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I'm trying to setup a bridge between my Wi-Fi connection and an emulator (QEMU). I need a virtual machine to be on the same LAN as the host, with its own IP address.

QEMU requires using a TAP (virtual network device) so I have installed tuntaposx, have it running, and can open up QEMU using a TAP:

qemu-system-arm -kernel zImage.integrator -initrd arm_root.img -m 256 -net nic -net tap,ifname=tap1 -nographic -append "console=ttyAMA0"

I have a script that configures the bridge once QEMU has opened up the TAP interface:

sysctl -w net.link.ether.inet.proxyall=1
sysctl -w net.inet.ip.forwarding=1
sysctl -w net.inet.ip.fw.enable=1
ifconfig bridge0 create
ifconfig bridge0 addm en1
ifconfig tap1 0.0.0.0 up
ifconfig bridge0 addm tap1
ifconfig bridge0 up

If I manually set an IP on the VM, I can ping from the VM to the host, but not from the host to the VM. Also, I can't access the rest of the network from the VM - including not being able to set an IP over DHCP.

Any ideas?

penx
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2 Answers2

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You are forgetting 2 important steps : running the natd daemon and configuring the firewall to allow that traffic, ie :

natd -interface en0 ipfw add divert natd ip from any to any via en0

en0 is my wifi interface (macbook air) and this work like a charm. The proposed openvpn solution is overtly complicated.

You can also run natd in fancier ways (ex: # fancy: natd -alias_address 10.0.0.2 -interface en0 -use_sockets -same_ports -unregistered_only -dynamic -clamp_mss) if you want to be very specific, but the above will work.

I detailed the whole process on http://en.blog.guylhem.net/post/88201449689/running-qemu-with-tap0-and-nat-under-osx-10-9-maverick

guylhem
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  • Blog link appears dead, but the instructions would seem to be replicated at: https://github.com/ckujau/scripts/blob/master/qemu-tap.sh – Arto Bendiken Aug 02 '16 at 11:55
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-netdev tap,id=xxx,ifname=tap0 -device e1000,netdev=xxx. You need device-specific and make sure your kernel supports it, intel e1000 should be universally supported. I fixed the bridge problem on my mac running a x86 VM, since I don't need to connect to the internet, in my case, I just need to connect multiple VM in the host network. So I didn' addm en0. P.S. remember to have a addm script, the qemu -netdev tap will alert this error to you. Hope this will fix your problem.

Tong Xing
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