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  * @cookie: cookie data to return to userspace (for success)
  72  * @cookie_len: actual cookie data length
  73  */
  74 struct netlink_ext_ack {
  75         const char *_msg;
  76         const struct nlattr *bad_attr;
  77         u8 cookie[NETLINK_MAX_COOKIE_LEN];
  78         u8 cookie_len;
  79 };
  80
  81 /* Always use this macro, this allows later putting the
  82  * message into a separate section or such for things
  83  * like translation or listing all possible messages.
  84  * Currently string formatting is not supported (due
  85  * to the lack of an output buffer.)
  86  */
  87 #define NL_SET_ERR_MSG(extack, msg) do {                \
  88         static const char __msg[] = msg;                \
  89         struct netlink_ext_ack *__extack = (extack);    \
  90                                                         \
  91         if (__extack)                                   \
  92                 __extack->_msg = __msg;                 \
  93 } while (0)
  94
  95 #define NL_SET_ERR_MSG_MOD(extack, msg)                 \
  96         NL_SET_ERR_MSG((extack), KBUILD_MODNAME ": " msg)
  97
  98 #define NL_SET_BAD_ATTR(extack, attr) do {              \
  99         if ((extack))                                   \
 100                 (extack)->bad_attr = (attr);            \
 101 } while (0)
 102
 103 #define NL_SET_ERR_MSG_ATTR(extack, attr, msg) do {     \
 104         static const char __msg[] = msg;                \
 105         struct netlink_ext_ack *__extack = (extack);    \
 106                                                         \
 107         if (__extack) {                                 \
 108                 __extack->_msg = __msg;                 \
 109                 __extack->bad_attr = (attr);            \
 110         }                                               \
 111 } while (0)
 112
 113 static inline void nl_set_extack_cookie_u64(struct netlink_ext_ack *extack,
 114                                             u64 cookie)
 115 {
 116         u64 __cookie = cookie;
 117
 118         if (!extack)
 119                 return;
 120         memcpy(extack->cookie, &__cookie, sizeof(__cookie));
 121         extack->cookie_len = sizeof(__cookie);
 122 }
 123
 124 static inline void nl_set_extack_cookie_u32(struct netlink_ext_ack *extack,
 125                                             u32 cookie)
 126 {
 127         u32 __cookie = cookie;
 128
 129         if (!extack)
 130                 return;
 131         memcpy(extack->cookie, &__cookie, sizeof(__cookie));
 132         extack->cookie_len = sizeof(__cookie);
 133 }
 134
 135 void netlink_kernel_release(struct sock *sk);
 136 int __netlink_change_ngroups(struct sock *sk, unsigned int groups);
 137 int netlink_change_ngroups(struct sock *sk, unsigned int groups);
 138 void __netlink_clear_multicast_users(struct sock *sk, unsigned int group);
 139 void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
 140                  const struct netlink_ext_ack *extack);
 141 int netlink_has_listeners(struct sock *sk, unsigned int group);
 142 bool netlink_strict_get_check(struct sk_buff *skb);
 143
 144 int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 portid, int nonblock);
 145 int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, __u32 portid,
 146                       __u32 group, gfp_t allocation);
 147 int netlink_broadcast_filtered(struct sock *ssk, struct sk_buff *skb,
 148                                __u32 portid, __u32 group, gfp_t allocation,
 149                                int (*filter)(struct sock *dsk, struct sk_buff *skb, void *data),
 150                                void *filter_data);
 151 int netlink_set_err(struct sock *ssk, __u32 portid, __u32 group, int code);
 152 int netlink_register_notifier(struct notifier_block *nb);
 153 int netlink_unregister_notifier(struct notifier_block *nb);
 154
 155 /* finegrained unicast helpers: */
 156 struct sock *netlink_getsockbyfilp(struct file *filp);
 157 int netlink_attachskb(struct sock *sk, struct sk_buff *skb,
 158                       long *timeo, struct sock *ssk);
 159 void netlink_detachskb(struct sock *sk, struct sk_buff *skb);
 160 int netlink_sendskb(struct sock *sk, struct sk_buff *skb);
 161
 162 static inline struct sk_buff *
 163 netlink_skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
 164 {
 165         struct sk_buff *nskb;
 166
 167         nskb = skb_clone(skb, gfp_mask);
 168         if (!nskb)
 169                 return NULL;
 170
 171         /* This is a large skb, set destructor callback to release head */
 172         if (is_vmalloc_addr(skb->head))
 173                 nskb->destructor = skb->destructor;
 174
 175         return nskb;
 176 }
 177
 178 /*
 179  *      skb should fit one page. This choice is good for headerless malloc.
