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 information 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.

       -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 classic 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
       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
       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
       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
       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
       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)