Messages

Netlink Message Construction/Parsing Interface. More...

Modules
	Attributes
	Netlink Attributes Construction/Parsing Interface.

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.
#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.

Netlink Message Type Translations
char *	nl_nlmsgtype2str (int type, char *buf, size_t size)
int	nl_str2nlmsgtype (const char *name)

Size Calculations
int	nlmsg_msg_size (int payload)
	length of netlink message not including padding
int	nlmsg_total_size (int payload)
	length of netlink message including padding
int	nlmsg_padlen (int payload)
	length of padding at the message's tail

Payload Access
void *	nlmsg_data (const struct nlmsghdr *nlh)
	head of message payload
void *	nlmsg_tail (const struct nlmsghdr *nlh)
int	nlmsg_len (const struct nlmsghdr *nlh)
	length of message payload

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

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
struct nlmsghdr *	nlmsg_next (struct nlmsghdr *nlh, int *remaining)
	next netlink message in message stream
int	nlmsg_parse (struct nlmsghdr *nlh, int hdrlen, struct nlattr *tb[], int maxtype, struct nla_policy *policy)
	parse attributes of a netlink message
struct nlattr *	nlmsg_find_attr (struct nlmsghdr *nlh, int hdrlen, int attrtype)
	nlmsg_find_attr - find a specific attribute in a netlink message
int	nlmsg_validate (struct nlmsghdr *nlh, int hdrlen, int maxtype, struct nla_policy *policy)
	nlmsg_validate - validate a netlink message including attributes

Message Building/Access
struct nl_msg *	nlmsg_alloc (void)
	Allocate a new netlink message with the default maximum payload size.
struct nl_msg *	nlmsg_alloc_size (size_t max)
	Allocate a new netlink message with maximum payload size specified.
struct nl_msg *	nlmsg_inherit (struct nlmsghdr *hdr)
	Allocate a new netlink message and inherit netlink message header.
struct nl_msg *	nlmsg_alloc_simple (int nlmsgtype, int flags)
	Allocate a new netlink message.
void	nlmsg_set_default_size (size_t max)
	Set the default maximum message payload size for allocated messages.
struct nl_msg *	nlmsg_convert (struct nlmsghdr *hdr)
	Convert a netlink message received from a netlink socket to a nl_msg.
void *	nlmsg_reserve (struct nl_msg *n, size_t len, int pad)
	Reserve room for additional data in a netlink message.
int	nlmsg_append (struct nl_msg *n, void *data, size_t len, int pad)
	Append data to tail of a netlink message.
int	nlmsg_expand (struct nl_msg *n, size_t newlen)
	Expand maximum payload size of a netlink message.
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.
struct nlmsghdr *	nlmsg_hdr (struct nl_msg *n)
	Return actual netlink message.
void	nlmsg_free (struct nl_msg *n)
	Free a netlink message.

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 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.

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

Standard message flags
#define	NLM_F_REQUEST   1
	Must be set on all request messages (typically from user space to kernel space).
#define	NLM_F_MULTI   2
	Indicates the message is part of a multipart message terminated by NLMSG_DONE.
#define	NLM_F_ACK   4
	Request for an acknowledgment on success.
#define	NLM_F_ECHO   8
	Echo this request.

Additional message flags for GET requests
#define	NLM_F_ROOT   0x100
	Return the complete table instead of a single entry.
#define	NLM_F_MATCH   0x200
	Return all entries matching criteria passed in message content.
#define	NLM_F_ATOMIC   0x400
	Return an atomic snapshot of the table being referenced.
#define	NLM_F_DUMP   (NLM_F_ROOT|NLM_F_MATCH)
	Dump all entries.

Additional messsage flags for NEW requests
#define	NLM_F_REPLACE   0x100
	Replace existing matching config object with this request.
#define	NLM_F_EXCL   0x200
	Don't replace the config object if it already exists.
#define	NLM_F_CREATE   0x400
	Create config object if it doesn't already exist.
#define	NLM_F_APPEND   0x800
	Add to the end of the object list.

Standard Message types
#define	NLMSG_NOOP   0x1
	No operation, message must be ignored.
#define	NLMSG_ERROR   0x2
	The message signals an error and the payload contains a nlmsgerr structure.
#define	NLMSG_DONE   0x3
	Message terminates a multipart message.
#define	NLMSG_OVERRUN   0x4
	The message signals that data got lost.
#define	NLMSG_MIN_TYPE   0x10
	Lower limit of reserved message types.

