OpenWrt – Rev 4
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/*
* lib/genl/genl.c Generic Netlink
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation version 2.1
* of the License.
*
* Copyright (c) 2003-2008 Thomas Graf <tgraf@suug.ch>
*/
/**
* @defgroup genl Generic Netlink
*
* @par Message Format
* @code
* <------- NLMSG_ALIGN(hlen) ------> <---- NLMSG_ALIGN(len) --->
* +----------------------------+- - -+- - - - - - - - - - -+- - -+
* | Header | Pad | Payload | Pad |
* | struct nlmsghdr | | | |
* +----------------------------+- - -+- - - - - - - - - - -+- - -+
* @endcode
* @code
* <-------- GENL_HDRLEN -------> <--- hdrlen -->
* <------- genlmsg_len(ghdr) ------>
* +------------------------+- - -+---------------+- - -+------------+
* | Generic Netlink Header | Pad | Family Header | Pad | Attributes |
* | struct genlmsghdr | | | | |
* +------------------------+- - -+---------------+- - -+------------+
* genlmsg_data(ghdr)--------------^ ^
* genlmsg_attrdata(ghdr, hdrlen)-------------------------
* @endcode
*
* @par Example
* @code
* #include <netlink/netlink.h>
* #include <netlink/genl/genl.h>
* #include <netlink/genl/ctrl.h>
*
* struct nl_sock *sock;
* struct nl_msg *msg;
* int family;
*
* // Allocate a new netlink socket
* sock = nl_socket_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;
* }
* @endcode
* @{
*/
#include <netlink-generic.h>
#include <netlink/netlink.h>
#include <netlink/genl/genl.h>
#include <netlink/utils.h>
/**
* @name Socket Creating
* @{
*/
int genl_connect(struct nl_sock *sk)
{
return nl_connect(sk, NETLINK_GENERIC);
}
/** @} */
/**
* @name Sending
* @{
*/
/**
* Send trivial generic netlink message
* @arg sk Netlink socket.
* @arg family Generic netlink family
* @arg cmd Command
* @arg version Version
* @arg flags Additional netlink message flags.
*
* Fills out a routing netlink request message and sends it out
* using nl_send_simple().
*
* @return 0 on success or a negative error code.
*/
int genl_send_simple(struct nl_sock *sk, int family, int cmd,
int version, int flags)
{
struct genlmsghdr hdr = {
.cmd = cmd,
.version = version,
};
return nl_send_simple(sk, family, flags, &hdr, sizeof(hdr));
}
/** @} */
/**
* @name Message Parsing
* @{
*/
int genlmsg_valid_hdr(struct nlmsghdr *nlh, int hdrlen)
{
struct genlmsghdr *ghdr;
if (!nlmsg_valid_hdr(nlh, GENL_HDRLEN))
return 0;
ghdr = nlmsg_data(nlh);
if (genlmsg_len(ghdr) < NLMSG_ALIGN(hdrlen))
return 0;
return 1;
}
int genlmsg_validate(struct nlmsghdr *nlh, int hdrlen, int maxtype,
struct nla_policy *policy)
{
struct genlmsghdr *ghdr;
if (!genlmsg_valid_hdr(nlh, hdrlen))
return -NLE_MSG_TOOSHORT;
ghdr = nlmsg_data(nlh);
return nla_validate(genlmsg_attrdata(ghdr, hdrlen),
genlmsg_attrlen(ghdr, hdrlen), maxtype, policy);
}
int genlmsg_parse(struct nlmsghdr *nlh, int hdrlen, struct nlattr *tb[],
int maxtype, struct nla_policy *policy)
{
struct genlmsghdr *ghdr;
if (!genlmsg_valid_hdr(nlh, hdrlen))
return -NLE_MSG_TOOSHORT;
ghdr = nlmsg_data(nlh);
return nla_parse(tb, maxtype, genlmsg_attrdata(ghdr, hdrlen),
genlmsg_attrlen(ghdr, hdrlen), policy);
}
/**
* Get head of message payload
* @arg gnlh genetlink messsage header
*/
void *genlmsg_data(const struct genlmsghdr *gnlh)
{
return ((unsigned char *) gnlh + GENL_HDRLEN);
}
/**
* Get lenght of message payload
* @arg gnlh genetlink message header
*/
int genlmsg_len(const struct genlmsghdr *gnlh)
{
struct nlmsghdr *nlh = (struct nlmsghdr *)((unsigned char *)gnlh -
NLMSG_HDRLEN);
return (nlh->nlmsg_len - GENL_HDRLEN - NLMSG_HDRLEN);
}
/**
* Get head of attribute data
* @arg gnlh generic netlink message header
* @arg hdrlen length of family specific header
*/
struct nlattr *genlmsg_attrdata(const struct genlmsghdr *gnlh, int hdrlen)
{
return genlmsg_data(gnlh) + NLMSG_ALIGN(hdrlen);
}
/**
* Get length of attribute data
* @arg gnlh generic netlink message header
* @arg hdrlen length of family specific header
*/
int genlmsg_attrlen(const struct genlmsghdr *gnlh, int hdrlen)
{
return genlmsg_len(gnlh) - NLMSG_ALIGN(hdrlen);
}
/** @} */
/**
* @name Message Building
* @{
*/
/**
* Add generic netlink header to netlink message
* @arg msg netlink message
* @arg pid netlink process id or NL_AUTO_PID
* @arg seq sequence number of message or NL_AUTO_SEQ
* @arg family generic netlink family
* @arg hdrlen length of user specific header
* @arg flags message flags
* @arg cmd generic netlink command
* @arg version protocol version
*
* Returns pointer to user specific header.
*/
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)
{
struct nlmsghdr *nlh;
struct genlmsghdr hdr = {
.cmd = cmd,
.version = version,
};
nlh = nlmsg_put(msg, pid, seq, family, GENL_HDRLEN + hdrlen, flags);
if (nlh == NULL)
return NULL;
memcpy(nlmsg_data(nlh), &hdr, sizeof(hdr));
NL_DBG(2, "msg %p: Added generic netlink header cmd=%d version=%d\n",
msg, cmd, version);
return nlmsg_data(nlh) + GENL_HDRLEN;
}
/** @} */
/** @} */