[pve-devel] [PATCH v3 container 1/1] Add device passthrough
Wolfgang Bumiller
w.bumiller at proxmox.com
Fri Nov 10 11:44:29 CET 2023
On Tue, Nov 07, 2023 at 02:46:42PM +0100, Filip Schauer wrote:
> Add a dev[n] argument to the container config to pass devices through to
> a container. A device can be passed by its path. Additionally the access
> mode, uid and gid can be specified through their respective properties.
>
> Signed-off-by: Filip Schauer <f.schauer at proxmox.com>
> ---
> src/PVE/LXC.pm | 29 +++++++++++++-
> src/PVE/LXC/Config.pm | 79 +++++++++++++++++++++++++++++++++++++++
> src/PVE/LXC/Tools.pm | 23 +++++++++---
> src/lxc-pve-autodev-hook | 14 ++++++-
> src/lxc-pve-prestart-hook | 63 +++++++++++++++++++++++++++++++
> 5 files changed, 201 insertions(+), 7 deletions(-)
>
> diff --git a/src/PVE/LXC.pm b/src/PVE/LXC.pm
> index 7ec816b..162f093 100644
> --- a/src/PVE/LXC.pm
> +++ b/src/PVE/LXC.pm
> @@ -5,7 +5,7 @@ use warnings;
>
> use Cwd qw();
> use Errno qw(ELOOP ENOTDIR EROFS ECONNREFUSED EEXIST);
> -use Fcntl qw(O_RDONLY O_WRONLY O_NOFOLLOW O_DIRECTORY);
> +use Fcntl qw(O_RDONLY O_WRONLY O_NOFOLLOW O_DIRECTORY :mode);
> use File::Path;
> use File::Spec;
> use IO::Poll qw(POLLIN POLLHUP);
> @@ -639,6 +639,33 @@ sub update_lxc_config {
> $raw .= "lxc.mount.auto = sys:mixed\n";
> }
>
> + PVE::LXC::Config->foreach_passthrough_device($conf, sub {
> + my ($key, $device) = @_;
> +
> + die "Path is not defined for passthrough device $key"
> + unless (defined($device->{path}));
> +
> + my $absolute_path = $device->{path};
> +
> + die "Device $absolute_path does not exist\n"
> + unless (-e $absolute_path);
> +
> + my ($mode, $rdev) = (stat($absolute_path))[2, 6];
> +
> + die "Could not get mode of device $absolute_path\n"
> + if $mode !~ /^([\d]+)$/;
> + $mode = $1;
> +
> + die "Could not get device ID of $absolute_path\n"
> + if $rdev !~ /^([\d]+)$/;
> + $rdev = $1;
^ The above 2 checks don't seem necessary. `stat()` cannot return
different types of values there.
Just check them for definedness once together.
> +
> + my $major = PVE::Tools::dev_t_major($rdev);
> + my $minor = PVE::Tools::dev_t_minor($rdev);
> + my $device_type_char = S_ISBLK($mode) ? 'b' : 'c';
> + $raw .= "lxc.cgroup2.devices.allow = $device_type_char $major:$minor rw\n";
> + });
> +
> # WARNING: DO NOT REMOVE this without making sure that loop device nodes
> # cannot be exposed to the container with r/w access (cgroup perms).
> # When this is enabled mounts will still remain in the monitor's namespace
> diff --git a/src/PVE/LXC/Config.pm b/src/PVE/LXC/Config.pm
> index 56e1f10..b4fa147 100644
> --- a/src/PVE/LXC/Config.pm
> +++ b/src/PVE/LXC/Config.pm
> @@ -29,6 +29,7 @@ mkdir $lockdir;
> mkdir "/etc/pve/nodes/$nodename/lxc";
> my $MAX_MOUNT_POINTS = 256;
> my $MAX_UNUSED_DISKS = $MAX_MOUNT_POINTS;
> +my $MAX_DEVICES = 256;
>
> # BEGIN implemented abstract methods from PVE::AbstractConfig
>
> @@ -908,6 +909,57 @@ for (my $i = 0; $i < $MAX_UNUSED_DISKS; $i++) {
> }
> }
>
> +PVE::JSONSchema::register_format('pve-lxc-dev-string', \&verify_lxc_dev_string);
> +sub verify_lxc_dev_string {
> + my ($dev, $noerr) = @_;
> +
> + if (
> + $dev =~ m@/\.\.?/@ ||
> + $dev =~ m@/\.\.?$@ ||
> + $dev !~ m!^/dev/!
