Ubuntu Manpage: ss - another utility to investigate sockets

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.

-Q, --no-queues
Suppress sending and receiving queue columns.

-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).

-B, --bound-inactive
Display only TCP bound but inactive (not listening, connecting, etc.) 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)

<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

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

-p, --processes
Show process using socket.

-T, --threads
Show thread using socket. Implies -p.

-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.

--tipcinfo
Show internal tipc socket information.

-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. If the -T option is used,
also shows thread 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.

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

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

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

-M, --mptcp
Display MPTCP sockets.

--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, tipc, 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, tipc,
vsock_stream, vsock_dgram, xdp, mptcp. 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.

--bpf-maps
Pretty-print all the BPF socket-local data entries for each socket.

--bpf-map-id=MAP_ID
Pretty-print the BPF socket-local data entries for the requested map ID. Can be
used more than once.

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

STATE-FILTER

       STATE-FILTER  allows  one  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

              bound-inactive  -  bound but otherwise inactive sockets (not listening, connecting,
              etc.)

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.

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)