr = proto;

 	hdr->daddr = isrh->segments[isrh->first_segment];
 	set_tun_src(net, dst->dev, &hdr->daddr, &hdr->saddr);

 #ifdef CONFIG_IPV6_SEG6_HMAC
 	if (sr_has_hmac(isrh)) {
 		err = seg6_push_hmac(net, &hdr->saddr, isrh);
 		if (unlikely(err))
 			return err;
 	}
 #endif

 	hdr->payload_len = htons(skb->len - sizeof(struct ipv6hdr));

 	skb_postpush_rcsum(skb, hdr, tot_len);

 	return 0;
 }
 EXPORT_SYMBOL_GPL(seg6_do_srh_encap);

 /* insert an SRH within an IPv6 packet, just after the IPv6 header */
 int seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh)
 {
 	struct ipv6hdr *hdr, *oldhdr;
 	struct ipv6_sr_hdr *isrh;
 	int hdrlen, err;

 	hdrlen = (osrh->hdrlen + 1) << 3;

 	err = skb_cow_head(skb, hdrlen + skb->mac_len);
 	if (unlikely(err))
 		return err;

 	oldhdr = ipv6_hdr(skb);

 	skb_pull(skb, sizeof(struct ipv6hdr));
 	skb_postpull_rcsum(skb, skb_network_header(skb),
 			   sizeof(struct ipv6hdr));

 	skb_push(skb, sizeof(struct ipv6hdr) + hdrlen);
 	skb_reset_network_header(skb);
 	skb_mac_header_rebuild(skb);

 	hdr = ipv6_hdr(skb);

 	memmove(hdr, oldhdr, sizeof(*hdr));

 	isrh = (void *)hdr + sizeof(*hdr);
 	memcpy(isrh, osrh, hdrlen);

 	isrh->nexthdr = hdr->nexthdr;
 	hdr->nexthdr = NEXTHDR_ROUTING;

 	isrh->segments[0] = hdr->daddr;
 	hdr->daddr = isrh->segments[isrh->first_segment];

 #ifdef CONFIG_IPV6_SEG6_HMAC
 	if (sr_has_hmac(isrh)) {
 		struct net *net = dev_net(skb_dst(skb)->dev);

 		err = seg6_push_hmac(net, &hdr->saddr, isrh);
 		if (unlikely(err))
 			return err;
 	}
 #endif

 	hdr->payload_len = htons(skb->len - sizeof(struct ipv6hdr));

 	skb_postpush_rcsum(skb, hdr, sizeof(struct ipv6hdr) + hdrlen);

 	return 0;
 }
 EXPORT_SYMBOL_GPL(seg6_do_srh_inline);

 static int seg6_do_srh(struct sk_buff *skb)
 {
 	struct dst_entry *dst = skb_dst(skb);
 	struct seg6_iptunnel_encap *tinfo;
 	int proto, err = 0;

 	tinfo = seg6_encap_lwtunnel(dst->lwtstate);

 	switch (tinfo->mode) {
 	case SEG6_IPTUN_MODE_INLINE:
 		if (skb->protocol != htons(ETH_P_IPV6))
 			return -EINVAL;

 		err = seg6_do_srh_inline(skb, tinfo->srh);
 		if (err)
 			return err;
 		break;
 	case SEG6_IPTUN_MODE_ENCAP:
 		err = iptunnel_handle_offloads(skb, SKB_GSO_IPXIP6);
 		if (err)
 			return err;

 		if (skb->protocol == htons(ETH_P_IPV6))
 			proto = IPPROTO_IPV6;
 		else if (skb->protocol == htons(ETH_P_IP))
 			proto = IPPROTO_IPIP;
 		else
 			return -EINVAL;

 		err = seg6_do_srh_encap(skb, tinfo->srh, proto);
 		if (err)
 			return err;

 		skb_set_inner_transport_header(skb, skb_transport_offset(skb));
 		skb_set_inner_protocol(skb, skb->protocol);
 		skb->protocol = htons(ETH_P_IPV6);
 		break;
 	case SEG6_IPTUN_MODE_L2ENCAP:
 		if (!skb_mac_header_was_set(skb))
 			return -EINVAL;

 		if (pskb_expand_head(skb, skb->mac_len, 0, GFP_ATOMIC) < 0)
 			return -ENOMEM;

