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Re: Ethernet stack sends empty fragment


On 03/01/2010 03:27 AM, Timo Gerber wrote:
Hi guys,
I'm working on an ethernet driver with scather gather support and I am wondering:
When sending UDP packets from the application with a higher payload-size (e.g. 2500Bytesand more), the ethernet stack calls my DRV_eth_send() function with a weird sg_list.
For instance, some packets are fragmented like this:
sg_list[1].len => 42
sg_list[1].buf => points to the hdr.

sg_list[2].len => 1472
sg_list[2].buf => points to the payload.

sg_list[3].len => 0
sg_list[3].buf => points to an empty buffer.

As you can see the last sg fragment is kinda weird, but this scheme appears all the time, not only now an then.

What's the MTU on that interface?


--
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Gary Thomas                 |  Consulting for the
MLB Associates              |    Embedded world
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