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/inet_ecn.h>
  15 #include <net/netlink.h>
  16 #include <net/pkt_sched.h>
  17 #include <net/pkt_cls.h>
  18
  19 #include <linux/tc_act/tc_skbmod.h>
  20 #include <net/tc_act/tc_skbmod.h>
  21
  22 static unsigned int skbmod_net_id;
  23 static struct tc_action_ops act_skbmod_ops;
  24
  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, max_edit_len, err;
  30         struct tcf_skbmod_params *p;
  31         u64 flags;
  32
  33         tcf_lastuse_update(&d->tcf_tm);
  34         bstats_cpu_update(this_cpu_ptr(d->common.cpu_bstats), skb);
  35
  36         action = READ_ONCE(d->tcf_action);
  37         if (unlikely(action == TC_ACT_SHOT))
  38                 goto drop;
  39
  40         max_edit_len = skb_mac_header_len(skb);
  41         p = rcu_dereference_bh(d->skbmod_p);
  42         flags = p->flags;
  43
  44         /* tcf_skbmod_init() guarantees "flags" to be one of the following:
  45          *      1. a combination of SKBMOD_F_{DMAC,SMAC,ETYPE}
  46          *      2. SKBMOD_F_SWAPMAC
  47          *      3. SKBMOD_F_ECN
  48          * SKBMOD_F_ECN only works with IP packets; all other flags only work with Ethernet
  49          * packets.
  50          */
  51         if (flags == SKBMOD_F_ECN) {
  52                 switch (skb_protocol(skb, true)) {
  53                 case cpu_to_be16(ETH_P_IP):
  54                 case cpu_to_be16(ETH_P_IPV6):
  55                         max_edit_len += skb_network_header_len(skb);
  56                         break;
  57                 default:
  58                         goto out;
  59                 }
  60         } else if (!skb->dev || skb->dev->type != ARPHRD_ETHER) {
  61                 goto out;
  62         }
  63
  64         err = skb_ensure_writable(skb, max_edit_len);
  65         if (unlikely(err)) /* best policy is to drop on the floor */
  66                 goto drop;
  67
  68         if (flags & SKBMOD_F_DMAC)
  69                 ether_addr_copy(eth_hdr(skb)->h_dest, p->eth_dst);
  70         if (flags & SKBMOD_F_SMAC)
  71                 ether_addr_copy(eth_hdr(skb)->h_source, p->eth_src);
  72         if (flags & SKBMOD_F_ETYPE)
  73                 eth_hdr(skb)->h_proto = p->eth_type;
  74
  75         if (flags & SKBMOD_F_SWAPMAC) {
  76                 u16 tmpaddr[ETH_ALEN / 2]; /* ether_addr_copy() requirement */
  77                 /*XXX: I am sure we can come up with more efficient swapping*/
  78                 ether_addr_copy((u8 *)tmpaddr, eth_hdr(skb)->h_dest);
  79                 ether_addr_copy(eth_hdr(skb)->h_dest, eth_hdr(skb)->h_source);
  80                 ether_addr_copy(eth_hdr(skb)->h_source, (u8 *)tmpaddr);
  81         }
  82
  83         if (flags & SKBMOD_F_ECN)
  84                 INET_ECN_set_ce(skb);
  85
  86 out:
  87         return action;
  88
  89 drop:
  90         qstats_overlimit_inc(this_cpu_ptr(d->common.cpu_qstats));
  91         return TC_ACT_SHOT;
  92 }
  93
  94 static const struct nla_policy skbmod_policy[TCA_SKBMOD_MAX + 1] = {
  95         [TCA_SKBMOD_PARMS]              = { .len = sizeof(struct tc_skbmod) },
  96         [TCA_SKBMOD_DMAC]               = { .len = ETH_ALEN },
  97         [TCA_SKBMOD_SMAC]               = { .len = ETH_ALEN },
  98         [TCA_SKBMOD_ETYPE]              = { .type = NLA_U16 },
  99 };
 100
 101 static int tcf_skbmod_init(struct net *net, struct nlattr *nla,
 102                            struct nlattr *est, struct tc_action **a,
 103                            struct tcf_proto *tp, u32 flags,
 104                            struct netlink_ext_ack *extack)
 105 {
 106         struct tc_action_net *tn = net_generic(net, skbmod_net_id);
 107         bool ovr = flags & TCA_ACT_FLAGS_REPLACE;
 108         bool bind = flags & TCA_ACT_FLAGS_BIND;
 109         struct nlattr *tb[TCA_SKBMOD_MAX + 1];
 110         struct tcf_skbmod_params *p, *p_old;
 111         struct tcf_chain *goto_ch = NULL;
 112         struct tc_skbmod *parm;
 113         u32 lflags = 0, index;
 114         struct tcf_skbmod *d;
