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HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | STATE-FILTER | EXPRESSION | HOST SYNTAX | USAGE EXAMPLES | SEE ALSO | AUTHOR | COLOPHON |
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SS(8) System Manager's Manual SS(8)
ss - another utility to investigate sockets
ss [options] [ FILTER ]
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.
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 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 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
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.
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.
ip(8),
RFC 793 - https://tools.ietf.org/rfc/rfc793.txt (TCP states)
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).
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
2025-02-02. (At that time, the date of the most recent commit
that was found in the repository was 2025-01-21.) 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: lsfd(1), pcp-ss(1), pmdasockets(1), netstat(8), ping(8)
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HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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