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562 lines
15 KiB
C
562 lines
15 KiB
C
/*
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* lib/msg.c Netlink Messages Interface
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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) 2003-2008 Thomas Graf <tgraf@suug.ch>
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*/
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/**
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* @ingroup core
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* @defgroup msg Messages
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* Netlink Message Construction/Parsing Interface
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*
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* The following information is partly extracted from RFC3549
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* (ftp://ftp.rfc-editor.org/in-notes/rfc3549.txt)
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*
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* @par Message Format
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* Netlink messages consist of a byte stream with one or multiple
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* Netlink headers and an associated payload. If the payload is too big
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* to fit into a single message it, can be split over multiple Netlink
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* messages, collectively called a multipart message. For multipart
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* messages, the first and all following headers have the \c NLM_F_MULTI
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* Netlink header flag set, except for the last header which has the
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* Netlink header type \c NLMSG_DONE.
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*
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* @par
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* The Netlink message header (\link nlmsghdr struct nlmsghdr\endlink) is shown below.
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* @code
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* 0 1 2 3
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* 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
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | Length |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | Type | Flags |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | Sequence Number |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | Process ID (PID) |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* @endcode
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*
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* @par
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* The netlink message header and payload must be aligned properly:
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* @code
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* <------- NLMSG_ALIGN(hlen) ------> <---- NLMSG_ALIGN(len) --->
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* +----------------------------+- - -+- - - - - - - - - - -+- - -+
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* | Header | Pad | Payload | Pad |
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* | struct nlmsghdr | | | |
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* +----------------------------+- - -+- - - - - - - - - - -+- - -+
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* @endcode
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* @par
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* Message Format:
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* @code
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* <--- nlmsg_total_size(payload) --->
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* <-- nlmsg_msg_size(payload) ->
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* +----------+- - -+-------------+- - -+-------- - -
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* | nlmsghdr | Pad | Payload | Pad | nlmsghdr
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* +----------+- - -+-------------+- - -+-------- - -
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* nlmsg_data(nlh)---^ ^
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* nlmsg_next(nlh)-----------------------+
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* @endcode
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* @par
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* The payload may consist of arbitary data but may have strict
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* alignment and formatting rules depening on the specific netlink
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* families.
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* @par
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* @code
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* <---------------------- nlmsg_len(nlh) --------------------->
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* <------ hdrlen ------> <- nlmsg_attrlen(nlh, hdrlen) ->
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* +----------------------+- - -+--------------------------------+
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* | Family Header | Pad | Attributes |
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* +----------------------+- - -+--------------------------------+
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* nlmsg_attrdata(nlh, hdrlen)---^
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* @endcode
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* @par The ACK Netlink Message
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* This message is actually used to denote both an ACK and a NACK.
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* Typically, the direction is from FEC to CPC (in response to an ACK
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* request message). However, the CPC should be able to send ACKs back
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* to FEC when requested.
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* @code
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* 0 1 2 3
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* 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
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | Netlink message header |
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* | type = NLMSG_ERROR |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | Error code |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | OLD Netlink message header |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* @endcode
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*
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* @par Example
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* @code
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* // Various methods exist to create/allocate a new netlink
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* // message.
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* //
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* // nlmsg_alloc() will allocate an empty netlink message with
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* // a maximum payload size which defaults to the page size of
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* // the system. This default size can be modified using the
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* // function nlmsg_set_default_size().
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* struct nl_msg *msg = nlmsg_alloc();
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*
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* // Very often, the message type and message flags are known
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* // at allocation time while the other fields are auto generated:
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* struct nl_msg *msg = nlmsg_alloc_simple(MY_TYPE, MY_FLAGS);
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*
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* // Alternatively an existing netlink message header can be used
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* // to inherit the header values:
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* struct nlmsghdr hdr = {
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* .nlmsg_type = MY_TYPE,
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* .nlmsg_flags = MY_FLAGS,
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* };
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* struct nl_msg *msg = nlmsg_inherit(&hdr);
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*
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* // Last but not least, netlink messages received from netlink sockets
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* // can be converted into nl_msg objects using nlmsg_convert(). This
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* // will create a message with a maximum payload size which equals the
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* // length of the existing netlink message, therefore no more data can
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* // be appened without calling nlmsg_expand() first.