> + ) {
> + return undef if $noerr;
> + die "$dev is not a valid device path\n";
> + }
> +
> + return $dev;
> +}
> +
> +my $dev_desc = {
> + path => {
> + optional => 1,
> + type => 'string',
> + default_key => 1,
> + format => 'pve-lxc-dev-string',
> + format_description => 'Path',
> + description => 'Device to pass through to the container',
> + verbose_description => 'Path to the device to pass through to the container',
> + },
> + mode => {
> + optional => 1,
> + type => 'integer',
> + description => 'Access mode (in octal) to be set on the device node',
> + },
> + uid => {
> + optional => 1,
> + type => 'integer',
> + description => 'User ID to be assigned to the device node',
> + },
> + gid => {
> + optional => 1,
> + type => 'integer',
> + description => 'Group ID to be assigned to the device node',
> + },
> +};
> +
> +for (my $i = 0; $i < $MAX_DEVICES; $i++) {
> + $confdesc->{"dev$i"} = {
> + optional => 1,
> + type => 'string', format => $dev_desc,
> + description => "Device to pass through to the container",
> + }
> +}
> +
> sub parse_pct_config {
> my ($filename, $raw, $strict) = @_;
>
> @@ -1255,6 +1307,21 @@ sub parse_volume {
> return;
> }
>
> +sub parse_device {
> + my ($class, $device_string, $noerr) = @_;
> +
> + my $res;
> + eval { $res = PVE::JSONSchema::parse_property_string($dev_desc, $device_string) };
> + if ($@) {
> + return undef if $noerr;
> + die $@;
> + }
> +
> + die "Path has to be defined" unless (defined($res->{path}));
> +
> + return $res;
> +}
> +
> sub print_volume {
> my ($class, $key, $volume) = @_;
>
> @@ -1762,4 +1829,16 @@ sub get_derived_property {
> }
> }
>
> +sub foreach_passthrough_device {
> + my ($class, $conf, $func, @param) = @_;
> +
> + foreach my $key (keys %$conf) {
> + next if $key !~ m/^dev(\d+)$/;
> +
> + my $device = $class->parse_device($conf->{$key});
> +
> + $func->($key, $device, @param);
> + }
> +}
> +
> 1;
> diff --git a/src/PVE/LXC/Tools.pm b/src/PVE/LXC/Tools.pm
> index 62cdbc1..c9fb834 100644
> --- a/src/PVE/LXC/Tools.pm
> +++ b/src/PVE/LXC/Tools.pm
> @@ -81,10 +81,9 @@ sub lxc_hook($$&) {
> $code->($ct_name, $common_vars, $namespaces, $args);
> }
>
> -sub for_current_devices($&) {
> - my ($vmid, $code) = @_;
> +sub for_devices {
> + my ($devlist_file, $vmid, $code) = @_;
>
> - my $devlist_file = "/var/lib/lxc/$vmid/devices";
> my $fd;
>
> if (! open $fd, '<', $devlist_file) {
> @@ -93,8 +92,8 @@ sub for_current_devices($&) {
> }
>
> while (defined(my $line = <$fd>)) {
> - if ($line !~ m@^(b):(\d+):(\d+):/dev/(\S+)\s*$@) {
> - warn "invalid .pve-devices entry: $line\n";
> + if ($line !~ m@^(b|c):(\d+):(\d+):/dev/(\S+)\s*$@) {
> + warn "invalid $devlist_file entry: $line\n";
> next;
> }
>
> @@ -117,6 +116,20 @@ sub for_current_devices($&) {
> close $fd;
> }
>
> +sub for_current_devices($&) {
> + my ($vmid, $code) = @_;
> +
> + my $devlist_file = "/var/lib/lxc/$vmid/devices";
> + for_devices($devlist_file, $vmid, $code);
> +}
> +
