net/sched/act_skbmod.c

   1 /*
   2  * net/sched/act_skbmod.c  skb data modifier
   3  *
   4  * Copyright (c) 2016 Jamal Hadi Salim <jhs@mojatatu.com>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10 */
  11
  12 #include <linux/module.h>
  13 #include <linux/init.h>
  14 #include <linux/kernel.h>
  15 #include <linux/skbuff.h>
  16 #include <linux/rtnetlink.h>
  17 #include <net/netlink.h>
  18 #include <net/pkt_sched.h>
  19 #include <net/pkt_cls.h>
  20
  21 #include <linux/tc_act/tc_skbmod.h>
  22 #include <net/tc_act/tc_skbmod.h>
  23
  24 static unsigned int skbmod_net_id;
  25 static struct tc_action_ops act_skbmod_ops;
  26
  27 #define MAX_EDIT_LEN ETH_HLEN
  28 static int tcf_skbmod_act(struct sk_buff *skb, const struct tc_action *a,
  29                           struct tcf_result *res)
  30 {
  31         struct tcf_skbmod *d = to_skbmod(a);
  32         int action;
  33         struct tcf_skbmod_params *p;
  34         u64 flags;
  35         int err;
  36
  37         tcf_lastuse_update(&d->tcf_tm);
  38         bstats_cpu_update(this_cpu_ptr(d->common.cpu_bstats), skb);
  39
  40         /* XXX: if you are going to edit more fields beyond ethernet header
  41          * (example when you add IP header replacement or vlan swap)
  42          * then MAX_EDIT_LEN needs to change appropriately
  43         */
  44         err = skb_ensure_writable(skb, MAX_EDIT_LEN);
  45         if (unlikely(err)) /* best policy is to drop on the floor */
  46                 goto drop;
  47
  48         action = READ_ONCE(d->tcf_action);
  49         if (unlikely(action == TC_ACT_SHOT))
  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,
  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         struct tcf_skbmod *d;
  95         bool exists = false;
  96         u8 *daddr = NULL;
  97         u8 *saddr = NULL;
  98         u16 eth_type = 0;
  99         u32 lflags = 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         if (parm->flags & SKBMOD_F_SWAPMAC)
 130                 lflags = SKBMOD_F_SWAPMAC;
 131
 132         err = tcf_idr_check_alloc(tn, &parm->index, a, bind);
 133         if (err < 0)
 134                 return err;
 135         exists = err;
 136         if (exists && bind)
 137                 return 0;
 138
 139         if (!lflags) {
 140                 if (exists)
 141                         tcf_idr_release(*a, bind);
 142                 else
 143                         tcf_idr_cleanup(tn, parm->index);
 144                 return -EINVAL;
 145         }
 146
 147         if (!exists) {
 148                 ret = tcf_idr_create(tn, parm->index, est, a,
 149                                      &act_skbmod_ops, bind, true);
 150                 if (ret) {
 151                         tcf_idr_cleanup(tn, parm->index);
 152                         return ret;
 153                 }
 154
 155                 ret = ACT_P_CREATED;
 156         } else if (!ovr) {
 157                 tcf_idr_release(*a, bind);
 158                 return -EEXIST;
 159         }
 160         err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
 161         if (err < 0)
 162                 goto release_idr;
 163
 164         d = to_skbmod(*a);
 165
 166         p = kzalloc(sizeof(struct tcf_skbmod_params), GFP_KERNEL);
 167         if (unlikely(!p)) {
 168                 err = -ENOMEM;
 169                 goto put_chain;
 170         }
 171
 172         p->flags = lflags;
 173
 174         if (ovr)
 175                 spin_lock_bh(&d->tcf_lock);
 176         /* Protected by tcf_lock if overwriting existing action. */
 177         goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
 178         p_old = rcu_dereference_protected(d->skbmod_p, 1);
 179
 180         if (lflags & SKBMOD_F_DMAC)
 181                 ether_addr_copy(p->eth_dst, daddr);
 182         if (lflags & SKBMOD_F_SMAC)
 183                 ether_addr_copy(p->eth_src, saddr);
 184         if (lflags & SKBMOD_F_ETYPE)
 185                 p->eth_type = htons(eth_type);
 186
 187         rcu_assign_pointer(d->skbmod_p, p);
 188         if (ovr)
 189                 spin_unlock_bh(&d->tcf_lock);
 190
 191         if (p_old)
 192                 kfree_rcu(p_old, rcu);
 193         if (goto_ch)
 194                 tcf_chain_put_by_act(goto_ch);
 195
 196         if (ret == ACT_P_CREATED)
 197                 tcf_idr_insert(tn, *a);
 198         return ret;
 199 put_chain:
 200         if (goto_ch)
 201                 tcf_chain_put_by_act(goto_ch);
 202 release_idr:
