On Fri, 8 Aug 2025 20:56:33 +0200 Gábor LENCSE <len...@hit.bme.hu> wrote:
> Dear Stephen, > > Thank you very much for your answer. It helps me a lot, but I have > further questions. Please see my comments inline. > > The pseudo-header part is different. > If I understand it correctly, then it means that I need to write the > ICMPv6 checksum function myself. To that end, I reviewed the source code > of the "rte_ipv6_udptcp_cksum()" function so that I can learn from it. > However, I did not find where it differs from the one that I need. I > took the below source code from here: > https://doc.dpdk.org/api/rte__ip6_8h_source.html#l00610 > rte_ipv6_udptcp_cksum(const struct rte_ipv6_hdr *ipv6_hdr, const void > *l4_hdr) { uint16_t cksum = __rte_ipv6_udptcp_cksum(ipv6_hdr, l4_hdr); > cksum = ~cksum; /* * Per RFC 768: If the computed checksum is zero for > UDP, * it is transmitted as all ones * (the equivalent in one's > complement arithmetic). */ if (cksum == 0 && ipv6_hdr->proto == > IPPROTO_UDP) cksum = 0xffff; return cksum; } It is the highest level. It > calls an internal function and at the end it considers the protocol > number (with other words, the next header field of the IPv6 header) when > it handles UDP specific things, thus I think that this time it does not > cause any problem in the case of ICMPv6. > > This is the source code of the internal function: > > static inline uint16_t > __rte_ipv6_udptcp_cksum(const struct rte_ipv6_hdr *ipv6_hdr, const void > *l4_hdr) > { > uint32_t cksum; > uint32_t l4_len; > > l4_len = rte_be_to_cpu_16(ipv6_hdr->payload_len); > > cksum = rte_raw_cksum(l4_hdr, l4_len); > cksum += rte_ipv6_phdr_cksum(ipv6_hdr, 0); > > cksum = ((cksum & 0xffff0000) >> 16) + (cksum & 0xffff); > > return (uint16_t)cksum; > } Yes this is similar but in UDP/TCP case the UDP/TCP header is included in the checksum. l4_hdr points to the UDP/TCP header. l4_len is the payload length that is TCP/UDP header and the associated data. The pseudo header is done by rte_ipv6_phdr_cksum(). For ICMPv6 you would need to point l4_hdr at ICMP header. Even though ICMP is not really an L4 protocol. https://en.wikipedia.org/wiki/ICMPv6#Checksum
