Core

Collaboration diagram for Core:

Modules
	Abstract Address
	Caching
	Abstract Data
	Callbacks/Customization
	Messages
	Netlink Message Construction/Parsing Interface.
	Netlink socket helpers
	Utilities

Connection Management
int	nl_connect (struct nl_sock *sk, int protocol)
	Create and connect netlink socket. More...
void	nl_close (struct nl_sock *sk)
	Close/Disconnect netlink socket. More...

Send
int	nl_sendto (struct nl_sock *sk, void *buf, size_t size)
	Send raw data over netlink socket. More...
int	nl_sendmsg (struct nl_sock *sk, struct nl_msg *msg, struct msghdr *hdr)
	Send netlink message with control over sendmsg() message header. More...
int	nl_send_iovec (struct nl_sock *sk, struct nl_msg *msg, const struct iovec *iov, unsigned iovlen)
	Send netlink message. More...
int	nl_send (struct nl_sock *sk, struct nl_msg *msg)
	Send netlink message. More...
void	nl_auto_complete (struct nl_sock *sk, struct nl_msg *msg)
int	nl_send_auto_complete (struct nl_sock *sk, struct nl_msg *msg)
	Send netlink message and check & extend header values as needed. More...
int	nl_send_simple (struct nl_sock *sk, int type, int flags, void *buf, size_t size)
	Send simple netlink message using nl_send_auto_complete() More...

Receive
int	nl_recv (struct nl_sock *sk, struct sockaddr_nl *nla, unsigned char **buf, struct ucred **creds)
	Receive data from netlink socket. More...
int	nl_recvmsgs (struct nl_sock *sk, struct nl_cb *cb)
	Receive a set of messages from a netlink socket. More...
int	nl_recvmsgs_default (struct nl_sock *sk)
	Receive a set of message from a netlink socket using handlers in nl_sock. More...
int	nl_wait_for_ack (struct nl_sock *sk)
	Wait for ACK. More...
#define	NL_CB_CALL(cb, type, msg)

Detailed Description

1) Connecting the socket

// Bind and connect the socket to a protocol, NETLINK_ROUTE in this example.
nl_connect(sk, NETLINK_ROUTE);

2) Sending data

// The most rudimentary method is to use nl_sendto() simply pushing
// a piece of data to the other netlink peer. This method is not
// recommended.
const char buf[] = { 0x01, 0x02, 0x03, 0x04 };
nl_sendto(sk, buf, sizeof(buf));

// A more comfortable interface is nl_send() taking a pointer to
// a netlink message.
struct nl_msg *msg = my_msg_builder();
nl_send(sk, nlmsg_hdr(msg));

// nl_sendmsg() provides additional control over the sendmsg() message
// header in order to allow more specific addressing of multiple peers etc.
struct msghdr hdr = { ... };
nl_sendmsg(sk, nlmsg_hdr(msg), &hdr);

// You're probably too lazy to fill out the netlink pid, sequence number
// and message flags all the time. nl_send_auto_complete() automatically
// extends your message header as needed with an appropriate sequence
// number, the netlink pid stored in the netlink socket and the message
// flags NLM_F_REQUEST and NLM_F_ACK (if not disabled in the socket)
nl_send_auto_complete(sk, nlmsg_hdr(msg));

// Simple protocols don't require the complex message construction interface
// and may favour nl_send_simple() to easly send a bunch of payload
// encapsulated in a netlink message header.
nl_send_simple(sk, MY_MSG_TYPE, 0, buf, sizeof(buf));

3) Receiving data

// nl_recv() receives a single message allocating a buffer for the message
// content and gives back the pointer to you.
struct sockaddr_nl peer;
unsigned char *msg;
nl_recv(sk, &peer, &msg);

// nl_recvmsgs() receives a bunch of messages until the callback system
// orders it to state, usually after receving a compolete multi part
// message series.
nl_recvmsgs(sk, my_callback_configuration);

// nl_recvmsgs_default() acts just like nl_recvmsg() but uses the callback
// configuration stored in the socket.
nl_recvmsgs_default(sk);

// In case you want to wait for the ACK to be recieved that you requested
// with your latest message, you can call nl_wait_for_ack()
nl_wait_for_ack(sk);

4) Closing

// Close the socket first to release kernel memory
nl_close(sk);

Macro Definition Documentation

#define NL_CB_CALL	(		cb,
			type,
			msg
	)

Value:

do { \
    err = nl_cb_call(cb, type, msg); \
    switch (err) { \
    case NL_OK: \
        err = 0; \
        break; \
    case NL_SKIP: \
        goto skip; \
    case NL_STOP: \
        goto stop; \
    default: \
        goto out; \
    } \
} while (0)

