Handle stub/stub-v2 as viable --compress arguments

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+### Added
+
+- Support for `--compress stub-v2`.
+
 ### Fixed
 
 - Return error in install completion handler. [#206](https://github.com/passepartoutvpn/tunnelkit/issues/206)

TunnelKit/Sources/Protocols/OpenVPN/CompressionFraming.swift

@@ -40,6 +40,9 @@ extension OpenVPN {
         /// Framing compatible with 2.4 `compress`.
         case compress
 
+        /// Framing compatible with 2.4 `compress` (version 2, e.g. stub-v2).
+        case compressV2
+        
         var native: CompressionFramingNative {
             guard let val = CompressionFramingNative(rawValue: rawValue) else {
                 fatalError("Unhandled CompressionFraming bridging")
@@ -58,6 +61,9 @@ extension OpenVPN {
             case .compress:
                 return "compress"
                 
+            case .compressV2:
+                return "compress"
+                
             case .compLZO:
                 return "comp-lzo"
             }

TunnelKit/Sources/Protocols/OpenVPN/CompressionFramingNative.h

@@ -28,5 +28,6 @@
 typedef NS_ENUM(NSInteger, CompressionFramingNative) {
     CompressionFramingNativeDisabled,
     CompressionFramingNativeCompLZO,
-    CompressionFramingNativeCompress
+    CompressionFramingNativeCompress,
+    CompressionFramingNativeCompressV2
 };

TunnelKit/Sources/Protocols/OpenVPN/ConfigurationParser.swift

@@ -412,7 +412,20 @@ extension OpenVPN {
                         }
                     } else {
                         if let arg = $0.first {
-                            optCompressionAlgorithm = (arg == "lzo") ? .LZO : .other
+                            switch arg {
+                            case "lzo":
+                                optCompressionAlgorithm = .LZO
+                                
+                            case "stub":
+                                optCompressionAlgorithm = .disabled
+                                
+                            case "stub-v2":
+                                optCompressionFraming = .compressV2
+                                optCompressionAlgorithm = .disabled
+
+                            default:
+                                optCompressionAlgorithm = .other
+                            }
                         } else {
                             optCompressionAlgorithm = .disabled
                         }

TunnelKit/Sources/Protocols/OpenVPN/DataPath.m

@@ -195,13 +195,31 @@
                 *payloadOffset = 1;
                 break;
                 
-            default:
+            case DataPacketV2Indicator:
-                // @"Expected NO_COMPRESS (found %X != %X)", payload[0], DataPacketNoCompress);
+                if (compressionFraming == CompressionFramingNativeCompressV2) {
+                    if (payload[1] != DataPacketV2Uncompressed) {
                         if (error) {
                             *error = TunnelKitErrorWithCode(TunnelKitErrorCodeDataPathCompression);
                         }
                         return NO;
                     }
+                    *payloadOffset = 2;
+                } else {
+                    *payloadOffset = 0;
+                    *headerLength = 0;
+                }
+                break;
+
+            default:
+                // @"Expected NO_COMPRESS (found %X != %X)", payload[0], DataPacketNoCompress);
+//                if (error) {
+//                    *error = TunnelKitErrorWithCode(TunnelKitErrorCodeDataPathCompression);
+//                }
+//                return NO;
+                *payloadOffset = 0;
+                *headerLength = 0;
+                break;
+        }
         return YES;
     };
 
@@ -244,6 +262,25 @@
             self.parsePayloadBlock = parseCompressedBlock;
             break;
         }
+        case CompressionFramingNativeCompressV2: {
+            self.assemblePayloadBlock = ^(uint8_t * packetDest, NSInteger * packetLengthOffset, NSData * payload) {
+
+                // assume no compression (v2 algorithms unsupported)
+
+                // prepend headers only in case of byte ambiguity
+                const uint8_t first = *(uint8_t *)payload.bytes;
+                if (first == DataPacketV2Indicator) {
+                    *packetLengthOffset = 2;
+                    packetDest[0] = DataPacketV2Indicator;
+                    packetDest[1] = DataPacketV2Uncompressed;
+                } else {
+                    *packetLengthOffset = 0;
+                }
+                memcpy(packetDest + *packetLengthOffset, payload.bytes, payload.length);
+            };
+            self.parsePayloadBlock = parseCompressedBlock;
+            break;
+        }
         case CompressionFramingNativeCompLZO: {
             self.assemblePayloadBlock = ^(uint8_t * packetDest, NSInteger * packetLengthOffset, NSData * payload) {
                 NSData *compressedPayload = [weakSelf.lzo compressedDataWithData:payload error:NULL];

TunnelKit/Sources/Protocols/OpenVPN/PacketMacros.h

@@ -62,6 +62,9 @@ typedef NS_ENUM(uint8_t, PacketCode) {
 #define DataPacketNoCompressSwap    0xfb
 #define DataPacketLZOCompress       0x66
 
+#define DataPacketV2Indicator       0x50
+#define DataPacketV2Uncompressed    0x00
+
 extern const uint8_t DataPacketPingData[16];
 
 static inline void PacketOpcodeGet(const uint8_t *from, PacketCode *_Nullable code, uint8_t *_Nullable key)