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linux/include/linux/netlink.h
David Ahern 22e6c58b8c netlink: Add answer_flags to netlink_callback 
With dump filtering we need a way to ensure the NLM_F_DUMP_FILTERED
flag is set on a message back to the user if the data returned is
influenced by some input attributes. Normally this can be done as
messages are added to the skb, but if the filter results in no data
being returned, the user could be confused as to why.

This patch adds answer_flags to the netlink_callback allowing dump
handlers to set the NLM_F_DUMP_FILTERED at a minimum in the
NLMSG_DONE message ensuring the flag gets back to the user.

The netlink_callback space is initialized to 0 via a memset in
__netlink_dump_start, so init of the new answer_flags is covered.

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-10-16 00:13:12 -07:00

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6.9 KiB
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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_NETLINK_H
#define __LINUX_NETLINK_H
#include <linux/capability.h>
#include <linux/skbuff.h>
#include <linux/export.h>
#include <net/scm.h>
#include <uapi/linux/netlink.h>
struct net;
static inline struct nlmsghdr *nlmsg_hdr(const struct sk_buff *skb)
{
return (struct nlmsghdr *)skb->data;
}
enum netlink_skb_flags {
NETLINK_SKB_DST = 0x8, /* Dst set in sendto or sendmsg */
};
struct netlink_skb_parms {
struct scm_creds creds; /* Skb credentials */
__u32 portid;
__u32 dst_group;
__u32 flags;
struct sock *sk;
bool nsid_is_set;
int nsid;
};
#define NETLINK_CB(skb) (*(struct netlink_skb_parms*)&((skb)->cb))
#define NETLINK_CREDS(skb) (&NETLINK_CB((skb)).creds)
extern void netlink_table_grab(void);
extern void netlink_table_ungrab(void);
#define NL_CFG_F_NONROOT_RECV (1 << 0)
#define NL_CFG_F_NONROOT_SEND (1 << 1)
/* optional Netlink kernel configuration parameters */
struct netlink_kernel_cfg {
unsigned int groups;
unsigned int flags;
void (*input)(struct sk_buff *skb);
struct mutex *cb_mutex;
int (*bind)(struct net *net, int group);
void (*unbind)(struct net *net, int group);
bool (*compare)(struct net *net, struct sock *sk);
};
extern struct sock *__netlink_kernel_create(struct net *net, int unit,
struct module *module,
struct netlink_kernel_cfg *cfg);
static inline struct sock *
netlink_kernel_create(struct net *net, int unit, struct netlink_kernel_cfg *cfg)
{
return __netlink_kernel_create(net, unit, THIS_MODULE, cfg);
}
/* this can be increased when necessary - don't expose to userland */
#define NETLINK_MAX_COOKIE_LEN 20
/**
* struct netlink_ext_ack - netlink extended ACK report struct
* @_msg: message string to report - don't access directly, use
* %NL_SET_ERR_MSG
* @bad_attr: attribute with error
* @cookie: cookie data to return to userspace (for success)
* @cookie_len: actual cookie data length
*/
struct netlink_ext_ack {
const char *_msg;
const struct nlattr *bad_attr;
u8 cookie[NETLINK_MAX_COOKIE_LEN];
u8 cookie_len;
};
/* Always use this macro, this allows later putting the
* message into a separate section or such for things
* like translation or listing all possible messages.
* Currently string formatting is not supported (due
* to the lack of an output buffer.)
*/
#define NL_SET_ERR_MSG(extack, msg) do { \
static const char __msg[] = msg; \
struct netlink_ext_ack *__extack = (extack); \
\
if (__extack) \
__extack->_msg = __msg; \
} while (0)
#define NL_SET_ERR_MSG_MOD(extack, msg) \
NL_SET_ERR_MSG((extack), KBUILD_MODNAME ": " msg)
#define NL_SET_BAD_ATTR(extack, attr) do { \
if ((extack)) \
(extack)->bad_attr = (attr); \
} while (0)
#define NL_SET_ERR_MSG_ATTR(extack, attr, msg) do { \
static const char __msg[] = msg; \
struct netlink_ext_ack *__extack = (extack); \
\
if (__extack) { \
__extack->_msg = __msg; \
__extack->bad_attr = (attr); \
} \
} while (0)
extern void netlink_kernel_release(struct sock *sk);
