Add P2P infinite loop detection (#1723)

src/main/java/appeng/parts/p2p/PartP2PItems.java

@@ -10,8 +10,10 @@
 
 package appeng.parts.p2p;
 
+import java.util.HashSet;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.Set;
 
 import net.minecraft.entity.player.EntityPlayer;
 import net.minecraft.init.Blocks;
@@ -88,6 +90,9 @@ public class PartP2PItems extends PartP2PTunnelNormal<PartP2PItems>
         }
 
         for (final PartP2PItems t : itemTunnels) {
+            if (t.loopsBackTo(this, new HashSet<>())) {
+                continue;
+            }
             final IInventory inv = t.getOutputInv();
             if (inv != null) {
                 if (Platform.getRandomInt() % 2 == 0) {
@@ -313,4 +318,29 @@ public class PartP2PItems extends PartP2PTunnelNormal<PartP2PItems>
     public ConnectOverride overridePipeConnection(final PipeType type, final ForgeDirection with) {
         return this.getSide() == with && type == PipeType.ITEM ? ConnectOverride.CONNECT : ConnectOverride.DEFAULT;
     }
+
+    private boolean loopsBackTo(final PartP2PItems tunnel, final Set<PartP2PItems> visited) {
+        final TileEntity te = this.getTile().getWorldObj().getTileEntity(
+                this.getTile().xCoord + this.getSide().offsetX,
+                this.getTile().yCoord + this.getSide().offsetY,
+                this.getTile().zCoord + this.getSide().offsetZ);
+        if (Platform.getPartFromTE(te, this.getSide().getOpposite()) instanceof PartP2PItems next) {
+            if (next == tunnel) {
+                return true;
+            }
+            if (!visited.contains(next)) {
+                visited.add(next);
+                try {
+                    for (final PartP2PItems t : next.getOutputs()) {
+                        if (t.loopsBackTo(tunnel, visited)) {
+                            return true;
+                        }
+                    }
+                } catch (final GridAccessException ignored) {
+                    // :P
+                }
+            }
+        }
+        return false;
+    }
 }

src/main/java/appeng/parts/p2p/PartP2PLiquids.java

@@ -221,7 +221,22 @@ public class PartP2PLiquids extends PartP2PTunnelNormal<PartP2PLiquids> implemen
 
     @Override
     public boolean canFill(final ForgeDirection from, final Fluid fluid) {
-        return from == this.getSide() && (!this.getOutputs(fluid).isEmpty() || inputAcceptsFluid(fluid));
+        if (from != this.getSide()) {
+            return false;
+        }
+
+        final Stack<PartP2PLiquids> stack = this.getDepth();
+        for (final PartP2PLiquids t : stack) {
+            if (t == this) {
+                return false;
+            }
+        }
+        stack.push(this);
+        try {
+            return !this.getOutputs(fluid).isEmpty() || inputAcceptsFluid(fluid);
+        } finally {
+            stack.pop();
+        }
     }
 
     @Override