TUN-2921: Rework address selection logic to avoid corner cases

edgediscovery/allregions/region.go

@@ -2,6 +2,8 @@ package allregions
 
 import (
 	"net"
+
+	"github.com/sirupsen/logrus"
 )
 
 // Region contains cloudflared edge addresses. The edge is partitioned into several regions for
@@ -56,6 +58,10 @@ func (r Region) GetUnusedIP(excluding *net.TCPAddr) *net.TCPAddr {
 
 // Use the address, assigning it to a proxy connection.
 func (r Region) Use(addr *net.TCPAddr, connID int) {
+	if addr == nil {
+		logrus.Errorf("Attempted to use nil address for connection %d", connID)
+		return
+	}
 	r.connFor[addr] = InUse(connID)
 }