man/man8/ss.8

   1 .TH SS 8
   2 .SH NAME
   3 ss \- another utility to investigate sockets
   4 .SH SYNOPSIS
   5 .B ss
   6 .RI [ options ] " [ FILTER ]"
   7 .SH DESCRIPTION
   8 .B ss
   9 is used to dump socket statistics. It allows showing information similar
  10 to
  11 .IR netstat .
  12 It can display more TCP and state informations than other tools.
  13
  14 .SH OPTIONS
  15 When no option is used ss displays a list of
  16 open non-listening sockets (e.g. TCP/UNIX/UDP) that have established connection.
  17 .TP
  18 .B \-h, \-\-help
  19 Show summary of options.
  20 .TP
  21 .B \-V, \-\-version
  22 Output version information.
  23 .TP
  24 .B \-H, \-\-no-header
  25 Suppress header line.
  26 .TP
  27 .B \-n, \-\-numeric
  28 Do not try to resolve service names.
  29 .TP
  30 .B \-r, \-\-resolve
  31 Try to resolve numeric address/ports.
  32 .TP
  33 .B \-a, \-\-all
  34 Display both listening and non-listening (for TCP this means established connections) sockets.
  35 .TP
  36 .B \-l, \-\-listening
  37 Display only listening sockets (these are omitted by default).
  38 .TP
  39 .B \-o, \-\-options
  40 Show timer information. For tcp protocol, the output format is:
  41 .RS
  42 .P
  43 timer:(<timer_name>,<expire_time>,<retrans>)
  44 .P
  45 .TP
  46 .B <timer_name>
  47 the name of the timer, there are five kind of timer names:
  48 .RS
  49 .P
  50 .BR on ": means one of these timers: tcp retrans timer, tcp early retrans timer and tail loss probe timer"
  51 .P
  52 .BR keepalive ": tcp keep alive timer"
  53 .P
  54 .BR timewait ": timewait stage timer"
  55 .P
  56 .BR persist ": zero window probe timer"
  57 .P
  58 .BR unknown ": none of the above timers"
  59 .RE
  60 .TP
  61 .B <expire_time>
  62 how long time the timer will expire
  63 .P
  64 .TP
  65 .B <retrans>
  66 how many times the retran occurs
  67 .RE
  68 .TP
  69 .B \-e, \-\-extended
  70 Show detailed socket information. The output format is:
  71 .RS
  72 .P
  73 uid:<uid_number> ino:<inode_number> sk:<cookie>
  74 .P
  75 .TP
  76 .B <uid_number>
  77 the user id the socket belongs to
  78 .P
  79 .TP
  80 .B <inode_number>
  81 the socket's inode number in VFS
  82 .P
  83 .TP
  84 .B <cookie>
  85 an uuid of the socket
  86 .RE
  87 .TP
  88 .B \-m, \-\-memory
  89 Show socket memory usage. The output format is:
  90 .RS
  91 .P
  92 skmem:(r<rmem_alloc>,rb<rcv_buf>,t<wmem_alloc>,tb<snd_buf>,
  93 .br
  94 .RS
  95 .RS
  96 f<fwd_alloc>,w<wmem_queued>,
  97 .RE
  98 .RE
  99 .br
 100 .RS
 101 .RS
 102 o<opt_mem>,bl<back_log>)
 103 .RE
 104 .RE
 105 .P
 106 .TP
 107 .B <rmem_alloc>
 108 the memory allocated for receiving packet
 109 .P
 110 .TP
 111 .B <rcv_buf>
 112 the total memory can be allocated for receiving packet
 113 .P
 114 .TP
 115 .B <wmem_alloc>
 116 the memory used for sending packet (which has been sent to layer 3)
 117 .P
 118 .TP
 119 .B <snd_buf>
 120 the total memory can be allocated for sending packet
 121 .P
 122 .TP
 123 .B <fwd_alloc>
 124 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.