 		skb_mac_header_rebuild(skb);
 		skb_push(skb, skb->mac_len);

 		err = seg6_do_srh_encap(skb, tinfo->srh, IPPROTO_ETHERNET);
 		if (err)
 			return err;

 		skb->protocol = htons(ETH_P_IPV6);
 		break;
 	}

 	skb_set_transport_header(skb, sizeof(struct ipv6hdr));
 	nf_reset_ct(skb);

 	return 0;
 }

 static int seg6_input_finish(struct net *net, struct sock *sk,
 			     struct sk_buff *skb)
 {
 	return dst_input(skb);
 }

 static int seg6_input_core(struct net *net, struct sock *sk,
 			   struct sk_buff *skb)
 {
 	struct dst_entry *orig_dst = skb_dst(skb);
 	struct dst_entry *dst = NULL;
 	struct seg6_lwt *slwt;
 	int err;

 	err = seg6_do_srh(skb);
 	if (unlikely(err)) {
 		kfree_skb(skb);
 		return err;
 	}

 	slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);

 	preempt_disable();
 	dst = dst_cache_get(&slwt->cache);
 	preempt_enable();

 	skb_dst_drop(skb);

 	if (!dst) {
 		ip6_route_input(skb);
 		dst = skb_dst(skb);
 		if (!dst->error) {
 			preempt_disable();
 			dst_cache_set_ip6(&slwt->cache, dst,
 					  &ipv6_hdr(skb)->saddr);
 			preempt_enable();
 		}
 	} else {
 		skb_dst_set(skb, dst);
 	}

 	err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
 	if (unlikely(err))
 		return err;

 	if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))
 		return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT,
 			       dev_net(skb->dev), NULL, skb, NULL,
 			       skb_dst(skb)->dev, seg6_input_finish);

 	return seg6_input_finish(dev_net(skb->dev), NULL, skb);
 }

 static int seg6_input_nf(struct sk_buff *skb)
 {
 	struct net_device *dev = skb_dst(skb)->dev;
 	struct net *net = dev_net(skb->dev);

 	switch (skb->protocol) {
 	case htons(ETH_P_IP):
 		return NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING, net, NULL,
 			       skb, NULL, dev, seg6_input_core);
 	case htons(ETH_P_IPV6):
 		return NF_HOOK(NFPROTO_IPV6, NF_INET_POST_ROUTING, net, NULL,
 			       skb, NULL, dev, seg6_input_core);
 	}

 	return -EINVAL;
 }

 static int seg6_input(struct sk_buff *skb)
 {
 	if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))
 		return seg6_input_nf(skb);

 	return seg6_input_core(dev_net(skb->dev), NULL, skb);
 }

 static int seg6_output_core(struct net *net, struct sock *sk,
 			    struct sk_buff *skb)
 {
 	struct dst_entry *orig_dst = skb_dst(skb);
 	struct dst_entry *dst = NULL;
 	struct seg6_lwt *slwt;
 	int err;

 	err = seg6_do_srh(skb);
 	if (unlikely(err))
 		goto drop;

 	slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);

 	preempt_disable();
 	dst = dst_cache_get(&slwt->cache);
 	preempt_enable();

 	if (unlikely(!dst)) {
 		struct ipv6hdr *hdr = ipv6_hdr(skb);
 		struct flowi6 fl6;

 		memset(&fl6, 0, sizeof(fl6));
 		fl6.daddr = hdr->daddr;
 		fl6.saddr = hdr->saddr;
 		fl6.flowlabel = ip6_flowinfo(hdr);
 		fl6.flowi6_mark = skb->mark;
 		fl6.flowi6_proto = hdr->nexthdr;

 		dst = ip6_route_output(net, NULL, &fl6);
 		if (dst->error) {
 			err = dst->error;
 			dst_release(dst);
 			goto drop;
 		}

 		preempt_disable();
 		dst_cache_set_ip6(&slwt->cache, dst, &fl6.saddr);
 		preempt_enable();
 	}

 	skb_dst_drop(skb);
 	skb_dst_set(skb, dst);

 	err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
 	if (unlikely(err))
 		goto drop;

 	if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))
 		return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT, net, sk, skb,
 			       NULL, skb_dst(skb)->dev, dst_output);

