392 lines
9.7 KiB
C
392 lines
9.7 KiB
C
/*
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* lib/genl/genl.c Generic Netlink
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation version 2.1
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* of the License.
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*
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* Copyright (c) 2003-2012 Thomas Graf <tgraf@suug.ch>
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*/
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/**
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* @defgroup genl Generic Netlink Library (libnl-genl)
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*
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* @{
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*/
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#include <netlink-generic.h>
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#include <netlink/netlink.h>
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#include <netlink/genl/genl.h>
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#include <netlink/utils.h>
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/**
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* @name Generic Netlink Socket
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* @{
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*/
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/**
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* Connect a Generic Netlink socket
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* @arg sk Unconnected Netlink socket
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*
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* This function expects a struct nl_socket object previously allocated via
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* nl_socket_alloc(). It calls nl_connect() to create the local socket file
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* descriptor and binds the socket to the \c NETLINK_GENERIC Netlink protocol.
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*
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* Using this function is equivalent to:
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* @code
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* nl_connect(sk, NETLINK_GENERIC);
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* @endcode
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*
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* @see nl_connect()
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*
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* @return 0 on success or a negative error code.
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*/
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int genl_connect(struct nl_sock *sk)
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{
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return nl_connect(sk, NETLINK_GENERIC);
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}
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/** @} */
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/**
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* @name Sending Data
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* @{
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*/
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/**
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* Send a Generic Netlink message consisting only of a header
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* @arg sk Generic Netlink socket
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* @arg family Numeric family identifier
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* @arg cmd Numeric command identifier
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* @arg version Interface version
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* @arg flags Additional Netlink message flags (optional)
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*
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* This function is a shortcut for sending a Generic Netlink message without
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* any message payload. The message will only consist of the Netlink and
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* Generic Netlink headers. The header is constructed based on the specified
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* parameters and passed on to nl_send_simple() to send it on the specified
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* socket.
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*
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* @par Example:
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* @code
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* #include <netlink/genl/genl.h>
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* #include <linux/genetlink.h>
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*
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* err = genl_send_simple(sk, GENL_ID_CTRL, CTRL_CMD_GETFAMILY, CTRL_VERSION,
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* NLM_F_DUMP);
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* @endcode
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*
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* @see nl_send_simple()
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*
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* @return 0 on success or a negative error code.
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*/
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int genl_send_simple(struct nl_sock *sk, int family, int cmd,
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int version, int flags)
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{
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struct genlmsghdr hdr = {
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.cmd = cmd,
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.version = version,
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};
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return nl_send_simple(sk, family, flags, &hdr, sizeof(hdr));
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}
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/** @} */
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/**
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* @name Message Parsing
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* @{
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*/
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/**
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* Validate Generic Netlink message headers
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* @arg nlh Pointer to Netlink message header
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* @arg hdrlen Length of user header
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*
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* Verifies the integrity of the Netlink and Generic Netlink headers by
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* enforcing the following requirements:
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* - Valid Netlink message header (nlmsg_valid_hdr())
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* - Presence of a complete Generic Netlink header
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* - At least \c hdrlen bytes of payload included after the generic
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* netlink header.
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*
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* @return A positive integer (true) if the headers are valid or
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* 0 (false) if not.
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*/
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int genlmsg_valid_hdr(struct nlmsghdr *nlh, int hdrlen)
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{
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struct genlmsghdr *ghdr;
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if (!nlmsg_valid_hdr(nlh, GENL_HDRLEN))
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return 0;
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ghdr = nlmsg_data(nlh);
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if (genlmsg_len(ghdr) < NLMSG_ALIGN(hdrlen))
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return 0;
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return 1;
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}
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/**
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* Validate Generic Netlink message including attributes
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* @arg nlh Pointer to Netlink message header
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* @arg hdrlen Length of user header
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* @arg maxtype Maximum attribtue id expected
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* @arg policy Attribute validation policy
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*
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* Verifies the validity of the Netlink and Generic Netlink headers using
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* genlmsg_valid_hdr() and calls nla_validate() on the message payload to
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* verify the integrity of eventual attributes.
