Netlink Message Construction/Parsing Interface. More...

Collaboration diagram for Messages:

Modules
	Netlink attribute helpers
	Netlink Type-Length-Value (TLV) attribute:

Data Structures
struct	nlmsghdr
	Netlink message header. More...

struct	nlmsgerr
	Netlink error message. More...

Macros
#define	NL_AUTO_PID 0
	Will cause the netlink pid to be set to the pid assigned to the netlink handle (socket) just before sending the message off. More...

#define	NL_AUTO_SEQ 0
	May be used to refer to a sequence number which should be automatically set just before sending the message off. More...

Iterators
#define	nlmsg_for_each_attr(pos, nlh, hdrlen, rem)
	Iterate over a stream of attributes in a message. More...

#define	nlmsg_for_each_msg(pos, head, len, rem)
	Iterate over a stream of messages. More...

Standard message flags
#define	NLM_F_REQUEST 1
	Must be set on all request messages (typically from user space to kernel space). More...

#define	NLM_F_MULTI 2
	Indicates the message is part of a multipart message terminated by NLMSG_DONE. More...

#define	NLM_F_ACK 4
	Request for an acknowledgment on success. More...

#define	NLM_F_ECHO 8
	Echo this request. More...

Additional message flags for GET requests
#define	NLM_F_ROOT 0x100
	Return the complete table instead of a single entry. More...

#define	NLM_F_MATCH 0x200
	Return all entries matching criteria passed in message content. More...

#define	NLM_F_ATOMIC 0x400
	Return an atomic snapshot of the table being referenced. More...

#define	NLM_F_DUMP (NLM_F_ROOT\|NLM_F_MATCH)
	Dump all entries. More...

Additional messsage flags for NEW requests
#define	NLM_F_REPLACE 0x100
	Replace existing matching config object with this request. More...

#define	NLM_F_EXCL 0x200
	Don't replace the config object if it already exists. More...

#define	NLM_F_CREATE 0x400
	Create config object if it doesn't already exist. More...

#define	NLM_F_APPEND 0x800
	Add to the end of the object list. More...

Standard Message types
#define	NLMSG_NOOP 0x1
	No operation, message must be ignored. More...

#define	NLMSG_ERROR 0x2
	The message signals an error and the payload contains a nlmsgerr structure. More...

#define	NLMSG_DONE 0x3
	Message terminates a multipart message. More...

#define	NLMSG_OVERRUN 0x4
	The message signals that data got lost. More...

#define	NLMSG_MIN_TYPE 0x10
	Lower limit of reserved message types. More...

Size Calculations
int	nlmsg_msg_size (int payload)
	length of netlink message not including padding More...

int	nlmsg_total_size (int payload)
	length of netlink message including padding More...

int	nlmsg_padlen (int payload)
	length of padding at the message's tail More...

Payload Access
void *	nlmsg_data (const struct nlmsghdr *nlh)
	head of message payload More...

void *	nlmsg_tail (const struct nlmsghdr *nlh)

int	nlmsg_len (const struct nlmsghdr *nlh)
	length of message payload More...

Attribute Access
struct nlattr *	nlmsg_attrdata (const struct nlmsghdr *nlh, int hdrlen)
	head of attributes data More...

int	nlmsg_attrlen (const struct nlmsghdr *nlh, int hdrlen)
	length of attributes data More...

Message Parsing
int	nlmsg_valid_hdr (const struct nlmsghdr *nlh, int hdrlen)

int	nlmsg_ok (const struct nlmsghdr *nlh, int remaining)
	check if the netlink message fits into the remaining bytes More...

struct nlmsghdr *	nlmsg_next (struct nlmsghdr nlh, int remaining)
	next netlink message in message stream More...

int	nlmsg_parse (struct nlmsghdr nlh, int hdrlen, struct nlattr tb[], int maxtype, struct nla_policy *policy)
	parse attributes of a netlink message More...

struct nlattr *	nlmsg_find_attr (struct nlmsghdr *nlh, int hdrlen, int attrtype)
	nlmsg_find_attr - find a specific attribute in a netlink message More...

int	nlmsg_validate (struct nlmsghdr nlh, int hdrlen, int maxtype, struct nla_policy policy)
	nlmsg_validate - validate a netlink message including attributes More...

