net/ipv6/ioam6_iptunnel.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0+
 /*
  *  IPv6 IOAM Lightweight Tunnel implementation
  *
  *  Author:
  *  Justin Iurman <justin.iurman@uliege.be>
  */

 #include <linux/kernel.h>
 #include <linux/skbuff.h>
 #include <linux/net.h>
 #include <linux/in6.h>
 #include <linux/ioam6.h>
 #include <linux/ioam6_iptunnel.h>
 #include <net/dst.h>
 #include <net/sock.h>
 #include <net/lwtunnel.h>
 #include <net/ioam6.h>
 #include <net/netlink.h>
 #include <net/ipv6.h>
 #include <net/dst_cache.h>
 #include <net/ip6_route.h>
 #include <net/addrconf.h>

 #define IOAM6_MASK_SHORT_FIELDS 0xff100000
 #define IOAM6_MASK_WIDE_FIELDS 0xe00000

 struct ioam6_lwt_encap {
 	struct ipv6_hopopt_hdr eh;
 	u8 pad[2];			/* 2-octet padding for 4n-alignment */
 	struct ioam6_hdr ioamh;
 	struct ioam6_trace_hdr traceh;
 } __packed;

 struct ioam6_lwt_freq {
 	u32 k;
 	u32 n;
 };

 struct ioam6_lwt {
 	struct dst_cache cache;
 	struct ioam6_lwt_freq freq;
 	atomic_t pkt_cnt;
 	u8 mode;
 	struct in6_addr tundst;
 	struct ioam6_lwt_encap	tuninfo;
 };

 static const struct netlink_range_validation freq_range = {
 	.min = IOAM6_IPTUNNEL_FREQ_MIN,
 	.max = IOAM6_IPTUNNEL_FREQ_MAX,
 };

 static struct ioam6_lwt *ioam6_lwt_state(struct lwtunnel_state *lwt)
 {
 	return (struct ioam6_lwt *)lwt->data;
 }

 static struct ioam6_lwt_encap *ioam6_lwt_info(struct lwtunnel_state *lwt)
 {
 	return &ioam6_lwt_state(lwt)->tuninfo;
 }

 static struct ioam6_trace_hdr *ioam6_lwt_trace(struct lwtunnel_state *lwt)
 {
 	return &(ioam6_lwt_state(lwt)->tuninfo.traceh);
 }

 static const struct nla_policy ioam6_iptunnel_policy[IOAM6_IPTUNNEL_MAX + 1] = {
 	[IOAM6_IPTUNNEL_FREQ_K] = NLA_POLICY_FULL_RANGE(NLA_U32, &freq_range),
 	[IOAM6_IPTUNNEL_FREQ_N] = NLA_POLICY_FULL_RANGE(NLA_U32, &freq_range),
 	[IOAM6_IPTUNNEL_MODE]	= NLA_POLICY_RANGE(NLA_U8,
 						   IOAM6_IPTUNNEL_MODE_MIN,
 						   IOAM6_IPTUNNEL_MODE_MAX),
 	[IOAM6_IPTUNNEL_DST]	= NLA_POLICY_EXACT_LEN(sizeof(struct in6_addr)),
 	[IOAM6_IPTUNNEL_TRACE]	= NLA_POLICY_EXACT_LEN(sizeof(struct ioam6_trace_hdr)),
 };

 static bool ioam6_validate_trace_hdr(struct ioam6_trace_hdr *trace)
 {
 	u32 fields;

 	if (!trace->type_be32 || !trace->remlen ||
 	    trace->remlen > IOAM6_TRACE_DATA_SIZE_MAX / 4 ||
 	    trace->type.bit12 | trace->type.bit13 | trace->type.bit14 |
 	    trace->type.bit15 | trace->type.bit16 | trace->type.bit17 |
 	    trace->type.bit18 | trace->type.bit19 | trace->type.bit20 |
 	    trace->type.bit21)
 		return false;

 	trace->nodelen = 0;
 	fields = be32_to_cpu(trace->type_be32);

 	trace->nodelen += hweight32(fields & IOAM6_MASK_SHORT_FIELDS)
 				* (sizeof(__be32) / 4);
 	trace->nodelen += hweight32(fields & IOAM6_MASK_WIDE_FIELDS)
 				* (sizeof(__be64) / 4);

 	return true;
 }

 static int ioam6_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[IOAM6_IPTUNNEL_MAX + 1];
 	struct ioam6_lwt_encap *tuninfo;
 	struct ioam6_trace_hdr *trace;
 	struct lwtunnel_state *lwt;
 	struct ioam6_lwt *ilwt;
 	int len_aligned, err;
 	u32 freq_k, freq_n;
 	u8 mode;

