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         memcpy(extack->cookie, &__cookie, sizeof(__cookie));
 119         extack->cookie_len = sizeof(__cookie);
 120 }
 121
 122 void netlink_kernel_release(struct sock *sk);
 123 int __netlink_change_ngroups(struct sock *sk, unsigned int groups);
 124 int netlink_change_ngroups(struct sock *sk, unsigned int groups);
 125 void __netlink_clear_multicast_users(struct sock *sk, unsigned int group);
 126 void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
 127                  const struct netlink_ext_ack *extack);
 128 int netlink_has_listeners(struct sock *sk, unsigned int group);
 129 bool netlink_strict_get_check(struct sk_buff *skb);
 130
 131 int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 portid, int nonblock);
 132 int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, __u32 portid,
 133                       __u32 group, gfp_t allocation);
 134 int netlink_broadcast_filtered(struct sock *ssk, struct sk_buff *skb,
 135                                __u32 portid, __u32 group, gfp_t allocation,
 136                                int (*filter)(struct sock *dsk, struct sk_buff *skb, void *data),
 137                                void *filter_data);
 138 int netlink_set_err(struct sock *ssk, __u32 portid, __u32 group, int code);
 139 int netlink_register_notifier(struct notifier_block *nb);
 140 int netlink_unregister_notifier(struct notifier_block *nb);
 141
 142 /* finegrained unicast helpers: */
 143 struct sock *netlink_getsockbyfilp(struct file *filp);
 144 int netlink_attachskb(struct sock *sk, struct sk_buff *skb,
 145                       long *timeo, struct sock *ssk);
 146 void netlink_detachskb(struct sock *sk, struct sk_buff *skb);
 147 int netlink_sendskb(struct sock *sk, struct sk_buff *skb);
 148
 149 static inline struct sk_buff *
 150 netlink_skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
 151 {
 152         struct sk_buff *nskb;
 153
 154         nskb = skb_clone(skb, gfp_mask);
 155         if (!nskb)
 156                 return NULL;
 157
 158         /* This is a large skb, set destructor callback to release head */
 159         if (is_vmalloc_addr(skb->head))
 160                 nskb->destructor = skb->destructor;
 161
 162         return nskb;
 163 }
 164
 165 /*
 166  *      skb should fit one page. This choice is good for headerless malloc.
 167  *      But we should limit to 8K so that userspace does not have to
 168  *      use enormous buffer sizes on recvmsg() calls just to avoid
 169  *      MSG_TRUNC when PAGE_SIZE is very large.
 170  */
 171 #if PAGE_SIZE < 8192UL
 172 #define NLMSG_GOODSIZE  SKB_WITH_OVERHEAD(PAGE_SIZE)
 173 #else
 174 #define NLMSG_GOODSIZE  SKB_WITH_OVERHEAD(8192UL)
 175 #endif
 176
 177 #define NLMSG_DEFAULT_SIZE (NLMSG_GOODSIZE - NLMSG_HDRLEN)
 178
 179
 180 struct netlink_callback {
 181         struct sk_buff          *skb;
 182         const struct nlmsghdr   *nlh;
 183         int                     (*dump)(struct sk_buff * skb,
 184                                         struct netlink_callback *cb);
 185         int                     (*done)(struct netlink_callback *cb);
 186         void                    *data;
 187         /* the module that dump function belong to */
 188         struct module           *module;
 189         struct netlink_ext_ack  *extack;
 190         u16                     family;
 191         u16                     min_dump_alloc;
 192         bool                    strict_check;
 193         u16                     answer_flags;
 194         unsigned int            prev_seq, seq;
 195         union {
 196                 u8              ctx[48];
 197
 198                 /* args is deprecated. Cast a struct over ctx instead
 199                  * for proper type safety.
 200                  */
 201                 long            args[6];
 202         };
 203 };
 204
 205 struct netlink_notify {
 206         struct net *net;
 207         u32 portid;
 208         int protocol;
 209 };
 210
 211 struct nlmsghdr *
 212 __nlmsg_put(struct sk_buff *skb, u32 portid, u32 seq, int type, int len, int flags);
 213
 214 struct netlink_dump_control {
 215         int (*start)(struct netlink_callback *);
 216         int (*dump)(struct sk_buff *skb, struct netlink_callback *);
 217         int (*done)(struct netlink_callback *);
 218         void *data;
 219         struct module *module;
 220         u16 min_dump_alloc;
 221 };
 222
 223 int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
 224                                 const struct nlmsghdr *nlh,
 225                                 struct netlink_dump_control *control);
 226 static inline int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
 227                                      const struct nlmsghdr *nlh,
 228                                      struct netlink_dump_control *control)
 229 {
 230         if (!control->module)
 231                 control->module = THIS_MODULE;
 232
 233         return __netlink_dump_start(ssk, skb, nlh, control);
 234 }
 235
 236 struct netlink_tap {
 237         struct net_device *dev;
 238         struct module *module;
 239         struct list_head list;
 240 };
 241
 242 int netlink_add_tap(struct netlink_tap *nt);
 243 int netlink_remove_tap(struct netlink_tap *nt);
 244
 245 bool __netlink_ns_capable(const struct netlink_skb_parms *nsp,
 246                           struct user_namespace *ns, int cap);
 247 bool netlink_ns_capable(const struct sk_buff *skb,
 248                         struct user_namespace *ns, int cap);
 249 bool netlink_capable(const struct sk_buff *skb, int cap);
 250 bool netlink_net_capable(const struct sk_buff *skb, int cap);
 251
 252 #endif  /* __LINUX_NETLINK_H */