Hello,
On Tue, Feb 29, 2000 at 11:08:36AM -0500, TenThumbs wrote:
> Chris Dunlop wrote:
> > There seems to be a problem with TCP in 2.2.15pre10. The same problem occurs
> > in at least 2.2.14pre5, 2.2.14pre9 and 2.2.15pre10.
> >
> > Following is the tail end of a tcpdump of an attempt to pick up the latest
> > netscape communicator using ncftpget. The command line used was:
> >
> > ncftpget -F ftp://205.188.247.193/pub/communicator/english/4.72/windows/windows95_or_nt/complete_install/cc32e472.exe
> >
> > Everything looks fine until the packet where we issue the PASV command,
> > but then we don't seem to see their ack/reply. We issue the same packet
> > again, and they try sending their reply a few times, but we seem to be
> > missing it.
> >
> > This same transfer worked without problems under 2.0.35.
>
> Either switch to active-mode ftp or turn off tcp_timestamps. Netscape has been
> screwed up this way for a while; probably a broken firewall.
>
> Still, the server does send packets which the kernel ignores. I wonder if this
> is right?
I've repeated the test and found that our side sees the packets with a broken
TCP checksum. The real reason is a broken NAT device in Netscape which is
unable to properly calculate the checksum of a packet with rewritten PASV
address/port in presence of timestamps.
Our kernel behaves absolutely correct: it logs and drops the broken packets.
Best regards
Andrey V.
Savochkin
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This archive was generated by hypermail 2b29 : Tue Mar 07 2000 - 21:00:11 EST