[ECOS] max IP packet size = 9216 B. Why?

Andrew Lunn andrew@lunn.ch
Tue Jun 12 22:12:00 GMT 2007

On Tue, Jun 12, 2007 at 05:49:30PM +0200, J?rgen Lambrecht wrote:
> Hello,
> I found out that the maximum IP packet size = 9216 B (0x2400).
> I implemented an echo program, both udp and tcp.
> My ecos applic can receive more that 9216B, but not send back more than 
> that.
> Has anybody a clue how to solve this?
> I need to support the maximum IP packet size of 65535 B (IP_MAXPACKET).

Interesting. What network technology do you have underneath
this. Something reliable i presume since even small packet error rates
are going to cause big delay and inefficiencies with retries.

> I don't know if this is a bug in ecos, or a (hidden?) limitation of an 
> embedded OS.

I don't know of anybody else using nearly jumbo packets. So you might
be running into bugs, or configuration tweaks might be needed.

> I'm busy tracing this back in the source
> This comes from the socket that is allocated statically in 
> /io/fileio/.../fd.cxx and socket is part of a cyg_file (cyg_file is 
> defined by file in file.h). In cyg_file there is a member f_data, which 
> is the socket.
> I'm continuing my search in the code at this point....

Do you get a crash, or does write/sendto return an error code?


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