Message Building/Access
struct nl_msg *	nlmsg_alloc (void)
	Allocate a new netlink message with the default maximum payload size. More...

struct nl_msg *	nlmsg_alloc_size (size_t max)
	Allocate a new netlink message with maximum payload size specified. More...

struct nl_msg *	nlmsg_inherit (struct nlmsghdr *hdr)
	Allocate a new netlink message and inherit netlink message header. More...

struct nl_msg *	nlmsg_alloc_simple (int nlmsgtype, int flags)
	Allocate a new netlink message. More...

void	nlmsg_set_default_size (size_t max)
	Set the default maximum message payload size for allocated messages. More...

struct nl_msg *	nlmsg_convert (struct nlmsghdr *hdr)
	Convert a netlink message received from a netlink socket to a nl_msg. More...

void *	nlmsg_reserve (struct nl_msg *n, size_t len, int pad)
	Reserve room for additional data in a netlink message. More...

int	nlmsg_append (struct nl_msg n, void data, size_t len, int pad)
	Append data to tail of a netlink message. More...

int	nlmsg_expand (struct nl_msg *n, size_t newlen)
	Expand maximum payload size of a netlink message. More...

struct nlmsghdr *	nlmsg_put (struct nl_msg *n, uint32_t pid, uint32_t seq, int type, int payload, int flags)
	Add a netlink message header to a netlink message. More...

struct nlmsghdr *	nlmsg_hdr (struct nl_msg *n)
	Return actual netlink message. More...

void	nlmsg_get (struct nl_msg *msg)
	Acquire a reference on a netlink message. More...

void	nlmsg_free (struct nl_msg *msg)
	Release a reference from an netlink message. More...

Attributes
void	nlmsg_set_proto (struct nl_msg *msg, int protocol)

int	nlmsg_get_proto (struct nl_msg *msg)

size_t	nlmsg_get_max_size (struct nl_msg *msg)

void	nlmsg_set_src (struct nl_msg msg, struct sockaddr_nl addr)

struct sockaddr_nl *	nlmsg_get_src (struct nl_msg *msg)

void	nlmsg_set_dst (struct nl_msg msg, struct sockaddr_nl addr)

struct sockaddr_nl *	nlmsg_get_dst (struct nl_msg *msg)

void	nlmsg_set_creds (struct nl_msg msg, struct ucred creds)

struct ucred *	nlmsg_get_creds (struct nl_msg *msg)

Netlink Message Type Translations
char *	nl_nlmsgtype2str (int type, char *buf, size_t size)

int	nl_str2nlmsgtype (const char *name)

Netlink Message Flags Translations
char *	nl_nlmsg_flags2str (int flags, char *buf, size_t len)

Direct Parsing
int	nl_msg_parse (struct nl_msg msg, void(cb)(struct nl_object , void ), void *arg)

Dumping
void	nl_msg_dump (struct nl_msg msg, FILE ofd)
	Dump message in human readable format to file descriptor. More...

Detailed Description

Netlink Message Construction/Parsing Interface.

The following information is partly extracted from RFC3549 (ftp://ftp.rfc-editor.org/in-notes/rfc3549.txt)

Message Format: Netlink messages consist of a byte stream with one or multiple Netlink headers and an associated payload. If the payload is too big to fit into a single message it, can be split over multiple Netlink messages, collectively called a multipart message. For multipart messages, the first and all following headers have the NLM_F_MULTI Netlink header flag set, except for the last header which has the Netlink header type NLMSG_DONE.

: The Netlink message header (struct nlmsghdr) is shown below.
0 1 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| Length |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| Type | Flags |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| Sequence Number |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| Process ID (PID) |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

: The netlink message header and payload must be aligned properly:
<------- NLMSG_ALIGN(hlen) ------> <---- NLMSG_ALIGN(len) --->

+----------------------------+- - -+- - - - - - - - - - -+- - -+

| Header | Pad | Payload | Pad |

| struct nlmsghdr | | | |

+----------------------------+- - -+- - - - - - - - - - -+- - -+

: Message Format:
<--- nlmsg_total_size(payload) --->

<-- nlmsg_msg_size(payload) ->

+----------+- - -+-------------+- - -+-------- - -

| nlmsghdr | Pad | Payload | Pad | nlmsghdr

+----------+- - -+-------------+- - -+-------- - -

nlmsg_data(nlh)---^ ^

nlmsg_next(nlh)-----------------------+

: The payload may consist of arbitary data but may have strict alignment and formatting rules depening on the specific netlink families.

