Difference between revisions of "Ir:USER"

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m (Undo revision 12391 by Socram8888 (talk))
 
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This service was added with [[2.0.0-2]]. It employs a custom packet format with obfuscation and error detection.
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#REDIRECT [[IR Services#IR Service "ir:USER"]]
 
 
= Command set =
 
When sending data, SendIrnop is used when the size is <=0xFC, otherwise SendIrnopLarge is used.
 
 
 
{| class="wikitable" border="1"
 
|-
 
!  Command Header
 
!  Available since system version
 
!  Description
 
|-
 
| 0x00010182
 
| [[2.0.0-2]]
 
| InitializeIrnop
 
|-
 
| 0x00020000
 
| [[2.0.0-2]]
 
| FinalizeIrnop
 
|-
 
| 0x00030000
 
| [[2.0.0-2]]
 
| ClearReceiveBuffer
 
|-
 
| 0x00040000
 
| [[2.0.0-2]]
 
| ClearSendBuffer
 
|-
 
| 0x0005....
 
| [[2.0.0-2]]
 
| WaitConnection
 
|-
 
| 0x00060040
 
| [[2.0.0-2]]
 
| RequireConnection (u8 input)
 
|-
 
| 0x0007....
 
| [[2.0.0-2]]
 
| AutoConnection
 
|-
 
| 0x0008....
 
| [[2.0.0-2]]
 
| AnyConnection
 
|-
 
| 0x00090000
 
| [[2.0.0-2]]
 
| Disconnect
 
|-
 
| 0x000A0000
 
| [[2.0.0-2]]
 
| GetReceiveEvent (writes event handle to cmdreply[3])
 
|-
 
| 0x000B0000
 
| [[2.0.0-2]]
 
| GetSendEvent (writes event handle to cmdreply[3])
 
|-
 
| 0x000C0000
 
| [[2.0.0-2]]
 
| GetConnectionStatusEvent (writes event handle to cmdreply[3])
 
|-
 
| 0x000D0042
 
| [[2.0.0-2]]
 
| SendIrnop (u32 size, ((Size<<14) <nowiki>|</nowiki> 2), inbufptr)
 
|-
 
| 0x000E0042
 
| [[2.0.0-2]]
 
| SendIrnopLarge (u32 size, ((Size<<8) <nowiki>|</nowiki> 10), inbufptr)
 
|-
 
| 0x000F....
 
| [[2.0.0-2]]
 
| ReceiveIrnop
 
|-
 
| 0x0010....
 
| [[2.0.0-2]]
 
| ReceiveIrnopLarge
 
|-
 
| 0x0011....
 
| [[2.0.0-2]]
 
| GetLatestReceiveErrorResult
 
|-
 
| 0x0012....
 
| [[2.0.0-2]]
 
| GetLatestSendErrorResult
 
|-
 
| 0x0013....
 
| [[2.0.0-2]]
 
| GetConnectionStatus
 
|-
 
| 0x0014....
 
| [[2.0.0-2]]
 
| GetTryingToConnectStatus
 
|-
 
| 0x0015....
 
| [[2.0.0-2]]
 
| GetReceiveSizeFreeAndUsed
 
|-
 
| 0x0016....
 
| [[2.0.0-2]]
 
| GetSendSizeFreeAndUsed
 
|-
 
| 0x0017....
 
| [[2.2.0-X]]
 
| GetConnectionRole
 
|-
 
| 0x00180182
 
| [[2.2.0-X]]
 
| InitializeIrnopShared (u32, u32, u32, u32, u32, u8, 0, handle)
 
|-
 
| 0x00190040
 
| [[2.2.0-X]]
 
| ReleaseReceivedData (32bit_value input)
 
|-
 
| 0x001A0040
 
| [[2.2.0-X]]
 
| SetOwnMachineId (u8 input)
 
|}
 
 
 
= Protocol description =
 
Packets are sent using IrDA-SIR, with a 8N1 encoding (eight data bits, one stop bit, without parity). Each one is formed by a 2-byte header, a varint with the payload size, an obfuscated payload, and trailing error detection byte.
 
 
 
== Packet header ==
 
The packet header is fixed and consists in a synchronization byte (0xA5), followed by a unused (possibly RFU) zero byte. After these two hardcoded bytes, there's a varint representing the payload size, which may use one byte or two, depending on the how big the payload is.
 
 
 
* For payloads with less than 64 bytes, the third byte represents the payload size.
 
* For packets with up to 16383 bytes, the size is split in two bytes, with the third byte being the upper 6 bits of the payload size, OR'd with 0x40, and the fourth being the lower eight bits of the payload size
 
 
 
For packets with less than 64 bytes:
 
{| class="wikitable" border="1"
 
! Sync
 
! RFU
 
! Size
 
|-
 
| 0xA5
 
| 0x00
 
| size
 
|}
 
 
 
For packets with up to 16383 bytes:
 
{| class="wikitable" border="1"
 
! Sync
 
! RFU
 
! Size (1)
 
! Size (2)
 
|-
 
| 0xA5
 
| 0x00
 
| (size >> 8) <nowiki>|</nowiki> 0x40
 
| size & 0xFF
 
|}
 
 
 
In C:
 
<nowiki>uint8_t * setPacketHeader(uint8_t * buffer, size_t payloadSize) {
 
assert(payloadSize < 16384);
 
 
 
buffer[0] = 0xA5;
 
buffer[1] = 0x00;
 
 
 
if (payloadSize < 64) {
 
buffer[2] = payloadSize;
 
buffer += 3;
 
} else {
 
buffer[2] = 0x40 | (payloadSize >> 8);
 
buffer[3] = payloadSize;
 
buffer += 4;
 
}
 
 
 
return buffer;
 
}</nowiki>
 
 
 
== Payload ==
 
The payload is obfuscated using a XOR-based encryption. In C:
 
<nowiki>void payloadObfuscate(const void * voidplain, void * voidcipher, size_t size) {
 
uint16_t * plain = (uint16_t *) voidplain;
 
uint16_t * cipher = (uint16_t *) voidcipher;
 
size_t halfCount = size / sizeof(uint16_t);
 
 
 
uint16_t xorval = htobe16(0xE963);
 
size_t i;
 
 
 
for (i = 0; i < halfCount; i++) {
 
xorval ^= plain[i];
 
cipher[i] = xorval;
 
}
 
}
 
 
 
void payloadDeobfuscate(const void * voidcipher, void * voidplain, size_t size) {
 
uint16_t * cipher = (uint16_t *) voidcipher;
 
uint16_t * plain = (uint16_t *) voidplain;
 
size_t halfCount = size / sizeof(uint16_t);
 
 
 
if (halfCount) {
 
size_t i;
 
for (i = halfCount - 1; i > 0; i--) {
 
plain[i] = cipher[i] ^ cipher[i - 1];
 
}
 
 
 
plain[0] = cipher[0] ^ htobe16(0xE963);
 
}
 
}</nowiki>
 
 
 
== Error detection ==
 
The trailing error detection byte is calculated using [[CRC-8-CCITT]] <b>over the whole packet</b> (both the header and the payload)
 

Latest revision as of 16:21, 17 April 2015