 115         bool exists = false;
 116         u8 *daddr = NULL;
 117         u8 *saddr = NULL;
 118         u16 eth_type = 0;
 119         int ret = 0, err;
 120
 121         if (!nla)
 122                 return -EINVAL;
 123
 124         err = nla_parse_nested_deprecated(tb, TCA_SKBMOD_MAX, nla,
 125                                           skbmod_policy, NULL);
 126         if (err < 0)
 127                 return err;
 128
 129         if (!tb[TCA_SKBMOD_PARMS])
 130                 return -EINVAL;
 131
 132         if (tb[TCA_SKBMOD_DMAC]) {
 133                 daddr = nla_data(tb[TCA_SKBMOD_DMAC]);
 134                 lflags |= SKBMOD_F_DMAC;
 135         }
 136
 137         if (tb[TCA_SKBMOD_SMAC]) {
 138                 saddr = nla_data(tb[TCA_SKBMOD_SMAC]);
 139                 lflags |= SKBMOD_F_SMAC;
 140         }
 141
 142         if (tb[TCA_SKBMOD_ETYPE]) {
 143                 eth_type = nla_get_u16(tb[TCA_SKBMOD_ETYPE]);
 144                 lflags |= SKBMOD_F_ETYPE;
 145         }
 146
 147         parm = nla_data(tb[TCA_SKBMOD_PARMS]);
 148         index = parm->index;
 149         if (parm->flags & SKBMOD_F_SWAPMAC)
 150                 lflags = SKBMOD_F_SWAPMAC;
 151         if (parm->flags & SKBMOD_F_ECN)
 152                 lflags = SKBMOD_F_ECN;
 153
 154         err = tcf_idr_check_alloc(tn, &index, a, bind);
 155         if (err < 0)
 156                 return err;
 157         exists = err;
 158         if (exists && bind)
 159                 return 0;
 160
 161         if (!lflags) {
 162                 if (exists)
 163                         tcf_idr_release(*a, bind);
 164                 else
 165                         tcf_idr_cleanup(tn, index);
 166                 return -EINVAL;
 167         }
 168
 169         if (!exists) {
 170                 ret = tcf_idr_create(tn, index, est, a,
 171                                      &act_skbmod_ops, bind, true, 0);
 172                 if (ret) {
 173                         tcf_idr_cleanup(tn, index);
 174                         return ret;
 175                 }
 176
 177                 ret = ACT_P_CREATED;
 178         } else if (!ovr) {
 179                 tcf_idr_release(*a, bind);
 180                 return -EEXIST;
 181         }
 182         err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
 183         if (err < 0)
 184                 goto release_idr;
 185
 186         d = to_skbmod(*a);
 187
 188         p = kzalloc(sizeof(struct tcf_skbmod_params), GFP_KERNEL);
 189         if (unlikely(!p)) {
 190                 err = -ENOMEM;
 191                 goto put_chain;
 192         }
 193
 194         p->flags = lflags;
 195
 196         if (ovr)
 197                 spin_lock_bh(&d->tcf_lock);
 198         /* Protected by tcf_lock if overwriting existing action. */
 199         goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
 200         p_old = rcu_dereference_protected(d->skbmod_p, 1);
 201
 202         if (lflags & SKBMOD_F_DMAC)
 203                 ether_addr_copy(p->eth_dst, daddr);
 204         if (lflags & SKBMOD_F_SMAC)
 205                 ether_addr_copy(p->eth_src, saddr);
 206         if (lflags & SKBMOD_F_ETYPE)
 207                 p->eth_type = htons(eth_type);
 208
 209         rcu_assign_pointer(d->skbmod_p, p);
 210         if (ovr)
 211                 spin_unlock_bh(&d->tcf_lock);
 212
 213         if (p_old)
 214                 kfree_rcu(p_old, rcu);
 215         if (goto_ch)
 216                 tcf_chain_put_by_act(goto_ch);
 217
 218         return ret;
 219 put_chain:
 220         if (goto_ch)
 221                 tcf_chain_put_by_act(goto_ch);
 222 release_idr:
 223         tcf_idr_release(*a, bind);
 224         return err;
 225 }
 226
 227 static void tcf_skbmod_cleanup(struct tc_action *a)
 228 {
 229         struct tcf_skbmod *d = to_skbmod(a);
 230         struct tcf_skbmod_params  *p;
 231
 232         p = rcu_dereference_protected(d->skbmod_p, 1);
 233         if (p)
 234                 kfree_rcu(p, rcu);
 235 }
 236
 237 static int tcf_skbmod_dump(struct sk_buff *skb, struct tc_action *a,
