hst/fsbind: optional autoetc behaviour

This generalises the special field allowing any special behaviour to be matched from target.

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

cmd/hakurei/print_test.go

@@ -284,7 +284,7 @@ App
           "dst": "/",
           "src": "/var/lib/hakurei/base/org.debian",
           "write": true,
-          "autoroot": true
+          "special": true
         },
         {
           "type": "ephemeral",
@@ -438,7 +438,7 @@ App
         "dst": "/",
         "src": "/var/lib/hakurei/base/org.debian",
         "write": true,
-        "autoroot": true
+        "special": true
       },
       {
         "type": "ephemeral",
@@ -646,7 +646,7 @@ func Test_printPs(t *testing.T) {
             "dst": "/",
             "src": "/var/lib/hakurei/base/org.debian",
             "write": true,
-            "autoroot": true
+            "special": true
           },
           {
             "type": "ephemeral",

hst/fs.go

@@ -18,11 +18,19 @@ type FilesystemConfig interface {
 	// Host returns a slice of all host paths used by this operation.
 	Host() []*container.Absolute
 	// Apply appends the [container.Op] implementing this operation.
-	Apply(ops *container.Ops)
+	Apply(z *ApplyState)
 
 	fmt.Stringer
 }
 
+// ApplyState holds the address of [container.Ops] and any relevant application state.
+type ApplyState struct {
+	// AutoEtcPrefix is the prefix for [container.AutoEtcOp].
+	AutoEtcPrefix string
+
+	*container.Ops
+}
+
 var (
 	ErrFSNull = errors.New("unexpected null in mount point")
 )

hst/fs_test.go

@@ -209,7 +209,7 @@ type stubFS struct {
 func (s stubFS) Valid() bool                 { return false }
 func (s stubFS) Path() *container.Absolute   { panic("unreachable") }
 func (s stubFS) Host() []*container.Absolute { panic("unreachable") }
-func (s stubFS) Apply(*container.Ops)        { panic("unreachable") }
+func (s stubFS) Apply(*hst.ApplyState)       { panic("unreachable") }
 func (s stubFS) String() string              { return "<invalid " + s.typeName + ">" }
 
 type sCheck struct {
@@ -238,7 +238,7 @@ func checkFs(t *testing.T, testCases []fsTestCase) {
 
 			t.Run("ops", func(t *testing.T) {
 				ops := new(container.Ops)
-				tc.fs.Apply(ops)
+				tc.fs.Apply(&hst.ApplyState{AutoEtcPrefix: ":3", Ops: ops})
 				if !reflect.DeepEqual(ops, &tc.ops) {
 					gotString := new(strings.Builder)
 					for _, op := range *ops {

hst/fsbind.go

@@ -25,17 +25,38 @@ type FSBind struct {
 	// skip this mount point if the host path does not exist
 	Optional bool `json:"optional,omitempty"`
 
-	// enable autoroot behaviour;
-	// this requires Target to be [container.AbsFHSRoot].
-	AutoRoot bool `json:"autoroot,omitempty"`
+	// enable special behaviour:
+	// for autoroot, Target must be set to [container.AbsFHSRoot];
+	// for autoetc, Target must be set to [container.AbsFHSEtc]
+	Special bool `json:"special,omitempty"`
+}
+
+// IsAutoRoot returns whether this FSBind has autoroot behaviour enabled.
+func (b *FSBind) IsAutoRoot() bool {
+	return b.Valid() && b.Special && b.Target.String() == container.FHSRoot
+}
+
+// IsAutoEtc returns whether this FSBind has autoetc behaviour enabled.
+func (b *FSBind) IsAutoEtc() bool {
+	return b.Valid() && b.Special && b.Target.String() == container.FHSEtc
 }
 
 func (b *FSBind) Valid() bool {
 	if b == nil || b.Source == nil {
 		return false
 	}
-	if b.AutoRoot && (b.Target == nil || b.Target.String() != container.FHSRoot) {
+	if b.Special {
+		if b.Target == nil {
 			return false
+		} else {
+			switch b.Target.String() {
+			case container.FHSRoot, container.FHSEtc:
+				break
+
+			default:
+				return false
+			}
+		}
 	}
 	return true
 }
@@ -57,7 +78,7 @@ func (b *FSBind) Host() []*container.Absolute {
 	return []*container.Absolute{b.Source}
 }
 
