Generic Netlink Library (libnl-genl)

Modules
	Controller (Resolver)
	Resolves Generic Netlink family names to numeric identifiers.
	Family and Command Registration
	Registering Generic Netlink Families and Commands.

Generic Netlink Socket
int	genl_connect (struct nl_sock *sk)
	Connect a Generic Netlink socket. More...

Sending Data
int	genl_send_simple (struct nl_sock *sk, int family, int cmd, int version, int flags)
	Send a Generic Netlink message consisting only of a header. More...

Message Parsing
int	genlmsg_valid_hdr (struct nlmsghdr *nlh, int hdrlen)
	Validate Generic Netlink message headers. More...
int	genlmsg_validate (struct nlmsghdr *nlh, int hdrlen, int maxtype, const struct nla_policy *policy)
	Validate Generic Netlink message including attributes. More...
int	genlmsg_parse (struct nlmsghdr *nlh, int hdrlen, struct nlattr *tb[], int maxtype, const struct nla_policy *policy)
	Parse Generic Netlink message including attributes. More...
struct genlmsghdr *	genlmsg_hdr (struct nlmsghdr *nlh)
	Return pointer to Generic Netlink header. More...
int	genlmsg_len (const struct genlmsghdr *gnlh)
	Return length of message payload including user header. More...
void *	genlmsg_user_hdr (const struct genlmsghdr *gnlh)
	Return pointer to user header. More...
void *	genlmsg_user_data (const struct genlmsghdr *gnlh, const int hdrlen)
	Return pointer to user data. More...
int	genlmsg_user_datalen (const struct genlmsghdr *gnlh, const int hdrlen)
	Return length of user data. More...
struct nlattr *	genlmsg_attrdata (const struct genlmsghdr *gnlh, int hdrlen)
	Return pointer to message attributes. More...
int	genlmsg_attrlen (const struct genlmsghdr *gnlh, int hdrlen)
	Return length of message attributes. More...

Message Construction
void *	genlmsg_put (struct nl_msg *msg, uint32_t port, uint32_t seq, int family, int hdrlen, int flags, uint8_t cmd, uint8_t version)
	Add Generic Netlink headers to Netlink message. More...

Deprecated
void *	genlmsg_data (const struct genlmsghdr *gnlh)
	Return pointer to message payload. More...

Detailed Description

Function Documentation

genl_connect()

int genl_connect

(

struct nl_sock *

sk

)

Connect a Generic Netlink socket.

Parameters

sk	Unconnected Netlink socket

This function expects a struct nl_socket object previously allocated via nl_socket_alloc(). It calls nl_connect() to create the local socket file descriptor and binds the socket to the NETLINK_GENERIC Netlink protocol.

Using this function is equivalent to:

nl_connect(sk, NETLINK_GENERIC);

See also

nl_connect()

Returns

0 on success or a negative error code.

Definition at line 39 of file genl.c.

References nl_connect().

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genl_send_simple()

int genl_send_simple	(	struct nl_sock *	sk,
		int	family,
		int	cmd,
		int	version,
		int	flags
	)

Send a Generic Netlink message consisting only of a header.

Parameters

sk	Generic Netlink socket
family	Numeric family identifier
cmd	Numeric command identifier
version	Interface version
flags	Additional Netlink message flags (optional)

This function is a shortcut for sending a Generic Netlink message without any message payload. The message will only consist of the Netlink and Generic Netlink headers. The header is constructed based on the specified parameters and passed on to nl_send_simple() to send it on the specified socket.

Example:

#include <netlink/genl/genl.h>
#include <linux/genetlink.h>
 
err = genl_send_simple(sk, GENL_ID_CTRL, CTRL_CMD_GETFAMILY, CTRL_VERSION,
                       NLM_F_DUMP);

See also

nl_send_simple()

Returns

0 on success or a negative error code. Due to a bug, this function returns the number of bytes sent. Treat any non-negative number as success.

