Provided by: netsniff-ng_0.6.8-3_amd64 bug


       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

       -6, --ipv6
              Display IPv6 flows. That is  the  default  when  flowtop  is  started  without  any

       -T, --tcp
              Display  TCP  flows.  That  is  the  default  when  flowtop  is started without any

       -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

       -G, --no-geoip
              Don't  perform  GeoIP  lookup.  No  geographical information will be shown for flow

       -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.


              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  <>  and  Daniel  Borkmann


       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