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