 	if (family != AF_INET6)
 		return -EINVAL;

 	err = nla_parse_nested(tb, IOAM6_IPTUNNEL_MAX, nla,
 			       ioam6_iptunnel_policy, extack);
 	if (err < 0)
 		return err;

 	if ((!tb[IOAM6_IPTUNNEL_FREQ_K] && tb[IOAM6_IPTUNNEL_FREQ_N]) ||
 	    (tb[IOAM6_IPTUNNEL_FREQ_K] && !tb[IOAM6_IPTUNNEL_FREQ_N])) {
 		NL_SET_ERR_MSG(extack, "freq: missing parameter");
 		return -EINVAL;
 	} else if (!tb[IOAM6_IPTUNNEL_FREQ_K] && !tb[IOAM6_IPTUNNEL_FREQ_N]) {
 		freq_k = IOAM6_IPTUNNEL_FREQ_MIN;
 		freq_n = IOAM6_IPTUNNEL_FREQ_MIN;
 	} else {
 		freq_k = nla_get_u32(tb[IOAM6_IPTUNNEL_FREQ_K]);
 		freq_n = nla_get_u32(tb[IOAM6_IPTUNNEL_FREQ_N]);

 		if (freq_k > freq_n) {
 			NL_SET_ERR_MSG(extack, "freq: k > n is forbidden");
 			return -EINVAL;
 		}
 	}

 	if (!tb[IOAM6_IPTUNNEL_MODE])
 		mode = IOAM6_IPTUNNEL_MODE_INLINE;
 	else
 		mode = nla_get_u8(tb[IOAM6_IPTUNNEL_MODE]);

 	if (!tb[IOAM6_IPTUNNEL_DST] && mode != IOAM6_IPTUNNEL_MODE_INLINE) {
 		NL_SET_ERR_MSG(extack, "this mode needs a tunnel destination");
 		return -EINVAL;
 	}

 	if (!tb[IOAM6_IPTUNNEL_TRACE]) {
 		NL_SET_ERR_MSG(extack, "missing trace");
 		return -EINVAL;
 	}

 	trace = nla_data(tb[IOAM6_IPTUNNEL_TRACE]);
 	if (!ioam6_validate_trace_hdr(trace)) {
 		NL_SET_ERR_MSG_ATTR(extack, tb[IOAM6_IPTUNNEL_TRACE],
 				    "invalid trace validation");
 		return -EINVAL;
 	}

 	len_aligned = ALIGN(trace->remlen * 4, 8);
 	lwt = lwtunnel_state_alloc(sizeof(*ilwt) + len_aligned);
 	if (!lwt)
 		return -ENOMEM;

 	ilwt = ioam6_lwt_state(lwt);
 	err = dst_cache_init(&ilwt->cache, GFP_ATOMIC);
 	if (err) {
 		kfree(lwt);
 		return err;
 	}

 	atomic_set(&ilwt->pkt_cnt, 0);
 	ilwt->freq.k = freq_k;
 	ilwt->freq.n = freq_n;

 	ilwt->mode = mode;
 	if (tb[IOAM6_IPTUNNEL_DST])
 		ilwt->tundst = nla_get_in6_addr(tb[IOAM6_IPTUNNEL_DST]);

 	tuninfo = ioam6_lwt_info(lwt);
 	tuninfo->eh.hdrlen = ((sizeof(*tuninfo) + len_aligned) >> 3) - 1;
 	tuninfo->pad[0] = IPV6_TLV_PADN;
 	tuninfo->ioamh.type = IOAM6_TYPE_PREALLOC;
 	tuninfo->ioamh.opt_type = IPV6_TLV_IOAM;
 	tuninfo->ioamh.opt_len = sizeof(tuninfo->ioamh) - 2 + sizeof(*trace)
 					+ trace->remlen * 4;

 	memcpy(&tuninfo->traceh, trace, sizeof(*trace));

 	if (len_aligned - trace->remlen * 4) {
 		tuninfo->traceh.data[trace->remlen * 4] = IPV6_TLV_PADN;
 		tuninfo->traceh.data[trace->remlen * 4 + 1] = 2;
 	}

 	lwt->type = LWTUNNEL_ENCAP_IOAM6;
 	lwt->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;

