On 2017年05月03日 11:43, Zhang Chen wrote:


On 05/02/2017 12:53 PM, Jason Wang wrote:


On 2017年04月28日 17:47, Zhang Chen wrote:
Address Jason Wang's comments add vnet header length to SocketReadState.

Instead of saying this, you can add "Suggested-by: Jason Wang <jasow...@redhat.com>" above your sign-off.

OK.


So we change net_fill_rstate() to read
struct  {int size; int vnet_hdr_len; const uint8_t buf[];}.

This makes me thinking about the backward compatibility. I think we'd better try to keep it as much as possible. E.g how about pack vnet_hdr_len into higher bits of size?


Do you means split uint32_t size to uint16_t size and uint16_t vnet_hdr_len ?
If yes, we also can't keep compatibility with old version.
Old code send a uint32_t size, we read it as uint16_t size is always wrong.

Thanks
Zhang Chen

Consider it's unlikely to send or receive packet >= 64K, we can reuse higher bits (e.g highest 8 bits). Then we can still read uint32_t and then check its highest 8 bits. If it was zero, we know vnet header is zero, if not it could be read as vnet header length.

Thanks


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