/* * 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 */ /** * @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 * #include * #include * * 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 #include #include #include /** * @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 ((unsigned) 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; } /** @} */ /** @} */