Definition at line 79 of file genl.c.

References nl_send_simple().

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genlmsg_valid_hdr()

int genlmsg_valid_hdr	(	struct nlmsghdr *	nlh,
		int	hdrlen
	)

Validate Generic Netlink message headers.

Parameters

nlh	Pointer to Netlink message header
hdrlen	Length of user header

Verifies the integrity of the Netlink and Generic Netlink headers by enforcing the following requirements:

• Valid Netlink message header (nlmsg_valid_hdr())
• Presence of a complete Generic Netlink header
• At least hdrlen bytes of payload included after the generic netlink header.

Returns

A positive integer (true) if the headers are valid or 0 (false) if not.

Definition at line 112 of file genl.c.

References genlmsg_len(), and nlmsg_data().

Referenced by genl_handle_msg(), genlmsg_parse(), and genlmsg_validate().

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genlmsg_validate()

int genlmsg_validate	(	struct nlmsghdr *	nlh,
		int	hdrlen,
		int	maxtype,
		const struct nla_policy *	policy
	)

Validate Generic Netlink message including attributes.

Parameters

nlh	Pointer to Netlink message header
hdrlen	Length of user header
maxtype	Maximum attribtue id expected
policy	Attribute validation policy

Verifies the validity of the Netlink and Generic Netlink headers using genlmsg_valid_hdr() and calls nla_validate() on the message payload to verify the integrity of eventual attributes.

Note

You may call genlmsg_parse() directly to perform validation and parsing in a single step.

See also

genlmsg_valid_hdr()

nla_validate()

genlmsg_parse()

Returns

0 on success or a negative error code.

Definition at line 146 of file genl.c.

References genlmsg_attrdata(), genlmsg_attrlen(), genlmsg_valid_hdr(), nla_validate(), and nlmsg_data().

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genlmsg_parse()

int genlmsg_parse	(	struct nlmsghdr *	nlh,
		int	hdrlen,
		struct nlattr *	tb[],
		int	maxtype,
		const struct nla_policy *	policy
	)

Parse Generic Netlink message including attributes.

Parameters

nlh	Pointer to Netlink message header
hdrlen	Length of user header
tb	Array to store parsed attributes
maxtype	Maximum attribute id expected
policy	Attribute validation policy

Verifies the validity of the Netlink and Generic Netlink headers using genlmsg_valid_hdr() and calls nla_parse() on the message payload to parse eventual attributes.

Example:

struct nlattr *attrs[MY_TYPE_MAX+1];
 
if ((err = genlmsg_parse(nlmsg_hdr(msg), sizeof(struct my_hdr), attrs,
                         MY_TYPE_MAX, attr_policy)) < 0)
        // ERROR

See also

genlmsg_valid_hdr()

genlmsg_validate()

nla_parse()

Returns

0 on success or a negative error code.

Definition at line 186 of file genl.c.

References genlmsg_attrdata(), genlmsg_attrlen(), genlmsg_valid_hdr(), nla_parse(), and nlmsg_data().

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genlmsg_hdr()

struct genlmsghdr * genlmsg_hdr

(

struct nlmsghdr *

nlh

)

Return pointer to Generic Netlink header.

Parameters

nlh	Netlink message header

Returns

Pointer to Generic Netlink message header

Definition at line 205 of file genl.c.

References nlmsg_data().

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genlmsg_len()

int genlmsg_len

(

const struct genlmsghdr *

gnlh

)

Return length of message payload including user header.

Parameters

gnlh	Generic Netlink message header

See also

genlmsg_data()

Returns

Length of user payload including an eventual user header in number of bytes.

Definition at line 219 of file genl.c.

Referenced by genlmsg_attrlen(), genlmsg_user_datalen(), and genlmsg_valid_hdr().

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genlmsg_user_hdr()

void * genlmsg_user_hdr

(

const struct genlmsghdr *

gnlh

)

Return pointer to user header.

