/**
* mnl_nlmsg_put_extra_header - reserve and prepare room for an extra header
* \param nlh pointer to Netlink header
* \param size size of the extra header that we want to put
*
* This function sets to zero the room that is required to put the extra
* header after the initial Netlink header. This function also increases
* the nlmsg_len field. You have to invoke mnl_nlmsg_put_header() before
* you call this function. This function returns a pointer to the extra
* header.
*/
void *
mnl_nlmsg_put_extra_header(struct nlmsghdr *nlh, size_t size)
{
char *ptr = (char *)nlh + nlh->nlmsg_len;
nlh->nlmsg_len += MNL_ALIGN(size);
memset(ptr, 0, size);
return ptr;
}
/**
* mnl_attr_put_check - add an attribute to netlink message
* \param nlh pointer to the netlink message
* \param buflen size of buffer which stores the message
* \param type netlink attribute type that you want to add
* \param len netlink attribute payload length
* \param data pointer to the data that will be stored by the new attribute
*
* This function first checks that the data can be added to the message
* (fits into the buffer) and then updates the length field of the Netlink
* message (nlmsg_len) by adding the size (header + payload) of the new
* attribute. The function returns true if the attribute could be added
* to the message, otherwise false is returned.
*/
bool
mnl_attr_put_check(struct nlmsghdr *nlh, size_t buflen,
uint16_t type, size_t len, const void *data)
{
if (nlh->nlmsg_len + MNL_ATTR_HDRLEN + MNL_ALIGN(len) > buflen)
return false;
mnl_attr_put(nlh, type, len, data);
return true;
}
/**
* mnl_nlmsg_put_header - reserve and prepare room for Netlink header
* \param buf memory already allocated to store the Netlink header
*
* This function sets to zero the room that is required to put the Netlink
* header in the memory buffer passed as parameter. This function also
* initializes the nlmsg_len field to the size of the Netlink header. This
* function returns a pointer to the Netlink header structure.
*/
struct nlmsghdr *mnl_nlmsg_put_header(void *buf)
{
int len = MNL_ALIGN(sizeof(struct nlmsghdr));
struct nlmsghdr *nlh = buf;
memset(buf, 0, len);
nlh->nlmsg_len = len;
return nlh;
}
/**
* mnl_attr_nest_start - start an attribute nest
* \param nlh pointer to the netlink message
* \param type netlink attribute type
*
* This function adds the attribute header that identifies the beginning of
* an attribute nest. This function always returns a valid pointer to the
* beginning of the nest.
*/
struct nlattr *mnl_attr_nest_start(struct nlmsghdr *nlh, uint16_t type)
{
struct nlattr *start = mnl_nlmsg_get_payload_tail(nlh);
/* set start->nla_len in mnl_attr_nest_end() */
start->nla_type = NLA_F_NESTED | type;
nlh->nlmsg_len += MNL_ALIGN(sizeof(struct nlattr));
return start;
}
static ssize_t send_netlink_json(uint8_t *snd_buf,
struct json_object *parsed_obj, int32_t sock_fd,
struct sockaddr *netlink_addr)
{
struct nlmsghdr *netlink_hdr = (struct nlmsghdr*) snd_buf;
const char *json_str = json_object_to_json_string_ext(parsed_obj,
JSON_C_TO_STRING_PLAIN);
socklen_t netlink_addrlen = sizeof(netlink_addr);
memcpy(netlink_hdr + 1, json_str, strlen(json_str) + 1);
netlink_hdr->nlmsg_len = mnl_nlmsg_size(MNL_ALIGN(strlen(json_str)));
return sendto(sock_fd, snd_buf, netlink_hdr->nlmsg_len, 0, netlink_addr,
netlink_addrlen);
}
/**
* mnl_attr_next - get the next attribute in the payload of a netlink message
* \param attr pointer to the current attribute
*
* This function returns a pointer to the next attribute after the one passed
* as parameter. You have to use mnl_attr_ok() to ensure that the next
* attribute is valid.
*/
struct nlattr *mnl_attr_next(const struct nlattr *attr)
{
return (struct nlattr *)((void *)attr + MNL_ALIGN(attr->nla_len));
}
/**
* mnl_nlmsg_get_payload_tail - get the ending of the netlink message
* \param nlh pointer to netlink message
*
* This function returns a pointer to the netlink message tail. This is useful
* to build a message since we continue adding attributes at the end of the
* message.
*/
void *mnl_nlmsg_get_payload_tail(const struct nlmsghdr *nlh)
{
return (void *)nlh + MNL_ALIGN(nlh->nlmsg_len);
}
/**
* mnl_nlmsg_next - get the next netlink message in a multipart message
* \param nlh current netlink message that we are handling
* \param len length of the remaining bytes in the buffer (passed by reference).
*
* This function returns a pointer to the next netlink message that is part
* of a multi-part netlink message. Netlink can batch several messages into
* one buffer so that the receiver has to iterate over the whole set of
* Netlink messages.
*
* You have to use mnl_nlmsg_ok() to check if the next Netlink message is
* valid.
*/
struct nlmsghdr *
mnl_nlmsg_next(const struct nlmsghdr *nlh, int *len)
{
*len -= MNL_ALIGN(nlh->nlmsg_len);
return (struct nlmsghdr *)((void *)nlh + MNL_ALIGN(nlh->nlmsg_len));
}
/**
* mnl_nlmsg_get_payload_offset - get a pointer to the payload of the message
* \param nlh pointer to a netlink header
* \param offset offset to the payload of the attributes TLV set
*
* This function returns a pointer to the payload of the netlink message plus
* a given offset.
*/
void *
mnl_nlmsg_get_payload_offset(const struct nlmsghdr *nlh, size_t offset)
{
return (void *)nlh + MNL_NLMSG_HDRLEN + MNL_ALIGN(offset);
}