Generic Netlink
[Netlink Families]

Modules
	Generic Netlink Family
	Management

---

Detailed Description

Message Format

  <------- NLMSG_ALIGN(hlen) ------> <---- NLMSG_ALIGN(len) --->
 +----------------------------+- - -+- - - - - - - - - - -+- - -+
 |           Header           | Pad |       Payload       | Pad |
 |      struct nlmsghdr       |     |                     |     |
 +----------------------------+- - -+- - - - - - - - - - -+- - -+

  <-------- GENL_HDRLEN -------> <--- hdrlen -->
                                 <------- genlmsg_len(ghdr) ------>
 +------------------------+- - -+---------------+- - -+------------+
 | Generic Netlink Header | Pad | Family Header | Pad | Attributes |
 |    struct genlmsghdr   |     |               |     |            |
 +------------------------+- - -+---------------+- - -+------------+
 genlmsg_data(ghdr)--------------^                     ^
 genlmsg_attrdata(ghdr, hdrlen)-------------------------

Example

 #include <netlink/netlink.h>
 #include <netlink/genl/genl.h>
 #include <netlink/genl/ctrl.h>

 struct nl_handle *sock;
 struct nl_msg *msg;
 int family;

 // Allocate a new netlink socket
 sock = nl_handle_alloc();

 // Connect to generic netlink socket on kernel side
 genl_connect(sock);

 // Ask kernel to resolve family name to family id
 family = genl_ctrl_resolve(sock, "generic_netlink_family_name");

 // Construct a generic netlink by allocating a new message, fill in
 // the header and append a simple integer attribute.
 msg = nlmsg_alloc();
 genlmsg_put(msg, NL_AUTO_PID, NL_AUTO_SEQ, family, 0, NLM_F_ECHO,
             CMD_FOO_GET, FOO_VERSION);
 nla_put_u32(msg, ATTR_FOO, 123);

 // Send message over netlink socket
 nl_send_auto_complete(sock, msg);

 // Free message
 nlmsg_free(msg);

 // Prepare socket to receive the answer by specifying the callback
 // function to be called for valid messages.
 nl_socket_modify_cb(sock, NL_CB_VALID, NL_CB_CUSTOM, parse_cb, NULL);

 // Wait for the answer and receive it
 nl_recvmsgs_default(sock);

 static int parse_cb(struct nl_msg *msg, void *arg)
 {
     struct nlmsghdr *nlh = nlmsg_hdr(msg);
     struct nlattr *attrs[ATTR_MAX+1];

     // Validate message and parse attributes
     genlmsg_parse(nlh, 0, attrs, ATTR_MAX, policy);

     if (attrs[ATTR_FOO]) {
         uint32_t value = nla_get_u32(attrs[ATTR_FOO]);
         ...
     }

     return 0;
 }

---

Function Documentation

int genl_send_simple	(	struct nl_handle *	handle,
		int	family,
		int	cmd,
		int	version,
		int	flags
	)

Parameters:

	handle	Netlink handle.
	family	Generic netlink family
	cmd	Command
	version	Version
	flags	Additional netlink message flags.

Fills out a routing netlink request message and sends it out using nl_send_simple().

Returns:

0 on success or a negative error code.

Definition at line 128 of file genl.c.

References nl_send_simple().

void* genlmsg_data

(

const struct genlmsghdr *

gnlh

)

Parameters:

gnlh

genetlink messsage header

Definition at line 191 of file genl.c.

Referenced by genlmsg_attrdata().

int genlmsg_len

(

const struct genlmsghdr *

gnlh

)

Parameters:

gnlh

genetlink message header

Definition at line 200 of file genl.c.

References nlmsghdr::nlmsg_len.

Referenced by genlmsg_attrlen().

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

Parameters:

	gnlh	generic netlink message header
	hdrlen	length of family specific header

Definition at line 212 of file genl.c.

References genlmsg_data().

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

Parameters:

	gnlh	generic netlink message header
	hdrlen	length of family specific header

Definition at line 222 of file genl.c.

References genlmsg_len().

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

Parameters:

	msg	netlink message
	pid	netlink process id or NL_AUTO_PID
	seq	sequence number of message or NL_AUTO_SEQ
	family	generic netlink family
	hdrlen	length of user specific header
	flags	message flags
	cmd	generic netlink command
	version	protocol version

Returns pointer to user specific header.

Definition at line 247 of file genl.c.

References nlmsg_data(), and nlmsg_put().