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+/*
+ * lib/msg.c Netlink Messages Interface
+ *
+ * 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>
+ */
+
+/**
+ * @ingroup core
+ * @defgroup msg Messages
+ * Netlink Message Construction/Parsing Interface
+ *
+ * The following information is partly extracted from RFC3549
+ * (ftp://ftp.rfc-editor.org/in-notes/rfc3549.txt)
+ *
+ * @par Message Format
+ * Netlink messages consist of a byte stream with one or multiple
+ * Netlink headers and an associated payload. If the payload is too big
+ * to fit into a single message it, can be split over multiple Netlink
+ * messages, collectively called a multipart message. For multipart
+ * messages, the first and all following headers have the \c NLM_F_MULTI
+ * Netlink header flag set, except for the last header which has the
+ * Netlink header type \c NLMSG_DONE.
+ *
+ * @par
+ * The Netlink message header (\link nlmsghdr struct nlmsghdr\endlink) is shown below.
+ * @code
+ * 0 1 2 3
+ * 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
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Length |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Type | Flags |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Sequence Number |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Process ID (PID) |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * @endcode
+ *
+ * @par
+ * The netlink message header and payload must be aligned properly:
+ * @code
+ * <------- NLMSG_ALIGN(hlen) ------> <---- NLMSG_ALIGN(len) --->
+ * +----------------------------+- - -+- - - - - - - - - - -+- - -+
+ * | Header | Pad | Payload | Pad |
+ * | struct nlmsghdr | | | |
+ * +----------------------------+- - -+- - - - - - - - - - -+- - -+
+ * @endcode
+ * @par
+ * Message Format:
+ * @code
+ * <--- nlmsg_total_size(payload) --->
+ * <-- nlmsg_msg_size(payload) ->
+ * +----------+- - -+-------------+- - -+-------- - -
+ * | nlmsghdr | Pad | Payload | Pad | nlmsghdr
+ * +----------+- - -+-------------+- - -+-------- - -
+ * nlmsg_data(nlh)---^ ^
+ * nlmsg_next(nlh)-----------------------+
+ * @endcode
+ * @par
+ * The payload may consist of arbitary data but may have strict
+ * alignment and formatting rules depening on the specific netlink
+ * families.
+ * @par
+ * @code
+ * <---------------------- nlmsg_len(nlh) --------------------->
+ * <------ hdrlen ------> <- nlmsg_attrlen(nlh, hdrlen) ->
+ * +----------------------+- - -+--------------------------------+
+ * | Family Header | Pad | Attributes |
+ * +----------------------+- - -+--------------------------------+
+ * nlmsg_attrdata(nlh, hdrlen)---^
+ * @endcode
+ * @par The ACK Netlink Message
+ * This message is actually used to denote both an ACK and a NACK.
+ * Typically, the direction is from FEC to CPC (in response to an ACK
+ * request message). However, the CPC should be able to send ACKs back
+ * to FEC when requested.
+ * @code
+ * 0 1 2 3
+ * 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
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Netlink message header |
+ * | type = NLMSG_ERROR |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Error code |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | OLD Netlink message header |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * @endcode
+ *
+ * @par Example
+ * @code
+ * // Various methods exist to create/allocate a new netlink
+ * // message.
+ * //
+ * // nlmsg_alloc() will allocate an empty netlink message with
+ * // a maximum payload size which defaults to the page size of
+ * // the system. This default size can be modified using the
+ * // function nlmsg_set_default_size().
+ * struct nl_msg *msg = nlmsg_alloc();
+ *
+ * // Very often, the message type and message flags are known
+ * // at allocation time while the other fields are auto generated:
+ * struct nl_msg *msg = nlmsg_alloc_simple(MY_TYPE, MY_FLAGS);
+ *
+ * // Alternatively an existing netlink message header can be used
+ * // to inherit the header values:
+ * struct nlmsghdr hdr = {
+ * .nlmsg_type = MY_TYPE,
+ * .nlmsg_flags = MY_FLAGS,
+ * };
+ * struct nl_msg *msg = nlmsg_inherit(&hdr);
+ *
+ * // Last but not least, netlink messages received from netlink sockets
+ * // can be converted into nl_msg objects using nlmsg_convert(). This
+ * // will create a message with a maximum payload size which equals the
+ * // length of the existing netlink message, therefore no more data can
+ * // be appened without calling nlmsg_expand() first.