: <---------------------- nlmsg_len(nlh) --------------------->

<------ hdrlen ------> <- nlmsg_attrlen(nlh, hdrlen) ->

+----------------------+- - -+--------------------------------+

| Family Header | Pad | Attributes |

+----------------------+- - -+--------------------------------+

nlmsg_attrdata(nlh, hdrlen)---^

The ACK Netlink Message: This message is actually used to denote both an ACK and a NACK. Typically, the direction is from FEC to CPC (in response to an ACK request message). However, the CPC should be able to send ACKs back to FEC when requested.
0 1 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| Netlink message header |

| type = NLMSG_ERROR |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| Error code |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| OLD Netlink message header |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Example: // Various methods exist to create/allocate a new netlink

// message.

//

// nlmsg_alloc() will allocate an empty netlink message with

// a maximum payload size which defaults to the page size of

// the system. This default size can be modified using the

// function nlmsg_set_default_size().

struct nl_msg *msg = nlmsg_alloc();

// Very often, the message type and message flags are known

// at allocation time while the other fields are auto generated:

struct nl_msg *msg = nlmsg_alloc_simple(MY_TYPE, MY_FLAGS);

// Alternatively an existing netlink message header can be used

// to inherit the header values:

struct nlmsghdr hdr = {

.nlmsg_type = MY_TYPE,

.nlmsg_flags = MY_FLAGS,

};

struct nl_msg *msg = nlmsg_inherit(&hdr);

// Last but not least, netlink messages received from netlink sockets

// can be converted into nl_msg objects using nlmsg_convert(). This

// will create a message with a maximum payload size which equals the

// length of the existing netlink message, therefore no more data can

// be appened without calling nlmsg_expand() first.

struct nl_msg *msg = nlmsg_convert(nlh_from_nl_sock);

// Payload may be added to the message via nlmsg_append(). The fourth

// parameter specifies the number of alignment bytes the data should

// be padding with at the end. Common values are 0 to disable it or

// NLMSG_ALIGNTO to ensure proper netlink message padding.

nlmsg_append(msg, &mydata, sizeof(mydata), 0);

// Sometimes it may be necessary to reserve room for data but defer

// the actual copying to a later point, nlmsg_reserve() can be used

// for this purpose:

void *data = nlmsg_reserve(msg, sizeof(mydata), NLMSG_ALIGNTO);

// Attributes may be added using the attributes interface.

// After successful use of the message, the memory must be freed

// using nlmsg_free()

nlmsg_free(msg);

4) Parsing messages: int n;

unsigned char *buf;

struct nlmsghdr *hdr;

n = nl_recv(handle, NULL, &buf);

hdr = (struct nlmsghdr *) buf;

while (nlmsg_ok(hdr, n)) {

// Process message here...

hdr = nlmsg_next(hdr, &n);

}

Macro Definition Documentation

#define NL_AUTO_PID 0

Will cause the netlink pid to be set to the pid assigned to the netlink handle (socket) just before sending the message off.

Note: Requires the use of nl_send_auto_complete()!

#define NL_AUTO_SEQ 0

May be used to refer to a sequence number which should be automatically set just before sending the message off.

Note: Requires the use of nl_send_auto_complete()!

#define NLM_F_ACK 4

Request for an acknowledgment on success.

#define NLM_F_APPEND 0x800

Add to the end of the object list.

#define NLM_F_ATOMIC 0x400

Return an atomic snapshot of the table being referenced.

This may require special privileges because it has the potential to interrupt service in the FE for a longer time.

#define NLM_F_CREATE 0x400

Create config object if it doesn't already exist.

#define NLM_F_DUMP (NLM_F_ROOT|NLM_F_MATCH)

Dump all entries.

#define NLM_F_ECHO 8

Echo this request.

#define NLM_F_EXCL 0x200

Don't replace the config object if it already exists.

#define NLM_F_MATCH 0x200

Return all entries matching criteria passed in message content.

#define NLM_F_MULTI 2

Indicates the message is part of a multipart message terminated by NLMSG_DONE.

#define NLM_F_REPLACE 0x100

Replace existing matching config object with this request.

#define NLM_F_REQUEST 1

Must be set on all request messages (typically from user space to kernel space).

#define NLM_F_ROOT 0x100

Return the complete table instead of a single entry.

#define NLMSG_DONE 0x3

Message terminates a multipart message.

#define NLMSG_ERROR 0x2

The message signals an error and the payload contains a nlmsgerr structure.

This can be looked at as a NACK and typically it is from FEC to CPC.

