On Sun, Oct 07, 2007 at 09:58:06PM +0200, Tihomir Heidelberg - 9a4gl wrote:
> Using kernel 2.6.21.6 here. If you write to AX.25 socket bytes more then
> MTU, write will return -1 and errno will be set to 90 (EMSGSIZE =
> [Message too long]).
>
> This happend in net/ax25/af_ax25.c in function ax25_sendmsg at:
>
> if (len > ax25->ax25_dev->dev->mtu) {
> err = -EMSGSIZE;
> goto out;
> }
>
> Old kernels, 2.2.x and 2.4.x accepted write with data length larger then
> MTU and for SOCK_SEQPACKET sockets the ax25_output function did the
> fragmentation job.
Is it sensible to fragment raw AX.25 packets? I think that would depend
on what the next layer protocol is.
For APRS, each packet is significant (ie it's datagram rather than
stream oriented) so fragmenting a packet would not be correct. For IP
it's obviously allowed although you wouldn't be using an AX.25 socket
then.
> By the way, this problem is having OpenBCM V1.07b3, very popular BBS
> software (http://dnx274.dyndns.org/baybox/) which writes as much data as
> it prepared.
In your application (the other end of call, for example?) the packets
may just be a stream and therefore fragmenting at arbitrary points would
be ok. Although SOCK_SEQPACKET doesn't sound right in that case.
Hamish
--
Hamish Moffatt VK3SB <[EMAIL PROTECTED]> <[EMAIL PROTECTED]>
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