+ * struct nl_msg *msg = nlmsg_convert(nlh_from_nl_sock);
+ *
+ * // Payload may be added to the message via nlmsg_append(). The fourth
+ * // parameter specifies the number of alignment bytes the data should
+ * // be padding with at the end. Common values are 0 to disable it or
+ * // NLMSG_ALIGNTO to ensure proper netlink message padding.
+ * nlmsg_append(msg, &mydata, sizeof(mydata), 0);
+ *
+ * // Sometimes it may be necessary to reserve room for data but defer
+ * // the actual copying to a later point, nlmsg_reserve() can be used
+ * // for this purpose:
+ * void *data = nlmsg_reserve(msg, sizeof(mydata), NLMSG_ALIGNTO);
+ *
+ * // Attributes may be added using the attributes interface.
+ *
+ * // After successful use of the message, the memory must be freed
+ * // using nlmsg_free()
+ * nlmsg_free(msg);
+ * @endcode
+ *
+ * @par 4) Parsing messages
+ * @code
+ * int n;
+ * unsigned char *buf;
+ * struct nlmsghdr *hdr;
+ *
+ * n = nl_recv(handle, NULL, &buf);
+ *
+ * hdr = (struct nlmsghdr *) buf;
+ * while (nlmsg_ok(hdr, n)) {
+ * // Process message here...
+ * hdr = nlmsg_next(hdr, &n);
+ * }
+ * @endcode
+ * @{
+ */
+
+#include <netlink-local.h>
+#include <netlink/netlink.h>
+#include <netlink/utils.h>
+#include <netlink/cache.h>
+#include <netlink/attr.h>
+#include <netlink/msg.h>
+#include <linux/socket.h>
+
+static size_t default_msg_size;
+
+static void __init init_msg_size(void)
+{
+ default_msg_size = getpagesize();
+}
+
+/**
+ * @name Attribute Access
+ * @{
+ */
+
+//** @} */
+
+/**
+ * @name Message Parsing
+ * @{
+ */
+
+/**
+ * check if the netlink message fits into the remaining bytes
+ * @arg nlh netlink message header
+ * @arg remaining number of bytes remaining in message stream
+ */
+int nlmsg_ok(const struct nlmsghdr *nlh, int remaining)
+{
+ return (remaining >= sizeof(struct nlmsghdr) &&
+ nlh->nlmsg_len >= sizeof(struct nlmsghdr) &&
+ nlh->nlmsg_len <= remaining);
+}
+
+/**
+ * next netlink message in message stream
+ * @arg nlh netlink message header
+ * @arg remaining number of bytes remaining in message stream
+ *
+ * @returns the next netlink message in the message stream and
+ * decrements remaining by the size of the current message.
+ */
+struct nlmsghdr *nlmsg_next(struct nlmsghdr *nlh, int *remaining)
+{
+ int totlen = NLMSG_ALIGN(nlh->nlmsg_len);
+
+ *remaining -= totlen;
+
+ return (struct nlmsghdr *) ((unsigned char *) nlh + totlen);
+}
+
+/**
+ * parse attributes of a netlink message
+ * @arg nlh netlink message header
+ * @arg hdrlen length of family specific header
+ * @arg tb destination array with maxtype+1 elements
+ * @arg maxtype maximum attribute type to be expected
+ * @arg policy validation policy
+ *
+ * See nla_parse()
+ */
+int nlmsg_parse(struct nlmsghdr *nlh, int hdrlen, struct nlattr *tb[],
+ int maxtype, struct nla_policy *policy)
+{
+ if (!nlmsg_valid_hdr(nlh, hdrlen))
+ return -NLE_MSG_TOOSHORT;
+
+ return nla_parse(tb, maxtype, nlmsg_attrdata(nlh, hdrlen),
+ nlmsg_attrlen(nlh, hdrlen), policy);
+}
+
+/**
+ * nlmsg_validate - validate a netlink message including attributes
+ * @arg nlh netlinket message header
+ * @arg hdrlen length of familiy specific header
+ * @arg maxtype maximum attribute type to be expected
+ * @arg policy validation policy
+ */
+int nlmsg_validate(struct nlmsghdr *nlh, int hdrlen, int maxtype,
+ struct nla_policy *policy)
+{
+ if (!nlmsg_valid_hdr(nlh, hdrlen))
+ return -NLE_MSG_TOOSHORT;
+
+ return nla_validate(nlmsg_attrdata(nlh, hdrlen),
+ nlmsg_attrlen(nlh, hdrlen), maxtype, policy);
+}
+
+/** @} */
+
+/**
+ * @name Message Building/Access
+ * @{
+ */
+
+static struct nl_msg *__nlmsg_alloc(size_t len)
+{
+ struct nl_msg *nm;
+
+ nm = calloc(1, sizeof(*nm));
+ if (!nm)
+ goto errout;
+
+ nm->nm_refcnt = 1;
+
+ nm->nm_nlh = malloc(len);
+ if (!nm->nm_nlh)
+ goto errout;
+
+ memset(nm->nm_nlh, 0, sizeof(struct nlmsghdr));
+
+ nm->nm_protocol = -1;
+ nm->nm_size = len;
+ nm->nm_nlh->nlmsg_len = nlmsg_total_size(0);
+
+ NL_DBG(2, "msg %p: Allocated new message, maxlen=%zu\n", nm, len);
+
+ return nm;
+errout:
+ free(nm);
+ return NULL;
+}
+
+/**
+ * Allocate a new netlink message with the default maximum payload size.
