net/sched/act_skbmod.c

   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
  21 static unsigned int skbmod_net_id;
  22 static struct tc_action_ops act_skbmod_ops;
  23
  24 #define MAX_EDIT_LEN ETH_HLEN
  25 static 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
  71 drop:
  72         qstats_overlimit_inc(this_cpu_ptr(d->common.cpu_qstats));
  73         return TC_ACT_SHOT;
  74 }
  75
  76 static 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
  83 static 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;
 198 put_chain:
 199         if (goto_ch)
 200                 tcf_chain_put_by_act(goto_ch);
 201 release_idr:
 202         tcf_idr_release(*a, bind);
 203         return err;
 204 }
 205
 206 static 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
 216 static 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;
 252 nla_put_failure:
 253         spin_unlock_bh(&d->tcf_lock);
 254         nlmsg_trim(skb, b);
 255         return -1;
 256 }
 257
 258 static 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
 268 static 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
 275 static 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
 288 static __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
 295 static void __net_exit skbmod_exit_net(struct list_head *net_list)
 296 {
 297         tc_action_net_exit(net_list, skbmod_net_id);
 298 }
 299
 300 static 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
 307 MODULE_AUTHOR("Jamal Hadi Salim, <jhs@mojatatu.com>");
 308 MODULE_DESCRIPTION("SKB data mod-ing");
 309 MODULE_LICENSE("GPL");
 310
 311 static int __init skbmod_init_module(void)
 312 {
 313         return tcf_register_action(&act_skbmod_ops, &skbmod_net_ops);
 314 }
 315
 316 static void __exit skbmod_cleanup_module(void)
 317 {
 318         tcf_unregister_action(&act_skbmod_ops, &skbmod_net_ops);
 319 }
 320
 321 module_init(skbmod_init_module);
 322 module_exit(skbmod_cleanup_module);