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SubjectRe: UDP bugs
On Mon, Dec 14, 1998 at 06:26:28PM +0300, kuznet@ms2.inr.ac.ru wrote:
> > The reason I expect this is that an application dealing with a UDP
> > socket shouldn't have to know the UDP, IP and MAC header sizes. What if
> > you pass it a non-ethernet bound address, and IPV6 bound socket, some
> > other datagram type, an IP with source route, etc.?
>
> Look at RFCs. Sane application should not send frames longer 576 bytes,
> if it is not sure that destination will accept this.
> For IPv6 this limit is changed to 1500, not more. 8)
> And it is full frame size... Take into account that
> fragmentation is strongly discouraged too 8)8)

That was not my point.
I agree, that the default buffer size should be small.

I'm saying that SO_RCVBUF should change the maximum _application_ packet
size, not the raw size with UDP, IP and MAC headers included.

So setsockopt(fd, SOL_SOCKET, SO_RCVBUF, 16384) should be enough
to permit receiving 16384 _application_ bytes per packet.

> What's about maximal received frame size, I'd set default maximum
> to 4K. Apps, which really expect larger packets, must increase it themselves.
>
> Remeber, if host does not have gobs of unused memory 64K skb is serious
> pain for our memory allocator, 128K is reliable death.

Agree, agree, but I think you missed my point :-)

-- Jamie

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