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