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_run(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                 qstats_overlimit_inc(this_cpu_ptr(d->common.cpu_qstats));
  46                 return TC_ACT_SHOT;
  47         }
  48
  49         rcu_read_lock();
  50         action = READ_ONCE(d->tcf_action);
  51         if (unlikely(action == TC_ACT_SHOT)) {
  52                 qstats_overlimit_inc(this_cpu_ptr(d->common.cpu_qstats));
  53                 rcu_read_unlock();
  54                 return action;
  55         }
  56
  57         p = rcu_dereference(d->skbmod_p);
  58         flags = p->flags;
  59         if (flags & SKBMOD_F_DMAC)
  60                 ether_addr_copy(eth_hdr(skb)->h_dest, p->eth_dst);
  61         if (flags & SKBMOD_F_SMAC)
  62                 ether_addr_copy(eth_hdr(skb)->h_source, p->eth_src);
  63         if (flags & SKBMOD_F_ETYPE)
  64                 eth_hdr(skb)->h_proto = p->eth_type;
  65         rcu_read_unlock();
  66
  67         if (flags & SKBMOD_F_SWAPMAC) {
  68                 u16 tmpaddr[ETH_ALEN / 2]; /* ether_addr_copy() requirement */
  69                 /*XXX: I am sure we can come up with more efficient swapping*/
  70                 ether_addr_copy((u8 *)tmpaddr, eth_hdr(skb)->h_dest);
  71                 ether_addr_copy(eth_hdr(skb)->h_dest, eth_hdr(skb)->h_source);
  72                 ether_addr_copy(eth_hdr(skb)->h_source, (u8 *)tmpaddr);
  73         }
  74
  75         return action;
  76 }
  77
  78 static const struct nla_policy skbmod_policy[TCA_SKBMOD_MAX + 1] = {
  79         [TCA_SKBMOD_PARMS]              = { .len = sizeof(struct tc_skbmod) },
  80         [TCA_SKBMOD_DMAC]               = { .len = ETH_ALEN },
  81         [TCA_SKBMOD_SMAC]               = { .len = ETH_ALEN },
  82         [TCA_SKBMOD_ETYPE]              = { .type = NLA_U16 },
  83 };
  84
  85 static int tcf_skbmod_init(struct net *net, struct nlattr *nla,
  86                            struct nlattr *est, struct tc_action **a,
  87                            int ovr, int bind)
  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 tc_skbmod *parm;
  93         struct tcf_skbmod *d;
  94         bool exists = false;
  95         u8 *daddr = NULL;
  96         u8 *saddr = NULL;
  97         u16 eth_type = 0;
  98         u32 lflags = 0;
  99         int ret = 0, err;
 100
 101         if (!nla)
 102                 return -EINVAL;
 103
 104         err = nla_parse_nested(tb, TCA_SKBMOD_MAX, nla, skbmod_policy, NULL);
 105         if (err < 0)
 106                 return err;
 107
 108         if (!tb[TCA_SKBMOD_PARMS])
 109                 return -EINVAL;
 110
 111         if (tb[TCA_SKBMOD_DMAC]) {
 112                 daddr = nla_data(tb[TCA_SKBMOD_DMAC]);
 113                 lflags |= SKBMOD_F_DMAC;
 114         }
 115
 116         if (tb[TCA_SKBMOD_SMAC]) {
 117                 saddr = nla_data(tb[TCA_SKBMOD_SMAC]);
 118                 lflags |= SKBMOD_F_SMAC;
 119         }
 120
 121         if (tb[TCA_SKBMOD_ETYPE]) {
 122                 eth_type = nla_get_u16(tb[TCA_SKBMOD_ETYPE]);
 123                 lflags |= SKBMOD_F_ETYPE;
 124         }
 125
 126         parm = nla_data(tb[TCA_SKBMOD_PARMS]);
 127         if (parm->flags & SKBMOD_F_SWAPMAC)
 128                 lflags = SKBMOD_F_SWAPMAC;
 129
 130         exists = tcf_idr_check(tn, parm->index, a, bind);
 131         if (exists && bind)
 132                 return 0;
 133
 134         if (!lflags) {
 135                 if (exists)
 136                         tcf_idr_release(*a, bind);
 137                 return -EINVAL;
 138         }
 139
 140         if (!exists) {
 141                 ret = tcf_idr_create(tn, parm->index, est, a,
 142                                      &act_skbmod_ops, bind, true);
 143                 if (ret)
 144                         return ret;
 145
 146                 ret = ACT_P_CREATED;
 147         } else {
 148                 tcf_idr_release(*a, bind);
 149                 if (!ovr)
 150                         return -EEXIST;
 151         }
 152
 153         d = to_skbmod(*a);
 154
 155         ASSERT_RTNL();
 156         p = kzalloc(sizeof(struct tcf_skbmod_params), GFP_KERNEL);
 157         if (unlikely(!p)) {
 158                 if (ret == ACT_P_CREATED)
 159                         tcf_idr_release(*a, bind);
 160                 return -ENOMEM;
 161         }
 162
