Try and pull packet info out of source. gamepack 16 and 17 are actually identical, I didn't realize. Interestingly i found if I attempt to map deobbed client that is rebuilt vs the deobbed client, it can't map everything. Some of that might have to do with the packet handling stuff, this currently npes in iinc so I can't tell how many is due to that yet.

src/main/java/net/runelite/deob/deobfuscators/rename/Mapper.java

@@ -8,9 +8,12 @@ import java.util.List;
 import java.util.Map;
 import net.runelite.deob.ClassFile;
 import net.runelite.deob.ClassGroup;
+import net.runelite.deob.Field;
 import net.runelite.deob.Method;
+import net.runelite.deob.attributes.Annotations;
 import net.runelite.deob.attributes.code.Instruction;
 import net.runelite.deob.execution.ParallellMappingExecutor;
+import net.runelite.deob.signature.Type;
 
 public class Mapper
 {
@@ -36,7 +39,7 @@ public class Mapper
 
 		finalm.merge(mapStaticMethods(source, target));
 		finalm.merge(mapMethods(source, target));
-		finalm.merge(mapPackets(source, target));
+		finalm.merge(mapPackets(finalm, source, target));
 
 		mapping = finalm;
 	}
@@ -145,16 +148,24 @@ public class Mapper
 		}
 	}
 
-	private ParallelExecutorMapping mapPackets(ClassGroup group1, ClassGroup group2)
+	private ParallelExecutorMapping mapPackets(ParallelExecutorMapping pem, ClassGroup group1, ClassGroup group2)
 	{
-		// XXX PULL THESE FROM PREVIOUS MAPPINGS
-		group1.findClass("client").findField("field446").packetHandler = true;
-		group2.findClass("client").findField("field324").packetHandler = true;
+		Method packetMethod = this.findPacketMethod();
+		Field packetField = this.findPacketField();
 
-		Method m1 = group1.findClass("client").findMethod("vmethod3096");
-		Method m2 = group2.findClass("client").findMethod("vmethod2975");
+		assert packetMethod != null;
+		assert packetField != null;
 
-		ParallelExecutorMapping mappings = MappingExecutorUtil.map(m1, m2);
+		Method otherPacketMethod = (Method) pem.get(packetMethod);
+		Field otherPacketField = (Field) pem.get(packetField);
+
+		assert otherPacketMethod != null;
+		assert otherPacketField != null;
+
+		packetField.packetHandler = true;
+		otherPacketField.packetHandler = true;
+
+		ParallelExecutorMapping mappings = MappingExecutorUtil.map(packetMethod, otherPacketMethod);
 
 		System.out.println(mappings.packetHandler1.size() + " vs " + mappings.packetHandler2.size() + " handlers");
 
@@ -196,4 +207,41 @@ public class Mapper
 		ParallellMappingExecutor.enable = false;
 		return all;
 	}
+
+
+	private static final Type OBFUSCATED_NAME = new Type("Lnet/runelite/mapping/Export;");
+
+	private Field findPacketField()
+	{
+		for (ClassFile cf : source.getClasses())
+		{
+			for (Field f : cf.getFields().getFields())
+			{
+				Annotations an = f.getAttributes().getAnnotations();
+
+				if (an == null || an.find(OBFUSCATED_NAME) == null)
+					continue;
+
+				if (an.find(OBFUSCATED_NAME).getElement().getString().equals("packetOpcode"))
+					return f;
+			}
+		}
+		return null;
+	}
+
+	private Method findPacketMethod()
+	{
+		for (Method m : source.findClass("client").getMethods().getMethods())
+		{
+			Annotations an = m.getAttributes().getAnnotations();
+
+			if (an == null || an.find(OBFUSCATED_NAME) == null)
+				continue;
+
+			if (an.find(OBFUSCATED_NAME).getElement().getString().equals("packetHandler"))
+				return m;
+		}
+
+		return null;
+	}
 }