From 1b51e5803c966d940f462733f408f2471528b6b8 Mon Sep 17 00:00:00 2001
From: hc-github-team-consul-core
 <82989933+hc-github-team-consul-core@users.noreply.github.com>
Date: Mon, 8 Aug 2022 17:30:27 -0400
Subject: [PATCH] backport of commit 9c6d3fd332709aed81608b473745c9e0d11d5b86
 (#14068)

This pull request was automerged via backport-assistant
---
 sdk/freeport/freeport.go | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/sdk/freeport/freeport.go b/sdk/freeport/freeport.go
index 40d9cdb3b8c9..6eda1d4279b9 100644
--- a/sdk/freeport/freeport.go
+++ b/sdk/freeport/freeport.go
@@ -83,6 +83,10 @@ var (
 	// stopWg is used to keep track of background goroutines that are still
 	// alive. Only really exists for the safety of reset() during unit tests.
 	stopWg sync.WaitGroup
+
+	// portLastUser associates ports with a test name in order to debug
+	// which test may be leaking unclosed TCP connections.
+	portLastUser map[int]string
 )
 
 // initialize is used to initialize freeport.
@@ -127,6 +131,8 @@ func initialize() {
 
 	stopWg.Add(1)
 	stopCh = make(chan struct{})
+
+	portLastUser = make(map[int]string)
 	// Note: we pass this param explicitly to the goroutine so that we can
 	// freely recreate the underlying stop channel during reset() after closing
 	// the original.
@@ -166,6 +172,7 @@ func reset() {
 
 	freePorts = nil
 	pendingPorts = nil
+	portLastUser = nil
 	total = 0
 }
 
@@ -196,7 +203,7 @@ func checkFreedPortsOnce() {
 			freePorts.PushBack(port)
 			remove = append(remove, elem)
 		} else {
-			logf("WARN", "port %d still being used", port)
+			logf("WARN", "port %d still being used by %q", port, portLastUser[port])
 		}
 	}
 
@@ -416,6 +423,11 @@ func GetN(t TestingT, n int) []int {
 		t.Fatalf("failed to take %v ports: %w", n, err)
 	}
 	logf("DEBUG", "Test %q took ports %v", t.Name(), ports)
+	mu.Lock()
+	for _, p := range ports {
+		portLastUser[p] = t.Name()
+	}
+	mu.Unlock()
 	t.Cleanup(func() {
 		Return(ports)
 		logf("DEBUG", "Test %q returned ports %v", t.Name(), ports)