Add limit to ioutil.ReadAll for request body (#5224)
Add limit to ioutil.ReadAll for request body (#5224)

This PR adds limit to ioutil.ReadAll for DoH request body
so that it will not be subject to large requests.

Signed-off-by: Yong Tang <765086fe2e0c1f980161f127fec596800f327f62@outlook.com>
yongtang/coredns,chrisohaver/coredns,coredns/coredns