extern int __netlink_change_ngroups(struct sock *sk, unsigned int groups);
extern int netlink_change_ngroups(struct sock *sk, unsigned int groups);
extern void __netlink_clear_multicast_users(struct sock *sk, unsigned int group);
extern void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
const struct netlink_ext_ack *extack);
extern int netlink_has_listeners(struct sock *sk, unsigned int group);
extern int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 portid, int nonblock);
extern int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, __u32 portid,
__u32 group, gfp_t allocation);
extern int netlink_broadcast_filtered(struct sock *ssk, struct sk_buff *skb,
__u32 portid, __u32 group, gfp_t allocation,
int (*filter)(struct sock *dsk, struct sk_buff *skb, void *data),
void *filter_data);
extern int netlink_set_err(struct sock *ssk, __u32 portid, __u32 group, int code);
extern int netlink_register_notifier(struct notifier_block *nb);
extern int netlink_unregister_notifier(struct notifier_block *nb);
/* finegrained unicast helpers: */
struct sock *netlink_getsockbyfilp(struct file *filp);
int netlink_attachskb(struct sock *sk, struct sk_buff *skb,
long *timeo, struct sock *ssk);
void netlink_detachskb(struct sock *sk, struct sk_buff *skb);
int netlink_sendskb(struct sock *sk, struct sk_buff *skb);
static inline struct sk_buff *
netlink_skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
{
struct sk_buff *nskb;
nskb = skb_clone(skb, gfp_mask);
if (!nskb)
return NULL;
/* This is a large skb, set destructor callback to release head */
if (is_vmalloc_addr(skb->head))
nskb->destructor = skb->destructor;
return nskb;
}
/*
* skb should fit one page. This choice is good for headerless malloc.
* But we should limit to 8K so that userspace does not have to
* use enormous buffer sizes on recvmsg() calls just to avoid
* MSG_TRUNC when PAGE_SIZE is very large.
*/
#if PAGE_SIZE < 8192UL
#define NLMSG_GOODSIZE SKB_WITH_OVERHEAD(PAGE_SIZE)
#else
#define NLMSG_GOODSIZE SKB_WITH_OVERHEAD(8192UL)
#endif
#define NLMSG_DEFAULT_SIZE (NLMSG_GOODSIZE - NLMSG_HDRLEN)
struct netlink_callback {
struct sk_buff *skb;
const struct nlmsghdr *nlh;
int (*dump)(struct sk_buff * skb,
struct netlink_callback *cb);
int (*done)(struct netlink_callback *cb);
void *data;
/* the module that dump function belong to */
struct module *module;
struct netlink_ext_ack *extack;
u16 family;
u16 min_dump_alloc;
bool strict_check;
u16 answer_flags;
unsigned int prev_seq, seq;
long args[6];
};
struct netlink_notify {
struct net *net;
u32 portid;
int protocol;
};
struct nlmsghdr *
__nlmsg_put(struct sk_buff *skb, u32 portid, u32 seq, int type, int len, int flags);
struct netlink_dump_control {
int (*start)(struct netlink_callback *);
int (*dump)(struct sk_buff *skb, struct netlink_callback *);
int (*done)(struct netlink_callback *);
void *data;
struct module *module;
u16 min_dump_alloc;
};
extern int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
const struct nlmsghdr *nlh,
struct netlink_dump_control *control);
static inline int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
const struct nlmsghdr *nlh,
struct netlink_dump_control *control)
{
if (!control->module)
control->module = THIS_MODULE;
return __netlink_dump_start(ssk, skb, nlh, control);
}
struct netlink_tap {
struct net_device *dev;
struct module *module;
struct list_head list;
};
extern int netlink_add_tap(struct netlink_tap *nt);
extern int netlink_remove_tap(struct netlink_tap *nt);
bool __netlink_ns_capable(const struct netlink_skb_parms *nsp,
struct user_namespace *ns, int cap);
bool netlink_ns_capable(const struct sk_buff *skb,
struct user_namespace *ns, int cap);
bool netlink_capable(const struct sk_buff *skb, int cap);
bool netlink_net_capable(const struct sk_buff *skb, int cap);
#endif /* __LINUX_NETLINK_H */
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