Ipv6 payload length doesn't include header length. rfc8200 section 3 https://tools.ietf.org/html/rfc8200 Payload Length 16-bit unsigned integer. Length of the IPv6 payload, i.e., the rest of the packet following this IPv6 header, in octets. Bug: 215655463 Test: atest NetworkStaticLibTests Change-Id: Ifdc871125b0fe2eb3a8909b8b0723a62dbe44bcf