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Linux/net/sched/act_skbmod.c

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  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, 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 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                              struct netlink_ext_ack *extack)
241 {
242         struct tc_action_net *tn = net_generic(net, skbmod_net_id);
243 
244         return tcf_generic_walker(tn, skb, cb, type, ops, extack);
245 }
246 
247 static int tcf_skbmod_search(struct net *net, struct tc_action **a, u32 index,
248                              struct netlink_ext_ack *extack)
249 {
250         struct tc_action_net *tn = net_generic(net, skbmod_net_id);
251 
252         return tcf_idr_search(tn, a, index);
253 }
254 
255 static struct tc_action_ops act_skbmod_ops = {
256         .kind           =       "skbmod",
257         .type           =       TCA_ACT_SKBMOD,
258         .owner          =       THIS_MODULE,
259         .act            =       tcf_skbmod_run,
260         .dump           =       tcf_skbmod_dump,
261         .init           =       tcf_skbmod_init,
262         .cleanup        =       tcf_skbmod_cleanup,
263         .walk           =       tcf_skbmod_walker,
264         .lookup         =       tcf_skbmod_search,
265         .size           =       sizeof(struct tcf_skbmod),
266 };
267 
268 static __net_init int skbmod_init_net(struct net *net)
269 {
270         struct tc_action_net *tn = net_generic(net, skbmod_net_id);
271 
272         return tc_action_net_init(tn, &act_skbmod_ops);
273 }
274 
275 static void __net_exit skbmod_exit_net(struct list_head *net_list)
276 {
277         tc_action_net_exit(net_list, skbmod_net_id);
278 }
279 
280 static struct pernet_operations skbmod_net_ops = {
281         .init = skbmod_init_net,
282         .exit_batch = skbmod_exit_net,
283         .id   = &skbmod_net_id,
284         .size = sizeof(struct tc_action_net),
285 };
286 
287 MODULE_AUTHOR("Jamal Hadi Salim, <jhs@mojatatu.com>");
288 MODULE_DESCRIPTION("SKB data mod-ing");
289 MODULE_LICENSE("GPL");
290 
291 static int __init skbmod_init_module(void)
292 {
293         return tcf_register_action(&act_skbmod_ops, &skbmod_net_ops);
294 }
295 
296 static void __exit skbmod_cleanup_module(void)
297 {
298         tcf_unregister_action(&act_skbmod_ops, &skbmod_net_ops);
299 }
300 
301 module_init(skbmod_init_module);
302 module_exit(skbmod_cleanup_module);
303 

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