Packets lost: Softirq

Packets lost: Softirq

[Vasantha Kumar Puttappa]

Hi All,
 Please somebody guide me here. I desparatley need help regarding this
issue. ( plz do "reply to all")

 I am tracking all udp packets (in particular, SIP based UDP packets)that
goes through the iptables using LOG mechanism.
 I use the following command,
     iptables -A INPUT -p udp -j LOG --log-level-4.
     iptables -A FORWARD -p udp -j LOG --log-level-4

  In addition, i also run 'Ethereal' to make sure that all the packets
captured goes through the iptables as well.

  Here is the problem,
    Sometimes, a random number of packets doesnot go through IPtables and
  they are completely lost. Although, I can see those lost packets in
Ethereal. I tried increasing the backlog queue and ip_queue length, but
still no use.

   I am using Netgear's wireless network card (WG511, made in taiwan).
   Device driver: Prism54
   firmware: isl3890
   Kernel verison-- 2.6.11-6mdk

  Let me give you more insight into what I am trying do.

 I have a vitrual network interface and 2 physical network interface (one
Ethernet based, and other 802.11 based). The virtual network interface
dynamically binds to any one of the above physical interfaces for packet
transmission. The issue of packet loss occurs **only** during link
switching.

I feel that the following issues might be the possible reasons for the
packet loss.

1. Due to missing soft_IRQ interrupt for packets and hence packet loss ( i
have no proof to back this)
2. Due to incompatible wireless device driver.

Somebody please guide me. How do I findout the cause of this.

 Thank you,

  Regards
  Vasanth

Re: Packets lost: Softirq

[Eric Dumazet]

Vasantha Kumar Puttappa a écrit :
> Hi All,
>  Please somebody guide me here. I desparatley need help regarding this
> issue. ( plz do "reply to all")
> 
>  I am tracking all udp packets (in particular, SIP based UDP packets)that
> goes through the iptables using LOG mechanism.
>  I use the following command,
>      iptables -A INPUT -p udp -j LOG --log-level-4.
>      iptables -A FORWARD -p udp -j LOG --log-level-4
> 
>   In addition, i also run 'Ethereal' to make sure that all the packets
> captured goes through the iptables as well.
> 
>   Here is the problem,
>     Sometimes, a random number of packets doesnot go through IPtables and
>   they are completely lost. Although, I can see those lost packets in
> Ethereal. I tried increasing the backlog queue and ip_queue length, but
> still no use.
> 
>    I am using Netgear's wireless network card (WG511, made in taiwan).
>    Device driver: Prism54
>    firmware: isl3890
>    Kernel verison-- 2.6.11-6mdk
> 
>   Let me give you more insight into what I am trying do.
> 
>  I have a vitrual network interface and 2 physical network interface (one
> Ethernet based, and other 802.11 based). The virtual network interface
> dynamically binds to any one of the above physical interfaces for packet
> transmission. The issue of packet loss occurs **only** during link
> switching.
> 
> I feel that the following issues might be the possible reasons for the
> packet loss.
> 
> 1. Due to missing soft_IRQ interrupt for packets and hence packet loss ( i
> have no proof to back this)
> 2. Due to incompatible wireless device driver.
> 

netdev CCed

3) packets are going normally through iptables, but the '-j LOG' is flooded 
and syslog miss some of them.

Just do a : iptables -nvL INPUT

and check packets counters : they should match ethereal ones :)

-j LOG is not designed for logging all packets, just some of them :)