nf_queue.c

  1/*
  2 * Rusty Russell (C)2000 -- This code is GPL.
  3 * Patrick McHardy (c) 2006-2012
  4 */
  5
  6#include <linux/kernel.h>
  7#include <linux/slab.h>
  8#include <linux/init.h>
  9#include <linux/module.h>
 10#include <linux/proc_fs.h>
 11#include <linux/skbuff.h>
 12#include <linux/netfilter.h>
 13#include <linux/netfilter_ipv4.h>
 14#include <linux/netfilter_ipv6.h>
 15#include <linux/netfilter_bridge.h>
 16#include <linux/seq_file.h>
 17#include <linux/rcupdate.h>
 18#include <net/protocol.h>
 19#include <net/netfilter/nf_queue.h>
 20#include <net/dst.h>
 21
 22#include "nf_internals.h"
 23
 24static const struct nf_queue_handler __rcu *nf_queue_handler;
 25
 26/*
 27 * Hook for nfnetlink_queue to register its queue handler.
 28 * We do this so that most of the NFQUEUE code can be modular.
 29 *
 30 * Once the queue is registered it must reinject all packets it
 31 * receives, no matter what.
 32 */
 33
 34void nf_register_queue_handler(const struct nf_queue_handler *qh)
 35{
 36	/* should never happen, we only have one queueing backend in kernel */
 37	WARN_ON(rcu_access_pointer(nf_queue_handler));
 38	rcu_assign_pointer(nf_queue_handler, qh);
 39}
 40EXPORT_SYMBOL(nf_register_queue_handler);
 41
 42/* The caller must flush their queue before this */
 43void nf_unregister_queue_handler(void)
 44{
 45	RCU_INIT_POINTER(nf_queue_handler, NULL);
 46}
 47EXPORT_SYMBOL(nf_unregister_queue_handler);
 48
 49static void nf_queue_sock_put(struct sock *sk)
 50{
 51#ifdef CONFIG_INET
 52	sock_gen_put(sk);
 53#else
 54	sock_put(sk);
 55#endif
 56}
 57
 58static void nf_queue_entry_release_refs(struct nf_queue_entry *entry)
 59{
 60	struct nf_hook_state *state = &entry->state;
 61
 62	/* Release those devices we held, or Alexey will kill me. */
 63	dev_put(state->in);
 64	dev_put(state->out);
 65	if (state->sk)
 66		nf_queue_sock_put(state->sk);
 67
 68#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 69	dev_put(entry->physin);
 70	dev_put(entry->physout);
 71#endif
 72}
 73
 74void nf_queue_entry_free(struct nf_queue_entry *entry)
 75{
 76	nf_queue_entry_release_refs(entry);
 77	kfree(entry);
 78}
 79EXPORT_SYMBOL_GPL(nf_queue_entry_free);
 80
 81static void __nf_queue_entry_init_physdevs(struct nf_queue_entry *entry)
 82{
 83#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 84	const struct sk_buff *skb = entry->skb;
 85
 86	if (nf_bridge_info_exists(skb)) {
 87		entry->physin = nf_bridge_get_physindev(skb, entry->state.net);
 88		entry->physout = nf_bridge_get_physoutdev(skb);
 89	} else {
 90		entry->physin = NULL;
 91		entry->physout = NULL;
 92	}
 93#endif
 94}
 95
 96/* Bump dev refs so they don't vanish while packet is out */
 97bool nf_queue_entry_get_refs(struct nf_queue_entry *entry)
 98{
 99	struct nf_hook_state *state = &entry->state;
100
101	if (state->sk && !refcount_inc_not_zero(&state->sk->sk_refcnt))
102		return false;
103
104	dev_hold(state->in);
105	dev_hold(state->out);
106
107#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
108	dev_hold(entry->physin);
109	dev_hold(entry->physout);
110#endif
111	return true;
112}
113EXPORT_SYMBOL_GPL(nf_queue_entry_get_refs);
114
115void nf_queue_nf_hook_drop(struct net *net)
116{
117	const struct nf_queue_handler *qh;
