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.
I don't understand why it would be different for IPv6. are you just referring to the fact that there is no sysctl for reverse path filtering for IPv6? does it still work with ip6tables -t raw -A PREROUTING -m rpfilter --invert -j DROP?
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.