// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (c) 2015 Jiri Pirko <jiri@resnulli.us>
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/rtnetlink.h>
#include <linux/filter.h>
#include <linux/bpf.h>

#include <net/netlink.h>
#include <net/sock.h>
#include <net/pkt_sched.h>
#include <net/pkt_cls.h>

#include <linux/tc_act/tc_bpf.h>
#include <net/tc_act/tc_bpf.h>
#include <net/tc_wrapper.h>

#define ACT_BPF_NAME_LEN        256

struct tcf_bpf_cfg {
        struct bpf_prog *filter;
        struct sock_filter *bpf_ops;
        const char *bpf_name;
        u16 bpf_num_ops;
        bool is_ebpf;
};

static struct tc_action_ops act_bpf_ops;

TC_INDIRECT_SCOPE int tcf_bpf_act(struct sk_buff *skb,
                                  const struct tc_action *act,
                                  struct tcf_result *res)
{
        bool at_ingress = skb_at_tc_ingress(skb);
        struct tcf_bpf *prog = to_bpf(act);
        struct bpf_prog *filter;
        int action, filter_res;

        tcf_lastuse_update(&prog->tcf_tm);
        bstats_update(this_cpu_ptr(prog->common.cpu_bstats), skb);

        filter = rcu_dereference(prog->filter);
        if (at_ingress) {
                __skb_push(skb, skb->mac_len);
                filter_res = bpf_prog_run_data_pointers(filter, skb);
                __skb_pull(skb, skb->mac_len);
        } else {
                filter_res = bpf_prog_run_data_pointers(filter, skb);
        }
        if (unlikely(!skb->tstamp && skb->tstamp_type))
                skb->tstamp_type = SKB_CLOCK_REALTIME;
        if (skb_sk_is_prefetched(skb) && filter_res != TC_ACT_OK)
                skb_orphan(skb);

        /* A BPF program may overwrite the default action opcode.
         * Similarly as in cls_bpf, if filter_res == -1 we use the
         * default action specified from tc.
         *
         * In case a different well-known TC_ACT opcode has been
         * returned, it will overwrite the default one.
         *
         * For everything else that is unknown, TC_ACT_UNSPEC is
         * returned.
         */
        switch (filter_res) {
        case TC_ACT_PIPE:
        case TC_ACT_RECLASSIFY:
        case TC_ACT_OK:
        case TC_ACT_REDIRECT:
                action = filter_res;
                break;
        case TC_ACT_SHOT:
                action = filter_res;
                qstats_drop_inc(this_cpu_ptr(prog->common.cpu_qstats));
                break;
        case TC_ACT_UNSPEC:
                action = prog->tcf_action;
                break;
        default:
                action = TC_ACT_UNSPEC;
                break;
        }

        return action;
}

static bool tcf_bpf_is_ebpf(const struct tcf_bpf *prog)
{
        return !prog->bpf_ops;
}

static int tcf_bpf_dump_bpf_info(const struct tcf_bpf *prog,
                                 struct sk_buff *skb)
{
        struct nlattr *nla;

        if (nla_put_u16(skb, TCA_ACT_BPF_OPS_LEN, prog->bpf_num_ops))
                return -EMSGSIZE;

        nla = nla_reserve(skb, TCA_ACT_BPF_OPS, prog->bpf_num_ops *
                          sizeof(struct sock_filter));
        if (nla == NULL)
                return -EMSGSIZE;

        memcpy(nla_data(nla), prog->bpf_ops, nla_len(nla));

        return 0;
}

static int tcf_bpf_dump_ebpf_info(const struct tcf_bpf *prog,
                                  struct sk_buff *skb)
{
        struct nlattr *nla;

        if (prog->bpf_name &&
            nla_put_string(skb, TCA_ACT_BPF_NAME, prog->bpf_name))
                return -EMSGSIZE;

        if (nla_put_u32(skb, TCA_ACT_BPF_ID, prog->filter->aux->id))
                return -EMSGSIZE;

        nla = nla_reserve(skb, TCA_ACT_BPF_TAG, sizeof(prog->filter->tag));
        if (nla == NULL)
                return -EMSGSIZE;

        memcpy(nla_data(nla), prog->filter->tag, nla_len(nla));

        return 0;
}

static int tcf_bpf_dump(struct sk_buff *skb, struct tc_action *act,
                        int bind, int ref)
{
        unsigned char *tp = skb_tail_pointer(skb);
        struct tcf_bpf *prog = to_bpf(act);
        struct tc_act_bpf opt = {
                .index   = prog->tcf_index,
                .refcnt  = refcount_read(&prog->tcf_refcnt) - ref,
                .bindcnt = atomic_read(&prog->tcf_bindcnt) - bind,
        };
        struct tcf_t tm;
        int ret;

        spin_lock_bh(&prog->tcf_lock);
        opt.action = prog->tcf_action;
        if (nla_put(skb, TCA_ACT_BPF_PARMS, sizeof(opt), &opt))
                goto nla_put_failure;

