Am 17.04.2016 um 04:09 schrieb Marcelo Ricardo Leitner:
Cc'ing netfilter@ too
Thread:
https://lists.fedoraproject.org/archives/list/kernel@xxxxxxxxxxxxxxxxxxxxxxx/thread/CLNQ6O6OGNEJAFFSNV56KU6P2JAPM5YU/
Em 16-04-2016 10:52, Reindl Harald escreveu:
Am 15.04.2016 um 10:16 schrieb Reindl Harald:
Am 14.04.2016 um 23:53 schrieb Marcelo Ricardo Leitner:
Otherwise it won't be able to expect the new connection
sounds reasonable, on the other side the client yesterday had troubles
to make passive ftp connections with "connection refused" as far as
the
admin was able to tell on the phone
It could be that the drop happened and an auxiliary connection was
attempted before the retransmission of the 227 reply, so your firewall
didn't know about it and actively blocked the connection. If it had
silently dropped the new connection request, the client probably would
retransmit the SYN after a bit.
Now why the cameras are triggering it, good question
not the cameras - a ordinary client with filezilla, that one with 227 in
his IP address, the cameras blow their images without any problem on the
FTP server
maybe i made it not clear enough:
there is no "my firewall" between that is just iptables directly on the
machine running pure-ftpd and so it's killing outgoing localhost traffic
- that is very weird
Okay but expected :) because even if conntrack is running on the system
itself that is running the service, it ignores that fact and still acts
like just a man-in-the-middle.
but partial packets on the local system? :-)
So you can still reproduce it?
not in a way that would make it easy to debug, some days are log floods
and that for years now and most time there is nothing - until last week
i thought that would be something to attackers related but then i had a
customer with borken PASV ftp and his IP address 100 times in the log
with that message
If so, I don't see another way to debug
this but to unload nf_conntrack_ftp and take a traffic capture without
limiting the packet size (don't use -s option), because I'm afraid that
otherwise conntrack will drop the packet and we won't even see it in the
capture.
Look for a packet containing a "227 " in the beginning of TCP payload.
That should be our guy.
Feel free to send it only to my email if you prefer.
hmm - if i could reproduce it in a way "i want it now" and somewhere
else than a production server
Unfortunately the pr_debug()s available on that area aren't much helpful
for this problem.
And which kernel is this?
i have always the latest Fedora kernel running
4.4.7-300.fc23.x86_64
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