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         u32 lflags = 0, index;
  91         struct tcf_skbmod *d;
  92         bool exists = false;
  93         u8 *daddr = NULL;
  94         u8 *saddr = NULL;
  95         u16 eth_type = 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         index = parm->index;
 126         if (parm->flags & SKBMOD_F_SWAPMAC)
 127                 lflags = SKBMOD_F_SWAPMAC;
 128
 129         err = tcf_idr_check_alloc(tn, &index, a, bind);
 130         if (err < 0)
 131                 return err;
 132         exists = err;
 133         if (exists && bind)
 134                 return 0;
 135
 136         if (!lflags) {
 137                 if (exists)
 138                         tcf_idr_release(*a, bind);
 139                 else
 140                         tcf_idr_cleanup(tn, index);
 141                 return -EINVAL;
 142         }
 143
 144         if (!exists) {
 145                 ret = tcf_idr_create(tn, index, est, a,
 146                                      &act_skbmod_ops, bind, true);
 147                 if (ret) {
 148                         tcf_idr_cleanup(tn, index);
 149                         return ret;
 150                 }
 151
 152                 ret = ACT_P_CREATED;
 153         } else if (!ovr) {
 154                 tcf_idr_release(*a, bind);
 155                 return -EEXIST;
 156         }
 157         err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
 158         if (err < 0)
 159                 goto release_idr;
 160
 161         d = to_skbmod(*a);
 162
 163         p = kzalloc(sizeof(struct tcf_skbmod_params), GFP_KERNEL);
 164         if (unlikely(!p)) {
 165                 err = -ENOMEM;
 166                 goto put_chain;
 167         }
 168
 169         p->flags = lflags;
 170
 171         if (ovr)
 172                 spin_lock_bh(&d->tcf_lock);
 173         /* Protected by tcf_lock if overwriting existing action. */
 174         goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
 175         p_old = rcu_dereference_protected(d->skbmod_p, 1);
 176
 177         if (lflags & SKBMOD_F_DMAC)
 178                 ether_addr_copy(p->eth_dst, daddr);
 179         if (lflags & SKBMOD_F_SMAC)
 180                 ether_addr_copy(p->eth_src, saddr);
 181         if (lflags & SKBMOD_F_ETYPE)
 182                 p->eth_type = htons(eth_type);
 183
 184         rcu_assign_pointer(d->skbmod_p, p);
 185         if (ovr)
 186                 spin_unlock_bh(&d->tcf_lock);
 187
 188         if (p_old)
 189                 kfree_rcu(p_old, rcu);
 190         if (goto_ch)
 191                 tcf_chain_put_by_act(goto_ch);
 192
 193         if (ret == ACT_P_CREATED)
 194                 tcf_idr_insert(tn, *a);
 195         return ret;
 196 put_chain:
 197         if (goto_ch)
 198                 tcf_chain_put_by_act(goto_ch);
 199 release_idr:
 200         tcf_idr_release(*a, bind);
 201         return err;
 202 }
 203
 204 static void tcf_skbmod_cleanup(struct tc_action *a)
 205 {
 206         struct tcf_skbmod *d = to_skbmod(a);
 207         struct tcf_skbmod_params  *p;
 208
 209         p = rcu_dereference_protected(d->skbmod_p, 1);
 210         if (p)
 211                 kfree_rcu(p, rcu);
 212 }
 213
 214 static int tcf_skbmod_dump(struct sk_buff *skb, struct tc_action *a,
 215                            int bind, int ref)
 216 {
 217         struct tcf_skbmod *d = to_skbmod(a);
 218         unsigned char *b = skb_tail_pointer(skb);
 219         struct tcf_skbmod_params  *p;
 220         struct tc_skbmod opt = {
 221                 .index   = d->tcf_index,
 222                 .refcnt  = refcount_read(&d->tcf_refcnt) - ref,
