1SS(8) System Manager's Manual SS(8)
2
6 ss - another utility to investigate sockets
7
9 ss [options] [ FILTER ]
10
12 ss is used to dump socket statistics. It allows showing information
13 similar to netstat. It can display more TCP and state informations
14 than other tools.
15
18 When no option is used ss displays a list of open non-listening sockets
19 (e.g. TCP/UNIX/UDP) that have established connection.
20 -h, --help
22 Show summary of options.
23 -V, --version
25 Output version information.
26 -H, --no-header
28 Suppress header line.
29 -n, --numeric
31 Do not try to resolve service names.
32 -r, --resolve
34 Try to resolve numeric address/ports.
35 -a, --all
37 Display both listening and non-listening (for TCP this means
38 established connections) sockets.
39 -l, --listening
41 Display only listening sockets (these are omitted by default).
42 -o, --options
44 Show timer information. For tcp protocol, the output format is:
45 timer:(<timer_name>,<expire_time>,<retrans>)
47 <timer_name>
49 the name of the timer, there are five kind of timer
50 names:
51 on: means one of these timers: tcp retrans timer, tcp
53 early retrans timer and tail loss probe timer
54 keepalive: tcp keep alive timer
56 timewait: timewait stage timer
58 persist: zero window probe timer
60 unknown: none of the above timers
62 <expire_time>
64 how long time the timer will expire
65 <retrans>
67 how many times the retran occurs
68 -e, --extended
70 Show detailed socket information. The output format is:
71 uid:<uid_number> ino:<inode_number> sk:<cookie>
73 <uid_number>
75 the user id the socket belongs to
76 <inode_number>
78 the socket's inode number in VFS
79 <cookie>
81 an uuid of the socket
82 -m, --memory
84 Show socket memory usage. The output format is:
85 skmem:(r<rmem_alloc>,rb<rcv_buf>,t<wmem_alloc>,tb<snd_buf>,
87 f<fwd_alloc>,w<wmem_queued>,
88 o<opt_mem>,bl<back_log>)
89 <rmem_alloc>
91 the memory allocated for receiving packet
92 <rcv_buf>
94 the total memory can be allocated for receiving packet
95 <wmem_alloc>
97 the memory used for sending packet (which has been sent
98 to layer 3)
99 <snd_buf>
101 the total memory can be allocated for sending packet
102 <fwd_alloc>
104 the memory allocated by the socket as cache, but not used
105 for receiving/sending packet yet. If need memory to
106 send/receive packet, the memory in this cache will be
107 used before allocate additional memory.
108 <wmem_queued>
110 The memory allocated for sending packet (which has not
111 been sent to layer 3)
112 <opt_mem>
114 The memory used for storing socket option, e.g., the key
115 for TCP MD5 signature
116 <back_log>
118 The memory used for the sk backlog queue. On a process
119 context, if the process is receiving packet, and a new
120 packet is received, it will be put into the sk backlog
121 queue, so it can be received by the process immediately
122 -p, --processes
124 Show process using socket.
125 -i, --info
127 Show internal TCP information. Below fields may appear:
128 ts show string "ts" if the timestamp option is set
130 sack show string "sack" if the sack option is set
132 ecn show string "ecn" if the explicit congestion notification
134 option is set
135 ecnseen
137 show string "ecnseen" if the saw ecn flag is found in
138 received packets
139 fastopen
141 show string "fastopen" if the fastopen option is set
142 cong_alg
144 the congestion algorithm name, the default congestion
145 algorithm is "cubic"
146 wscale:<snd_wscale>:<rcv_wscale>
148 if window scale option is used, this field shows the send
149 scale factor and receive scale factor
150 rto:<icsk_rto>
152 tcp re-transmission timeout value, the unit is millisec‐
153 ond
154 backoff:<icsk_backoff>
156 used for exponential backoff re-transmission, the actual
157 re-transmission timeout value is icsk_rto << icsk_backoff
158 rtt:<rtt>/<rttvar>
160 rtt is the average round trip time, rttvar is the mean
161 deviation of rtt, their units are millisecond
162 ato:<ato>
164 ack timeout, unit is millisecond, used for delay ack mode
165 mss:<mss>
167 max segment size
168 cwnd:<cwnd>
170 congestion window size
171 pmtu:<pmtu>
173 path MTU value
174 ssthresh:<ssthresh>
176 tcp congestion window slow start threshold
177 bytes_acked:<bytes_acked>
179 bytes acked
180 bytes_received:<bytes_received>
182 bytes received
183 segs_out:<segs_out>
185 segments sent out
186 segs_in:<segs_in>
188 segments received
189 send <send_bps>bps
191 egress bps
192 lastsnd:<lastsnd>
194 how long time since the last packet sent, the unit is
195 millisecond
196 lastrcv:<lastrcv>
198 how long time since the last packet received, the unit is
199 millisecond
200 lastack:<lastack>
202 how long time since the last ack received, the unit is
203 millisecond
204 pacing_rate <pacing_rate>bps/<max_pacing_rate>bps
206 the pacing rate and max pacing rate
207 rcv_space:<rcv_space>
209 a helper variable for TCP internal auto tuning socket
210 receive buffer
211 -K, --kill
213 Attempts to forcibly close sockets. This option displays sockets
214 that are successfully closed and silently skips sockets that the
215 kernel does not support closing. It supports IPv4 and IPv6 sock‐
216 ets only.
