We use the conntrack method to avoid patching the kernel. An established connection needs to be broken (i.e. stop the ping in your example), but it’s a matter of timeout in real life examples.
We already discussed this topic in this forum and came to the conclusion that route cache clearing is often unnecessary and sometimes harmful.
Moreover, http is a connection-less protocol that works well with NethServer multi wan setup.
If you use specific protocols that need custom configurations, I’ll gladly help in fine tuning the setup.
DGD is done by lsm, pinging remore hosts (decision taken here before we re implemented multi wan from scratch).