 163         p->flags = lflags;
 164         d->tcf_action = parm->action;
 165
 166         p_old = rtnl_dereference(d->skbmod_p);
 167
 168         if (ovr)
 169                 spin_lock_bh(&d->tcf_lock);
 170
 171         if (lflags & SKBMOD_F_DMAC)
 172                 ether_addr_copy(p->eth_dst, daddr);
 173         if (lflags & SKBMOD_F_SMAC)
 174                 ether_addr_copy(p->eth_src, saddr);
 175         if (lflags & SKBMOD_F_ETYPE)
 176                 p->eth_type = htons(eth_type);
 177
 178         rcu_assign_pointer(d->skbmod_p, p);
 179         if (ovr)
 180                 spin_unlock_bh(&d->tcf_lock);
 181
 182         if (p_old)
 183                 kfree_rcu(p_old, rcu);
 184
 185         if (ret == ACT_P_CREATED)
 186                 tcf_idr_insert(tn, *a);
 187         return ret;
 188 }
 189
 190 static void tcf_skbmod_cleanup(struct tc_action *a)
 191 {
 192         struct tcf_skbmod *d = to_skbmod(a);
 193         struct tcf_skbmod_params  *p;
 194
 195         p = rcu_dereference_protected(d->skbmod_p, 1);
 196         if (p)
 197                 kfree_rcu(p, rcu);
 198 }
 199
 200 static int tcf_skbmod_dump(struct sk_buff *skb, struct tc_action *a,
 201                            int bind, int ref)
 202 {
 203         struct tcf_skbmod *d = to_skbmod(a);
 204         unsigned char *b = skb_tail_pointer(skb);
 205         struct tcf_skbmod_params  *p = rtnl_dereference(d->skbmod_p);
 206         struct tc_skbmod opt = {
 207                 .index   = d->tcf_index,
 208                 .refcnt  = d->tcf_refcnt - ref,
 209                 .bindcnt = d->tcf_bindcnt - bind,
 210                 .action  = d->tcf_action,
 211         };
 212         struct tcf_t t;
 213
 214         opt.flags  = p->flags;
 215         if (nla_put(skb, TCA_SKBMOD_PARMS, sizeof(opt), &opt))
 216                 goto nla_put_failure;
 217         if ((p->flags & SKBMOD_F_DMAC) &&
 218             nla_put(skb, TCA_SKBMOD_DMAC, ETH_ALEN, p->eth_dst))
 219                 goto nla_put_failure;
 220         if ((p->flags & SKBMOD_F_SMAC) &&
 221             nla_put(skb, TCA_SKBMOD_SMAC, ETH_ALEN, p->eth_src))
 222                 goto nla_put_failure;
 223         if ((p->flags & SKBMOD_F_ETYPE) &&
 224             nla_put_u16(skb, TCA_SKBMOD_ETYPE, ntohs(p->eth_type)))
 225                 goto nla_put_failure;
 226
 227         tcf_tm_dump(&t, &d->tcf_tm);
 228         if (nla_put_64bit(skb, TCA_SKBMOD_TM, sizeof(t), &t, TCA_SKBMOD_PAD))
 229                 goto nla_put_failure;
 230
 231         return skb->len;
 232 nla_put_failure:
 233         nlmsg_trim(skb, b);
 234         return -1;
 235 }
 236
 237 static int tcf_skbmod_walker(struct net *net, struct sk_buff *skb,
 238                              struct netlink_callback *cb, int type,
 239                              const struct tc_action_ops *ops)
 240 {
 241         struct tc_action_net *tn = net_generic(net, skbmod_net_id);
 242
 243         return tcf_generic_walker(tn, skb, cb, type, ops);
 244 }
 245
 246 static int tcf_skbmod_search(struct net *net, struct tc_action **a, u32 index)
 247 {
 248         struct tc_action_net *tn = net_generic(net, skbmod_net_id);
 249
 250         return tcf_idr_search(tn, a, index);
 251 }
 252
 253 static struct tc_action_ops act_skbmod_ops = {
 254         .kind           =       "skbmod",
 255         .type           =       TCA_ACT_SKBMOD,
 256         .owner          =       THIS_MODULE,
 257         .act            =       tcf_skbmod_run,
 258         .dump           =       tcf_skbmod_dump,
 259         .init           =       tcf_skbmod_init,
 260         .cleanup        =       tcf_skbmod_cleanup,
 261         .walk           =       tcf_skbmod_walker,
 262         .lookup         =       tcf_skbmod_search,
 263         .size           =       sizeof(struct tcf_skbmod),
 264 };
 265
 266 static __net_init int skbmod_init_net(struct net *net)
 267 {
 268         struct tc_action_net *tn = net_generic(net, skbmod_net_id);
 269
 270         return tc_action_net_init(tn, &act_skbmod_ops);
 271 }
 272
 273 static void __net_exit skbmod_exit_net(struct list_head *net_list)
 274 {
 275         tc_action_net_exit(net_list, skbmod_net_id);
 276 }
 277
 278 static struct pernet_operations skbmod_net_ops = {
 279         .init = skbmod_init_net,
 280         .exit_batch = 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);