Wireshark mailing list archives
Re: Incorrect checksum calculation for UDP packet with ipv6 extension header
From: João Valverde via Wireshark-dev <wireshark-dev () wireshark org>
Date: Fri, 9 Jul 2021 16:20:48 +0100
Hi,The final destination address for the packet is 505:505:505:505:505:505:505:505. Why would you think it is not?
When the kernel is routing the packet (at 4ea1:2222:2222::11) it does not look at the UDP checksum to accept/reject it.
Regards, João On 7/8/21 7:56 PM, Hupfer, Michael via Wireshark-dev wrote:
Please see packet 4 of the atached captureIn my opinion checksum 0xc343 is actually correct, since it is calculated using the final destination address 4ea1:2222:2222::11, but wireshark reports 0x2e12 as correct, which is the result of the checksum calculation if the address from the extension header 505:505:505:505:505:505:505:505 is used.Please refer to RFC 2460: 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. In addition, the Linux kernel accepts the UDP packet. 3.4.6 (v3.4.6-0-g6357ac1405b8)Compiled (64-bit) with Qt 5.15.2, with libpcap, with GLib 2.52.3, with zlib1.2.11, with SMI 0.4.8, with c-ares 1.15.0, with Lua 5.2.4, with GnuTLS 3.6.3and PKCS #11 support, with Gcrypt 1.8.3, with MIT Kerberos, with MaxMind DBresolver, with nghttp2 1.39.2, with brotli, with LZ4, with Zstandard, withSnappy, with libxml2 2.9.9, with QtMultimedia, with automatic updates usingWinSparkle 0.5.7, with AirPcap, with SpeexDSP (using bundled resampler), withMinizip. Running on 64-bit Windows 10 (2009), build 19043, with Intel(R) Core(TM)i7-8665U CPU @ 1.90GHz (with SSE4.2), with 32483 MB of physical memory, withlocale German_Germany.utf8, with light display mode, without HiDPI, with Npcapversion 1.31, based on libpcap version 1.10.1-PRE-GIT, with GnuTLS 3.6.3, withGcrypt 1.8.3, with brotli 1.0.2, without AirPcap, binary plugins supported (21loaded). Built using Microsoft Visual Studio 2019 (VC++ 14.28, build 29910). ___________________________________________________________________________ Sent via: Wireshark-dev mailing list <wireshark-dev () wireshark org> Archives: https://www.wireshark.org/lists/wireshark-dev Unsubscribe: https://www.wireshark.org/mailman/options/wireshark-dev mailto:wireshark-dev-request () wireshark org?subject=unsubscribe
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Current thread:
- Incorrect checksum calculation for UDP packet with ipv6 extension header Hupfer, Michael via Wireshark-dev (Jul 09)
- Re: Incorrect checksum calculation for UDP packet with ipv6 extension header João Valverde via Wireshark-dev (Jul 09)