In Calico's released versions, when using the eBPF data plane,
containers using host ports cannot respond to connection attempts
correctly. These container receive the packets from the client
forwarded after DNAT, but when they reply, there is no conntrack entry
for the would-be connection, so netfilter drops the reply packets,
preventing the connection from completing. The client never receives
the reply packets. The conntrack entry is missing because Calico
mistakenly attempts to optimize it away.
Work around the problem by disabling the Calico Felix program's
"BPFHostConntrackBypass" feature. This is a temporary measure until
the Calico maintainers can improve this feature to better handle host
port traffic, preserving these conntrack entries as intended.
Steven E. Harris