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*
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* @note You may call genlmsg_parse() directly to perform validation and
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* parsing in a single step.
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*
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* @see genlmsg_valid_hdr()
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* @see nla_validate()
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* @see genlmsg_parse()
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*
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* @return 0 on success or a negative error code.
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*/
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int genlmsg_validate(struct nlmsghdr *nlh, int hdrlen, int maxtype,
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struct nla_policy *policy)
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{
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struct genlmsghdr *ghdr;
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if (!genlmsg_valid_hdr(nlh, hdrlen))
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return -NLE_MSG_TOOSHORT;
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ghdr = nlmsg_data(nlh);
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return nla_validate(genlmsg_attrdata(ghdr, hdrlen),
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genlmsg_attrlen(ghdr, hdrlen), maxtype, policy);
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}
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/**
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* Parse Generic Netlink message including attributes
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* @arg nlh Pointer to Netlink message header
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* @arg hdrlen Length of user header
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* @arg tb Array to store parsed attributes
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* @arg maxtype Maximum attribute id expected
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* @arg policy Attribute validation policy
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*
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* Verifies the validity of the Netlink and Generic Netlink headers using
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* genlmsg_valid_hdr() and calls nla_parse() on the message payload to
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* parse eventual attributes.
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*
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* @par Example:
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* @code
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* struct nlattr *attrs[MY_TYPE_MAX+1];
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*
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* if ((err = genlsmg_parse(nlmsg_nlh(msg), sizeof(struct my_hdr), attrs,
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* MY_TYPE_MAX, attr_policy)) < 0)
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* // ERROR
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* @endcode
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*
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* @see genlmsg_valid_hdr()
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* @see genlmsg_validate()
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* @see nla_parse()
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*
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* @return 0 on success or a negative error code.
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*/
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int genlmsg_parse(struct nlmsghdr *nlh, int hdrlen, struct nlattr *tb[],
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int maxtype, struct nla_policy *policy)
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{
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struct genlmsghdr *ghdr;
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if (!genlmsg_valid_hdr(nlh, hdrlen))
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return -NLE_MSG_TOOSHORT;
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ghdr = nlmsg_data(nlh);
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return nla_parse(tb, maxtype, genlmsg_attrdata(ghdr, hdrlen),
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genlmsg_attrlen(ghdr, hdrlen), policy);
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}
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/**
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* Return pointer to Generic Netlink header
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* @arg nlh Netlink message header
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*
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* @return Pointer to Generic Netlink message header
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*/
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struct genlmsghdr *genlmsg_hdr(struct nlmsghdr *nlh)
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{
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return nlmsg_data(nlh);
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}
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/**
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* Return length of message payload including user header
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* @arg gnlh Generic Netlink message header
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*
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* @see genlmsg_data()
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*
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* @return Length of user payload including an eventual user header in
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* number of bytes.
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*/
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int genlmsg_len(const struct genlmsghdr *gnlh)
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{
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const struct nlmsghdr *nlh;
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nlh = (const struct nlmsghdr *)((const unsigned char *) gnlh - NLMSG_HDRLEN);
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return (nlh->nlmsg_len - GENL_HDRLEN - NLMSG_HDRLEN);
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}
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/**
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* Return pointer to user header
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* @arg gnlh Generic Netlink message header
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*
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* Calculates the pointer to the user header based on the pointer to
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* the Generic Netlink message header.
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*
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* @return Pointer to the user header
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*/
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void *genlmsg_user_hdr(const struct genlmsghdr *gnlh)
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{
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return genlmsg_data(gnlh);
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}
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/**
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* Return pointer to user data
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* @arg gnlh Generic netlink message header
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* @arg hdrlen Length of user header
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*
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* Calculates the pointer to the user data based on the pointer to
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* the Generic Netlink message header.
