// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C)2003,2004 USAGI/WIDE Project
 *
 * Author:
 *      Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
 */

#include <linux/types.h>
#include <linux/timer.h>
#include <linux/module.h>
#include <linux/netfilter.h>
#include <linux/in6.h>
#include <linux/icmpv6.h>
#include <linux/ipv6.h>
#include <net/ipv6.h>
#include <net/ip6_checksum.h>
#include <linux/seq_file.h>
#include <linux/netfilter_ipv6.h>
#include <net/netfilter/nf_conntrack_tuple.h>
#include <net/netfilter/nf_conntrack_l4proto.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack_timeout.h>
#include <net/netfilter/nf_conntrack_zones.h>
#include <net/netfilter/nf_log.h>

#include "nf_internals.h"

static const unsigned int nf_ct_icmpv6_timeout = 30*HZ;

bool icmpv6_pkt_to_tuple(const struct sk_buff *skb,
                         unsigned int dataoff,
                         struct net *net,
                         struct nf_conntrack_tuple *tuple)
{
        const struct icmp6hdr *hp;
        struct icmp6hdr _hdr;

        hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
        if (hp == NULL)
                return false;
        tuple->dst.u.icmp.type = hp->icmp6_type;
        tuple->src.u.icmp.id = hp->icmp6_identifier;
        tuple->dst.u.icmp.code = hp->icmp6_code;

        return true;
}

/* Add 1; spaces filled with 0. */
static const u_int8_t invmap[] = {
        [ICMPV6_ECHO_REQUEST - 128]     = ICMPV6_ECHO_REPLY + 1,
        [ICMPV6_ECHO_REPLY - 128]       = ICMPV6_ECHO_REQUEST + 1,
        [ICMPV6_NI_QUERY - 128]         = ICMPV6_NI_REPLY + 1,
        [ICMPV6_NI_REPLY - 128]         = ICMPV6_NI_QUERY + 1
};

static const u_int8_t noct_valid_new[] = {
        [ICMPV6_MGM_QUERY - 130] = 1,
        [ICMPV6_MGM_REPORT - 130] = 1,
        [ICMPV6_MGM_REDUCTION - 130] = 1,
        [NDISC_ROUTER_SOLICITATION - 130] = 1,
        [NDISC_ROUTER_ADVERTISEMENT - 130] = 1,
        [NDISC_NEIGHBOUR_SOLICITATION - 130] = 1,
        [NDISC_NEIGHBOUR_ADVERTISEMENT - 130] = 1,
        [ICMPV6_MLD2_REPORT - 130] = 1,
        [ICMPV6_MRDISC_ADV - 130] = 1,
        [ICMPV6_MRDISC_SOL - 130] = 1
};

bool nf_conntrack_invert_icmpv6_tuple(struct nf_conntrack_tuple *tuple,
                                      const struct nf_conntrack_tuple *orig)
{
        int type = orig->dst.u.icmp.type - 128;
        if (type < 0 || type >= sizeof(invmap) || !invmap[type])
                return false;

        tuple->src.u.icmp.id   = orig->src.u.icmp.id;
        tuple->dst.u.icmp.type = invmap[type] - 1;
        tuple->dst.u.icmp.code = orig->dst.u.icmp.code;
        return true;
}

static unsigned int *icmpv6_get_timeouts(struct net *net)
{
        return &nf_icmpv6_pernet(net)->timeout;
}

/* Returns verdict for packet, or -1 for invalid. */
int nf_conntrack_icmpv6_packet(struct nf_conn *ct,
                               struct sk_buff *skb,
                               enum ip_conntrack_info ctinfo,
                               const struct nf_hook_state *state)
{
        unsigned int *timeout = nf_ct_timeout_lookup(ct);
        static const u8 valid_new[] = {
                [ICMPV6_ECHO_REQUEST - 128] = 1,
                [ICMPV6_NI_QUERY - 128] = 1
        };

        if (state->pf != NFPROTO_IPV6)
                return -NF_ACCEPT;

        if (!nf_ct_is_confirmed(ct)) {
                int type = ct->tuplehash[0].tuple.dst.u.icmp.type - 128;

                if (type < 0 || type >= sizeof(valid_new) || !valid_new[type]) {
                        /* Can't create a new ICMPv6 `conn' with this. */
                        pr_debug("icmpv6: can't create new conn with type %u\n",
                                 type + 128);
                        nf_ct_dump_tuple_ipv6(&ct->tuplehash[0].tuple);
                        return -NF_ACCEPT;
                }
        }

        if (!timeout)
                timeout = icmpv6_get_timeouts(nf_ct_net(ct));