#define nlmsg_for_each_attr	(	pos,
		nlh,
		hdrlen,
		rem
	)

Value:

nla_for_each_attr(pos, nlmsg_attrdata(nlh, hdrlen), \

nlmsg_attrlen(nlh, hdrlen), rem)

nlmsg_attrlen

int nlmsg_attrlen(const struct nlmsghdr *, int)

length of attributes data

Definition: msg.c:260

nlmsg_attrdata

struct nlattr * nlmsg_attrdata(const struct nlmsghdr *, int)

head of attributes data

Definition: msg.c:249

pos

u8 pos

Definition: ip_set_hash_gen.h:187

nlh

const struct nlmsghdr * nlh

Definition: libnetfilter_conntrack.h:565

nla_for_each_attr

#define nla_for_each_attr(pos, head, len, rem)

Iterate over a stream of attributes.

Definition: attr.h:260

Iterate over a stream of attributes in a message.

pos loop counter, set to current attribute
nlh netlink message header
hdrlen length of family header
rem initialized to len, holds bytes currently remaining in stream

#define nlmsg_for_each_msg	(	pos,
		head,
		len,
		rem
	)

Value:

for (pos = head, rem = len; \
	     nlmsg_ok(pos, rem); \
	     pos = nlmsg_next(pos, &(rem)))

Iterate over a stream of messages.

pos loop counter, set to current message
head head of message stream
len length of message stream
rem initialized to len, holds bytes currently remaining in stream

#define NLMSG_MIN_TYPE 0x10

Lower limit of reserved message types.

#define NLMSG_NOOP 0x1

No operation, message must be ignored.

#define NLMSG_OVERRUN 0x4

The message signals that data got lost.

Function Documentation

void nl_msg_dump	(	struct nl_msg *	msg,
		FILE *	ofd
	)

Dump message in human readable format to file descriptor.

msg Message to print
ofd File descriptor.

References nl_cache_ops::co_hdrsize, nlmsgerr::error, nlmsgerr::msg, nl_cache_ops_associate(), nlmsg_attrdata(), nlmsg_attrlen(), nlmsg_data(), NLMSG_ERROR, nlmsg_free(), nlmsg_get_proto(), nlmsg_hdr(), nlmsg_inherit(), nlmsghdr::nlmsg_len, nlmsg_len(), nlmsg_msg_size(), and nlmsghdr::nlmsg_type.

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int nl_msg_parse	(	struct nl_msg *	msg,
		void()(struct nl_object , void *)	cb,
		void *	arg
	)

References nl_cache_ops_associate(), nl_cache_parse(), NLE_MSGTYPE_NOSUPPORT, nlmsg_get_proto(), nlmsg_hdr(), NULL, nl_parser_param::pp_arg, and nl_parser_param::pp_cb.

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char* nl_nlmsg_flags2str	(	int	flags,
		char *	buf,
		size_t	len
	)

References buf, PRINT_FLAG, REQUEST, and s.

char* nl_nlmsgtype2str	(	int	type,
		char *	buf,
		size_t	size
	)

References __type2str(), and ARRAY_SIZE.

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int nl_str2nlmsgtype ( const char * name )

References __str2type(), and ARRAY_SIZE.

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struct nl_msg* nlmsg_alloc ( void )

Allocate a new netlink message with the default maximum payload size.

Allocates a new netlink message without any further payload. The maximum payload size defaults to PAGESIZE or as otherwise specified with nlmsg_set_default_size().

Returns: Newly allocated netlink message or NULL.

Referenced by nfnl_nft_set_dump_request(), nfnl_nft_setelem_dump_request(), nlmsg_inherit(), and rtnl_neightbl_build_change_request().

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struct nl_msg* nlmsg_alloc_simple	(	int	nlmsgtype,
		int	flags
	)

Allocate a new netlink message.

nlmsgtype Netlink message type
flags Message flags.

Returns: Newly allocated netlink message or NULL.

References flags, NL_DBG, nlmsg_inherit(), and nlmsghdr::nlmsg_type.

Referenced by flnl_lookup_build_request(), main(), nfnlmsg_alloc_simple(), nl_send_simple(), rtnl_class_build_delete_request(), rtnl_link_build_change_request(), rtnl_neightbl_build_change_request(), and rtnl_qdisc_build_delete_request().

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struct nl_msg* nlmsg_alloc_size ( size_t max )

Allocate a new netlink message with maximum payload size specified.

int nlmsg_append	(	struct nl_msg *	n,
		void *	data,
		size_t	len,
		int	pad
	)

Append data to tail of a netlink message.

n netlink message
data data to add
len length of data
pad Number of bytes to align data to.

