/* SPDX-License-Identifier: GPL-2.0 */
#include <linux/module.h>
#include <linux/netfilter/nf_tables.h>
#include <net/netfilter/nf_tables.h>
#include <net/netfilter/nf_tables_core.h>
#include <net/netfilter/nf_socket.h>
#include <net/inet_sock.h>
#include <net/tcp.h>

struct nft_socket {
        enum nft_socket_keys            key:8;
        u8                              level;          /* cgroupv2 level to extract */
        u8                              level_user;     /* cgroupv2 level provided by userspace */
        u8                              len;
        union {
                u8                      dreg;
        };
};

static void nft_socket_wildcard(const struct nft_pktinfo *pkt,
                                struct nft_regs *regs, struct sock *sk,
                                u32 *dest)
{
        switch (nft_pf(pkt)) {
        case NFPROTO_IPV4:
                nft_reg_store8(dest, inet_sk(sk)->inet_rcv_saddr == 0);
                break;
#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
        case NFPROTO_IPV6:
                nft_reg_store8(dest, ipv6_addr_any(&sk->sk_v6_rcv_saddr));
                break;
#endif
        default:
                regs->verdict.code = NFT_BREAK;
                return;
        }
}

#ifdef CONFIG_SOCK_CGROUP_DATA
static noinline bool
nft_sock_get_eval_cgroupv2(u32 *dest, struct sock *sk, const struct nft_pktinfo *pkt, u32 level)
{
        struct cgroup *cgrp;
        u64 cgid;

        if (!sk_fullsock(sk))
                return false;

        cgrp = cgroup_ancestor(sock_cgroup_ptr(&sk->sk_cgrp_data), level);
        if (!cgrp)
                return false;

        cgid = cgroup_id(cgrp);
        memcpy(dest, &cgid, sizeof(u64));
        return true;
}

/* process context only, uses current->nsproxy. */
static noinline int nft_socket_cgroup_subtree_level(void)
{
        struct cgroup *cgrp = cgroup_get_from_path("/");
        int level;

        if (IS_ERR(cgrp))
                return PTR_ERR(cgrp);

        level = cgrp->level;

        cgroup_put(cgrp);

        if (level > 255)
                return -ERANGE;

        if (WARN_ON_ONCE(level < 0))
                return -EINVAL;

        return level;
}
#endif

static struct sock *nft_socket_do_lookup(const struct nft_pktinfo *pkt)
{
        const struct net_device *indev = nft_in(pkt);
        const struct sk_buff *skb = pkt->skb;
        struct sock *sk = NULL;

        if (!indev)
                return NULL;

        switch (nft_pf(pkt)) {
        case NFPROTO_IPV4:
                sk = nf_sk_lookup_slow_v4(nft_net(pkt), skb, indev);
                break;
#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
        case NFPROTO_IPV6:
                sk = nf_sk_lookup_slow_v6(nft_net(pkt), skb, indev);
                break;
#endif
        default:
                WARN_ON_ONCE(1);
                break;
        }

        return sk;
}

static void nft_socket_eval(const struct nft_expr *expr,
                            struct nft_regs *regs,
                            const struct nft_pktinfo *pkt)
{
        const struct nft_socket *priv = nft_expr_priv(expr);
        struct sk_buff *skb = pkt->skb;
        struct sock *sk = skb->sk;
        u32 *dest = &regs->data[priv->dreg];

        if (sk && !net_eq(nft_net(pkt), sock_net(sk)))
                sk = NULL;

        if (!sk)
                sk = nft_socket_do_lookup(pkt);

        if (!sk) {
                regs->verdict.code = NFT_BREAK;
                return;
        }

        switch(priv->key) {
        case NFT_SOCKET_TRANSPARENT:
                nft_reg_store8(dest, inet_sk_transparent(sk));
                break;
        case NFT_SOCKET_MARK:
                if (sk_fullsock(sk)) {
                        *dest = READ_ONCE(sk->sk_mark);
                } else {
                        regs->verdict.code = NFT_BREAK;
                        goto out_put_sk;
                }
                break;
        case NFT_SOCKET_WILDCARD:
                if (!sk_fullsock(sk)) {
                        regs->verdict.code = NFT_BREAK;
                        goto out_put_sk;
                }
                nft_socket_wildcard(pkt, regs, sk, dest);
                break;
#ifdef CONFIG_SOCK_CGROUP_DATA
        case NFT_SOCKET_CGROUPV2:
                if (!nft_sock_get_eval_cgroupv2(dest, sk, pkt, priv->level)) {
                        regs->verdict.code = NFT_BREAK;
                        goto out_put_sk;
                }
                break;
#endif
        default:
                WARN_ON(1);
                regs->verdict.code = NFT_BREAK;
        }

out_put_sk:
        if (sk != skb->sk)
                sock_gen_put(sk);
}

static const struct nla_policy nft_socket_policy[NFTA_SOCKET_MAX + 1] = {
        [NFTA_SOCKET_KEY]               = NLA_POLICY_MAX(NLA_BE32, 255),
        [NFTA_SOCKET_DREG]              = { .type = NLA_U32 },
        [NFTA_SOCKET_LEVEL]             = NLA_POLICY_MAX(NLA_BE32, 255),
};