Detailed Description

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

NL_AUTO_PID

#define NL_AUTO_PID   0

Note

Requires the use of nl_send_auto_complete()!

Definition at line 32 of file msg.h.

NL_AUTO_SEQ

#define NL_AUTO_SEQ   0

Note

Requires the use of nl_send_auto_complete()!

Definition at line 41 of file msg.h.

nlmsg_for_each_attr

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

Value:

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

Parameters

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

Definition at line 126 of file msg.h.

NLM_F_REQUEST

#define NLM_F_REQUEST   1

Definition at line 65 of file netlink-kernel.h.

NLM_F_ROOT

#define NLM_F_ROOT   0x100

Definition at line 94 of file netlink-kernel.h.

NLM_F_REPLACE

#define NLM_F_REPLACE   0x100

Definition at line 124 of file netlink-kernel.h.

NLMSG_NOOP

#define NLMSG_NOOP   0x1

Definition at line 152 of file netlink-kernel.h.

nlmsg_for_each_msg

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

Value:

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

Parameters

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

Definition at line 137 of file msg.h.

NLM_F_MULTI

#define NLM_F_MULTI   2

Definition at line 71 of file netlink-kernel.h.

NLM_F_ACK

#define NLM_F_ACK   4

Definition at line 76 of file netlink-kernel.h.

NLM_F_ECHO

#define NLM_F_ECHO   8

Definition at line 81 of file netlink-kernel.h.

NLM_F_MATCH

#define NLM_F_MATCH   0x200

Definition at line 99 of file netlink-kernel.h.

NLM_F_ATOMIC

#define NLM_F_ATOMIC   0x400

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

Definition at line 106 of file netlink-kernel.h.

NLM_F_DUMP

#define NLM_F_DUMP   (NLM_F_ROOT|NLM_F_MATCH)

Definition at line 111 of file netlink-kernel.h.

NLM_F_EXCL

#define NLM_F_EXCL   0x200

Definition at line 129 of file netlink-kernel.h.

NLM_F_CREATE

#define NLM_F_CREATE   0x400

Definition at line 134 of file netlink-kernel.h.

NLM_F_APPEND

#define NLM_F_APPEND   0x800

Definition at line 139 of file netlink-kernel.h.

NLMSG_ERROR

#define NLMSG_ERROR   0x2

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

Definition at line 159 of file netlink-kernel.h.

NLMSG_DONE

#define NLMSG_DONE   0x3

Definition at line 164 of file netlink-kernel.h.

NLMSG_OVERRUN

#define NLMSG_OVERRUN   0x4

Definition at line 169 of file netlink-kernel.h.

NLMSG_MIN_TYPE

#define NLMSG_MIN_TYPE   0x10

Definition at line 174 of file netlink-kernel.h.

Function Documentation

nlmsg_msg_size()

int nlmsg_msg_size

(

int

payload

)

Parameters

payload

length of message payload

Definition at line 184 of file msg.c.

{
        return NLMSG_HDRLEN + payload;
}

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

nlmsg_total_size()

int nlmsg_total_size

(

int

payload

)

Parameters

payload

length of message payload

Definition at line 193 of file msg.c.

{
        return NLMSG_ALIGN(nlmsg_msg_size(payload));
}

References nlmsg_msg_size().

Referenced by nlmsg_padlen(), and nlmsg_set_default_size().

nlmsg_padlen()

int nlmsg_padlen

(

int

payload

)

Parameters

payload

length of message payload

Definition at line 202 of file msg.c.

{
        return nlmsg_total_size(payload) - nlmsg_msg_size(payload);
}

References nlmsg_msg_size(), and nlmsg_total_size().

nlmsg_data()

void * nlmsg_data

(

const struct nlmsghdr *

nlh

)

Parameters

nlh	netlink messsage header

Definition at line 218 of file msg.c.

{
        return (unsigned char *) nlh + NLMSG_HDRLEN;
}

Referenced by genlmsg_put(), nfnlmsg_family(), nfnlmsg_res_id(), nl_msg_dump(), nla_put(), nla_put_nested(), nla_reserve(), and nlmsg_attrdata().

nlmsg_tail()

void * nlmsg_tail

(

const struct nlmsghdr *

nlh

)

Definition at line 223 of file msg.c.

