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