super basic wasm filter implementation using wazero

filters/builtin/builtin.go

@@ -21,6 +21,7 @@ import (
 	"github.com/zalando/skipper/filters/tee"
 	"github.com/zalando/skipper/filters/tls"
 	"github.com/zalando/skipper/filters/tracing"
+	"github.com/zalando/skipper/filters/wasm"
 	"github.com/zalando/skipper/filters/xforward"
 	"github.com/zalando/skipper/script"
 )
@@ -230,6 +231,7 @@ func Filters() []filters.Spec {
 		consistenthash.NewConsistentHashKey(),
 		consistenthash.NewConsistentHashBalanceFactor(),
 		tls.New(),
+		wasm.NewWASM(),
 	}
 }
 

filters/filters.go

@@ -352,6 +352,7 @@ const (
 	OpaServeResponseName                       = "opaServeResponse"
 	OpaServeResponseWithReqBodyName            = "opaServeResponseWithReqBody"
 	TLSName                                    = "tlsPassClientCertificates"
+	WASMName                                   = "wasm"
 
 	// Undocumented filters
 	HealthCheckName        = "healthcheck"

filters/wasm/testdata/add.go

@@ -0,0 +1,15 @@
+package main
+
+//export request
+func request(x, y uint32) uint32 {
+	return x + y
+}
+
+//export response
+func response(x, y uint32) uint32 {
+	return x - y
+}
+
+// main is required for the `wasi` target, even if it isn't used.
+// See https://wazero.io/languages/tinygo/#why-do-i-have-to-define-main
+func main() {}

filters/wasm/wasm.go

@@ -0,0 +1,104 @@
+package wasm
+
+import (
+	"context"
+	"net/url"
+	"os"
+
+	"github.com/sirupsen/logrus"
+	"github.com/tetratelabs/wazero"
+	"github.com/tetratelabs/wazero/api"
+	"github.com/tetratelabs/wazero/imports/wasi_snapshot_preview1"
+	"github.com/zalando/skipper/filters"
+)
+
+type wasmSpec struct{}
+
+type wasm struct {
+	code     []byte
+	mod      api.Module
+	request  api.Function
+	response api.Function
+}
+
+func NewWASM() filters.Spec {
+	return &wasmSpec{}
+}
+
+// Name implements filters.Spec.
+func (*wasmSpec) Name() string {
+	return filters.WASMName
+}
+
+// CreateFilter implements filters.Spec.
+func (*wasmSpec) CreateFilter(args []interface{}) (filters.Filter, error) {
+	if len(args) != 1 {
+		return nil, filters.ErrInvalidFilterParameters
+	}
+	src, ok := args[0].(string)
+	if !ok {
+		return nil, filters.ErrInvalidFilterParameters
+	}
+	u, err := url.Parse(src)
+	if err != nil {
+		return nil, filters.ErrInvalidFilterParameters
+	}
+
+	var code []byte
+
+	switch u.Scheme {
+	case "file":
+		code, err = os.ReadFile(u.Path)
+		if err != nil {
+			logrus.Errorf("Failed to load file %q: %v", u.Path, err)
+			return nil, filters.ErrInvalidFilterParameters
+		}
+	case "https":
+		panic("not implemented")
+	default:
+		return nil, filters.ErrInvalidFilterParameters
+	}
+
+	ctx := context.Background()
+	r := wazero.NewRuntime(ctx) // TODO: needs r.Close()
+	// Instantiate WASI, which implements host functions needed for TinyGo to
+	// implement `panic`.
+	wasi_snapshot_preview1.MustInstantiate(ctx, r)
+
+	// Instantiate the guest Wasm into the same runtime. It exports the `add`
+	// function, implemented in WebAssembly.
+	mod, err := r.Instantiate(ctx, code)
+	if err != nil {
+		logrus.Fatalf("failed to instantiate module: %v", err)
+	}
+	request := mod.ExportedFunction("request")
+	response := mod.ExportedFunction("response")
+
+	return &wasm{
+		code:     code,
+		mod:      mod,
+		request:  request,
+		response: response,
+	}, nil
+}
+
+// Request implements filters.Filter.
+func (w *wasm) Request(filters.FilterContext) {
+
+	result, err := w.request.Call(context.Background(), 2, 3)
+	if err != nil {
+		logrus.Errorf("failed to call add: %v", err)
+	}
+	logrus.Infof("request result: %v", result)
+
+}
+
+// Response implements filters.Filter.
+func (w *wasm) Response(filters.FilterContext) {
+	result, err := w.response.Call(context.Background(), 3, 2)
+	if err != nil {
+		logrus.Errorf("failed to call add: %v", err)
+	}
+	logrus.Infof("response result: %v", result)
+
+}

go.mod

@@ -146,6 +146,7 @@ require (
 	github.com/shoenig/go-m1cpu v0.1.6 // indirect
 	github.com/streadway/quantile v0.0.0-20220407130108-4246515d968d // indirect
 	github.com/tchap/go-patricia/v2 v2.3.1 // indirect
+	github.com/tetratelabs/wazero v1.6.0 // indirect
 	github.com/tidwall/match v1.1.1 // indirect
 	github.com/tidwall/pretty v1.2.0 // indirect
 	github.com/tklauser/go-sysconf v0.3.12 // indirect

go.sum

@@ -407,6 +407,8 @@ github.com/tchap/go-patricia/v2 v2.3.1 h1:6rQp39lgIYZ+MHmdEq4xzuk1t7OdC35z/xm0BG
 github.com/tchap/go-patricia/v2 v2.3.1/go.mod h1:VZRHKAb53DLaG+nA9EaYYiaEx6YztwDlLElMsnSHD4k=
 github.com/testcontainers/testcontainers-go v0.27.0 h1:IeIrJN4twonTDuMuBNQdKZ+K97yd7VrmNGu+lDpYcDk=
 github.com/testcontainers/testcontainers-go v0.27.0/go.mod h1:+HgYZcd17GshBUZv9b+jKFJ198heWPQq3KQIp2+N+7U=
+github.com/tetratelabs/wazero v1.6.0 h1:z0H1iikCdP8t+q341xqepY4EWvHEw8Es7tlqiVzlP3g=
+github.com/tetratelabs/wazero v1.6.0/go.mod h1:0U0G41+ochRKoPKCJlh0jMg1CHkyfK8kDqiirMmKY8A=
 github.com/tidwall/gjson v1.17.0 h1:/Jocvlh98kcTfpN2+JzGQWQcqrPQwDrVEMApx/M5ZwM=
 github.com/tidwall/gjson v1.17.0/go.mod h1:/wbyibRr2FHMks5tjHJ5F8dMZh3AcwJEMf5vlfC0lxk=
 github.com/tidwall/match v1.1.1 h1:+Ho715JplO36QYgwN9PGYNhgZvoUSc9X2c80KVTi+GA=