cvsup4.us.freebsd.org gives invalid greeting

[Randy Bush]

# csup -g -s -L 2 cvs-supfile 2>&1 | tee cvsup.log
Parsing supfile "cvs-supfile"
Connecting to cvsup4.us.freebsd.org
Connected to 2001:4f8:0:2::e
Invalid greeting from server