How to make passive FTP server connections
working on Debian
If you're setting a new server based Linux server and you want to
have an FTP server which is located behind a firewall or some kind
of router I've myself experienced this on Debian Lenny powered
server.
The exact kernel of the server is as follow:
Linux debian 2.6.26-2-amd64 #1 SMP Thu Sep 16 15:56:38 UTC
2010 x86_64 GNU/Linux
Until some time ago, everytime I experienced this kind of problem
on a Linux router the fix was done through loading the kernel
module
ip_c However this kind of fix is no longer working for
some reasons I'm not completely aware.
The Linux kernel has adopted a new kernel module:
/lib/modules/2.6.26-2-amd64/kernel/net/netfilter/nf_conntrack_ftp.ko
Which until some time apparently takes care for the connection
tracking of passive FTP connections.
Therefore to currently to enable the passive FTP connections to
your FTP daemon on Linux you need to load and enable the
nf_conntrack debian:~# echo nf_conntrack_ftp >>
/etc/modules
debian:~# modprobe nf_conntrack_ftp
Now your FTP passive connections should work fine.