Ensure non-zero minimum TTL for the domain in egress network policy

Author: Ravi Sankar Penta

pkg/network/common/dns.go

@@ -154,8 +154,13 @@ func (d *DNS) getIPsAndMinTTL(domain string) ([]net.IP, time.Duration, error) {
 				case *dns.A:
 					ips = append(ips, t.A)
 
-					if minTTL == 0 || t.Hdr.Ttl < minTTL {
-						minTTL = t.Hdr.Ttl
+					// We could potentially get zero TTL as we try to query the DNS
+					// server at the end of the TTL value for the domain.
+					// Adding 1 sec will ensure non zero minTTL
+					ttl := t.Hdr.Ttl + 1
+
+					if minTTL == 0 || ttl < minTTL {
+						minTTL = ttl
 					}
 				}
 			}