Move the HostConfig portion of Inspect inside libpod

When we first began writing Podman, we ran into a major issue
when implementing Inspect. Libpod deliberately does not tie its
internal data structures to Docker, and stores most information
about containers encoded within the OCI spec. However, Podman
must present a CLI compatible with Docker, which means it must
expose all the information in 'docker inspect' - most of which is
not contained in the OCI spec or libpod's Config struct.

Our solution at the time was the create artifact. We JSON'd the
complete CreateConfig (a parsed form of the CLI arguments to
'podman run') and stored it with the container, restoring it when
we needed to run commands that required the extra info.

Over the past month, I've been looking more at Inspect, and
refactored large portions of it into Libpod - generating them
from what we know about the OCI config and libpod's (now much
expanded, versus previously) container configuration. This path
comes close to completing the process, moving the last part of
inspect into libpod and removing the need for the create
artifact.

This improves libpod's compatability with non-Podman containers.
We no longer require an arbitrarily-formatted JSON blob to be
present to run inspect.

Fixes: #3500

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

2 files changed, 55 insertions, 0 deletions

diff --git a/pkg/util/utils_linux.go b/pkg/util/utils_linux.go
index 47fa1031f..318bd2b1b 100644
--- a/pkg/util/utils_linux.go
+++ b/pkg/util/utils_linux.go
@@ -1,7 +1,14 @@
 package util
 
 import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"syscall"
+
 	"github.com/containers/psgo"
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
 )
 
 // GetContainerPidInformationDescriptors returns a string slice of all supported
@@ -9,3 +16,39 @@ import (
 func GetContainerPidInformationDescriptors() ([]string, error) {
 	return psgo.ListDescriptors(), nil
 }
+
+// FindDeviceNodes parses /dev/ into a set of major:minor -> path, where
+// [major:minor] is the device's major and minor numbers formatted as, for
+// example, 2:0 and path is the path to the device node.
+// Symlinks to nodes are ignored.
+func FindDeviceNodes() (map[string]string, error) {
+	nodes := make(map[string]string)
+	err := filepath.Walk("/dev", func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			logrus.Warnf("Error descending into path %s: %v", path, err)
+			return filepath.SkipDir
+		}
+
+		// If we aren't a device node, do nothing.
+		if info.Mode()&(os.ModeDevice|os.ModeCharDevice) == 0 {
+			return nil
+		}
+
+		// We are a device node. Get major/minor.
+		sysstat, ok := info.Sys().(*syscall.Stat_t)
+		if !ok {
+			return errors.Errorf("Could not convert stat output for use")
+		}
+		major := uint64(sysstat.Rdev / 256)
+		minor := uint64(sysstat.Rdev % 256)
+
+		nodes[fmt.Sprintf("%d:%d", major, minor)] = path
+
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return nodes, nil
+}
diff --git a/pkg/util/utils_unsupported.go b/pkg/util/utils_unsupported.go
new file mode 100644
index 000000000..62805d7c8
--- /dev/null
+++ b/pkg/util/utils_unsupported.go
@@ -0,0 +1,12 @@
+// +build darwin windows
+
+package util
+
+import (
+	"github.com/pkg/errors"
+)
+
+// FindDeviceNodes is not implemented anywhere except Linux.
+func FindDeviceNodes() (map[string]string, error) {
+	return nil, errors.Errorf("not supported on non-Linux OSes")
+}