The current openshift router images uses the Red Hat RPM package of haproxy. This package is maintained by Red Hat and uses haproxy 1.5 with some Red Hat patches.
You can see what’s in the package on centos git repo
It’s not bad but haproxy have now released the version 1.7.x, therefore there are several enhancements and bugfixes in the newer versions.
HAProxy 1.7 have a very nice feature called Stream Processing Offload Engine (SPOE).