{
        return (unsigned char *) nlh + NLMSG_ALIGN(nlh->nlmsg_len);
}

nlmsg_len()

int nlmsg_len

(

const struct nlmsghdr *

nlh

)

Parameters

nlh	netlink message header

Definition at line 232 of file msg.c.

{
        return nlh->nlmsg_len - NLMSG_HDRLEN;
}

References nlmsghdr::nlmsg_len.

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

nlmsg_attrdata()

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

Parameters

nlh	netlink message header
hdrlen	length of family specific header

Definition at line 249 of file msg.c.

{
        unsigned char *data = nlmsg_data(nlh);
        return (struct nlattr *) (data + NLMSG_ALIGN(hdrlen));
}

References nlmsg_data().

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

nlmsg_attrlen()

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

Parameters

nlh	netlink message header
hdrlen	length of family specific header

Definition at line 260 of file msg.c.

{
        return nlmsg_len(nlh) - NLMSG_ALIGN(hdrlen);
}

References nlmsg_len().

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

nlmsg_valid_hdr()

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

Definition at line 272 of file msg.c.

{
        if (nlh->nlmsg_len < nlmsg_msg_size(hdrlen))
                return 0;
 
        return 1;
}

nlmsg_ok()

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

Parameters

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

Definition at line 285 of file msg.c.

{
        return (remaining >= (int)sizeof(struct nlmsghdr) &&
                nlh->nlmsg_len >= sizeof(struct nlmsghdr) &&
                nlh->nlmsg_len <= remaining);
}

References nlmsghdr::nlmsg_len.

nlmsg_next()

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

Parameters

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.

Definition at line 300 of file msg.c.

{
        int totlen = NLMSG_ALIGN(nlh->nlmsg_len);
 
        *remaining -= totlen;
 
        return (struct nlmsghdr *) ((unsigned char *) nlh + totlen);
}

References nlmsghdr::nlmsg_len.

nlmsg_parse()

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

Parameters

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()

Definition at line 319 of file msg.c.

{
        if (!nlmsg_valid_hdr(nlh, hdrlen))
                return nl_errno(EINVAL);
 
        return nla_parse(tb, maxtype, nlmsg_attrdata(nlh, hdrlen),
                         nlmsg_attrlen(nlh, hdrlen), policy);
}

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

nlmsg_find_attr()

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

Parameters

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.

Definition at line 337 of file msg.c.

{
        return nla_find(nlmsg_attrdata(nlh, hdrlen),
                        nlmsg_attrlen(nlh, hdrlen), attrtype);
}

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

nlmsg_validate()

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

Parameters

nlh	netlinket message header
hdrlen	length of familiy specific header
maxtype	maximum attribute type to be expected
policy	validation policy

Definition at line 350 of file msg.c.

{
        if (!nlmsg_valid_hdr(nlh, hdrlen))
                return nl_errno(EINVAL);
 
        return nla_validate(nlmsg_attrdata(nlh, hdrlen),
                            nlmsg_attrlen(nlh, hdrlen), maxtype, policy);
}

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

nlmsg_alloc()

struct nl_msg * nlmsg_alloc

(

void

)

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.

Definition at line 401 of file msg.c.

{
        return __nlmsg_alloc(default_msg_size);
}

Referenced by nlmsg_inherit(), and rtnl_neightbl_build_change_request().

nlmsg_alloc_size()

struct nl_msg * nlmsg_alloc_size

(

size_t

max

)

Definition at line 409 of file msg.c.

{
        return __nlmsg_alloc(max);
}

nlmsg_inherit()

struct nl_msg * nlmsg_inherit

(

struct nlmsghdr *

hdr

)

Parameters

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

Definition at line 424 of file msg.c.

{
        struct nl_msg *nm;
 
        nm = nlmsg_alloc();
        if (nm && hdr) {
                struct nlmsghdr *new = nm->nm_nlh;
 
                new->nlmsg_type = hdr->nlmsg_type;
                new->nlmsg_flags = hdr->nlmsg_flags;
                new->nlmsg_seq = hdr->nlmsg_seq;
                new->nlmsg_pid = hdr->nlmsg_pid;
        }
 
        return nm;
}

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

Referenced by nl_msg_dump(), and nlmsg_alloc_simple().

nlmsg_alloc_simple()

struct nl_msg * nlmsg_alloc_simple	(	int	nlmsgtype,
		int	flags
	)

Parameters

nlmsgtype	Netlink message type
flags	Message flags.