 	return dst_output(net, sk, skb);
 drop:
 	kfree_skb(skb);
 	return err;
 }

 static int seg6_output_nf(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
 	struct net_device *dev = skb_dst(skb)->dev;

 	switch (skb->protocol) {
 	case htons(ETH_P_IP):
 		return NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING, net, sk, skb,
 			       NULL, dev, seg6_output_core);
 	case htons(ETH_P_IPV6):
 		return NF_HOOK(NFPROTO_IPV6, NF_INET_POST_ROUTING, net, sk, skb,
 			       NULL, dev, seg6_output_core);
 	}

 	return -EINVAL;
 }

 static int seg6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
 	if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))
 		return seg6_output_nf(net, sk, skb);

 	return seg6_output_core(net, sk, skb);
 }

 static int seg6_build_state(struct net *net, struct nlattr *nla,
 			    unsigned int family, const void *cfg,
 			    struct lwtunnel_state **ts,
 			    struct netlink_ext_ack *extack)
 {
 	struct nlattr *tb[SEG6_IPTUNNEL_MAX + 1];
 	struct seg6_iptunnel_encap *tuninfo;
 	struct lwtunnel_state *newts;
 	int tuninfo_len, min_size;
 	struct seg6_lwt *slwt;
 	int err;

 	if (family != AF_INET && family != AF_INET6)
 		return -EINVAL;

 	err = nla_parse_nested_deprecated(tb, SEG6_IPTUNNEL_MAX, nla,
 					  seg6_iptunnel_policy, extack);

 	if (err < 0)
 		return err;

 	if (!tb[SEG6_IPTUNNEL_SRH])
 		return -EINVAL;

 	tuninfo = nla_data(tb[SEG6_IPTUNNEL_SRH]);
 	tuninfo_len = nla_len(tb[SEG6_IPTUNNEL_SRH]);

 	/* tuninfo must contain at least the iptunnel encap structure,
 	 * the SRH and one segment
 	 */
 	min_size = sizeof(*tuninfo) + sizeof(struct ipv6_sr_hdr) +
 		   sizeof(struct in6_addr);
 	if (tuninfo_len < min_size)
 		return -EINVAL;

 	switch (tuninfo->mode) {
 	case SEG6_IPTUN_MODE_INLINE:
 		if (family != AF_INET6)
 			return -EINVAL;

 		break;
 	case SEG6_IPTUN_MODE_ENCAP:
 		break;
 	case SEG6_IPTUN_MODE_L2ENCAP:
 		break;
 	default:
 		return -EINVAL;
 	}

 	/* verify that SRH is consistent */
 	if (!seg6_validate_srh(tuninfo->srh, tuninfo_len - sizeof(*tuninfo), false))
 		return -EINVAL;

 	newts = lwtunnel_state_alloc(tuninfo_len + sizeof(*slwt));
 	if (!newts)
 		return -ENOMEM;

 	slwt = seg6_lwt_lwtunnel(newts);

 	err = dst_cache_init(&slwt->cache, GFP_ATOMIC);
 	if (err) {
 		kfree(newts);
 		return err;
 	}

 	memcpy(&slwt->tuninfo, tuninfo, tuninfo_len);

 	newts->type = LWTUNNEL_ENCAP_SEG6;
 	newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT;

 	if (tuninfo->mode != SEG6_IPTUN_MODE_L2ENCAP)
 		newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;

 	newts->headroom = seg6_lwt_headroom(tuninfo);

 	*ts = newts;

 	return 0;
 }

 static void seg6_destroy_state(struct lwtunnel_state *lwt)
 {
 	dst_cache_destroy(&seg6_lwt_lwtunnel(lwt)->cache);
 }

 static int seg6_fill_encap_info(struct sk_buff *skb,
 				struct lwtunnel_state *lwtstate)
 {
 	struct seg6_iptunnel_encap *tuninfo = seg6_encap_lwtunnel(lwtstate);

 	if (nla_put_srh(skb, SEG6_IPTUNNEL_SRH, tuninfo))
 		return -EMSGSIZE;

 	return 0;
 }

 static int seg6_encap_nlsize(struct lwtunnel_state *lwtstate)
 {
 	struct seg6_iptunnel_encap *tuninfo = seg6_encap_lwtunnel(lwtstate);

