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 	void            (*release) (struct sock *sk, unsigned long *groups);
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 #define NETLINK_MAX_FMTMSG_LEN	80
68 
69 /**
70  * struct netlink_ext_ack - netlink extended ACK report struct
71  * @_msg: message string to report - don't access directly, use
72  *	%NL_SET_ERR_MSG
73  * @bad_attr: attribute with error
74  * @policy: policy for a bad attribute
75  * @miss_type: attribute type which was missing
76  * @miss_nest: nest missing an attribute (%NULL if missing top level attr)
77  * @cookie: cookie data to return to userspace (for success)
78  * @cookie_len: actual cookie data length
79  * @_msg_buf: output buffer for formatted message strings - don't access
80  *	directly, use %NL_SET_ERR_MSG_FMT
81  */
82 struct netlink_ext_ack {
83 	const char *_msg;
84 	const struct nlattr *bad_attr;
85 	const struct nla_policy *policy;
86 	const struct nlattr *miss_nest;
87 	u16 miss_type;
88 	u8 cookie[NETLINK_MAX_COOKIE_LEN];
89 	u8 cookie_len;
90 	char _msg_buf[NETLINK_MAX_FMTMSG_LEN];
91 };
92 
93 /* Always use this macro, this allows later putting the
94  * message into a separate section or such for things
95  * like translation or listing all possible messages.
96  * If string formatting is needed use NL_SET_ERR_MSG_FMT.
97  */
98 #define NL_SET_ERR_MSG(extack, msg) do {		\
99 	static const char __msg[] = msg;		\
100 	struct netlink_ext_ack *__extack = (extack);	\
101 							\
102 	do_trace_netlink_extack(__msg);			\
103 							\
104 	if (__extack)					\
105 		__extack->_msg = __msg;			\
106 } while (0)
107 
108 /* We splice fmt with %s at each end even in the snprintf so that both calls
109  * can use the same string constant, avoiding its duplication in .ro
110  */
111 #define NL_SET_ERR_MSG_FMT(extack, fmt, args...) do {			       \
112 	struct netlink_ext_ack *__extack = (extack);			       \
113 									       \
114 	if (!__extack)							       \
115 		break;							       \
116 	if (snprintf(__extack->_msg_buf, NETLINK_MAX_FMTMSG_LEN,	       \
117 		     "%s" fmt "%s", "", ##args, "") >=			       \
118 	    NETLINK_MAX_FMTMSG_LEN)					       \
119 		net_warn_ratelimited("%s" fmt "%s", "truncated extack: ",      \
120 				     ##args, "\n");			       \
121 									       \
122 	do_trace_netlink_extack(__extack->_msg_buf);			       \
123 									       \
124 	__extack->_msg = __extack->_msg_buf;				       \
125 } while (0)
126 
127 #define NL_SET_ERR_MSG_MOD(extack, msg)			\
128 	NL_SET_ERR_MSG((extack), KBUILD_MODNAME ": " msg)
129 
130 #define NL_SET_ERR_MSG_FMT_MOD(extack, fmt, args...)	\
131 	NL_SET_ERR_MSG_FMT((extack), KBUILD_MODNAME ": " fmt, ##args)
132 
133 #define NL_SET_ERR_MSG_WEAK(extack, msg) do {		\
134 	if ((extack) && !(extack)->_msg)		\
135 		NL_SET_ERR_MSG((extack), msg);		\
136 } while (0)
137 
138 #define NL_SET_ERR_MSG_WEAK_MOD(extack, msg) do {	\
139 	if ((extack) && !(extack)->_msg)		\
140 		NL_SET_ERR_MSG_MOD((extack), msg);	\
141 } while (0)
142 
143 #define NL_SET_BAD_ATTR_POLICY(extack, attr, pol) do {	\
144 	if ((extack)) {					\
145 		(extack)->bad_attr = (attr);		\
146 		(extack)->policy = (pol);		\
147 	}						\
148 } while (0)
149 
150 #define NL_SET_BAD_ATTR(extack, attr) NL_SET_BAD_ATTR_POLICY(extack, attr, NULL)
151 
152 #define NL_SET_ERR_MSG_ATTR_POL(extack, attr, pol, msg) do {	\
153 	static const char __msg[] = msg;			\
154 	struct netlink_ext_ack *__extack = (extack);		\
155 								\
156 	do_trace_netlink_extack(__msg);				\
157 								\
158 	if (__extack) {						\
159 		__extack->_msg = __msg;				\
160 		__extack->bad_attr = (attr);			\
161 		__extack->policy = (pol);			\
162 	}							\
163 } while (0)
164 
165 #define NL_SET_ERR_MSG_ATTR_POL_FMT(extack, attr, pol, fmt, args...) do {	\
