[FAB-6613] Build golang chaincode dynamically

Fabric currently forces static build of golang chaincode.
This prevents user chaincode to use extensions (e.g. pkcs11)
which require dynamic linking. This code change keeps static
linking the default. Dynamic chaincode linking is enabled by
setting chaincode.golang.dynamicLink to true in core.yaml.

NOTE: Dynamic linking requires a custom image.
Currently, hyperledger/fabric-baseos image does not
include the C libraries required for dynamic linking.

Change-Id: I189e9f30d12abb107d03d212561cf137b7fa724a
Signed-off-by: Aleksandar Likic <aleksandar.likic@securekey.com>

Author: Aleksandar Likic

core/chaincode/platforms/golang/platform.go

@@ -34,6 +34,7 @@ import (
 	"github.com/hyperledger/fabric/core/chaincode/platforms/util"
 	cutil "github.com/hyperledger/fabric/core/container/util"
 	pb "github.com/hyperledger/fabric/protos/peer"
+	"github.com/spf13/viper"
 )
 
 // Platform for chaincodes written in Go
@@ -449,6 +450,16 @@ func (goPlatform *Platform) GenerateDockerfile(cds *pb.ChaincodeDeploymentSpec)
 	return dockerFileContents, nil
 }
 
+const staticLDFlagsOpts = "-ldflags \"-linkmode external -extldflags '-static'\""
+const dynamicLDFlagsOpts = ""
+
+func getLDFlagsOpts() string {
+	if viper.GetBool("chaincode.golang.dynamicLink") {
+		return dynamicLDFlagsOpts
+	}
+	return staticLDFlagsOpts
+}
+
 func (goPlatform *Platform) GenerateDockerBuild(cds *pb.ChaincodeDeploymentSpec, tw *tar.Writer) error {
 	spec := cds.ChaincodeSpec
 
@@ -457,7 +468,9 @@ func (goPlatform *Platform) GenerateDockerBuild(cds *pb.ChaincodeDeploymentSpec,
 		return fmt.Errorf("could not decode url: %s", err)
 	}
 
-	const ldflags = "-linkmode external -extldflags '-static'"
+	ldflagsOpt := getLDFlagsOpts()
+	logger.Infof("building chaincode with ldflagsOpt: '%s'", ldflagsOpt)
+
 	var gotags string
 	// check if experimental features are enabled
 	if metadata.Experimental == "true" {
@@ -468,7 +481,7 @@ func (goPlatform *Platform) GenerateDockerBuild(cds *pb.ChaincodeDeploymentSpec,
 	codepackage := bytes.NewReader(cds.CodePackage)
 	binpackage := bytes.NewBuffer(nil)
 	err = util.DockerBuild(util.DockerBuildOptions{
-		Cmd:          fmt.Sprintf("GOPATH=/chaincode/input:$GOPATH go build -tags \"%s\" -ldflags \"%s\" -o /chaincode/output/chaincode %s", gotags, ldflags, pkgname),
+		Cmd:          fmt.Sprintf("GOPATH=/chaincode/input:$GOPATH go build -tags \"%s\" %s -o /chaincode/output/chaincode %s", gotags, ldflagsOpt, pkgname),
 		InputStream:  codepackage,
 		OutputStream: binpackage,
 	})

core/chaincode/platforms/golang/platform_go19_test.go

@@ -242,6 +242,18 @@ func TestGetDeploymentPayload(t *testing.T) {
 	}
 }
 
+//TestGetLDFlagsOpts tests handling of chaincode.golang.dynamicLink
+func TestGetLDFlagsOpts(t *testing.T) {
+	viper.Set("chaincode.golang.dynamicLink", true)
+	if getLDFlagsOpts() != dynamicLDFlagsOpts {
+		t.Error("Error handling chaincode.golang.dynamicLink configuration. ldflags should be for dynamic linkink")
+	}
+	viper.Set("chaincode.golang.dynamicLink", false)
+	if getLDFlagsOpts() != staticLDFlagsOpts {
+		t.Error("Error handling chaincode.golang.dynamicLink configuration. ldflags should be for static linkink")
+	}
+}
+
 //TestGenerateDockerBuild goes through the functions needed to do docker build
 func TestGenerateDockerBuild(t *testing.T) {
 	platform := &Platform{}

sampleconfig/core.yaml

@@ -391,6 +391,9 @@ chaincode:
         # golang will never need more than baseos
         runtime: $(BASE_DOCKER_NS)/fabric-baseos:$(ARCH)-$(BASE_VERSION)
 
+        # whether or not golang chaincode should be linked dynamically
+        dynamicLink: false
+
     car:
         # car may need more facilities (JVM, etc) in the future as the catalog
         # of platforms are expanded.  For now, we can just use baseos