netlink.h

  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
 12struct net;
 13
 14void do_trace_netlink_extack(const char *msg);
 15
 16static inline struct nlmsghdr *nlmsg_hdr(const struct sk_buff *skb)
 17{
 18	return (struct nlmsghdr *)skb->data;
 19}
 20
 21enum netlink_skb_flags {
 22	NETLINK_SKB_DST		= 0x8,	/* Dst set in sendto or sendmsg */
 23};
 24
 25struct 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#define NETLINK_CTX_SIZE	48
 38
 39
 40void netlink_table_grab(void);
 41void netlink_table_ungrab(void);
 42
 43#define NL_CFG_F_NONROOT_RECV	(1 << 0)
 44#define NL_CFG_F_NONROOT_SEND	(1 << 1)
 45
 46/* optional Netlink kernel configuration parameters */
 47struct netlink_kernel_cfg {
 48	unsigned int	groups;
 49	unsigned int	flags;
 50	void		(*input)(struct sk_buff *skb);
 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
 56struct sock *__netlink_kernel_create(struct net *net, int unit,
 57					    struct module *module,
 58					    struct netlink_kernel_cfg *cfg);
 59static inline struct sock *
 60netlink_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	8
 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 */
 82struct 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
210static inline void nl_set_extack_cookie_u64(struct netlink_ext_ack *extack,
211					    u64 cookie)
212{
213	if (!extack)
214		return;
215	BUILD_BUG_ON(sizeof(extack->cookie) < sizeof(cookie));
216	memcpy(extack->cookie, &cookie, sizeof(cookie));
217	extack->cookie_len = sizeof(cookie);
218}
219
220void netlink_kernel_release(struct sock *sk);
221int __netlink_change_ngroups(struct sock *sk, unsigned int groups);
222int netlink_change_ngroups(struct sock *sk, unsigned int groups);
223void __netlink_clear_multicast_users(struct sock *sk, unsigned int group);
224void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
225		 const struct netlink_ext_ack *extack);
226int netlink_has_listeners(struct sock *sk, unsigned int group);
227bool netlink_strict_get_check(struct sk_buff *skb);
228
229int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 portid, int nonblock);
230int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, __u32 portid,
231		      __u32 group, gfp_t allocation);
232
233typedef int (*netlink_filter_fn)(struct sock *dsk, struct sk_buff *skb, void *data);
234
235int netlink_broadcast_filtered(struct sock *ssk, struct sk_buff *skb,
236			       __u32 portid, __u32 group, gfp_t allocation,
237			       netlink_filter_fn filter,
238			       void *filter_data);
239int netlink_set_err(struct sock *ssk, __u32 portid, __u32 group, int code);
240int netlink_register_notifier(struct notifier_block *nb);
241int netlink_unregister_notifier(struct notifier_block *nb);
242
243/* finegrained unicast helpers: */
244struct sock *netlink_getsockbyfd(int fd);
245int netlink_attachskb(struct sock *sk, struct sk_buff *skb,
246		      long *timeo, struct sock *ssk);
247void netlink_detachskb(struct sock *sk, struct sk_buff *skb);
248int netlink_sendskb(struct sock *sk, struct sk_buff *skb);
249
250static inline struct sk_buff *
251netlink_skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
252{
253	struct sk_buff *nskb;
254
255	nskb = skb_clone(skb, gfp_mask);
256	if (!nskb)
257		return NULL;
258
259	/* This is a large skb, set destructor callback to release head */
260	if (is_vmalloc_addr(skb->head))
261		nskb->destructor = skb->destructor;
262
263	return nskb;
264}
265
266/*
267 *	skb should fit one page. This choice is good for headerless malloc.
268 *	But we should limit to 8K so that userspace does not have to
269 *	use enormous buffer sizes on recvmsg() calls just to avoid
270 *	MSG_TRUNC when PAGE_SIZE is very large.
271 */
272#if PAGE_SIZE < 8192UL
273#define NLMSG_GOODSIZE	SKB_WITH_OVERHEAD(PAGE_SIZE)
274#else
275#define NLMSG_GOODSIZE	SKB_WITH_OVERHEAD(8192UL)
276#endif
277
278#define NLMSG_DEFAULT_SIZE (NLMSG_GOODSIZE - NLMSG_HDRLEN)
279
280
281struct netlink_callback {
282	struct sk_buff		*skb;
283	const struct nlmsghdr	*nlh;
284	int			(*dump)(struct sk_buff * skb,
285					struct netlink_callback *cb);
286	int			(*done)(struct netlink_callback *cb);
287	void			*data;
288	/* the module that dump function belong to */
289	struct module		*module;
290	struct netlink_ext_ack	*extack;
291	u16			family;
292	u16			answer_flags;
293	u32			min_dump_alloc;
294	unsigned int		prev_seq, seq;
295	int			flags;
296	bool			strict_check;
297	union {
298		u8		ctx[NETLINK_CTX_SIZE];
299
300		/* args is deprecated. Cast a struct over ctx instead
301		 * for proper type safety.
302		 */
303		long		args[6];
304	};
305};
306
307#define NL_ASSERT_CTX_FITS(type_name)					\
308	BUILD_BUG_ON(sizeof(type_name) >				\
309		     sizeof_field(struct netlink_callback, ctx))
310
311struct netlink_notify {
312	struct net *net;
313	u32 portid;
314	int protocol;
315};
316
317struct nlmsghdr *
318__nlmsg_put(struct sk_buff *skb, u32 portid, u32 seq, int type, int len, int flags);
319
320struct netlink_dump_control {
321	int (*start)(struct netlink_callback *);
322	int (*dump)(struct sk_buff *skb, struct netlink_callback *);
323	int (*done)(struct netlink_callback *);
324	struct netlink_ext_ack *extack;
325	void *data;
326	struct module *module;
327	u32 min_dump_alloc;
328	int flags;
329};
330
331int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
332				const struct nlmsghdr *nlh,
333				struct netlink_dump_control *control);
334static inline int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
335				     const struct nlmsghdr *nlh,
336				     struct netlink_dump_control *control)
337{
338	if (!control->module)
339		control->module = THIS_MODULE;
340
341	return __netlink_dump_start(ssk, skb, nlh, control);
342}
343
344struct netlink_tap {
345	struct net_device *dev;
346	struct module *module;
347	struct list_head list;
348};
349
350int netlink_add_tap(struct netlink_tap *nt);
351int netlink_remove_tap(struct netlink_tap *nt);
352
353bool __netlink_ns_capable(const struct netlink_skb_parms *nsp,
354			  struct user_namespace *ns, int cap);
355bool netlink_ns_capable(const struct sk_buff *skb,
356			struct user_namespace *ns, int cap);
357bool netlink_capable(const struct sk_buff *skb, int cap);
358bool netlink_net_capable(const struct sk_buff *skb, int cap);
359struct sk_buff *netlink_alloc_large_skb(unsigned int size, int broadcast);
360
361#endif	/* __LINUX_NETLINK_H */