 	return nla_total_size(SEG6_IPTUN_ENCAP_SIZE(tuninfo));
 }

 static int seg6_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
 {
 	struct seg6_iptunnel_encap *a_hdr = seg6_encap_lwtunnel(a);
 	struct seg6_iptunnel_encap *b_hdr = seg6_encap_lwtunnel(b);
 	int len = SEG6_IPTUN_ENCAP_SIZE(a_hdr);

 	if (len != SEG6_IPTUN_ENCAP_SIZE(b_hdr))
 		return 1;

 	return memcmp(a_hdr, b_hdr, len);
 }

 static const struct lwtunnel_encap_ops seg6_iptun_ops = {
 	.build_state = seg6_build_state,
 	.destroy_state = seg6_destroy_state,
 	.output = seg6_output,
 	.input = seg6_input,
 	.fill_encap = seg6_fill_encap_info,
 	.get_encap_size = seg6_encap_nlsize,
 	.cmp_encap = seg6_encap_cmp,
 	.owner = THIS_MODULE,
 };

 int __init seg6_iptunnel_init(void)
 {
 	return lwtunnel_encap_add_ops(&seg6_iptun_ops, LWTUNNEL_ENCAP_SEG6);
 }

 void seg6_iptunnel_exit(void)
 {
 	lwtunnel_encap_del_ops(&seg6_iptun_ops, LWTUNNEL_ENCAP_SEG6);
 }
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* SR-IPv6 implementation
	*
	* Author:
	* David Lebrun <david.lebrun@uclouvain.be>
	*/

	#include <linux/types.h>
	#include <linux/skbuff.h>
	#include <linux/net.h>
	#include <linux/module.h>
	#include <net/ip.h>
	#include <net/ip_tunnels.h>
	#include <net/lwtunnel.h>
	#include <net/netevent.h>
	#include <net/netns/generic.h>
	#include <net/ip6_fib.h>
	#include <net/route.h>
	#include <net/seg6.h>
	#include <linux/seg6.h>
	#include <linux/seg6_iptunnel.h>
	#include <net/addrconf.h>
	#include <net/ip6_route.h>
	#include <net/dst_cache.h>
	#ifdef CONFIG_IPV6_SEG6_HMAC
	#include <net/seg6_hmac.h>
	#endif
	#include <linux/netfilter.h>

	static size_t seg6_lwt_headroom(struct seg6_iptunnel_encap *tuninfo)
	{
	int head = 0;

	switch (tuninfo->mode) {
	case SEG6_IPTUN_MODE_INLINE:
	break;
	case SEG6_IPTUN_MODE_ENCAP:
	head = sizeof(struct ipv6hdr);
	break;
	case SEG6_IPTUN_MODE_L2ENCAP:
	return 0;
	}

	return ((tuninfo->srh->hdrlen + 1) << 3) + head;
	}

	struct seg6_lwt {
	struct dst_cache cache;
	struct seg6_iptunnel_encap tuninfo[];
	};

	static inline struct seg6_lwt seg6_lwt_lwtunnel(struct lwtunnel_state lwt)
	{
	return (struct seg6_lwt *)lwt->data;
	}

	static inline struct seg6_iptunnel_encap *
	seg6_encap_lwtunnel(struct lwtunnel_state *lwt)
	{
	return seg6_lwt_lwtunnel(lwt)->tuninfo;
	}

	static const struct nla_policy seg6_iptunnel_policy[SEG6_IPTUNNEL_MAX + 1] = {
	[SEG6_IPTUNNEL_SRH] = { .type = NLA_BINARY },
	};

	static int nla_put_srh(struct sk_buff *skb, int attrtype,
	struct seg6_iptunnel_encap *tuninfo)
	{
	struct seg6_iptunnel_encap *data;
	struct nlattr *nla;
	int len;

	len = SEG6_IPTUN_ENCAP_SIZE(tuninfo);

	nla = nla_reserve(skb, attrtype, len);
	if (!nla)
	return -EMSGSIZE;

	data = nla_data(nla);
	memcpy(data, tuninfo, len);

	return 0;
	}

	static void set_tun_src(struct net net, struct net_device dev,
	struct in6_addr daddr, struct in6_addr saddr)
	{
	struct seg6_pernet_data *sdata = seg6_pernet(net);
	struct in6_addr *tun_src;

	rcu_read_lock();