 	*ts = lwt;

 	return 0;
 }

 static int ioam6_do_fill(struct net *net, struct sk_buff *skb)
 {
 	struct ioam6_trace_hdr *trace;
 	struct ioam6_namespace *ns;

 	trace = (struct ioam6_trace_hdr *)(skb_transport_header(skb)
 					   + sizeof(struct ipv6_hopopt_hdr) + 2
 					   + sizeof(struct ioam6_hdr));

 	ns = ioam6_namespace(net, trace->namespace_id);
 	if (ns)
 		ioam6_fill_trace_data(skb, ns, trace, false);

 	return 0;
 }

 static int ioam6_do_inline(struct net *net, struct sk_buff *skb,
 			   struct ioam6_lwt_encap *tuninfo)
 {
 	struct ipv6hdr *oldhdr, *hdr;
 	int hdrlen, err;

 	hdrlen = (tuninfo->eh.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(*oldhdr));
 	skb_postpull_rcsum(skb, skb_network_header(skb), sizeof(*oldhdr));

 	skb_push(skb, sizeof(*oldhdr) + hdrlen);
 	skb_reset_network_header(skb);
 	skb_mac_header_rebuild(skb);

 	hdr = ipv6_hdr(skb);
 	memmove(hdr, oldhdr, sizeof(*oldhdr));
 	tuninfo->eh.nexthdr = hdr->nexthdr;

 	skb_set_transport_header(skb, sizeof(*hdr));
 	skb_postpush_rcsum(skb, hdr, sizeof(*hdr) + hdrlen);

 	memcpy(skb_transport_header(skb), (u8 *)tuninfo, hdrlen);

 	hdr->nexthdr = NEXTHDR_HOP;
 	hdr->payload_len = cpu_to_be16(skb->len - sizeof(*hdr));

 	return ioam6_do_fill(net, skb);
 }

 static int ioam6_do_encap(struct net *net, struct sk_buff *skb,
 			  struct ioam6_lwt_encap *tuninfo,
 			  struct in6_addr *tundst)
 {
 	struct dst_entry *dst = skb_dst(skb);
 	struct ipv6hdr *hdr, *inner_hdr;
 	int hdrlen, len, err;

 	hdrlen = (tuninfo->eh.hdrlen + 1) << 3;
 	len = sizeof(*hdr) + hdrlen;

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

 	inner_hdr = ipv6_hdr(skb);

 	skb_push(skb, len);
 	skb_reset_network_header(skb);
 	skb_mac_header_rebuild(skb);
 	skb_set_transport_header(skb, sizeof(*hdr));

 	tuninfo->eh.nexthdr = NEXTHDR_IPV6;
 	memcpy(skb_transport_header(skb), (u8 *)tuninfo, hdrlen);

 	hdr = ipv6_hdr(skb);
 	memcpy(hdr, inner_hdr, sizeof(*hdr));

 	hdr->nexthdr = NEXTHDR_HOP;
 	hdr->payload_len = cpu_to_be16(skb->len - sizeof(*hdr));
 	hdr->daddr = *tundst;
 	ipv6_dev_get_saddr(net, dst->dev, &hdr->daddr,
 			   IPV6_PREFER_SRC_PUBLIC, &hdr->saddr);

 	skb_postpush_rcsum(skb, hdr, len);

 	return ioam6_do_fill(net, skb);
 }

 static int ioam6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
 	struct dst_entry *dst = skb_dst(skb);
 	struct in6_addr orig_daddr;
 	struct ioam6_lwt *ilwt;
 	int err = -EINVAL;
 	u32 pkt_cnt;

 	if (skb->protocol != htons(ETH_P_IPV6))
 		goto drop;

 	ilwt = ioam6_lwt_state(dst->lwtstate);

 	/* Check for insertion frequency (i.e., "k over n" insertions) */
 	pkt_cnt = atomic_fetch_inc(&ilwt->pkt_cnt);
 	if (pkt_cnt % ilwt->freq.n >= ilwt->freq.k)
 		goto out;

 	orig_daddr = ipv6_hdr(skb)->daddr;

 	switch (ilwt->mode) {
 	case IOAM6_IPTUNNEL_MODE_INLINE:
 do_inline:
 		/* Direct insertion - if there is no Hop-by-Hop yet */
 		if (ipv6_hdr(skb)->nexthdr == NEXTHDR_HOP)
 			goto out;

 		err = ioam6_do_inline(net, skb, &ilwt->tuninfo);
 		if (unlikely(err))
 			goto drop;

