packets being dropped in IP stack but no error counts incrementing?

packets being dropped in IP stack but no error counts incrementing?

[Chris Friesen]

I've been doing some testing on 2.4.18 and I'm seeing an interesting problem.

I have a test tool that simulates bursty UDP traffic by sending a bunch of
messages and then delaying a while.   If I leave the receiving udp socket at its
normal size, then I can get a significant number of messages just vanishing
between the ethernet driver and the userspace socket.  The driver rx count shows
that all packets were received, but the userspace program doesn't get all of
them.  netstat/ifconfig/iproute2 rx dropped counts do not increase.

Is this design intent, are we messing a counter increment when dropping packets,
or am I not looking at the right counter for these numbers?

Thanks,

Chris

-- 
Chris Friesen                    | MailStop: 043/33/F10  
Nortel Networks                  | work: (613) 765-0557
3500 Carling Avenue              | fax:  (613) 765-2986
Nepean, ON K2H 8E9 Canada        | email: cfriesen@nortelnetworks.com

Re: packets being dropped in IP stack but no error counts incrementing?

[Ben Greear]

I am not sure the UDP drop counters are available.  If you do
find them, I'm interested in them too!

Chris Friesen wrote:

> I've been doing some testing on 2.4.18 and I'm seeing an interesting problem.
> 
> I have a test tool that simulates bursty UDP traffic by sending a bunch of
> messages and then delaying a while.   If I leave the receiving udp socket at its
> normal size, then I can get a significant number of messages just vanishing
> between the ethernet driver and the userspace socket.  The driver rx count shows
> that all packets were received, but the userspace program doesn't get all of
> them.  netstat/ifconfig/iproute2 rx dropped counts do not increase.
> 
> Is this design intent, are we messing a counter increment when dropping packets,
> or am I not looking at the right counter for these numbers?
> 
> Thanks,
> 
> Chris
> 
> 


-- 
Ben Greear <greearb@candelatech.com>          <Ben_Greear@excite.com>
President of Candela Technologies Inc      http://www.candelatech.com
ScryMUD:  http://scry.wanfear.com     http://scry.wanfear.com/~greear

Re: packets being dropped in IP stack but no error counts incrementing?

[Chris Friesen]

Ben Greear wrote:
> 
> I am not sure the UDP drop counters are available.  If you do
> find them, I'm interested in them too!

Well, I've found an entry in /proc that has some information.  The entry is:

/proc/net/softnet_stat


The first two columns are:

total
dropped


In this case, dropped is the number of messages dropped due to the softnet_data
queue being full.  I have actually hit this under high load.

I'm still looking for socket/protocol specific stuff though.

Chris

-- 
Chris Friesen                    | MailStop: 043/33/F10  
Nortel Networks                  | work: (613) 765-0557
3500 Carling Avenue              | fax:  (613) 765-2986
Nepean, ON K2H 8E9 Canada        | email: cfriesen@nortelnetworks.com

Re: packets being dropped in IP stack but no error counts incrementing?

[andrew may]

On Wed, Jun 05, 2002 at 01:18:09PM -0400, Chris Friesen wrote:
> Ben Greear wrote:
> > 
> > I am not sure the UDP drop counters are available.  If you do
> > find them, I'm interested in them too!
 

You are using netstat -s/cat /proc/net/snmp and ifconfig/cat /proc/net/dev