Function Documentation

void nl_auto_complete	(	struct nl_sock *	sk,
		struct nl_msg *	msg
	)

References NL_NO_AUTO_ACK, sockaddr_nl::nl_pid, nlh, NLM_F_ACK, NLM_F_REQUEST, nlmsghdr::nlmsg_flags, nlmsg_hdr(), nlmsghdr::nlmsg_pid, nlmsghdr::nlmsg_seq, nl_msg::nm_protocol, nl_sock::s_flags, nl_sock::s_local, nl_sock::s_proto, and nl_sock::s_seq_next.

Referenced by nfnl_queue_msg_send_verdict_payload(), and nl_send_auto_complete().

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void nl_close

(

struct nl_sock *

sk

)

Close/Disconnect netlink socket.

• sk Netlink socket.

References nl_sock::s_fd, and nl_sock::s_proto.

Referenced by main(), and nl_cache_mngr_free().

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int nl_connect	(	struct nl_sock *	sk,
		int	protocol
	)

Create and connect netlink socket.

• sk Netlink socket.
• protocol Netlink protocol to use.

Creates a netlink socket using the specified protocol, binds the socket and issues a connection attempt.

Returns

0 on success or a negative error code.

References sockaddr_nl::nl_family, NL_SOCK_BUFSIZE_SET, nl_socket_set_buffer_size(), nl_syserr2nlerr(), NLE_AF_NOSUPPORT, NLE_NOADDR, nl_sock::s_fd, nl_sock::s_flags, nl_sock::s_local, and nl_sock::s_proto.

Referenced by genl_connect(), nfnl_connect(), nl_cache_mngr_alloc(), and nl_cli_connect().

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int nl_recv	(	struct nl_sock *	sk,
		struct sockaddr_nl *	nla,
		unsigned char **	buf,
		struct ucred **	creds
	)

Receive data from netlink socket.

• sk Netlink socket.
• nla Destination pointer for peer's netlink address.
• buf Destination pointer for message content.
• creds Destination pointer for credentials.

Receives a netlink message, allocates a buffer in *buf and stores the message content. The peer's netlink address is stored in *nla. The caller is responsible for freeing the buffer allocated in *buf if a positive value is returned. Interruped system calls are handled by repeating the read. The input buffer size is determined by peeking before the actual read is done.

A non-blocking sockets causes the function to return immediately with a return value of 0 if no data is available.

Returns

Number of octets read, 0 on EOF or a negative error code.

References flags, MSG_TRUNC, NL_DBG, NL_MSG_PEEK, NL_SOCK_PASSCRED, nl_syserr2nlerr(), NLE_NOADDR, NULL, nl_sock::s_fd, and nl_sock::s_flags.

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int nl_recvmsgs	(	struct nl_sock *	sk,
		struct nl_cb *	cb
	)

Receive a set of messages from a netlink socket.

• sk Netlink socket.
• cb set of callbacks to control behaviour.

Repeatedly calls nl_recv() or the respective replacement if provided by the application (see nl_cb_overwrite_recv()) and parses the received data as netlink messages. Stops reading if one of the callbacks returns NL_STOP or nl_recv returns either 0 or a negative error code.

A non-blocking sockets causes the function to return immediately if no data is available.

Returns

0 on success or a negative error code from nl_recv().

References nl_cb::cb_recvmsgs_ow.

Referenced by __cache_pickup(), nl_recvmsgs_default(), and nl_wait_for_ack().

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int nl_recvmsgs_default

(

struct nl_sock *

sk

)

Receive a set of message from a netlink socket using handlers in nl_sock.

• sk Netlink socket.

Calls nl_recvmsgs() with the handlers configured in the netlink socket.

References nl_recvmsgs(), and nl_sock::s_cb.

Referenced by main(), and nl_cache_mngr_data_ready().

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int nl_send	(	struct nl_sock *	sk,
		struct nl_msg *	msg
	)

Send netlink message.

• sk Netlink socket.
• msg Netlink message to be sent.

  See also

  nl_sendmsg()

  Returns

  Number of characters sent on success or a negative error code.

References nl_send_iovec(), nlmsg_hdr(), and nlmsghdr::nlmsg_len.

Referenced by nl_send_auto_complete().

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int nl_send_auto_complete	(	struct nl_sock *	sk,
		struct nl_msg *	msg
	)

Send netlink message and check & extend header values as needed.

• sk Netlink socket.
• msg Netlink message to be sent.

