Pablo Neira Ayuso a écrit :
GLAUME Vincent wrote:
Hi there,
I'm currently trying to figure out how the whole libnetfilter_conntrack
works, and more precisely the expect part of the lib.
My aim is to be able to create new expectation entries with this lib in
an application that would inspect packets (either coming from a
pcap-based sniffer or from netfilter via the nfqueue mechanism) : thus
I'd like to allow connections related to the inspected (and already
allowed) connections.
My various tests make me think that to create such an expectation entry,
a kernel module related to the master connection is required: am I right?
For instance, the "expect_create" app in the libnetfilter_conntrack
"utils" subdirectory works fine, unless I modify the destination port of
the master conntrack structure... then it's no longer related to the FTP
conntrack mechanism...
Same thing happens when using the conntrack app. from the conntrack-tools.
So, I'd like to know how to do this the right way, without coding the
whole inspection thing in a kernel module (if this is possible). Is
there any generic tcp conntrack system that could help here?
As I'm not too sure to fully understand the whole mechanism of expected
connection creation, any hint is welcome!
I hope this is not too confused... Thanks,
IIRC, this requires a couple of patches for the kernel to fully support
conntrack helpers in user-space, which seems to be what you need. So
this is not support until the appropriate patches go into the kernel.
Thank you for this hint, I'm going to dig it...
I wish I could understand why/how it works pretty well with the FTP
conntrack though!
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