linux/include/linux/netlink.h
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   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
  14static inline struct nlmsghdr *nlmsg_hdr(const struct sk_buff *skb)
  15{
  16        return (struct nlmsghdr *)skb->data;
  17}
  18
  19enum netlink_skb_flags {
  20        NETLINK_SKB_MMAPED      = 0x1,  /* Packet data is mmaped */
  21        NETLINK_SKB_TX          = 0x2,  /* Packet was sent by userspace */
  22        NETLINK_SKB_DELIVERED   = 0x4,  /* Packet was delivered */
  23        NETLINK_SKB_DST         = 0x8,  /* Dst set in sendto or sendmsg */
  24};
  25
  26struct netlink_skb_parms {
  27        struct scm_creds        creds;          /* Skb credentials      */
  28        __u32                   portid;
  29        __u32                   dst_group;
  30        __u32                   flags;
  31        struct sock             *sk;
  32        bool                    nsid_is_set;
  33        int                     nsid;
  34};
  35
  36#define NETLINK_CB(skb)         (*(struct netlink_skb_parms*)&((skb)->cb))
  37#define NETLINK_CREDS(skb)      (&NETLINK_CB((skb)).creds)
  38
  39
  40extern void netlink_table_grab(void);
  41extern void 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        struct mutex    *cb_mutex;
  52        int             (*bind)(struct net *net, int group);
  53        void            (*unbind)(struct net *net, int group);
  54        bool            (*compare)(struct net *net, struct sock *sk);
  55};
  56
  57extern struct sock *__netlink_kernel_create(struct net *net, int unit,
  58                                            struct module *module,
  59                                            struct netlink_kernel_cfg *cfg);
  60static inline struct sock *
  61netlink_kernel_create(struct net *net, int unit, struct netlink_kernel_cfg *cfg)
  62{
  63        return __netlink_kernel_create(net, unit, THIS_MODULE, cfg);
  64}
  65
  66/* this can be increased when necessary - don't expose to userland */
  67#define NETLINK_MAX_COOKIE_LEN  20
  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 * @cookie: cookie data to return to userspace (for success)
  75 * @cookie_len: actual cookie data length
  76 */
  77struct netlink_ext_ack {
  78        const char *_msg;
  79        const struct nlattr *bad_attr;
  80        u8 cookie[NETLINK_MAX_COOKIE_LEN];
  81        u8 cookie_len;
  82};
  83
  84/* Always use this macro, this allows later putting the
  85 * message into a separate section or such for things
  86 * like translation or listing all possible messages.
  87 * Currently string formatting is not supported (due
  88 * to the lack of an output buffer.)
  89 */
  90#define NL_SET_ERR_MSG(extack, msg) do {                \
  91        static const char __msg[] = (msg);              \
  92        struct netlink_ext_ack *__extack = (extack);    \
  93                                                        \
  94        if (__extack)                                   \
  95                __extack->_msg = __msg;                 \
  96} while (0)
  97
  98#define NL_SET_ERR_MSG_MOD(extack, msg)                 \
  99        NL_SET_ERR_MSG((extack), KBUILD_MODNAME ": " msg)
 100
 101#define NL_SET_BAD_ATTR(extack, attr) do {              \
 102        if ((extack))                                   \
 103                (extack)->bad_attr = (attr);            \
 104} while (0)
 105
 106#define NL_SET_ERR_MSG_ATTR(extack, attr, msg) do {     \
 107        static const char __msg[] = (msg);              \
 108        struct netlink_ext_ack *__extack = (extack);    \
 109                                                        \
 110        if (__extack) {                                 \
 111                __extack->_msg = __msg;                 \
 112                __extack->bad_attr = (attr);            \
 113        }                                               \
 114} while (0)
 115
 116extern void netlink_kernel_release(struct sock *sk);
 117extern int __netlink_change_ngroups(struct sock *sk, unsigned int groups);
 118extern int netlink_change_ngroups(struct sock *sk, unsigned int groups);
 119extern void __netlink_clear_multicast_users(struct sock *sk, unsigned int group);
 120extern void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
 121                        const struct netlink_ext_ack *extack);
 122extern int netlink_has_listeners(struct sock *sk, unsigned int group);
 123
 124extern int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 portid, int nonblock);