	tun_src = rcu_dereference(sdata->tun_src);

	if (!ipv6_addr_any(tun_src)) {
	memcpy(saddr, tun_src, sizeof(struct in6_addr));
	} else {
	ipv6_dev_get_saddr(net, dev, daddr, IPV6_PREFER_SRC_PUBLIC,
	saddr);
	}

	rcu_read_unlock();
	}

	/* Compute flowlabel for outer IPv6 header */
	static __be32 seg6_make_flowlabel(struct net net, struct sk_buff skb,
	struct ipv6hdr *inner_hdr)
	{
	int do_flowlabel = net->ipv6.sysctl.seg6_flowlabel;
	__be32 flowlabel = 0;
	u32 hash;

	if (do_flowlabel > 0) {
	hash = skb_get_hash(skb);
	hash = rol32(hash, 16);
	flowlabel = (__force __be32)hash & IPV6_FLOWLABEL_MASK;
	} else if (!do_flowlabel && skb->protocol == htons(ETH_P_IPV6)) {
	flowlabel = ip6_flowlabel(inner_hdr);
	}
	return flowlabel;
	}

	/* encapsulate an IPv6 packet within an outer IPv6 header with a given SRH */
	int seg6_do_srh_encap(struct sk_buff skb, struct ipv6_sr_hdr osrh, int proto)
	{
	struct dst_entry *dst = skb_dst(skb);
	struct net *net = dev_net(dst->dev);
	struct ipv6hdr hdr, inner_hdr;
	struct ipv6_sr_hdr *isrh;
	int hdrlen, tot_len, err;
	__be32 flowlabel;

	hdrlen = (osrh->hdrlen + 1) << 3;
	tot_len = hdrlen + sizeof(*hdr);

	err = skb_cow_head(skb, tot_len + skb->mac_len);
	if (unlikely(err))
	return err;

	inner_hdr = ipv6_hdr(skb);
	flowlabel = seg6_make_flowlabel(net, skb, inner_hdr);

	skb_push(skb, tot_len);
	skb_reset_network_header(skb);
	skb_mac_header_rebuild(skb);
	hdr = ipv6_hdr(skb);

	/* inherit tc, flowlabel and hlim
	* hlim will be decremented in ip6_forward() afterwards and
	* decapsulation will overwrite inner hlim with outer hlim
	*/

	if (skb->protocol == htons(ETH_P_IPV6)) {
	ip6_flow_hdr(hdr, ip6_tclass(ip6_flowinfo(inner_hdr)),
	flowlabel);
	hdr->hop_limit = inner_hdr->hop_limit;
	} else {
	ip6_flow_hdr(hdr, 0, flowlabel);
	hdr->hop_limit = ip6_dst_hoplimit(skb_dst(skb));

	memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));

	/* the control block has been erased, so we have to set the
	* iif once again.
	* We read the receiving interface index directly from the
	* skb->skb_iif as it is done in the IPv4 receiving path (i.e.:
	* ip_rcv_core(...)).
	*/
	IP6CB(skb)->iif = skb->skb_iif;
	}

	hdr->nexthdr = NEXTHDR_ROUTING;

	isrh = (void )hdr + sizeof(hdr);
	memcpy(isrh, osrh, hdrlen);

	isrh->nexthdr = proto;

	hdr->daddr = isrh->segments[isrh->first_segment];
	set_tun_src(net, dst->dev, &hdr->daddr, &hdr->saddr);

	#ifdef CONFIG_IPV6_SEG6_HMAC
	if (sr_has_hmac(isrh)) {
	err = seg6_push_hmac(net, &hdr->saddr, isrh);
	if (unlikely(err))
	return err;
	}
	#endif

	hdr->payload_len = htons(skb->len - sizeof(struct ipv6hdr));

	skb_postpush_rcsum(skb, hdr, tot_len);

	return 0;
	}
	EXPORT_SYMBOL_GPL(seg6_do_srh_encap);

