Re: [libnetfilter_log] fix bug in race condition of calling nflog_open from different threads at same time

[Pablo Neira Ayuso <pablo@netfilter.org>]

Hi,

On Tue, Apr 30, 2024 at 06:25:47PM +0300, Evgen Bendyak wrote:
> In my firewall based on nftables, I use several different log
> subsystem groups for packet capturing. This setup is used for a server
> providing access to a large number of internet clients, with each
> client in a separate VLAN. To expand the number of virtual networks,
> QinQ technology is utilized. One group captures ARP packets (in
> certain situations for new clients) coming from the network, for
> further analysis. Another group captures DHCP packets sent by clients.
> Also present groups for other various subsystems. These are not
> heavily loaded groups in terms of packet volume. In the application
> where this is processed, each group is handled by its own subsystem.
> Each subsystem creates its own thread, where the relevant group for
> that service is opened. Sometimes, after a restart, one group or
> another would fail to function. It appeared as if data was coming
> through the netlink socket, but when nflog_handle_packet was called,
> the callback would not trigger. That's when I began investigating what
> was wrong.

Oh I see, this is log not queue. For some reason I considered this was
the queue subsystem instead.

Thanks for explaining.