nf_conntrack_helper.c revision 9457d851fc5df54522d733f72cbb1f02ab59272e
1/* Helper handling for netfilter. */ 2 3/* (C) 1999-2001 Paul `Rusty' Russell 4 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org> 5 * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org> 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License version 2 as 9 * published by the Free Software Foundation. 10 */ 11 12#include <linux/types.h> 13#include <linux/netfilter.h> 14#include <linux/module.h> 15#include <linux/skbuff.h> 16#include <linux/vmalloc.h> 17#include <linux/stddef.h> 18#include <linux/slab.h> 19#include <linux/random.h> 20#include <linux/err.h> 21#include <linux/kernel.h> 22#include <linux/netdevice.h> 23 24#include <net/netfilter/nf_conntrack.h> 25#include <net/netfilter/nf_conntrack_l3proto.h> 26#include <net/netfilter/nf_conntrack_l4proto.h> 27#include <net/netfilter/nf_conntrack_helper.h> 28#include <net/netfilter/nf_conntrack_core.h> 29 30static __read_mostly LIST_HEAD(helpers); 31 32struct nf_conntrack_helper * 33__nf_ct_helper_find(const struct nf_conntrack_tuple *tuple) 34{ 35 struct nf_conntrack_helper *h; 36 37 list_for_each_entry(h, &helpers, list) { 38 if (nf_ct_tuple_mask_cmp(tuple, &h->tuple, &h->mask)) 39 return h; 40 } 41 return NULL; 42} 43 44struct nf_conntrack_helper * 45nf_ct_helper_find_get( const struct nf_conntrack_tuple *tuple) 46{ 47 struct nf_conntrack_helper *helper; 48 49 /* need nf_conntrack_lock to assure that helper exists until 50 * try_module_get() is called */ 51 read_lock_bh(&nf_conntrack_lock); 52 53 helper = __nf_ct_helper_find(tuple); 54 if (helper) { 55 /* need to increase module usage count to assure helper will 56 * not go away while the caller is e.g. busy putting a 57 * conntrack in the hash that uses the helper */ 58 if (!try_module_get(helper->me)) 59 helper = NULL; 60 } 61 62 read_unlock_bh(&nf_conntrack_lock); 63 64 return helper; 65} 66 67void nf_ct_helper_put(struct nf_conntrack_helper *helper) 68{ 69 module_put(helper->me); 70} 71 72struct nf_conntrack_helper * 73__nf_conntrack_helper_find_byname(const char *name) 74{ 75 struct nf_conntrack_helper *h; 76 77 list_for_each_entry(h, &helpers, list) { 78 if (!strcmp(h->name, name)) 79 return h; 80 } 81 82 return NULL; 83} 84 85static inline int unhelp(struct nf_conntrack_tuple_hash *i, 86 const struct nf_conntrack_helper *me) 87{ 88 struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i); 89 struct nf_conn_help *help = nfct_help(ct); 90 91 if (help && help->helper == me) { 92 nf_conntrack_event(IPCT_HELPER, ct); 93 help->helper = NULL; 94 } 95 return 0; 96} 97 98int nf_conntrack_helper_register(struct nf_conntrack_helper *me) 99{ 100 int size, ret; 101 102 BUG_ON(me->timeout == 0); 103 104 size = ALIGN(sizeof(struct nf_conn), __alignof__(struct nf_conn_help)) + 105 sizeof(struct nf_conn_help); 106 ret = nf_conntrack_register_cache(NF_CT_F_HELP, "nf_conntrack:help", 107 size); 108 if (ret < 0) { 109 printk(KERN_ERR "nf_conntrack_helper_register: Unable to create slab cache for conntracks\n"); 110 return ret; 111 } 112 write_lock_bh(&nf_conntrack_lock); 113 list_add(&me->list, &helpers); 114 write_unlock_bh(&nf_conntrack_lock); 115 116 return 0; 117} 118 119void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me) 120{ 121 unsigned int i; 122 struct nf_conntrack_tuple_hash *h; 123 struct nf_conntrack_expect *exp, *tmp; 124 125 /* Need write lock here, to delete helper. */ 126 write_lock_bh(&nf_conntrack_lock); 127 list_del(&me->list); 128 129 /* Get rid of expectations */ 130 list_for_each_entry_safe(exp, tmp, &nf_conntrack_expect_list, list) { 131 struct nf_conn_help *help = nfct_help(exp->master); 132 if ((help->helper == me || exp->helper == me) && 133 del_timer(&exp->timeout)) { 134 nf_ct_unlink_expect(exp); 135 nf_conntrack_expect_put(exp); 136 } 137 } 138 139 /* Get rid of expecteds, set helpers to NULL. */ 140 list_for_each_entry(h, &unconfirmed, list) 141 unhelp(h, me); 142 for (i = 0; i < nf_conntrack_htable_size; i++) { 143 list_for_each_entry(h, &nf_conntrack_hash[i], list) 144 unhelp(h, me); 145 } 146 write_unlock_bh(&nf_conntrack_lock); 147 148 /* Someone could be still looking at the helper in a bh. */ 149 synchronize_net(); 150} 151