Extends the netlink message as needed and appends the data of given length to the message.

Returns: 0 on success or a negative error code

References NL_DBG, NLE_NOMEM, nlmsg_reserve(), and NULL.

Referenced by flnl_lookup_build_request(), main(), nl_send_simple(), rtnl_class_build_delete_request(), rtnl_link_build_change_request(), rtnl_neightbl_build_change_request(), rtnl_qdisc_build_delete_request(), and rtnl_route_build_msg().

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struct nlattr* nlmsg_attrdata	(	const struct nlmsghdr *	nlh,
		int	hdrlen
	)

head of attributes data

nlh netlink message header
hdrlen length of family specific header

References data, NLMSG_ALIGN, and nlmsg_data().

Referenced by nl_msg_dump(), nlmsg_find_attr(), nlmsg_parse(), and nlmsg_validate().

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int nlmsg_attrlen	(	const struct nlmsghdr *	nlh,
		int	hdrlen
	)

length of attributes data

nlh netlink message header
hdrlen length of family specific header

References NLMSG_ALIGN, and nlmsg_len().

Referenced by nl_msg_dump(), nlmsg_find_attr(), nlmsg_parse(), and nlmsg_validate().

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struct nl_msg* nlmsg_convert ( struct nlmsghdr * hdr )

Convert a netlink message received from a netlink socket to a nl_msg.

hdr Netlink message received from netlink socket.

Allocates a new netlink message and copies all of the data pointed to by hdr into the new message object.

Returns: Newly allocated netlink message or NULL.

References NLMSG_ALIGN, nlmsg_free(), nlmsghdr::nlmsg_len, nl_msg::nm_nlh, and NULL.

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void* nlmsg_data ( const struct nlmsghdr * nlh )

head of message payload

nlh netlink messsage header

References NLMSG_HDRLEN.

Referenced by genlmsg_parse(), genlmsg_put(), genlmsg_valid_hdr(), genlmsg_validate(), nfnl_dump_packet(), nfnlmsg_family(), nfnlmsg_res_id(), nl_msg_dump(), nla_put(), nla_put_nested(), nla_reserve(), nlmsg_attrdata(), and rtnl_route_parse().

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int nlmsg_expand	(	struct nl_msg *	n,
		size_t	newlen
	)

Expand maximum payload size of a netlink message.

n Netlink message.
newlen New maximum payload size.

Reallocates the payload section of a netlink message and increases the maximum payload size of the message.

Note: Any pointers pointing to old payload block will be stale and need to be refetched. Therfore, do not expand while constructing nested attributes or while reserved data blocks are held.

Returns: 0 on success or a negative error code.

References NLE_INVAL, NLE_NOMEM, nl_msg::nm_nlh, nl_msg::nm_size, and NULL.

struct nlattr* nlmsg_find_attr	(	struct nlmsghdr *	nlh,
		int	hdrlen,
		int	attrtype
	)

nlmsg_find_attr - find a specific attribute in a netlink message

nlh netlink message header
hdrlen length of familiy specific header
attrtype type of attribute to look for

Returns the first attribute which matches the specified type.

References nla_find(), nlmsg_attrdata(), and nlmsg_attrlen().

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void nlmsg_free ( struct nl_msg * msg )

Release a reference from an netlink message.

msg message to release reference from

Frees memory after the last reference has been released.

References BUG, NL_DBG, nl_msg::nm_nlh, and nl_msg::nm_refcnt.

Referenced by flnl_lookup(), flnl_lookup_build_request(), main(), nfnl_ct_add(), nfnl_ct_del(), nfnl_ct_query(), nfnl_log_build_create_request(), 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_build_create_request(), nfnl_queue_msg_build_verdict(), nfnl_queue_msg_send_verdict(), nfnl_queue_msg_send_verdict_payload(), nfnlmsg_alloc_simple(), nl_msg_dump(), nl_send_simple(), nlmsg_convert(), rtnl_addr_add(), rtnl_addr_delete(), rtnl_class_add(), rtnl_class_build_delete_request(), rtnl_class_delete(), rtnl_cls_add(), rtnl_cls_change(), rtnl_cls_delete(), rtnl_link_build_change_request(), rtnl_link_change(), rtnl_neigh_add(), rtnl_neigh_delete(), rtnl_neightbl_build_change_request(), rtnl_neightbl_change(), rtnl_qdisc_add(), rtnl_qdisc_build_delete_request(), rtnl_qdisc_change(), rtnl_qdisc_delete(), rtnl_route_add(), rtnl_route_delete(), rtnl_rule_add(), and rtnl_rule_delete().

void nlmsg_get ( struct nl_msg * msg )

Acquire a reference on a netlink message.

msg message to acquire reference from

References NL_DBG, and nl_msg::nm_refcnt.

struct ucred* nlmsg_get_creds ( struct nl_msg * msg )

References NL_MSG_CRED_PRESENT, nl_msg::nm_creds, nl_msg::nm_flags, and NULL.