 		break;
 	case IOAM6_IPTUNNEL_MODE_ENCAP:
 do_encap:
 		/* Encapsulation (ip6ip6) */
 		err = ioam6_do_encap(net, skb, &ilwt->tuninfo, &ilwt->tundst);
 		if (unlikely(err))
 			goto drop;

 		break;
 	case IOAM6_IPTUNNEL_MODE_AUTO:
 		/* Automatic (RFC8200 compliant):
 		 *  - local packets -> INLINE mode
 		 *  - in-transit packets -> ENCAP mode
 		 */
 		if (!skb->dev)
 			goto do_inline;

 		goto do_encap;
 	default:
 		goto drop;
 	}

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

 	if (!ipv6_addr_equal(&orig_daddr, &ipv6_hdr(skb)->daddr)) {
 		preempt_disable();
 		dst = dst_cache_get(&ilwt->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(&ilwt->cache, dst, &fl6.saddr);
 			preempt_enable();
 		}

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

 		return dst_output(net, sk, skb);
 	}
 out:
 	return dst->lwtstate->orig_output(net, sk, skb);
 drop:
 	kfree_skb(skb);
 	return err;
 }

 static void ioam6_destroy_state(struct lwtunnel_state *lwt)
 {
 	dst_cache_destroy(&ioam6_lwt_state(lwt)->cache);
 }

 static int ioam6_fill_encap_info(struct sk_buff *skb,
 				 struct lwtunnel_state *lwtstate)
 {
 	struct ioam6_lwt *ilwt = ioam6_lwt_state(lwtstate);
 	int err;

 	err = nla_put_u32(skb, IOAM6_IPTUNNEL_FREQ_K, ilwt->freq.k);
 	if (err)
 		goto ret;

 	err = nla_put_u32(skb, IOAM6_IPTUNNEL_FREQ_N, ilwt->freq.n);
 	if (err)
 		goto ret;

 	err = nla_put_u8(skb, IOAM6_IPTUNNEL_MODE, ilwt->mode);
 	if (err)
 		goto ret;

 	if (ilwt->mode != IOAM6_IPTUNNEL_MODE_INLINE) {
 		err = nla_put_in6_addr(skb, IOAM6_IPTUNNEL_DST, &ilwt->tundst);
 		if (err)
 			goto ret;
 	}

 	err = nla_put(skb, IOAM6_IPTUNNEL_TRACE, sizeof(ilwt->tuninfo.traceh),
 		      &ilwt->tuninfo.traceh);
 ret:
 	return err;
 }

 static int ioam6_encap_nlsize(struct lwtunnel_state *lwtstate)
 {
 	struct ioam6_lwt *ilwt = ioam6_lwt_state(lwtstate);
 	int nlsize;

 	nlsize = nla_total_size(sizeof(ilwt->freq.k)) +
 		  nla_total_size(sizeof(ilwt->freq.n)) +
 		  nla_total_size(sizeof(ilwt->mode)) +
 		  nla_total_size(sizeof(ilwt->tuninfo.traceh));

 	if (ilwt->mode != IOAM6_IPTUNNEL_MODE_INLINE)
 		nlsize += nla_total_size(sizeof(ilwt->tundst));

 	return nlsize;
 }

 static int ioam6_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
 {
 	struct ioam6_trace_hdr *trace_a = ioam6_lwt_trace(a);
 	struct ioam6_trace_hdr *trace_b = ioam6_lwt_trace(b);
 	struct ioam6_lwt *ilwt_a = ioam6_lwt_state(a);
 	struct ioam6_lwt *ilwt_b = ioam6_lwt_state(b);

 	return (ilwt_a->freq.k != ilwt_b->freq.k ||
 		ilwt_a->freq.n != ilwt_b->freq.n ||
 		ilwt_a->mode != ilwt_b->mode ||
 		(ilwt_a->mode != IOAM6_IPTUNNEL_MODE_INLINE &&
 		 !ipv6_addr_equal(&ilwt_a->tundst, &ilwt_b->tundst)) ||
 		trace_a->namespace_id != trace_b->namespace_id);
 }

 static const struct lwtunnel_encap_ops ioam6_iptun_ops = {
 	.build_state		= ioam6_build_state,
 	.destroy_state		= ioam6_destroy_state,
 	.output		= ioam6_output,
 	.fill_encap		= ioam6_fill_encap_info,
 	.get_encap_size	= ioam6_encap_nlsize,
 	.cmp_encap		= ioam6_encap_cmp,
 	.owner			= THIS_MODULE,
 };

 int __init ioam6_iptunnel_init(void)
 {
 	return lwtunnel_encap_add_ops(&ioam6_iptun_ops, LWTUNNEL_ENCAP_IOAM6);
 }

 void ioam6_iptunnel_exit(void)
 {
 	lwtunnel_encap_del_ops(&ioam6_iptun_ops, LWTUNNEL_ENCAP_IOAM6);
 }
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* IPv6 IOAM Lightweight Tunnel implementation
	*
	* Author:
	* Justin Iurman <justin.iurman@uliege.be>
	*/

