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_DST         = 0x8,  /* Dst set in sendto or sendmsg */
  21};
  22
  23struct 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
  37void netlink_table_grab(void);
  38void 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 */
  44struct 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
  54struct sock *__netlink_kernel_create(struct net *net, int unit,
  55                                            struct module *module,
  56                                            struct netlink_kernel_cfg *cfg);
  57static inline struct sock *
  58netlink_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 */
  74struct 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
 113static 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
 122void netlink_kernel_release(struct sock *sk);
 123int __netlink_change_ngroups(struct sock *sk, unsigned int groups);
 124int netlink_change_ngroups(struct sock *sk, unsigned int groups);
 125void __netlink_clear_multicast_users(struct sock *sk, unsigned int group);
 126void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
 127                 const struct netlink_ext_ack *extack);
 128int netlink_has_listeners(struct sock *sk, unsigned int group);
 129bool netlink_strict_get_check(struct sk_buff *skb);
 130
 131int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 portid, int nonblock);
 132int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, __u32 portid,
 133                      __u32 group, gfp_t allocation);
 134int 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);
 138int netlink_set_err(struct sock *ssk, __u32 portid, __u32 group, int code);
 139int netlink_register_notifier(struct notifier_block *nb);
 140int netlink_unregister_notifier(struct notifier_block *nb);
 141
 142/* finegrained unicast helpers: */
 143struct sock *netlink_getsockbyfilp(struct file *filp);
 144int netlink_attachskb(struct sock *sk, struct sk_buff *skb,
 145                      long *timeo, struct sock *ssk);
 146void netlink_detachskb(struct sock *sk, struct sk_buff *skb);
 147int netlink_sendskb(struct sock *sk, struct sk_buff *skb);
 148
 149static inline struct sk_buff *
 150netlink_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
 180struct 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        long                    args[6];
 196};
 197
 198struct netlink_notify {
 199        struct net *net;
 200        u32 portid;
 201        int protocol;
 202};
 203
 204struct nlmsghdr *
 205__nlmsg_put(struct sk_buff *skb, u32 portid, u32 seq, int type, int len, int flags);
 206
 207struct netlink_dump_control {
 208        int (*start)(struct netlink_callback *);
 209        int (*dump)(struct sk_buff *skb, struct netlink_callback *);
 210        int (*done)(struct netlink_callback *);
 211        void *data;
 212        struct module *module;
 213        u16 min_dump_alloc;
 214};
 215
 216int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
 217                                const struct nlmsghdr *nlh,
 218                                struct netlink_dump_control *control);
 219static inline int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
 220                                     const struct nlmsghdr *nlh,
 221                                     struct netlink_dump_control *control)
 222{
 223        if (!control->module)
 224                control->module = THIS_MODULE;
 225
 226        return __netlink_dump_start(ssk, skb, nlh, control);
 227}
 228
 229struct netlink_tap {
 230        struct net_device *dev;
 231        struct module *module;
 232        struct list_head list;
 233};
 234
 235int netlink_add_tap(struct netlink_tap *nt);
 236int netlink_remove_tap(struct netlink_tap *nt);
 237
 238bool __netlink_ns_capable(const struct netlink_skb_parms *nsp,
 239                          struct user_namespace *ns, int cap);
 240bool netlink_ns_capable(const struct sk_buff *skb,
 241                        struct user_namespace *ns, int cap);
 242bool netlink_capable(const struct sk_buff *skb, int cap);
 243bool netlink_net_capable(const struct sk_buff *skb, int cap);
 244
 245#endif  /* __LINUX_NETLINK_H */
 246
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