-func (b *FSBind) Apply(ops *container.Ops) {
+func (b *FSBind) Apply(z *ApplyState) {
 	if !b.Valid() {
 		return
 	}
@@ -77,10 +98,15 @@ func (b *FSBind) Apply(ops *container.Ops) {
 		flags |= container.BindOptional
 	}
 
-	if !b.AutoRoot {
-		ops.Bind(b.Source, target, flags)
-	} else {
-		ops.Root(b.Source, flags)
+	switch {
+	case b.IsAutoRoot():
+		z.Root(b.Source, flags)
+
+	case b.IsAutoEtc():
+		z.Etc(b.Source, z.AutoEtcPrefix)
+
+	default:
+		z.Bind(b.Source, target, flags)
 	}
 }
 
@@ -96,7 +122,9 @@ func (b *FSBind) String() string {
 		flagSym = "w"
 	}
 
-	if b.AutoRoot {
+	if b.Special {
+		switch {
+		case b.IsAutoRoot():
 			prefix := "autoroot"
 			if flagSym != "" {
 				prefix += ":" + flagSym
@@ -105,6 +133,10 @@ func (b *FSBind) String() string {
 				return prefix + ":" + b.Source.String()
 			}
 			return prefix
+
+		case b.IsAutoEtc():
+			return "autoetc:" + b.Source.String()
+		}
 	}
 
 	g := 4 + len(b.Source.String())

hst/fsbind_test.go

@@ -63,22 +63,22 @@ func TestFSBind(t *testing.T) {
 		}}, m("/"), ms("/"),
 			"*/"},
 
-		{"autoroot nil target", &hst.FSBind{
+		{"special nil target", &hst.FSBind{
 			Source:  m("/"),
-			AutoRoot: true,
+			Special: true,
 		}, false, nil, nil, nil, "<invalid>"},
 
-		{"autoroot bad target", &hst.FSBind{
+		{"special bad target", &hst.FSBind{
 			Source:  m("/"),
-			Target:   m("/etc/"),
-			AutoRoot: true,
+			Target:  m("/var/"),
+			Special: true,
 		}, false, nil, nil, nil, "<invalid>"},
 
 		{"autoroot pd", &hst.FSBind{
 			Target:  m("/"),
 			Source:  m("/"),
 			Write:   true,
-			AutoRoot: true,
+			Special: true,
 		}, true, container.Ops{&container.AutoRootOp{
 			Host:  m("/"),
 			Flags: container.BindWritable,
@@ -88,10 +88,20 @@ func TestFSBind(t *testing.T) {
 			Target:  m("/"),
 			Source:  m("/etc"),
 			Write:   true,
-			AutoRoot: true,
+			Special: true,
 		}, true, container.Ops{&container.AutoRootOp{
 			Host:  m("/etc"),
 			Flags: container.BindWritable,
 		}}, m("/"), ms("/etc"), "autoroot:w:/etc"},
+
+		{"autoetc", &hst.FSBind{
+			Target:  m("/etc/"),
+			Source:  m("/etc/"),
+			Special: true,
+		}, true, container.Ops{
+			&container.MkdirOp{Path: m("/etc/"), Perm: 0755},
+			&container.BindMountOp{Source: m("/etc/"), Target: m("/etc/.host/:3")},
+			&container.AutoEtcOp{Prefix: ":3"},
+		}, m("/etc/"), ms("/etc/"), "autoetc:/etc/"},
 	})
 }

hst/fsephemeral.go

@@ -38,7 +38,7 @@ func (e *FSEphemeral) Host() []*container.Absolute { return nil }
 
 const fsEphemeralDefaultPerm = os.FileMode(0755)
 