118
119	rcu_read_lock();
120	qh = rcu_dereference(nf_queue_handler);
121	if (qh)
122		qh->nf_hook_drop(net);
123	rcu_read_unlock();
124}
125EXPORT_SYMBOL_GPL(nf_queue_nf_hook_drop);
126
127static void nf_ip_saveroute(const struct sk_buff *skb,
128			    struct nf_queue_entry *entry)
129{
130	struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
131
132	if (entry->state.hook == NF_INET_LOCAL_OUT) {
133		const struct iphdr *iph = ip_hdr(skb);
134
135		rt_info->tos = iph->tos;
136		rt_info->daddr = iph->daddr;
137		rt_info->saddr = iph->saddr;
138		rt_info->mark = skb->mark;
139	}
140}
141
142static void nf_ip6_saveroute(const struct sk_buff *skb,
143			     struct nf_queue_entry *entry)
144{
145	struct ip6_rt_info *rt_info = nf_queue_entry_reroute(entry);
146
147	if (entry->state.hook == NF_INET_LOCAL_OUT) {
148		const struct ipv6hdr *iph = ipv6_hdr(skb);
149
150		rt_info->daddr = iph->daddr;
151		rt_info->saddr = iph->saddr;
152		rt_info->mark = skb->mark;
153	}
154}
155
156static int __nf_queue(struct sk_buff *skb, const struct nf_hook_state *state,
157		      unsigned int index, unsigned int queuenum)
158{
159	struct nf_queue_entry *entry = NULL;
160	const struct nf_queue_handler *qh;
161	unsigned int route_key_size;
162	int status;
163
164	/* QUEUE == DROP if no one is waiting, to be safe. */
165	qh = rcu_dereference(nf_queue_handler);
166	if (!qh)
167		return -ESRCH;
168
169	switch (state->pf) {
170	case AF_INET:
171		route_key_size = sizeof(struct ip_rt_info);
172		break;
173	case AF_INET6:
174		route_key_size = sizeof(struct ip6_rt_info);
175		break;
176	default:
177		route_key_size = 0;
178		break;
179	}
180
181	if (skb_sk_is_prefetched(skb)) {
182		struct sock *sk = skb->sk;
183
184		if (!sk_is_refcounted(sk)) {
185			if (!refcount_inc_not_zero(&sk->sk_refcnt))
186				return -ENOTCONN;
187
188			/* drop refcount on skb_orphan */
189			skb->destructor = sock_edemux;
190		}
191	}
192
193	entry = kmalloc(sizeof(*entry) + route_key_size, GFP_ATOMIC);
194	if (!entry)
195		return -ENOMEM;
196
197	if (skb_dst(skb) && !skb_dst_force(skb)) {
198		kfree(entry);
199		return -ENETDOWN;
200	}
201
202	*entry = (struct nf_queue_entry) {
203		.skb	= skb,
204		.state	= *state,
205		.hook_index = index,
206		.size	= sizeof(*entry) + route_key_size,
207	};
208
209	__nf_queue_entry_init_physdevs(entry);
210
211	if (!nf_queue_entry_get_refs(entry)) {
212		kfree(entry);
213		return -ENOTCONN;
214	}
215
216	switch (entry->state.pf) {
217	case AF_INET:
218		nf_ip_saveroute(skb, entry);
219		break;
220	case AF_INET6:
221		nf_ip6_saveroute(skb, entry);
222		break;
223	}
224
225	status = qh->outfn(entry, queuenum);
226	if (status < 0) {
227		nf_queue_entry_free(entry);
228		return status;
229	}
230
231	return 0;
232}
233
234/* Packets leaving via this function must come back through nf_reinject(). */
235int nf_queue(struct sk_buff *skb, struct nf_hook_state *state,
236	     unsigned int index, unsigned int verdict)
237{
238	int ret;
239
240	ret = __nf_queue(skb, state, index, verdict >> NF_VERDICT_QBITS);
241	if (ret < 0) {
242		if (ret == -ESRCH &&
243		    (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS))
244			return 1;
245		kfree_skb(skb);
246	}
247
248	return 0;
249}
250EXPORT_SYMBOL_GPL(nf_queue);