#include <linux/errno.h>
#include <linux/ip.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/socket.h>
#include <linux/types.h>
#include <net/checksum.h>
#include <net/dst_cache.h>
#include <net/ip.h>
#include <net/ip6_fib.h>
#include <net/ip6_route.h>
#include <net/lwtunnel.h>
#include <net/protocol.h>
#include <uapi/linux/ila.h>
#include "ila.h"

struct ila_lwt {
        struct ila_params p;
        struct dst_cache dst_cache;
        u32 connected : 1;
};

static inline struct ila_lwt *ila_lwt_lwtunnel(
        struct lwtunnel_state *lwt)
{
        return (struct ila_lwt *)lwt->data;
}

static inline struct ila_params *ila_params_lwtunnel(
        struct lwtunnel_state *lwt)
{
        return &ila_lwt_lwtunnel(lwt)->p;
}

static int ila_output(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        struct dst_entry *orig_dst = skb_dst(skb);
        struct rt6_info *rt = (struct rt6_info *)orig_dst;
        struct ila_lwt *ilwt = ila_lwt_lwtunnel(orig_dst->lwtstate);
        struct dst_entry *dst;
        int err = -EINVAL;

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

        ila_update_ipv6_locator(skb, ila_params_lwtunnel(orig_dst->lwtstate),
                                true);

        if (rt->rt6i_flags & (RTF_GATEWAY | RTF_CACHE)) {
                /* Already have a next hop address in route, no need for
                 * dest cache route.
                 */
                return orig_dst->lwtstate->orig_output(net, sk, skb);
        }

        dst = dst_cache_get(&ilwt->dst_cache);
        if (unlikely(!dst)) {
                struct ipv6hdr *ip6h = ipv6_hdr(skb);
                struct flowi6 fl6;

                /* Lookup a route for the new destination. Take into
                 * account that the base route may already have a gateway.
                 */

                memset(&fl6, 0, sizeof(fl6));
                fl6.flowi6_oif = orig_dst->dev->ifindex;
                fl6.flowi6_iif = LOOPBACK_IFINDEX;
                fl6.daddr = *rt6_nexthop((struct rt6_info *)orig_dst,
                                         &ip6h->daddr);

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

                dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0);
                if (IS_ERR(dst)) {
                        err = PTR_ERR(dst);
                        goto drop;
                }

                if (ilwt->connected)
                        dst_cache_set_ip6(&ilwt->dst_cache, dst, &fl6.saddr);
        }

        skb_dst_set(skb, dst);
        return dst_output(net, sk, skb);

drop:
        kfree_skb(skb);
        return -EINVAL;
}

static int ila_input(struct sk_buff *skb)
{
        struct dst_entry *dst = skb_dst(skb);

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

        ila_update_ipv6_locator(skb, ila_params_lwtunnel(dst->lwtstate), false);

        return dst->lwtstate->orig_input(skb);

drop:
        kfree_skb(skb);
        return -EINVAL;
}

static const struct nla_policy ila_nl_policy[ILA_ATTR_MAX + 1] = {
        [ILA_ATTR_LOCATOR] = { .type = NLA_U64, },
        [ILA_ATTR_CSUM_MODE] = { .type = NLA_U8, },
};

static int ila_build_state(struct nlattr *nla,
                           unsigned int family, const void *cfg,
                           struct lwtunnel_state **ts)
{
        struct ila_lwt *ilwt;
        struct ila_params *p;
        struct nlattr *tb[ILA_ATTR_MAX + 1];
        struct lwtunnel_state *newts;
        const struct fib6_config *cfg6 = cfg;
        struct ila_addr *iaddr;
        int ret;

        if (family != AF_INET6)
                return -EINVAL;

        if (cfg6->fc_dst_len < 8 * sizeof(struct ila_locator) + 3) {
                /* Need to have full locator and at least type field
                 * included in destination
                 */
                return -EINVAL;
        }

        iaddr = (struct ila_addr *)&cfg6->fc_dst;

        if (!ila_addr_is_ila(iaddr) || ila_csum_neutral_set(iaddr->ident)) {
                /* Don't allow translation for a non-ILA address or checksum
                 * neutral flag to be set.
                 */
                return -EINVAL;
        }

        ret = nla_parse_nested(tb, ILA_ATTR_MAX, nla, ila_nl_policy, NULL);
        if (ret < 0)
                return ret;

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

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

        ilwt = ila_lwt_lwtunnel(newts);
        ret = dst_cache_init(&ilwt->dst_cache, GFP_ATOMIC);
        if (ret) {
                kfree(newts);
                return ret;
        }

        p = ila_params_lwtunnel(newts);

        p->locator.v64 = (__force __be64)nla_get_u64(tb[ILA_ATTR_LOCATOR]);

        /* Precompute checksum difference for translation since we
         * know both the old locator and the new one.
         */
        p->locator_match = iaddr->loc;
        p->csum_diff = compute_csum_diff8(
                (__be32 *)&p->locator_match, (__be32 *)&p->locator);

        if (tb[ILA_ATTR_CSUM_MODE])
                p->csum_mode = nla_get_u8(tb[ILA_ATTR_CSUM_MODE]);

        ila_init_saved_csum(p);

        newts->type = LWTUNNEL_ENCAP_ILA;
        newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT |
                        LWTUNNEL_STATE_INPUT_REDIRECT;

        if (cfg6->fc_dst_len == 8 * sizeof(struct in6_addr))
                ilwt->connected = 1;

        *ts = newts;

        return 0;
}

static void ila_destroy_state(struct lwtunnel_state *lwt)
{
        dst_cache_destroy(&ila_lwt_lwtunnel(lwt)->dst_cache);
}

static int ila_fill_encap_info(struct sk_buff *skb,
                               struct lwtunnel_state *lwtstate)
{
        struct ila_params *p = ila_params_lwtunnel(lwtstate);

        if (nla_put_u64_64bit(skb, ILA_ATTR_LOCATOR, (__force u64)p->locator.v64,
                              ILA_ATTR_PAD))
                goto nla_put_failure;
        if (nla_put_u8(skb, ILA_ATTR_CSUM_MODE, (__force u8)p->csum_mode))
                goto nla_put_failure;

        return 0;

nla_put_failure:
        return -EMSGSIZE;
}

static int ila_encap_nlsize(struct lwtunnel_state *lwtstate)
{
        return nla_total_size_64bit(sizeof(u64)) + /* ILA_ATTR_LOCATOR */
               nla_total_size(sizeof(u8)) +        /* ILA_ATTR_CSUM_MODE */
               0;
}

static int ila_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
{
        struct ila_params *a_p = ila_params_lwtunnel(a);
        struct ila_params *b_p = ila_params_lwtunnel(b);

        return (a_p->locator.v64 != b_p->locator.v64);
}

static const struct lwtunnel_encap_ops ila_encap_ops = {
        .build_state = ila_build_state,
        .destroy_state = ila_destroy_state,
        .output = ila_output,
        .input = ila_input,
        .fill_encap = ila_fill_encap_info,
        .get_encap_size = ila_encap_nlsize,
        .cmp_encap = ila_encap_cmp,
        .owner = THIS_MODULE,
};

int ila_lwt_init(void)
{
        return lwtunnel_encap_add_ops(&ila_encap_ops, LWTUNNEL_ENCAP_ILA);
}

void ila_lwt_fini(void)
{
        lwtunnel_encap_del_ops(&ila_encap_ops, LWTUNNEL_ENCAP_ILA);
}