166 	struct netlink_ext_ack *__extack = (extack);				\
167 										\
168 	if (!__extack)								\
169 		break;								\
170 										\
171 	if (snprintf(__extack->_msg_buf, NETLINK_MAX_FMTMSG_LEN,		\
172 		     "%s" fmt "%s", "", ##args, "") >=				\
173 	    NETLINK_MAX_FMTMSG_LEN)						\
174 		net_warn_ratelimited("%s" fmt "%s", "truncated extack: ",       \
175 				     ##args, "\n");				\
176 										\
177 	do_trace_netlink_extack(__extack->_msg_buf);				\
178 										\
179 	__extack->_msg = __extack->_msg_buf;					\
180 	__extack->bad_attr = (attr);						\
181 	__extack->policy = (pol);						\
182 } while (0)
183 
184 #define NL_SET_ERR_MSG_ATTR(extack, attr, msg)		\
185 	NL_SET_ERR_MSG_ATTR_POL(extack, attr, NULL, msg)
186 
187 #define NL_SET_ERR_MSG_ATTR_FMT(extack, attr, msg, args...) \
188 	NL_SET_ERR_MSG_ATTR_POL_FMT(extack, attr, NULL, msg, ##args)
189 
190 #define NL_SET_ERR_ATTR_MISS(extack, nest, type)  do {	\
191 	struct netlink_ext_ack *__extack = (extack);	\
192 							\
193 	if (__extack) {					\
194 		__extack->miss_nest = (nest);		\
195 		__extack->miss_type = (type);		\
196 	}						\
197 } while (0)
198 
199 #define NL_REQ_ATTR_CHECK(extack, nest, tb, type) ({		\
200 	struct nlattr **__tb = (tb);				\
201 	u32 __attr = (type);					\
202 	int __retval;						\
203 								\
204 	__retval = !__tb[__attr];				\
205 	if (__retval)						\
206 		NL_SET_ERR_ATTR_MISS((extack), (nest), __attr);	\
207 	__retval;						\
208 })
209 
nl_set_extack_cookie_u64(struct netlink_ext_ack * extack,u64 cookie)210 static inline void nl_set_extack_cookie_u64(struct netlink_ext_ack *extack,
211 					    u64 cookie)
212 {
213 	if (!extack)
214 		return;
215 	memcpy(extack->cookie, &cookie, sizeof(cookie));
216 	extack->cookie_len = sizeof(cookie);
217 }
218 
219 void netlink_kernel_release(struct sock *sk);
220 int __netlink_change_ngroups(struct sock *sk, unsigned int groups);
221 int netlink_change_ngroups(struct sock *sk, unsigned int groups);
222 void __netlink_clear_multicast_users(struct sock *sk, unsigned int group);
223 void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
224 		 const struct netlink_ext_ack *extack);
225 int netlink_has_listeners(struct sock *sk, unsigned int group);
226 bool netlink_strict_get_check(struct sk_buff *skb);
227 
228 int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 portid, int nonblock);
229 int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, __u32 portid,
230 		      __u32 group, gfp_t allocation);
231 int netlink_broadcast_filtered(struct sock *ssk, struct sk_buff *skb,
232 			       __u32 portid, __u32 group, gfp_t allocation,
233 			       int (*filter)(struct sock *dsk,
234 					     struct sk_buff *skb, void *data),
235 			       void *filter_data);
236 int netlink_set_err(struct sock *ssk, __u32 portid, __u32 group, int code);
237 int netlink_register_notifier(struct notifier_block *nb);
238 int netlink_unregister_notifier(struct notifier_block *nb);
239 
240 /* finegrained unicast helpers: */
241 struct sock *netlink_getsockbyfilp(struct file *filp);
242 int netlink_attachskb(struct sock *sk, struct sk_buff *skb,
243 		      long *timeo, struct sock *ssk);
244 void netlink_detachskb(struct sock *sk, struct sk_buff *skb);
245 int netlink_sendskb(struct sock *sk, struct sk_buff *skb);
246 
247 static inline struct sk_buff *
netlink_skb_clone(struct sk_buff * skb,gfp_t gfp_mask)248 netlink_skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
249 {
250 	struct sk_buff *nskb;
251 
252 	nskb = skb_clone(skb, gfp_mask);
253 	if (!nskb)
254 		return NULL;
255 
256 	/* This is a large skb, set destructor callback to release head */
257 	if (is_vmalloc_addr(skb->head))
258 		nskb->destructor = skb->destructor;
259 
260 	return nskb;
261 }
262 
263 /*
264  *	skb should fit one page. This choice is good for headerless malloc.
