| net_test v0.1 |
| ============= |
| |
| A simple framework for blackbox testing of kernel networking code. |
| |
| |
| Why use it? |
| =========== |
| |
| - Fast test / boot cycle. |
| - Access to host filesystem and networking via L2 bridging. |
| - Full Linux userland including Python, etc. |
| - Kernel bugs don't crash the system. |
| |
| |
| How to use it |
| ============= |
| |
| cd <kerneldir> |
| path/to/net_test/run_net_test.sh <test> |
| |
| where <test> is the name of a test binary in the net_test directory. This can |
| be an x86 binary, a shell script, a Python script. etc. |
| |
| |
| How it works |
| ============ |
| |
| net_test compiles the kernel to a user-mode linux binary, which runs as a |
| process on the host machine. It runs the binary to start a Linux "virtual |
| machine" whose root filesystem is the supplied Debian disk image. The machine |
| boots, mounts the root filesystem read-only, runs the specified test from init, and then drops to a shell. |
| |
| |
| Access to host filesystem |
| ========================= |
| |
| The VM mounts the host filesystem at /host, so the test can be modified and |
| re-run without rebooting the VM. |
| |
| |
| Access to host networking |
| ========================= |
| |
| Access to host networking is provided by tap interfaces. On the host, the |
| interfaces are named <user>TAP0, <user>TAP1, etc., where <user> is the first |
| 10 characters of the username running net_test. (10 characters because |
| IFNAMSIZ = 16). On the guest, they are named eth0, eth1, etc. |
| |
| net_test does not do any networking setup beyond creating the tap interfaces. |
| IP connectivity can be provided on the host side by setting up a DHCP server |
| and NAT, sending IPv6 router advertisements, etc. By default, the VM has IPv6 |
| privacy addresses disabled, so its IPv6 addresses can be predicted using a tool |
| such as ipv6calc. |
| |
| The provided filesystem contains a DHCPv4 client and simple networking |
| utilities such as ping[6], traceroute[6], and wget. |
| |
| The number of tap interfaces is currently hardcoded to two. To change this |
| number, modify run_net_test.sh. |
| |
| |
| Logging into the VM, installing packages, etc. |
| ============================================== |
| |
| net_test mounts the root filesystem read-only, and runs the test from init, but |
| since the filesystem contains a full Linux userland, it's possible to boot into |
| userland and modify the filesystem, for example to install packages using |
| apt-get install. Log in as root with no password. By default, the filesystem is |
| configured to perform DHCPv4 on eth0 and listen to RAs. |
| |
| |
| Bugs |
| ==== |
| |
| Since the test mounts the filesystem read-only, tests cannot modify |
| /etc/resolv.conf and the system resolver is hardcoded to 8.8.8.8. |