Checks the netlink message nlh for completness and extends it as required before sending it out. Checked fields include pid, sequence nr, and flags.

See also

nl_send()

Returns

Number of characters sent or a negative error code.

References nl_cb::cb_send_ow, nl_auto_complete(), nl_send(), and nl_sock::s_cb.

Referenced by flnl_lookup(), main(), nfnl_ct_add(), nfnl_ct_del(), nfnl_ct_query(), nfnl_nft_chain_add(), nfnl_nft_chain_delete(), nfnl_nft_chain_query(), nfnl_nft_rule_add(), nfnl_nft_rule_delete(), nfnl_nft_rule_query(), nfnl_nft_set_add(), nfnl_nft_set_delete(), nfnl_nft_set_dump_request(), nfnl_nft_set_query(), nfnl_nft_setelem_dump_request(), nfnl_nft_setelem_query(), nfnl_nft_table_add(), nfnl_nft_table_delete(), nfnl_nft_table_query(), nfnl_queue_msg_send_verdict(), nl_send_simple(), rtnl_addr_add(), rtnl_addr_delete(), rtnl_class_add(), rtnl_class_delete(), rtnl_cls_add(), rtnl_cls_change(), rtnl_cls_delete(), rtnl_link_change(), rtnl_neigh_add(), rtnl_neigh_delete(), rtnl_neightbl_change(), rtnl_qdisc_add(), rtnl_qdisc_change(), rtnl_qdisc_delete(), rtnl_route_add(), rtnl_route_delete(), rtnl_rule_add(), and rtnl_rule_delete().

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int nl_send_iovec	(	struct nl_sock *	sk,
		struct nl_msg *	msg,
		const struct iovec *	iov,
		unsigned	iovlen
	)

Send netlink message.

• sk Netlink socket.
• msg Netlink message to be sent.
• iov iovec to be sent.
• iovlen number of struct iovec to be sent.

  See also

  nl_sendmsg()

  Returns

  Number of characters sent on success or a negative error code.

References buf, sockaddr_nl::nl_family, nl_sendmsg(), nlmsg_get_creds(), nlmsg_get_dst(), NULL, and nl_sock::s_peer.

Referenced by nfnl_queue_msg_send_verdict_payload(), and nl_send().

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int nl_send_simple	(	struct nl_sock *	sk,
		int	type,
		int	flags,
		void *	buf,
		size_t	size
	)

Send simple netlink message using nl_send_auto_complete()

• sk Netlink socket.
• type Netlink message type.
• flags Netlink message flags.
• buf Data buffer.
• size Size of data buffer.

Builds a netlink message with the specified type and flags and appends the specified data as payload to the message.

See also

nl_send_auto_complete()

Returns

Number of characters sent on success or a negative error code.

References nl_send_auto_complete(), NLE_NOMEM, NLMSG_ALIGNTO, nlmsg_alloc_simple(), nlmsg_append(), and nlmsg_free().

Referenced by genl_send_simple(), nfnl_send_simple(), and nl_rtgen_request().

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int nl_sendmsg	(	struct nl_sock *	sk,
		struct nl_msg *	msg,
		struct msghdr *	hdr
	)

Send netlink message with control over sendmsg() message header.

• sk Netlink socket.
• msg Netlink message to be sent.
• hdr Sendmsg() message header.

  Returns

  Number of characters sent on sucess or a negative error code.

References nl_cb::cb_set, NL_CB_MSG_OUT, NL_DBG, NL_OK, nl_syserr2nlerr(), nlmsg_set_src(), nl_sock::s_cb, nl_sock::s_fd, and nl_sock::s_local.

Referenced by nl_send_iovec().

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int nl_sendto	(	struct nl_sock *	sk,
		void *	buf,
		size_t	size
	)

Send raw data over netlink socket.

• sk Netlink socket.
• buf Data buffer.
• size Size of data buffer.

  Returns

  Number of characters written on success or a negative error code.

References nl_syserr2nlerr(), nl_sock::s_fd, and nl_sock::s_peer.

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int nl_wait_for_ack

(

struct nl_sock *

sk

)

Wait for ACK.

• sk Netlink socket.

  Precondition

  The netlink socket must be in blocking state.

  Waits until an ACK is received for the latest not yet acknowledged netlink message.

References NL_CB_ACK, nl_cb_clone(), NL_CB_CUSTOM, nl_cb_put(), nl_cb_set(), nl_recvmsgs(), NLE_NOMEM, NULL, and nl_sock::s_cb.

Referenced by rtnl_cls_add(), rtnl_cls_change(), and rtnl_cls_delete().

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