This reverts commit 5bed9f3f63.
Gal Presman says:
this patch broke geneve tunnels, or possibly all udp tunnels?
A simple test that creates two geneve tunnels and runs tcp iperf fails
and results in checksum errors (TcpInCsumErrors).
Original commit wanted to fix nf_reject with zero checksum,
so it appears better to change nf reject infra instead.
Fixes: 5bed9f3f63 ("netfilter: conntrack: mark UDP zero checksum as CHECKSUM_UNNECESSARY")
Reported-by: Gal Pressman <gal@nvidia.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>