ss

SS(8)                       System Manager's Manual                      SS(8)

NAME
       ss - another utility to investigate sockets

SYNOPSIS
       ss [options] [ FILTER ]

DESCRIPTION
       ss  is  used  to  dump socket statistics. It allows showing information
       similar to netstat.  It can display more  TCP  and  state  informations
       than other tools.

OPTIONS
       When no option is used ss displays a list of open non-listening sockets
       (e.g. TCP/UNIX/UDP) that have established connection.

       -h, --help
              Show summary of options.

       -V, --version
              Output version information.

       -H, --no-header
              Suppress header line.

       -n, --numeric
              Do not try to resolve service names.

       -r, --resolve
              Try to resolve numeric address/ports.

       -a, --all
              Display both listening and non-listening  (for  TCP  this  means
              established connections) sockets.

       -l, --listening
              Display only listening sockets (these are omitted by default).

       -o, --options
              Show timer information. For tcp protocol, the output format is:

              timer:(<timer_name>,<expire_time>,<retrans>)

              <timer_name>
                     the  name  of  the  timer,  there  are five kind of timer
                     names:

                     on: means one of these timers:  tcp  retrans  timer,  tcp
                     early retrans timer and tail loss probe timer

                     keepalive: tcp keep alive timer

                     timewait: timewait stage timer

                     persist: zero window probe timer

                     unknown: none of the above timers

              <expire_time>
                     how long time the timer will expire

              <retrans>
                     how many times the retran occurs

       -e, --extended
              Show detailed socket information. The output format is:

              uid:<uid_number> ino:<inode_number> sk:<cookie>

              <uid_number>
                     the user id the socket belongs to

              <inode_number>
                     the socket's inode number in VFS

              <cookie>
                     an uuid of the socket

       -m, --memory
              Show socket memory usage. The output format is:

              skmem:(r<rmem_alloc>,rb<rcv_buf>,t<wmem_alloc>,tb<snd_buf>,f<fwd_alloc>,w<wmem_queued>,o<opt_mem>,bl<back_log>)

              <rmem_alloc>
                     the memory allocated for receiving packet

              <rcv_buf>
                     the total memory can be allocated for receiving packet

              <wmem_alloc>
                     the memory used for sending packet (which has  been  sent
                     to layer 3)

              <snd_buf>
                     the total memory can be allocated for sending packet

              <fwd_alloc>
                     the memory allocated by the socket as cache, but not used
                     for receiving/sending  packet  yet.  If  need  memory  to
                     send/receive  packet,  the  memory  in this cache will be
                     used before allocate additional memory.

              <wmem_queued>
                     The memory allocated for sending packet  (which  has  not
                     been sent to layer 3)

              <opt_mem>
                     The  memory used for storing socket option, e.g., the key
                     for TCP MD5 signature

              <back_log>
                     The memory used for the sk backlog queue.  On  a  process
                     context,  if  the  process is receiving packet, and a new
                     packet is received, it will be put into  the  sk  backlog
                     queue, so it can be received by the process immediately

       -p, --processes
              Show process using socket.

       -i, --info
              Show internal TCP information. Below fields may appear:

              ts     show string "ts" if the timestamp option is set

              sack   show string "sack" if the sack option is set

              ecn    show string "ecn" if the explicit congestion notification
                     option is set

              ecnseen
                     show string "ecnseen" if the saw ecn  flag  is  found  in
                     received packets

              fastopen
                     show string "fastopen" if the fastopen option is set

              cong_alg
                     the  congestion  algorithm  name,  the default congestion
                     algorithm is "cubic"

              wscale:<snd_wscale>:<rcv_wscale>
                     if window scale option is used, this field shows the send
                     scale factory and receive scale factory

              rto:<icsk_rto>
                     tcp  re-transmission timeout value, the unit is millisec-
                     ond

              backoff:<icsk_backoff>
                     used for exponential backoff re-transmission, the  actual
                     re-transmission timeout value is icsk_rto << icsk_backoff

              rtt:<rtt>/<rttvar>
                     rtt  is  the  average round trip time, rttvar is the mean
                     deviation of rtt, their units are millisecond

              ato:<ato>
                     ack timeout, unit is millisecond, used for delay ack mode

              mss:<mss>
                     max segment size

              cwnd:<cwnd>
                     congestion window size

              pmtu:<pmtu>
                     path MTU value

              ssthresh:<ssthresh>
                     tcp congestion window slow start threshold

              bytes_acked:<bytes_acked>
                     bytes acked

              bytes_received:<bytes_received>
                     bytes received

              segs_out:<segs_out>
                     segments sent out

              segs_in:<segs_in>
                     segments received

              send <send_bps>bps
                     egress bps

              lastsnd:<lastsnd>
                     how long time since the last packet  sent,  the  unit  is
                     millisecond

              lastrcv:<lastrcv>
                     how long time since the last packet received, the unit is
                     millisecond

              lastack:<lastack>
                     how long time since the last ack received,  the  unit  is
                     millisecond

              pacing_rate <pacing_rate>bps/<max_pacing_rate>bps
                     the pacing rate and max pacing rate

              rcv_space:<rcv_space>
                     a  helper  variable  for  TCP internal auto tuning socket
                     receive buffer

       -K, --kill
              Attempts to forcibly close sockets. This option displays sockets
              that are successfully closed and silently skips sockets that the
              kernel does not support closing. It supports IPv4 and IPv6 sock-
              ets only.

