1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __LINUX_NETLINK_H
3 #define __LINUX_NETLINK_H
4 
5 
6 #include <linux/capability.h>
7 #include <linux/skbuff.h>
8 #include <linux/export.h>
9 #include <net/scm.h>
10 #include <uapi/linux/netlink.h>
11 
12 struct net;
13 
14 void do_trace_netlink_extack(const char *msg);
15 
nlmsg_hdr(const struct sk_buff * skb)16 static inline struct nlmsghdr *nlmsg_hdr(const struct sk_buff *skb)
17 {
18 	return (struct nlmsghdr *)skb->data;
19 }
20 
21 enum netlink_skb_flags {
22 	NETLINK_SKB_DST		= 0x8,	/* Dst set in sendto or sendmsg */
23 };
24 
25 struct netlink_skb_parms {
26 	struct scm_creds	creds;		/* Skb credentials	*/
27 	__u32			portid;
28 	__u32			dst_group;
29 	__u32			flags;
30 	struct sock		*sk;
31 	bool			nsid_is_set;
32 	int			nsid;
33 };
34 
35 #define NETLINK_CB(skb)		(*(struct netlink_skb_parms*)&((skb)->cb))
36 #define NETLINK_CREDS(skb)	(&NETLINK_CB((skb)).creds)
37 
38 
39 void netlink_table_grab(void);
40 void netlink_table_ungrab(void);
41 
42 #define NL_CFG_F_NONROOT_RECV	(1 << 0)
43 #define NL_CFG_F_NONROOT_SEND	(1 << 1)
44 
45 /* optional Netlink kernel configuration parameters */
46 struct netlink_kernel_cfg {
47 	unsigned int	groups;
48 	unsigned int	flags;
49 	void		(*input)(struct sk_buff *skb);
50 	struct mutex	*cb_mutex;
51 	int		(*bind)(struct net *net, int group);
52 	void		(*unbind)(struct net *net, int group);
53 	bool		(*compare)(struct net *net, struct sock *sk);
54 };
55 
56 struct sock *__netlink_kernel_create(struct net *net, int unit,
57 					    struct module *module,
58 					    struct netlink_kernel_cfg *cfg);
59 static inline struct sock *
netlink_kernel_create(struct net * net,int unit,struct netlink_kernel_cfg * cfg)60 netlink_kernel_create(struct net *net, int unit, struct netlink_kernel_cfg *cfg)
61 {
62 	return __netlink_kernel_create(net, unit, THIS_MODULE, cfg);
63 }
64 
65 /* this can be increased when necessary - don't expose to userland */
66 #define NETLINK_MAX_COOKIE_LEN	20
67 
68 /**
69  * struct netlink_ext_ack - netlink extended ACK report struct
70  * @_msg: message string to report - don't access directly, use
71  *	%NL_SET_ERR_MSG
72  * @bad_attr: attribute with error
73  * @policy: policy for a bad attribute
74  * @miss_type: attribute type which was missing
75  * @miss_nest: nest missing an attribute (%NULL if missing top level attr)
76  * @cookie: cookie data to return to userspace (for success)
77  * @cookie_len: actual cookie data length
78  */
79 struct netlink_ext_ack {
80 	const char *_msg;
81 	const struct nlattr *bad_attr;
82 	const struct nla_policy *policy;
83 	const struct nlattr *miss_nest;
84 	u16 miss_type;
85 	u8 cookie[NETLINK_MAX_COOKIE_LEN];
86 	u8 cookie_len;
87 };
88 
89 /* Always use this macro, this allows later putting the
90  * message into a separate section or such for things
91  * like translation or listing all possible messages.
92  * Currently string formatting is not supported (due
93  * to the lack of an output buffer.)
