Collaboration diagram for Netlink socket helpers:

Functions
int	mnl_socket_get_fd (const struct mnl_socket *nl)
	mnl_socket_get_fd - obtain file descriptor from netlink socket More...

	EXPORT_SYMBOL (mnl_socket_get_fd)

unsigned int	mnl_socket_get_portid (const struct mnl_socket *nl)
	mnl_socket_get_portid - obtain Netlink PortID from netlink socket More...

	EXPORT_SYMBOL (mnl_socket_get_portid)

struct mnl_socket *	mnl_socket_open (int bus)
	mnl_socket_open - open a netlink socket More...

	EXPORT_SYMBOL (mnl_socket_open)

struct mnl_socket *	mnl_socket_fdopen (int fd)
	mnl_socket_fdopen - associates a mnl_socket object with pre-existing socket. More...

	EXPORT_SYMBOL (mnl_socket_fdopen)

int	mnl_socket_bind (struct mnl_socket *nl, unsigned int groups, pid_t pid)
	mnl_socket_bind - bind netlink socket More...

	EXPORT_SYMBOL (mnl_socket_bind)

ssize_t	mnl_socket_sendto (const struct mnl_socket nl, const void buf, size_t len)
	mnl_socket_sendto - send a netlink message of a certain size More...

	EXPORT_SYMBOL (mnl_socket_sendto)

ssize_t	mnl_socket_recvfrom (const struct mnl_socket nl, void buf, size_t bufsiz)
	mnl_socket_recvfrom - receive a netlink message More...

	EXPORT_SYMBOL (mnl_socket_recvfrom)

int	mnl_socket_close (struct mnl_socket *nl)
	mnl_socket_close - close a given netlink socket More...

	EXPORT_SYMBOL (mnl_socket_close)

int	mnl_socket_setsockopt (const struct mnl_socket nl, int type, void buf, socklen_t len)
	mnl_socket_setsockopt - set Netlink socket option More...

	EXPORT_SYMBOL (mnl_socket_setsockopt)

int	mnl_socket_getsockopt (const struct mnl_socket nl, int type, void buf, socklen_t *len)
	mnl_socket_getsockopt - get a Netlink socket option More...

	EXPORT_SYMBOL (mnl_socket_getsockopt)

Allocation
struct nl_sock *	nl_socket_alloc (void)
	Allocate new netlink socket. More...

struct nl_sock *	nl_socket_alloc_cb (struct nl_cb *cb)
	Allocate new socket with custom callbacks. More...

void	nl_socket_free (struct nl_sock *sk)
	Free a netlink socket. More...

Sequence Numbers
void	nl_socket_disable_seq_check (struct nl_sock *sk)
	Disable sequence number checking. More...

unsigned int	nl_socket_use_seq (struct nl_sock *sk)
	Use next sequence number. More...

void	nl_socket_disable_auto_ack (struct nl_sock *sk)
	Disable automatic request for ACK. More...

void	nl_socket_enable_auto_ack (struct nl_sock *sk)
	Enable automatic request for ACK (default) More...

Source Idenficiation
uint32_t	nl_socket_get_local_port (struct nl_sock *sk)

void	nl_socket_set_local_port (struct nl_sock *sk, uint32_t port)
	Set local port of socket. More...

Group Subscriptions
int	nl_socket_add_memberships (struct nl_sock *sk, int group,...)
	Join groups. More...

int	nl_socket_add_membership (struct nl_sock *sk, int group)

int	nl_socket_drop_memberships (struct nl_sock *sk, int group,...)
	Leave groups. More...

int	nl_socket_drop_membership (struct nl_sock *sk, int group)

void	nl_join_groups (struct nl_sock *sk, int groups)
	Join multicast groups (deprecated) More...

Peer Identfication
uint32_t	nl_socket_get_peer_port (struct nl_sock *sk)

void	nl_socket_set_peer_port (struct nl_sock *sk, uint32_t port)

File Descriptor
int	nl_socket_get_fd (struct nl_sock *sk)

int	nl_socket_set_nonblocking (struct nl_sock *sk)
	Set file descriptor of socket to non-blocking state. More...

void	nl_socket_enable_msg_peek (struct nl_sock *sk)
	Enable use of MSG_PEEK when reading from socket. More...

void	nl_socket_disable_msg_peek (struct nl_sock *sk)
	Disable use of MSG_PEEK when reading from socket. More...

