Re: [Minios-devel] Building with TCP/IP support (daytime) and problems with TCO

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Feb 27, 2018 at 07:08:18PM +0200, Razvan Cojocaru wrote:
> Hello,
> 
> I have tried building mini-os with TCP/IP support using lwip 1.3.2 and
> initially, the daytime server doesn't reply to TCP requests, even though
> there is connectivity. In a nutshell, ping works, but netcat on port 13
> doesn't.
> 
> After some digging, I realized that because of TCP Checksum Offloading,
> checksums are incorrect and the network stack of the guest system drops any
> TCP packets received.
> 
> In my opinion, there are two ways this issue could be addressed, and I
> would like to hear an opinion regarding which would be best:
> 1. Properly document the behavior and mention in the README how to turn off
> TCO for the guest interface
> e.g. # ethtool -K vif<id>.0 tx off

There are also some control flags that frontend can write to disable
that iirc.

> 2. Disable TCP checksum validation by default, using
> lwip's CHECKSUM_CHECK_TCP flag, so that new users (like myself) don't have
> to worry about these issues.

Check out _NETTXF_* flags in netif.h?

Netback should set those flags and you can map those flags into lwip
ones or take appropriate action.

Wei.

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