94  */
95 #define NL_SET_ERR_MSG(extack, msg) do {		\
96 	static const char __msg[] = msg;		\
97 	struct netlink_ext_ack *__extack = (extack);	\
98 							\
99 	do_trace_netlink_extack(__msg);			\
100 							\
101 	if (__extack)					\
102 		__extack->_msg = __msg;			\
103 } while (0)
104 
105 #define NL_SET_ERR_MSG_MOD(extack, msg)			\
106 	NL_SET_ERR_MSG((extack), KBUILD_MODNAME ": " msg)
107 
108 #define NL_SET_BAD_ATTR_POLICY(extack, attr, pol) do {	\
109 	if ((extack)) {					\
110 		(extack)->bad_attr = (attr);		\
111 		(extack)->policy = (pol);		\
112 	}						\
113 } while (0)
114 
115 #define NL_SET_BAD_ATTR(extack, attr) NL_SET_BAD_ATTR_POLICY(extack, attr, NULL)
116 
117 #define NL_SET_ERR_MSG_ATTR_POL(extack, attr, pol, msg) do {	\
118 	static const char __msg[] = msg;			\
119 	struct netlink_ext_ack *__extack = (extack);		\
120 								\
121 	do_trace_netlink_extack(__msg);				\
122 								\
123 	if (__extack) {						\
124 		__extack->_msg = __msg;				\
125 		__extack->bad_attr = (attr);			\
126 		__extack->policy = (pol);			\
127 	}							\
128 } while (0)
129 
130 #define NL_SET_ERR_MSG_ATTR(extack, attr, msg)		\
131 	NL_SET_ERR_MSG_ATTR_POL(extack, attr, NULL, msg)
132 
133 #define NL_SET_ERR_ATTR_MISS(extack, nest, type)  do {	\
134 	struct netlink_ext_ack *__extack = (extack);	\
135 							\
136 	if (__extack) {					\
137 		__extack->miss_nest = (nest);		\
138 		__extack->miss_type = (type);		\
139 	}						\
140 } while (0)
141 
142 #define NL_REQ_ATTR_CHECK(extack, nest, tb, type) ({		\
143 	struct nlattr **__tb = (tb);				\
144 	u32 __attr = (type);					\
145 	int __retval;						\
146 								\
147 	__retval = !__tb[__attr];				\
148 	if (__retval)						\
149 		NL_SET_ERR_ATTR_MISS((extack), (nest), __attr);	\
150 	__retval;						\
151 })
152 
nl_set_extack_cookie_u64(struct netlink_ext_ack * extack,u64 cookie)153 static inline void nl_set_extack_cookie_u64(struct netlink_ext_ack *extack,
154 					    u64 cookie)
155 {
156 	if (!extack)
157 		return;
158 	memcpy(extack->cookie, &cookie, sizeof(cookie));
159 	extack->cookie_len = sizeof(cookie);
160 }
161 
162 void netlink_kernel_release(struct sock *sk);
163 int __netlink_change_ngroups(struct sock *sk, unsigned int groups);
164 int netlink_change_ngroups(struct sock *sk, unsigned int groups);
165 void __netlink_clear_multicast_users(struct sock *sk, unsigned int group);
166 void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
167 		 const struct netlink_ext_ack *extack);
168 int netlink_has_listeners(struct sock *sk, unsigned int group);
169 bool netlink_strict_get_check(struct sk_buff *skb);
170 
171 int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 portid, int nonblock);
172 int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, __u32 portid,
173 		      __u32 group, gfp_t allocation);
174 int netlink_set_err(struct sock *ssk, __u32 portid, __u32 group, int code);
175 int netlink_register_notifier(struct notifier_block *nb);
176 int netlink_unregister_notifier(struct notifier_block *nb);
177 
178 /* finegrained unicast helpers: */
179 struct sock *netlink_getsockbyfilp(struct file *filp);
180 int netlink_attachskb(struct sock *sk, struct sk_buff *skb,
181 		      long *timeo, struct sock *ssk);
182 void netlink_detachskb(struct sock *sk, struct sk_buff *skb);
183 int netlink_sendskb(struct sock *sk, struct sk_buff *skb);
184 
185 static inline struct sk_buff *
netlink_skb_clone(struct sk_buff * skb,gfp_t gfp_mask)186 netlink_skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
187 {
188 	struct sk_buff *nskb;
189 
190 	nskb = skb_clone(skb, gfp_mask);
191 	if (!nskb)
192 		return NULL;
193 
194 	/* This is a large skb, set destructor callback to release head */
195 	if (is_vmalloc_addr(skb->head))
196 		nskb->destructor = skb->destructor;
197 
198 	return nskb;
199 }
200 
201 /*
202  *	skb should fit one page. This choice is good for headerless malloc.
