123 lines
3.6 KiB
Go
123 lines
3.6 KiB
Go
//go:build !windows
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/*
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Copyright The containerd Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package client
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import (
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"context"
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"fmt"
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"github.com/containerd/containerd/v2/core/snapshots"
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)
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const (
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capaRemapIDs = "remap-ids"
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capaOnlyRemapIds = "only-remap-ids"
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)
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// WithRemapperLabels creates the labels used by any supporting snapshotter
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// to shift the filesystem ownership (user namespace mapping) automatically; currently
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// supported by the fuse-overlayfs and overlay snapshotters
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func WithRemapperLabels(ctrUID, hostUID, ctrGID, hostGID, length uint32) snapshots.Opt {
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return snapshots.WithLabels(map[string]string{
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snapshots.LabelSnapshotUIDMapping: fmt.Sprintf("%d:%d:%d", ctrUID, hostUID, length),
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snapshots.LabelSnapshotGIDMapping: fmt.Sprintf("%d:%d:%d", ctrGID, hostGID, length)})
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}
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func resolveSnapshotOptions(ctx context.Context, client *Client, snapshotterName string, snapshotter snapshots.Snapshotter, parent string, opts ...snapshots.Opt) (string, error) {
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capabs, err := client.GetSnapshotterCapabilities(ctx, snapshotterName)
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if err != nil {
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return "", err
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}
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for _, capab := range capabs {
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if capab == capaRemapIDs {
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// Snapshotter supports ID remapping, we don't need to do anything.
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return parent, nil
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}
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}
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var local snapshots.Info
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for _, opt := range opts {
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opt(&local)
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}
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needsRemap := false
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var uidMap, gidMap string
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if value, ok := local.Labels[snapshots.LabelSnapshotUIDMapping]; ok {
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needsRemap = true
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uidMap = value
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}
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if value, ok := local.Labels[snapshots.LabelSnapshotGIDMapping]; ok {
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needsRemap = true
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gidMap = value
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}
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if !needsRemap {
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return parent, nil
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}
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capaOnlyRemap := false
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for _, capa := range capabs {
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if capa == capaOnlyRemapIds {
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capaOnlyRemap = true
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}
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}
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if capaOnlyRemap {
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return "", fmt.Errorf("snapshotter %q doesn't support idmap mounts on this host, configure `slow_chown` to allow a slower and expensive fallback", snapshotterName)
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}
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var ctrUID, hostUID, length uint32
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_, err = fmt.Sscanf(uidMap, "%d:%d:%d", &ctrUID, &hostUID, &length)
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if err != nil {
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return "", fmt.Errorf("uidMap unparsable: %w", err)
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}
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var ctrGID, hostGID, lengthGID uint32
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_, err = fmt.Sscanf(gidMap, "%d:%d:%d", &ctrGID, &hostGID, &lengthGID)
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if err != nil {
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return "", fmt.Errorf("gidMap unparsable: %w", err)
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}
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if ctrUID != 0 || ctrGID != 0 {
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return "", fmt.Errorf("Container UID/GID of 0 only supported currently (%d/%d)", ctrUID, ctrGID)
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}
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// TODO(dgl): length isn't taken into account for the intermediate snapshot id.
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usernsID := fmt.Sprintf("%s-%d-%d", parent, hostUID, hostGID)
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if _, err := snapshotter.Stat(ctx, usernsID); err == nil {
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return usernsID, nil
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}
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mounts, err := snapshotter.Prepare(ctx, usernsID+"-remap", parent)
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if err != nil {
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return "", err
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}
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// TODO(dgl): length isn't taken into account here yet either.
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if err := remapRootFS(ctx, mounts, hostUID, hostGID); err != nil {
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snapshotter.Remove(ctx, usernsID+"-remap")
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return "", err
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}
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if err := snapshotter.Commit(ctx, usernsID, usernsID+"-remap"); err != nil {
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return "", err
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}
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return usernsID, nil
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}
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