217 -s, --summary
219 Print summary statistics. This option does not parse socket
220 lists obtaining summary from various sources. It is useful when
221 amount of sockets is so huge that parsing /proc/net/tcp is
222 painful.
223 -E, --events
225 Continually display sockets as they are destroyed
226 -Z, --context
228 As the -p option but also shows process security context.
229 For netlink(7) sockets the initiating process context is dis‐
231 played as follows:
232 1. If valid pid show the process context.
234 2. If destination is kernel (pid = 0) show kernel ini‐
236 tial context.
237 3. If a unique identifier has been allocated by the ker‐
239 nel or netlink user, show context as "unavailable".
240 This will generally indicate that a process has more
241 than one netlink socket active.
242 -z, --contexts
244 As the -Z option but also shows the socket context. The socket
245 context is taken from the associated inode and is not the actual
246 socket context held by the kernel. Sockets are typically labeled
247 with the context of the creating process, however the context
248 shown will reflect any policy role, type and/or range transition
249 rules applied, and is therefore a useful reference.
250 -N NSNAME, --net=NSNAME
252 Switch to the specified network namespace name.
253 -b, --bpf
255 Show socket BPF filters (only administrators are allowed to get
256 these information).
257 -4, --ipv4
259 Display only IP version 4 sockets (alias for -f inet).
260 -6, --ipv6
262 Display only IP version 6 sockets (alias for -f inet6).
263 -0, --packet
265 Display PACKET sockets (alias for -f link).
266 -t, --tcp
268 Display TCP sockets.
269 -u, --udp
271 Display UDP sockets.
272 -d, --dccp
274 Display DCCP sockets.
275 -w, --raw
277 Display RAW sockets.
278 -x, --unix
280 Display Unix domain sockets (alias for -f unix).
281 -S, --sctp
283 Display SCTP sockets.
284 --vsock
286 Display vsock sockets (alias for -f vsock).
287 -f FAMILY, --family=FAMILY
289 Display sockets of type FAMILY. Currently the following fami‐
290 lies are supported: unix, inet, inet6, link, netlink, vsock.
291 -A QUERY, --query=QUERY, --socket=QUERY
293 List of socket tables to dump, separated by commas. The follow‐
294 ing identifiers are understood: all, inet, tcp, udp, raw, unix,
295 packet, netlink, unix_dgram, unix_stream, unix_seqpacket,
296 packet_raw, packet_dgram, dccp, sctp, vsock_stream, vsock_dgram.
297 Any item in the list may optionally be prefixed by an exclama‐
298 tion mark (!) to exclude that socket table from being dumped.
299 -D FILE, --diag=FILE
301 Do not display anything, just dump raw information about TCP
302 sockets to FILE after applying filters. If FILE is - stdout is
303 used.
304 -F FILE, --filter=FILE
306 Read filter information from FILE. Each line of FILE is inter‐
307 preted like single command line option. If FILE is - stdin is
308 used.
309 FILTER := [ state STATE-FILTER ] [ EXPRESSION ]
311 Please take a look at the official documentation for details
312 regarding filters.
313
316 STATE-FILTER allows to construct arbitrary set of states to match. Its
317 syntax is sequence of keywords state and exclude followed by identifier
318 of state.
319 Available identifiers are:
321 All standard TCP states: established, syn-sent, syn-recv, fin-
323 wait-1, fin-wait-2, time-wait, closed, close-wait, last-ack,
324 listening and closing.
325 all - for all the states
327 connected - all the states except for listening and closed
329 synchronized - all the connected states except for syn-sent
331 bucket - states, which are maintained as minisockets, i.e.
333 time-wait and syn-recv
334 big - opposite to bucket
336
339 ss -t -a
340 Display all TCP sockets.
341 ss -t -a -Z
343 Display all TCP sockets with process SELinux security contexts.
344 ss -u -a
346 Display all UDP sockets.
347 ss -o state established '( dport = :ssh or sport = :ssh )'
349 Display all established ssh connections.
350 ss -x src /tmp/.X11-unix/*
352 Find all local processes connected to X server.
353 ss -o state fin-wait-1 '( sport = :http or sport = :https )' dst
355 193.233.7/24
356 List all the tcp sockets in state FIN-WAIT-1 for our apache to
357 network 193.233.7/24 and look at their timers.
358 ss -a -A 'all,!tcp'
360 List sockets in all states from all socket tables but TCP.
361
363 ip(8),
364 RFC 793 - https://tools.ietf.org/rfc/rfc793.txt (TCP states)
365
368 ss was written by Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>.
369 This manual page was written by Michael Prokop <mika@grml.org> for the
371 Debian project (but may be used by others).
372 SS(8)