 125 .P
 126 .TP
 127 .B <wmem_queued>
 128 The memory allocated for sending packet (which has not been sent to layer 3)
 129 .P
 130 .TP
 131 .B <opt_mem>
 132 The memory used for storing socket option, e.g., the key for TCP MD5 signature
 133 .P
 134 .TP
 135 .B <back_log>
 136 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
 137 .RE
 138 .TP
 139 .B \-p, \-\-processes
 140 Show process using socket.
 141 .TP
 142 .B \-i, \-\-info
 143 Show internal TCP information. Below fields may appear:
 144 .RS
 145 .P
 146 .TP
 147 .B ts
 148 show string "ts" if the timestamp option is set
 149 .P
 150 .TP
 151 .B sack
 152 show string "sack" if the sack option is set
 153 .P
 154 .TP
 155 .B ecn
 156 show string "ecn" if the explicit congestion notification option is set
 157 .P
 158 .TP
 159 .B ecnseen
 160 show string "ecnseen" if the saw ecn flag is found in received packets
 161 .P
 162 .TP
 163 .B fastopen
 164 show string "fastopen" if the fastopen option is set
 165 .P
 166 .TP
 167 .B cong_alg
 168 the congestion algorithm name, the default congestion algorithm is "cubic"
 169 .P
 170 .TP
 171 .B wscale:<snd_wscale>:<rcv_wscale>
 172 if window scale option is used, this field shows the send scale factor and receive scale factor
 173 .P
 174 .TP
 175 .B rto:<icsk_rto>
 176 tcp re-transmission timeout value, the unit is millisecond
 177 .P
 178 .TP
 179 .B backoff:<icsk_backoff>
 180 used for exponential backoff re-transmission, the actual re-transmission timeout value is icsk_rto << icsk_backoff
 181 .P
 182 .TP
 183 .B rtt:<rtt>/<rttvar>
 184 rtt is the average round trip time, rttvar is the mean deviation of rtt, their units are millisecond
 185 .P
 186 .TP
 187 .B ato:<ato>
 188 ack timeout, unit is millisecond, used for delay ack mode
 189 .P
 190 .TP
 191 .B mss:<mss>
 192 max segment size
 193 .P
 194 .TP
 195 .B cwnd:<cwnd>
 196 congestion window size
 197 .P
 198 .TP
 199 .B pmtu:<pmtu>
 200 path MTU value
 201 .P
 202 .TP
 203 .B ssthresh:<ssthresh>
 204 tcp congestion window slow start threshold
 205 .P
 206 .TP
 207 .B bytes_acked:<bytes_acked>
 208 bytes acked
 209 .P
 210 .TP
 211 .B bytes_received:<bytes_received>
 212 bytes received
 213 .P
 214 .TP
 215 .B segs_out:<segs_out>
 216 segments sent out
 217 .P
 218 .TP
 219 .B segs_in:<segs_in>
 220 segments received
 221 .P
 222 .TP
 223 .B send <send_bps>bps
 224 egress bps
 225 .P
 226 .TP
 227 .B lastsnd:<lastsnd>
 228 how long time since the last packet sent, the unit is millisecond
 229 .P
 230 .TP
 231 .B lastrcv:<lastrcv>
 232 how long time since the last packet received, the unit is millisecond
 233 .P
 234 .TP
 235 .B lastack:<lastack>
 236 how long time since the last ack received, the unit is millisecond
 237 .P
 238 .TP
 239 .B pacing_rate <pacing_rate>bps/<max_pacing_rate>bps
 240 the pacing rate and max pacing rate
 241 .P
 242 .TP
 243 .B rcv_space:<rcv_space>
 244 a helper variable for TCP internal auto tuning socket receive buffer
 245 .RE
 246 .TP
 247 .B \-K, \-\-kill
 248 Attempts to forcibly close sockets. This option displays sockets that are
 249 successfully closed and silently skips sockets that the kernel does not support
 250 closing. It supports IPv4 and IPv6 sockets only.
 251 .TP
 252 .B \-s, \-\-summary
 253 Print summary statistics. This option does not parse socket lists obtaining
 254 summary from various sources. It is useful when amount of sockets is so huge
 255 that parsing /proc/net/tcp is painful.
 256 .TP
 257 .B \-E, \-\-events
 258 Continually display sockets as they are destroyed
 259 .TP
 260 .B \-Z, \-\-context
 261 As the
 262 .B \-p
 263 option but also shows process security context.
 264 .sp
 265 For
 266 .BR netlink (7)
 267 sockets the initiating process context is displayed as follows:
 268 .RS
 269 .RS
 270 .IP "1." 4
 271 If valid pid show the process context.
 272 .IP "2." 4
 273 If destination is kernel (pid = 0) show kernel initial context.
 274 .IP "3." 4
 275 If a unique identifier has been allocated by the kernel or netlink user,
 276 show context as "unavailable". This will generally indicate that a
 277 process has more than one netlink socket active.
 278 .RE
 279 .RE
 280 .TP
 281 .B \-z, \-\-contexts
 282 As the
 283 .B \-Z
 284 option but also shows the socket context. The socket context is
 285 taken from the associated inode and is not the actual socket
 286 context held by the kernel. Sockets are typically labeled with the
 287 context of the creating process, however the context shown will reflect
 288 any policy role, type and/or range transition rules applied,
 289 and is therefore a useful reference.
