/*
* 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) 2003-2012 Thomas Graf <tgraf@suug.ch>
*/
/**
* @defgroup genl Generic Netlink Library (libnl-genl)
*
* @{
*/
#include <netlink-private/genl.h>
#include <netlink/netlink.h>
#include <netlink/genl/genl.h>
#include <netlink/utils.h>
/**
* @name Generic Netlink Socket
* @{
*/
/**
* Connect a Generic Netlink socket
* @arg sk Unconnected Netlink socket
*
* This function expects a struct nl_socket object previously allocated via
* nl_socket_alloc(). It calls nl_connect() to create the local socket file
* descriptor and binds the socket to the \c NETLINK_GENERIC Netlink protocol.
*
* Using this function is equivalent to:
* @code
* nl_connect(sk, NETLINK_GENERIC);
* @endcode
*
* @see nl_connect()
*
* @return 0 on success or a negative error code.
*/
int genl_connect(struct nl_sock *sk)
{
return nl_connect(sk, NETLINK_GENERIC);
}
/** @} */
/**
* @name Sending Data
* @{
*/
/**
* Send a Generic Netlink message consisting only of a header
* @arg sk Generic Netlink socket
* @arg family Numeric family identifier
* @arg cmd Numeric command identifier
* @arg version Interface version
* @arg flags Additional Netlink message flags (optional)
*
* This function is a shortcut for sending a Generic Netlink message without
* any message payload. The message will only consist of the Netlink and
* Generic Netlink headers. The header is constructed based on the specified
* parameters and passed on to nl_send_simple() to send it on the specified
* socket.
*
* @par Example:
* @code
* #include <netlink/genl/genl.h>
* #include <linux/genetlink.h>
*
* err = genl_send_simple(sk, GENL_ID_CTRL, CTRL_CMD_GETFAMILY, CTRL_VERSION,
* NLM_F_DUMP);
* @endcode
*
* @see 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
* @{
*/
/**
* Validate Generic Netlink message headers
* @arg nlh Pointer to Netlink message header
* @arg hdrlen Length of user header
*
* Verifies the integrity of the Netlink and Generic Netlink headers by
* enforcing the following requirements:
* - Valid Netlink message header (nlmsg_valid_hdr())
* - Presence of a complete Generic Netlink header
* - At least \c hdrlen bytes of payload included after the generic
* netlink header.
*
* @return A positive integer (true) if the headers are valid or
* 0 (false) if not.
*/
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;
}
/**
* Validate Generic Netlink message including attributes
* @arg nlh Pointer to Netlink message header
* @arg hdrlen Length of user header
* @arg maxtype Maximum attribtue id expected
* @arg policy Attribute validation policy
*
* Verifies the validity of the Netlink and Generic Netlink headers using
* genlmsg_valid_hdr() and calls nla_validate() on the message payload to
* verify the integrity of eventual attributes.
*
* @note You may call genlmsg_parse() directly to perform validation and
* parsing in a single step.
*
* @see genlmsg_valid_hdr()
* @see nla_validate()
* @see genlmsg_parse()
*
* @return 0 on success or a negative error code.
*/
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);
}
/**
* Parse Generic Netlink message including attributes
* @arg nlh Pointer to Netlink message header
* @arg hdrlen Length of user header
* @arg tb Array to store parsed attributes
* @arg maxtype Maximum attribute id expected
* @arg policy Attribute validation policy
*
* Verifies the validity of the Netlink and Generic Netlink headers using
* genlmsg_valid_hdr() and calls nla_parse() on the message payload to
* parse eventual attributes.
*
* @par Example:
* @code
* struct nlattr *attrs[MY_TYPE_MAX+1];
*
* if ((err = genlsmg_parse(nlmsg_nlh(msg), sizeof(struct my_hdr), attrs,
* MY_TYPE_MAX, attr_policy)) < 0)
* // ERROR
* @endcode
*
* @see genlmsg_valid_hdr()
* @see genlmsg_validate()
* @see nla_parse()
*
* @return 0 on success or a negative error code.
*/
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);
}
/**
* Return pointer to Generic Netlink header
* @arg nlh Netlink message header
*
* @return Pointer to Generic Netlink message header
*/
struct genlmsghdr *genlmsg_hdr(struct nlmsghdr *nlh)
{
return nlmsg_data(nlh);
}
/**
* Return length of message payload including user header
* @arg gnlh Generic Netlink message header
*
* @see genlmsg_data()
*
* @return Length of user payload including an eventual user header in
* number of bytes.