Returns

Newly allocated netlink message or NULL.

Definition at line 448 of file msg.c.

{
        struct nl_msg *msg;
        struct nlmsghdr nlh = {
                .nlmsg_type = nlmsgtype,
                .nlmsg_flags = flags,
        };
 
        msg = nlmsg_inherit(&nlh);
        if (msg)
                NL_DBG(2, "msg %p: Allocated new simple message\n", msg);
 
        return msg;
}

References nlmsg_inherit(), and nlmsghdr::nlmsg_type.

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

nlmsg_set_default_size()

void nlmsg_set_default_size

(

size_t

max

)

Parameters

max	Size of payload in bytes.

Definition at line 467 of file msg.c.

{
        if (max < nlmsg_total_size(0))
                max = nlmsg_total_size(0);
 
        default_msg_size = max;
}

References nlmsg_total_size().

nlmsg_convert()

struct nl_msg * nlmsg_convert

(

struct nlmsghdr *

hdr

)

Parameters

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.

Definition at line 484 of file msg.c.

{
        struct nl_msg *nm;
 
        nm = __nlmsg_alloc(NLMSG_ALIGN(hdr->nlmsg_len));
        if (!nm)
                goto errout;
 
        memcpy(nm->nm_nlh, hdr, hdr->nlmsg_len);
 
        return nm;
errout:
        nlmsg_free(nm);
        return NULL;
}

References nlmsg_free(), and nlmsghdr::nlmsg_len.

nlmsg_reserve()

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

Parameters

n	netlink message
len	length of additional data to reserve room for
pad	number of bytes to align data to

Reserves room for additional data at the tail of the an existing netlink message. Eventual padding required will be zeroed out.

Returns

Pointer to start of additional data tailroom or NULL.

Definition at line 512 of file msg.c.

{
        void *buf = n->nm_nlh;
        size_t nlmsg_len = n->nm_nlh->nlmsg_len;
        size_t tlen;
 
        tlen = pad ? ((len + (pad - 1)) & ~(pad - 1)) : len;
 
        if ((tlen + nlmsg_len) > n->nm_size) {
                nl_errno(ENOBUFS);
                return NULL;
        }
 
        buf += nlmsg_len;
        n->nm_nlh->nlmsg_len += tlen;
 
        if (tlen > len)
                memset(buf + len, 0, tlen - len);
 
        NL_DBG(2, "msg %p: Reserved %zu bytes, pad=%d, nlmsg_len=%d\n",
                  n, len, pad, n->nm_nlh->nlmsg_len);
 
        return buf;
}

References nlmsg_len().

Referenced by nlmsg_append(), and nlmsg_put().

nlmsg_append()

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

Parameters

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

Definition at line 549 of file msg.c.

{
        void *tmp;
 
        tmp = nlmsg_reserve(n, len, pad);
        if (tmp == NULL)
                return nl_errno(ENOMEM);
 
        memcpy(tmp, data, len);
        NL_DBG(2, "msg %p: Appended %zu bytes with padding %d\n", n, len, pad);
 
        return 0;
}

References nlmsg_reserve().

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

nlmsg_expand()

int nlmsg_expand	(	struct nl_msg *	n,
		size_t	newlen
	)

Parameters

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.

Definition at line 577 of file msg.c.

{
        void *tmp;
 
        if (newlen <= n->nm_size)
                return nl_errno(EINVAL);
 
        tmp = realloc(n->nm_nlh, newlen);
        if (tmp == NULL)
                return nl_errno(ENOMEM);
 
        n->nm_nlh = tmp;
        n->nm_size = newlen;
 
        return 0;
}

nlmsg_put()

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

Parameters

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().

Returns

A pointer to the netlink message header or NULL.

Definition at line 610 of file msg.c.

{
        struct nlmsghdr *nlh;
 
        if (n->nm_nlh->nlmsg_len < NLMSG_HDRLEN)
                BUG();
 
        nlh = (struct nlmsghdr *) n->nm_nlh;
        nlh->nlmsg_type = type;
        nlh->nlmsg_flags = flags;
        nlh->nlmsg_pid = pid;
        nlh->nlmsg_seq = seq;
 
        NL_DBG(2, "msg %p: Added netlink header type=%d, flags=%d, pid=%d, "
                  "seq=%d\n", n, type, flags, pid, seq);
 
        if (payload > 0 &&
            nlmsg_reserve(n, payload, NLMSG_ALIGNTO) == NULL)
                return NULL;
 
        return nlh;
}

References nlmsghdr::nlmsg_flags, nlmsghdr::nlmsg_pid, nlmsg_reserve(), nlmsghdr::nlmsg_seq, and nlmsghdr::nlmsg_type.

