include/linux/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
  12 struct net;
  13
  14 static inline struct nlmsghdr *nlmsg_hdr(const struct sk_buff *skb)
  15 {
  16         return (struct nlmsghdr *)skb->data;
  17 }
  18
  19 enum netlink_skb_flags {
  20         NETLINK_SKB_DST         = 0x8,  /* Dst set in sendto or sendmsg */
  21 };
  22
  23 struct netlink_skb_parms {
  24         struct scm_creds        creds;          /* Skb credentials      */
  25         __u32                   portid;
  26         __u32                   dst_group;
  27         __u32                   flags;
  28         struct sock             *sk;
  29         bool                    nsid_is_set;
  30         int                     nsid;
  31 };
  32
  33 #define NETLINK_CB(skb)         (*(struct netlink_skb_parms*)&((skb)->cb))
  34 #define NETLINK_CREDS(skb)      (&NETLINK_CB((skb)).creds)
  35
  36
  37 void netlink_table_grab(void);
  38 void netlink_table_ungrab(void);
  39
  40 #define NL_CFG_F_NONROOT_RECV   (1 << 0)
  41 #define NL_CFG_F_NONROOT_SEND   (1 << 1)
  42
  43 /* optional Netlink kernel configuration parameters */
  44 struct netlink_kernel_cfg {
  45         unsigned int    groups;
  46         unsigned int    flags;
  47         void            (*input)(struct sk_buff *skb);
  48         struct mutex    *cb_mutex;
  49         int             (*bind)(struct net *net, int group);
  50         void            (*unbind)(struct net *net, int group);
  51         bool            (*compare)(struct net *net, struct sock *sk);
  52 };
  53
  54 struct sock *__netlink_kernel_create(struct net *net, int unit,
  55                                             struct module *module,
  56                                             struct netlink_kernel_cfg *cfg);
  57 static inline struct sock *
  58 netlink_kernel_create(struct net *net, int unit, struct netlink_kernel_cfg *cfg)
  59 {
  60         return __netlink_kernel_create(net, unit, THIS_MODULE, cfg);
  61 }
  62
  63 /* this can be increased when necessary - don't expose to userland */
  64 #define NETLINK_MAX_COOKIE_LEN  20
  65
  66 /**
  67  * struct netlink_ext_ack - netlink extended ACK report struct
  68  * @_msg: message string to report - don't access directly, use
  69  *      %NL_SET_ERR_MSG
  70  * @bad_attr: attribute with error
  71  * @policy: policy for a bad attribute
  72  * @cookie: cookie data to return to userspace (for success)
  73  * @cookie_len: actual cookie data length
  74  */
  75 struct netlink_ext_ack {
  76         const char *_msg;
  77         const struct nlattr *bad_attr;
  78         const struct nla_policy *policy;
  79         u8 cookie[NETLINK_MAX_COOKIE_LEN];
  80         u8 cookie_len;
  81 };
  82
  83 /* Always use this macro, this allows later putting the
  84  * message into a separate section or such for things
  85  * like translation or listing all possible messages.
  86  * Currently string formatting is not supported (due
  87  * to the lack of an output buffer.)
  88  */
  89 #define NL_SET_ERR_MSG(extack, msg) do {                \
  90         static const char __msg[] = msg;                \
  91         struct netlink_ext_ack *__extack = (extack);    \
  92                                                         \
  93         if (__extack)                                   \
  94                 __extack->_msg = __msg;                 \
  95 } while (0)
  96
  97 #define NL_SET_ERR_MSG_MOD(extack, msg)                 \
  98         NL_SET_ERR_MSG((extack), KBUILD_MODNAME ": " msg)
  99
 100 #define NL_SET_BAD_ATTR_POLICY(extack, attr, pol) do {  \
 101         if ((extack)) {                                 \
 102                 (extack)->bad_attr = (attr);            \
 103                 (extack)->policy = (pol);               \
 104         }                                               \
 105 } while (0)
 106
 107 #define NL_SET_BAD_ATTR(extack, attr) NL_SET_BAD_ATTR_POLICY(extack, attr, NULL)
 108
 109 #define NL_SET_ERR_MSG_ATTR_POL(extack, attr, pol, msg) do {    \
 110         static const char __msg[] = msg;                        \
 111         struct netlink_ext_ack *__extack = (extack);            \
 112                                                                 \
 113         if (__extack) {                                         \
 114                 __extack->_msg = __msg;                         \
 115                 __extack->bad_attr = (attr);                    \
 116                 __extack->policy = (pol);                       \
 117         }                                                       \
 118 } while (0)
 119
 120 #define NL_SET_ERR_MSG_ATTR(extack, attr, msg)          \
 121         NL_SET_ERR_MSG_ATTR_POL(extack, attr, NULL, msg)
 122
 123 static inline void nl_set_extack_cookie_u64(struct netlink_ext_ack *extack,
 124                                             u64 cookie)
 125 {
 126         u64 __cookie = cookie;
 127
 128         if (!extack)
 129                 return;
 130         memcpy(extack->cookie, &__cookie, sizeof(__cookie));
 131         extack->cookie_len = sizeof(__cookie);
 132 }
 133
 134 static inline void nl_set_extack_cookie_u32(struct netlink_ext_ack *extack,
 135                                             u32 cookie)
 136 {
 137         u32 __cookie = cookie;
 138
 139         if (!extack)
 140                 return;
 141         memcpy(extack->cookie, &__cookie, sizeof(__cookie));
 142         extack->cookie_len = sizeof(__cookie);
 143 }
 144
 145 void netlink_kernel_release(struct sock *sk);
