go sdk: add accessor for destination address (#50)

This can be useful for WAF purposes (though it may be desirable as well
to get the ip from a header like XFF or the Envoy trusted IP).

---------

Signed-off-by: William Zhang <wtzhang23@gmail.com>

Author: wtzhang23

go/gosdk/abi.go

@@ -298,7 +298,8 @@ func envoy_dynamic_module_on_http_filter_http_callout_done(
 func envoy_dynamic_module_on_http_filter_scheduled(
 	filterEnvoyPtr uintptr,
 	filterModulePtr uintptr,
-	eventID C.uint64_t) {
+	eventID C.uint64_t,
+) {
 	pinned := unwrapPinnedHttpFilter(uintptr(filterModulePtr))
 	// Call the Scheduled method of the filter.
 	pinned.obj.Scheduled(envoyFilter{raw: uintptr(filterEnvoyPtr)}, uint64(eventID))
@@ -469,6 +470,12 @@ func (e envoyFilter) GetSourceAddress() string {
 	return e.getStringAttribute(24) // source.address
 }
 
+// GetDestinationAddress implements [EnvoyHttpFilter].
+func (e envoyFilter) GetDestinationAddress() string {
+	// https://github.com/envoyproxy/envoy/blob/05223ee2cd143d70b32402783c2a866a9dd18bd1/source/extensions/dynamic_modules/abi.h#L237-L372
+	return e.getStringAttribute(26) // destination.address
+}
+
 func (e envoyFilter) getStringAttribute(id int) string {
 	var resultBufferPtr *byte
 	var resultBufferLengthPtr int

go/gosdk/gosdk.go

@@ -59,6 +59,9 @@ type EnvoyHttpFilter interface {
 	// GetSourceAddress gets the source address of the request in the format of "IP:PORT".
 	// This corresponds to `source.address` attribute https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/advanced/attributes.
 	GetSourceAddress() string
+	// GetDestinationAddress gets the destination address of the request in the format of "IP:PORT".
+	// This corresponds to `destination.address` attribute https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/advanced/attributes.
+	GetDestinationAddress() string
 	// GetRequestProtocol gets the request protocol. This corresponds to `request.protocol` attribute https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/advanced/attributes.
 	GetRequestProtocol() string
 	// NewScheduler creates a new Scheduler that can be used to schedule events to the correct Envoy worker thread.

go/mock_test.go

@@ -8,24 +8,25 @@ import (
 
 // mockEnvoyHttpFilter is a mock implementation of [gosdk.EnvoyHttpFilter] for testing.
 type mockEnvoyHttpFilter struct {
-	getRequestHeader   func(key string) (string, bool)
-	getRequestHeaders  func() map[string][]string
-	setRequestHeader   func(key string, value []byte) bool
-	getResponseHeader  func(key string) (string, bool)
-	getResponseHeaders func() map[string][]string
-	setResponseHeader  func(key string, value []byte) bool
-	getRequestBody     func() (io.Reader, bool)
-	drainRequestBody   func(n int) bool
-	appendRequestBody  func(data []byte) bool
-	getResponseBody    func() (io.Reader, bool)
-	drainResponseBody  func(n int) bool
-	appendResponseBody func(data []byte) bool
-	sendLocalReply     func(statusCode uint32, headers [][2]string, body []byte)
-	getSourceAddress   func() string
-	getRequestProtocol func() string
-	newScheduler       func() gosdk.Scheduler
-	continueRequest    func()
-	continueResponse   func()
+	getRequestHeader      func(key string) (string, bool)
+	getRequestHeaders     func() map[string][]string
+	setRequestHeader      func(key string, value []byte) bool
+	getResponseHeader     func(key string) (string, bool)
+	getResponseHeaders    func() map[string][]string
+	setResponseHeader     func(key string, value []byte) bool
+	getRequestBody        func() (io.Reader, bool)
+	drainRequestBody      func(n int) bool
+	appendRequestBody     func(data []byte) bool
+	getResponseBody       func() (io.Reader, bool)
+	drainResponseBody     func(n int) bool
+	appendResponseBody    func(data []byte) bool
+	sendLocalReply        func(statusCode uint32, headers [][2]string, body []byte)
+	getSourceAddress      func() string
+	getDestinationAddress func() string
+	getRequestProtocol    func() string
+	newScheduler          func() gosdk.Scheduler
+	continueRequest       func()
+	continueResponse      func()
 }
 
 // GetRequestHeader implements [gosdk.EnvoyHttpFilter.GetRequestHeader].
@@ -98,6 +99,11 @@ func (m mockEnvoyHttpFilter) GetSourceAddress() string {
 	return m.getSourceAddress()
 }
 
+// GetDestinationAddress implements [gosdk.EnvoyHttpFilter.GetDestinationAddress].
+func (m mockEnvoyHttpFilter) GetDestinationAddress() string {
+	return m.getDestinationAddress()
+}
+
 // GetRequestProtocol implements [gosdk.EnvoyHttpFilter.GetRequestProtocol].
 func (m mockEnvoyHttpFilter) GetRequestProtocol() string {
 	return m.getRequestProtocol()

go/passthrough.go

@@ -37,6 +37,7 @@ func (p passthroughFilter) RequestHeaders(e gosdk.EnvoyHttpFilter, endOfStream b
 		}
 	}
 	fmt.Printf("gosdk: RequestHeaders, source address: %s\n", e.GetSourceAddress())
+	fmt.Printf("gosdk: RequestHeaders, destination address: %s\n", e.GetDestinationAddress())
 	fmt.Printf("gosdk: RequestHeaders, request protocol: %s\n", e.GetRequestProtocol())
 	return gosdk.RequestHeadersStatusContinue
 }