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
  37extern void netlink_table_grab(void);
  38extern 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 */
  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
  54extern struct 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
 113extern void netlink_kernel_release(struct sock *sk);
 114extern int __netlink_change_ngroups(struct sock *sk, unsigned int groups);
 115extern int netlink_change_ngroups(struct sock *sk, unsigned int groups);
 116extern void __netlink_clear_multicast_users(struct sock *sk, unsigned int group);
 117extern void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
 118                        const struct netlink_ext_ack *extack);
 119extern int netlink_has_listeners(struct sock *sk, unsigned int group);
 120
 121extern int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 portid, int nonblock);
 122extern int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, __u32 portid,
 123                             __u32 group, gfp_t allocation);
 124extern 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);
 128extern int netlink_set_err(struct sock *ssk, __u32 portid, __u32 group, int code);
 129extern int netlink_register_notifier(struct notifier_block *nb);
 130extern int netlink_unregister_notifier(struct notifier_block *nb);
 131
 132/* finegrained unicast helpers: */
 133struct sock *netlink_getsockbyfilp(struct file *filp);
 134int netlink_attachskb(struct sock *sk, struct sk_buff *skb,
 135                      long *timeo, struct sock *ssk);
 136void netlink_detachskb(struct sock *sk, struct sk_buff *skb);
 137int netlink_sendskb(struct sock *sk, struct sk_buff *skb);
 138
 139static inline struct sk_buff *
 140netlink_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
 170struct netlink_callback {
 171        struct sk_buff          *skb;
 172        const struct nlmsghdr   *nlh;
 173        int                     (*dump)(struct sk_buff * skb,
 174                                        struct netlink_callback *cb);
 175        int                     (*done)(struct netlink_callback *cb);
 176        void                    *data;
 177        /* the module that dump function belong to */
 178        struct module           *module;
 179        struct netlink_ext_ack  *extack;
 180        u16                     family;
 181        u16                     min_dump_alloc;
 182        bool                    strict_check;
 183        u16                     answer_flags;
 184        unsigned int            prev_seq, seq;
 185        long                    args[6];
 186};
 187
 188struct netlink_notify {
 189        struct net *net;
 190        u32 portid;
 191        int protocol;
 192};
 193
 194struct nlmsghdr *
 195__nlmsg_put(struct sk_buff *skb, u32 portid, u32 seq, int type, int len, int flags);
 196
 197struct netlink_dump_control {
 198        int (*start)(struct netlink_callback *);
 199        int (*dump)(struct sk_buff *skb, struct netlink_callback *);
 200        int (*done)(struct netlink_callback *);
 201        void *data;
 202        struct module *module;
 203        u16 min_dump_alloc;
 204};
 205
 206extern int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
 207                                const struct nlmsghdr *nlh,
 208                                struct netlink_dump_control *control);
 209static inline int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
 210                                     const struct nlmsghdr *nlh,
 211                                     struct netlink_dump_control *control)
 212{
 213        if (!control->module)
 214                control->module = THIS_MODULE;
 215
 216        return __netlink_dump_start(ssk, skb, nlh, control);
 217}
 218
 219struct netlink_tap {
 220        struct net_device *dev;
 221        struct module *module;
 222        struct list_head list;
 223};
 224
 225extern int netlink_add_tap(struct netlink_tap *nt);
 226extern int netlink_remove_tap(struct netlink_tap *nt);
 227
 228bool __netlink_ns_capable(const struct netlink_skb_parms *nsp,
 229                          struct user_namespace *ns, int cap);
 230bool netlink_ns_capable(const struct sk_buff *skb,
 231                        struct user_namespace *ns, int cap);
 232bool netlink_capable(const struct sk_buff *skb, int cap);
 233bool netlink_net_capable(const struct sk_buff *skb, int cap);
 234
 235#endif  /* __LINUX_NETLINK_H */
 236
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