 125extern int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, __u32 portid,
 126                             __u32 group, gfp_t allocation);
 127extern int netlink_broadcast_filtered(struct sock *ssk, struct sk_buff *skb,
 128        __u32 portid, __u32 group, gfp_t allocation,
 129        int (*filter)(struct sock *dsk, struct sk_buff *skb, void *data),
 130        void *filter_data);
 131extern int netlink_set_err(struct sock *ssk, __u32 portid, __u32 group, int code);
 132extern int netlink_register_notifier(struct notifier_block *nb);
 133extern int netlink_unregister_notifier(struct notifier_block *nb);
 134
 135/* finegrained unicast helpers: */
 136struct sock *netlink_getsockbyfilp(struct file *filp);
 137int netlink_attachskb(struct sock *sk, struct sk_buff *skb,
 138                      long *timeo, struct sock *ssk);
 139void netlink_detachskb(struct sock *sk, struct sk_buff *skb);
 140int netlink_sendskb(struct sock *sk, struct sk_buff *skb);
 141
 142static inline struct sk_buff *
 143netlink_skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
 144{
 145        struct sk_buff *nskb;
 146
 147        nskb = skb_clone(skb, gfp_mask);
 148        if (!nskb)
 149                return NULL;
 150
 151        /* This is a large skb, set destructor callback to release head */
 152        if (is_vmalloc_addr(skb->head))
 153                nskb->destructor = skb->destructor;
 154
 155        return nskb;
 156}
 157
 158/*
 159 *      skb should fit one page. This choice is good for headerless malloc.
 160 *      But we should limit to 8K so that userspace does not have to
 161 *      use enormous buffer sizes on recvmsg() calls just to avoid
 162 *      MSG_TRUNC when PAGE_SIZE is very large.
 163 */
 164#if PAGE_SIZE < 8192UL
 165#define NLMSG_GOODSIZE  SKB_WITH_OVERHEAD(PAGE_SIZE)
 166#else
 167#define NLMSG_GOODSIZE  SKB_WITH_OVERHEAD(8192UL)
 168#endif
 169
 170#define NLMSG_DEFAULT_SIZE (NLMSG_GOODSIZE - NLMSG_HDRLEN)
 171
 172
 173struct netlink_callback {
 174        struct sk_buff          *skb;
 175        const struct nlmsghdr   *nlh;
 176        int                     (*start)(struct netlink_callback *);
 177        int                     (*dump)(struct sk_buff * skb,
 178                                        struct netlink_callback *cb);
 179        int                     (*done)(struct netlink_callback *cb);
 180        void                    *data;
 181        /* the module that dump function belong to */
 182        struct module           *module;
 183        u16                     family;
 184        u16                     min_dump_alloc;
 185        unsigned int            prev_seq, seq;
 186        long                    args[6];
 187};
 188
 189struct netlink_notify {
 190        struct net *net;
 191        u32 portid;
 192        int protocol;
 193};
 194
 195struct nlmsghdr *
 196__nlmsg_put(struct sk_buff *skb, u32 portid, u32 seq, int type, int len, int flags);
 197
 198struct netlink_dump_control {
 199        int (*start)(struct netlink_callback *);
 200        int (*dump)(struct sk_buff *skb, struct netlink_callback *);
 201        int (*done)(struct netlink_callback *);
 202        void *data;
 203        struct module *module;
 204        u16 min_dump_alloc;
 205};
 206
 207extern int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
 208                                const struct nlmsghdr *nlh,
 209                                struct netlink_dump_control *control);
 210static inline int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
 211                                     const struct nlmsghdr *nlh,
 212                                     struct netlink_dump_control *control)
 213{
 214        if (!control->module)
 215                control->module = THIS_MODULE;
 216
 217        return __netlink_dump_start(ssk, skb, nlh, control);
 218}
 219
 220struct netlink_tap {
 221        struct net_device *dev;
 222        struct module *module;
 223        struct list_head list;
 224};
 225
 226extern int netlink_add_tap(struct netlink_tap *nt);
 227extern int netlink_remove_tap(struct netlink_tap *nt);
 228
 229bool __netlink_ns_capable(const struct netlink_skb_parms *nsp,
 230                          struct user_namespace *ns, int cap);
 231bool netlink_ns_capable(const struct sk_buff *skb,
 232                        struct user_namespace *ns, int cap);
 233bool netlink_capable(const struct sk_buff *skb, int cap);
 234bool netlink_net_capable(const struct sk_buff *skb, int cap);
 235
 236#endif  /* __LINUX_NETLINK_H */
 237
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