        /* Do not immediately delete the connection after the first
           successful reply to avoid excessive conntrackd traffic
           and also to handle correctly ICMP echo reply duplicates. */
        nf_ct_refresh_acct(ct, ctinfo, skb, *timeout);

        return NF_ACCEPT;
}


static void icmpv6_error_log(const struct sk_buff *skb,
                             const struct nf_hook_state *state,
                             const char *msg)
{
        nf_l4proto_log_invalid(skb, state, IPPROTO_ICMPV6, "%s", msg);
}

static noinline_for_stack int
nf_conntrack_icmpv6_redirect(struct nf_conn *tmpl, struct sk_buff *skb,
                             unsigned int dataoff,
                             const struct nf_hook_state *state)
{
        u8 hl = ipv6_hdr(skb)->hop_limit;
        union nf_inet_addr outer_daddr;
        union {
                struct nd_opt_hdr nd_opt;
                struct rd_msg rd_msg;
        } tmp;
        const struct nd_opt_hdr *nd_opt;
        const struct rd_msg *rd_msg;

        rd_msg = skb_header_pointer(skb, dataoff, sizeof(*rd_msg), &tmp.rd_msg);
        if (!rd_msg) {
                icmpv6_error_log(skb, state, "short redirect");
                return -NF_ACCEPT;
        }

        if (rd_msg->icmph.icmp6_code != 0)
                return NF_ACCEPT;

        if (hl != 255 || !(ipv6_addr_type(&ipv6_hdr(skb)->saddr) & IPV6_ADDR_LINKLOCAL)) {
                icmpv6_error_log(skb, state, "invalid saddr or hoplimit for redirect");
                return -NF_ACCEPT;
        }

        dataoff += sizeof(*rd_msg);

        /* warning: rd_msg no longer usable after this call */
        nd_opt = skb_header_pointer(skb, dataoff, sizeof(*nd_opt), &tmp.nd_opt);
        if (!nd_opt || nd_opt->nd_opt_len == 0) {
                icmpv6_error_log(skb, state, "redirect without options");
                return -NF_ACCEPT;
        }

        /* We could call ndisc_parse_options(), but it would need
         * skb_linearize() and a bit more work.
         */
        if (nd_opt->nd_opt_type != ND_OPT_REDIRECT_HDR)
                return NF_ACCEPT;

        memcpy(&outer_daddr.ip6, &ipv6_hdr(skb)->daddr,
               sizeof(outer_daddr.ip6));
        dataoff += 8;
        return nf_conntrack_inet_error(tmpl, skb, dataoff, state,
                                       IPPROTO_ICMPV6, &outer_daddr);
}

int nf_conntrack_icmpv6_error(struct nf_conn *tmpl,
                              struct sk_buff *skb,
                              unsigned int dataoff,
                              const struct nf_hook_state *state)
{
        union nf_inet_addr outer_daddr;
        const struct icmp6hdr *icmp6h;
        struct icmp6hdr _ih;
        int type;

        icmp6h = skb_header_pointer(skb, dataoff, sizeof(_ih), &_ih);
        if (icmp6h == NULL) {
                icmpv6_error_log(skb, state, "short packet");
                return -NF_ACCEPT;
        }

        if (state->hook == NF_INET_PRE_ROUTING &&
            state->net->ct.sysctl_checksum &&
            nf_ip6_checksum(skb, state->hook, dataoff, IPPROTO_ICMPV6)) {
                icmpv6_error_log(skb, state, "ICMPv6 checksum failed");
                return -NF_ACCEPT;
        }

        type = icmp6h->icmp6_type - 130;
        if (type >= 0 && type < sizeof(noct_valid_new) &&
            noct_valid_new[type]) {
                nf_ct_set(skb, NULL, IP_CT_UNTRACKED);
                return NF_ACCEPT;
        }

        if (icmp6h->icmp6_type == NDISC_REDIRECT)
                return nf_conntrack_icmpv6_redirect(tmpl, skb, dataoff, state);

        /* is not error message ? */
        if (icmp6h->icmp6_type >= 128)
                return NF_ACCEPT;

        memcpy(&outer_daddr.ip6, &ipv6_hdr(skb)->daddr,
               sizeof(outer_daddr.ip6));
        dataoff += sizeof(*icmp6h);
        return nf_conntrack_inet_error(tmpl, skb, dataoff, state,
                                       IPPROTO_ICMPV6, &outer_daddr);
}

#if IS_ENABLED(CONFIG_NF_CT_NETLINK)

