From 826f64e863ec5950f0c9f74c165050fba3725722 Mon Sep 17 00:00:00 2001
From: Brad Fitzpatrick <bradfitz@tailscale.com>
Date: Fri, 19 Feb 2021 07:48:35 -0800
Subject: [PATCH] cmd/tailscale/cli: add netcheck dev knob
 TS_DEBUG_NETCHECK_UDP_BIND

---
 cmd/tailscale/cli/netcheck.go | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/cmd/tailscale/cli/netcheck.go b/cmd/tailscale/cli/netcheck.go
index 04d3ab0ab..55de4ca99 100644
--- a/cmd/tailscale/cli/netcheck.go
+++ b/cmd/tailscale/cli/netcheck.go
@@ -43,7 +43,9 @@ var netcheckArgs struct {
 }
 
 func runNetcheck(ctx context.Context, args []string) error {
-	c := &netcheck.Client{}
+	c := &netcheck.Client{
+		UDPBindAddr: os.Getenv("TS_DEBUG_NETCHECK_UDP_BIND"),
+	}
 	if netcheckArgs.verbose {
 		c.Logf = logger.WithPrefix(log.Printf, "netcheck: ")
 		c.Verbose = true