	#include <linux/kernel.h>
	#include <linux/skbuff.h>
	#include <linux/net.h>
	#include <linux/in6.h>
	#include <linux/ioam6.h>
	#include <linux/ioam6_iptunnel.h>
	#include <net/dst.h>
	#include <net/sock.h>
	#include <net/lwtunnel.h>
	#include <net/ioam6.h>
	#include <net/netlink.h>
	#include <net/ipv6.h>
	#include <net/dst_cache.h>
	#include <net/ip6_route.h>
	#include <net/addrconf.h>

	#define IOAM6_MASK_SHORT_FIELDS 0xff100000
	#define IOAM6_MASK_WIDE_FIELDS 0xe00000

	struct ioam6_lwt_encap {
	struct ipv6_hopopt_hdr eh;
	u8 pad[2]; /* 2-octet padding for 4n-alignment */
	struct ioam6_hdr ioamh;
	struct ioam6_trace_hdr traceh;
	} __packed;

	struct ioam6_lwt_freq {
	u32 k;
	u32 n;
	};

	struct ioam6_lwt {
	struct dst_cache cache;
	struct ioam6_lwt_freq freq;
	atomic_t pkt_cnt;
	u8 mode;
	struct in6_addr tundst;
	struct ioam6_lwt_encap tuninfo;
	};

	static const struct netlink_range_validation freq_range = {
	.min = IOAM6_IPTUNNEL_FREQ_MIN,
	.max = IOAM6_IPTUNNEL_FREQ_MAX,
	};

	static struct ioam6_lwt ioam6_lwt_state(struct lwtunnel_state lwt)
	{
	return (struct ioam6_lwt *)lwt->data;
	}

	static struct ioam6_lwt_encap ioam6_lwt_info(struct lwtunnel_state lwt)
	{
	return &ioam6_lwt_state(lwt)->tuninfo;
	}

	static struct ioam6_trace_hdr ioam6_lwt_trace(struct lwtunnel_state lwt)
	{
	return &(ioam6_lwt_state(lwt)->tuninfo.traceh);
	}

	static const struct nla_policy ioam6_iptunnel_policy[IOAM6_IPTUNNEL_MAX + 1] = {
	[IOAM6_IPTUNNEL_FREQ_K] = NLA_POLICY_FULL_RANGE(NLA_U32, &freq_range),
	[IOAM6_IPTUNNEL_FREQ_N] = NLA_POLICY_FULL_RANGE(NLA_U32, &freq_range),
	[IOAM6_IPTUNNEL_MODE] = NLA_POLICY_RANGE(NLA_U8,
	IOAM6_IPTUNNEL_MODE_MIN,
	IOAM6_IPTUNNEL_MODE_MAX),
	[IOAM6_IPTUNNEL_DST] = NLA_POLICY_EXACT_LEN(sizeof(struct in6_addr)),
	[IOAM6_IPTUNNEL_TRACE] = NLA_POLICY_EXACT_LEN(sizeof(struct ioam6_trace_hdr)),
	};

	static bool ioam6_validate_trace_hdr(struct ioam6_trace_hdr *trace)
	{
	u32 fields;

	if (!trace->type_be32 \|\| !trace->remlen \|\|
	trace->remlen > IOAM6_TRACE_DATA_SIZE_MAX / 4 \|\|
	trace->type.bit12 \| trace->type.bit13 \| trace->type.bit14 \|
	trace->type.bit15 \| trace->type.bit16 \| trace->type.bit17 \|
	trace->type.bit18 \| trace->type.bit19 \| trace->type.bit20 \|
	trace->type.bit21)
	return false;

	trace->nodelen = 0;
	fields = be32_to_cpu(trace->type_be32);

	trace->nodelen += hweight32(fields & IOAM6_MASK_SHORT_FIELDS)
	* (sizeof(__be32) / 4);
	trace->nodelen += hweight32(fields & IOAM6_MASK_WIDE_FIELDS)
	* (sizeof(__be64) / 4);

