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Re: [Openvpn-users] Incorrect tcp and udp checksums on packets from gateway to vpn clients (solved)

  • Subject: Re: [Openvpn-users] Incorrect tcp and udp checksums on packets from gateway to vpn clients (solved)
  • From: "Giampaolo Carmagnani" <giampaolo@xxxxxxxxx>
  • Date: Tue, 3 Apr 2007 17:19:03 -0300

On 4/3/07, Georg Graf <g.graf@xxxxxxxx> wrote:
> Hi!
> Giampaolo Carmagnani wrote:
> > --ip-win32 method
> >     When using --ifconfig on Windows, set the TAP-Win32 adapter IP
> > address and netmask using method. Don't use this option unless you are
> > also using --ifconfig.
> Giampaolo, I'm afraid you misunderstood the cause of my posting. I am
> not having any fragmentation problems.

Ohhh OK.
I was thinking is a fragmentation issue because I already have
problems with fragmentation and TCP checksums (the packet not arrive
complete at all...)

> The problem was: The pyhsical Network Card attached to the server bridge
> was by default doing TCP checksums in hardware (Intel Gigabit Ethernet
> Adapter, em in FreeBSD Terms), to take this workload off the kernel. So
>   the packets generated by the server host had no valid TCP checksum on
> them, entered the bridge without seeing the Intel Card and arrived at my
> VPN Clients with no valid checksum on them.
> "ifconfig em0 -txcsum" solved the problem. Now the kernel generates the
> checksums for all packets, they are valid when they enter the bridge and
> the communication works fine.
Happy to know

Good Job


Giampaolo Carmagnani

> I'll report this issue to the FreeBSD People.
>    George
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