> +sub for_passthrough_devices($&) {
> + my ($vmid, $code) = @_;
> +
> + my $passthrough_devlist_file = "/var/lib/lxc/$vmid/passthrough_devices";
> + for_devices($passthrough_devlist_file, $vmid, $code);
> +}
> +
> sub cgroup_do_write($$) {
> my ($path, $value) = @_;
> my $fd;
> diff --git a/src/lxc-pve-autodev-hook b/src/lxc-pve-autodev-hook
> index 3c45949..cd2b92a 100755
> --- a/src/lxc-pve-autodev-hook
> +++ b/src/lxc-pve-autodev-hook
> @@ -3,8 +3,9 @@
> use strict;
> use warnings;
>
> -use File::Path;
> use File::Basename;
> +use File::Path;
> +use File::Touch;
>
> use PVE::LXC::Tools;
> use PVE::Tools;
> @@ -14,6 +15,17 @@ PVE::LXC::Tools::lxc_hook('autodev', 'lxc', sub {
>
> my $root = $vars->{ROOTFS_MOUNT};
>
> + PVE::LXC::Tools::for_passthrough_devices($vmid, sub {
> + my ($type, $major, $minor, $dev) = @_;
> +
> + my $rel_devpath = "/dev/$dev";
> + my $rel_dir = dirname($rel_devpath);
> + File::Path::mkpath("$root/$rel_dir");
> + touch("$root/dev/$dev");
^ Hint: `touch` is not a syscall. This does an `utimensat()` to update
the file mtimes. This isn't really necessary, and an easy way to just
create a file and do nothing if it already exists is to just use mknod
with S_IFREG for the file type in the mode bits and zero for the device
type:
PVE::Tools::mknod("$root/dev/$dev", S_IFREG, 0);
> +
> + PVE::Tools::mount("/var/lib/lxc/$vmid/passthrough/dev/$dev", "$root/dev/$dev", 0, 4096, 0);
Don't use magic numbers. Please place the MS_BIND constant in PVE::Tools
instead.
Also die() if mount fails.
> + });
> +
> PVE::LXC::Tools::for_current_devices($vmid, sub {
> my ($type, $major, $minor, $dev) = @_;
>
> diff --git a/src/lxc-pve-prestart-hook b/src/lxc-pve-prestart-hook
> index 936d0bf..68c7cec 100755
> --- a/src/lxc-pve-prestart-hook
> +++ b/src/lxc-pve-prestart-hook
> @@ -6,6 +6,7 @@ use strict;
> use warnings;
>
> use Fcntl qw(O_DIRECTORY :mode);
> +use File::Basename;
> use File::Path;
> use POSIX;
>
> @@ -118,6 +119,55 @@ PVE::LXC::Tools::lxc_hook('pre-start', 'lxc', sub {
>
> PVE::LXC::Config->foreach_volume($conf, $setup_mountpoint);
>
> + # Device passthrough
> + my $passthrough_devlist_file = "/var/lib/lxc/$vmid/passthrough_devices";
> + unlink $passthrough_devlist_file;
> + my $passthrough_devices = [];
> +
> + my $passthrough_dir = "/var/lib/lxc/$vmid/passthrough";
> + File::Path::make_path($passthrough_dir);
> + PVE::Tools::mount("none", $passthrough_dir, "tmpfs", 0, "size=8k");
^ checking that `mount` succeeded is particularly important here
> +
> + my $setup_passthrough_device = sub {
> + my ($key, $device) = @_;
> +
> + my $absolute_path = $device->{path};
> + my ($mode, $rdev) = (stat($absolute_path))[2, 6];
> +
> + die "Could not get mode of device $absolute_path\n"
> + if $mode !~ /^([\d]+)$/;
> + $mode = $1;
> +
> + die "Could not get device ID of $absolute_path\n"
> + if $rdev !~ /^([\d]+)$/;
> + $rdev = $1;
^ As above for the 2 checks with the stat() returned values.
