idk

src/main/java/com/legacyminecraft/poseidon/commands/FlyCommand.java

@@ -11,7 +11,7 @@ public class FlyCommand extends Command {
 
     public FlyCommand(String name) {
         super(name);
-        this.description = "Toggles the server-side flight check exemption for yourself";
+        this.description = "Toggles server-side flight for yourself";
         this.usageMessage = "/fly";
     }
 
@@ -31,10 +31,10 @@ public class FlyCommand extends Command {
         player.flightAllowed = !player.flightAllowed;
 
         if (player.flightAllowed) {
-            sender.sendMessage(ChatColor.GREEN + "Flight check exemption enabled.");
+            sender.sendMessage(ChatColor.GREEN + "Flight enabled.");
-            sender.sendMessage(ChatColor.YELLOW + "A compatible client-side flight mod is required to fly.");
+            sender.sendMessage(ChatColor.YELLOW + "Look up to rise, look down or sneak to descend.");
         } else {
-            sender.sendMessage(ChatColor.YELLOW + "Flight check exemption disabled.");
+            sender.sendMessage(ChatColor.YELLOW + "Flight disabled.");
         }
 
         return true;

src/main/java/net/minecraft/server/NetServerHandler.java

@@ -187,6 +187,7 @@ public class NetServerHandler extends NetHandler implements ICommandListener {
             return;
 
         WorldServer worldserver = this.minecraftServer.getWorldServer(this.player.dimension);
+        boolean serverFlight = this.applyServerFlight(packet10flying);
 
         this.i = true;
         double d0;
@@ -441,8 +442,41 @@ public class NetServerHandler extends NetHandler implements ICommandListener {
             this.player.onGround = packet10flying.g;
             this.minecraftServer.serverConfigurationManager.d(this.player);
             this.player.b(this.player.locY - d0, packet10flying.g);
+
+            // A Beta client has no flight-ability packet. Keep its local position in
+            // sync with the server-controlled vertical movement while flying.
+            if (serverFlight) {
+                this.player.fallDistance = 0.0F;
+                this.sendPacket(new Packet13PlayerLookMove(this.player.locX, this.player.locY + 1.6200000047683716D, this.player.locY, this.player.locZ, this.player.yaw, this.player.pitch, false));
             }
         }
+    }
+
+    /**
+     * Converts a normal Beta movement packet into server-side flight movement.
+     * Looking up rises, looking down descends, and sneaking always descends.
+     * The client still supplies horizontal movement, so its normal movement keys
+     * continue to work without a modified client.
+     */
+    private boolean applyServerFlight(Packet10Flying packet10flying) {
+        if (!this.player.flightAllowed || !packet10flying.h || this.player.vehicle != null || this.player.isSleeping()) {
+            return false;
+        }
+
+        double verticalSpeed = 0.0D;
+        if (this.player.isSneaking() || packet10flying.pitch > 25.0F) {
+            verticalSpeed = -0.32D;
+        } else if (packet10flying.pitch < -25.0F) {
+            verticalSpeed = 0.32D;
+        }
+
+        packet10flying.y = this.player.locY + verticalSpeed;
+        packet10flying.stance = packet10flying.y + 1.6200000047683716D;
+        packet10flying.g = false;
+        this.player.motY = 0.0D;
+        this.player.fallDistance = 0.0F;
+        return true;
+    }
 
     public void a(double d0, double d1, double d2, float f, float f1) {
         // CraftBukkit start - Delegate to teleport(Location)