From d7a81cb144141c4ebb4659437caa2ce680e3bdc6 Mon Sep 17 00:00:00 2001
From: hc-github-team-consul-core <github-team-consul-core@hashicorp.com>
Date: Mon, 6 Nov 2023 09:14:59 -0600
Subject: [PATCH] Backport of [NET-6459] Fix issue with wanfed lan ip
 conflicts. into release/1.16.x (#19522)

backport of commit a47995f72dba14020cc50e69eaffdf6b131159ae

Co-authored-by: Derek Menteer <derek.menteer@hashicorp.com>
---
 .changelog/19503.txt |  3 +++
 agent/pool/pool.go   | 11 +++++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)
 create mode 100644 .changelog/19503.txt

diff --git a/.changelog/19503.txt b/.changelog/19503.txt
new file mode 100644
index 000000000..cb89cfbec
--- /dev/null
+++ b/.changelog/19503.txt
@@ -0,0 +1,3 @@
+```release-note:bug
+wan-federation: Fix a bug where servers wan-federated through mesh-gateways could crash due to overlapping LAN IP addresses.
+```
diff --git a/agent/pool/pool.go b/agent/pool/pool.go
index cadb0e4af..dbe716476 100644
--- a/agent/pool/pool.go
+++ b/agent/pool/pool.go
@@ -49,6 +49,7 @@ type Conn struct {
 	refCount    int32
 	shouldClose int32
 
+	dc       string
 	nodeName string
 	addr     net.Addr
 	session  muxSession
@@ -234,7 +235,7 @@ func (p *ConnPool) acquire(dc string, nodeName string, addr net.Addr) (*Conn, er
 
 	addrStr := addr.String()
 
-	poolKey := nodeName + ":" + addrStr
+	poolKey := makePoolKey(dc, nodeName, addrStr)
 
 	// Check to see if there's a pooled connection available. This is up
 	// here since it should the vastly more common case than the rest
@@ -493,6 +494,7 @@ func (p *ConnPool) getNewConn(dc string, nodeName string, addr net.Addr) (*Conn,
 	// Wrap the connection
 	c := &Conn{
 		refCount: 1,
+		dc:       dc,
 		nodeName: nodeName,
 		addr:     addr,
 		session:  session,
@@ -514,7 +516,7 @@ func (p *ConnPool) clearConn(conn *Conn) {
 
 	// Clear from the cache
 	addrStr := conn.addr.String()
-	poolKey := conn.nodeName + ":" + addrStr
+	poolKey := makePoolKey(conn.dc, conn.nodeName, addrStr)
 	p.Lock()
 	if c, ok := p.pool[poolKey]; ok && c == conn {
 		delete(p.pool, poolKey)
@@ -716,3 +718,8 @@ func (p *ConnPool) reap() {
 		p.Unlock()
 	}
 }
+
+// makePoolKey generates a unique key for grouping connections together into a pool.
+func makePoolKey(dc, nodeName, addrStr string) string {
+	return dc + ":" + nodeName + ":" + addrStr
+}