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 information than other tools.
  13
  14 .SH OPTIONS
  15 When no option is used ss displays a list of open non-listening
  16 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 \-O, \-\-oneline
  28 Print each socket's data on a single line.
  29 .TP
  30 .B \-n, \-\-numeric
  31 Do not try to resolve service names.
  32 .TP
  33 .B \-r, \-\-resolve
  34 Try to resolve numeric address/ports.
  35 .TP
  36 .B \-a, \-\-all
  37 Display both listening and non-listening (for TCP this means
  38 established connections) sockets.
  39 .TP
  40 .B \-l, \-\-listening
  41 Display only listening sockets (these are omitted by default).
  42 .TP
  43 .B \-o, \-\-options
  44 Show timer information. For TCP protocol, the output format is:
  45 .RS
  46 .P
  47 timer:(<timer_name>,<expire_time>,<retrans>)
  48 .P
  49 .TP
  50 .B <timer_name>
  51 the name of the timer, there are five kind of timer names:
  52 .RS
  53 .P
  54 .B on
  55 : means one of these timers: TCP retrans timer, TCP early retrans
  56 timer and tail loss probe timer
  57 .P
  58 .BR keepalive ": tcp keep alive timer"
  59 .P
  60 .BR timewait ": timewait stage timer"
  61 .P
  62 .BR persist ": zero window probe timer"
  63 .P
  64 .BR unknown ": none of the above timers"
  65 .RE
  66 .TP
  67 .B <expire_time>
  68 how long time the timer will expire
  69 .P
  70 .TP
  71 .B <retrans>
  72 how many times the retransmission occured
  73 .RE
  74 .TP
  75 .B \-e, \-\-extended
  76 Show detailed socket information. The output format is:
  77 .RS
  78 .P
  79 uid:<uid_number> ino:<inode_number> sk:<cookie>
  80 .P
  81 .TP
  82 .B <uid_number>
  83 the user id the socket belongs to
  84 .P
  85 .TP
  86 .B <inode_number>
  87 the socket's inode number in VFS
  88 .P
  89 .TP
  90 .B <cookie>
  91 an uuid of the socket
  92 .RE
  93 .TP
  94 .B \-m, \-\-memory
  95 Show socket memory usage. The output format is:
  96 .RS
  97 .P
  98 skmem:(r<rmem_alloc>,rb<rcv_buf>,t<wmem_alloc>,tb<snd_buf>,
  99 .br
 100 .RS
 101 .RS
 102 f<fwd_alloc>,w<wmem_queued>,
 103 .RE
 104 .RE
 105 .br
 106 .RS
 107 .RS
 108 o<opt_mem>,bl<back_log>)
 109 .RE
 110 .RE
 111 .P
 112 .TP
 113 .B <rmem_alloc>
 114 the memory allocated for receiving packet
 115 .P
 116 .TP
 117 .B <rcv_buf>
 118 the total memory can be allocated for receiving packet
 119 .P
 120 .TP
 121 .B <wmem_alloc>
 122 the memory used for sending packet (which has been sent to layer 3)
 123 .P
 124 .TP
 125 .B <snd_buf>
 126 the total memory can be allocated for sending packet
 127 .P
 128 .TP
 129 .B <fwd_alloc>
 130 the memory allocated by the socket as cache, but not used for
 131 receiving/sending packet yet. If need memory to send/receive packet,
 132 the memory in this cache will be used before allocate additional
 133 memory.
