qemu起虚拟机的网络配置

来自https://gist.github.com/extremecoders-re/e8fd8a67a515fee0c873dcafc81d811c

Setting up Qemu with a tap interface

There are two parts to networking within QEMU:

• The virtual network device that is provided to the guest (e.g. a PCI network card).
• The network backend that interacts with the emulated NIC (e.g. puts packets onto the host's network).

Example: User mode network

User mode networking allows the guest to connect back to the outside world through TCP, UDP etc. ICMP Ping is not allowed. Also connections from host to guest are not allowed unless using port forwarding.

$ qemu-system-i386 -cdrom Core-current.iso -boot d -netdev user,id=mynet0,hostfwd=tcp::8080-:80 -device e1000,netdev=mynet0

-netdev user,id=mynet0,hostfwd=tcp::8080-:80

Create the user mode network backend having id mynet0. Redirect incoming tcp connections on host port 8080 to guest port 80. The syntax is hostfwd=[tcp|udp]:[hostaddr]:hostport-[guestaddr]:guestport

-device e1000,netdev=mynet0

Create a NIC (model e1000) and connect to mynet0 backend created by the previous parameter

Example: Tap network

TAP network overcomes all of the limitations of user mode networking, but requires a tap to be setup before running qemu. Also qemu must be run with root privileges.

$ sudo qemu-system-i386 -cdrom Core-current.iso -boot d -netdev tap,id=mynet0,ifname=tap0,script=no,downscript=no -device e1000,netdev=mynet0,mac=52:55:00:d1:55:01

-netdev tap,id=mynet0,ifname=tap0,script=no,downscript=no

Create a tap network backend with id mynet0. This will connect to a tap interface tap0 which must be already setup. Do not use any network configuration scripts.

-device e1000,netdev=mynet0,mac=52:55:00:d1:55:01

Create a NIC (model e1000) and connect to mynet0 backend created by the previous parameter. Also specify a mac address for the NIC.

Setup

• Create a bridge

   brctl addbr br0
  

• Clear IP of eth0

   ip addr flush dev eth0
  

• Add eth0 to bridge

   brctl addif br0 eth0
  

• Create tap interface

   tunctl -t tap0 -u `whoami`
  

• Add tap0 to bridge

   brctl addif br0 tap0
  

• Make sure everything is up

   ifconfig eth0 up
   ifconfig tap0 up
   ifconfig br0 up
  

• Check if properly bridged

   brctl show
  

• Assign ip to br0

   dhclient -v br0
  

Cleanup

• Remove tap interface tap0 from bridge br0

  brctl delif br0 tap0
  

• Delete tap0

  tunctl -d tap0
  

• Remove eth0 from bridge

  brctl delif br0 eth0
  

• Bring bridge down

  ifconfig br0 down
  

• Remove bridge

  brctl delbr br0
  

• Bring eth0 up

  ifconfig eth0 up
  

• Check if an IP is assigned to eth0, if not request one

  dhclient -v eth0
  

dhclient - Auto configuration using a DHCP server

• Release IP

  dhclient -v -r 
  

• Request IP

  dhclient -v