|
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | USAGE EXAMPLE | CONFIG FILES | BUGS | LEGAL | HISTORY | SEE ALSO | AUTHOR | COLOPHON | COLOPHON |
FLOWTOP(8) netsniff-ng toolkit FLOWTOP(8)
flowtop - top-like netfilter TCP/UDP/SCTP/DCCP/ICMP(v6) flow tracking
flowtop { [options] }
flowtop is a top-like connection tracking tool that can run on an end
host or small home router. It is able to present TCP, UDP/UDP-lite,
SCTP, DCCP, and ICMP(v6) flows that have been collected by the
kernel's netfilter connection tracking framework, thus no packet
capturing in user space needs to be done.
flowtop is able to give you a quick overview of current connections
on your local system, e.g. for debugging purposes or to answer
questions like:
* If you access website X, what other connections are being
opened in
the background that I'm not aware of?
* What connections are active that pass one's router?
* I have this proprietary binary Y, to where does it connect?
* To which countries am I sending data?
* Are there any suspicious background connections on my machine?
* How many active connections does binary Y have?
* How long are connections active already?
* At which rate am I sending/receiving data?
The following information will be presented in flowtop's output:
* Application name and PID when run on local machine
* Reverse DNS for source and destination
* Geo-location information (country, city)
* Used protocols (IPv4, IPv6, TCP, UDP, SCTP, ICMP, ...)
* Flow port's service name heuristic
* Transport protocol state machine information
* Byte/packet counters (if they are enabled)
* Connection duration (if timestamping is enabled)
* Flow send/receive rate (if byte/packet counters are enabled)
In order for flowtop to work, netfilter must be active and running on
your machine, thus kernel-side connection tracking is active. If
netfilter is not running, you can activate it with iptables(8):
iptables -A INPUT -p tcp -m state --state ESTABLISHED -j ACCEPT
iptables -A OUTPUT -p tcp -m state --state NEW,ESTABLISHED -j
ACCEPT
or by loading the following kernel modules:
modprobe nf_conntrack_ipv4
modprobe nf_conntrack_ipv6
To dump byte/packet counters flowtop enables the sysctl(8) parameter
“net.netfilter.nf_conntrack_acct” via:
echo 1 > /proc/sys/net/netfilter/nf_conntrack_acct
and resets it to the previously set value on exit. These counters
will only be active on connections which were created after
accounting was enabled. Thus, to have these counters be active all
the time the parameter should be enabled after the system is up. To
automatically enable it, sysctl.conf(8) or sysctl.d(8) might be used.
To calculate the connection duration flowtop enables the sysctl(8)
parameter “net.netfilter.nf_conntrack_timestamp” via:
echo 1 > /proc/sys/net/netfilter/nf_conntrack_timestamp
and resets it to the previously set value on exit.
flowtop's intention is just to get a quick look over your active
connections. If you want logging support, have a look at netfilter's
conntrack(8) tools instead.
-4, --ipv4
Display IPv4 flows. That is the default when flowtop is started
without any arguments.
-6, --ipv6
Display IPv6 flows. That is the default when flowtop is started
without any arguments.
-T, --tcp
Display TCP flows. That is the default when flowtop is started
without any arguments.
-U, --udp
Display UDP and UDP-lite flows.
-D, --dccp
Display DCCP flows.
-I, --icmp
Display ICMP version 4 and version 6 flows.
-S, --sctp
Display SCTP flows.
-n, --no-dns
Don't perform hostname lookup. Only numeric addresses will be shown
for flow endpoints.
-G, --no-geoip
Don't perform GeoIP lookup. No geographical information will be shown
for flow endpoints.
-s, --show-src
Also show source information of the flow, not only destination
information.
-b, --bits
Show flow rates in bits per second instead of bytes per second.
-u, --update
The built-in database update mechanism will be invoked to get
Maxmind's latest database. To configure search locations for
databases, the file /etc/netsniff-ng/geoip.conf contains possible
addresses. Thus, to save bandwidth or for mirroring Maxmind's
databases (to bypass their traffic limit policy), different hosts or
IP addresses can be placed into geoip.conf, separated by a newline.
-t <time>, --interval <time>
Flow info refresh interval in seconds, default is 1s.
-v, --version
Show version information and exit.
-h, --help
Show user help and exit.
flowtop
Default ncurses output for flowtop that tracks IPv4, IPv6 flows for
TCP.
flowtop -46UTDISs
This example enables the maximum display options for flowtop.
Files under /etc/netsniff-ng/ can be modified to extend flowtop's
service resolution and lookup information.
* tcp.conf - TCP port/services map
* udp.conf - UDP port/services map
* geoip.conf - GeoIP database mirrors
With a fairly high rate of connection tracking updates, flowtop can
become unresponsive for short periods of time while scrolling. The
right fix would be to replace flowtop's connection management backend
with a better design with respect to the locking approach. This is
still on the "todo" list.
flowtop is licensed under the GNU GPL version 2.0.
flowtop was originally written for the netsniff-ng toolkit by Daniel
Borkmann. It is currently maintained by Tobias Klauser
<tklauser@distanz.ch> and Daniel Borkmann <dborkma@tik.ee.ethz.ch>.
netsniff-ng(8), trafgen(8), mausezahn(8), ifpps(8), bpfc(8),
astraceroute(8), curvetun(8), iptables(8), sysctl(8), sysctl.conf(8),
sysctl.d(8)
Manpage was written by Daniel Borkmann.
This page is part of the Linux netsniff-ng toolkit project. A
description of the project, and information about reporting bugs, can
be found at http://netsniff-ng.org/.
This page is part of the netsniff-ng (a free Linux networking
toolkit) project. Information about the project can be found at
⟨http://netsniff-ng.org/⟩. If you have a bug report for this manual
page, send it to netsniff-ng@googlegroups.com. This page was
obtained from the project's upstream Git repository
⟨git://github.com/netsniff-ng/netsniff-ng.git⟩ on 2017-07-05. If you
discover any rendering problems in this HTML version of the page, or
you believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a mail
to man-pages@man7.org
Linux 03 March 2013 FLOWTOP(8)
Pages that refer to this page: astraceroute(8), bpfc(8), curvetun(8), ifpps(8), mausezahn(8), netsniff-ng(8), trafgen(8)