 134 .P
 135 .TP
 136 .B <wmem_queued>
 137 The memory allocated for sending packet (which has not been sent to layer 3)
 138 .P
 139 .TP
 140 .B <ropt_mem>
 141 The memory used for storing socket option, e.g., the key for TCP MD5 signature
 142 .P
 143 .TP
 144 .B <back_log>
 145 The memory used for the sk backlog queue. On a process context, if the
 146 process is receiving packet, and a new packet is received, it will be
 147 put into the sk backlog queue, so it can be received by the process
 148 immediately
 149 .RE
 150 .TP
 151 .B \-p, \-\-processes
 152 Show process using socket.
 153 .TP
 154 .B \-i, \-\-info
 155 Show internal TCP information. Below fields may appear:
 156 .RS
 157 .P
 158 .TP
 159 .B ts
 160 show string "ts" if the timestamp option is set
 161 .P
 162 .TP
 163 .B sack
 164 show string "sack" if the sack option is set
 165 .P
 166 .TP
 167 .B ecn
 168 show string "ecn" if the explicit congestion notification option is set
 169 .P
 170 .TP
 171 .B ecnseen
 172 show string "ecnseen" if the saw ecn flag is found in received packets
 173 .P
 174 .TP
 175 .B fastopen
 176 show string "fastopen" if the fastopen option is set
 177 .P
 178 .TP
 179 .B cong_alg
 180 the congestion algorithm name, the default congestion algorithm is "cubic"
 181 .P
 182 .TP
 183 .B wscale:<snd_wscale>:<rcv_wscale>
 184 if window scale option is used, this field shows the send scale factor
 185 and receive scale factor
 186 .P
 187 .TP
 188 .B rto:<icsk_rto>
 189 tcp re-transmission timeout value, the unit is millisecond
 190 .P
 191 .TP
 192 .B backoff:<icsk_backoff>
 193 used for exponential backoff re-transmission, the actual
 194 re-transmission timeout value is icsk_rto << icsk_backoff
 195 .P
 196 .TP
 197 .B rtt:<rtt>/<rttvar>
 198 rtt is the average round trip time, rttvar is the mean deviation of
 199 rtt, their units are millisecond
 200 .P
 201 .TP
 202 .B ato:<ato>
 203 ack timeout, unit is millisecond, used for delay ack mode
 204 .P
 205 .TP
 206 .B mss:<mss>
 207 max segment size
 208 .P
 209 .TP
 210 .B cwnd:<cwnd>
 211 congestion window size
 212 .P
 213 .TP
 214 .B pmtu:<pmtu>
 215 path MTU value
 216 .P
 217 .TP
 218 .B ssthresh:<ssthresh>
 219 tcp congestion window slow start threshold
 220 .P
 221 .TP
 222 .B bytes_acked:<bytes_acked>
 223 bytes acked
 224 .P
 225 .TP
 226 .B bytes_received:<bytes_received>
 227 bytes received
 228 .P
 229 .TP
 230 .B segs_out:<segs_out>
 231 segments sent out
 232 .P
 233 .TP
 234 .B segs_in:<segs_in>
 235 segments received
 236 .P
 237 .TP
 238 .B send <send_bps>bps
 239 egress bps
 240 .P
 241 .TP
 242 .B lastsnd:<lastsnd>
 243 how long time since the last packet sent, the unit is millisecond
 244 .P
 245 .TP
 246 .B lastrcv:<lastrcv>
 247 how long time since the last packet received, the unit is millisecond
 248 .P
 249 .TP
 250 .B lastack:<lastack>
 251 how long time since the last ack received, the unit is millisecond
 252 .P
 253 .TP
 254 .B pacing_rate <pacing_rate>bps/<max_pacing_rate>bps
 255 the pacing rate and max pacing rate
 256 .P
 257 .TP
 258 .B rcv_space:<rcv_space>
 259 a helper variable for TCP internal auto tuning socket receive buffer
 260 .RE
 261 .TP
 262 .B \-\-tos
 263 Show ToS and priority information. Below fields may appear:
 264 .RS
 265 .P
 266 .TP
 267 .B tos
 268 IPv4 Type-of-Service byte
 269 .P
 270 .TP
 271 .B tclass
 272 IPv6 Traffic Class byte
 273 .P
 274 .TP
 275 .B class_id
 276 Class id set by net_cls cgroup. If class is zero this shows priority
 277 set by SO_PRIORITY.
 278 .RE
 279 .TP
 280 .B \-K, \-\-kill
 281 Attempts to forcibly close sockets. This option displays sockets that are
 282 successfully closed and silently skips sockets that the kernel does not support
 283 closing. It supports IPv4 and IPv6 sockets only.
 284 .TP
 285 .B \-s, \-\-summary
 286 Print summary statistics. This option does not parse socket lists obtaining
 287 summary from various sources. It is useful when amount of sockets is so huge
 288 that parsing /proc/net/tcp is painful.
 289 .TP
 290 .B \-E, \-\-events
 291 Continually display sockets as they are destroyed
 292 .TP
 293 .B \-Z, \-\-context
 294 As the
 295 .B \-p
 296 option but also shows process security context.
