nf_queue.c (8037B)
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 struct nf_bridge_info *nf_bridge; 86 87 nf_bridge = nf_bridge_info_get(skb); 88 if (nf_bridge) { 89 entry->physin = nf_bridge_get_physindev(skb); 90 entry->physout = nf_bridge_get_physoutdev(skb); 91 } else { 92 entry->physin = NULL; 93 entry->physout = NULL; 94 } 95#endif 96} 97 98/* Bump dev refs so they don't vanish while packet is out */ 99bool nf_queue_entry_get_refs(struct nf_queue_entry *entry) 100{ 101 struct nf_hook_state *state = &entry->state; 102 103 if (state->sk && !refcount_inc_not_zero(&state->sk->sk_refcnt)) 104 return false; 105 106 dev_hold(state->in); 107 dev_hold(state->out); 108 109#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER) 110 dev_hold(entry->physin); 111 dev_hold(entry->physout); 112#endif 113 return true; 114} 115EXPORT_SYMBOL_GPL(nf_queue_entry_get_refs); 116 117void nf_queue_nf_hook_drop(struct net *net) 118{ 119 const struct nf_queue_handler *qh; 120 121 rcu_read_lock(); 122 qh = rcu_dereference(nf_queue_handler); 123 if (qh) 124 qh->nf_hook_drop(net); 125 rcu_read_unlock(); 126} 127EXPORT_SYMBOL_GPL(nf_queue_nf_hook_drop); 128 129static void nf_ip_saveroute(const struct sk_buff *skb, 130 struct nf_queue_entry *entry) 131{ 132 struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); 133 134 if (entry->state.hook == NF_INET_LOCAL_OUT) { 135 const struct iphdr *iph = ip_hdr(skb); 136 137 rt_info->tos = iph->tos; 138 rt_info->daddr = iph->daddr; 139 rt_info->saddr = iph->saddr; 140 rt_info->mark = skb->mark; 141 } 142} 143 144static void nf_ip6_saveroute(const struct sk_buff *skb, 145 struct nf_queue_entry *entry) 146{ 147 struct ip6_rt_info *rt_info = nf_queue_entry_reroute(entry); 148 149 if (entry->state.hook == NF_INET_LOCAL_OUT) { 150 const struct ipv6hdr *iph = ipv6_hdr(skb); 151 152 rt_info->daddr = iph->daddr; 153 rt_info->saddr = iph->saddr; 154 rt_info->mark = skb->mark; 155 } 156} 157 158static int __nf_queue(struct sk_buff *skb, const struct nf_hook_state *state, 159 unsigned int index, unsigned int queuenum) 160{ 161 struct nf_queue_entry *entry = NULL; 162 const struct nf_queue_handler *qh; 163 unsigned int route_key_size; 164 int status; 165 166 /* QUEUE == DROP if no one is waiting, to be safe. */ 167 qh = rcu_dereference(nf_queue_handler); 168 if (!qh) 169 return -ESRCH; 170 171 switch (state->pf) { 172 case AF_INET: 173 route_key_size = sizeof(struct ip_rt_info); 174 break; 175 case AF_INET6: 176 route_key_size = sizeof(struct ip6_rt_info); 177 break; 178 default: 179 route_key_size = 0; 180 break; 181 } 182 183 if (skb_sk_is_prefetched(skb)) { 184 struct sock *sk = skb->sk; 185 186 if (!sk_is_refcounted(sk)) { 187 if (!refcount_inc_not_zero(&sk->sk_refcnt)) 188 return -ENOTCONN; 189 190 /* drop refcount on skb_orphan */ 191 skb->destructor = sock_edemux; 192 } 193 } 194 195 entry = kmalloc(sizeof(*entry) + route_key_size, GFP_ATOMIC); 196 if (!entry) 197 return -ENOMEM; 198 199 if (skb_dst(skb) && !skb_dst_force(skb)) { 200 kfree(entry); 201 return -ENETDOWN; 202 } 203 204 *entry = (struct nf_queue_entry) { 205 .skb = skb, 206 .state = *state, 207 .hook_index = index, 208 .size = sizeof(*entry) + route_key_size, 209 }; 210 211 __nf_queue_entry_init_physdevs(entry); 212 213 if (!nf_queue_entry_get_refs(entry)) { 214 kfree(entry); 215 return -ENOTCONN; 216 } 