        if (tcf_bpf_is_ebpf(prog))
                ret = tcf_bpf_dump_ebpf_info(prog, skb);
        else
                ret = tcf_bpf_dump_bpf_info(prog, skb);
        if (ret)
                goto nla_put_failure;

        tcf_tm_dump(&tm, &prog->tcf_tm);
        if (nla_put_64bit(skb, TCA_ACT_BPF_TM, sizeof(tm), &tm,
                          TCA_ACT_BPF_PAD))
                goto nla_put_failure;

        spin_unlock_bh(&prog->tcf_lock);
        return skb->len;

nla_put_failure:
        spin_unlock_bh(&prog->tcf_lock);
        nlmsg_trim(skb, tp);
        return -1;
}

static const struct nla_policy act_bpf_policy[TCA_ACT_BPF_MAX + 1] = {
        [TCA_ACT_BPF_PARMS]     = { .len = sizeof(struct tc_act_bpf) },
        [TCA_ACT_BPF_FD]        = { .type = NLA_U32 },
        [TCA_ACT_BPF_NAME]      = { .type = NLA_NUL_STRING,
                                    .len = ACT_BPF_NAME_LEN },
        [TCA_ACT_BPF_OPS_LEN]   = { .type = NLA_U16 },
        [TCA_ACT_BPF_OPS]       = { .type = NLA_BINARY,
                                    .len = sizeof(struct sock_filter) * BPF_MAXINSNS },
};

static int tcf_bpf_init_from_ops(struct nlattr **tb, struct tcf_bpf_cfg *cfg)
{
        struct sock_filter *bpf_ops;
        struct sock_fprog_kern fprog_tmp;
        struct bpf_prog *fp;
        u16 bpf_size, bpf_num_ops;
        int ret;

        bpf_num_ops = nla_get_u16(tb[TCA_ACT_BPF_OPS_LEN]);
        if (bpf_num_ops > BPF_MAXINSNS || bpf_num_ops == 0)
                return -EINVAL;

        bpf_size = bpf_num_ops * sizeof(*bpf_ops);
        if (bpf_size != nla_len(tb[TCA_ACT_BPF_OPS]))
                return -EINVAL;

        bpf_ops = kmemdup(nla_data(tb[TCA_ACT_BPF_OPS]), bpf_size, GFP_KERNEL);
        if (bpf_ops == NULL)
                return -ENOMEM;

        fprog_tmp.len = bpf_num_ops;
        fprog_tmp.filter = bpf_ops;

        ret = bpf_prog_create(&fp, &fprog_tmp);
        if (ret < 0) {
                kfree(bpf_ops);
                return ret;
        }

        cfg->bpf_ops = bpf_ops;
        cfg->bpf_num_ops = bpf_num_ops;
        cfg->filter = fp;
        cfg->is_ebpf = false;

        return 0;
}

static int tcf_bpf_init_from_efd(struct nlattr **tb, struct tcf_bpf_cfg *cfg)
{
        struct bpf_prog *fp;
        char *name = NULL;
        u32 bpf_fd;

        bpf_fd = nla_get_u32(tb[TCA_ACT_BPF_FD]);

        fp = bpf_prog_get_type(bpf_fd, BPF_PROG_TYPE_SCHED_ACT);
        if (IS_ERR(fp))
                return PTR_ERR(fp);

        if (tb[TCA_ACT_BPF_NAME]) {
                name = nla_memdup(tb[TCA_ACT_BPF_NAME], GFP_KERNEL);
                if (!name) {
                        bpf_prog_put(fp);
                        return -ENOMEM;
                }
        }

        cfg->bpf_name = name;
        cfg->filter = fp;
        cfg->is_ebpf = true;

        return 0;
}

static void tcf_bpf_cfg_cleanup(const struct tcf_bpf_cfg *cfg)
{
        struct bpf_prog *filter = cfg->filter;

        if (filter) {
                if (cfg->is_ebpf)
                        bpf_prog_put(filter);
                else
                        bpf_prog_destroy(filter);
        }

        kfree(cfg->bpf_ops);
        kfree(cfg->bpf_name);
}

static void tcf_bpf_prog_fill_cfg(const struct tcf_bpf *prog,
                                  struct tcf_bpf_cfg *cfg)
{
        cfg->is_ebpf = tcf_bpf_is_ebpf(prog);
        /* updates to prog->filter are prevented, since it's called either
         * with tcf lock or during final cleanup in rcu callback
         */
        cfg->filter = rcu_dereference_protected(prog->filter, 1);

        cfg->bpf_ops = prog->bpf_ops;
        cfg->bpf_name = prog->bpf_name;
}

static int tcf_bpf_init(struct net *net, struct nlattr *nla,
                        struct nlattr *est, struct tc_action **act,
                        struct tcf_proto *tp, u32 flags,
                        struct netlink_ext_ack *extack)
{
        struct tc_action_net *tn = net_generic(net, act_bpf_ops.net_id);
        bool bind = flags & TCA_ACT_FLAGS_BIND;
        struct nlattr *tb[TCA_ACT_BPF_MAX + 1];
        struct tcf_chain *goto_ch = NULL;
        struct tcf_bpf_cfg cfg, old;
        struct tc_act_bpf *parm;
        struct tcf_bpf *prog;
        bool is_bpf, is_ebpf;
        int ret, res = 0;
        u32 index;

        if (!nla)
                return -EINVAL;

        ret = nla_parse_nested_deprecated(tb, TCA_ACT_BPF_MAX, nla,
                                          act_bpf_policy, NULL);
        if (ret < 0)
                return ret;