static int nft_socket_init(const struct nft_ctx *ctx,
                           const struct nft_expr *expr,
                           const struct nlattr * const tb[])
{
        struct nft_socket *priv = nft_expr_priv(expr);
        unsigned int len;

        if (!tb[NFTA_SOCKET_DREG] || !tb[NFTA_SOCKET_KEY])
                return -EINVAL;

        switch(ctx->family) {
        case NFPROTO_IPV4:
#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
        case NFPROTO_IPV6:
#endif
        case NFPROTO_INET:
                break;
        default:
                return -EOPNOTSUPP;
        }

        priv->key = ntohl(nla_get_be32(tb[NFTA_SOCKET_KEY]));
        switch(priv->key) {
        case NFT_SOCKET_TRANSPARENT:
        case NFT_SOCKET_WILDCARD:
                len = sizeof(u8);
                break;
        case NFT_SOCKET_MARK:
                len = sizeof(u32);
                break;
#ifdef CONFIG_SOCK_CGROUP_DATA
        case NFT_SOCKET_CGROUPV2: {
                unsigned int level;
                int err;

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

                level = ntohl(nla_get_be32(tb[NFTA_SOCKET_LEVEL]));
                if (level > 255)
                        return -EOPNOTSUPP;

                err = nft_socket_cgroup_subtree_level();
                if (err < 0)
                        return err;

                priv->level_user = level;

                level += err;
                /* Implies a giant cgroup tree */
                if (level > 255)
                        return -EOPNOTSUPP;

                priv->level = level;
                len = sizeof(u64);
                break;
        }
#endif
        default:
                return -EOPNOTSUPP;
        }

        priv->len = len;
        return nft_parse_register_store(ctx, tb[NFTA_SOCKET_DREG], &priv->dreg,
                                        NULL, NFT_DATA_VALUE, len);
}

static int nft_socket_dump(struct sk_buff *skb,
                           const struct nft_expr *expr, bool reset)
{
        const struct nft_socket *priv = nft_expr_priv(expr);

        if (nla_put_be32(skb, NFTA_SOCKET_KEY, htonl(priv->key)))
                return -1;
        if (nft_dump_register(skb, NFTA_SOCKET_DREG, priv->dreg))
                return -1;
        if (priv->key == NFT_SOCKET_CGROUPV2 &&
            nla_put_be32(skb, NFTA_SOCKET_LEVEL, htonl(priv->level_user)))
                return -1;
        return 0;
}

static bool nft_socket_reduce(struct nft_regs_track *track,
                              const struct nft_expr *expr)
{
        const struct nft_socket *priv = nft_expr_priv(expr);
        const struct nft_socket *socket;

        if (!nft_reg_track_cmp(track, expr, priv->dreg)) {
                nft_reg_track_update(track, expr, priv->dreg, priv->len);
                return false;
        }

        socket = nft_expr_priv(track->regs[priv->dreg].selector);
        if (priv->key != socket->key ||
            priv->dreg != socket->dreg ||
            priv->level != socket->level) {
                nft_reg_track_update(track, expr, priv->dreg, priv->len);
                return false;
        }

        if (!track->regs[priv->dreg].bitwise)
                return true;

        return nft_expr_reduce_bitwise(track, expr);
}

static int nft_socket_validate(const struct nft_ctx *ctx,
                               const struct nft_expr *expr)
{
        if (ctx->family != NFPROTO_IPV4 &&
            ctx->family != NFPROTO_IPV6 &&
            ctx->family != NFPROTO_INET)
                return -EOPNOTSUPP;

        return nft_chain_validate_hooks(ctx->chain,
                                        (1 << NF_INET_PRE_ROUTING) |
                                        (1 << NF_INET_LOCAL_IN) |
                                        (1 << NF_INET_LOCAL_OUT));
}

static struct nft_expr_type nft_socket_type;
static const struct nft_expr_ops nft_socket_ops = {
        .type           = &nft_socket_type,
        .size           = NFT_EXPR_SIZE(sizeof(struct nft_socket)),
        .eval           = nft_socket_eval,
        .init           = nft_socket_init,
        .dump           = nft_socket_dump,
        .validate       = nft_socket_validate,
        .reduce         = nft_socket_reduce,
};

static struct nft_expr_type nft_socket_type __read_mostly = {
        .name           = "socket",
        .ops            = &nft_socket_ops,
        .policy         = nft_socket_policy,
        .maxattr        = NFTA_SOCKET_MAX,
        .owner          = THIS_MODULE,
};

static int __init nft_socket_module_init(void)
{
        return nft_register_expr(&nft_socket_type);
}

static void __exit nft_socket_module_exit(void)
{
        nft_unregister_expr(&nft_socket_type);
}

module_init(nft_socket_module_init);
module_exit(nft_socket_module_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Máté Eckl");
MODULE_DESCRIPTION("nf_tables socket match module");
MODULE_ALIAS_NFT_EXPR("socket");