 290 .TP
 291 .B \-N NSNAME, \-\-net=NSNAME
 292 Switch to the specified network namespace name.
 293 .TP
 294 .B \-b, \-\-bpf
 295 Show socket BPF filters (only administrators are allowed to get these information).
 296 .TP
 297 .B \-4, \-\-ipv4
 298 Display only IP version 4 sockets (alias for -f inet).
 299 .TP
 300 .B \-6, \-\-ipv6
 301 Display only IP version 6 sockets (alias for -f inet6).
 302 .TP
 303 .B \-0, \-\-packet
 304 Display PACKET sockets (alias for -f link).
 305 .TP
 306 .B \-t, \-\-tcp
 307 Display TCP sockets.
 308 .TP
 309 .B \-u, \-\-udp
 310 Display UDP sockets.
 311 .TP
 312 .B \-d, \-\-dccp
 313 Display DCCP sockets.
 314 .TP
 315 .B \-w, \-\-raw
 316 Display RAW sockets.
 317 .TP
 318 .B \-x, \-\-unix
 319 Display Unix domain sockets (alias for -f unix).
 320 .TP
 321 .B \-S, \-\-sctp
 322 Display SCTP sockets.
 323 .TP
 324 .B \-\-vsock
 325 Display vsock sockets (alias for -f vsock).
 326 .TP
 327 .B \-f FAMILY, \-\-family=FAMILY
 328 Display sockets of type FAMILY.
 329 Currently the following families are supported: unix, inet, inet6, link, netlink, vsock.
 330 .TP
 331 .B \-A QUERY, \-\-query=QUERY, \-\-socket=QUERY
 332 List of socket tables to dump, separated by commas. The following identifiers
 333 are understood: all, inet, tcp, udp, raw, unix, packet, netlink, unix_dgram,
 334 unix_stream, unix_seqpacket, packet_raw, packet_dgram, dccp, sctp,
 335 vsock_stream, vsock_dgram. Any item in the list may optionally be prefixed by
 336 an exclamation mark
 337 .RB ( ! )
 338 to exclude that socket table from being dumped.
 339 .TP
 340 .B \-D FILE, \-\-diag=FILE
 341 Do not display anything, just dump raw information about TCP sockets to FILE after applying filters. If FILE is - stdout is used.
 342 .TP
 343 .B \-F FILE, \-\-filter=FILE
 344 Read filter information from FILE.
 345 Each line of FILE is interpreted like single command line option. If FILE is - stdin is used.
 346 .TP
 347 .B FILTER := [ state STATE-FILTER ] [ EXPRESSION ]
 348 Please take a look at the official documentation for details regarding filters.
 349
 350 .SH STATE-FILTER
 351
 352 .B STATE-FILTER
 353 allows to construct arbitrary set of states to match. Its syntax is sequence of keywords state and exclude followed by identifier of state.
 354 .TP
 355 Available identifiers are:
 356
 357 All standard TCP states:
 358 .BR established ", " syn-sent ", " syn-recv ", " fin-wait-1 ", " fin-wait-2 ", " time-wait ", " closed ", " close-wait ", " last-ack ", "
 359 .BR  listening " and " closing.
 360
 361 .B all
 362 - for all the states
 363
 364 .B connected
 365 - all the states except for
 366 .BR listening " and " closed
 367
 368 .B synchronized
 369 - all the
 370 .B connected
 371 states except for
 372 .B syn-sent
 373
 374 .B bucket
 375 - states, which are maintained as minisockets, i.e.
 376 .BR time-wait " and " syn-recv
 377
 378 .B big
 379 - opposite to
 380 .B bucket
 381
 382 .SH USAGE EXAMPLES
 383 .TP
 384 .B ss -t -a
 385 Display all TCP sockets.
 386 .TP
 387 .B ss -t -a -Z
 388 Display all TCP sockets with process SELinux security contexts.
 389 .TP
 390 .B ss -u -a
 391 Display all UDP sockets.
 392 .TP
 393 .B ss -o state established '( dport = :ssh or sport = :ssh )'
 394 Display all established ssh connections.
 395 .TP
 396 .B ss -x src /tmp/.X11-unix/*
 397 Find all local processes connected to X server.
 398 .TP
 399 .B ss -o state fin-wait-1 '( sport = :http or sport = :https )' dst 193.233.7/24
 400 List all the tcp sockets in state FIN-WAIT-1 for our apache to network 193.233.7/24 and look at their timers.
 401 .TP
 402 .B ss -a -A 'all,!tcp'
 403 List sockets in all states from all socket tables but TCP.
 404 .SH SEE ALSO
 405 .BR ip (8),
 406 .br
 407 .BR RFC " 793 "
 408 - https://tools.ietf.org/rfc/rfc793.txt (TCP states)
 409
 410 .SH AUTHOR
 411 .I ss
 412 was written by Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>.
 413 .PP
 414 This manual page was written by Michael Prokop <mika@grml.org>
 415 for the Debian project (but may be used by others).