Re: [PATCH] udp: resubmit encapsulation packets on all multicast listeners

[Mariano Baragiola <mbaragiola@linux.com>]

Thanks for checking this.

I fetched current net and confirmed that 3cb8d4b9bfeb is now present, so the primary-path issue is fixed there.

I also checked the SO_BINDTODEVICE case. Although different bound devices can bypass the port-use equality check, multicast delivery requires the socket's bound device to match the packet's ingress device. Those sockets therefore cannot become multiple matching listeners for the same multicast packet. FOU/GUE sockets also do not enable SO_REUSEADDR or SO_REUSEPORT.

The secondary clone path is therefore not reachable for the positive encapsulation return. I will withdraw this patch rather than repost it.

For completeness, I found the original issue while comparing the multicast receive path with the unicast and GSO paths, then confirmed it with a focused FOU probe against clean and patched kernels. The clean kernel dropped the multicast encapsulated packets; the patched kernel resubmitted them to the IP protocol handler.

Thanks again for the review.