Re: [liblo] maximum size of message

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while you are generally right, ...

On 2014-09-19 16:31, to...@tr... wrote:
> -the sender *must* create chunks in order to send a continuous 
> ("unlimited") datastream. the question is how large these chunks
> can be at max.

this - unfortunately - is either wrong or misses the point.

the "missing the point" part: the network-layer (e.g. "IP") does some
packetizing on it's own. but this is totally transparent to both the
sender and receiver (application). the maximum size of these chunks is
the MTU and has an upper limit of 65535 bytes.

the "wrong" part: it's fairly easy to create an OSC-message of
*unlimited* size on the sender side, when you are dealing with a
serial datastream that is SLIP-encoded:

<snip>
MARK[]=[0xCE]; // slip packet boundary
bundle[]=[0x23,0x62,0x75,0x6E,0x64,0x6C,0x65,0] // "#bundle"
timestamp[]=[0,0,0,0,0,0,0,0x1];    // now
msg[]=[47, 120, 0, 0, 44, 0, 0, 0]; // "/x"

send(MARK);
send(bundle);
send(timestamp);
while(true) {
 send(len(msg);
 send(msg);
}
</snip>

just make sure you never send an END-mark and the packet keeps growing
on the receiving side, due to the semantics of the OSC-bundle
(messages within the bundle are atomic, so you cannot simply output
them as you receive them instead you have to wait till the end of the
bundle).

the above code is a DoS attack that will eat away all the memory of a
receiver that does not impose a maximum OSC packet size.


fgmdr
IOhannes
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