265  *	But we should limit to 8K so that userspace does not have to
266  *	use enormous buffer sizes on recvmsg() calls just to avoid
267  *	MSG_TRUNC when PAGE_SIZE is very large.
268  */
269 #if PAGE_SIZE < 8192UL
270 #define NLMSG_GOODSIZE	SKB_WITH_OVERHEAD(PAGE_SIZE)
271 #else
272 #define NLMSG_GOODSIZE	SKB_WITH_OVERHEAD(8192UL)
273 #endif
274 
275 #define NLMSG_DEFAULT_SIZE (NLMSG_GOODSIZE - NLMSG_HDRLEN)
276 
277 
278 struct netlink_callback {
279 	struct sk_buff		*skb;
280 	const struct nlmsghdr	*nlh;
281 	int			(*dump)(struct sk_buff * skb,
282 					struct netlink_callback *cb);
283 	int			(*done)(struct netlink_callback *cb);
284 	void			*data;
285 	/* the module that dump function belong to */
286 	struct module		*module;
287 	struct netlink_ext_ack	*extack;
288 	u16			family;
289 	u16			answer_flags;
290 	u32			min_dump_alloc;
291 	unsigned int		prev_seq, seq;
292 	bool			strict_check;
293 	union {
294 		u8		ctx[48];
295 
296 		/* args is deprecated. Cast a struct over ctx instead
297 		 * for proper type safety.
298 		 */
299 		long		args[6];
300 	};
301 };
302 
303 #define NL_ASSERT_DUMP_CTX_FITS(type_name)				\
304 	BUILD_BUG_ON(sizeof(type_name) >				\
305 		     sizeof_field(struct netlink_callback, ctx))
306 
307 struct netlink_notify {
308 	struct net *net;
309 	u32 portid;
310 	int protocol;
311 };
312 
313 struct nlmsghdr *
314 __nlmsg_put(struct sk_buff *skb, u32 portid, u32 seq, int type, int len, int flags);
315 
316 struct netlink_dump_control {
317 	int (*start)(struct netlink_callback *);
318 	int (*dump)(struct sk_buff *skb, struct netlink_callback *);
319 	int (*done)(struct netlink_callback *);
320 	struct netlink_ext_ack *extack;
321 	void *data;
322 	struct module *module;
323 	u32 min_dump_alloc;
324 };
325 
326 int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
327 				const struct nlmsghdr *nlh,
328 				struct netlink_dump_control *control);
netlink_dump_start(struct sock * ssk,struct sk_buff * skb,const struct nlmsghdr * nlh,struct netlink_dump_control * control)329 static inline int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
330 				     const struct nlmsghdr *nlh,
331 				     struct netlink_dump_control *control)
332 {
333 	if (!control->module)
334 		control->module = THIS_MODULE;
335 
336 	return __netlink_dump_start(ssk, skb, nlh, control);
337 }
338 
339 struct netlink_tap {
340 	struct net_device *dev;
341 	struct module *module;
342 	struct list_head list;
343 };
344 
345 int netlink_add_tap(struct netlink_tap *nt);
346 int netlink_remove_tap(struct netlink_tap *nt);
347 
348 bool __netlink_ns_capable(const struct netlink_skb_parms *nsp,
349 			  struct user_namespace *ns, int cap);
350 bool netlink_ns_capable(const struct sk_buff *skb,
351 			struct user_namespace *ns, int cap);
352 bool netlink_capable(const struct sk_buff *skb, int cap);
353 bool netlink_net_capable(const struct sk_buff *skb, int cap);
354 
355 #endif	/* __LINUX_NETLINK_H */
356