217 218 switch (entry->state.pf) { 219 case AF_INET: 220 nf_ip_saveroute(skb, entry); 221 break; 222 case AF_INET6: 223 nf_ip6_saveroute(skb, entry); 224 break; 225 } 226 227 status = qh->outfn(entry, queuenum); 228 if (status < 0) { 229 nf_queue_entry_free(entry); 230 return status; 231 } 232 233 return 0; 234} 235 236/* Packets leaving via this function must come back through nf_reinject(). */ 237int nf_queue(struct sk_buff *skb, struct nf_hook_state *state, 238 unsigned int index, unsigned int verdict) 239{ 240 int ret; 241 242 ret = __nf_queue(skb, state, index, verdict >> NF_VERDICT_QBITS); 243 if (ret < 0) { 244 if (ret == -ESRCH && 245 (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS)) 246 return 1; 247 kfree_skb(skb); 248 } 249 250 return 0; 251} 252EXPORT_SYMBOL_GPL(nf_queue); 253 254static unsigned int nf_iterate(struct sk_buff *skb, 255 struct nf_hook_state *state, 256 const struct nf_hook_entries *hooks, 257 unsigned int *index) 258{ 259 const struct nf_hook_entry *hook; 260 unsigned int verdict, i = *index; 261 262 while (i < hooks->num_hook_entries) { 263 hook = &hooks->hooks[i]; 264repeat: 265 verdict = nf_hook_entry_hookfn(hook, skb, state); 266 if (verdict != NF_ACCEPT) { 267 *index = i; 268 if (verdict != NF_REPEAT) 269 return verdict; 270 goto repeat; 271 } 272 i++; 273 } 274 275 *index = i; 276 return NF_ACCEPT; 277} 278 279static struct nf_hook_entries *nf_hook_entries_head(const struct net *net, u8 pf, u8 hooknum) 280{ 281 switch (pf) { 282#ifdef CONFIG_NETFILTER_FAMILY_BRIDGE 283 case NFPROTO_BRIDGE: 284 return rcu_dereference(net->nf.hooks_bridge[hooknum]); 285#endif 286 case NFPROTO_IPV4: 287 return rcu_dereference(net->nf.hooks_ipv4[hooknum]); 288 case NFPROTO_IPV6: 289 return rcu_dereference(net->nf.hooks_ipv6[hooknum]); 290 default: 291 WARN_ON_ONCE(1); 292 return NULL; 293 } 294 295 return NULL; 296} 297 298/* Caller must hold rcu read-side lock */ 299void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict) 300{ 301 const struct nf_hook_entry *hook_entry; 302 const struct nf_hook_entries *hooks; 303 struct sk_buff *skb = entry->skb; 304 const struct net *net; 305 unsigned int i; 306 int err; 307 u8 pf; 308 309 net = entry->state.net; 310 pf = entry->state.pf; 311 312 hooks = nf_hook_entries_head(net, pf, entry->state.hook); 313 314 i = entry->hook_index; 315 if (WARN_ON_ONCE(!hooks || i >= hooks->num_hook_entries)) { 316 kfree_skb(skb); 317 nf_queue_entry_free(entry); 318 return; 319 } 320 321 hook_entry = &hooks->hooks[i]; 322 323 /* Continue traversal iff userspace said ok... */ 324 if (verdict == NF_REPEAT) 325 verdict = nf_hook_entry_hookfn(hook_entry, skb, &entry->state); 326 327 if (verdict == NF_ACCEPT) { 328 if (nf_reroute(skb, entry) < 0) 329 verdict = NF_DROP; 330 } 331 332 if (verdict == NF_ACCEPT) { 333next_hook: 334 ++i; 335 verdict = nf_iterate(skb, &entry->state, hooks, &i); 336 } 337 338 switch (verdict & NF_VERDICT_MASK) { 339 case NF_ACCEPT: 340 case NF_STOP: 341 local_bh_disable(); 342 entry->state.okfn(entry->state.net, entry->state.sk, skb); 343 local_bh_enable(); 344 break; 345 case NF_QUEUE: 346 err = nf_queue(skb, &entry->state, i, verdict); 347 if (err == 1) 348 goto next_hook; 349 break; 350 case NF_STOLEN: 351 break; 352 default: 353 kfree_skb(skb); 354 } 355 356 nf_queue_entry_free(entry); 357} 358EXPORT_SYMBOL(nf_reinject);