 180  *      But we should limit to 8K so that userspace does not have to
 181  *      use enormous buffer sizes on recvmsg() calls just to avoid
 182  *      MSG_TRUNC when PAGE_SIZE is very large.
 183  */
 184 #if PAGE_SIZE < 8192UL
 185 #define NLMSG_GOODSIZE  SKB_WITH_OVERHEAD(PAGE_SIZE)
 186 #else
 187 #define NLMSG_GOODSIZE  SKB_WITH_OVERHEAD(8192UL)
 188 #endif
 189
 190 #define NLMSG_DEFAULT_SIZE (NLMSG_GOODSIZE - NLMSG_HDRLEN)
 191
 192
 193 struct netlink_callback {
 194         struct sk_buff          *skb;
 195         const struct nlmsghdr   *nlh;
 196         int                     (*dump)(struct sk_buff * skb,
 197                                         struct netlink_callback *cb);
 198         int                     (*done)(struct netlink_callback *cb);
 199         void                    *data;
 200         /* the module that dump function belong to */
 201         struct module           *module;
 202         struct netlink_ext_ack  *extack;
 203         u16                     family;
 204         u16                     answer_flags;
 205         u32                     min_dump_alloc;
 206         unsigned int            prev_seq, seq;
 207         bool                    strict_check;
 208         union {
 209                 u8              ctx[48];
 210
 211                 /* args is deprecated. Cast a struct over ctx instead
 212                  * for proper type safety.
 213                  */
 214                 long            args[6];
 215         };
 216 };
 217
 218 struct netlink_notify {
 219         struct net *net;
 220         u32 portid;
 221         int protocol;
 222 };
 223
 224 struct nlmsghdr *
 225 __nlmsg_put(struct sk_buff *skb, u32 portid, u32 seq, int type, int len, int flags);
 226
 227 struct netlink_dump_control {
 228         int (*start)(struct netlink_callback *);
 229         int (*dump)(struct sk_buff *skb, struct netlink_callback *);
 230         int (*done)(struct netlink_callback *);
 231         void *data;
 232         struct module *module;
 233         u16 min_dump_alloc;
 234 };
 235
 236 int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
 237                                 const struct nlmsghdr *nlh,
 238                                 struct netlink_dump_control *control);
 239 static inline int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
 240                                      const struct nlmsghdr *nlh,
 241                                      struct netlink_dump_control *control)
 242 {
 243         if (!control->module)
 244                 control->module = THIS_MODULE;
 245
 246         return __netlink_dump_start(ssk, skb, nlh, control);
 247 }
 248
 249 struct netlink_tap {
 250         struct net_device *dev;
 251         struct module *module;
 252         struct list_head list;
 253 };
 254
 255 int netlink_add_tap(struct netlink_tap *nt);
 256 int netlink_remove_tap(struct netlink_tap *nt);
 257
 258 bool __netlink_ns_capable(const struct netlink_skb_parms *nsp,
 259                           struct user_namespace *ns, int cap);
 260 bool netlink_ns_capable(const struct sk_buff *skb,
 261                         struct user_namespace *ns, int cap);
 262 bool netlink_capable(const struct sk_buff *skb, int cap);
 263 bool netlink_net_capable(const struct sk_buff *skb, int cap);
 264
 265 #endif  /* __LINUX_NETLINK_H */