1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3  * connection tracking helpers.
4  *
5  * 16 Dec 2003: Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
6  *	- generalize L3 protocol dependent part.
7  *
8  * Derived from include/linux/netfiter_ipv4/ip_conntrack_helper.h
9  */
10 
11 #ifndef _NF_CONNTRACK_HELPER_H
12 #define _NF_CONNTRACK_HELPER_H
13 #include <linux/refcount.h>
14 #include <net/netfilter/nf_conntrack.h>
15 #include <net/netfilter/nf_conntrack_extend.h>
16 #include <net/netfilter/nf_conntrack_expect.h>
17 
18 #define NF_NAT_HELPER_PREFIX		"ip_nat_"
19 #define NF_NAT_HELPER_NAME(name)	NF_NAT_HELPER_PREFIX name
20 #define MODULE_ALIAS_NF_NAT_HELPER(name) \
21 	MODULE_ALIAS(NF_NAT_HELPER_NAME(name))
22 
23 struct module;
24 
25 enum nf_ct_helper_flags {
26 	NF_CT_HELPER_F_USERSPACE	= (1 << 0),
27 	NF_CT_HELPER_F_CONFIGURED	= (1 << 1),
28 };
29 
30 #define NF_CT_HELPER_NAME_LEN	16
31 
32 struct nf_conntrack_helper {
33 	struct hlist_node hnode;	/* Internal use. */
34 
35 	char name[NF_CT_HELPER_NAME_LEN]; /* name of the module */
36 	refcount_t refcnt;
37 	struct module *me;		/* pointer to self */
38 	const struct nf_conntrack_expect_policy *expect_policy;
39 
40 	/* Tuple of things we will help (compared against server response) */
41 	struct nf_conntrack_tuple tuple;
42 
43 	/* Function to call when data passes; return verdict, or -1 to
44            invalidate. */
45 	int (*help)(struct sk_buff *skb,
46 		    unsigned int protoff,
47 		    struct nf_conn *ct,
48 		    enum ip_conntrack_info conntrackinfo);
49 
50 	void (*destroy)(struct nf_conn *ct);
51 
52 	int (*from_nlattr)(struct nlattr *attr, struct nf_conn *ct);
53 	int (*to_nlattr)(struct sk_buff *skb, const struct nf_conn *ct);
54 	unsigned int expect_class_max;
55 
56 	unsigned int flags;
57 
58 	/* For user-space helpers: */
59 	unsigned int queue_num;
60 	/* length of userspace private data stored in nf_conn_help->data */
61 	u16 data_len;
62 	/* name of NAT helper module */
63 	char nat_mod_name[NF_CT_HELPER_NAME_LEN];
64 };
65 
66 /* Must be kept in sync with the classes defined by helpers */
67 #define NF_CT_MAX_EXPECT_CLASSES	4
68 
69 /* nf_conn feature for connections that have a helper */
70 struct nf_conn_help {
71 	/* Helper. if any */
72 	struct nf_conntrack_helper __rcu *helper;
73 
74 	struct hlist_head expectations;
75 
76 	/* Current number of expected connections */
77 	u8 expecting[NF_CT_MAX_EXPECT_CLASSES];
78 
79 	/* private helper information. */
80 	char data[32] __aligned(8);
81 };
82 
83 #define NF_CT_HELPER_BUILD_BUG_ON(structsize) \
84 	BUILD_BUG_ON((structsize) > sizeof_field(struct nf_conn_help, data))
85 
86 struct nf_conntrack_helper *__nf_conntrack_helper_find(const char *name,
87 						       u16 l3num, u8 protonum);
88 
89 struct nf_conntrack_helper *nf_conntrack_helper_try_module_get(const char *name,
90 							       u16 l3num,
91 							       u8 protonum);
92 void nf_conntrack_helper_put(struct nf_conntrack_helper *helper);
93 
94 void nf_ct_helper_init(struct nf_conntrack_helper *helper,
95 		       u16 l3num, u16 protonum, const char *name,
96 		       u16 default_port, u16 spec_port, u32 id,
97 		       const struct nf_conntrack_expect_policy *exp_pol,
98 		       u32 expect_class_max,
99 		       int (*help)(struct sk_buff *skb, unsigned int protoff,
100 				   struct nf_conn *ct,
101 				   enum ip_conntrack_info ctinfo),
102 		       int (*from_nlattr)(struct nlattr *attr,
103 					  struct nf_conn *ct),
104 		       struct module *module);
105 
106 int nf_conntrack_helper_register(struct nf_conntrack_helper *);
107 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *);
108 
109 int nf_conntrack_helpers_register(struct nf_conntrack_helper *, unsigned int);
110 void nf_conntrack_helpers_unregister(struct nf_conntrack_helper *,
111 				     unsigned int);
112 
113 struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp);
114 
115 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
116 			      gfp_t flags);
117 
118 void nf_ct_helper_destroy(struct nf_conn *ct);
119 
nfct_help(const struct nf_conn * ct)120 static inline struct nf_conn_help *nfct_help(const struct nf_conn *ct)
121 {
122 	return nf_ct_ext_find(ct, NF_CT_EXT_HELPER);
123 }
124 
nfct_help_data(const struct nf_conn * ct)125 static inline void *nfct_help_data(const struct nf_conn *ct)
126 {
127 	struct nf_conn_help *help;
128 
129 	help = nf_ct_ext_find(ct, NF_CT_EXT_HELPER);
130 
131 	return (void *)help->data;
132 }
133 
134 void nf_conntrack_helper_pernet_init(struct net *net);
135 
136 int nf_conntrack_helper_init(void);
137 void nf_conntrack_helper_fini(void);
138 
139 int nf_conntrack_broadcast_help(struct sk_buff *skb, struct nf_conn *ct,
140 				enum ip_conntrack_info ctinfo,
141 				unsigned int timeout);
142 
143 struct nf_ct_helper_expectfn {
144 	struct list_head head;
145 	const char *name;
146 	void (*expectfn)(struct nf_conn *ct, struct nf_conntrack_expect *exp);
147 };
148 
149 __printf(3,4)
150 void nf_ct_helper_log(struct sk_buff *skb, const struct nf_conn *ct,
151 		      const char *fmt, ...);
152 
153 void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n);
154 void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n);
155 struct nf_ct_helper_expectfn *
156 nf_ct_helper_expectfn_find_by_name(const char *name);
157 struct nf_ct_helper_expectfn *
158 nf_ct_helper_expectfn_find_by_symbol(const void *symbol);
159 
160 extern struct hlist_head *nf_ct_helper_hash;
161 extern unsigned int nf_ct_helper_hsize;
162 
163 struct nf_conntrack_nat_helper {
164 	struct list_head list;
165 	char mod_name[NF_CT_HELPER_NAME_LEN];	/* module name */
166 	struct module *module;			/* pointer to self */
167 };
168 
169 #define NF_CT_NAT_HELPER_INIT(name) \
170 	{ \
171 	.mod_name = NF_NAT_HELPER_NAME(name), \
172 	.module = THIS_MODULE \
173 	}
174 
175 void nf_nat_helper_register(struct nf_conntrack_nat_helper *nat);
176 void nf_nat_helper_unregister(struct nf_conntrack_nat_helper *nat);
177 int nf_nat_helper_try_module_get(const char *name, u16 l3num,
178 				 u8 protonum);
179 void nf_nat_helper_put(struct nf_conntrack_helper *helper);
180 void nf_ct_set_auto_assign_helper_warned(struct net *net);
181 #endif /*_NF_CONNTRACK_HELPER_H*/
182