Referenced by genlmsg_put(), and nfnlmsg_put().

nlmsg_hdr()

struct nlmsghdr * nlmsg_hdr

(

struct nl_msg *

n

)

Parameters

n	netlink message

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

Returns

A pointer to the netlink message.

Definition at line 643 of file msg.c.

{
        return n->nm_nlh;
}

Referenced by nl_cache_parse_and_add(), nl_msg_dump(), nl_send_auto_complete(), and nl_sendmsg().

nlmsg_free()

void nlmsg_free

(

struct nl_msg *

n

)

Parameters

n	netlink message

Destroys a netlink message and frees up all used memory.

Precondition

The message must be unused.

Definition at line 656 of file msg.c.

{
        if (!n)
                return;
 
        free(n->nm_nlh);
        free(n);
        NL_DBG(2, "msg %p: Freed\n", n);
}

Referenced by flnl_lookup(), flnl_lookup_build_request(), nfnlmsg_alloc_simple(), nl_msg_dump(), nl_send_simple(), nlmsg_convert(), rtnl_addr_add(), rtnl_addr_delete(), rtnl_class_add(), rtnl_cls_add(), rtnl_cls_change(), rtnl_cls_delete(), rtnl_link_build_change_request(), rtnl_link_change(), rtnl_neigh_add(), rtnl_neigh_change(), rtnl_neigh_delete(), rtnl_neightbl_build_change_request(), rtnl_neightbl_change(), rtnl_qdisc_add(), rtnl_qdisc_change(), rtnl_qdisc_delete(), rtnl_rule_add(), and rtnl_rule_delete().

nlmsg_set_proto()

void nlmsg_set_proto	(	struct nl_msg *	msg,
		int	protocol
	)

Definition at line 673 of file msg.c.

{
        msg->nm_protocol = protocol;
}

nlmsg_get_proto()

int nlmsg_get_proto

(

struct nl_msg *

msg

)

Definition at line 678 of file msg.c.

{
        return msg->nm_protocol;
}

nlmsg_get_max_size()

size_t nlmsg_get_max_size

(

struct nl_msg *

msg

)

Definition at line 683 of file msg.c.

{
        return msg->nm_size;
}

nlmsg_set_src()

void nlmsg_set_src	(	struct nl_msg *	msg,
		struct sockaddr_nl *	addr
	)

Definition at line 688 of file msg.c.

{
        memcpy(&msg->nm_src, addr, sizeof(*addr));
}

nlmsg_get_src()

struct sockaddr_nl * nlmsg_get_src

(

struct nl_msg *

msg

)

Definition at line 693 of file msg.c.

{
        return &msg->nm_src;
}

nlmsg_set_dst()

void nlmsg_set_dst	(	struct nl_msg *	msg,
		struct sockaddr_nl *	addr
	)

Definition at line 698 of file msg.c.

{
        memcpy(&msg->nm_dst, addr, sizeof(*addr));
}

nlmsg_get_dst()

struct sockaddr_nl * nlmsg_get_dst

(

struct nl_msg *

msg

)

Definition at line 703 of file msg.c.

{
        return &msg->nm_dst;
}

nlmsg_set_creds()

void nlmsg_set_creds	(	struct nl_msg *	msg,
		struct ucred *	creds
	)

Definition at line 708 of file msg.c.

{
        memcpy(&msg->nm_creds, creds, sizeof(*creds));
        msg->nm_flags |= NL_MSG_CRED_PRESENT;
}

nlmsg_get_creds()

struct ucred * nlmsg_get_creds

(

struct nl_msg *

msg

)

Definition at line 714 of file msg.c.

{
        if (msg->nm_flags & NL_MSG_CRED_PRESENT)
                return &msg->nm_creds;
        return NULL;
}

nl_nlmsgtype2str()

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

Definition at line 735 of file msg.c.

{
        return __type2str(type, buf, size, nl_msgtypes,
                          ARRAY_SIZE(nl_msgtypes));
}

nl_str2nlmsgtype()

int nl_str2nlmsgtype

(

const char *

name

)

Definition at line 741 of file msg.c.

