Fix returning message reply on retval errors (#147)

* fix handling of EAGAIN reply return value

The new VPP binapi for stream can return a reply with the return value EAGAIN. This value signals, that VPP ends the transmition because the call has taken to long and is possibly blocking the master thread.
The client is then expected to repeat the request, optimally providing the cursor to the last received data.
Sofar, the implementation only returned an error without providing the cursor to the last received data point (in older versions, e.g., v0.4.0, govpp does not return an error and just accepts the incomplete response).

* Revert converting retval field to error

Signed-off-by: Ondrej Fabry <[email protected]>

---------

Signed-off-by: Ondrej Fabry <[email protected]>
Co-authored-by: Fabio Streun <[email protected]>

Author: ondrej-fabry

Diff for: api/errors.go

@@ -169,6 +169,21 @@ const (
 	INVALID_VALUE_3                    VPPApiError = -150
 	NON_ETHERNET                       VPPApiError = -151
 	BD_ALREADY_HAS_BVI                 VPPApiError = -152
+	INVALID_PROTOCOL                   VPPApiError = -153
+	INVALID_ALGORITHM                  VPPApiError = -154
+	RSRC_IN_USE                        VPPApiError = -155
+	KEY_LENGTH                         VPPApiError = -156
+	FIB_PATH_UNSUPPORTED_NH_PROTO      VPPApiError = -157
+	API_ENDIAN_FAILED                  VPPApiError = -159
+	NO_CHANGE                          VPPApiError = -160
+	MISSING_CERT_KEY                   VPPApiError = -161
+	LIMIT_EXCEEDED                     VPPApiError = -162
+	IKE_NO_PORT                        VPPApiError = -163
+	UDP_PORT_TAKEN                     VPPApiError = -164
+	EAGAIN                             VPPApiError = -165
+	INVALID_VALUE_4                    VPPApiError = -166
+	BUSY                               VPPApiError = -167
+	BUG                                VPPApiError = -168
 )
 
 var vppApiErrors = map[VPPApiError]string{
@@ -298,4 +313,19 @@ var vppApiErrors = map[VPPApiError]string{
 	INVALID_VALUE_3:                    "Invalid value #3",
 	NON_ETHERNET:                       "Interface is not an Ethernet interface",
 	BD_ALREADY_HAS_BVI:                 "Bridge domain already has a BVI interface",
+	INVALID_PROTOCOL:                   "Invalid Protocol",
+	INVALID_ALGORITHM:                  "Invalid Algorithm",
+	RSRC_IN_USE:                        "Resource In Use",
+	KEY_LENGTH:                         "invalid Key Length",
+	FIB_PATH_UNSUPPORTED_NH_PROTO:      "Unsupported FIB Path protocol",
+	API_ENDIAN_FAILED:                  "Endian mismatch detected",
+	NO_CHANGE:                          "No change in table",
+	MISSING_CERT_KEY:                   "Missing certifcate or key",
+	LIMIT_EXCEEDED:                     "limit exceeded",
+	IKE_NO_PORT:                        "port not managed by IKE",
+	UDP_PORT_TAKEN:                     "UDP port already taken",
+	EAGAIN:                             "Retry stream call with cursor",
+	INVALID_VALUE_4:                    "Invalid value #4",
+	BUSY:                               "Busy",
+	BUG:                                "Bug",
 }

Diff for: binapi/graph/graph_rpc.ba.go

@@ -327,9 +327,9 @@ func newMessage(gen *Generator, file *File, apitype vppapi.Message) *Message {
 	var n int
 	for _, fieldType := range apitype.Fields {
 		if n == 0 {
-			// skip header fields
 			switch strings.ToLower(fieldType.Name) {
 			case fieldMsgID, fieldClientIndex, fieldContext:
+				// skip header fields
 				continue
 			}
 		}

Diff for: binapi/interface/interface_rpc.ba.go

@@ -169,13 +169,9 @@ func genService(g *GenFile, svc *Service) {
 			g.P("	case *", msgReply.GoIdent, ":")
 			if msgReply != msgControlPingReply {
 				if retvalField := getRetvalField(msgReply); retvalField != nil {
-					s := fmt.Sprint("(m.", retvalField.GoName, ")")
-					if fieldType := getFieldType(g, retvalField); fieldType != "int32" {
-						s = fmt.Sprint("(int32(m.", retvalField.GoName, "))")
-					}
-					g.P("if err := ", govppApiPkg.Ident("RetvalToVPPApiError"), s, "; err != nil {")
+					g.P("if err := ", retvalFieldToErr(g, "m", retvalField), "; err != nil {")
 					if msgReply != msgControlPingReply {
-						g.P("	return nil, nil, err")
+						g.P("	return nil, m, err")
 					} else {
 						g.P("	return nil, err")
 					}
@@ -184,7 +180,7 @@ func genService(g *GenFile, svc *Service) {
 			}
 			g.P("		err = c.Stream.Close()")
 			if msgReply != msgControlPingReply {
-				g.P("	if err != nil { return nil, nil, err }")
+				g.P("	if err != nil { return nil, m, err }")
 			} else {
 				g.P("	if err != nil { return nil, err }")
 			}
@@ -205,15 +201,11 @@ func genService(g *GenFile, svc *Service) {
 			g.P("err := c.conn.Invoke(ctx, in, out)")
 			g.P("if err != nil { return nil, err }")
 			if retvalField := getRetvalField(rpc.MsgReply); retvalField != nil {
-				if fieldType := getFieldType(g, retvalField); fieldType == "int32" {
-					g.P("return out, ", govppApiPkg.Ident("RetvalToVPPApiError"), "(out.", retvalField.GoName, ")")
-				} else {
-					g.P("return out, ", govppApiPkg.Ident("RetvalToVPPApiError"), "(int32(out.", retvalField.GoName, "))")
-				}
+				g.P("return out, ", retvalFieldToErr(g, "out", retvalField))
 			} else {
 				g.P("return out, nil")
 			}
-		} else {
+		} else { // MsgReply == nil
 			g.P("stream, err := c.conn.NewStream(ctx)")
 			g.P("if err != nil { return err }")
 			g.P("err = stream.SendMsg(in)")
@@ -245,6 +237,14 @@ func genService(g *GenFile, svc *Service) {
 	g.P()
 }
 
+func retvalFieldToErr(g *GenFile, varName string, retvalField *Field) string {
+	if getFieldType(g, retvalField) == "int32" {
+		return g.GoIdent(govppApiPkg.Ident("RetvalToVPPApiError")) + "(" + varName + "." + retvalField.GoName + ")"
+	} else {
+		return g.GoIdent(govppApiPkg.Ident("RetvalToVPPApiError")) + "(int32(" + varName + "." + retvalField.GoName + "))"
+	}
+}
+
 func rpcMethodSignature(g *GenFile, rpc *RPC) string {
 	s := rpc.GoName + "(ctx " + g.GoIdent(contextPkg.Ident("Context"))
 	s += ", in *" + g.GoIdent(rpc.MsgRequest.GoIdent) + ") ("