+ *
+ * Allocates a new netlink message without any further payload. The
+ * maximum payload size defaults to PAGESIZE or as otherwise specified
+ * with nlmsg_set_default_size().
+ *
+ * @return Newly allocated netlink message or NULL.
+ */
+struct nl_msg *nlmsg_alloc(void)
+{
+ return __nlmsg_alloc(default_msg_size);
+}
+
+/**
+ * Allocate a new netlink message with maximum payload size specified.
+ */
+struct nl_msg *nlmsg_alloc_size(size_t max)
+{
+ return __nlmsg_alloc(max);
+}
+
+/**
+ * Allocate a new netlink message and inherit netlink message header
+ * @arg hdr Netlink message header template
+ *
+ * Allocates a new netlink message and inherits the original message
+ * header. If \a hdr is not NULL it will be used as a template for
+ * the netlink message header, otherwise the header is left blank.
+ *
+ * @return Newly allocated netlink message or NULL
+ */
+struct nl_msg *nlmsg_inherit(struct nlmsghdr *hdr)
+{
+ struct nl_msg *nm;
+
+ nm = nlmsg_alloc();
+ if (nm && hdr) {
+ struct nlmsghdr *new = nm->nm_nlh;
+
+ new->nlmsg_type = hdr->nlmsg_type;
+ new->nlmsg_flags = hdr->nlmsg_flags;
+ new->nlmsg_seq = hdr->nlmsg_seq;
+ new->nlmsg_pid = hdr->nlmsg_pid;
+ }
+
+ return nm;
+}
+
+/**
+ * Allocate a new netlink message
+ * @arg nlmsgtype Netlink message type
+ * @arg flags Message flags.
+ *
+ * @return Newly allocated netlink message or NULL.
+ */
+struct nl_msg *nlmsg_alloc_simple(int nlmsgtype, int flags)
+{
+ struct nl_msg *msg;
+ struct nlmsghdr nlh = {
+ .nlmsg_type = nlmsgtype,
+ .nlmsg_flags = flags,
+ };
+
+ msg = nlmsg_inherit(&nlh);
+ if (msg)
+ NL_DBG(2, "msg %p: Allocated new simple message\n", msg);
+
+ return msg;
+}
+
+/**
+ * Set the default maximum message payload size for allocated messages
+ * @arg max Size of payload in bytes.
+ */
+void nlmsg_set_default_size(size_t max)
+{
+ if (max < nlmsg_total_size(0))
+ max = nlmsg_total_size(0);
+
+ default_msg_size = max;
+}
+
+/**
+ * Convert a netlink message received from a netlink socket to a nl_msg
+ * @arg hdr Netlink message received from netlink socket.
+ *
+ * Allocates a new netlink message and copies all of the data pointed to
+ * by \a hdr into the new message object.
+ *
+ * @return Newly allocated netlink message or NULL.
