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Skip copying melondDS default MAC address #4648

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cc886d2
Skip copying melondDS default MAC address
Real96 Mar 2, 2026
c865994
Check if external firmware MAC address is valid
Real96 Mar 2, 2026
7efe60e
Rebuild melonDS
Real96 Mar 3, 2026
3b4c71c
update melondDS MAC address validation
Real96 Apr 5, 2026
1a6bc52
update comments
Real96 Apr 6, 2026
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Binary file modified Assets/dll/melonDS.wbx.zst
100644 → 100755
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23 changes: 22 additions & 1 deletion waterbox/melon/BizConsoleCreator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -63,6 +63,17 @@ static std::unique_ptr<T> CreateBiosImage(u8* biosData, u32 biosLength, std::opt
return std::move(bios);
}

static bool isValidMacAddress(const melonDS::MacAddress& mac)
{
// Invalid 48bit MAC address: FF:FF:FF:FF:FF:FF
const bool isAll0xFF = mac[0] == 0xFF && mac[1] == 0xFF && mac[2] == 0xFF && mac[3] == 0xFF && mac[4] == 0xFF && mac[5] == 0xFF;

// Broadcast channel 48bit MAC address: 03:09:BF:XX:XX:XX
const bool isBroadsast = mac[0] == 0x03 && mac[1] == 0x09 && mac[2] == 0xBF;

return !isAll0xFF || !isBroadsast;
}

static void SanitizeExternalFirmware(melonDS::Firmware& firmware)
{
auto& header = firmware.GetHeader();
Expand All @@ -84,7 +95,17 @@ static void SanitizeExternalFirmware(melonDS::Firmware& firmware)
memset(&header.Bytes[0x28], 0xFF, 2);
}

memcpy(&header.Bytes[0x2C], &defaultHeader.Bytes[0x2C], 0x136);
memcpy(&header.Bytes[0x2C], &defaultHeader.Bytes[0x2C], 10);

// MAC address offset is 0x36, so we skip writing from 0x36 to 0x3B (48 bit)
// to avoid copying melonDS default MAC address 0x0009BF112233
// only if the external firmware MAC address is valid
if (!isValidMacAddress(header.MacAddr))
{
memcpy(&header.Bytes[0x36], &defaultHeader.Bytes[0x36], 6);
}

memcpy(&header.Bytes[0x3C], &defaultHeader.Bytes[0x3C], 0x126);
memset(&header.Bytes[0x162], 0xFF, 0x9E);

if (isDSiFw)
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