From 88d21ce627f0aabd9d1e336ef42e08354c1044d8 Mon Sep 17 00:00:00 2001
From: Matt Joiner <anacrolix@gmail.com>
Date: Tue, 17 May 2016 16:06:18 +1000
Subject: [PATCH] dht: Don't contact nodes with an IP containing a leading
 octet of 0

---
 dht/announce.go | 14 ++++++++++++--
 dht/dht_test.go |  8 ++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/dht/announce.go b/dht/announce.go
index ead301a4..c6b64579 100644
--- a/dht/announce.go
+++ b/dht/announce.go
@@ -115,10 +115,20 @@ func (s *Server) Announce(infoHash string, port int, impliedPort bool) (*Announc
 	return disc, nil
 }
 
+func validNodeAddr(addr Addr) bool {
+	ua := addr.UDPAddr()
+	if ua.Port == 0 {
+		return false
+	}
+	if ip4 := ua.IP.To4(); ip4 != nil && ip4[0] == 0 {
+		return false
+	}
+	return true
+}
+
 // TODO: Merge this with maybeGetPeersFromAddr.
 func (a *Announce) gotNodeAddr(addr Addr) {
-	if addr.UDPAddr().Port == 0 {
-		// Not a contactable address.
+	if !validNodeAddr(addr) {
 		return
 	}
 	if a.triedAddrs.Test([]byte(addr.String())) {
diff --git a/dht/dht_test.go b/dht/dht_test.go
index 166e8f0c..6ed8c4aa 100644
--- a/dht/dht_test.go
+++ b/dht/dht_test.go
@@ -221,3 +221,11 @@ func TestHook(t *testing.T) {
 		}
 	}
 }
+
+// Check that address resolution doesn't rat out invalid SendTo addr
+// arguments.
+func TestResolveBadAddr(t *testing.T) {
+	ua, err := net.ResolveUDPAddr("udp", "0.131.255.145:33085")
+	require.NoError(t, err)
+	assert.False(t, validNodeAddr(NewAddr(ua)))
+}
-- 
2.48.1