pc and linux are connected directly through the network cable, start silp network port, and create tun0 on linux at the same time. Now you need to send multicast packets through pc->eth0->tun0, but it is found that the data packets stop when they reach eth0 through tcpdump.

I can catch the packet by ping tun0 eth0 on linux as well as by sending unicast packets on PC under tun0 configuration below.enter image description here