	/* insert an SRH within an IPv6 packet, just after the IPv6 header */
	int seg6_do_srh_inline(struct sk_buff skb, struct ipv6_sr_hdr osrh)
	{
	struct ipv6hdr hdr, oldhdr;
	struct ipv6_sr_hdr *isrh;
	int hdrlen, err;

	hdrlen = (osrh->hdrlen + 1) << 3;

	err = skb_cow_head(skb, hdrlen + skb->mac_len);
	if (unlikely(err))
	return err;

	oldhdr = ipv6_hdr(skb);

	skb_pull(skb, sizeof(struct ipv6hdr));
	skb_postpull_rcsum(skb, skb_network_header(skb),
	sizeof(struct ipv6hdr));

	skb_push(skb, sizeof(struct ipv6hdr) + hdrlen);
	skb_reset_network_header(skb);
	skb_mac_header_rebuild(skb);

	hdr = ipv6_hdr(skb);

	memmove(hdr, oldhdr, sizeof(*hdr));

	isrh = (void )hdr + sizeof(hdr);
	memcpy(isrh, osrh, hdrlen);

	isrh->nexthdr = hdr->nexthdr;
	hdr->nexthdr = NEXTHDR_ROUTING;

	isrh->segments[0] = hdr->daddr;
	hdr->daddr = isrh->segments[isrh->first_segment];

	#ifdef CONFIG_IPV6_SEG6_HMAC
	if (sr_has_hmac(isrh)) {
	struct net *net = dev_net(skb_dst(skb)->dev);

	err = seg6_push_hmac(net, &hdr->saddr, isrh);
	if (unlikely(err))
	return err;
	}
	#endif

	hdr->payload_len = htons(skb->len - sizeof(struct ipv6hdr));

	skb_postpush_rcsum(skb, hdr, sizeof(struct ipv6hdr) + hdrlen);

	return 0;
	}
	EXPORT_SYMBOL_GPL(seg6_do_srh_inline);

	static int seg6_do_srh(struct sk_buff *skb)
	{
	struct dst_entry *dst = skb_dst(skb);
	struct seg6_iptunnel_encap *tinfo;
	int proto, err = 0;

	tinfo = seg6_encap_lwtunnel(dst->lwtstate);

	switch (tinfo->mode) {
	case SEG6_IPTUN_MODE_INLINE:
	if (skb->protocol != htons(ETH_P_IPV6))
	return -EINVAL;

	err = seg6_do_srh_inline(skb, tinfo->srh);
	if (err)
	return err;
	break;
	case SEG6_IPTUN_MODE_ENCAP:
	err = iptunnel_handle_offloads(skb, SKB_GSO_IPXIP6);
	if (err)
	return err;

	if (skb->protocol == htons(ETH_P_IPV6))
	proto = IPPROTO_IPV6;
	else if (skb->protocol == htons(ETH_P_IP))
	proto = IPPROTO_IPIP;
	else
	return -EINVAL;

	err = seg6_do_srh_encap(skb, tinfo->srh, proto);
	if (err)
	return err;

	skb_set_inner_transport_header(skb, skb_transport_offset(skb));
	skb_set_inner_protocol(skb, skb->protocol);
	skb->protocol = htons(ETH_P_IPV6);
	break;
	case SEG6_IPTUN_MODE_L2ENCAP:
	if (!skb_mac_header_was_set(skb))
	return -EINVAL;

	if (pskb_expand_head(skb, skb->mac_len, 0, GFP_ATOMIC) < 0)
	return -ENOMEM;

	skb_mac_header_rebuild(skb);
	skb_push(skb, skb->mac_len);

	err = seg6_do_srh_encap(skb, tinfo->srh, IPPROTO_ETHERNET);
	if (err)
	return err;

	skb->protocol = htons(ETH_P_IPV6);
	break;
	}

	skb_set_transport_header(skb, sizeof(struct ipv6hdr));
	nf_reset_ct(skb);

	return 0;
	}

	static int seg6_input_finish(struct net net, struct sock sk,
	struct sk_buff *skb)
	{
	return dst_input(skb);
	}

	static int seg6_input_core(struct net net, struct sock sk,
	struct sk_buff *skb)
	{
	struct dst_entry *orig_dst = skb_dst(skb);
	struct dst_entry *dst = NULL;
	struct seg6_lwt *slwt;
	int err;

	err = seg6_do_srh(skb);
	if (unlikely(err)) {
	kfree_skb(skb);
	return err;
	}

	slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);

	preempt_disable();
	dst = dst_cache_get(&slwt->cache);
	preempt_enable();

	skb_dst_drop(skb);