203  *	But we should limit to 8K so that userspace does not have to
204  *	use enormous buffer sizes on recvmsg() calls just to avoid
205  *	MSG_TRUNC when PAGE_SIZE is very large.
206  */
207 #if PAGE_SIZE < 8192UL
208 #define NLMSG_GOODSIZE	SKB_WITH_OVERHEAD(PAGE_SIZE)
209 #else
210 #define NLMSG_GOODSIZE	SKB_WITH_OVERHEAD(8192UL)
211 #endif
212 
213 #define NLMSG_DEFAULT_SIZE (NLMSG_GOODSIZE - NLMSG_HDRLEN)
214 
215 
216 struct netlink_callback {
217 	struct sk_buff		*skb;
218 	const struct nlmsghdr	*nlh;
219 	int			(*dump)(struct sk_buff * skb,
220 					struct netlink_callback *cb);
221 	int			(*done)(struct netlink_callback *cb);
222 	void			*data;
223 	/* the module that dump function belong to */
224 	struct module		*module;
225 	struct netlink_ext_ack	*extack;
226 	u16			family;
227 	u16			answer_flags;
228 	u32			min_dump_alloc;
229 	unsigned int		prev_seq, seq;
230 	bool			strict_check;
231 	union {
232 		u8		ctx[48];
233 
234 		/* args is deprecated. Cast a struct over ctx instead
235 		 * for proper type safety.
236 		 */
237 		long		args[6];
238 	};
239 };
240 
241 struct netlink_notify {
242 	struct net *net;
243 	u32 portid;
244 	int protocol;
245 };
246 
247 struct nlmsghdr *
248 __nlmsg_put(struct sk_buff *skb, u32 portid, u32 seq, int type, int len, int flags);
249 
250 struct netlink_dump_control {
251 	int (*start)(struct netlink_callback *);
252 	int (*dump)(struct sk_buff *skb, struct netlink_callback *);
253 	int (*done)(struct netlink_callback *);
254 	void *data;
255 	struct module *module;
256 	u32 min_dump_alloc;
257 };
258 
259 int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
260 				const struct nlmsghdr *nlh,
261 				struct netlink_dump_control *control);
netlink_dump_start(struct sock * ssk,struct sk_buff * skb,const struct nlmsghdr * nlh,struct netlink_dump_control * control)262 static inline int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
263 				     const struct nlmsghdr *nlh,
264 				     struct netlink_dump_control *control)
265 {
266 	if (!control->module)
267 		control->module = THIS_MODULE;
268 
269 	return __netlink_dump_start(ssk, skb, nlh, control);
270 }
271 
272 struct netlink_tap {
273 	struct net_device *dev;
274 	struct module *module;
275 	struct list_head list;
276 };
277 
278 int netlink_add_tap(struct netlink_tap *nt);
279 int netlink_remove_tap(struct netlink_tap *nt);
280 
281 bool __netlink_ns_capable(const struct netlink_skb_parms *nsp,
282 			  struct user_namespace *ns, int cap);
283 bool netlink_ns_capable(const struct sk_buff *skb,
284 			struct user_namespace *ns, int cap);
285 bool netlink_capable(const struct sk_buff *skb, int cap);
286 bool netlink_net_capable(const struct sk_buff *skb, int cap);
287 
288 #endif	/* __LINUX_NETLINK_H */
289