From cfe5ab52ea5e014548b8169a3e02b8c88d3cbb18 Mon Sep 17 00:00:00 2001 From: Alexandre Courbot Date: Thu, 21 Oct 2021 23:56:03 +0900 Subject: [PATCH] mdbook: add instructions for network device setup BUG=none TEST=mdbook serve Change-Id: Id72c44201b248e20761ec38e2c892f5c4993ef46 Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3237468 Reviewed-by: Dennis Kempin Reviewed-by: Keiichi Watanabe Tested-by: kokoro Commit-Queue: Alexandre Courbot --- docs/book/src/running_crosvm/usage.md | 54 +++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) diff --git a/docs/book/src/running_crosvm/usage.md b/docs/book/src/running_crosvm/usage.md index 64230f5aa4..d37adeef9a 100644 --- a/docs/book/src/running_crosvm/usage.md +++ b/docs/book/src/running_crosvm/usage.md @@ -54,6 +54,60 @@ crosvm run --shared-dir "/:mtdfake:type=fs:cache=always" \ -p "rootfstype=virtiofs root=mtdfake" vmlinux ``` +## Network device + +The most convenient way to provide a network device to a guest is to setup a persistent TAP +interface on the host. This section will explain how to do this for basic IPv4 connectivity. + +```bash +sudo ip tuntap add mode tap user $USER vnet_hdr crosvm_tap +sudo ip addr add 192.168.10.1/24 dev crosvm_tap +sudo ip link set crosvm_tap up +``` + +These commands create a TAP interface named `crosvm_tap` that is accessible to the current user, +configure the host to use the IP address `192.168.10.1`, and bring the interface up. + +The next step is to make sure that traffic from/to this interface is properly routed: + +```bash +sudo sysctl net.ipv4.ip_forward=1 +# Network interface used to connect to the internet. +HOST_DEV=$(ip route get 8.8.8.8 | awk -- '{printf $5}') +sudo iptables -t nat -A POSTROUTING -o "${HOST_DEV}" -j MASQUERADE +sudo iptables -A FORWARD -i "${HOST_DEV}" -o crosvm_tap -m state --state RELATED,ESTABLISHED -j ACCEPT +sudo iptables -A FORWARD -i crosvm_tap -o "${HOST_DEV}" -j ACCEPT +``` + +The interface is now configured and can be used by crosvm: +```bash +crosvm run \ + ... + --tap-name crosvm_tap \ + ... +``` + +Provided the guest kernel had support for `VIRTIO_NET`, the network device should be visible and +configurable from the guest: + +```bash +# Replace with the actual network interface name of the guest +# (use "ip addr" to list the interfaces) +GUEST_DEV=enp0s5 +sudo ip addr add 192.168.10.2/24 dev "${GUEST_DEV}" +sudo ip link set "${GUEST_DEV}" up +sudo ip route add default via 192.168.10.1 +# "8.8.8.8" is chosen arbitrarily as a default, please replace with your local (or preferred global) +# DNS provider, which should be visible in `/etc/resolv.conf` on the host. +echo "nameserver 8.8.8.8" | sudo tee /etc/resolv.conf +``` + +These commands assign IP address `192.168.10.2` to the guest, activate the interface, and route +all network traffic to the host. The last line also ensures DNS will work. + +Please refer to your distribution's documentation for instructions on how to make these settings +persistent for the host and guest if desired. + ## Control Socket If the control socket was enabled with `-s`, the main process can be controlled