> +
> + my $passthrough_device_path = "$passthrough_dir$absolute_path";
^ The above concatenation would probably be more readable with `.`
instead of quotes ($passthrough_dir . $absolute_path), or with `{}`
around the names.
> +
> + die "passthrough device path is invalid\n"
> + if $passthrough_device_path !~ /^([\w\/]+)$/;
> + $passthrough_device_path = $1;
^ Why this check? Both portions should be fine - $passthrough_dir is
trivial and $absolute_path comes from the parse function after
verification (and is already used in `stat()` so definitely contains a
valid path we also already used.
> +
> + File::Path::make_path(dirname($passthrough_device_path));
> + PVE::Tools::mknod($passthrough_device_path, $mode, $rdev);
^ `mknod` should be checked for errors.
> +
> + # Use chmod because umask could mess with the access mode on mknod
> + my $passthrough_mode = 0660;
> + $passthrough_mode = oct($device->{mode}) if (defined($device->{mode}));
> + chmod $passthrough_mode, $passthrough_device_path;
^ should be checked for errors.
> +
> + # Set uid and gid of the device node
> + my $uid = $rootuid;
> + my $gid = $rootgid;
> + $uid += $device->{uid} if (defined($device->{uid}));
> + $gid += $device->{gid} if (defined($device->{gid}));
^ id mappings can constist of multiple ranges.
You get the mapping from `parse_id_maps` (the 1st return value in the
line fetching `$root*id`).
It's an array of tuples of the form:
[ "g" or "u", <ns id>, <host id>, <length> ]
Make a helper to map ids using that array (see [1]).
$device->{*id} is from the perspective of the container and you want to
map from that to the host.
[1] https://git.proxmox.com/?p=pve-lxc-syscalld.git;a=blob;f=src/process/id_map.rs;h=d61d489da7af7418908fd8d85f1660c435b7c73e;hb=refs/heads/master#l26
> + chown $uid, $gid, $passthrough_device_path;
^ check for errors
> +
> + push @$passthrough_devices, $absolute_path;
push @$passthrough_devices, [$absolute_path, $mode, $rdev];
to avoid the extra stat below...
> + };
> +
> + PVE::LXC::Config->foreach_passthrough_device($conf, $setup_passthrough_device);
> +
> my $lxc_setup = PVE::LXC::Setup->new($conf, $rootdir);
> $lxc_setup->pre_start_hook();
>
> @@ -140,6 +190,19 @@ PVE::LXC::Tools::lxc_hook('pre-start', 'lxc', sub {
> }
> PVE::Tools::file_set_contents($devlist_file, $devlist);
> }
> +
> + if (@$passthrough_devices) {
> + my $devlist = '';
> + foreach my $dev (@$passthrough_devices) {
> + my ($mode, $rdev) = (stat($dev))[2, 6];
> + next if !$mode || !$rdev;
...and then resolve the tuple via:
($dev, my $mode, my $rdev) = @$dev;
> + my $major = PVE::Tools::dev_t_major($rdev);
> + my $minor = PVE::Tools::dev_t_minor($rdev);
> + my $device_type_char = S_ISBLK($mode) ? 'b' : 'c';
> + $devlist .= "$device_type_char:$major:$minor:$dev\n";
> + }
> + PVE::Tools::file_set_contents($passthrough_devlist_file, $devlist);
> + }
> });
>
> # Leftover cgroups prevent lxc from starting without any useful information
> --
> 2.39.2
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