linux/net/sched/act_skbmod.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * net/sched/act_skbmod.c  skb data modifier
   4 *
   5 * Copyright (c) 2016 Jamal Hadi Salim <jhs@mojatatu.com>
   6*/
   7
   8#include <linux/module.h>
   9#include <linux/if_arp.h>
  10#include <linux/init.h>
  11#include <linux/kernel.h>
  12#include <linux/skbuff.h>
  13#include <linux/rtnetlink.h>
  14#include <net/netlink.h>
  15#include <net/pkt_sched.h>
  16#include <net/pkt_cls.h>
  17
  18#include <linux/tc_act/tc_skbmod.h>
  19#include <net/tc_act/tc_skbmod.h>
  20
  21static unsigned int skbmod_net_id;
  22static struct tc_action_ops act_skbmod_ops;
  23
  24#define MAX_EDIT_LEN ETH_HLEN
  25static int tcf_skbmod_act(struct sk_buff *skb, const struct tc_action *a,
  26                          struct tcf_result *res)
  27{
  28        struct tcf_skbmod *d = to_skbmod(a);
  29        int action;
  30        struct tcf_skbmod_params *p;
  31        u64 flags;
  32        int err;
  33
  34        tcf_lastuse_update(&d->tcf_tm);
  35        bstats_cpu_update(this_cpu_ptr(d->common.cpu_bstats), skb);
  36
  37        action = READ_ONCE(d->tcf_action);
  38        if (unlikely(action == TC_ACT_SHOT))
  39                goto drop;
  40
  41        if (!skb->dev || skb->dev->type != ARPHRD_ETHER)
  42                return action;
  43
  44        /* XXX: if you are going to edit more fields beyond ethernet header
  45         * (example when you add IP header replacement or vlan swap)
  46         * then MAX_EDIT_LEN needs to change appropriately
  47        */
  48        err = skb_ensure_writable(skb, MAX_EDIT_LEN);
  49        if (unlikely(err)) /* best policy is to drop on the floor */
  50                goto drop;
  51
  52        p = rcu_dereference_bh(d->skbmod_p);
  53        flags = p->flags;
  54        if (flags & SKBMOD_F_DMAC)
  55                ether_addr_copy(eth_hdr(skb)->h_dest, p->eth_dst);
  56        if (flags & SKBMOD_F_SMAC)
  57                ether_addr_copy(eth_hdr(skb)->h_source, p->eth_src);
  58        if (flags & SKBMOD_F_ETYPE)
  59                eth_hdr(skb)->h_proto = p->eth_type;
  60
  61        if (flags & SKBMOD_F_SWAPMAC) {
  62                u16 tmpaddr[ETH_ALEN / 2]; /* ether_addr_copy() requirement */
  63                /*XXX: I am sure we can come up with more efficient swapping*/
  64                ether_addr_copy((u8 *)tmpaddr, eth_hdr(skb)->h_dest);
  65                ether_addr_copy(eth_hdr(skb)->h_dest, eth_hdr(skb)->h_source);
  66                ether_addr_copy(eth_hdr(skb)->h_source, (u8 *)tmpaddr);
  67        }
  68
  69        return action;
  70
  71drop:
  72        qstats_overlimit_inc(this_cpu_ptr(d->common.cpu_qstats));
  73        return TC_ACT_SHOT;
  74}
  75
  76static const struct nla_policy skbmod_policy[TCA_SKBMOD_MAX + 1] = {
  77        [TCA_SKBMOD_PARMS]              = { .len = sizeof(struct tc_skbmod) },
  78        [TCA_SKBMOD_DMAC]               = { .len = ETH_ALEN },
  79        [TCA_SKBMOD_SMAC]               = { .len = ETH_ALEN },
  80        [TCA_SKBMOD_ETYPE]              = { .type = NLA_U16 },
  81};
  82
  83static int tcf_skbmod_init(struct net *net, struct nlattr *nla,
  84                           struct nlattr *est, struct tc_action **a,
  85                           int ovr, int bind, bool rtnl_held,
  86                           struct tcf_proto *tp, u32 flags,
  87                           struct netlink_ext_ack *extack)
  88{
  89        struct tc_action_net *tn = net_generic(net, skbmod_net_id);
  90        struct nlattr *tb[TCA_SKBMOD_MAX + 1];
  91        struct tcf_skbmod_params *p, *p_old;
  92        struct tcf_chain *goto_ch = NULL;
  93        struct tc_skbmod *parm;
  94        u32 lflags = 0, index;
  95        struct tcf_skbmod *d;
  96        bool exists = false;
  97        u8 *daddr = NULL;
  98        u8 *saddr = NULL;
  99        u16 eth_type = 0;
