libpod: allow to configure path to the network-cmd binary

allow to configure the path to the network-cmd binary, either via an
option flag --network-cmd-path or through the libpod.conf
configuration file.

This is currently used to customize the path to the slirp4netns
binary.

Closes: https://github.com/containers/libpod/issues/2506

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

3 files changed, 25 insertions, 4 deletions

diff --git a/libpod/networking_linux.go b/libpod/networking_linux.go
index f9caf26d1..80d7d8213 100644
--- a/libpod/networking_linux.go
+++ b/libpod/networking_linux.go
@@ -139,10 +139,15 @@ func (r *Runtime) setupRootlessNetNS(ctr *Container) (err error) {
 	defer ctr.rootlessSlirpSyncR.Close()
 	defer ctr.rootlessSlirpSyncW.Close()
 
-	path, err := exec.LookPath("slirp4netns")
-	if err != nil {
-		logrus.Errorf("could not find slirp4netns, the network namespace won't be configured: %v", err)
-		return nil
+	path := r.config.NetworkCmdPath
+
+	if path == "" {
+		var err error
+		path, err = exec.LookPath("slirp4netns")
+		if err != nil {
+			logrus.Errorf("could not find slirp4netns, the network namespace won't be configured: %v", err)
+			return nil
+		}
 	}
 
 	syncR, syncW, err := os.Pipe()
diff --git a/libpod/options.go b/libpod/options.go
index 5ad2824d9..64b425c57 100644
--- a/libpod/options.go
+++ b/libpod/options.go
@@ -193,6 +193,20 @@ func WithConmonEnv(environment []string) RuntimeOption {
 	}
 }
 
+// WithNetworkCmdPath specifies the path to the slirp4netns binary which manages the
+// runtime.
+func WithNetworkCmdPath(path string) RuntimeOption {
+	return func(rt *Runtime) error {
+		if rt.valid {
+			return ErrRuntimeFinalized
+		}
+
+		rt.config.NetworkCmdPath = path
+
+		return nil
+	}
+}
+
 // WithCgroupManager specifies the manager implementation name which is used to
 // handle cgroups for containers.
 // Current valid values are "cgroupfs" and "systemd".
diff --git a/libpod/runtime.go b/libpod/runtime.go
index 9667abfe6..535b6f41b 100644
--- a/libpod/runtime.go
+++ b/libpod/runtime.go
@@ -217,6 +217,8 @@ type RuntimeConfig struct {
 	EnablePortReservation bool `toml:"enable_port_reservation"`
 	// EnableLabeling indicates wether libpod will support container labeling
 	EnableLabeling bool `toml:"label"`
+	// NetworkCmdPath is the path to the slirp4netns binary
+	NetworkCmdPath string `toml:"network_cmd_path"`
 
 	// NumLocks is the number of locks to make available for containers and
 	// pods.