-func (e *FSEphemeral) Apply(ops *container.Ops) {
+func (e *FSEphemeral) Apply(z *ApplyState) {
 	if !e.Valid() {
 		return
 	}
@@ -54,9 +54,9 @@ func (e *FSEphemeral) Apply(ops *container.Ops) {
 	}
 
 	if e.Write {
-		ops.Tmpfs(e.Target, size, perm)
+		z.Tmpfs(e.Target, size, perm)
 	} else {
-		ops.Readonly(e.Target, perm)
+		z.Readonly(e.Target, perm)
 	}
 }
 

hst/fsoverlay.go

@@ -62,15 +62,15 @@ func (o *FSOverlay) Host() []*container.Absolute {
 	return p
 }
 
-func (o *FSOverlay) Apply(op *container.Ops) {
+func (o *FSOverlay) Apply(z *ApplyState) {
 	if !o.Valid() {
 		return
 	}
 
 	if o.Upper != nil && o.Work != nil { // rw
-		op.Overlay(o.Target, o.Upper, o.Work, o.Lower...)
+		z.Overlay(o.Target, o.Upper, o.Work, o.Lower...)
 	} else { // ro
-		op.OverlayReadonly(o.Target, o.Lower...)
+		z.OverlayReadonly(o.Target, o.Lower...)
 	}
 }
 

hst/hst_test.go

@@ -107,7 +107,7 @@ func TestTemplate(t *testing.T) {
 				"dst": "/",
 				"src": "/var/lib/hakurei/base/org.debian",
 				"write": true,
-				"autoroot": true
+				"special": true
 			},
 			{
 				"type": "ephemeral",

internal/app/container_linux.go

@@ -40,9 +40,13 @@ func newContainer(s *hst.ContainerConfig, os sys.State, prefix string, uid, gid
 		ForwardCancel: s.WaitDelay >= 0,
 	}
 
+	as := &hst.ApplyState{
+		AutoEtcPrefix: prefix,
+	}
 	{
 		ops := make(container.Ops, 0, preallocateOpsCount+len(s.Filesystem)+len(s.Link))
 		params.Ops = &ops
+		as.Ops = &ops
 	}
 
 	if s.Multiarch {
@@ -81,10 +85,10 @@ func newContainer(s *hst.ContainerConfig, os sys.State, prefix string, uid, gid
 		// if the first element targets /, it is inserted early and excluded from path hiding
 		rootfs := filesystem[0].FilesystemConfig
 		filesystem = filesystem[1:]
-		rootfs.Apply(params.Ops)
+		rootfs.Apply(as)
 
 		// autoroot requires special handling during path hiding
-		if b, ok := rootfs.(*hst.FSBind); ok && b.Valid() && b.AutoRoot {
+		if b, ok := rootfs.(*hst.FSBind); ok && b.IsAutoRoot() {
 			autoroot = b
 		}
 	}
@@ -143,7 +147,7 @@ func newContainer(s *hst.ContainerConfig, os sys.State, prefix string, uid, gid
 		if !c.Valid() {
 			return nil, nil, fmt.Errorf("invalid filesystem at index %d", i)
 		}
-		c.Apply(params.Ops)
+		c.Apply(as)
 
 		// fs counter
 		hidePathSourceCount += len(c.Host())

internal/app/seal_linux.go

@@ -249,7 +249,7 @@ func (seal *outcome) finalise(ctx context.Context, sys sys.State, config *hst.Co
 					Target:  container.AbsFHSRoot,
 					Source:  container.AbsFHSRoot,
 					Write:   true,
-					AutoRoot: true,
+					Special: true,
 				}},
 			},
 		}