Hi Gregoire,
please file a bug on https://github.com/ntop/nProbe 
<https://github.com/ntop/nProbe> and attach a pcap file for reproducing it

Regards Luca

> On 17 Dec 2015, at 15:21, [email protected] wrote:
> 
> Hello,
> 
> I want to test nprobe stable on CentOS6 (v.7.2.151211) and I have an issue 
> with nprobe and L2TP tunnelled traffic. Here is the command I launch :
> 
> [root@netflow-linux ~]# nprobe -i eth1 -d 60 -P /tmp/flows -D t -I sfr -T 
> "%IN_BYTES %IN_PKTS %L4_SRC_PORT %PROTOCOL %IPV4_SRC_ADDR %L4_DST_PORT 
> %IPV4_DST_ADDR %IPV6_SRC_ADDR %IPV6_DST_MASK %UPSTREAM_TUNNEL_ID 
> %DOWNSTREAM_TUNNEL_ID" -V 9 --smart-udp-frags -N 0 --tunnel
> 
> I'd expect to get records like
> "122|1|53|17|IP_IN_TUNNEL|13217|IP_IN_TUNNEL|::|0|000054B5|0000B5AB|
> 117|2|443|6|IP_IN_TUNNEL|53820|IP_IN_TUNNEL|::|0|00006304|0000BB56|
> "
> I get some of them, but most of my records are not correctly decapsulated and 
> I usually get records like that :
> 
> 52|1|30753|17|L2TP_IP|49752|L2TP_IP|::|0|00000000|00000000|
> 52|1|4560|17|L2TP_IP|34232|L2TP_IP|::|0|00000000|00000000|
> 
> As you can see, L4_SRC_PORT and L4_DST_PORT are correctly decapsulated. 
> However, I neither get the tunneled IP address or the tunnel informations (I 
> obfuscated IP informations, replacing them with IP_IN_TUNNEL and L2TP_IP). 
> ~75% of flows are concerned.
> 
> I am pretty sure the problem comes from the decapsulation and it's not a 
> false positive as if it was, src port and dest port would be 1701.
> 
> When I try to use it in debug mode I get a segfault (which I don't get 
> without the --tunnel option) :
> 
> [root@netflow-linux ~]# nprobe -i eth1 -d 60 -P /tmp/flows -D t -I sfr -T 
> "%IN_BYTES %IN_PKTS %L4_SRC_PORT %PROTOCOL %IPV4_SRC_ADDR %L4_DST_PORT 
> %IPV4_DST_ADDR %IPV6_SRC_ADDR %IPV6_DST_MASK %UPSTREAM_TUNNEL_ID 
> %DOWNSTREAM_TUNNEL_ID %UNTUNNELED_IPV4_SRC_ADDR" -V 9 --smart-udp-frags -N 0 
> --debug --tunnel
> 17/Dec/2015 16:19:38 [nprobe.c:3114] ERROR: Invalid nProbe license 
> (/etc/nprobe.license) [Missing license file]
> 17/Dec/2015 16:19:38 [nprobe.c:3121] ERROR: 
> *****************************************************
> 17/Dec/2015 16:19:38 [nprobe.c:3122] ERROR: **                                
>                  **
> 17/Dec/2015 16:19:38 [nprobe.c:3123] ERROR: **  Switching to DEMO MODE 
> (missing valid license) **
> 17/Dec/2015 16:19:38 [nprobe.c:3124] ERROR: **                                
>                  **
> 17/Dec/2015 16:19:38 [nprobe.c:3125] ERROR: **  Create your nProbe license at 
>                  **
> 17/Dec/2015 16:19:38 [nprobe.c:3126] ERROR: **       
> http://www.nmon.net/mklicense/            **
> 17/Dec/2015 16:19:38 [nprobe.c:3127] ERROR: **                                
>                  **
> 17/Dec/2015 16:19:38 [nprobe.c:3128] ERROR: 
> *****************************************************
> 17/Dec/2015 16:19:38 [nprobe.c:6508] ERROR: 
> ***************************************************************
> 17/Dec/2015 16:19:38 [nprobe.c:6509] ERROR: * NOTE: This is a DEMO version 
> limited to 25000 flows export.  *
> 17/Dec/2015 16:19:38 [nprobe.c:6510] ERROR: 
> ***************************************************************
> 17/Dec/2015 16:19:38 [plugin.c:166] No plugins found in ./plugins
> 17/Dec/2015 16:19:38 [plugin.c:174] Loading 22 plugins [.so] from 
> /usr/local/lib/nprobe/plugins
> datagramSourceIP 0.0.0.0
> datagramSize 48
> unixSecondsUTC 1450365578
> datagramVersion 5
> agentSubId 0
> agent 192.168.1.1
> packetSequenceNo 1084445
> sysUpTime 2429093100
> samplesInPacket 4
> startSample ----------------------
> sampleType_tag 0:2
> sampleType COUNTERSSAMPLE
> sampleSequenceNo 187645
> sourceId 0:1
> counterBlock_tag 2176:0
> skipping unknown counters_sample_element: 2176:0 len=0
> counterBlock_tag 568615:598
> skipping unknown counters_sample_element: 568615:598 len=0
> endSample   ----------------------
> unexpected end of datagram after sample 1 of 4
> datagramSourceIP 0.0.0.0
> datagramSize 48
> unixSecondsUTC 1450365578
> datagramVersion 5
> agentSubId 0
> agent 192.168.1.1
> packetSequenceNo 1084446
> sysUpTime 2429093100
> samplesInPacket 10
> startSample ----------------------
> sampleType_tag 0:1
> sampleType FLOWSAMPLE
> sampleSequenceNo 11443
> sourceId 0:2
> meanSkipCount 50
> samplePool 8912896
> dropEvents 0
> inputPort multiple 181563990
> outputPort 0
> flowBlock_tag 0:0
> skipping unknown flow_sample_element: 0:0 len=-2147483648
> Segmentation fault
> 
> When I compare with what I get in a pcap, I can see that in my pcap file I 
> almost don't get any packet
> 
> Is there a performance issue (it doesn't seem so, CPU stays low) ? Is there a 
> fix somewhere, or did I miss something ?
> 
> Thank you very much,
> Regards,
> Grégoire
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