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* struct nl_msg *msg = nlmsg_convert(nlh_from_nl_sock);
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*
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* // Payload may be added to the message via nlmsg_append(). The fourth
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* // parameter specifies the number of alignment bytes the data should
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* // be padding with at the end. Common values are 0 to disable it or
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* // NLMSG_ALIGNTO to ensure proper netlink message padding.
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* nlmsg_append(msg, &mydata, sizeof(mydata), 0);
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*
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* // Sometimes it may be necessary to reserve room for data but defer
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* // the actual copying to a later point, nlmsg_reserve() can be used
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* // for this purpose:
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* void *data = nlmsg_reserve(msg, sizeof(mydata), NLMSG_ALIGNTO);
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*
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* // Attributes may be added using the attributes interface.
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*
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* // After successful use of the message, the memory must be freed
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* // using nlmsg_free()
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* nlmsg_free(msg);
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* @endcode
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*
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* @par 4) Parsing messages
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* @code
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* int n;
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* unsigned char *buf;
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* struct nlmsghdr *hdr;
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*
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* n = nl_recv(handle, NULL, &buf);
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*
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* hdr = (struct nlmsghdr *) buf;
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* while (nlmsg_ok(hdr, n)) {
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* // Process message here...
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* hdr = nlmsg_next(hdr, &n);
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* }
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* @endcode
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* @{
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*/
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#include <netlink-local.h>
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#include <netlink/netlink.h>
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#include <netlink/utils.h>
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#include <netlink/cache.h>
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#include <netlink/attr.h>
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#include <netlink/msg.h>
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#include <linux/socket.h>
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static size_t default_msg_size = 4096;
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/**
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* @name Attribute Access
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* @{
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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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* check if the netlink message fits into the remaining bytes
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* @arg nlh netlink message header
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* @arg remaining number of bytes remaining in message stream
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*/
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int nlmsg_ok(const struct nlmsghdr *nlh, int remaining)
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{
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return (remaining >= sizeof(struct nlmsghdr) &&
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nlh->nlmsg_len >= sizeof(struct nlmsghdr) &&
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nlh->nlmsg_len <= remaining);
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}
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/**
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* next netlink message in message stream
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* @arg nlh netlink message header
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* @arg remaining number of bytes remaining in message stream
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*
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* @returns the next netlink message in the message stream and
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* decrements remaining by the size of the current message.
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*/
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struct nlmsghdr *nlmsg_next(struct nlmsghdr *nlh, int *remaining)
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{
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int totlen = NLMSG_ALIGN(nlh->nlmsg_len);
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*remaining -= totlen;
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return (struct nlmsghdr *) ((unsigned char *) nlh + totlen);
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}
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/**
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* parse attributes of a netlink message
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* @arg nlh netlink message header
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* @arg hdrlen length of family specific header
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* @arg tb destination array with maxtype+1 elements
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* @arg maxtype maximum attribute type to be expected
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* @arg policy validation policy
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*
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* See nla_parse()
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*/
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int nlmsg_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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if (!nlmsg_valid_hdr(nlh, hdrlen))
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return -NLE_MSG_TOOSHORT;
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return nla_parse(tb, maxtype, nlmsg_attrdata(nlh, hdrlen),
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nlmsg_attrlen(nlh, hdrlen), policy);
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}
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/**
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* nlmsg_validate - validate a netlink message including attributes
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* @arg nlh netlinket message header
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* @arg hdrlen length of familiy specific header
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* @arg maxtype maximum attribute type to be expected
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* @arg policy validation policy
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*/
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int nlmsg_validate(struct nlmsghdr *nlh, int hdrlen, int maxtype,
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struct nla_policy *policy)
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{
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if (!nlmsg_valid_hdr(nlh, hdrlen))
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return -NLE_MSG_TOOSHORT;
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return nla_validate(nlmsg_attrdata(nlh, hdrlen),
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nlmsg_attrlen(nlh, hdrlen), maxtype, policy);
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}
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/** @} */
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/**
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* @name Message Building/Access
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* @{
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*/
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static struct nl_msg *__nlmsg_alloc(size_t len)
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{
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struct nl_msg *nm;
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nm = calloc(1, sizeof(*nm));
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if (!nm)
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goto errout;
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nm->nm_refcnt = 1;
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nm->nm_nlh = malloc(len);
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if (!nm->nm_nlh)
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goto errout;
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memset(nm->nm_nlh, 0, sizeof(struct nlmsghdr));
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nm->nm_protocol = -1;
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nm->nm_size = len;
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nm->nm_nlh->nlmsg_len = nlmsg_total_size(0);
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NL_DBG(2, "msg %p: Allocated new message, maxlen=%zu\n", nm, len);
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return nm;
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errout:
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free(nm);
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return NULL;
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}
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/**
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* Allocate a new netlink message with the default maximum payload size.
