Commit | Line | Data |
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f6ebe77f HW |
1 | /* netfilter.c: look after the filters for various protocols. |
2 | * Heavily influenced by the old firewall.c by David Bonn and Alan Cox. | |
3 | * | |
4 | * Thanks to Rob `CmdrTaco' Malda for not influencing this code in any | |
5 | * way. | |
6 | * | |
7 | * Rusty Russell (C)2000 -- This code is GPL. | |
8 | * | |
9 | * February 2000: Modified by James Morris to have 1 queue per protocol. | |
10 | * 15-Mar-2000: Added NF_REPEAT --RR. | |
11 | * 08-May-2003: Internal logging interface added by Jozsef Kadlecsik. | |
12 | */ | |
13 | #include <linux/config.h> | |
14 | #include <linux/kernel.h> | |
15 | #include <linux/netfilter.h> | |
16 | #include <net/protocol.h> | |
17 | #include <linux/init.h> | |
18 | #include <linux/skbuff.h> | |
19 | #include <linux/wait.h> | |
20 | #include <linux/module.h> | |
21 | #include <linux/interrupt.h> | |
22 | #include <linux/if.h> | |
23 | #include <linux/netdevice.h> | |
24 | #include <linux/inetdevice.h> | |
25 | #include <linux/proc_fs.h> | |
26 | #include <net/sock.h> | |
27 | ||
28 | #include "nf_internals.h" | |
29 | ||
30 | /* In this code, we can be waiting indefinitely for userspace to | |
31 | * service a packet if a hook returns NF_QUEUE. We could keep a count | |
32 | * of skbuffs queued for userspace, and not deregister a hook unless | |
33 | * this is zero, but that sucks. Now, we simply check when the | |
34 | * packets come back: if the hook is gone, the packet is discarded. */ | |
35 | struct list_head nf_hooks[NPROTO][NF_MAX_HOOKS]; | |
36 | EXPORT_SYMBOL(nf_hooks); | |
37 | static DEFINE_SPINLOCK(nf_hook_lock); | |
38 | ||
39 | int nf_register_hook(struct nf_hook_ops *reg) | |
40 | { | |
41 | struct list_head *i; | |
42 | ||
43 | spin_lock_bh(&nf_hook_lock); | |
44 | list_for_each(i, &nf_hooks[reg->pf][reg->hooknum]) { | |
45 | if (reg->priority < ((struct nf_hook_ops *)i)->priority) | |
46 | break; | |
47 | } | |
48 | list_add_rcu(®->list, i->prev); | |
49 | spin_unlock_bh(&nf_hook_lock); | |
50 | ||
51 | synchronize_net(); | |
52 | return 0; | |
53 | } | |
54 | EXPORT_SYMBOL(nf_register_hook); | |
55 | ||
56 | void nf_unregister_hook(struct nf_hook_ops *reg) | |
57 | { | |
58 | spin_lock_bh(&nf_hook_lock); | |
59 | list_del_rcu(®->list); | |
60 | spin_unlock_bh(&nf_hook_lock); | |
61 | ||
62 | synchronize_net(); | |
63 | } | |
64 | EXPORT_SYMBOL(nf_unregister_hook); | |
65 | ||
66 | unsigned int nf_iterate(struct list_head *head, | |
67 | struct sk_buff **skb, | |
68 | int hook, | |
69 | const struct net_device *indev, | |
70 | const struct net_device *outdev, | |
71 | struct list_head **i, | |
72 | int (*okfn)(struct sk_buff *), | |
73 | int hook_thresh) | |
74 | { | |
75 | unsigned int verdict; | |
76 | ||
77 | /* | |
78 | * The caller must not block between calls to this | |
79 | * function because of risk of continuing from deleted element. | |
80 | */ | |
81 | list_for_each_continue_rcu(*i, head) { | |
82 | struct nf_hook_ops *elem = (struct nf_hook_ops *)*i; | |
83 | ||
84 | if (hook_thresh > elem->priority) | |
85 | continue; | |
86 | ||
87 | /* Optimization: we don't need to hold module | |
88 | reference here, since function can't sleep. --RR */ | |
89 | verdict = elem->hook(hook, skb, indev, outdev, okfn); | |
90 | if (verdict != NF_ACCEPT) { | |
91 | #ifdef CONFIG_NETFILTER_DEBUG | |
92 | if (unlikely((verdict & NF_VERDICT_MASK) | |
93 | > NF_MAX_VERDICT)) { | |
94 | NFDEBUG("Evil return from %p(%u).\n", | |
95 | elem->hook, hook); | |
96 | continue; | |
97 | } | |
98 | #endif | |
99 | if (verdict != NF_REPEAT) | |
100 | return verdict; | |
101 | *i = (*i)->prev; | |
102 | } | |
103 | } | |
104 | return NF_ACCEPT; | |
105 | } | |
106 | ||