 238                            int bind, int ref)
 239 {
 240         struct tcf_skbmod *d = to_skbmod(a);
 241         unsigned char *b = skb_tail_pointer(skb);
 242         struct tcf_skbmod_params  *p;
 243         struct tc_skbmod opt = {
 244                 .index   = d->tcf_index,
 245                 .refcnt  = refcount_read(&d->tcf_refcnt) - ref,
 246                 .bindcnt = atomic_read(&d->tcf_bindcnt) - bind,
 247         };
 248         struct tcf_t t;
 249
 250         spin_lock_bh(&d->tcf_lock);
 251         opt.action = d->tcf_action;
 252         p = rcu_dereference_protected(d->skbmod_p,
 253                                       lockdep_is_held(&d->tcf_lock));
 254         opt.flags  = p->flags;
 255         if (nla_put(skb, TCA_SKBMOD_PARMS, sizeof(opt), &opt))
 256                 goto nla_put_failure;
 257         if ((p->flags & SKBMOD_F_DMAC) &&
 258             nla_put(skb, TCA_SKBMOD_DMAC, ETH_ALEN, p->eth_dst))
 259                 goto nla_put_failure;
 260         if ((p->flags & SKBMOD_F_SMAC) &&
 261             nla_put(skb, TCA_SKBMOD_SMAC, ETH_ALEN, p->eth_src))
 262                 goto nla_put_failure;
 263         if ((p->flags & SKBMOD_F_ETYPE) &&
 264             nla_put_u16(skb, TCA_SKBMOD_ETYPE, ntohs(p->eth_type)))
 265                 goto nla_put_failure;
 266
 267         tcf_tm_dump(&t, &d->tcf_tm);
 268         if (nla_put_64bit(skb, TCA_SKBMOD_TM, sizeof(t), &t, TCA_SKBMOD_PAD))
 269                 goto nla_put_failure;
 270
 271         spin_unlock_bh(&d->tcf_lock);
 272         return skb->len;
 273 nla_put_failure:
 274         spin_unlock_bh(&d->tcf_lock);
 275         nlmsg_trim(skb, b);
 276         return -1;
 277 }
 278
 279 static int tcf_skbmod_walker(struct net *net, struct sk_buff *skb,
 280                              struct netlink_callback *cb, int type,
 281                              const struct tc_action_ops *ops,
 282                              struct netlink_ext_ack *extack)
 283 {
 284         struct tc_action_net *tn = net_generic(net, skbmod_net_id);
 285
 286         return tcf_generic_walker(tn, skb, cb, type, ops, extack);
 287 }
 288
 289 static int tcf_skbmod_search(struct net *net, struct tc_action **a, u32 index)
 290 {
 291         struct tc_action_net *tn = net_generic(net, skbmod_net_id);
 292
 293         return tcf_idr_search(tn, a, index);
 294 }
 295
 296 static struct tc_action_ops act_skbmod_ops = {
 297         .kind           =       "skbmod",
 298         .id             =       TCA_ACT_SKBMOD,
 299         .owner          =       THIS_MODULE,
 300         .act            =       tcf_skbmod_act,
 301         .dump           =       tcf_skbmod_dump,
 302         .init           =       tcf_skbmod_init,
 303         .cleanup        =       tcf_skbmod_cleanup,
 304         .walk           =       tcf_skbmod_walker,
 305         .lookup         =       tcf_skbmod_search,
 306         .size           =       sizeof(struct tcf_skbmod),
 307 };
 308
 309 static __net_init int skbmod_init_net(struct net *net)
 310 {
 311         struct tc_action_net *tn = net_generic(net, skbmod_net_id);
 312
 313         return tc_action_net_init(net, tn, &act_skbmod_ops);
 314 }
 315
 316 static void __net_exit skbmod_exit_net(struct list_head *net_list)
 317 {
 318         tc_action_net_exit(net_list, skbmod_net_id);
 319 }
 320
 321 static struct pernet_operations skbmod_net_ops = {
 322         .init = skbmod_init_net,
 323         .exit_batch = skbmod_exit_net,
 324         .id   = &skbmod_net_id,
 325         .size = sizeof(struct tc_action_net),
 326 };
 327
 328 MODULE_AUTHOR("Jamal Hadi Salim, <jhs@mojatatu.com>");
 329 MODULE_DESCRIPTION("SKB data mod-ing");
 330 MODULE_LICENSE("GPL");
 331
 332 static int __init skbmod_init_module(void)
 333 {
 334         return tcf_register_action(&act_skbmod_ops, &skbmod_net_ops);
 335 }
 336
 337 static void __exit skbmod_cleanup_module(void)
 338 {
 339         tcf_unregister_action(&act_skbmod_ops, &skbmod_net_ops);
 340 }
 341
 342 module_init(skbmod_init_module);
 343 module_exit(skbmod_cleanup_module);