fix(cli): Resolve FQDN on Linux machines with short hostnames (#600)

If os.Hostname() returns a short hostname instead of a FQDN, lookup the
FQDN using net.LookupHost() and net.LookupAddr()

Resolves #189

Co-authored-by: Ganesh Raikhelkar <[email protected]>

internal/amt/linux.go

@@ -9,18 +9,42 @@
 package amt
 
 import (
+	"net"
 	"os"
 	"strings"
 )
 
 func (amt AMTCommand) GetOSDNSSuffix() (string, error) {
-	hostname, err := os.Hostname()
+	fqdn, err := getFQDN()
 	if err != nil {
 		return "", err
 	}
-	splitName := strings.SplitAfterN(hostname, ".", 2)
+	splitName := strings.SplitAfterN(fqdn, ".", 2)
 	if len(splitName) == 2 {
 		return splitName[1], nil
 	}
-	return hostname, err
+	return fqdn, err
+}
+
+func getFQDN() (string, error) {
+	hostname, err := os.Hostname()
+	if err != nil {
+		return "", err
+	}
+
+	if strings.Contains(hostname, ".") {
+		return hostname, nil
+	}
+
+	addrs, err := net.LookupHost(hostname)
+	if err != nil {
+		return "", err
+	}
+
+	names, err := net.LookupAddr(addrs[0])
+	if err != nil {
+		return "", err
+	}
+
+	return strings.TrimSuffix(names[0], "."), nil
 }