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

        parm = nla_data(tb[TCA_ACT_BPF_PARMS]);
        index = parm->index;
        ret = tcf_idr_check_alloc(tn, &index, act, bind);
        if (!ret) {
                ret = tcf_idr_create(tn, index, est, act,
                                     &act_bpf_ops, bind, true, flags);
                if (ret < 0) {
                        tcf_idr_cleanup(tn, index);
                        return ret;
                }

                res = ACT_P_CREATED;
        } else if (ret > 0) {
                /* Don't override defaults. */
                if (bind)
                        return ACT_P_BOUND;

                if (!(flags & TCA_ACT_FLAGS_REPLACE)) {
                        tcf_idr_release(*act, bind);
                        return -EEXIST;
                }
        } else {
                return ret;
        }

        ret = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
        if (ret < 0)
                goto release_idr;

        is_bpf = tb[TCA_ACT_BPF_OPS_LEN] && tb[TCA_ACT_BPF_OPS];
        is_ebpf = tb[TCA_ACT_BPF_FD];

        if (is_bpf == is_ebpf) {
                ret = -EINVAL;
                goto put_chain;
        }

        memset(&cfg, 0, sizeof(cfg));

        ret = is_bpf ? tcf_bpf_init_from_ops(tb, &cfg) :
                       tcf_bpf_init_from_efd(tb, &cfg);
        if (ret < 0)
                goto put_chain;

        prog = to_bpf(*act);

        spin_lock_bh(&prog->tcf_lock);
        if (res != ACT_P_CREATED)
                tcf_bpf_prog_fill_cfg(prog, &old);

        prog->bpf_ops = cfg.bpf_ops;
        prog->bpf_name = cfg.bpf_name;

        if (cfg.bpf_num_ops)
                prog->bpf_num_ops = cfg.bpf_num_ops;

        goto_ch = tcf_action_set_ctrlact(*act, parm->action, goto_ch);
        rcu_assign_pointer(prog->filter, cfg.filter);
        spin_unlock_bh(&prog->tcf_lock);

        if (goto_ch)
                tcf_chain_put_by_act(goto_ch);

        if (res != ACT_P_CREATED) {
                /* make sure the program being replaced is no longer executing */
                synchronize_rcu();
                tcf_bpf_cfg_cleanup(&old);
        }

        return res;

put_chain:
        if (goto_ch)
                tcf_chain_put_by_act(goto_ch);

release_idr:
        tcf_idr_release(*act, bind);
        return ret;
}

static void tcf_bpf_cleanup(struct tc_action *act)
{
        struct tcf_bpf_cfg tmp;

        tcf_bpf_prog_fill_cfg(to_bpf(act), &tmp);
        tcf_bpf_cfg_cleanup(&tmp);
}

static struct tc_action_ops act_bpf_ops __read_mostly = {
        .kind           =       "bpf",
        .id             =       TCA_ID_BPF,
        .owner          =       THIS_MODULE,
        .act            =       tcf_bpf_act,
        .dump           =       tcf_bpf_dump,
        .cleanup        =       tcf_bpf_cleanup,
        .init           =       tcf_bpf_init,
        .size           =       sizeof(struct tcf_bpf),
};
MODULE_ALIAS_NET_ACT("bpf");

static __net_init int bpf_init_net(struct net *net)
{
        struct tc_action_net *tn = net_generic(net, act_bpf_ops.net_id);

        return tc_action_net_init(net, tn, &act_bpf_ops);
}

static void __net_exit bpf_exit_net(struct list_head *net_list)
{
        tc_action_net_exit(net_list, act_bpf_ops.net_id);
}

static struct pernet_operations bpf_net_ops = {
        .init = bpf_init_net,
        .exit_batch = bpf_exit_net,
        .id   = &act_bpf_ops.net_id,
        .size = sizeof(struct tc_action_net),
};

static int __init bpf_init_module(void)
{
        return tcf_register_action(&act_bpf_ops, &bpf_net_ops);
}

static void __exit bpf_cleanup_module(void)
{
        tcf_unregister_action(&act_bpf_ops, &bpf_net_ops);
}

module_init(bpf_init_module);
module_exit(bpf_cleanup_module);

MODULE_AUTHOR("Jiri Pirko <jiri@resnulli.us>");
MODULE_DESCRIPTION("TC BPF based action");
MODULE_LICENSE("GPL v2");