#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nfnetlink_conntrack.h>
static int icmpv6_tuple_to_nlattr(struct sk_buff *skb,
                                  const struct nf_conntrack_tuple *t)
{
        if (nla_put_be16(skb, CTA_PROTO_ICMPV6_ID, t->src.u.icmp.id) ||
            nla_put_u8(skb, CTA_PROTO_ICMPV6_TYPE, t->dst.u.icmp.type) ||
            nla_put_u8(skb, CTA_PROTO_ICMPV6_CODE, t->dst.u.icmp.code))
                goto nla_put_failure;
        return 0;

nla_put_failure:
        return -1;
}

static const struct nla_policy icmpv6_nla_policy[CTA_PROTO_MAX+1] = {
        [CTA_PROTO_ICMPV6_TYPE] = { .type = NLA_U8 },
        [CTA_PROTO_ICMPV6_CODE] = { .type = NLA_U8 },
        [CTA_PROTO_ICMPV6_ID]   = { .type = NLA_U16 },
};

static int icmpv6_nlattr_to_tuple(struct nlattr *tb[],
                                struct nf_conntrack_tuple *tuple,
                                u_int32_t flags)
{
        if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMPV6_TYPE)) {
                if (!tb[CTA_PROTO_ICMPV6_TYPE])
                        return -EINVAL;

                tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMPV6_TYPE]);
                if (tuple->dst.u.icmp.type < 128 ||
                    tuple->dst.u.icmp.type - 128 >= sizeof(invmap) ||
                    !invmap[tuple->dst.u.icmp.type - 128])
                        return -EINVAL;
        }

        if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMPV6_CODE)) {
                if (!tb[CTA_PROTO_ICMPV6_CODE])
                        return -EINVAL;

                tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMPV6_CODE]);
        }

        if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMPV6_ID)) {
                if (!tb[CTA_PROTO_ICMPV6_ID])
                        return -EINVAL;

                tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMPV6_ID]);
        }

        return 0;
}

static unsigned int icmpv6_nlattr_tuple_size(void)
{
        static unsigned int size __read_mostly;

        if (!size)
                size = nla_policy_len(icmpv6_nla_policy, CTA_PROTO_MAX + 1);

        return size;
}
#endif

#ifdef CONFIG_NF_CONNTRACK_TIMEOUT

#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nfnetlink_cttimeout.h>

static int icmpv6_timeout_nlattr_to_obj(struct nlattr *tb[],
                                        struct net *net, void *data)
{
        unsigned int *timeout = data;
        struct nf_icmp_net *in = nf_icmpv6_pernet(net);

        if (!timeout)
                timeout = icmpv6_get_timeouts(net);
        if (tb[CTA_TIMEOUT_ICMPV6_TIMEOUT]) {
                *timeout =
                    ntohl(nla_get_be32(tb[CTA_TIMEOUT_ICMPV6_TIMEOUT])) * HZ;
        } else {
                /* Set default ICMPv6 timeout. */
                *timeout = in->timeout;
        }
        return 0;
}

static int
icmpv6_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
{
        const unsigned int *timeout = data;

        if (nla_put_be32(skb, CTA_TIMEOUT_ICMPV6_TIMEOUT, htonl(*timeout / HZ)))
                goto nla_put_failure;
        return 0;

nla_put_failure:
        return -ENOSPC;
}

static const struct nla_policy
icmpv6_timeout_nla_policy[CTA_TIMEOUT_ICMPV6_MAX+1] = {
        [CTA_TIMEOUT_ICMPV6_TIMEOUT]    = { .type = NLA_U32 },
};
#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */

void nf_conntrack_icmpv6_init_net(struct net *net)
{
        struct nf_icmp_net *in = nf_icmpv6_pernet(net);

        in->timeout = nf_ct_icmpv6_timeout;
}

const struct nf_conntrack_l4proto nf_conntrack_l4proto_icmpv6 =
{
        .l4proto                = IPPROTO_ICMPV6,
        .allow_clash            = true,
#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
        .tuple_to_nlattr        = icmpv6_tuple_to_nlattr,
        .nlattr_tuple_size      = icmpv6_nlattr_tuple_size,
        .nlattr_to_tuple        = icmpv6_nlattr_to_tuple,
        .nla_policy             = icmpv6_nla_policy,
#endif
#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
        .ctnl_timeout           = {
                .nlattr_to_obj  = icmpv6_timeout_nlattr_to_obj,
                .obj_to_nlattr  = icmpv6_timeout_obj_to_nlattr,
                .nlattr_max     = CTA_TIMEOUT_ICMP_MAX,
                .obj_size       = sizeof(unsigned int),
                .nla_policy     = icmpv6_timeout_nla_policy,
        },
#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
};