 100        int ret = 0, err;
 101
 102        if (!nla)
 103                return -EINVAL;
 104
 105        err = nla_parse_nested_deprecated(tb, TCA_SKBMOD_MAX, nla,
 106                                          skbmod_policy, NULL);
 107        if (err < 0)
 108                return err;
 109
 110        if (!tb[TCA_SKBMOD_PARMS])
 111                return -EINVAL;
 112
 113        if (tb[TCA_SKBMOD_DMAC]) {
 114                daddr = nla_data(tb[TCA_SKBMOD_DMAC]);
 115                lflags |= SKBMOD_F_DMAC;
 116        }
 117
 118        if (tb[TCA_SKBMOD_SMAC]) {
 119                saddr = nla_data(tb[TCA_SKBMOD_SMAC]);
 120                lflags |= SKBMOD_F_SMAC;
 121        }
 122
 123        if (tb[TCA_SKBMOD_ETYPE]) {
 124                eth_type = nla_get_u16(tb[TCA_SKBMOD_ETYPE]);
 125                lflags |= SKBMOD_F_ETYPE;
 126        }
 127
 128        parm = nla_data(tb[TCA_SKBMOD_PARMS]);
 129        index = parm->index;
 130        if (parm->flags & SKBMOD_F_SWAPMAC)
 131                lflags = SKBMOD_F_SWAPMAC;
 132
 133        err = tcf_idr_check_alloc(tn, &index, a, bind);
 134        if (err < 0)
 135                return err;
 136        exists = err;
 137        if (exists && bind)
 138                return 0;
 139
 140        if (!lflags) {
 141                if (exists)
 142                        tcf_idr_release(*a, bind);
 143                else
 144                        tcf_idr_cleanup(tn, index);
 145                return -EINVAL;
 146        }
 147
 148        if (!exists) {
 149                ret = tcf_idr_create(tn, index, est, a,
 150                                     &act_skbmod_ops, bind, true, 0);
 151                if (ret) {
 152                        tcf_idr_cleanup(tn, index);
 153                        return ret;
 154                }
 155
 156                ret = ACT_P_CREATED;
 157        } else if (!ovr) {
 158                tcf_idr_release(*a, bind);
 159                return -EEXIST;
 160        }
 161        err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
 162        if (err < 0)
 163                goto release_idr;
 164
 165        d = to_skbmod(*a);
 166
 167        p = kzalloc(sizeof(struct tcf_skbmod_params), GFP_KERNEL);
 168        if (unlikely(!p)) {
 169                err = -ENOMEM;
 170                goto put_chain;
 171        }
 172
 173        p->flags = lflags;
 174
 175        if (ovr)
 176                spin_lock_bh(&d->tcf_lock);
 177        /* Protected by tcf_lock if overwriting existing action. */
 178        goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
 179        p_old = rcu_dereference_protected(d->skbmod_p, 1);
 180
 181        if (lflags & SKBMOD_F_DMAC)
 182                ether_addr_copy(p->eth_dst, daddr);
 183        if (lflags & SKBMOD_F_SMAC)
 184                ether_addr_copy(p->eth_src, saddr);
 185        if (lflags & SKBMOD_F_ETYPE)
 186                p->eth_type = htons(eth_type);
 187
 188        rcu_assign_pointer(d->skbmod_p, p);
 189        if (ovr)
 190                spin_unlock_bh(&d->tcf_lock);
 191
 192        if (p_old)
 193                kfree_rcu(p_old, rcu);
 194        if (goto_ch)
 195                tcf_chain_put_by_act(goto_ch);
 196
 197        return ret;
 198put_chain:
 199        if (goto_ch)
 200                tcf_chain_put_by_act(goto_ch);
 201release_idr:
 202        tcf_idr_release(*a, bind);
 203        return err;
 204}
 205
 206static void tcf_skbmod_cleanup(struct tc_action *a)
 207{
 208        struct tcf_skbmod *d = to_skbmod(a);
 209        struct tcf_skbmod_params  *p;
 210
 211        p = rcu_dereference_protected(d->skbmod_p, 1);
 212        if (p)
 213                kfree_rcu(p, rcu);
 214}
 215
 216static int tcf_skbmod_dump(struct sk_buff *skb, struct tc_action *a,
 217                           int bind, int ref)
 218{
 219        struct tcf_skbmod *d = to_skbmod(a);
