WinSock2 on Windows XP and ICMPv6

I am trying to programatically send out ICMPv6 echo requests (ping6) using WinSock2. The ICMPv6 checksum is calculated based on the whole IPv6 packet that will be sent out. For that reason - from what I understand - the OS (kernel?) is supposed to calculate it and write it into the ICMPv6 header when sending the packet.

This works very well on a SUSE Linux Enterprise Server 11, however, Windows XP does not seem to do this. It leaves the checksum to what I set it by default (zero, I analyzed this using Wireshark), thus the 开发者_如何学编程receiving end will discard it and not reply.

IPv6 is correctly set up on this WinXP machine. With the help of Wireshark I even found out that it responds correctly to ICMPv6 pings from the SUSE Linux server, sent using the very same code. So it cannot be that Windows XP doesn't support ICMPv6. However, I wonder whether WinSock2 under Windows XP does.

The WinSock2 API does provide the IPPROTO_ICMPV6 protocol which I create my raw socket for. Is there any special socket option I need to set for the ICMPv6 checksum to be calculated automatically, or are there any other tricks?

Most probable reason for the behavior you describe is checksum offloading. It means, checksum calculation might be delegated to networking hardware, so that sniffed packet doesn't contain the correct checksum value. Refer to http://www.wireshark.org/docs/wsug_html_chunked/ChAdvChecksums.html or to http://en.wikipedia.org/wiki/Transmission_Control_Protocol#Checksum_offload