[Qemu-discuss] tap network not working properly on kernel 4.14

[Max Blau]

I've placed a tap0 adapter into an OpenWrt system (kernel 4.14). The
tap0 device cannot access any other subnets, packets don't get
forwarded. That's unexpected behavior. Deploying the image 1:1 to real
hardware substituting the tap0 interface with a real NIC magically works
properly. Also, using QEMU with an Arch Linux guest (kernel 5.1.3) works
as expected as well. So, my guess is there's something picky about the
4.14 kernel (or OpenWrt in particular). Full details here:
https://superuser.com/questions/1438816/openwrt-in-qemu-no-response-from-other-subnets-with-tap-network

Is there anything known about this issue?

Linux 5.1.3-arch1-1-ARCH #1 SMP PREEMPT Thu May 16 20:59:36 UTC 2019
x86_64 GNU/Linux
qemu-x86_64 version 4.0.0