hst/container: optional runtime and tmpdir sharing

Sharing and persisting these directories do not always make sense. Make it optional here.

Closes #16.

Signed-off-by: Ophestra <cat@gensokyo.uk>

hst/container.go

@@ -63,6 +63,11 @@ const (
 	// FDevice mount /dev/ from the init mount namespace as-is in the container mount namespace.
 	FDevice
 
+	// FShareRuntime shares XDG_RUNTIME_DIR between containers under the same identity.
+	FShareRuntime
+	// FShareTmpdir shares TMPDIR between containers under the same identity.
+	FShareTmpdir
+
 	fMax
 
 	// FAll is [ContainerConfig.Flags] with all currently defined bits set.
@@ -133,6 +138,11 @@ type containerConfigJSON = struct {
 
 	// Corresponds to [FDevice].
 	Device bool `json:"device,omitempty"`
+
+	// Corresponds to [FShareRuntime].
+	ShareRuntime bool `json:"share_runtime,omitempty"`
+	// Corresponds to [FShareTmpdir]
+	ShareTmpdir bool `json:"share_tmpdir,omitempty"`
 }
 
 func (c *ContainerConfig) MarshalJSON() ([]byte, error) {
@@ -151,6 +161,8 @@ func (c *ContainerConfig) MarshalJSON() ([]byte, error) {
 		Multiarch:     c.Flags&FMultiarch != 0,
 		MapRealUID:    c.Flags&FMapRealUID != 0,
 		Device:        c.Flags&FDevice != 0,
+		ShareRuntime:  c.Flags&FShareRuntime != 0,
+		ShareTmpdir:   c.Flags&FShareTmpdir != 0,
 	})
 }
 
@@ -192,5 +204,11 @@ func (c *ContainerConfig) UnmarshalJSON(data []byte) error {
 	if v.Device {
 		c.Flags |= FDevice
 	}
+	if v.ShareRuntime {
+		c.Flags |= FShareRuntime
+	}
+	if v.ShareTmpdir {
+		c.Flags |= FShareTmpdir
+	}
 	return nil
 }

hst/container_test.go

@@ -28,7 +28,7 @@ func TestContainerConfig(t *testing.T) {
 		{"hostnet hostabstract mapuid", &hst.ContainerConfig{Flags: hst.FHostNet | hst.FHostAbstract | hst.FMapRealUID},
 			`{"env":null,"filesystem":null,"shell":null,"home":null,"args":null,"host_net":true,"host_abstract":true,"map_real_uid":true}`},
 		{"all", &hst.ContainerConfig{Flags: hst.FAll},
-			`{"env":null,"filesystem":null,"shell":null,"home":null,"args":null,"seccomp_compat":true,"devel":true,"userns":true,"host_net":true,"host_abstract":true,"tty":true,"multiarch":true,"map_real_uid":true,"device":true}`},
+			`{"env":null,"filesystem":null,"shell":null,"home":null,"args":null,"seccomp_compat":true,"devel":true,"userns":true,"host_net":true,"host_abstract":true,"tty":true,"multiarch":true,"map_real_uid":true,"device":true,"share_runtime":true,"share_tmpdir":true}`},
 	}
 
 	for _, tc := range testCases {

hst/hst_test.go

@@ -244,7 +244,9 @@ func TestTemplate(t *testing.T) {
 		"tty": true,
 		"multiarch": true,
 		"map_real_uid": true,
-		"device": true
+		"device": true,
+		"share_runtime": true,
+		"share_tmpdir": true
 	}
 }`