{
        return __str2type(name, nl_msgtypes, ARRAY_SIZE(nl_msgtypes));
}

nl_nlmsg_flags2str()

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

Definition at line 753 of file msg.c.

{
        memset(buf, 0, len);
 
#define PRINT_FLAG(f) \
        if (flags & NLM_F_##f) { \
                flags &= ~NLM_F_##f; \
                strncat(buf, #f, len - strlen(buf) - 1); \
                if (flags) \
                        strncat(buf, ",", len - strlen(buf) - 1); \
        }
        
        PRINT_FLAG(REQUEST);
        PRINT_FLAG(MULTI);
        PRINT_FLAG(ACK);
        PRINT_FLAG(ECHO);
        PRINT_FLAG(ROOT);
        PRINT_FLAG(MATCH);
        PRINT_FLAG(ATOMIC);
        PRINT_FLAG(REPLACE);
        PRINT_FLAG(EXCL);
        PRINT_FLAG(CREATE);
        PRINT_FLAG(APPEND);
 
        if (flags) {
                char s[32];
                snprintf(s, sizeof(s), "0x%x", flags);
                strncat(buf, s, len - strlen(buf) - 1);
        }
#undef PRINT_FLAG
 
        return buf;
}

nl_msg_parse()

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

Definition at line 809 of file msg.c.

{
        struct nl_cache_ops *ops;
        struct nl_parser_param p = {
                .pp_cb = parse_cb
        };
        struct dp_xdata x = {
                .cb = cb,
                .arg = arg,
        };
 
        ops = nl_cache_ops_associate(nlmsg_get_proto(msg),
                                     nlmsg_hdr(msg)->nlmsg_type);
        if (ops == NULL)
                return nl_error(ENOENT, "Unknown message type %d",
                                nlmsg_hdr(msg)->nlmsg_type);
        p.pp_arg = &x;
 
        return nl_cache_parse(ops, NULL, nlmsg_hdr(msg), &p);
}

nl_msg_dump()

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

Parameters

msg	Message to print
ofd	File descriptor.

Definition at line 947 of file msg.c.

{
        struct nlmsghdr *hdr = nlmsg_hdr(msg);
        
        fprintf(ofd, 
        "--------------------------   BEGIN NETLINK MESSAGE "
        "---------------------------\n");
 
        fprintf(ofd, "  [HEADER] %Zu octets\n", sizeof(struct nlmsghdr));
        print_hdr(ofd, msg);
 
        if (hdr->nlmsg_type == NLMSG_ERROR &&
            hdr->nlmsg_len >= nlmsg_msg_size(sizeof(struct nlmsgerr))) {
                struct nl_msg *errmsg;
                struct nlmsgerr *err = nlmsg_data(hdr);
                char buf[256];
 
                fprintf(ofd, "  [ERRORMSG] %Zu octets\n", sizeof(*err));
                fprintf(ofd, "    .error = %d \"%s\"\n", err->error,
                        strerror_r(-err->error, buf, sizeof(buf)));
                fprintf(ofd, "  [ORIGINAL MESSAGE] %Zu octets\n", sizeof(*hdr));
 
                errmsg = nlmsg_inherit(&err->msg);
                print_hdr(ofd, errmsg);
                nlmsg_free(errmsg);
        } else if (nlmsg_len(hdr) > 0) {
                struct nl_cache_ops *ops;
                int payloadlen = nlmsg_len(hdr);
                int attrlen = 0;
 
                ops = nl_cache_ops_associate(nlmsg_get_proto(msg),
                                             hdr->nlmsg_type);
                if (ops) {
                        attrlen = nlmsg_attrlen(hdr, ops->co_hdrsize);
                        payloadlen -= attrlen;
                }
 
                fprintf(ofd, "  [PAYLOAD] %d octets\n", payloadlen);
                dump_hex(ofd, nlmsg_data(hdr), payloadlen, 0);
 
                if (attrlen) {
                        struct nlattr *attrs;
                        int attrlen;
                        
                        attrs = nlmsg_attrdata(hdr, ops->co_hdrsize);
                        attrlen = nlmsg_attrlen(hdr, ops->co_hdrsize);
                        dump_attrs(ofd, attrs, attrlen, 0);
                }
        }
 
        fprintf(ofd, 
        "---------------------------  END NETLINK MESSAGE   "
        "---------------------------\n");
}

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