 220        unsigned char *b = skb_tail_pointer(skb);
 221        struct tcf_skbmod_params  *p;
 222        struct tc_skbmod opt = {
 223                .index   = d->tcf_index,
 224                .refcnt  = refcount_read(&d->tcf_refcnt) - ref,
 225                .bindcnt = atomic_read(&d->tcf_bindcnt) - bind,
 226        };
 227        struct tcf_t t;
 228
 229        spin_lock_bh(&d->tcf_lock);
 230        opt.action = d->tcf_action;
 231        p = rcu_dereference_protected(d->skbmod_p,
 232                                      lockdep_is_held(&d->tcf_lock));
 233        opt.flags  = p->flags;
 234        if (nla_put(skb, TCA_SKBMOD_PARMS, sizeof(opt), &opt))
 235                goto nla_put_failure;
 236        if ((p->flags & SKBMOD_F_DMAC) &&
 237            nla_put(skb, TCA_SKBMOD_DMAC, ETH_ALEN, p->eth_dst))
 238                goto nla_put_failure;
 239        if ((p->flags & SKBMOD_F_SMAC) &&
 240            nla_put(skb, TCA_SKBMOD_SMAC, ETH_ALEN, p->eth_src))
 241                goto nla_put_failure;
 242        if ((p->flags & SKBMOD_F_ETYPE) &&
 243            nla_put_u16(skb, TCA_SKBMOD_ETYPE, ntohs(p->eth_type)))
 244                goto nla_put_failure;
 245
 246        tcf_tm_dump(&t, &d->tcf_tm);
 247        if (nla_put_64bit(skb, TCA_SKBMOD_TM, sizeof(t), &t, TCA_SKBMOD_PAD))
 248                goto nla_put_failure;
 249
 250        spin_unlock_bh(&d->tcf_lock);
 251        return skb->len;
 252nla_put_failure:
 253        spin_unlock_bh(&d->tcf_lock);
 254        nlmsg_trim(skb, b);
 255        return -1;
 256}
 257
 258static int tcf_skbmod_walker(struct net *net, struct sk_buff *skb,
 259                             struct netlink_callback *cb, int type,
 260                             const struct tc_action_ops *ops,
 261                             struct netlink_ext_ack *extack)
 262{
 263        struct tc_action_net *tn = net_generic(net, skbmod_net_id);
 264
 265        return tcf_generic_walker(tn, skb, cb, type, ops, extack);
 266}
 267
 268static int tcf_skbmod_search(struct net *net, struct tc_action **a, u32 index)
 269{
 270        struct tc_action_net *tn = net_generic(net, skbmod_net_id);
 271
 272        return tcf_idr_search(tn, a, index);
 273}
 274
 275static struct tc_action_ops act_skbmod_ops = {
 276        .kind           =       "skbmod",
 277        .id             =       TCA_ACT_SKBMOD,
 278        .owner          =       THIS_MODULE,
 279        .act            =       tcf_skbmod_act,
 280        .dump           =       tcf_skbmod_dump,
 281        .init           =       tcf_skbmod_init,
 282        .cleanup        =       tcf_skbmod_cleanup,
 283        .walk           =       tcf_skbmod_walker,
 284        .lookup         =       tcf_skbmod_search,
 285        .size           =       sizeof(struct tcf_skbmod),
 286};
 287
 288static __net_init int skbmod_init_net(struct net *net)
 289{
 290        struct tc_action_net *tn = net_generic(net, skbmod_net_id);
 291
 292        return tc_action_net_init(net, tn, &act_skbmod_ops);
 293}
 294
 295static void __net_exit skbmod_exit_net(struct list_head *net_list)
 296{
 297        tc_action_net_exit(net_list, skbmod_net_id);
 298}
 299
 300static struct pernet_operations skbmod_net_ops = {
 301        .init = skbmod_init_net,
 302        .exit_batch = skbmod_exit_net,
 303        .id   = &skbmod_net_id,
 304        .size = sizeof(struct tc_action_net),
 305};
 306
 307MODULE_AUTHOR("Jamal Hadi Salim, <jhs@mojatatu.com>");
 308MODULE_DESCRIPTION("SKB data mod-ing");
 309MODULE_LICENSE("GPL");
 310
 311static int __init skbmod_init_module(void)
 312{
 313        return tcf_register_action(&act_skbmod_ops, &skbmod_net_ops);
 314}
 315
 316static void __exit skbmod_cleanup_module(void)
 317{
 318        tcf_unregister_action(&act_skbmod_ops, &skbmod_net_ops);
 319}
 320
 321module_init(skbmod_init_module);
 322module_exit(skbmod_cleanup_module);
 323