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*
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* @see genlmsg_user_datalen()
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*
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* @return Pointer to the user data
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*/
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void *genlmsg_user_data(const struct genlmsghdr *gnlh, const int hdrlen)
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{
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return genlmsg_user_hdr(gnlh) + NLMSG_ALIGN(hdrlen);
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}
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/**
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* Return length of user data
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* @arg gnlh Generic Netlink message header
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* @arg hdrlen Length of user header
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*
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* @see genlmsg_user_data()
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*
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* @return Length of user data in bytes
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*/
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int genlmsg_user_datalen(const struct genlmsghdr *gnlh, const int hdrlen)
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{
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return genlmsg_len(gnlh) - NLMSG_ALIGN(hdrlen);
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}
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/**
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* Return pointer to message attributes
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* @arg gnlh Generic Netlink message header
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* @arg hdrlen Length of user header
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*
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* @see genlmsg_attrlen()
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*
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* @return Pointer to the start of the message's attributes section.
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*/
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struct nlattr *genlmsg_attrdata(const struct genlmsghdr *gnlh, int hdrlen)
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{
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return genlmsg_user_data(gnlh, hdrlen);
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}
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/**
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* Return length of message attributes
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* @arg gnlh Generic Netlink message header
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* @arg hdrlen Length of user header
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*
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* @see genlmsg_attrdata()
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*
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* @return Length of the message section containing attributes in number
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* of bytes.
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*/
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int genlmsg_attrlen(const struct genlmsghdr *gnlh, int hdrlen)
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{
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return genlmsg_len(gnlh) - NLMSG_ALIGN(hdrlen);
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}
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/** @} */
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/**
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* @name Message Construction
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* @{
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*/
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/**
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* Add Generic Netlink headers to Netlink message
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* @arg msg Netlink message object
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* @arg port Netlink port or NL_AUTO_PORT
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* @arg seq Sequence number of message or NL_AUTO_SEQ
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* @arg family Numeric family identifier
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* @arg hdrlen Length of user header
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* @arg flags Additional Netlink message flags (optional)
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* @arg cmd Numeric command identifier
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* @arg version Interface version
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*
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* Calls nlmsg_put() on the specified message object to reserve space for
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* the Netlink header, the Generic Netlink header, and a user header of
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* specified length. Fills out the header fields with the specified
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* parameters.
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*
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* @par Example:
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* @code
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* struct nl_msg *msg;
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* struct my_hdr *user_hdr;
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*
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* if (!(msg = nlmsg_alloc()))
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* // ERROR
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*
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* user_hdr = genlmsg_put(msg, NL_AUTO_PORT, NL_AUTO_SEQ, family_id,
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* sizeof(struct my_hdr), 0, MY_CMD_FOO, 0);
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* if (!user_hdr)
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* // ERROR
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* @endcode
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*
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* @see nlmsg_put()
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*
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* Returns Pointer to user header or NULL if an error occurred.
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*/
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void *genlmsg_put(struct nl_msg *msg, uint32_t port, uint32_t seq, int family,
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int hdrlen, int flags, uint8_t cmd, uint8_t version)
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{
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struct nlmsghdr *nlh;
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struct genlmsghdr hdr = {
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.cmd = cmd,
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.version = version,
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};
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nlh = nlmsg_put(msg, port, seq, family, GENL_HDRLEN + hdrlen, flags);
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if (nlh == NULL)
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return NULL;
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memcpy(nlmsg_data(nlh), &hdr, sizeof(hdr));
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NL_DBG(2, "msg %p: Added generic netlink header cmd=%d version=%d\n",
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msg, cmd, version);
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return nlmsg_data(nlh) + GENL_HDRLEN;
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}
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/** @} */
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/**
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* @name Deprecated
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* @{
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*/
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/**
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* Return pointer to message payload
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* @arg gnlh Generic Netlink message header
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*
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* @deprecated This function has been deprecated due to inability to specify
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* the length of the user header. Use genlmsg_user_hdr()
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* respectively genlmsg_user_data().
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*
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* @return Pointer to payload section
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*/
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void *genlmsg_data(const struct genlmsghdr *gnlh)
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{
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return ((unsigned char *) gnlh + GENL_HDRLEN);
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}
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/** @} */
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/** @} */
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