107 | ||
108 | /* Returns 1 if okfn() needs to be executed by the caller, | |
109 | * -EPERM for NF_DROP, 0 otherwise. */ | |
110 | int nf_hook_slow(int pf, unsigned int hook, struct sk_buff **pskb, | |
111 | struct net_device *indev, | |
112 | struct net_device *outdev, | |
113 | int (*okfn)(struct sk_buff *), | |
114 | int hook_thresh) | |
115 | { | |
116 | struct list_head *elem; | |
117 | unsigned int verdict; | |
118 | int ret = 0; | |
119 | ||
120 | /* We may already have this, but read-locks nest anyway */ | |
121 | rcu_read_lock(); | |
122 | ||
123 | elem = &nf_hooks[pf][hook]; | |
124 | next_hook: | |
125 | verdict = nf_iterate(&nf_hooks[pf][hook], pskb, hook, indev, | |
126 | outdev, &elem, okfn, hook_thresh); | |
127 | if (verdict == NF_ACCEPT || verdict == NF_STOP) { | |
128 | ret = 1; | |
129 | goto unlock; | |
130 | } else if (verdict == NF_DROP) { | |
131 | kfree_skb(*pskb); | |
132 | ret = -EPERM; | |
133 | } else if ((verdict & NF_VERDICT_MASK) == NF_QUEUE) { | |
134 | NFDEBUG("nf_hook: Verdict = QUEUE.\n"); | |
135 | if (!nf_queue(pskb, elem, pf, hook, indev, outdev, okfn, | |
136 | verdict >> NF_VERDICT_BITS)) | |
137 | goto next_hook; | |
138 | } | |
139 | unlock: | |
140 | rcu_read_unlock(); | |
141 | return ret; | |
142 | } | |
143 | EXPORT_SYMBOL(nf_hook_slow); | |
144 | ||
145 | ||
146 | int skb_make_writable(struct sk_buff **pskb, unsigned int writable_len) | |
147 | { | |
148 | struct sk_buff *nskb; | |
149 | ||
150 | if (writable_len > (*pskb)->len) | |
151 | return 0; | |
152 | ||
153 | /* Not exclusive use of packet? Must copy. */ | |
154 | if (skb_shared(*pskb) || skb_cloned(*pskb)) | |
155 | goto copy_skb; | |
156 | ||
157 | return pskb_may_pull(*pskb, writable_len); | |
158 | ||
159 | copy_skb: | |
160 | nskb = skb_copy(*pskb, GFP_ATOMIC); | |
161 | if (!nskb) | |
162 | return 0; | |
163 | BUG_ON(skb_is_nonlinear(nskb)); | |
164 | ||
165 | /* Rest of kernel will get very unhappy if we pass it a | |
166 | suddenly-orphaned skbuff */ | |
167 | if ((*pskb)->sk) | |
168 | skb_set_owner_w(nskb, (*pskb)->sk); | |
169 | kfree_skb(*pskb); | |
170 | *pskb = nskb; | |
171 | return 1; | |
172 | } | |
173 | EXPORT_SYMBOL(skb_make_writable); | |
174 | ||
175 | ||
176 | /* This does not belong here, but locally generated errors need it if connection | |
177 | tracking in use: without this, connection may not be in hash table, and hence | |
178 | manufactured ICMP or RST packets will not be associated with it. */ | |
179 | void (*ip_ct_attach)(struct sk_buff *, struct sk_buff *); | |
180 | EXPORT_SYMBOL(ip_ct_attach); | |
181 | ||
182 | void nf_ct_attach(struct sk_buff *new, struct sk_buff *skb) | |
183 | { | |
184 | void (*attach)(struct sk_buff *, struct sk_buff *); | |
185 | ||
186 | if (skb->nfct && (attach = ip_ct_attach) != NULL) { | |
187 | mb(); /* Just to be sure: must be read before executing this */ | |
188 | attach(new, skb); | |
189 | } | |
190 | } | |
191 | EXPORT_SYMBOL(nf_ct_attach); | |
192 | ||
193 | #ifdef CONFIG_PROC_FS | |
194 | struct proc_dir_entry *proc_net_netfilter; | |
195 | EXPORT_SYMBOL(proc_net_netfilter); | |
196 | #endif | |
197 | ||
198 | void __init netfilter_init(void) | |
199 | { | |
200 | int i, h; | |
201 | for (i = 0; i < NPROTO; i++) { | |
202 | for (h = 0; h < NF_MAX_HOOKS; h++) | |
203 | INIT_LIST_HEAD(&nf_hooks[i][h]); | |
204 | } | |
205 | ||
206 | #ifdef CONFIG_PROC_FS | |
207 | proc_net_netfilter = proc_mkdir("netfilter", proc_net); | |
208 | if (!proc_net_netfilter) | |
209 | panic("cannot create netfilter proc entry"); | |
210 | #endif | |
211 | ||
212 | if (netfilter_queue_init() < 0) | |
213 | panic("cannot initialize nf_queue"); | |
214 | if (netfilter_log_init() < 0) | |
215 | panic("cannot initialize nf_log"); | |
216 | } |