 223                 .bindcnt = atomic_read(&d->tcf_bindcnt) - bind,
 224         };
 225         struct tcf_t t;
 226
 227         spin_lock_bh(&d->tcf_lock);
 228         opt.action = d->tcf_action;
 229         p = rcu_dereference_protected(d->skbmod_p,
 230                                       lockdep_is_held(&d->tcf_lock));
 231         opt.flags  = p->flags;
 232         if (nla_put(skb, TCA_SKBMOD_PARMS, sizeof(opt), &opt))
 233                 goto nla_put_failure;
 234         if ((p->flags & SKBMOD_F_DMAC) &&
 235             nla_put(skb, TCA_SKBMOD_DMAC, ETH_ALEN, p->eth_dst))
 236                 goto nla_put_failure;
 237         if ((p->flags & SKBMOD_F_SMAC) &&
 238             nla_put(skb, TCA_SKBMOD_SMAC, ETH_ALEN, p->eth_src))
 239                 goto nla_put_failure;
 240         if ((p->flags & SKBMOD_F_ETYPE) &&
 241             nla_put_u16(skb, TCA_SKBMOD_ETYPE, ntohs(p->eth_type)))
 242                 goto nla_put_failure;
 243
 244         tcf_tm_dump(&t, &d->tcf_tm);
 245         if (nla_put_64bit(skb, TCA_SKBMOD_TM, sizeof(t), &t, TCA_SKBMOD_PAD))
 246                 goto nla_put_failure;
 247
 248         spin_unlock_bh(&d->tcf_lock);
 249         return skb->len;
 250 nla_put_failure:
 251         spin_unlock_bh(&d->tcf_lock);
 252         nlmsg_trim(skb, b);
 253         return -1;
 254 }
 255
 256 static int tcf_skbmod_walker(struct net *net, struct sk_buff *skb,
 257                              struct netlink_callback *cb, int type,
 258                              const struct tc_action_ops *ops,
 259                              struct netlink_ext_ack *extack)
 260 {
 261         struct tc_action_net *tn = net_generic(net, skbmod_net_id);
 262
 263         return tcf_generic_walker(tn, skb, cb, type, ops, extack);
 264 }
 265
 266 static int tcf_skbmod_search(struct net *net, struct tc_action **a, u32 index)
 267 {
 268         struct tc_action_net *tn = net_generic(net, skbmod_net_id);
 269
 270         return tcf_idr_search(tn, a, index);
 271 }
 272
 273 static struct tc_action_ops act_skbmod_ops = {
 274         .kind           =       "skbmod",
 275         .id             =       TCA_ACT_SKBMOD,
 276         .owner          =       THIS_MODULE,
 277         .act            =       tcf_skbmod_act,
 278         .dump           =       tcf_skbmod_dump,
 279         .init           =       tcf_skbmod_init,
 280         .cleanup        =       tcf_skbmod_cleanup,
 281         .walk           =       tcf_skbmod_walker,
 282         .lookup         =       tcf_skbmod_search,
 283         .size           =       sizeof(struct tcf_skbmod),
 284 };
 285
 286 static __net_init int skbmod_init_net(struct net *net)
 287 {
 288         struct tc_action_net *tn = net_generic(net, skbmod_net_id);
 289
 290         return tc_action_net_init(tn, &act_skbmod_ops);
 291 }
 292
 293 static void __net_exit skbmod_exit_net(struct list_head *net_list)
 294 {
 295         tc_action_net_exit(net_list, skbmod_net_id);
 296 }
 297
 298 static struct pernet_operations skbmod_net_ops = {
 299         .init = skbmod_init_net,
 300         .exit_batch = skbmod_exit_net,
 301         .id   = &skbmod_net_id,
 302         .size = sizeof(struct tc_action_net),
 303 };
 304
 305 MODULE_AUTHOR("Jamal Hadi Salim, <jhs@mojatatu.com>");
 306 MODULE_DESCRIPTION("SKB data mod-ing");
 307 MODULE_LICENSE("GPL");
 308
 309 static int __init skbmod_init_module(void)
 310 {
 311         return tcf_register_action(&act_skbmod_ops, &skbmod_net_ops);
 312 }
 313
 314 static void __exit skbmod_cleanup_module(void)
 315 {
 316         tcf_unregister_action(&act_skbmod_ops, &skbmod_net_ops);
 317 }
 318
 319 module_init(skbmod_init_module);
 320 module_exit(skbmod_cleanup_module);