Callback Handler
struct nl_cb *	nl_socket_get_cb (struct nl_sock *sk)

void	nl_socket_set_cb (struct nl_sock sk, struct nl_cb cb)

int	nl_socket_modify_cb (struct nl_sock sk, enum nl_cb_type type, enum nl_cb_kind kind, nl_recvmsg_msg_cb_t func, void arg)
	Modify the callback handler associated to the socket. More...

Utilities
int	nl_socket_set_buffer_size (struct nl_sock *sk, int rxbuf, int txbuf)
	Set socket buffer size of netlink socket. More...

int	nl_socket_set_passcred (struct nl_sock *sk, int state)
	Enable/disable credential passing on netlink socket. More...

int	nl_socket_recv_pktinfo (struct nl_sock *sk, int state)
	Enable/disable receival of additional packet information. More...

Detailed Description

Function Documentation

EXPORT_SYMBOL ( mnl_socket_get_fd )

EXPORT_SYMBOL ( mnl_socket_get_portid )

EXPORT_SYMBOL ( mnl_socket_open )

EXPORT_SYMBOL ( mnl_socket_fdopen )

EXPORT_SYMBOL ( mnl_socket_bind )

EXPORT_SYMBOL ( mnl_socket_sendto )

EXPORT_SYMBOL ( mnl_socket_recvfrom )

EXPORT_SYMBOL ( mnl_socket_close )

EXPORT_SYMBOL ( mnl_socket_setsockopt )

EXPORT_SYMBOL ( mnl_socket_getsockopt )

int mnl_socket_bind	(	struct mnl_socket *	nl,
		unsigned int	groups,
		pid_t	pid
	)

mnl_socket_bind - bind netlink socket

Parameters

nl	netlink socket obtained via mnl_socket_open()
groups	the group of message you're interested in
pid	the port ID you want to use (use zero for automatic selection)

On error, this function returns -1 and errno is appropriately set. On success, 0 is returned. You can use MNL_SOCKET_AUTOPID which is 0 for automatic port ID selection.

References mnl_socket::addr, mnl_socket::fd, sockaddr_nl::nl_family, sockaddr_nl::nl_groups, and sockaddr_nl::nl_pid.

Referenced by cthelper_init(), mnl_event_nssocket(), netlink_monitor(), nfct_mnl_open(), nft_batch_is_supported(), nft_compatible_revision(), nft_init(), and xtables_events_main().

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int mnl_socket_close ( struct mnl_socket * nl )

mnl_socket_close - close a given netlink socket

Parameters

nl	netlink socket obtained via mnl_socket_open()

On error, this function returns -1 and errno is appropriately set. On success, it returns 0.

References mnl_socket::fd.

Referenced by cthelper_kill(), main(), mnl_event_nssocket(), nft_batch_is_supported(), nft_compatible_revision(), nft_fini(), nfts_socket_close(), and xtables_events_main().

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struct mnl_socket* mnl_socket_fdopen ( int fd )

mnl_socket_fdopen - associates a mnl_socket object with pre-existing socket.

Parameters

fd	pre-existing socket descriptor.

On error, it returns NULL and errno is appropriately set. Otherwise, it returns a valid pointer to the mnl_socket structure. It also sets the portID if the socket fd is already bound and it is AF_NETLINK.

Note that mnl_socket_get_portid() returns 0 if this function is used with non-netlink socket.

References mnl_socket::addr, mnl_socket::fd, sockaddr_nl::nl_family, and NULL.

Referenced by mnl_nssocket_open().

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int mnl_socket_get_fd ( const struct mnl_socket * nl )

mnl_socket_get_fd - obtain file descriptor from netlink socket

Parameters

nl	netlink socket obtained via mnl_socket_open()

This function returns the file descriptor of a given netlink socket.

References mnl_socket::fd.

Referenced by cthelper_init(), handle_qacb(), and mnl_batch_talk().

