Function BuildProbeMessage

engine/dlib/src/dlib/mdns.cpp:1120–1183

    }

    static uint32_t BuildProbeMessage(const RegisteredService& service, uint8_t* buffer, uint32_t buffer_size)
    {
        uint32_t offset = 0;
        ProbeRecord service_records[2];
        ProbeRecord host_records[1];
        const uint32_t service_record_count = BuildServiceProbeRecordSet(service, service_records, DM_ARRAY_SIZE(service_records));
        const uint32_t host_record_count = BuildHostProbeRecordSet(service, host_records, DM_ARRAY_SIZE(host_records));

        // RFC 6762 probing is done against the unique RRsets we intend to own.
        // For DNS-SD that means the SRV/TXT pair at the full service instance
        // name, not the shared PTR at the service type. Authority records carry
        // the tentative rdata so simultaneous probes can be tie-broken.
        const uint16_t question_count = host_record_count > 0 ? 2 : 1;
        const uint16_t authority_count = (uint16_t) (service_record_count + host_record_count);
        if (service_record_count != 2)
            return 0;

        if (!WriteU16(buffer, buffer_size, &offset, 0)
            || !WriteU16(buffer, buffer_size, &offset, 0)
            || !WriteU16(buffer, buffer_size, &offset, question_count)
            || !WriteU16(buffer, buffer_size, &offset, 0)
            || !WriteU16(buffer, buffer_size, &offset, authority_count)
            || !WriteU16(buffer, buffer_size, &offset, 0)
            || !WriteName(buffer, buffer_size, &offset, service.m_FullServiceName)
            || !WriteU16(buffer, buffer_size, &offset, DNS_TYPE_ANY)
            || !WriteU16(buffer, buffer_size, &offset, DNS_CLASS_IN))
        {
            return 0;
        }

        if (host_record_count > 0
            && (!WriteName(buffer, buffer_size, &offset, service.m_HostLocal)
                || !WriteU16(buffer, buffer_size, &offset, DNS_TYPE_ANY)
                || !WriteU16(buffer, buffer_size, &offset, DNS_CLASS_IN)))
        {
            return 0;
        }

        for (uint32_t i = 0; i < service_record_count; ++i)
        {
            if (!WriteCanonicalRecord(buffer, buffer_size, &offset,
                                      service.m_FullServiceName,
                                      service_records[i].m_Type,
                                      service_records[i].m_Class,
                                      service.m_Ttl,
                                      service_records[i].m_RData,
                                      service_records[i].m_RDataLength))
                return 0;
        }

        for (uint32_t i = 0; i < host_record_count; ++i)
        {
            if (!WriteCanonicalRecord(buffer, buffer_size, &offset,
                                      service.m_HostLocal,
                                      host_records[i].m_Type,
                                      host_records[i].m_Class,
                                      service.m_Ttl,
                                      host_records[i].m_RData,