Use passt for user-mode networking on crosvm. - #3071
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Currenly, for cuttlefish guest network access, the host requires tap devices to be preconfigured or dynamically configured with cvdalloc. Both require some manner of elevated privileges in the execution environment, which can be inconvenient for external network access, or prevents network access entirely in some execution environments. User-mode networking is the typical mechanism to work around this requirement, and slirp is the typical implementation for this. However, while slirp is available in qemu, it is not available on all platforms for crosvm. To work around this, for now we use vhost-user and passt. If slirp is supported in crosvm on more platforms in the future, then we can pivot. Currently, only the mobile interface is set up with passt. Doing this correctly for Wi-Fi will require more care, and for now, having some basic user-mode networking is better than none. Bug: 286284441
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Currenly, for cuttlefish guest network access, the host requires tap
devices to be preconfigured or dynamically configured with cvdalloc.
Both require some manner of elevated privileges in the execution
environment, which can be inconvenient for external network access, or
prevents network access entirely in some execution environments.
User-mode networking is the typical mechanism to work around this
requirement, and slirp is the typical implementation for this. However,
while slirp is available in qemu, it is not available on all platforms
for crosvm.
To work around this, for now we use vhost-user and passt. If slirp is
supported in crosvm on more platforms in the future, then we can pivot.
Currently, only the mobile interface is set up with passt. Doing this
correctly for Wi-Fi will require more care, and for now, having some
basic user-mode networking is better than none.
Bug: 286284441
To expedite things, I'm sending this for review now while dependent prs covering the other commits are now being merged in #3056 and #3057. Once landed, I'll rebase this branch. For now, you can focus your attention on the changes in ccd3551.