// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * net/sched/act_skbmod.c  skb data modifier
 *
 * Copyright (c) 2016 Jamal Hadi Salim <jhs@mojatatu.com>
*/

#include <linux/module.h>
#include <linux/if_arp.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/rtnetlink.h>
#include <net/inet_ecn.h>
#include <net/netlink.h>
#include <net/pkt_sched.h>
#include <net/pkt_cls.h>
#include <net/tc_wrapper.h>

#include <linux/tc_act/tc_skbmod.h>
#include <net/tc_act/tc_skbmod.h>

static struct tc_action_ops act_skbmod_ops;

TC_INDIRECT_SCOPE int tcf_skbmod_act(struct sk_buff *skb,
                                     const struct tc_action *a,
                                     struct tcf_result *res)
{
        struct tcf_skbmod *d = to_skbmod(a);
        struct tcf_skbmod_params *p;
        int max_edit_len, err;
        u64 flags;

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

        p = rcu_dereference_bh(d->skbmod_p);
        if (unlikely(p->action == TC_ACT_SHOT))
                goto drop;

        max_edit_len = skb_mac_header_len(skb);
        flags = p->flags;

        /* tcf_skbmod_init() guarantees "flags" to be one of the following:
         *      1. a combination of SKBMOD_F_{DMAC,SMAC,ETYPE}
         *      2. SKBMOD_F_SWAPMAC
         *      3. SKBMOD_F_ECN
         * SKBMOD_F_ECN only works with IP packets; all other flags only work with Ethernet
         * packets.
         */
        if (flags == SKBMOD_F_ECN) {
                switch (skb_protocol(skb, true)) {
                case cpu_to_be16(ETH_P_IP):
                case cpu_to_be16(ETH_P_IPV6):
                        max_edit_len += skb_network_header_len(skb);
                        break;
                default:
                        goto out;
                }
        } else if (!skb->dev || skb->dev->type != ARPHRD_ETHER) {
                goto out;
        }

        err = skb_ensure_writable(skb, max_edit_len);
        if (unlikely(err)) /* best policy is to drop on the floor */
                goto drop;

        if (flags & SKBMOD_F_DMAC)
                ether_addr_copy(eth_hdr(skb)->h_dest, p->eth_dst);
        if (flags & SKBMOD_F_SMAC)
                ether_addr_copy(eth_hdr(skb)->h_source, p->eth_src);
        if (flags & SKBMOD_F_ETYPE)
                eth_hdr(skb)->h_proto = p->eth_type;

        if (flags & SKBMOD_F_SWAPMAC) {
                u16 tmpaddr[ETH_ALEN / 2]; /* ether_addr_copy() requirement */
                /*XXX: I am sure we can come up with more efficient swapping*/
                ether_addr_copy((u8 *)tmpaddr, eth_hdr(skb)->h_dest);
                ether_addr_copy(eth_hdr(skb)->h_dest, eth_hdr(skb)->h_source);
                ether_addr_copy(eth_hdr(skb)->h_source, (u8 *)tmpaddr);
        }

        if (flags & SKBMOD_F_ECN)
                INET_ECN_set_ce(skb);

out:
        return p->action;

drop:
        qstats_overlimit_inc(this_cpu_ptr(d->common.cpu_qstats));
        return TC_ACT_SHOT;
}

static const struct nla_policy skbmod_policy[TCA_SKBMOD_MAX + 1] = {
        [TCA_SKBMOD_PARMS]              = { .len = sizeof(struct tc_skbmod) },
        [TCA_SKBMOD_DMAC]               = { .len = ETH_ALEN },
        [TCA_SKBMOD_SMAC]               = { .len = ETH_ALEN },
        [TCA_SKBMOD_ETYPE]              = { .type = NLA_U16 },
};

static int tcf_skbmod_init(struct net *net, struct nlattr *nla,
                           struct nlattr *est, struct tc_action **a,
                           struct tcf_proto *tp, u32 flags,
                           struct netlink_ext_ack *extack)
{
        struct tc_action_net *tn = net_generic(net, act_skbmod_ops.net_id);
        bool ovr = flags & TCA_ACT_FLAGS_REPLACE;
        bool bind = flags & TCA_ACT_FLAGS_BIND;
        struct nlattr *tb[TCA_SKBMOD_MAX + 1];
        struct tcf_skbmod_params *p, *p_old;
        struct tcf_chain *goto_ch = NULL;
        struct tc_skbmod *parm;
        u32 lflags = 0, index;
        struct tcf_skbmod *d;
        bool exists = false;
        u8 *daddr = NULL;
        u8 *saddr = NULL;
        u16 eth_type = 0;
        int ret = 0, err;

        if (!nla)
                return -EINVAL;

        err = nla_parse_nested_deprecated(tb, TCA_SKBMOD_MAX, nla,
                                          skbmod_policy, NULL);
        if (err < 0)
                return err;

