/*
 *  SR-IPv6 implementation
 *
 *  Author:
 *  David Lebrun <david.lebrun@uclouvain.be>
 *
 *
 *  This program is free software; you can redistribute it and/or
 *        modify it under the terms of the GNU General Public License
 *        as published by the Free Software Foundation; either version
 *        2 of the License, or (at your option) any later version.
 */

#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/net.h>
#include <linux/module.h>
#include <net/ip.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_local.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

struct seg6_local_lwt;

struct seg6_action_desc {
	int action;
	unsigned long attrs;
	int (*input)(struct sk_buff *skb, struct seg6_local_lwt *slwt);
	int static_headroom;
};

struct seg6_local_lwt {
	int action;
	struct ipv6_sr_hdr *srh;
	int table;
	struct in_addr nh4;
	struct in6_addr nh6;
	int iif;
	int oif;

	int headroom;
	struct seg6_action_desc *desc;
};

static struct seg6_local_lwt *seg6_local_lwtunnel(struct lwtunnel_state *lwt)
{
	return (struct seg6_local_lwt *)lwt->data;
}

static struct seg6_action_desc seg6_action_table[] = {
	{
		.action		= SEG6_LOCAL_ACTION_END,
		.attrs		= 0,
	},
};

static struct seg6_action_desc *__get_action_desc(int action)
{
	struct seg6_action_desc *desc;
	int i, count;

	count = sizeof(seg6_action_table) / sizeof(struct seg6_action_desc);
	for (i = 0; i < count; i++) {
		desc = &seg6_action_table[i];
		if (desc->action == action)
			return desc;
	}

	return NULL;
}

static int seg6_local_input(struct sk_buff *skb)
{
	struct dst_entry *orig_dst = skb_dst(skb);
	struct seg6_action_desc *desc;
	struct seg6_local_lwt *slwt;

	slwt = seg6_local_lwtunnel(orig_dst->lwtstate);
	desc = slwt->desc;

	return desc->input(skb, slwt);
}

static const struct nla_policy seg6_local_policy[SEG6_LOCAL_MAX + 1] = {
	[SEG6_LOCAL_ACTION]	= { .type = NLA_U32 },
	[SEG6_LOCAL_SRH]	= { .type = NLA_BINARY },
	[SEG6_LOCAL_TABLE]	= { .type = NLA_U32 },
	[SEG6_LOCAL_NH4]	= { .type = NLA_BINARY,
				    .len = sizeof(struct in_addr) },
	[SEG6_LOCAL_NH6]	= { .type = NLA_BINARY,
				    .len = sizeof(struct in6_addr) },
	[SEG6_LOCAL_IIF]	= { .type = NLA_U32 },
	[SEG6_LOCAL_OIF]	= { .type = NLA_U32 },
};

struct seg6_action_param {
	int (*parse)(struct nlattr **attrs, struct seg6_local_lwt *slwt);
	int (*put)(struct sk_buff *skb, struct seg6_local_lwt *slwt);
	int (*cmp)(struct seg6_local_lwt *a, struct seg6_local_lwt *b);
};

static struct seg6_action_param seg6_action_params[SEG6_LOCAL_MAX + 1] = {
	[SEG6_LOCAL_SRH]	= { .parse = NULL,
				    .put = NULL,
				    .cmp = NULL },

	[SEG6_LOCAL_TABLE]	= { .parse = NULL,
				    .put = NULL,
				    .cmp = NULL },

	[SEG6_LOCAL_NH4]	= { .parse = NULL,
				    .put = NULL,
				    .cmp = NULL },

	[SEG6_LOCAL_NH6]	= { .parse = NULL,
				    .put = NULL,
				    .cmp = NULL },

	[SEG6_LOCAL_IIF]	= { .parse = NULL,
				    .put = NULL,
				    .cmp = NULL },

	[SEG6_LOCAL_OIF]	= { .parse = NULL,
				    .put = NULL,
				    .cmp = NULL },
};

static int parse_nla_action(struct nlattr **attrs, struct seg6_local_lwt *slwt)
{
	struct seg6_action_param *param;
	struct seg6_action_desc *desc;
	int i, err;

	desc = __get_action_desc(slwt->action);
	if (!desc)
		return -EINVAL;

	if (!desc->input)
		return -EOPNOTSUPP;

	slwt->desc = desc;
	slwt->headroom += desc->static_headroom;

	for (i = 0; i < SEG6_LOCAL_MAX + 1; i++) {
		if (desc->attrs & (1 << i)) {
			if (!attrs[i])
				return -EINVAL;

			param = &seg6_action_params[i];

			err = param->parse(attrs, slwt);
			if (err < 0)
				return err;
		}
	}

	return 0;
}

static int seg6_local_build_state(struct nlattr *nla, unsigned int family,
				  const void *cfg, struct lwtunnel_state **ts,
				  struct netlink_ext_ack *extack)
{
	struct nlattr *tb[SEG6_LOCAL_MAX + 1];
	struct lwtunnel_state *newts;
	struct seg6_local_lwt *slwt;
	int err;

	err = nla_parse_nested(tb, SEG6_LOCAL_MAX, nla, seg6_local_policy,
			       extack);

	if (err < 0)
		return err;

	if (!tb[SEG6_LOCAL_ACTION])
		return -EINVAL;