Parameters

gnlh	Generic Netlink message header

Calculates the pointer to the user header based on the pointer to the Generic Netlink message header.

Returns

Pointer to the user header

Definition at line 237 of file genl.c.

References genlmsg_data().

Referenced by genlmsg_user_data().

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genlmsg_user_data()

void * genlmsg_user_data	(	const struct genlmsghdr *	gnlh,
		const int	hdrlen
	)

Return pointer to user data.

Parameters

gnlh	Generic netlink message header
hdrlen	Length of user header

Calculates the pointer to the user data based on the pointer to the Generic Netlink message header.

See also

genlmsg_user_datalen()

Returns

Pointer to the user data

Definition at line 254 of file genl.c.

References genlmsg_user_hdr().

Referenced by genlmsg_attrdata().

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genlmsg_user_datalen()

int genlmsg_user_datalen	(	const struct genlmsghdr *	gnlh,
		const int	hdrlen
	)

Return length of user data.

Parameters

gnlh	Generic Netlink message header
hdrlen	Length of user header

See also

genlmsg_user_data()

Returns

Length of user data in bytes

Definition at line 268 of file genl.c.

References genlmsg_len().

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genlmsg_attrdata()

struct nlattr * genlmsg_attrdata	(	const struct genlmsghdr *	gnlh,
		int	hdrlen
	)

Return pointer to message attributes.

Parameters

gnlh	Generic Netlink message header
hdrlen	Length of user header

See also

genlmsg_attrlen()

Returns

Pointer to the start of the message's attributes section.

Definition at line 282 of file genl.c.

References genlmsg_user_data().

Referenced by genlmsg_parse(), and genlmsg_validate().

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genlmsg_attrlen()

int genlmsg_attrlen	(	const struct genlmsghdr *	gnlh,
		int	hdrlen
	)

Return length of message attributes.

Parameters

gnlh	Generic Netlink message header
hdrlen	Length of user header

See also

genlmsg_attrdata()

Returns

Length of the message section containing attributes in number of bytes.

Definition at line 297 of file genl.c.

References genlmsg_len().

Referenced by genlmsg_parse(), and genlmsg_validate().

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genlmsg_put()

void * genlmsg_put	(	struct nl_msg *	msg,
		uint32_t	port,
		uint32_t	seq,
		int	family,
		int	hdrlen,
		int	flags,
		uint8_t	cmd,
		uint8_t	version
	)

Add Generic Netlink headers to Netlink message.

Parameters

msg	Netlink message object
port	Netlink port or NL_AUTO_PORT
seq	Sequence number of message or NL_AUTO_SEQ
family	Numeric family identifier
hdrlen	Length of user header
flags	Additional Netlink message flags (optional)
cmd	Numeric command identifier
version	Interface version

Calls nlmsg_put() on the specified message object to reserve space for the Netlink header, the Generic Netlink header, and a user header of specified length. Fills out the header fields with the specified parameters.

Example:

struct nl_msg *msg;
struct my_hdr *user_hdr;
 
if (!(msg = nlmsg_alloc()))
        // ERROR
 
user_hdr = genlmsg_put(msg, NL_AUTO_PORT, NL_AUTO_SEQ, family_id,
                       sizeof(struct my_hdr), 0, MY_CMD_FOO, 0);
if (!user_hdr)
        // ERROR

See also

nlmsg_put()

Returns Pointer to user header or NULL if an error occurred.

Definition at line 343 of file genl.c.

References nlmsg_data(), and nlmsg_put().

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genlmsg_data()

void * genlmsg_data

(

const struct genlmsghdr *

gnlh

)

Return pointer to message payload.

Parameters

gnlh	Generic Netlink message header

Deprecated:

This function has been deprecated due to inability to specify the length of the user header. Use genlmsg_user_hdr() respectively genlmsg_user_data().

Returns

Pointer to payload section

Definition at line 380 of file genl.c.

Referenced by genlmsg_user_hdr().

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