I have wireshark-1.2.15-2.el62.1.x8664.rpm installed on CentOS. I was hoping to see a command like 'wireshark', but couldnt find it. How do i launch wireshark?
Article on how to install and use Wireshark on Debian 9 / Ubuntu 16.04 / 17.10. Wireshark is free and open source, GUI based Network packet analyzer for Linux and Windows systems. Installing Wireshark under CentOS If you wish to use the free and open-source (FOSS) network packet analyzer Wireshark on a CentOS Linux system, e.g., CentOS 7, you can install the command line interface (CLI) version of the software, TShark, with yum install wireshark.
After querying the rpm, following components are installed. How do i launch the typical wireshark UI?/usr/sbin/capinfos/usr/sbin/dftest/usr/sbin/dumpcap/usr/sbin/editcap/usr/sbin/mergecap/usr/sbin/randpkt/usr/sbin/rawshark/usr/sbin/tethereal/usr/sbin/text2pcap/usr/sbin/tsharkUPDATE: I needed to install wireshark-gnome for the UI.
I am attempting to capture approx 20mbit/sec worth of traffic continuously with tshark. If I capture packets with tshark on CentOS 6.5 I get around 4% to 66% packets dropped. If I do the same thing on CentOS 7 it never reports any dropped packets. I've actually tried to get it to drop packets by doing crazy stuff like outputting large amounts of traffic to xml.
As far as I can tell it is not dropping packets. My question is, does CentOS 7 have some sort of feature that makes dropping packets impossible? Or is it dropping packets and not telling me?As an example, I execute commands like this: tshark -i ens224 -c 100000 -w /tmp/delme.pcaptshark -i ens224 -c 100000 -T pdml /tmp/delme.pcapFor the first command CentOS 6 reports 4% dropped packets, CentOS 7 reports none. For the second command CentOS reports 66% dropped packets but CentOS 7 reports none.Note that both machines are running tshark 1.12.7 compiled from source. My question is, does CentOS 7 have some sort of feature that makes dropping packets impossible?No, but it has two features that make dropping packets far less likely:.
a kernel version that includes TPACKETV3 for PFPACKET sockets;. a libpcap version that uses TPACKETV3 for PFPACKET sockets.Libpcap uses PFPACKET sockets to capture on Linux 2.2 and later (Linux 1.x and 2.0 didn't have PFPACKET sockets).
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The original PFPACKET sockets delivered packets using the regular socket mechanisms, meaning libpcap (or any other program capturing traffic) had to make one recvmsg call on that socket for every packet. This was more expensive than, for example, the way the BPF mechanism on.BSD and OS X works, where multiple packets are delivered on every read, so, with a high level of traffic, fewer system calls are made.Linux 2.4, I think, introduced the 'turbopacket' mechanism (that's what the 'T' in 'TPACKET' stands for - 'turbo'), which provides a memory-mapped buffer shared by the kernel and userland. With that, fewer copies are needed when delivering packets, and the packet-reading loop in userland can process multiple packets per wakeup (to wait for packets to arrive, userland makes a select, poll, or epoll call). Unfortunately, that mechanism provided a ring of fixed-size buffers, and libpcap has to choose a size big enough for the largest possible packet. Earlier versions picked packets that were the same size as the snapshot length provided, i.e. Probably 64K-1 for the version of Wireshark you're using, which is quite wasteful - the buffer ends up not having enough slots for packets to avoid overrun.
Some later versions attempted to use the MTU to determine the slot size, but it can't always do that, and even if it can that can be wasteful.In some 3.x version (3.6?), TPACKETV3, a significantly different turbopacket mechanism, was added. It's more like BPF, in that a buffer doesn't hold one packet, it can have multiple packets packed into it. This makes a lot better use of memory for capturing, and a lot fewer packets get dropped.