Add string function for DNSClass, DNSType and DNSOpCode
Add string function for DNSClass, DNSType and DNSOpCode

google/gopacket,google/gopacket,levigross/gopacket,rouzier/gopacket,xuzhaokui/gopacket,rouzier/gopacket,xuzhaokui/gopacket,rouzier/gopacket,google/gopacket,levigross/gopacket,levigross/gopacket,xuzhaokui/gopacket