Correct. It does completely prevent the attack for IPv4, however, so we didn't notice the attack until the rp_filter settings were changed.

I can verify that turning rp_filter on in my use case is an acceptable solution on Manjaro and Ubuntu.

EDIT: To clear up the confusion below, I was saying that setting the rp_filter variable to strict mode does prevent this attack from working against IPv4, and in my situation, this is enough since I am not using IPv6 or any complicated routing on my network etc.