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

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