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

        if (tb[TCA_SKBMOD_DMAC]) {
                daddr = nla_data(tb[TCA_SKBMOD_DMAC]);
                lflags |= SKBMOD_F_DMAC;
        }

        if (tb[TCA_SKBMOD_SMAC]) {
                saddr = nla_data(tb[TCA_SKBMOD_SMAC]);
                lflags |= SKBMOD_F_SMAC;
        }

        if (tb[TCA_SKBMOD_ETYPE]) {
                eth_type = nla_get_u16(tb[TCA_SKBMOD_ETYPE]);
                lflags |= SKBMOD_F_ETYPE;
        }

        parm = nla_data(tb[TCA_SKBMOD_PARMS]);
        index = parm->index;
        if (parm->flags & SKBMOD_F_SWAPMAC)
                lflags = SKBMOD_F_SWAPMAC;
        if (parm->flags & SKBMOD_F_ECN)
                lflags = SKBMOD_F_ECN;

        err = tcf_idr_check_alloc(tn, &index, a, bind);
        if (err < 0)
                return err;
        exists = err;
        if (exists && bind)
                return ACT_P_BOUND;

        if (!lflags) {
                if (exists)
                        tcf_idr_release(*a, bind);
                else
                        tcf_idr_cleanup(tn, index);
                return -EINVAL;
        }

        if (!exists) {
                ret = tcf_idr_create(tn, index, est, a,
                                     &act_skbmod_ops, bind, true, flags);
                if (ret) {
                        tcf_idr_cleanup(tn, index);
                        return ret;
                }

                ret = ACT_P_CREATED;
        } else if (!ovr) {
                tcf_idr_release(*a, bind);
                return -EEXIST;
        }
        err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
        if (err < 0)
                goto release_idr;

        d = to_skbmod(*a);

        p = kzalloc_obj(struct tcf_skbmod_params);
        if (unlikely(!p)) {
                err = -ENOMEM;
                goto put_chain;
        }

        p->flags = lflags;
        p->action = parm->action;
        if (ovr)
                spin_lock_bh(&d->tcf_lock);
        /* Protected by tcf_lock if overwriting existing action. */
        goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
        p_old = rcu_dereference_protected(d->skbmod_p, 1);

        if (lflags & SKBMOD_F_DMAC)
                ether_addr_copy(p->eth_dst, daddr);
        if (lflags & SKBMOD_F_SMAC)
                ether_addr_copy(p->eth_src, saddr);
        if (lflags & SKBMOD_F_ETYPE)
                p->eth_type = htons(eth_type);

        rcu_assign_pointer(d->skbmod_p, p);
        if (ovr)
                spin_unlock_bh(&d->tcf_lock);

        if (p_old)
                kfree_rcu(p_old, rcu);
        if (goto_ch)
                tcf_chain_put_by_act(goto_ch);

        return ret;
put_chain:
        if (goto_ch)
                tcf_chain_put_by_act(goto_ch);
release_idr:
        tcf_idr_release(*a, bind);
        return err;
}

static void tcf_skbmod_cleanup(struct tc_action *a)
{
        struct tcf_skbmod *d = to_skbmod(a);
        struct tcf_skbmod_params  *p;

        p = rcu_dereference_protected(d->skbmod_p, 1);
        if (p)
                kfree_rcu(p, rcu);
}

static int tcf_skbmod_dump(struct sk_buff *skb, struct tc_action *a,
                           int bind, int ref)
{
        struct tcf_skbmod *d = to_skbmod(a);
        unsigned char *b = skb_tail_pointer(skb);
        struct tcf_skbmod_params  *p;
        struct tc_skbmod opt;
        struct tcf_t t;

        memset(&opt, 0, sizeof(opt));
        opt.index   = d->tcf_index;
        opt.refcnt  = refcount_read(&d->tcf_refcnt) - ref;
        opt.bindcnt = atomic_read(&d->tcf_bindcnt) - bind;
        rcu_read_lock();
        p = rcu_dereference(d->skbmod_p);
        opt.action = p->action;
        opt.flags  = p->flags;
        if (nla_put(skb, TCA_SKBMOD_PARMS, sizeof(opt), &opt))
                goto nla_put_failure;
        if ((p->flags & SKBMOD_F_DMAC) &&
            nla_put(skb, TCA_SKBMOD_DMAC, ETH_ALEN, p->eth_dst))
                goto nla_put_failure;
        if ((p->flags & SKBMOD_F_SMAC) &&
            nla_put(skb, TCA_SKBMOD_SMAC, ETH_ALEN, p->eth_src))
                goto nla_put_failure;
        if ((p->flags & SKBMOD_F_ETYPE) &&
            nla_put_u16(skb, TCA_SKBMOD_ETYPE, ntohs(p->eth_type)))
                goto nla_put_failure;

        tcf_tm_dump(&t, &d->tcf_tm);
        if (nla_put_64bit(skb, TCA_SKBMOD_TM, sizeof(t), &t, TCA_SKBMOD_PAD))
                goto nla_put_failure;

        rcu_read_unlock();
        return skb->len;
nla_put_failure:
        rcu_read_unlock();
        nlmsg_trim(skb, b);
        return -1;
}

static struct tc_action_ops act_skbmod_ops = {
        .kind           =       "skbmod",
        .id             =       TCA_ACT_SKBMOD,
        .owner          =       THIS_MODULE,
        .act            =       tcf_skbmod_act,
        .dump           =       tcf_skbmod_dump,
        .init           =       tcf_skbmod_init,
        .cleanup        =       tcf_skbmod_cleanup,
        .size           =       sizeof(struct tcf_skbmod),
};
MODULE_ALIAS_NET_ACT("skbmod");

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

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

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

static struct pernet_operations skbmod_net_ops = {
        .init = skbmod_init_net,
        .exit_batch = skbmod_exit_net,
        .id   = &act_skbmod_ops.net_id,
        .size = sizeof(struct tc_action_net),
};

MODULE_AUTHOR("Jamal Hadi Salim, <jhs@mojatatu.com>");
MODULE_DESCRIPTION("SKB data mod-ing");
MODULE_LICENSE("GPL");

static int __init skbmod_init_module(void)
{
        return tcf_register_action(&act_skbmod_ops, &skbmod_net_ops);
}

static void __exit skbmod_cleanup_module(void)
{
        tcf_unregister_action(&act_skbmod_ops, &skbmod_net_ops);
}

module_init(skbmod_init_module);
module_exit(skbmod_cleanup_module);