Re: [Ethereal-users] Why am I seeing lots of packets with incorrect UDP checksums?

[Guy Harris <guy@xxxxxxxxxxxx>]

Hoehle, Joerg-Cyril wrote:

> Note that the IP checksum is reported correct with my laptop:
> lspci: Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ (rev 10)
> I'd have expected a hardware able to fix the TCP checksum to also manage the IP one. How comes?

I don't know.  You might want to ask whoever maintains the driver for 
those adapters.

> [Enhancement request #2 follows:]
> Sadly, this preferences setting deactivates checksums even for
> incoming packets, which is not good.  A single switch "*outgoing*
> checksums done in HW, please don't check" would be preferable,
> possibly per interface.

A mechanism for determining whether a packet is incoming or outgoing 
would be a requirement for this.  Unfortunately, there isn't yet such a 
mechanism in libpcap/WinPcap, so, for captures done with 
libpcap/WinPcap-based applications (such as Wireshark), that's not doable.