Re: [PATCH 1/1] net: tun: add XDP metadata support

quoted

quoted

quoted

+		metasize = metasize > 0 ? metasize : 0;

Why is this part needed?

When an xdp_buff was initialized withouth metadata support (meta_valid
argument of xdp_prepare_buff is false), then data_meta == data + 1.
So this check makes sure that metadata was supported for the given xdp_buff
and metasize is not -1 (data - data_meta).

But you have a good point here: Because we have control over the
initialization of xdp_buff in the tun_build_skb function (first code path),
we know, that metadata is always supported for that buffer and metasize
is never < 0. So this check is redundant and I'll remove it.

But in the tun_xdp_one function (second code path), I'd prefer to keep that
check, as the xdp_buff is externally passed to tun_sendmsg and the tun driver
should probably not make assumptions about the metadata support of buffers
created by other drivers (e.g. vhost_net).

Thank you for taking a look, I hope things are more clear now.

Please use min()

Err.. max.