[lwip-devel] [bug #44805] sendmsg implementation to support scatter/gather IO

[Simon Goldschmidt]

Update of bug #44805 (project lwip):

                  Status:                 Invalid => None                   

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Follow-up Comment #3:

> I based the UDP support on how sendto() is implemented.

Ok, good point. Checking back on the multiple discussions we had about zero
copy, it seems like PBUF_REF is only zero-copy for non-DMA (i.e. non-delayed)
transmission. When you have a netif that enqueues data for sending (like
DMA-enabled interfaces would normally do), only PBUF_ROM allows true
zero-copy. PBUF_REF has to be copied to temporary buffers to prevent the
buffer being altered after netif->linkoutput returns.

I'm not too sure how wide this knowledge is spread around netif driver
developers, though... It seems like there is room for improvement in
documenting this.

Given that, the implementation looks correct.

BTW: why did you ifdef 'iovec' but not 'msghdr'?

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