ss(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | STATE-FILTER | EXPRESSION | HOST SYNTAX | USAGE EXAMPLES | SEE ALSO | AUTHOR | COLOPHON

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

NAME         top

       ss - another utility to investigate sockets

SYNOPSIS         top

       ss [options] [ FILTER ]

DESCRIPTION         top

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

OPTIONS         top

       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.

       -O, --oneline
              Print each socket's data on a single line.

       -n, --numeric
              Do not try to resolve service names. Show exact bandwidth
              values, instead of human-readable.

       -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 retransmission occurred

       -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>,d<sock_drop>)

              <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)

              <ropt_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

              <sock_drop>
                     the number of packets dropped before they are de-
                     multiplexed into the socket

       -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 factor and receive scale factor

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

              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

              tcp-ulp-mptcp flags:[MmBbJjecv]
              token:<rem_token(rem_id)/loc_token(loc_id)> seq:<sn>
              sfseq:<ssn> ssnoff:<off> maplen:<maplen>
                     MPTCP subflow information

       --tos  Show ToS and priority information. Below fields may
              appear:

              tos    IPv4 Type-of-Service byte

              tclass IPv6 Traffic Class byte

              class_id
                     Class id set by net_cls cgroup. If class is zero
                     this shows priority set by SO_PRIORITY.

       --cgroup
              Show cgroup information. Below fields may appear:

              cgroup Cgroup v2 pathname. This pathname is relative to
                     the mount point of the hierarchy.

       -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 sockets 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.

       -E, --events
              Continually display sockets as they are destroyed

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

              For netlink(7) sockets the initiating process context is
              displayed as follows:

                     1.  If valid pid show the process context.

                     2.  If destination is kernel (pid = 0) show kernel
                         initial context.

                     3.  If a unique identifier has been allocated by
                         the kernel 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).

       --xdp  Display XDP sockets (alias for -f xdp).

       --inet-sockopt
              Display inet socket options.

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

       -A QUERY, --query=QUERY, --socket=QUERY
              List of socket tables to dump, separated by commas. The
              following 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, xdp Any item in the list may
              optionally be prefixed by an exclamation mark (!)  to
              exclude that socket table from being dumped.

       -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
              interpreted 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         top

       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

EXPRESSION         top

       EXPRESSION allows filtering based on specific criteria.
       EXPRESSION consists of a series of predicates combined by boolean
       operators. The possible operators in increasing order of
       precedence are or (or | or ||), and (or & or &&), and not (or !).
       If no operator is between consecutive predicates, an implicit and
       operator is assumed. Subexpressions can be grouped with "(" and
       ")".

       The following predicates are supported:

       {dst|src} [=] HOST
              Test if the destination or source matches HOST. See HOST
              SYNTAX for details.

       {dport|sport} [OP] [FAMILY:]:PORT
              Compare the destination or source port to PORT. OP can be
              any of "<", "<=", "=", "!=", ">=" and ">". Following
              normal arithmetic rules. FAMILY and PORT are as described
              in HOST SYNTAX below.

       dev [=|!=] DEVICE
              Match based on the device the connection uses. DEVICE can
              either be a device name or the index of the interface.

       fwmark [=|!=] MASK
              Matches based on the fwmark value for the connection. This
              can either be a specific mark value or a mark value
              followed by a "/" and a bitmask of which bits to use in
              the comparison. For example "fwmark = 0x01/0x03" would
              match if the two least significant bits of the fwmark were
              0x01.

       cgroup [=|!=] PATH
              Match if the connection is part of a cgroup at the given
              path.

       autobound
              Match if the port or path of the source address was
              automatically allocated (rather than explicitly
              specified).

       Most operators have aliases. If no operator is supplied "=" is
       assumed.  Each of the following groups of operators are all
       equivalent:

              • = == eq

              • != ne neq

              • > gt

              • < lt

              • >= ge geq

              • <= le leq

              • ! not

              • | || or

              • & && and

HOST SYNTAX         top

       The general host syntax is [FAMILY:]ADDRESS[:PORT].

       FAMILY must be one of the families supported by the -f option. If
       not given it defaults to the family given with the -f option, and
       if that is also missing, will assume either inet or inet6. Note
       that all host conditions in the expression should either all be
       the same family or be only inet and inet6. If there is some other
       mixture of families, the results will probably be unexpected.

       The form of ADDRESS and PORT depends on the family used. "*" can
       be used as a wildcard for either the address or port. The details
       for each family are as follows:

       unix   ADDRESS is a glob pattern (see fnmatch(3)) that will be
              matched case-insensitively against the unix socket's
              address. Both path and abstract names are supported. Unix
              addresses do not support a port, and "*" cannot be used as
              a wildcard.

       link   ADDRESS is the case-insensitive name of an Ethernet
              protocol to match. PORT is either a device name or a
              device index for the desired link device, as seen in the
              output of ip link.

       netlink
              ADDRESS is a descriptor of the netlink family. Possible
              values come from /etc/iproute2/nl_protos. PORT is the port
              id of the socket, which is usually the same as the owning
              process id. The value "kernel" can be used to represent
              the kernel (port id of 0).

       vsock  ADDRESS is an integer representing the CID address, and
              PORT is the port.

       inet and inet6
              ADDRESS is an ip address (either v4 or v6 depending on the
              family) or a DNS hostname that resolves to an ip address
              of the required version. An ipv6 address must be enclosed
              in "[" and "]" to disambiguate the port separator. The
              address may additionally have a prefix length given in
              CIDR notation (a slash followed by the prefix length in
              bits). PORT is either the numerical socket port, or the
              service name for the port to match.

USAGE EXAMPLES         top

       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.

       ss -a -A 'all,!tcp'
              List sockets in all states from all socket tables but TCP.

SEE ALSO         top

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

AUTHOR         top

       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).

COLOPHON         top

       This page is part of the iproute2 (utilities for controlling
       TCP/IP networking and traffic) project.  Information about the
       project can be found at 
       ⟨http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2⟩.
       If you have a bug report for this manual page, send it to
       netdev@vger.kernel.org, shemminger@osdl.org.  This page was
       obtained from the project's upstream Git repository
       ⟨https://git.kernel.org/pub/scm/network/iproute2/iproute2.git⟩ on
       2021-04-01.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-03-22.)  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

                                                                   SS(8)

Pages that refer to this page: pmdasockets(1)netstat(8)ping(8)