+ */
+struct nl_msg *nlmsg_convert(struct nlmsghdr *hdr)
+{
+ struct nl_msg *nm;
+
+ nm = __nlmsg_alloc(NLMSG_ALIGN(hdr->nlmsg_len));
+ if (!nm)
+ goto errout;
+
+ memcpy(nm->nm_nlh, hdr, hdr->nlmsg_len);
+
+ return nm;
+errout:
+ nlmsg_free(nm);
+ return NULL;
+}
+
+/**
+ * Reserve room for additional data in a netlink message
+ * @arg n netlink message
+ * @arg len length of additional data to reserve room for
+ * @arg pad number of bytes to align data to
+ *
+ * Reserves room for additional data at the tail of the an
+ * existing netlink message. Eventual padding required will
+ * be zeroed out.
+ *
+ * @return Pointer to start of additional data tailroom or NULL.
+ */
+void *nlmsg_reserve(struct nl_msg *n, size_t len, int pad)
+{
+ void *buf = n->nm_nlh;
+ size_t nlmsg_len = n->nm_nlh->nlmsg_len;
+ size_t tlen;
+
+ tlen = pad ? ((len + (pad - 1)) & ~(pad - 1)) : len;
+
+ if ((tlen + nlmsg_len) > n->nm_size)
+ return NULL;
+
+ buf += nlmsg_len;
+ n->nm_nlh->nlmsg_len += tlen;
+
+ if (tlen > len)
+ memset(buf + len, 0, tlen - len);
+
+ NL_DBG(2, "msg %p: Reserved %zu bytes, pad=%d, nlmsg_len=%d\n",
+ n, len, pad, n->nm_nlh->nlmsg_len);
+
+ return buf;
+}
+
+/**
+ * Append data to tail of a netlink message
+ * @arg n netlink message
+ * @arg data data to add
+ * @arg len length of data
+ * @arg pad Number of bytes to align data to.
+ *
+ * Extends the netlink message as needed and appends the data of given
+ * length to the message.
+ *
+ * @return 0 on success or a negative error code
+ */
+int nlmsg_append(struct nl_msg *n, void *data, size_t len, int pad)
+{
+ void *tmp;
+
+ tmp = nlmsg_reserve(n, len, pad);
+ if (tmp == NULL)
+ return -NLE_NOMEM;
+
+ memcpy(tmp, data, len);
+ NL_DBG(2, "msg %p: Appended %zu bytes with padding %d\n", n, len, pad);
+
+ return 0;
+}
+
+/**
+ * Add a netlink message header to a netlink message
+ * @arg n netlink message
+ * @arg pid netlink process id or NL_AUTO_PID
+ * @arg seq sequence number of message or NL_AUTO_SEQ
+ * @arg type message type
+ * @arg payload length of message payload
+ * @arg flags message flags
+ *
+ * Adds or overwrites the netlink message header in an existing message
+ * object. If \a payload is greater-than zero additional room will be
+ * reserved, f.e. for family specific headers. It can be accesed via
+ * nlmsg_data().
+ *
+ * @return A pointer to the netlink message header or NULL.
+ */
+struct nlmsghdr *nlmsg_put(struct nl_msg *n, uint32_t pid, uint32_t seq,
+ int type, int payload, int flags)
+{
+ struct nlmsghdr *nlh;
+
+ if (n->nm_nlh->nlmsg_len < NLMSG_HDRLEN)
+ BUG();
+
+ nlh = (struct nlmsghdr *) n->nm_nlh;
+ nlh->nlmsg_type = type;
+ nlh->nlmsg_flags = flags;
+ nlh->nlmsg_pid = pid;
+ nlh->nlmsg_seq = seq;
+
+ NL_DBG(2, "msg %p: Added netlink header type=%d, flags=%d, pid=%d, "
+ "seq=%d\n", n, type, flags, pid, seq);
+
+ if (payload > 0 &&
+ nlmsg_reserve(n, payload, NLMSG_ALIGNTO) == NULL)
+ return NULL;
+
+ return nlh;
+}
+
+/**
+ * Release a reference from an netlink message
+ * @arg msg message to release reference from
+ *
+ * Frees memory after the last reference has been released.
+ */
+void nlmsg_free(struct nl_msg *msg)
+{
+ if (!msg)
+ return;
+
+ msg->nm_refcnt--;
+ NL_DBG(4, "Returned message reference %p, %d remaining\n",
+ msg, msg->nm_refcnt);
+
+ 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);
+}
+
+/** @} */
generated by cgit v1.1 at 2024-11-08 21:15:16 +0000