The UDP pseudo-header use IPv6 DA for UDP checksum, not look into segment list.
Steps to reproduce What is the current bug behavior? Wireshark will validate the checksums of several protocols, e.g.: IP, TCP, UDP. So I figured, this change is not right, based on RFC2460.
#UDP CHECKSUM CALCULATOR UPDATE#
This modification is happened in Commit ca43dace 'IPv6: Update SRH dissection to RFC8754'. But the logic is also rewritten for pinfo->dst - from segment in 3.2.4 to original IPv6 dst in 3.4.0. I looked into 3.4.0 wireshark code, find that in file packet-ipv6.c, the function dissect_routing6_srh was rewritten for RFC8754(compared to version 3.2.4 ,where code is based on rfc draft). Checksum Calculation: UDP Checksum calculation is similar to TCP Checksum computation. It is not delivered to the wrong protocol. If this value is changed during transmission, the checksum calculation at the receiver will detect it and UDP drops the packet. Scapy is right, so is the wireshark 3.2.4. The value of the protocol field for UDP is 17. the function that I found needs to be called with an array, so should I send this function my 6 bytes. So I found this function that takes an array and returns the Checksum, but I have two small questions: UDP layer has 8 bytes: 2 source port, 2 destination port, 2 length and 2 checksum. So the IPv6 DST used in UDP pseudo-header supposed to be the first segment in segment list in SRv6, a.k.a segment. To do this, I need to calculate my UDP layer Checksum. If the IPv6 packet contains a Routing header, the Destination Address used in the pseudo-header is that of the final destination.At the originating node, that address will be in the last element of the Routing header at the recipient(s), that address will be in the Destination Address field of the IPv6 header. Then I check the RFC 2460 to make sure the UDP checksum calculation is in the right place. I check the packet in scapy, it show the checksum is right. The IPv6 + SRH + UDP packet will validate the UDP checksum when check the option "Validate the UDP checksum if possible".Ĭurrently, when I update my wireshark version from 3.2.4 to 3.4.0, one of my SRv6 packet shows UDP checksum is wrong, which was right before.
0 kommentar(er)