	return true;
	}

	static int ioam6_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[IOAM6_IPTUNNEL_MAX + 1];
	struct ioam6_lwt_encap *tuninfo;
	struct ioam6_trace_hdr *trace;
	struct lwtunnel_state *lwt;
	struct ioam6_lwt *ilwt;
	int len_aligned, err;
	u32 freq_k, freq_n;
	u8 mode;

	if (family != AF_INET6)
	return -EINVAL;

	err = nla_parse_nested(tb, IOAM6_IPTUNNEL_MAX, nla,
	ioam6_iptunnel_policy, extack);
	if (err < 0)
	return err;

	if ((!tb[IOAM6_IPTUNNEL_FREQ_K] && tb[IOAM6_IPTUNNEL_FREQ_N]) \|\|
	(tb[IOAM6_IPTUNNEL_FREQ_K] && !tb[IOAM6_IPTUNNEL_FREQ_N])) {
	NL_SET_ERR_MSG(extack, "freq: missing parameter");
	return -EINVAL;
	} else if (!tb[IOAM6_IPTUNNEL_FREQ_K] && !tb[IOAM6_IPTUNNEL_FREQ_N]) {
	freq_k = IOAM6_IPTUNNEL_FREQ_MIN;
	freq_n = IOAM6_IPTUNNEL_FREQ_MIN;
	} else {
	freq_k = nla_get_u32(tb[IOAM6_IPTUNNEL_FREQ_K]);
	freq_n = nla_get_u32(tb[IOAM6_IPTUNNEL_FREQ_N]);

	if (freq_k > freq_n) {
	NL_SET_ERR_MSG(extack, "freq: k > n is forbidden");
	return -EINVAL;
	}
	}

	if (!tb[IOAM6_IPTUNNEL_MODE])
	mode = IOAM6_IPTUNNEL_MODE_INLINE;
	else
	mode = nla_get_u8(tb[IOAM6_IPTUNNEL_MODE]);

	if (!tb[IOAM6_IPTUNNEL_DST] && mode != IOAM6_IPTUNNEL_MODE_INLINE) {
	NL_SET_ERR_MSG(extack, "this mode needs a tunnel destination");
	return -EINVAL;
	}

	if (!tb[IOAM6_IPTUNNEL_TRACE]) {
	NL_SET_ERR_MSG(extack, "missing trace");
	return -EINVAL;
	}

	trace = nla_data(tb[IOAM6_IPTUNNEL_TRACE]);
	if (!ioam6_validate_trace_hdr(trace)) {
	NL_SET_ERR_MSG_ATTR(extack, tb[IOAM6_IPTUNNEL_TRACE],
	"invalid trace validation");
	return -EINVAL;
	}

	len_aligned = ALIGN(trace->remlen * 4, 8);
	lwt = lwtunnel_state_alloc(sizeof(*ilwt) + len_aligned);
	if (!lwt)
	return -ENOMEM;

	ilwt = ioam6_lwt_state(lwt);
	err = dst_cache_init(&ilwt->cache, GFP_ATOMIC);
	if (err) {
	kfree(lwt);
	return err;
	}

	atomic_set(&ilwt->pkt_cnt, 0);
	ilwt->freq.k = freq_k;
	ilwt->freq.n = freq_n;

	ilwt->mode = mode;
	if (tb[IOAM6_IPTUNNEL_DST])
	ilwt->tundst = nla_get_in6_addr(tb[IOAM6_IPTUNNEL_DST]);

	tuninfo = ioam6_lwt_info(lwt);
	tuninfo->eh.hdrlen = ((sizeof(*tuninfo) + len_aligned) >> 3) - 1;
	tuninfo->pad[0] = IPV6_TLV_PADN;
	tuninfo->ioamh.type = IOAM6_TYPE_PREALLOC;
	tuninfo->ioamh.opt_type = IPV6_TLV_IOAM;
	tuninfo->ioamh.opt_len = sizeof(tuninfo->ioamh) - 2 + sizeof(*trace)
	+ trace->remlen * 4;

	memcpy(&tuninfo->traceh, trace, sizeof(*trace));

	if (len_aligned - trace->remlen * 4) {
	tuninfo->traceh.data[trace->remlen * 4] = IPV6_TLV_PADN;
	tuninfo->traceh.data[trace->remlen * 4 + 1] = 2;
	}

	lwt->type = LWTUNNEL_ENCAP_IOAM6;
	lwt->flags \|= LWTUNNEL_STATE_OUTPUT_REDIRECT;

