Implement autodetection of Windows buildkitd socket

Buildkit on Windows doesn't support rootless mode, and doesn't put the
namespace into the pipe name currently, so the Windows version is
near-trivial.

This also corrects the autodetection path on FreeBSD to start in
/var/run instead of current Linux FHS's /run, and doesn't bother trying
to support Rootless mode and related path guessing on FreeBSD.

Signed-off-by: Paul "TBBle" Hampson <[email protected]>

pkg/buildkitutil/buildkitutil.go

@@ -57,28 +57,14 @@ func BuildctlBaseArgs(buildkitHost string) []string {
 }
 
 func GetBuildkitHost(namespace string) (string, error) {
- if namespace == "" {
- return "", fmt.Errorf("namespace must be specified")
- }
- // Try candidate locations of the current containerd namespace.
- run := "/run/"
- if rootlessutil.IsRootless() {
- var err error
- run, err = rootlessutil.XDGRuntimeDir()
- if err != nil {
- log.L.Warn(err)
- run = fmt.Sprintf("/run/user/%d", rootlessutil.ParentEUID())
- }
- }
- var hostRel []string
- if namespace != "default" {
- hostRel = append(hostRel, fmt.Sprintf("buildkit-%s/buildkitd.sock", namespace))
+ paths, err := getBuildkitHostCandidates(namespace)
+ if err != nil {
+ return "", err
  }
- hostRel = append(hostRel, "buildkit-default/buildkitd.sock", "buildkit/buildkitd.sock")
+
  var errs []error //nolint:prealloc
- for _, p := range hostRel {
- log.L.Debugf("Choosing the buildkit host %q, candidates=%v (in %q)", p, hostRel, run)
- buildkitHost := "unix://" + filepath.Join(run, p)
+ for _, buildkitHost := range paths {
+ log.L.Debugf("Choosing the buildkit host %q, candidates=%v", buildkitHost, paths)
  _, err := pingBKDaemon(buildkitHost)
  if err == nil {
  log.L.Debugf("Chosen buildkit host %q", buildkitHost)
@@ -88,7 +74,7 @@ func GetBuildkitHost(namespace string) (string, error) {
  }
  allErr := errors.Join(errs...)
  log.L.WithError(allErr).Error(getHint())
- return "", fmt.Errorf("no buildkit host is available, tried %d candidates: %w", len(hostRel), allErr)
+ return "", fmt.Errorf("no buildkit host is available, tried %d candidates: %w", len(paths), allErr)
 }
 
 func GetWorkerLabels(buildkitHost string) (labels map[string]string, _ error) {

pkg/buildkitutil/buildkitutil_freebsd.go

@@ -0,0 +1,22 @@
+/*
+ Copyright The containerd Authors.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+package buildkitutil
+
+func getRuntimeVariableDataDir() string {
+ // Per hier(7) dated July 6, 2023.
+ return "/var/run"
+}

pkg/buildkitutil/buildkitutil_linux.go

@@ -0,0 +1,39 @@
+/*
+ Copyright The containerd Authors.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+package buildkitutil
+
+import (
+ "fmt"
+
+ "github.com/containerd/log"
+ "github.com/containerd/nerdctl/v2/pkg/rootlessutil"
+)
+
+func getRuntimeVariableDataDir() string {
+ // Per Linux Foundation "Filesystem Hierarchy Standard" version 3.0 section 3.15.
+ // Under version 2.3, this was "/var/run".
+ run := "/run"
+ if rootlessutil.IsRootless() {
+ var err error
+ run, err = rootlessutil.XDGRuntimeDir()
+ if err != nil {
+ log.L.Warn(err)
+ run = fmt.Sprintf("/run/user/%d", rootlessutil.ParentEUID())
+ }
+ }
+ return run
+}

pkg/buildkitutil/buildkitutil_unix.go

@@ -0,0 +1,39 @@
+//go:build freebsd || linux
+
+/*
+ Copyright The containerd Authors.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+package buildkitutil
+
+import (
+ "fmt"
+ "path/filepath"
+)
+
+func getBuildkitHostCandidates(namespace string) ([]string, error) {
+ if namespace == "" {
+ return []string{}, fmt.Errorf("namespace must be specified")
+ }
+ // Try candidate locations of the current containerd namespace.
+ run := getRuntimeVariableDataDir()
+ var candidates []string
+ if namespace != "default" {
+ candidates = append(candidates, "unix://"+filepath.Join(run, fmt.Sprintf("buildkit-%s/buildkitd.sock", namespace)))
+ }
+ candidates = append(candidates, "unix://"+filepath.Join(run, "buildkit-default/buildkitd.sock"), "unix://"+filepath.Join(run, "buildkit/buildkitd.sock"))
+
+ return candidates, nil
+}

pkg/buildkitutil/buildkitutil_windows.go

@@ -0,0 +1,21 @@
+/*
+ Copyright The containerd Authors.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+package buildkitutil
+
+func getBuildkitHostCandidates(namespace string) ([]string, error) {
+ return []string{"npipe:////./pipe/buildkitd"}, nil
+}