Visit Jeremy's Blog.
Go Back > Forums > Linux Forums > Linux - Software > Linux - Kernel
User Name
Linux - Kernel This forum is for all discussion relating to the Linux kernel.


  Search this Thread
Old 10-05-2009, 03:23 PM   #1
LQ Newbie
Registered: Oct 2009
Posts: 1

Rep: Reputation: 0
Question How to tell whether kernel is dropping UDP packets (or size of used receive buffer)?

I have an application that is receiving UDP (datagram) packets. I have a socket and have specified some (512K) size for its receive buffer.

I am receiving the packets at some rate, but I want to know whether I am catching up or not. Hence, I would like to find out, from which the application, either whether the kernel is dropping incoming UDP packets (due to me not catching up) or at least the size of the receive buffer used/free (I understand that my receive buffer can be used by multiple backloged UDP packets, is that correct?).

If it matters, I can arrange for my application to run as root.


- Igor
Old 10-09-2009, 05:57 AM   #2
Registered: Sep 2009
Distribution: Fedora, Red Hat
Posts: 52

Rep: Reputation: 18
If you want to see if the netfilter module drops a package you can put "iptables -A MYRULES -j LOG" at the end of your fw chain. This will write a log everytime a package is dropped. to You can also run a "tcpdump -v udp" to see the current UDP traffic.

To see the size of the Maximum Receive Window:

sysctl -a|grep rmem_max

I must say, i don't know how to see the usage of that buffer.
Old 10-15-2009, 09:26 AM   #3
LQ Newbie
Registered: Aug 2006
Location: Chicago
Distribution: Debian
Posts: 11

Rep: Reputation: 0
I would use Wireshark or snort to sniff the traffic


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Cannot Receive UDP Multicast Packets from Windows chewygumstix Linux - Networking 1 12-10-2008 03:47 PM
Questions regarding UDP Buffer Size in 2.4.20-31.9smp crazy_abt_linux Programming 1 04-25-2006 02:16 PM
UDP Buffer size Problems crazy_abt_linux Programming 1 04-24-2006 11:29 AM
how to increase serial receive email buffer size? HZC Programming 0 02-14-2005 11:32 PM
How to receive UDP and ICMP packets, by one UDP socket(PMTUD) myself_rajat Linux - Networking 0 05-28-2004 06:43 AM > Forums > Linux Forums > Linux - Software > Linux - Kernel

All times are GMT -5. The time now is 12:05 AM.

Main Menu
Write for LQ is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
Facebook: linuxquestions Google+: linuxquestions
Open Source Consulting | Domain Registration