feat(session): add from_fds for externally pre-cloned fds#679
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XciD wants to merge 1 commit intocberner:masterfrom
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feat(session): add from_fds for externally pre-cloned fds#679XciD wants to merge 1 commit intocberner:masterfrom
XciD wants to merge 1 commit intocberner:masterfrom
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Add Session::from_fds(filesystem, primary_fd, extra_fds, acl, config) for callers that receive /dev/fuse fds cloned by a privileged helper (e.g. a CSI driver sending fds over SCM_RIGHTS). When extra_fds is non-empty: - Worker count = 1 + extra_fds.len() (config.n_threads ignored). - Workers use the supplied fds directly; config.clone_fd and the internal clone_fd() path (which opens /dev/fuse and so requires CAP_SYS_ADMIN) are skipped. Each extra fd must already be bound to the same FUSE connection as the primary (FUSE_DEV_IOC_CLONE ioctl); FUSE_INIT still happens on the primary during handshake(). from_fd is preserved as a thin wrapper over from_fds with no extras.
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Summary
Adds
Session::from_fds(filesystem, primary_fd, extra_fds, acl, config)for callers that receive/dev/fusefds cloned by a privileged helper (e.g. a CSI driver sending fds overSCM_RIGHTS).When
extra_fdsis non-empty:1 + extra_fds.len()(config.n_threadsis ignored).config.clone_fdand the internalclone_fd()path (which opens/dev/fuseand so requiresCAP_SYS_ADMIN) are skipped.Each extra fd must already be bound to the same FUSE connection as the primary (
FUSE_DEV_IOC_CLONEioctl);FUSE_INITstill happens on the primary duringhandshake().from_fdis preserved as a thin wrapper overfrom_fdswith no extras.Motivation
In some deployments (e.g. Kubernetes CSI drivers), an unprivileged process should not hold
CAP_SYS_ADMINand so cannot itself open/dev/fuseto clone the session fd. A privileged sidecar opens/dev/fuse, performsFUSE_DEV_IOC_CLONE, and passes the resulting fds to the worker over a Unix socket. This API lets the worker drive a multi-threaded session over those externally-cloned fds without ever opening/dev/fuseitself.