kola/qemuexec: allow changing guest network #3645
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For local testing, it's useful to have an easy way to netboot a system. Enable this by exposing QEMU's builtin support for TFTP serving and BOOTP option. For iPXE, one can just directly pass the iPXE script. For PXELINUX/GRUB, you'll likely want to prepare a netboot directory with your artifacts. Probably this should be streamlined more in the future, and also deduped more with the related bits in `metal.go`. But anyway, for now this is immediately useful in helping to test root on iSCSI locally (via iPXE's `sanboot` option).
This is useful when you're nesting VMs and you want the first VM to be able to access the host. The default host address that QEMU assigns (e.g. 10.0.2.2, modifiable via the `host=...` netdev knob) doesn't always work because it's not actually an IP address owned by the host, but proxied by QEMU itself. So the source appears to come from localhost, but in some contexts (e.g. iSCSI), we need the host and the guest to agree that the same IP refers to the host. With this, one can start the first VM as usual (e.g. `cosa run`) and the second VM within with e.g. `cosa run --usernet-addr 10.0.3.0/24` and be able to talk back to the outer VM via the valid address 10.0.2.15. To be clear, this can all be done with passthrough QEMU args, so this is just about making it more convenient.
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Requires #3644 (for conflicts, not conceptually). |
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This is useful when you're nesting VMs and you want the first VM to
be able to access the host. The default host address that QEMU assigns
(e.g. 10.0.2.2, modifiable via the
host=...netdev knob) doesn'talways work because it's not actually an IP address owned by the host,
but proxied by QEMU itself.
So the source appears to come from localhost, but in some contexts (e.g.
iSCSI), we need the host and the guest to agree that the same IP refers
to the host.
With this, one can start the first VM as usual (e.g.
cosa run) and thesecond VM within with e.g.
cosa run --usernet-addr 10.0.3.0/24and beable to talk back to the outer VM via the valid address 10.0.2.15.
To be clear, this can all be done with passthrough QEMU args, so this is
just about making it more convenient.