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_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
  26 struct 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
  40 extern void netlink_table_grab(void);
  41 extern 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 */
  47 struct 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
  57 extern struct sock *__netlink_kernel_create(struct net *net, int unit,
  58                                             struct module *module,
  59                                             struct netlink_kernel_cfg *cfg);
  60 static inline struct sock *
  61 netlink_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  */
  77 struct 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
 116 extern void netlink_kernel_release(struct sock *sk);
 117 extern int __netlink_change_ngroups(struct sock *sk, unsigned int groups);
 118 extern int netlink_change_ngroups(struct sock *sk, unsigned int groups);
 119 extern void __netlink_clear_multicast_users(struct sock *sk, unsigned int group);
 120 extern void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
 121                         const struct netlink_ext_ack *extack);
 122 extern int netlink_has_listeners(struct sock *sk, unsigned int group);
 123
 124 extern int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 portid, int nonblock);
 125 extern int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, __u32 portid,
 126                              __u32 group, gfp_t allocation);
 127 extern 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);
 131 extern int netlink_set_err(struct sock *ssk, __u32 portid, __u32 group, int code);
 132 extern int netlink_register_notifier(struct notifier_block *nb);
 133 extern int netlink_unregister_notifier(struct notifier_block *nb);
 134
 135 /* finegrained unicast helpers: */
 136 struct sock *netlink_getsockbyfilp(struct file *filp);
 137 int netlink_attachskb(struct sock *sk, struct sk_buff *skb,
 138                       long *timeo, struct sock *ssk);
 139 void netlink_detachskb(struct sock *sk, struct sk_buff *skb);
 140 int netlink_sendskb(struct sock *sk, struct sk_buff *skb);
 141
 142 static inline struct sk_buff *
 143 netlink_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
 173 struct 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
 189 struct netlink_notify {
 190         struct net *net;
 191         u32 portid;
 192         int protocol;
 193 };
 194
 195 struct nlmsghdr *
 196 __nlmsg_put(struct sk_buff *skb, u32 portid, u32 seq, int type, int len, int flags);
 197
 198 struct 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
 207 extern int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
 208                                 const struct nlmsghdr *nlh,
 209                                 struct netlink_dump_control *control);
 210 static 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
 220 struct netlink_tap {
 221         struct net_device *dev;
 222         struct module *module;
 223         struct list_head list;
 224 };
 225
 226 extern int netlink_add_tap(struct netlink_tap *nt);
 227 extern int netlink_remove_tap(struct netlink_tap *nt);
 228
 229 bool __netlink_ns_capable(const struct netlink_skb_parms *nsp,
 230                           struct user_namespace *ns, int cap);
 231 bool netlink_ns_capable(const struct sk_buff *skb,
 232                         struct user_namespace *ns, int cap);
 233 bool netlink_capable(const struct sk_buff *skb, int cap);
 234 bool netlink_net_capable(const struct sk_buff *skb, int cap);
 235
 236 #endif  /* __LINUX_NETLINK_H */