	if (!dst) {
	ip6_route_input(skb);
	dst = skb_dst(skb);
	if (!dst->error) {
	preempt_disable();
	dst_cache_set_ip6(&slwt->cache, dst,
	&ipv6_hdr(skb)->saddr);
	preempt_enable();
	}
	} else {
	skb_dst_set(skb, dst);
	}

	err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
	if (unlikely(err))
	return err;

	if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))
	return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT,
	dev_net(skb->dev), NULL, skb, NULL,
	skb_dst(skb)->dev, seg6_input_finish);

	return seg6_input_finish(dev_net(skb->dev), NULL, skb);
	}

	static int seg6_input_nf(struct sk_buff *skb)
	{
	struct net_device *dev = skb_dst(skb)->dev;
	struct net *net = dev_net(skb->dev);

	switch (skb->protocol) {
	case htons(ETH_P_IP):
	return NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING, net, NULL,
	skb, NULL, dev, seg6_input_core);
	case htons(ETH_P_IPV6):
	return NF_HOOK(NFPROTO_IPV6, NF_INET_POST_ROUTING, net, NULL,
	skb, NULL, dev, seg6_input_core);
	}

	return -EINVAL;
	}

	static int seg6_input(struct sk_buff *skb)
	{
	if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))
	return seg6_input_nf(skb);

	return seg6_input_core(dev_net(skb->dev), NULL, skb);
	}

	static int seg6_output_core(struct net net, struct sock sk,
	struct sk_buff *skb)
	{
	struct dst_entry *orig_dst = skb_dst(skb);
	struct dst_entry *dst = NULL;
	struct seg6_lwt *slwt;
	int err;

	err = seg6_do_srh(skb);
	if (unlikely(err))
	goto drop;

	slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);

	preempt_disable();
	dst = dst_cache_get(&slwt->cache);
	preempt_enable();

	if (unlikely(!dst)) {
	struct ipv6hdr *hdr = ipv6_hdr(skb);
	struct flowi6 fl6;

	memset(&fl6, 0, sizeof(fl6));
	fl6.daddr = hdr->daddr;
	fl6.saddr = hdr->saddr;
	fl6.flowlabel = ip6_flowinfo(hdr);
	fl6.flowi6_mark = skb->mark;
	fl6.flowi6_proto = hdr->nexthdr;

	dst = ip6_route_output(net, NULL, &fl6);
	if (dst->error) {
	err = dst->error;
	dst_release(dst);
	goto drop;
	}

	preempt_disable();
	dst_cache_set_ip6(&slwt->cache, dst, &fl6.saddr);
	preempt_enable();
	}

	skb_dst_drop(skb);
	skb_dst_set(skb, dst);

	err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
	if (unlikely(err))
	goto drop;

	if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))
	return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT, net, sk, skb,
	NULL, skb_dst(skb)->dev, dst_output);

	return dst_output(net, sk, skb);
	drop:
	kfree_skb(skb);
	return err;
	}

	static int seg6_output_nf(struct net net, struct sock sk, struct sk_buff *skb)
	{
	struct net_device *dev = skb_dst(skb)->dev;

	switch (skb->protocol) {
	case htons(ETH_P_IP):
	return NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING, net, sk, skb,
	NULL, dev, seg6_output_core);
	case htons(ETH_P_IPV6):
	return NF_HOOK(NFPROTO_IPV6, NF_INET_POST_ROUTING, net, sk, skb,
	NULL, dev, seg6_output_core);
	}

	return -EINVAL;
	}

	static int seg6_output(struct net net, struct sock sk, struct sk_buff *skb)
	{
	if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))
	return seg6_output_nf(net, sk, skb);

	return seg6_output_core(net, sk, skb);
	}

	static int seg6_build_state(struct net net, struct nlattr nla,
	unsigned int family, const void *cfg,
	struct lwtunnel_state **ts,
	struct netlink_ext_ack *extack)
	{
	struct nlattr *tb[SEG6_IPTUNNEL_MAX + 1];
	struct seg6_iptunnel_encap *tuninfo;
	struct lwtunnel_state *newts;
	int tuninfo_len, min_size;
	struct seg6_lwt *slwt;
	int err;

	if (family != AF_INET && family != AF_INET6)
	return -EINVAL;

	err = nla_parse_nested_deprecated(tb, SEG6_IPTUNNEL_MAX, nla,
	seg6_iptunnel_policy, extack);

	if (err < 0)
	return err;

	if (!tb[SEG6_IPTUNNEL_SRH])
	return -EINVAL;

	tuninfo = nla_data(tb[SEG6_IPTUNNEL_SRH]);
	tuninfo_len = nla_len(tb[SEG6_IPTUNNEL_SRH]);