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unsigned int mnl_socket_get_portid ( const struct mnl_socket * nl )

mnl_socket_get_portid - obtain Netlink PortID from netlink socket

Parameters

nl	netlink socket obtained via mnl_socket_open()

This function returns the Netlink PortID of a given netlink socket. It's a common mistake to assume that this PortID equals the process ID which is not always true. This is the case if you open more than one socket that is binded to the same Netlink subsystem from the same process.

References mnl_socket::addr, and sockaddr_nl::nl_pid.

Referenced by cthelper_init(), mnl_batch_supported(), mnl_batch_talk(), nft_batch_is_supported(), nft_compatible_revision(), and nft_init().

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int mnl_socket_getsockopt	(	const struct mnl_socket *	nl,
		int	type,
		void *	buf,
		socklen_t *	len
	)

mnl_socket_getsockopt - get a Netlink socket option

Parameters

nl	netlink socket obtained via mnl_socket_open()
type	type of Netlink socket options
buf	pointer to the buffer to store the value of this option
len	size of the information written in the buffer

On error, this function returns -1 and errno is appropriately set.

References mnl_socket::fd, and SOL_NETLINK.

struct mnl_socket* mnl_socket_open ( int bus )

mnl_socket_open - open a netlink socket

Parameters

bus	the netlink socket bus ID (see NETLINK_* constants)

On error, it returns NULL and errno is appropriately set. Otherwise, it returns a valid pointer to the mnl_socket structure.

References mnl_socket::fd, and NULL.

Referenced by cthelper_init(), nfct_mnl_open(), nft_batch_is_supported(), nft_compatible_revision(), nft_init(), and xtables_events_main().

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ssize_t mnl_socket_recvfrom	(	const struct mnl_socket *	nl,
		void *	buf,
		size_t	bufsiz
	)

mnl_socket_recvfrom - receive a netlink message

Parameters

nl	netlink socket obtained via mnl_socket_open()
buf	buffer that you want to use to store the netlink message
bufsiz	size of the buffer passed to store the netlink message

On error, it returns -1 and errno is appropriately set. If errno is set to ENOSPC, it means that the buffer that you have passed to store the netlink message is too small, so you have received a truncated message. To avoid this, you have to allocate a buffer of MNL_SOCKET_BUFFER_SIZE (which is 8KB, see linux/netlink.h for more information). Using this buffer size ensures that your buffer is big enough to store the netlink message without truncating it.

References buf, mnl_socket::fd, MSG_TRUNC, and NULL.

Referenced by handle_qacb(), mnl_batch_supported(), mnl_batch_talk(), mnl_talk(), nfct_mnl_talk(), nft_batch_is_supported(), nft_compatible_revision(), and xtables_events_main().

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ssize_t mnl_socket_sendto	(	const struct mnl_socket *	nl,
		const void *	buf,
		size_t	len
	)

mnl_socket_sendto - send a netlink message of a certain size

Parameters

nl	netlink socket obtained via mnl_socket_open()
buf	buffer containing the netlink message to be sent
len	number of bytes in the buffer that you want to send

On error, it returns -1 and errno is appropriately set. Otherwise, it returns the number of bytes sent.

References mnl_socket::fd, and sockaddr_nl::nl_family.

Referenced by mnl_batch_supported(), mnl_talk(), nfct_mnl_talk(), nft_batch_is_supported(), and nft_compatible_revision().

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int mnl_socket_setsockopt	(	const struct mnl_socket *	nl,
		int	type,
		void *	buf,
		socklen_t	len
	)

mnl_socket_setsockopt - set Netlink socket option

Parameters

nl	netlink socket obtained via mnl_socket_open()
type	type of Netlink socket options
buf	the buffer that contains the data about this option
len	the size of the buffer passed

This function allows you to set some Netlink socket option. As of writing this (see linux/netlink.h), the existing options are:

#define NETLINK_ADD_MEMBERSHIP 1
#define NETLINK_DROP_MEMBERSHIP 2
#define NETLINK_PKTINFO 3
#define NETLINK_BROADCAST_ERROR 4
#define NETLINK_NO_ENOBUFS 5

In the early days, Netlink only supported 32 groups expressed in a 32-bits mask. However, since 2.6.14, Netlink may have up to 2^32 multicast groups but you have to use setsockopt() with NETLINK_ADD_MEMBERSHIP to join a given multicast group. This function internally calls setsockopt() to join a given netlink multicast group. You can still use mnl_bind() and the 32-bit mask to join a set of Netlink multicast groups.

