Add SMB volume driver via direct guest CIFS mount

[tonycoco]

Add NFS and SMB volume drivers via direct guest mounts

Adds --driver nfs and --driver smb to container volume create. Both drivers mount network shares directly inside the Linux guest rather than going through virtiofs, eliminating the host-side mount hop.

When a volume is created with --driver smb or --driver nfs, no block image is created. The share path and options are stored as volume metadata. At container start, Utility.swift resolves the volume into a Filesystem.smb or Filesystem.nfs mount, which SandboxService.swift translates into a .any guest mount with type cifs or nfs respectively.

Usage:

SMB

container volume create --driver smb \
  --opt share=//192.168.1.1/Media \
  --opt username=user \
  --opt password=secret \
  --opt vers=3.0 \
  myshare

NFS

container volume create --driver nfs \
  --opt share=nas.local:/exports/data \
  --opt addr=nas.local \
  --opt vers=3 \
  --opt proto=tcp \
  myexport

container run -v myshare:/media alpine ls /media

Boolean mount flags (e.g. nolock, mfsymlinks) can be passed as --opt nolock= with an empty value and are serialized as bare flags in the mount data string.

Kernel requirement

This depends on a pending change to apple/containerization. The default guest kernel ships with CONFIG_CIFS=y disabled. A PR to that repo is needed to enable it in kernel/config-arm64 — without it, SMB mounts fail at runtime with errno 19 (ENODEV). NFS (CONFIG_NFS_FS) is already enabled in the current kernel config but is not compiled into the shipped kernel binary, so a rebuild is required for both drivers to work end-to-end.

The required containerization change is a single line in kernel/config-arm64:

# Before
# CONFIG_CIFS is not set

# After
CONFIG_CIFS=y
# CONFIG_CIFS_STATS2 is not set
CONFIG_CIFS_ALLOW_INSECURE_LEGACY=y
CONFIG_CIFS_UPCALL=y
CONFIG_CIFS_XATTR=y
CONFIG_CIFS_POSIX=y
# CONFIG_CIFS_DEBUG is not set
CONFIG_CIFS_DFS_UPCALL=y
# CONFIG_CIFS_SMB_DIRECT is not set

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update

Motivation and Context

#1413

Testing

• Tested locally
• Added/updated tests
• Added/updated docs