Provided by: netsniff-ng_0.6.0-1build2_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

       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.


       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