	*ts = lwt;

	return 0;
	}

	static int ioam6_do_fill(struct net net, struct sk_buff skb)
	{
	struct ioam6_trace_hdr *trace;
	struct ioam6_namespace *ns;

	trace = (struct ioam6_trace_hdr *)(skb_transport_header(skb)
	+ sizeof(struct ipv6_hopopt_hdr) + 2
	+ sizeof(struct ioam6_hdr));

	ns = ioam6_namespace(net, trace->namespace_id);
	if (ns)
	ioam6_fill_trace_data(skb, ns, trace, false);

	return 0;
	}

	static int ioam6_do_inline(struct net net, struct sk_buff skb,
	struct ioam6_lwt_encap *tuninfo)
	{
	struct ipv6hdr oldhdr, hdr;
	int hdrlen, err;

	hdrlen = (tuninfo->eh.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(*oldhdr));
	skb_postpull_rcsum(skb, skb_network_header(skb), sizeof(*oldhdr));

	skb_push(skb, sizeof(*oldhdr) + hdrlen);
	skb_reset_network_header(skb);
	skb_mac_header_rebuild(skb);

	hdr = ipv6_hdr(skb);
	memmove(hdr, oldhdr, sizeof(*oldhdr));
	tuninfo->eh.nexthdr = hdr->nexthdr;

	skb_set_transport_header(skb, sizeof(*hdr));
	skb_postpush_rcsum(skb, hdr, sizeof(*hdr) + hdrlen);

	memcpy(skb_transport_header(skb), (u8 *)tuninfo, hdrlen);

	hdr->nexthdr = NEXTHDR_HOP;
	hdr->payload_len = cpu_to_be16(skb->len - sizeof(*hdr));

	return ioam6_do_fill(net, skb);
	}

	static int ioam6_do_encap(struct net net, struct sk_buff skb,
	struct ioam6_lwt_encap *tuninfo,
	struct in6_addr *tundst)
	{
	struct dst_entry *dst = skb_dst(skb);
	struct ipv6hdr hdr, inner_hdr;
	int hdrlen, len, err;

	hdrlen = (tuninfo->eh.hdrlen + 1) << 3;
	len = sizeof(*hdr) + hdrlen;

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

	inner_hdr = ipv6_hdr(skb);

	skb_push(skb, len);
	skb_reset_network_header(skb);
	skb_mac_header_rebuild(skb);
	skb_set_transport_header(skb, sizeof(*hdr));

	tuninfo->eh.nexthdr = NEXTHDR_IPV6;
	memcpy(skb_transport_header(skb), (u8 *)tuninfo, hdrlen);

	hdr = ipv6_hdr(skb);
	memcpy(hdr, inner_hdr, sizeof(*hdr));

	hdr->nexthdr = NEXTHDR_HOP;
	hdr->payload_len = cpu_to_be16(skb->len - sizeof(*hdr));
	hdr->daddr = *tundst;
	ipv6_dev_get_saddr(net, dst->dev, &hdr->daddr,
	IPV6_PREFER_SRC_PUBLIC, &hdr->saddr);

	skb_postpush_rcsum(skb, hdr, len);

	return ioam6_do_fill(net, skb);
	}

	static int ioam6_output(struct net net, struct sock sk, struct sk_buff *skb)
	{
	struct dst_entry *dst = skb_dst(skb);
	struct in6_addr orig_daddr;
	struct ioam6_lwt *ilwt;
	int err = -EINVAL;
	u32 pkt_cnt;

	if (skb->protocol != htons(ETH_P_IPV6))
	goto drop;

	ilwt = ioam6_lwt_state(dst->lwtstate);

	/* Check for insertion frequency (i.e., "k over n" insertions) */
	pkt_cnt = atomic_fetch_inc(&ilwt->pkt_cnt);
	if (pkt_cnt % ilwt->freq.n >= ilwt->freq.k)
	goto out;

	orig_daddr = ipv6_hdr(skb)->daddr;

	switch (ilwt->mode) {
	case IOAM6_IPTUNNEL_MODE_INLINE:
	do_inline:
	/* Direct insertion - if there is no Hop-by-Hop yet */
	if (ipv6_hdr(skb)->nexthdr == NEXTHDR_HOP)
	goto out;

	err = ioam6_do_inline(net, skb, &ilwt->tuninfo);
	if (unlikely(err))
	goto drop;

	break;
	case IOAM6_IPTUNNEL_MODE_ENCAP:
	do_encap:
	/* Encapsulation (ip6ip6) */
	err = ioam6_do_encap(net, skb, &ilwt->tuninfo, &ilwt->tundst);
	if (unlikely(err))
	goto drop;

	break;
	case IOAM6_IPTUNNEL_MODE_AUTO:
	/* Automatic (RFC8200 compliant):
	* - local packets -> INLINE mode
	* - in-transit packets -> ENCAP mode
	*/
	if (!skb->dev)
	goto do_inline;

	goto do_encap;
	default:
	goto drop;
	}

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

	if (!ipv6_addr_equal(&orig_daddr, &ipv6_hdr(skb)->daddr)) {
	preempt_disable();
	dst = dst_cache_get(&ilwt->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(&ilwt->cache, dst, &fl6.saddr);
	preempt_enable();
	}

