snort seems to stop working after first hit of drop rule

[Stefan Mayer <stefan.mayer () usaneers de>]

Hi everyone.

I am using ubuntu 18.04 lts, and also the latest snort version from apt-get, Version 2.9.7.0 GRE (Build 149). It is 
running inline, calling
/usr/sbin/snort -A console -Q -c /etc/snort/snort.conf -i eno1:enp3s0 -N

I set up the snort.conf, setting  $HOME_NET to 10.10.10.0/25 and disabling all rules except local.rules, with the 
following content:
alert  udp any any -> $HOME_NET 30501 (msg:"packet detected"; sid:10000003; rev:1; content:"|45670123|"; depth:4;)

The result is:
02/21-18:11:48.115016  [**] [1:10000003:1] packet detected [**] [Priority: 0] {UDP} 10.10.10.99:30400 -> 
10.10.10.16:30501

At the receiving end, the packets still arrive as they are supposed to. So far, so good.

After changing the rule to
drop  udp any any -> $HOME_NET 30501 (msg:"packet detected"; sid:10000003; rev:1; content:"|45670123|"; depth:4;)

The result is:
02/21-18:12:42.978438  [Drop] [**] [1:10000003:1] packet detected [**] [Priority: 0] {UDP} 10.10.10.99:30400 -> 
10.10.10.16:30501

Once. For the first packet that matches. After that, the traffic on udp stops arriving at the target, the only thing 
still passing the bridge is a ping. All udp traffic, either matching the rule or missing it, is lost, until I restart 
snort.
Changing the rule to sdrop does not help, either.

How can I resolve this issue? Thanks.

Stefan

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