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