       -s, --summary
              Print  summary  statistics.  This  option  does not parse socket
              lists obtaining summary from various sources. It is useful  when
              amount  of  sockets  is  so  huge  that parsing /proc/net/tcp is
              painful.

       -Z, --context
              As the -p option but also shows process security context.

              For netlink(7) sockets the initiating process  context  is  dis-
              played as follows:

                     1.  If valid pid show the process context.

                     2.  If  destination  is kernel (pid = 0) show kernel ini-
                         tial context.

                     3.  If a unique identifier has been allocated by the ker-
                         nel  or  netlink user, show context as "unavailable".
                         This will generally indicate that a process has  more
                         than one netlink socket active.

       -z, --contexts
              As  the  -Z option but also shows the socket context. The socket
              context is taken from the associated inode and is not the actual
              socket context held by the kernel. Sockets are typically labeled
              with the context of the creating process,  however  the  context
              shown will reflect any policy role, type and/or range transition
              rules applied, and is therefore a useful reference.

       -N NSNAME, --net=NSNAME
              Switch to the specified network namespace name.

       -b, --bpf
              Show socket BPF filters (only administrators are allowed to  get
              these information).

       -4, --ipv4
              Display only IP version 4 sockets (alias for -f inet).

       -6, --ipv6
              Display only IP version 6 sockets (alias for -f inet6).

       -0, --packet
              Display PACKET sockets (alias for -f link).

       -t, --tcp
              Display TCP sockets.

       -u, --udp
              Display UDP sockets.

       -d, --dccp
              Display DCCP sockets.

       -w, --raw
              Display RAW sockets.

       -x, --unix
              Display Unix domain sockets (alias for -f unix).

       -S, --sctp
              Display SCTP sockets.

       --vsock
              Display vsock sockets (alias for -f vsock).

       -f FAMILY, --family=FAMILY
              Display  sockets  of type FAMILY.  Currently the following fami-
              lies are supported: unix, inet, inet6, link, netlink, vsock.

       -A QUERY, --query=QUERY, --socket=QUERY
              List of socket tables to dump, separated by commas. The  follow-
              ing  identifiers are understood: all, inet, tcp, udp, raw, unix,
              packet,  netlink,   unix_dgram,   unix_stream,   unix_seqpacket,
              packet_raw, packet_dgram, dccp, sctp, vsock_stream, vsock_dgram.

       -D FILE, --diag=FILE
              Do  not  display  anything,  just dump raw information about TCP
              sockets to FILE after applying filters. If FILE is -  stdout  is
              used.

       -F FILE, --filter=FILE
              Read  filter information from FILE.  Each line of FILE is inter-
              preted like single command line option. If FILE is  -  stdin  is
              used.

       FILTER := [ state STATE-FILTER ] [ EXPRESSION ]
              Please  take  a  look  at the official documentation for details
              regarding filters.

STATE-FILTER
       STATE-FILTER allows to construct arbitrary set of states to match.  Its
       syntax is sequence of keywords state and exclude followed by identifier
       of state.

       Available identifiers are:

              All standard TCP states: established, syn-sent,  syn-recv,  fin-
              wait-1,  fin-wait-2,  time-wait,  closed,  close-wait, last-ack,
              listening and closing.

              all - for all the states

              connected - all the states except for listening and closed

              synchronized - all the connected states except for syn-sent

              bucket - states,  which  are  maintained  as  minisockets,  i.e.
              time-wait and syn-recv

              big - opposite to bucket

USAGE EXAMPLES
       ss -t -a
              Display all TCP sockets.

       ss -t -a -Z
              Display all TCP sockets with process SELinux security contexts.

       ss -u -a
              Display all UDP sockets.

       ss -o state established '( dport = :ssh or sport = :ssh )'
              Display all established ssh connections.

       ss -x src /tmp/.X11-unix/*
              Find all local processes connected to X server.

       ss  -o  state  fin-wait-1  '(  sport  =  :http or sport = :https )' dst
       193.233.7/24
              List all the tcp sockets in state FIN-WAIT-1 for our  apache  to
              network 193.233.7/24 and look at their timers.

SEE ALSO
       ip(8),
       RFC 793 - https://tools.ietf.org/rfc/rfc793.txt (TCP states)

AUTHOR
       ss was written by Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>.

       This  manual page was written by Michael Prokop <mika@grml.org> for the
       Debian project (but may be used by others).

                                                                         SS(8)
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