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*
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* Allocates a new netlink message without any further payload. The
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* maximum payload size defaults to PAGESIZE or as otherwise specified
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* with nlmsg_set_default_size().
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*
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* @return Newly allocated netlink message or NULL.
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*/
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struct nl_msg *nlmsg_alloc(void)
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{
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return __nlmsg_alloc(default_msg_size);
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}
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/**
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* Allocate a new netlink message with maximum payload size specified.
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*/
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struct nl_msg *nlmsg_alloc_size(size_t max)
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{
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return __nlmsg_alloc(max);
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}
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/**
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* Allocate a new netlink message and inherit netlink message header
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* @arg hdr Netlink message header template
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*
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* Allocates a new netlink message and inherits the original message
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* header. If \a hdr is not NULL it will be used as a template for
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* the netlink message header, otherwise the header is left blank.
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*
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* @return Newly allocated netlink message or NULL
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*/
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struct nl_msg *nlmsg_inherit(struct nlmsghdr *hdr)
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{
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struct nl_msg *nm;
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nm = nlmsg_alloc();
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if (nm && hdr) {
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struct nlmsghdr *new = nm->nm_nlh;
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new->nlmsg_type = hdr->nlmsg_type;
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new->nlmsg_flags = hdr->nlmsg_flags;
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new->nlmsg_seq = hdr->nlmsg_seq;
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new->nlmsg_pid = hdr->nlmsg_pid;
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}
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return nm;
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}
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/**
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* Allocate a new netlink message
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* @arg nlmsgtype Netlink message type
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* @arg flags Message flags.
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*
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* @return Newly allocated netlink message or NULL.
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*/
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struct nl_msg *nlmsg_alloc_simple(int nlmsgtype, int flags)
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{
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struct nl_msg *msg;
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struct nlmsghdr nlh = {
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.nlmsg_type = nlmsgtype,
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.nlmsg_flags = flags,
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};
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msg = nlmsg_inherit(&nlh);
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if (msg)
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NL_DBG(2, "msg %p: Allocated new simple message\n", msg);
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return msg;
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}
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/**
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* Set the default maximum message payload size for allocated messages
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* @arg max Size of payload in bytes.
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*/
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void nlmsg_set_default_size(size_t max)
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{
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if (max < nlmsg_total_size(0))
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max = nlmsg_total_size(0);
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default_msg_size = max;
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}
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/**
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* Convert a netlink message received from a netlink socket to a nl_msg
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* @arg hdr Netlink message received from netlink socket.
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*
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* Allocates a new netlink message and copies all of the data pointed to
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* by \a hdr into the new message object.
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*
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* @return Newly allocated netlink message or NULL.
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*/
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struct nl_msg *nlmsg_convert(struct nlmsghdr *hdr)
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{
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struct nl_msg *nm;
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nm = __nlmsg_alloc(NLMSG_ALIGN(hdr->nlmsg_len));
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if (!nm)
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goto errout;
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memcpy(nm->nm_nlh, hdr, hdr->nlmsg_len);
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return nm;
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errout:
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nlmsg_free(nm);
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return NULL;
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}
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/**
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* Reserve room for additional data in a netlink message
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* @arg n netlink message
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* @arg len length of additional data to reserve room for
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* @arg pad number of bytes to align data to
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*
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* Reserves room for additional data at the tail of the an
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* existing netlink message. Eventual padding required will
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* be zeroed out.
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*
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* @return Pointer to start of additional data tailroom or NULL.
