skip port 25 check on Azure as well as GCE

daemon/maintenance/maintenance.go

@@ -102,7 +102,7 @@ func (daemon *Daemon) runPortsCheck() error {
 			continue
 		}
 		for _, port := range ports {
-			if port == 25 && inet.IsGCE() {
+			if port == 25 && (inet.IsGCE() || inet.IsAzure()) {
 				daemon.logger.Info("runPortsCheck", "", nil, "because Google cloud forbids connection to port 25, port check will skip %s:25", host)
 				continue
 			}

inet/ip.go

@@ -1,6 +1,7 @@
 package inet
 
 import (
+	"io/ioutil"
 	"strings"
 	"sync"
 	"time"
@@ -12,6 +13,10 @@ var (
 	// isGCE is true only if IsGCE function has determined that the program is running on Google compute engine.
 	isGCE     bool
 	isGCEOnce = new(sync.Once)
+
+	// isAzure is true only if IsAzure function has determined that the program is running on Microsoft Azure.
+	isAzure     bool
+	isAzureOnce = new(sync.Once)
 )
 
 // IsGCE returns true only if the program is running on Google compute engine (or Google cloud platform, same thing).
@@ -28,6 +33,19 @@ func IsGCE() bool {
 	return isGCE
 }
 
+// IsAzure returns true only if the program is running on Microsoft Azure virtual machine.
+func IsAzure() bool {
+	isAzureOnce.Do(func() {
+		content, err := ioutil.ReadFile("/var/lib/dhcp/dhclient.eth0.leases")
+		if err == nil {
+			if strings.Contains(string(content), "unknown-245") {
+				isAzure = true
+			}
+		}
+	})
+	return isAzure
+}
+
 /*
 GetPublicIP returns the latest public IP address of the computer. If the IP address cannot be determined, it will return
 an empty string. The function may take up to 3 seconds to return a value.