a command line packet analyzer

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9
votes
1answer
1k views

what level of the network stack does tcpdump get its info from?

As I was trying in vain to fix a faulty ethernet controller here, one thing I tried was running tcpdump on the machine. I found it interesting that tcpdump was able to detect that some of the ICMP ...
1
vote
2answers
2k views

How to modify the output of tcpdump to be human-readable?

I have a tcpdump command: tcpdump -i wlan0 dst port 80 and ! dst 192.168.1.201 and ! src 192.168.1.201 -vvv -s0 -w proba.txt Which gives the following output: root@SERVER:/tmp# egrep "GET|Host:" ...
4
votes
1answer
1k views

How can I run tcpdump from a Python script without AppArmor complaining?

For inconvenient reasons going beyond the scope of this question, I have to run tcpdump from within a Python script. I currently just call subprocess.Popen(['tcpdump', ...) and everything works just ...
2
votes
1answer
457 views

How to know the number of messages received in a message queue at a point of time

I have a implementation where the hardware dispatches 300 packets every second to a host application through DMA transfer and then to the host application's message queue. When packets are sent at ...
7
votes
1answer
5k views

Buffer size for capturing packets in kernel space?

Going through the man page of tcpdump, it seems kernel can drop the packets if the buffer is full. I was wondering if: that size is configurable and/or where can I see the size for my distro? From ...
2
votes
1answer
989 views

Is it possible to capture all network traffic using tcpdump?

I have 3 computers on the same sub-net. Computer A and B are communicating with each other (ping, telnet, etc.). I'd like to see the packets between A and B on computer C. Is it possible to do this ...
8
votes
3answers
7k views

How to process/pipe TCPDUMPs output in realtime

If I want to tcpdump DNS requests by clients (on an OpenWrt 10.04 router), then I root@ROUTER:/etc# tcpdump -n -i br-lan dst port 53 2>&1 tcpdump: verbose output suppressed, use -v or ...
0
votes
2answers
737 views

Understanding tcpdump output on a linux router

My router has an atm0 interface and a VLAN (atm0.1) interface, atm0.1 has the WAN IP address. When using tcpdump -i atm0, the packets captured are only outgoing packet (LAN to WAN). 05:34:19.504895 ...