From 7fab244614f1660daab400ab4261cfcdbe5137a6 Mon Sep 17 00:00:00 2001
From: David Anderson <danderson@tailscale.com>
Date: Tue, 20 Apr 2021 18:54:15 -0700
Subject: [PATCH] net/dns/resolver: don't spam logs on EHOSTUNREACH.

Fixes #1719.

Signed-off-by: David Anderson <danderson@tailscale.com>
---
 net/dns/resolver/forwarder.go | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/dns/resolver/forwarder.go b/net/dns/resolver/forwarder.go
index 4f5c46095..10854f802 100644
--- a/net/dns/resolver/forwarder.go
+++ b/net/dns/resolver/forwarder.go
@@ -14,6 +14,7 @@
 	"math/rand"
 	"net"
 	"sync"
+	"syscall"
 	"time"
 
 	dns "golang.org/x/net/dns/dnsmessage"
@@ -371,6 +372,12 @@ func (c *fwdConn) send(packet []byte, dst netaddr.IPPort) {
 			backOff(err)
 			continue
 		}
+		if errors.Is(err, syscall.EHOSTUNREACH) {
+			// "No route to host." The network stack is fine, but
+			// can't talk to this destination. Not much we can do
+			// about that, don't spam logs.
+			return
+		}
 		if networkIsDown(err) {
 			// Fail.
 			c.logf("send: network is down")