From 2041438866a21d52ce7d1c14da7a36ebb48827bc Mon Sep 17 00:00:00 2001
From: Takeshi Yoneda <takeshi@tetrate.io>
Date: Wed, 27 Oct 2021 14:01:06 +0900
Subject: [PATCH] Fix panic in dispatched callback on getting empty http
 trailers. (#218)

Signed-off-by: Takeshi Yoneda <takeshi@tetrate.io>
---
 e2e/e2e_test.go                           |  1 +
 examples/dispatch_call_on_tick/envoy.yaml |  7 +++++-
 examples/dispatch_call_on_tick/main.go    | 30 ++++++++++++++++++++---
 proxywasm/hostcall.go                     |  2 ++
 proxywasm/proxytest/http.go               |  8 ++++++
 5 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/e2e/e2e_test.go b/e2e/e2e_test.go
index 8b22ffa7..226c7925 100644
--- a/e2e/e2e_test.go
+++ b/e2e/e2e_test.go
@@ -34,6 +34,7 @@ func Test_dispatch_call_on_tick(t *testing.T) {
 		if checkMessage(stdErr.String(), []string{
 			fmt.Sprintf("called %d for contextID=1", count),
 			fmt.Sprintf("called %d for contextID=2", count),
+			":status: 200", ":status: 503",
 		}, nil) {
 			count++
 		}
diff --git a/examples/dispatch_call_on_tick/envoy.yaml b/examples/dispatch_call_on_tick/envoy.yaml
index eb1505da..f10bf8e7 100644
--- a/examples/dispatch_call_on_tick/envoy.yaml
+++ b/examples/dispatch_call_on_tick/envoy.yaml
@@ -74,11 +74,16 @@ static_resources:
                         - "*"
                       routes:
                         - match:
-                            prefix: "/"
+                            prefix: "/ok"
                           direct_response:
                             status: 200
                             body:
                               inline_string: "example body\n"
+                        - match:
+                            prefix: "/fail"
+                          direct_response:
+                            status: 503
+
                 http_filters:
                   - name: envoy.filters.http.router
                     typed_config: {}
diff --git a/examples/dispatch_call_on_tick/main.go b/examples/dispatch_call_on_tick/main.go
index 483ea36b..685a2609 100644
--- a/examples/dispatch_call_on_tick/main.go
+++ b/examples/dispatch_call_on_tick/main.go
@@ -15,6 +15,8 @@
 package main
 
 import (
+	"crypto/rand"
+
 	"github.com/tetratelabs/proxy-wasm-go-sdk/proxywasm"
 	"github.com/tetratelabs/proxy-wasm-go-sdk/proxywasm/types"
 )
@@ -55,16 +57,38 @@ func (ctx *pluginContext) OnPluginStart(pluginConfigurationSize int) types.OnPlu
 	ctx.callBack = func(numHeaders, bodySize, numTrailers int) {
 		ctx.cnt++
 		proxywasm.LogInfof("called %d for contextID=%d", ctx.cnt, ctx.contextID)
+		headers, err := proxywasm.GetHttpCallResponseHeaders()
+		if err != nil && err != types.ErrorStatusNotFound {
+			panic(err)
+		}
+		for _, h := range headers {
+			proxywasm.LogInfof("response header for the dispatched call: %s: %s", h[0], h[1])
+		}
+		headers, err = proxywasm.GetHttpCallResponseTrailers()
+		if err != nil && err != types.ErrorStatusNotFound {
+			panic(err)
+		}
+		for _, h := range headers {
+			proxywasm.LogInfof("response trailer for the dispatched call: %s: %s", h[0], h[1])
+		}
 	}
 	return types.OnPluginStartStatusOK
 }
 
 // Override types.DefaultPluginContext.
 func (ctx *pluginContext) OnTick() {
-	hs := [][2]string{
-		{":method", "GET"}, {":authority", "some_authority"}, {":path", "/path/to/service"}, {"accept", "*/*"},
+	headers := [][2]string{
+		{":method", "GET"}, {":authority", "some_authority"}, {"accept", "*/*"},
+	}
+	// Pick random value to select the request path.
+	buf := make([]byte, 1)
+	_, _ = rand.Read(buf)
+	if buf[0]%2 == 0 {
+		headers = append(headers, [2]string{":path", "/ok"})
+	} else {
+		headers = append(headers, [2]string{":path", "/fail"})
 	}
-	if _, err := proxywasm.DispatchHttpCall("web_service", hs, nil, nil, 5000, ctx.callBack); err != nil {
+	if _, err := proxywasm.DispatchHttpCall("web_service", headers, nil, nil, 5000, ctx.callBack); err != nil {
 		proxywasm.LogCriticalf("dispatch httpcall failed: %v", err)
 	}
 }
diff --git a/proxywasm/hostcall.go b/proxywasm/hostcall.go
index 2504ffb3..df6df606 100644
--- a/proxywasm/hostcall.go
+++ b/proxywasm/hostcall.go
@@ -781,6 +781,8 @@ func getMap(mapType internal.MapType) ([][2]string, error) {
 	st := internal.ProxyGetHeaderMapPairs(mapType, &raw, &rvs)
 	if st != internal.StatusOK {
 		return nil, internal.StatusToError(st)
+	} else if raw == nil {
+		return nil, types.ErrorStatusNotFound
 	}
 
 	bs := internal.RawBytePtrToByteSlice(raw, rvs)
diff --git a/proxywasm/proxytest/http.go b/proxywasm/proxytest/http.go
index f1d7c434..6acb844a 100644
--- a/proxywasm/proxytest/http.go
+++ b/proxywasm/proxytest/http.go
@@ -272,6 +272,14 @@ func (h *httpHostEmulator) httpHostEmulatorProxyGetHeaderMapPairs(mapType intern
 		panic("unreachable: maybe a bug in this host emulation or SDK")
 	}
 
+	if len(m) == 0 {
+		// The host might reutrn OK without setting the data pointer,
+		// if there's nothing to pass to Wasm VM.
+		*returnValueData = nil
+		*returnValueSize = 0
+		return internal.StatusOK
+	}
+
 	*returnValueData = &m[0]
 	*returnValueSize = len(m)
 	return internal.StatusOK