Troubles with 'em' driver and UDP packets

[Vaidas Damoševičius]

If I start freeradius under high load, packets doesn't reach the destination - on sender side I see packets passing out (with tcpdump), on receiver side tcpdump "see" only part of these packets - some of them are missing.

> On 20 Mar 2015, at 11:49, Olivier Cochard-Labbé <olivier at cochard.me> wrote:
> 
> On Fri, Mar 20, 2015 at 10:23 AM, Vaidas Damoševičius <vd at par.lt <mailto:vd at par.lt>> wrote:
> Hello,
> 
> ​Hi,
> ​ 
> 
> I have 2 boxes with FreeBSD 10.1-RELEASE/amd64 and "Intel(R) PRO/1000 Network Connection 7.4.2" NIC's directly connected to each other. I noticed strange problem - I'm loosing small UDP packets under high load. I've tried to test it with iperf and got the following:
> 
> ---
> 
> vd at v0s4:~ % iperf3 -u -c 1.2.3.4
> Connecting to host 1.2.3.4, port 5201
> [  4] local 1.2.3.3 port 64254 connected to 1.2.3.4 port 5201
> [ ID] Interval           Transfer     Bandwidth       Total Datagrams
> [  4]   0.00-1.01   sec   120 KBytes   976 Kbits/sec  15
> [  4]   1.01-2.01   sec   128 KBytes  1.05 Mbits/sec  16
> [  4]   2.01-3.01   sec   128 KBytes  1.05 Mbits/sec  16
> [  4]   3.01-4.01   sec   128 KBytes  1.05 Mbits/sec  16
> [  4]   4.01-5.01   sec   128 KBytes  1.05 Mbits/sec  16
> [  4]   5.01-6.01   sec   128 KBytes  1.05 Mbits/sec  16
> [  4]   6.01-7.01   sec   128 KBytes  1.05 Mbits/sec  16
> [  4]   7.01-8.00   sec   128 KBytes  1.05 Mbits/sec  16
> [  4]   8.00-9.01   sec   128 KBytes  1.05 Mbits/sec  16
> [  4]   9.01-10.01  sec   128 KBytes  1.05 Mbits/sec  16
> - - - - - - - - - - - - - - - - - - - - - - - - -
> [ ID] Interval           Transfer     Bandwidth       Jitter    Lost/Total Datagrams
> [  4]   0.00-10.01  sec  1.24 MBytes  1.04 Mbits/sec  0.325 ms  0/159 (0%)
> [  4] Sent 159 datagrams
> 
> 
> 
> ​The result display a Lost/Total ratio of 0/159: Where do you see missing UDP packets ?
> By default iperf send only 1 Mbit/sec in UDP mode: I didn't see any problem on these stats.
> 
> Regards,
> 
> Olivier
> 
> 
> ​