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

	return dst_output(net, sk, skb);
	}
	out:
	return dst->lwtstate->orig_output(net, sk, skb);
	drop:
	kfree_skb(skb);
	return err;
	}

	static void ioam6_destroy_state(struct lwtunnel_state *lwt)
	{
	dst_cache_destroy(&ioam6_lwt_state(lwt)->cache);
	}

	static int ioam6_fill_encap_info(struct sk_buff *skb,
	struct lwtunnel_state *lwtstate)
	{
	struct ioam6_lwt *ilwt = ioam6_lwt_state(lwtstate);
	int err;

	err = nla_put_u32(skb, IOAM6_IPTUNNEL_FREQ_K, ilwt->freq.k);
	if (err)
	goto ret;

	err = nla_put_u32(skb, IOAM6_IPTUNNEL_FREQ_N, ilwt->freq.n);
	if (err)
	goto ret;

	err = nla_put_u8(skb, IOAM6_IPTUNNEL_MODE, ilwt->mode);
	if (err)
	goto ret;

	if (ilwt->mode != IOAM6_IPTUNNEL_MODE_INLINE) {
	err = nla_put_in6_addr(skb, IOAM6_IPTUNNEL_DST, &ilwt->tundst);
	if (err)
	goto ret;
	}

	err = nla_put(skb, IOAM6_IPTUNNEL_TRACE, sizeof(ilwt->tuninfo.traceh),
	&ilwt->tuninfo.traceh);
	ret:
	return err;
	}

	static int ioam6_encap_nlsize(struct lwtunnel_state *lwtstate)
	{
	struct ioam6_lwt *ilwt = ioam6_lwt_state(lwtstate);
	int nlsize;

	nlsize = nla_total_size(sizeof(ilwt->freq.k)) +
	nla_total_size(sizeof(ilwt->freq.n)) +
	nla_total_size(sizeof(ilwt->mode)) +
	nla_total_size(sizeof(ilwt->tuninfo.traceh));

	if (ilwt->mode != IOAM6_IPTUNNEL_MODE_INLINE)
	nlsize += nla_total_size(sizeof(ilwt->tundst));

	return nlsize;
	}

	static int ioam6_encap_cmp(struct lwtunnel_state a, struct lwtunnel_state b)
	{
	struct ioam6_trace_hdr *trace_a = ioam6_lwt_trace(a);
	struct ioam6_trace_hdr *trace_b = ioam6_lwt_trace(b);
	struct ioam6_lwt *ilwt_a = ioam6_lwt_state(a);
	struct ioam6_lwt *ilwt_b = ioam6_lwt_state(b);

	return (ilwt_a->freq.k != ilwt_b->freq.k \|\|
	ilwt_a->freq.n != ilwt_b->freq.n \|\|
	ilwt_a->mode != ilwt_b->mode \|\|
	(ilwt_a->mode != IOAM6_IPTUNNEL_MODE_INLINE &&
	!ipv6_addr_equal(&ilwt_a->tundst, &ilwt_b->tundst)) \|\|
	trace_a->namespace_id != trace_b->namespace_id);
	}

	static const struct lwtunnel_encap_ops ioam6_iptun_ops = {
	.build_state = ioam6_build_state,
	.destroy_state = ioam6_destroy_state,
	.output = ioam6_output,
	.fill_encap = ioam6_fill_encap_info,
	.get_encap_size = ioam6_encap_nlsize,
	.cmp_encap = ioam6_encap_cmp,
	.owner = THIS_MODULE,
	};

	int __init ioam6_iptunnel_init(void)
	{
	return lwtunnel_encap_add_ops(&ioam6_iptun_ops, LWTUNNEL_ENCAP_IOAM6);
	}

	void ioam6_iptunnel_exit(void)
	{
	lwtunnel_encap_del_ops(&ioam6_iptun_ops, LWTUNNEL_ENCAP_IOAM6);
	}