 203         tcf_idr_release(*a, bind);
 204         return err;
 205 }
 206
 207 static void tcf_skbmod_cleanup(struct tc_action *a)
 208 {
 209         struct tcf_skbmod *d = to_skbmod(a);
 210         struct tcf_skbmod_params  *p;
 211
 212         p = rcu_dereference_protected(d->skbmod_p, 1);
 213         if (p)
 214                 kfree_rcu(p, rcu);
 215 }
 216
 217 static int tcf_skbmod_dump(struct sk_buff *skb, struct tc_action *a,
 218                            int bind, int ref)
 219 {
 220         struct tcf_skbmod *d = to_skbmod(a);
 221         unsigned char *b = skb_tail_pointer(skb);
 222         struct tcf_skbmod_params  *p;
 223         struct tc_skbmod opt = {
 224                 .index   = d->tcf_index,
 225                 .refcnt  = refcount_read(&d->tcf_refcnt) - ref,
 226                 .bindcnt = atomic_read(&d->tcf_bindcnt) - bind,
 227         };
 228         struct tcf_t t;
 229
 230         spin_lock_bh(&d->tcf_lock);
 231         opt.action = d->tcf_action;
 232         p = rcu_dereference_protected(d->skbmod_p,
 233                                       lockdep_is_held(&d->tcf_lock));
 234         opt.flags  = p->flags;
 235         if (nla_put(skb, TCA_SKBMOD_PARMS, sizeof(opt), &opt))
 236                 goto nla_put_failure;
 237         if ((p->flags & SKBMOD_F_DMAC) &&
 238             nla_put(skb, TCA_SKBMOD_DMAC, ETH_ALEN, p->eth_dst))
 239                 goto nla_put_failure;
 240         if ((p->flags & SKBMOD_F_SMAC) &&
 241             nla_put(skb, TCA_SKBMOD_SMAC, ETH_ALEN, p->eth_src))
 242                 goto nla_put_failure;
 243         if ((p->flags & SKBMOD_F_ETYPE) &&
 244             nla_put_u16(skb, TCA_SKBMOD_ETYPE, ntohs(p->eth_type)))
 245                 goto nla_put_failure;
 246
 247         tcf_tm_dump(&t, &d->tcf_tm);
 248         if (nla_put_64bit(skb, TCA_SKBMOD_TM, sizeof(t), &t, TCA_SKBMOD_PAD))
 249                 goto nla_put_failure;
 250
 251         spin_unlock_bh(&d->tcf_lock);
 252         return skb->len;
 253 nla_put_failure:
 254         spin_unlock_bh(&d->tcf_lock);
 255         nlmsg_trim(skb, b);
 256         return -1;
 257 }
 258
 259 static int tcf_skbmod_walker(struct net *net, struct sk_buff *skb,
 260                              struct netlink_callback *cb, int type,
 261                              const struct tc_action_ops *ops,
 262                              struct netlink_ext_ack *extack)
 263 {
 264         struct tc_action_net *tn = net_generic(net, skbmod_net_id);
 265
 266         return tcf_generic_walker(tn, skb, cb, type, ops, extack);
 267 }
 268
 269 static int tcf_skbmod_search(struct net *net, struct tc_action **a, u32 index)
 270 {
 271         struct tc_action_net *tn = net_generic(net, skbmod_net_id);
 272
 273         return tcf_idr_search(tn, a, index);
 274 }
 275
 276 static struct tc_action_ops act_skbmod_ops = {
 277         .kind           =       "skbmod",
 278         .id             =       TCA_ACT_SKBMOD,
 279         .owner          =       THIS_MODULE,
 280         .act            =       tcf_skbmod_act,
 281         .dump           =       tcf_skbmod_dump,
 282         .init           =       tcf_skbmod_init,
 283         .cleanup        =       tcf_skbmod_cleanup,
 284         .walk           =       tcf_skbmod_walker,
 285         .lookup         =       tcf_skbmod_search,
 286         .size           =       sizeof(struct tcf_skbmod),
 287 };
 288
 289 static __net_init int skbmod_init_net(struct net *net)
 290 {
 291         struct tc_action_net *tn = net_generic(net, skbmod_net_id);
 292
 293         return tc_action_net_init(tn, &act_skbmod_ops);
 294 }
 295
 296 static void __net_exit skbmod_exit_net(struct list_head *net_list)
 297 {
 298         tc_action_net_exit(net_list, skbmod_net_id);
 299 }
 300
 301 static struct pernet_operations skbmod_net_ops = {
 302         .init = skbmod_init_net,
 303         .exit_batch = skbmod_exit_net,
 304         .id   = &skbmod_net_id,
 305         .size = sizeof(struct tc_action_net),
 306 };
 307
 308 MODULE_AUTHOR("Jamal Hadi Salim, <jhs@mojatatu.com>");
 309 MODULE_DESCRIPTION("SKB data mod-ing");
 310 MODULE_LICENSE("GPL");
 311
 312 static int __init skbmod_init_module(void)
 313 {
 314         return tcf_register_action(&act_skbmod_ops, &skbmod_net_ops);
 315 }
 316
 317 static void __exit skbmod_cleanup_module(void)
 318 {
 319         tcf_unregister_action(&act_skbmod_ops, &skbmod_net_ops);
 320 }
 321
 322 module_init(skbmod_init_module);
 323 module_exit(skbmod_cleanup_module);