Referenced by nl_send_iovec().

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struct sockaddr_nl* nlmsg_get_dst ( struct nl_msg * msg )

References nl_msg::nm_dst.

Referenced by nl_send_iovec().

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size_t nlmsg_get_max_size ( struct nl_msg * msg )

References nl_msg::nm_size.

int nlmsg_get_proto ( struct nl_msg * msg )

References nl_msg::nm_protocol.

Referenced by nl_msg_dump(), and nl_msg_parse().

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struct sockaddr_nl* nlmsg_get_src ( struct nl_msg * msg )

References nl_msg::nm_src.

struct nlmsghdr* nlmsg_hdr ( struct nl_msg * n )

Return actual netlink message.

n netlink message

Returns the actual netlink message casted to the type of the netlink message header.

Returns: A pointer to the netlink message.

References nl_msg::nm_nlh.

Referenced by nfnl_queue_msg_send_verdict_payload(), nl_auto_complete(), nl_cache_parse_and_add(), nl_msg_dump(), nl_msg_parse(), and nl_send().

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struct nl_msg* nlmsg_inherit ( struct nlmsghdr * hdr )

Allocate a new netlink message and inherit netlink message header.

hdr Netlink message header template

Allocates a new netlink message and inherits the original message header. If hdr is not NULL it will be used as a template for the netlink message header, otherwise the header is left blank.

Returns: Newly allocated netlink message or NULL

References nlmsg_alloc(), nlmsghdr::nlmsg_flags, nlmsghdr::nlmsg_pid, nlmsghdr::nlmsg_seq, nlmsghdr::nlmsg_type, and nl_msg::nm_nlh.

Referenced by nl_msg_dump(), and nlmsg_alloc_simple().

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int nlmsg_len ( const struct nlmsghdr * nlh )

length of message payload

nlh netlink message header

References NLMSG_HDRLEN, and nlmsghdr::nlmsg_len.

Referenced by nl_msg_dump(), nla_put_nested(), nlmsg_attrlen(), and nlmsg_reserve().

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int nlmsg_msg_size ( int payload )

length of netlink message not including padding

payload length of message payload

References NLMSG_HDRLEN, and payload.

Referenced by nl_msg_dump(), nlmsg_padlen(), nlmsg_total_size(), and nlmsg_valid_hdr().

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struct nlmsghdr* nlmsg_next	(	struct nlmsghdr *	nlh,
		int *	remaining
	)

next netlink message in message stream

nlh netlink message header
remaining number of bytes remaining in message stream

Returns: the next netlink message in the message stream and decrements remaining by the size of the current message.

References NLMSG_ALIGN, and nlmsghdr::nlmsg_len.

int nlmsg_ok	(	const struct nlmsghdr *	nlh,
		int	remaining
	)

check if the netlink message fits into the remaining bytes

nlh netlink message header
remaining number of bytes remaining in message stream

References nlmsghdr::nlmsg_len.

int nlmsg_padlen ( int payload )

length of padding at the message's tail

payload length of message payload

References nlmsg_msg_size(), and nlmsg_total_size().

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

parse attributes of a netlink message

nlh netlink message header
hdrlen length of family specific header
tb destination array with maxtype+1 elements
maxtype maximum attribute type to be expected
policy validation policy

See nla_parse()

References nla_parse(), NLE_MSG_TOOSHORT, nlmsg_attrdata(), nlmsg_attrlen(), and nlmsg_valid_hdr().

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struct nlmsghdr* nlmsg_put	(	struct nl_msg *	n,
		uint32_t	pid,
		uint32_t	seq,
		int	type,
		int	payload,
		int	flags
	)

Add a netlink message header to a netlink message.

n netlink message
pid netlink process id or NL_AUTO_PID
seq sequence number of message or NL_AUTO_SEQ
type message type
payload length of message payload
flags message flags

Adds or overwrites the netlink message header in an existing message object. If payload is greater-than zero additional room will be reserved, f.e. for family specific headers. It can be accesed via nlmsg_data().