On error, this function returns -1 and errno is appropriately set.

References mnl_socket::fd, and SOL_NETLINK.

void nl_join_groups	(	struct nl_sock *	sk,
		int	groups
	)

Join multicast groups (deprecated)

sk Netlink socket.
groups Bitmask of groups to join.

This function defines the old way of joining multicast group which has to be done prior to calling nl_connect(). It works on any kernel version but is very limited as only 32 groups can be joined.

References sockaddr_nl::nl_groups, and nl_sock::s_local.

int nl_socket_add_membership	(	struct nl_sock *	sk,
		int	group
	)

References nl_socket_add_memberships().

Referenced by main(), and nl_cache_mngr_add().

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int nl_socket_add_memberships	(	struct nl_sock *	sk,
		int	group,
			...
	)

Join groups.

sk Netlink socket
group Group identifier

Joins the specified groups using the modern socket option which is available since kernel version 2.6.14. It allows joining an almost arbitary number of groups without limitation. The list of groups has to be terminated by 0 (NFNLGRP_NONE).

Make sure to use the correct group definitions as the older bitmask definitions for nl_join_groups() are likely to still be present for backward compatibility reasons.

Returns: 0 on sucess or a negative error code.

References NETLINK_ADD_MEMBERSHIP, nl_syserr2nlerr(), NLE_BAD_SOCK, NLE_INVAL, nl_sock::s_fd, and SOL_NETLINK.

Referenced by nl_socket_add_membership().

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struct nl_sock* nl_socket_alloc ( void )

Allocate new netlink socket.

Returns: Newly allocated netlink socket or NULL.

References nl_cb_alloc(), and NULL.

Referenced by nfnl_queue_socket_alloc(), and nl_cli_alloc_socket().

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struct nl_sock* nl_socket_alloc_cb ( struct nl_cb * cb )

Allocate new socket with custom callbacks.

cb Callback handler

The reference to the callback handler is taken into account automatically, it is released again upon calling nl_socket_free().

Returns: Newly allocted socket handle or NULL.

References BUG, nl_cb_get(), and NULL.

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void nl_socket_disable_auto_ack ( struct nl_sock * sk )

Disable automatic request for ACK.

sk Netlink socket.

The default behaviour of a socket is to request an ACK for each message sent to allow for the caller to synchronize to the completion of the netlink operation. This function disables this behaviour and will result in requests being sent which will not have the NLM_F_ACK flag set automatically. However, it is still possible for the caller to set the NLM_F_ACK flag explicitely.

References NL_NO_AUTO_ACK, and nl_sock::s_flags.

Referenced by nfnl_queue_socket_alloc().

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void nl_socket_disable_msg_peek ( struct nl_sock * sk )

Disable use of MSG_PEEK when reading from socket.

sk Netlink socket.

References NL_MSG_PEEK, and nl_sock::s_flags.

void nl_socket_disable_seq_check ( struct nl_sock * sk )

Disable sequence number checking.

sk Netlink socket.

Disables checking of sequence numbers on the netlink socket This is required to allow messages to be processed which were not requested by a preceding request message, e.g. netlink events.

Note: This function modifies the NL_CB_SEQ_CHECK configuration in the callback handle associated with the socket.

References NL_CB_CUSTOM, NL_CB_SEQ_CHECK, nl_cb_set(), NULL, and nl_sock::s_cb.

Referenced by main(), and nl_cache_mngr_alloc().

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int nl_socket_drop_membership	(	struct nl_sock *	sk,
		int	group
	)

References nl_socket_drop_memberships().

Referenced by nl_cache_mngr_add().

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int nl_socket_drop_memberships	(	struct nl_sock *	sk,
		int	group,
			...
	)

Leave groups.

sk Netlink socket
group Group identifier

Leaves the specified groups using the modern socket option which is available since kernel version 2.6.14. The list of groups has to terminated by 0 (NFNLGRP_NONE).