	/* tuninfo must contain at least the iptunnel encap structure,
	* the SRH and one segment
	*/
	min_size = sizeof(*tuninfo) + sizeof(struct ipv6_sr_hdr) +
	sizeof(struct in6_addr);
	if (tuninfo_len < min_size)
	return -EINVAL;

	switch (tuninfo->mode) {
	case SEG6_IPTUN_MODE_INLINE:
	if (family != AF_INET6)
	return -EINVAL;

	break;
	case SEG6_IPTUN_MODE_ENCAP:
	break;
	case SEG6_IPTUN_MODE_L2ENCAP:
	break;
	default:
	return -EINVAL;
	}

	/* verify that SRH is consistent */
	if (!seg6_validate_srh(tuninfo->srh, tuninfo_len - sizeof(*tuninfo), false))
	return -EINVAL;

	newts = lwtunnel_state_alloc(tuninfo_len + sizeof(*slwt));
	if (!newts)
	return -ENOMEM;

	slwt = seg6_lwt_lwtunnel(newts);

	err = dst_cache_init(&slwt->cache, GFP_ATOMIC);
	if (err) {
	kfree(newts);
	return err;
	}

	memcpy(&slwt->tuninfo, tuninfo, tuninfo_len);

	newts->type = LWTUNNEL_ENCAP_SEG6;
	newts->flags \|= LWTUNNEL_STATE_INPUT_REDIRECT;

	if (tuninfo->mode != SEG6_IPTUN_MODE_L2ENCAP)
	newts->flags \|= LWTUNNEL_STATE_OUTPUT_REDIRECT;

	newts->headroom = seg6_lwt_headroom(tuninfo);

	*ts = newts;

	return 0;
	}

	static void seg6_destroy_state(struct lwtunnel_state *lwt)
	{
	dst_cache_destroy(&seg6_lwt_lwtunnel(lwt)->cache);
	}

	static int seg6_fill_encap_info(struct sk_buff *skb,
	struct lwtunnel_state *lwtstate)
	{
	struct seg6_iptunnel_encap *tuninfo = seg6_encap_lwtunnel(lwtstate);

	if (nla_put_srh(skb, SEG6_IPTUNNEL_SRH, tuninfo))
	return -EMSGSIZE;

	return 0;
	}

	static int seg6_encap_nlsize(struct lwtunnel_state *lwtstate)
	{
	struct seg6_iptunnel_encap *tuninfo = seg6_encap_lwtunnel(lwtstate);

	return nla_total_size(SEG6_IPTUN_ENCAP_SIZE(tuninfo));
	}

	static int seg6_encap_cmp(struct lwtunnel_state a, struct lwtunnel_state b)
	{
	struct seg6_iptunnel_encap *a_hdr = seg6_encap_lwtunnel(a);
	struct seg6_iptunnel_encap *b_hdr = seg6_encap_lwtunnel(b);
	int len = SEG6_IPTUN_ENCAP_SIZE(a_hdr);

	if (len != SEG6_IPTUN_ENCAP_SIZE(b_hdr))
	return 1;

	return memcmp(a_hdr, b_hdr, len);
	}

	static const struct lwtunnel_encap_ops seg6_iptun_ops = {
	.build_state = seg6_build_state,
	.destroy_state = seg6_destroy_state,
	.output = seg6_output,
	.input = seg6_input,
	.fill_encap = seg6_fill_encap_info,
	.get_encap_size = seg6_encap_nlsize,
	.cmp_encap = seg6_encap_cmp,
	.owner = THIS_MODULE,
	};

	int __init seg6_iptunnel_init(void)
	{
	return lwtunnel_encap_add_ops(&seg6_iptun_ops, LWTUNNEL_ENCAP_SEG6);
	}

	void seg6_iptunnel_exit(void)
	{
	lwtunnel_encap_del_ops(&seg6_iptun_ops, LWTUNNEL_ENCAP_SEG6);
	}