 146 int __netlink_change_ngroups(struct sock *sk, unsigned int groups);
 147 int netlink_change_ngroups(struct sock *sk, unsigned int groups);
 148 void __netlink_clear_multicast_users(struct sock *sk, unsigned int group);
 149 void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
 150                  const struct netlink_ext_ack *extack);
 151 int netlink_has_listeners(struct sock *sk, unsigned int group);
 152 bool netlink_strict_get_check(struct sk_buff *skb);
 153
 154 int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 portid, int nonblock);
 155 int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, __u32 portid,
 156                       __u32 group, gfp_t allocation);
 157 int netlink_broadcast_filtered(struct sock *ssk, struct sk_buff *skb,
 158                                __u32 portid, __u32 group, gfp_t allocation,
 159                                int (*filter)(struct sock *dsk, struct sk_buff *skb, void *data),
 160                                void *filter_data);
 161 int netlink_set_err(struct sock *ssk, __u32 portid, __u32 group, int code);
 162 int netlink_register_notifier(struct notifier_block *nb);
 163 int netlink_unregister_notifier(struct notifier_block *nb);
 164
 165 /* finegrained unicast helpers: */
 166 struct sock *netlink_getsockbyfilp(struct file *filp);
 167 int netlink_attachskb(struct sock *sk, struct sk_buff *skb,
 168                       long *timeo, struct sock *ssk);
 169 void netlink_detachskb(struct sock *sk, struct sk_buff *skb);
 170 int netlink_sendskb(struct sock *sk, struct sk_buff *skb);
 171
 172 static inline struct sk_buff *
 173 netlink_skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
 174 {
 175         struct sk_buff *nskb;
 176
 177         nskb = skb_clone(skb, gfp_mask);
 178         if (!nskb)
 179                 return NULL;
 180
 181         /* This is a large skb, set destructor callback to release head */
 182         if (is_vmalloc_addr(skb->head))
 183                 nskb->destructor = skb->destructor;
 184
 185         return nskb;
 186 }
 187
 188 /*
 189  *      skb should fit one page. This choice is good for headerless malloc.
 190  *      But we should limit to 8K so that userspace does not have to
 191  *      use enormous buffer sizes on recvmsg() calls just to avoid
 192  *      MSG_TRUNC when PAGE_SIZE is very large.
 193  */
 194 #if PAGE_SIZE < 8192UL
 195 #define NLMSG_GOODSIZE  SKB_WITH_OVERHEAD(PAGE_SIZE)
 196 #else
 197 #define NLMSG_GOODSIZE  SKB_WITH_OVERHEAD(8192UL)
 198 #endif
 199
 200 #define NLMSG_DEFAULT_SIZE (NLMSG_GOODSIZE - NLMSG_HDRLEN)
 201
 202
 203 struct netlink_callback {
 204         struct sk_buff          *skb;
 205         const struct nlmsghdr   *nlh;
 206         int                     (*dump)(struct sk_buff * skb,
 207                                         struct netlink_callback *cb);
 208         int                     (*done)(struct netlink_callback *cb);
 209         void                    *data;
 210         /* the module that dump function belong to */
 211         struct module           *module;
 212         struct netlink_ext_ack  *extack;
 213         u16                     family;
 214         u16                     answer_flags;
 215         u32                     min_dump_alloc;
 216         unsigned int            prev_seq, seq;
 217         bool                    strict_check;
 218         union {
 219                 u8              ctx[48];
 220
 221                 /* args is deprecated. Cast a struct over ctx instead
 222                  * for proper type safety.
 223                  */
 224                 long            args[6];
 225         };
 226 };
 227
 228 struct netlink_notify {
 229         struct net *net;
 230         u32 portid;
 231         int protocol;
 232 };
 233
 234 struct nlmsghdr *
 235 __nlmsg_put(struct sk_buff *skb, u32 portid, u32 seq, int type, int len, int flags);
 236
 237 struct netlink_dump_control {
 238         int (*start)(struct netlink_callback *);
 239         int (*dump)(struct sk_buff *skb, struct netlink_callback *);
 240         int (*done)(struct netlink_callback *);
 241         void *data;
 242         struct module *module;
 243         u16 min_dump_alloc;
 244 };
 245
 246 int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
 247                                 const struct nlmsghdr *nlh,
 248                                 struct netlink_dump_control *control);
 249 static inline int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
 250                                      const struct nlmsghdr *nlh,
 251                                      struct netlink_dump_control *control)
 252 {
 253         if (!control->module)
 254                 control->module = THIS_MODULE;
 255
 256         return __netlink_dump_start(ssk, skb, nlh, control);
 257 }
 258
 259 struct netlink_tap {
 260         struct net_device *dev;
 261         struct module *module;
 262         struct list_head list;
 263 };
 264
 265 int netlink_add_tap(struct netlink_tap *nt);
 266 int netlink_remove_tap(struct netlink_tap *nt);
 267
 268 bool __netlink_ns_capable(const struct netlink_skb_parms *nsp,
 269                           struct user_namespace *ns, int cap);
 270 bool netlink_ns_capable(const struct sk_buff *skb,
 271                         struct user_namespace *ns, int cap);
 272 bool netlink_capable(const struct sk_buff *skb, int cap);
 273 bool netlink_net_capable(const struct sk_buff *skb, int cap);
 274
 275 #endif  /* __LINUX_NETLINK_H */