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

	slwt = seg6_local_lwtunnel(newts);
	slwt->action = nla_get_u32(tb[SEG6_LOCAL_ACTION]);

	err = parse_nla_action(tb, slwt);
	if (err < 0)
		goto out_free;

	newts->type = LWTUNNEL_ENCAP_SEG6_LOCAL;
	newts->flags = LWTUNNEL_STATE_INPUT_REDIRECT;
	newts->headroom = slwt->headroom;

	*ts = newts;

	return 0;

out_free:
	kfree(slwt->srh);
	kfree(newts);
	return err;
}

static void seg6_local_destroy_state(struct lwtunnel_state *lwt)
{
	struct seg6_local_lwt *slwt = seg6_local_lwtunnel(lwt);

	kfree(slwt->srh);
}

static int seg6_local_fill_encap(struct sk_buff *skb,
				 struct lwtunnel_state *lwt)
{
	struct seg6_local_lwt *slwt = seg6_local_lwtunnel(lwt);
	struct seg6_action_param *param;
	int i, err;

	if (nla_put_u32(skb, SEG6_LOCAL_ACTION, slwt->action))
		return -EMSGSIZE;

	for (i = 0; i < SEG6_LOCAL_MAX + 1; i++) {
		if (slwt->desc->attrs & (1 << i)) {
			param = &seg6_action_params[i];
			err = param->put(skb, slwt);
			if (err < 0)
				return err;
		}
	}

	return 0;
}

static int seg6_local_get_encap_size(struct lwtunnel_state *lwt)
{
	struct seg6_local_lwt *slwt = seg6_local_lwtunnel(lwt);
	unsigned long attrs;
	int nlsize;

	nlsize = nla_total_size(4); /* action */

	attrs = slwt->desc->attrs;

	if (attrs & (1 << SEG6_LOCAL_SRH))
		nlsize += nla_total_size((slwt->srh->hdrlen + 1) << 3);

	if (attrs & (1 << SEG6_LOCAL_TABLE))
		nlsize += nla_total_size(4);

	if (attrs & (1 << SEG6_LOCAL_NH4))
		nlsize += nla_total_size(4);

	if (attrs & (1 << SEG6_LOCAL_NH6))
		nlsize += nla_total_size(16);

	if (attrs & (1 << SEG6_LOCAL_IIF))
		nlsize += nla_total_size(4);

	if (attrs & (1 << SEG6_LOCAL_OIF))
		nlsize += nla_total_size(4);

	return nlsize;
}

static int seg6_local_cmp_encap(struct lwtunnel_state *a,
				struct lwtunnel_state *b)
{
	struct seg6_local_lwt *slwt_a, *slwt_b;
	struct seg6_action_param *param;
	int i;

	slwt_a = seg6_local_lwtunnel(a);
	slwt_b = seg6_local_lwtunnel(b);

	if (slwt_a->action != slwt_b->action)
		return 1;

	if (slwt_a->desc->attrs != slwt_b->desc->attrs)
		return 1;

	for (i = 0; i < SEG6_LOCAL_MAX + 1; i++) {
		if (slwt_a->desc->attrs & (1 << i)) {
			param = &seg6_action_params[i];
			if (param->cmp(slwt_a, slwt_b))
				return 1;
		}
	}

	return 0;
}

static const struct lwtunnel_encap_ops seg6_local_ops = {
	.build_state	= seg6_local_build_state,
	.destroy_state	= seg6_local_destroy_state,
	.input		= seg6_local_input,
	.fill_encap	= seg6_local_fill_encap,
	.get_encap_size	= seg6_local_get_encap_size,
	.cmp_encap	= seg6_local_cmp_encap,
	.owner		= THIS_MODULE,
};

int __init seg6_local_init(void)
{
	return lwtunnel_encap_add_ops(&seg6_local_ops,
				      LWTUNNEL_ENCAP_SEG6_LOCAL);
}

void seg6_local_exit(void)
{
	lwtunnel_encap_del_ops(&seg6_local_ops, LWTUNNEL_ENCAP_SEG6_LOCAL);
}