*/
int genlmsg_len(const struct genlmsghdr *gnlh)
{
const struct nlmsghdr *nlh;
nlh = (const struct nlmsghdr *)((const unsigned char *) gnlh - NLMSG_HDRLEN);
return (nlh->nlmsg_len - GENL_HDRLEN - NLMSG_HDRLEN);
}
/**
* Return pointer to user header
* @arg gnlh Generic Netlink message header
*
* Calculates the pointer to the user header based on the pointer to
* the Generic Netlink message header.
*
* @return Pointer to the user header
*/
void *genlmsg_user_hdr(const struct genlmsghdr *gnlh)
{
return genlmsg_data(gnlh);
}
/**
* Return pointer to user data
* @arg gnlh Generic netlink message header
* @arg hdrlen Length of user header
*
* Calculates the pointer to the user data based on the pointer to
* the Generic Netlink message header.
*
* @see genlmsg_user_datalen()
*
* @return Pointer to the user data
*/
void *genlmsg_user_data(const struct genlmsghdr *gnlh, const int hdrlen)
{
return genlmsg_user_hdr(gnlh) + NLMSG_ALIGN(hdrlen);
}
/**
* Return length of user data
* @arg gnlh Generic Netlink message header
* @arg hdrlen Length of user header
*
* @see genlmsg_user_data()
*
* @return Length of user data in bytes
*/
int genlmsg_user_datalen(const struct genlmsghdr *gnlh, const int hdrlen)
{
return genlmsg_len(gnlh) - NLMSG_ALIGN(hdrlen);
}
/**
* Return pointer to message attributes
* @arg gnlh Generic Netlink message header
* @arg hdrlen Length of user header
*
* @see genlmsg_attrlen()
*
* @return Pointer to the start of the message's attributes section.
*/
struct nlattr *genlmsg_attrdata(const struct genlmsghdr *gnlh, int hdrlen)
{
return genlmsg_user_data(gnlh, hdrlen);
}
/**
* Return length of message attributes
* @arg gnlh Generic Netlink message header
* @arg hdrlen Length of user header
*
* @see genlmsg_attrdata()
*
* @return Length of the message section containing attributes in number
* of bytes.
*/
int genlmsg_attrlen(const struct genlmsghdr *gnlh, int hdrlen)
{
return genlmsg_len(gnlh) - NLMSG_ALIGN(hdrlen);
}
/** @} */
/**
* @name Message Construction
* @{
*/
/**
* Add Generic Netlink headers to Netlink message
* @arg msg Netlink message object
* @arg port Netlink port or NL_AUTO_PORT
* @arg seq Sequence number of message or NL_AUTO_SEQ
* @arg family Numeric family identifier
* @arg hdrlen Length of user header
* @arg flags Additional Netlink message flags (optional)
* @arg cmd Numeric command identifier
* @arg version Interface version
*
* Calls nlmsg_put() on the specified message object to reserve space for
* the Netlink header, the Generic Netlink header, and a user header of
* specified length. Fills out the header fields with the specified
* parameters.
*
* @par Example:
* @code
* struct nl_msg *msg;
* struct my_hdr *user_hdr;
*
* if (!(msg = nlmsg_alloc()))
* // ERROR
*
* user_hdr = genlmsg_put(msg, NL_AUTO_PORT, NL_AUTO_SEQ, family_id,
* sizeof(struct my_hdr), 0, MY_CMD_FOO, 0);
* if (!user_hdr)
* // ERROR
* @endcode
*
* @see nlmsg_put()
*
* Returns Pointer to user header or NULL if an error occurred.
*/
void *genlmsg_put(struct nl_msg *msg, uint32_t port, 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, port, 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;
}
/** @} */
/**
* @name Deprecated
* @{
*/
/**
* Return pointer to message payload
* @arg gnlh Generic Netlink message header
*
* @deprecated This function has been deprecated due to inability to specify
* the length of the user header. Use genlmsg_user_hdr()
* respectively genlmsg_user_data().
*
* @return Pointer to payload section
*/
void *genlmsg_data(const struct genlmsghdr *gnlh)
{
return ((unsigned char *) gnlh + GENL_HDRLEN);
}
/** @} */
/** @} */