Function otPlatDnsStartUpstreamQuery 

pub unsafe extern "C" fn otPlatDnsStartUpstreamQuery(
    aInstance: *mut otInstance,
    aTxn: *mut otPlatDnsUpstreamQuery,
    aQuery: *const otMessage,
)

Starts an upstream query transaction.

• In success case (and errors represented by DNS protocol messages), the platform is expected to call otPlatDnsUpstreamQueryDone.
• The OpenThread core may cancel a (possibly timeout) query transaction by calling otPlatDnsCancelUpstreamQuery, the platform must not call otPlatDnsUpstreamQueryDone on a cancelled transaction.

@param[in] aInstance The OpenThread instance structure. @param[in] aTxn A pointer to the opaque DNS query transaction object. @param[in] aQuery A message buffer of the DNS payload that should be sent to upstream DNS server.