Add SourceAddr support

api/handler/handler.go

@@ -161,6 +161,9 @@ type Host interface {
 	// FuncRemoveHeader with HeaderKindResponseTrailers. This panics if
 	// FeatureTrailers is not supported.
 	RemoveResponseTrailer(ctx context.Context, name string)
+
+	// GetSourceAddr supports the WebAssembly function export FuncGetSourceAddr.
+	GetSourceAddr(ctx context.Context) string
 }
 
 // eofReader is safer than reading from os.DevNull as it can never overrun
@@ -206,3 +209,4 @@ func (UnimplementedHost) GetResponseTrailerValues(context.Context, string) (valu
 func (UnimplementedHost) SetResponseTrailerValue(context.Context, string, string)            {}
 func (UnimplementedHost) AddResponseTrailerValue(context.Context, string, string)            {}
 func (UnimplementedHost) RemoveResponseTrailer(context.Context, string)                      {}
+func (UnimplementedHost) GetSourceAddr(context.Context) string                               { return "1.1.1.1:12345" }

api/handler/wasm.go

@@ -316,4 +316,10 @@ const (
 	//
 	// TODO: document on http-wasm-abi
 	FuncSetStatusCode = "set_status_code"
+
+	// FuncGetSourceAddr writes the SourceAddr to memory if it isn't larger than BufLimit.
+	// The result is its length in bytes. Ex. "1.1.1.1:12345" or "[fe80::101e:2bdf:8bfb:b97e]:12345"
+	//
+	// TODO: document on http-wasm-abi
+	FuncGetSourceAddr = "get_source_addr"
 )

handler/middleware.go

@@ -565,6 +565,17 @@ func (m *middleware) writeBody(ctx context.Context, mod wazeroapi.Module, params
 	writeBody(mod, buf, bufLen, w)
 }
 
+// getSourceAddr implements the WebAssembly host function handler.FuncGetSourceAddr.
+func (m *middleware) getSourceAddr(ctx context.Context, mod wazeroapi.Module, stack []uint64) {
+	buf := uint32(stack[0])
+	bufLimit := handler.BufLimit(stack[1])
+
+	method := m.host.GetSourceAddr(ctx)
+	methodLen := writeStringIfUnderLimit(mod.Memory(), buf, bufLimit, method)
+
+	stack[0] = uint64(methodLen)
+}
+
 func writeBody(mod wazeroapi.Module, buf, bufLen uint32, w io.Writer) {
 	// buf_len 0 means to overwrite with nothing
 	var b []byte
@@ -694,6 +705,9 @@ func (m *middleware) instantiateHost(ctx context.Context) (wazeroapi.Module, err
 		WithGoModuleFunction(wazeroapi.GoModuleFunc(m.writeBody), []wazeroapi.ValueType{i32, i32, i32}, []wazeroapi.ValueType{}).
 		WithParameterNames("kind", "body", "body_len").Export(handler.FuncWriteBody).
 		NewFunctionBuilder().
+		WithGoModuleFunction(wazeroapi.GoModuleFunc(m.getSourceAddr), []wazeroapi.ValueType{i32, i32}, []wazeroapi.ValueType{i32}).
+		WithParameterNames("buf", "buf_limit").Export(handler.FuncGetSourceAddr).
+		NewFunctionBuilder().
 		WithGoFunction(wazeroapi.GoFunc(m.getStatusCode), []wazeroapi.ValueType{}, []wazeroapi.ValueType{i32}).
 		WithParameterNames().Export(handler.FuncGetStatusCode).
 		NewFunctionBuilder().

handler/nethttp/host.go

@@ -346,3 +346,9 @@ func addTrailer(header http.Header, name string, value string) {
 func removeTrailer(header http.Header, name string) {
 	header.Del(http.TrailerPrefix + name)
 }
+
+// GetSourceAddr implements the same method as documented on handler.Host.
+func (host) GetSourceAddr(ctx context.Context) string {
+	r := requestStateFromContext(ctx).r
+	return r.RemoteAddr
+}