From ff5b5e15f17c5fc24b55c45ef426daa6d1b91195 Mon Sep 17 00:00:00 2001
From: gop <gameofpointers@proton.me>
Date: Fri, 8 Sep 2023 15:01:10 -0500
Subject: [PATCH] Added fetcher limit for block imports as a DDos prevention
 mechanism

---
 eth/fetcher/block_fetcher.go | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/eth/fetcher/block_fetcher.go b/eth/fetcher/block_fetcher.go
index f1cd195a81..f2d4e04f64 100644
--- a/eth/fetcher/block_fetcher.go
+++ b/eth/fetcher/block_fetcher.go
@@ -350,7 +350,12 @@ func (f *BlockFetcher) loop() {
 				f.forgetBlock(hash)
 				continue
 			}
-			f.importBlocks(op.origin, op.block)
+
+			// Only import blocks using the Fetcher if its within maxUncleDist
+			// This is done to prevent DDos on the append queue
+			if op != nil && op.block.NumberU64()+maxUncleDist > f.chainHeight() {
+				f.importBlocks(op.origin, op.block)
+			}
 		}
 		// Wait for an outside event to occur
 		select {