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*/
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void *nlmsg_reserve(struct nl_msg *n, size_t len, int pad)
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{
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void *buf = n->nm_nlh;
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size_t nlmsg_len = n->nm_nlh->nlmsg_len;
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size_t tlen;
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tlen = pad ? ((len + (pad - 1)) & ~(pad - 1)) : len;
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if ((tlen + nlmsg_len) > n->nm_size)
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return NULL;
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buf += nlmsg_len;
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n->nm_nlh->nlmsg_len += tlen;
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if (tlen > len)
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memset(buf + len, 0, tlen - len);
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NL_DBG(2, "msg %p: Reserved %zu bytes, pad=%d, nlmsg_len=%d\n",
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n, len, pad, n->nm_nlh->nlmsg_len);
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return buf;
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}
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/**
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* Append data to tail of a netlink message
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* @arg n netlink message
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* @arg data data to add
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* @arg len length of data
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* @arg pad Number of bytes to align data to.
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*
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* Extends the netlink message as needed and appends the data of given
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* length to the message.
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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 nlmsg_append(struct nl_msg *n, void *data, size_t len, int pad)
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{
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void *tmp;
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tmp = nlmsg_reserve(n, len, pad);
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if (tmp == NULL)
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return -NLE_NOMEM;
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memcpy(tmp, data, len);
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NL_DBG(2, "msg %p: Appended %zu bytes with padding %d\n", n, len, pad);
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return 0;
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}
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/**
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* Add a netlink message header to a netlink message
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* @arg n netlink message
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* @arg pid netlink process id or NL_AUTO_PID
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* @arg seq sequence number of message or NL_AUTO_SEQ
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* @arg type message type
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* @arg payload length of message payload
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* @arg flags message flags
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*
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* Adds or overwrites the netlink message header in an existing message
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* object. If \a payload is greater-than zero additional room will be
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* reserved, f.e. for family specific headers. It can be accesed via
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* nlmsg_data().
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*
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* @return A pointer to the netlink message header or NULL.
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*/
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struct nlmsghdr *nlmsg_put(struct nl_msg *n, uint32_t pid, uint32_t seq,
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int type, int payload, int flags)
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{
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struct nlmsghdr *nlh;
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if (n->nm_nlh->nlmsg_len < NLMSG_HDRLEN)
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BUG();
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nlh = (struct nlmsghdr *) n->nm_nlh;
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nlh->nlmsg_type = type;
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nlh->nlmsg_flags = flags;
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nlh->nlmsg_pid = pid;
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nlh->nlmsg_seq = seq;
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NL_DBG(2, "msg %p: Added netlink header type=%d, flags=%d, pid=%d, "
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"seq=%d\n", n, type, flags, pid, seq);
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if (payload > 0 &&
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nlmsg_reserve(n, payload, NLMSG_ALIGNTO) == NULL)
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return NULL;
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return nlh;
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}
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/**
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* Release a reference from an netlink message
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* @arg msg message to release reference from
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*
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* Frees memory after the last reference has been released.
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*/
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void nlmsg_free(struct nl_msg *msg)
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{
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if (!msg)
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return;
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msg->nm_refcnt--;
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NL_DBG(4, "Returned message reference %p, %d remaining\n",
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msg, msg->nm_refcnt);
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|
|
if (msg->nm_refcnt < 0)
|
|
BUG();
|
|
|
|
if (msg->nm_refcnt <= 0) {
|
|
free(msg->nm_nlh);
|
|
free(msg);
|
|
NL_DBG(2, "msg %p: Freed\n", msg);
|
|
}
|
|
}
|
|
|
|
/** @} */
|
|
|
|
/**
|
|
* @name Direct Parsing
|
|
* @{
|
|
*/
|
|
|
|
/** @cond SKIP */
|
|
struct dp_xdata {
|
|
void (*cb)(struct nl_object *, void *);
|
|
void *arg;
|
|
};
|
|
/** @endcond */
|
|
|
|
static int parse_cb(struct nl_object *obj, struct nl_parser_param *p)
|
|
{
|
|
struct dp_xdata *x = p->pp_arg;
|
|
|
|
x->cb(obj, x->arg);
|
|
return 0;
|
|
}
|
|
|
|
int nl_msg_parse(struct nl_msg *msg, void (*cb)(struct nl_object *, void *),
|
|
void *arg)
|
|
{
|
|
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 -NLE_MSGTYPE_NOSUPPORT;
|
|
p.pp_arg = &x;
|
|
|
|
return nl_cache_parse(ops, NULL, nlmsg_hdr(msg), &p);
|
|
}
|
|
|
|
/** @} */
|