 297 .sp
 298 For
 299 .BR netlink (7)
 300 sockets the initiating process context is displayed as follows:
 301 .RS
 302 .RS
 303 .IP "1." 4
 304 If valid pid show the process context.
 305 .IP "2." 4
 306 If destination is kernel (pid = 0) show kernel initial context.
 307 .IP "3." 4
 308 If a unique identifier has been allocated by the kernel or netlink user,
 309 show context as "unavailable". This will generally indicate that a
 310 process has more than one netlink socket active.
 311 .RE
 312 .RE
 313 .TP
 314 .B \-z, \-\-contexts
 315 As the
 316 .B \-Z
 317 option but also shows the socket context. The socket context is
 318 taken from the associated inode and is not the actual socket
 319 context held by the kernel. Sockets are typically labeled with the
 320 context of the creating process, however the context shown will reflect
 321 any policy role, type and/or range transition rules applied,
 322 and is therefore a useful reference.
 323 .TP
 324 .B \-N NSNAME, \-\-net=NSNAME
 325 Switch to the specified network namespace name.
 326 .TP
 327 .B \-b, \-\-bpf
 328 Show socket BPF filters (only administrators are allowed to get these
 329 information).
 330 .TP
 331 .B \-4, \-\-ipv4
 332 Display only IP version 4 sockets (alias for -f inet).
 333 .TP
 334 .B \-6, \-\-ipv6
 335 Display only IP version 6 sockets (alias for -f inet6).
 336 .TP
 337 .B \-0, \-\-packet
 338 Display PACKET sockets (alias for -f link).
 339 .TP
 340 .B \-t, \-\-tcp
 341 Display TCP sockets.
 342 .TP
 343 .B \-u, \-\-udp
 344 Display UDP sockets.
 345 .TP
 346 .B \-d, \-\-dccp
 347 Display DCCP sockets.
 348 .TP
 349 .B \-w, \-\-raw
 350 Display RAW sockets.
 351 .TP
 352 .B \-x, \-\-unix
 353 Display Unix domain sockets (alias for -f unix).
 354 .TP
 355 .B \-S, \-\-sctp
 356 Display SCTP sockets.
 357 .TP
 358 .B \-\-vsock
 359 Display vsock sockets (alias for -f vsock).
 360 .TP
 361 .B \-\-xdp
 362 Display XDP sockets (alias for -f xdp).
 363 .TP
 364 .B \-f FAMILY, \-\-family=FAMILY
 365 Display sockets of type FAMILY.  Currently the following families are
 366 supported: unix, inet, inet6, link, netlink, vsock, xdp.
 367 .TP
 368 .B \-A QUERY, \-\-query=QUERY, \-\-socket=QUERY
 369 List of socket tables to dump, separated by commas. The following identifiers
 370 are understood: all, inet, tcp, udp, raw, unix, packet, netlink, unix_dgram,
 371 unix_stream, unix_seqpacket, packet_raw, packet_dgram, dccp, sctp,
 372 vsock_stream, vsock_dgram, xdp Any item in the list may optionally be
 373 prefixed by an exclamation mark
 374 .RB ( ! )
 375 to exclude that socket table from being dumped.
 376 .TP
 377 .B \-D FILE, \-\-diag=FILE
 378 Do not display anything, just dump raw information about TCP sockets
 379 to FILE after applying filters. If FILE is - stdout is used.
 380 .TP
 381 .B \-F FILE, \-\-filter=FILE
 382 Read filter information from FILE.  Each line of FILE is interpreted
 383 like single command line option. If FILE is - stdin is used.
 384 .TP
 385 .B FILTER := [ state STATE-FILTER ] [ EXPRESSION ]
 386 Please take a look at the official documentation for details regarding filters.
 387
 388 .SH STATE-FILTER
 389
 390 .B STATE-FILTER
 391 allows to construct arbitrary set of states to match. Its syntax is
 392 sequence of keywords state and exclude followed by identifier of
 393 state.
 394 .TP
 395 Available identifiers are:
 396
 397 All standard TCP states:
 398 .BR established ", " syn-sent ", " syn-recv ", " fin-wait-1 ", " fin-wait-2 ", " time-wait ", " closed ", " close-wait ", " last-ack ", "
 399 .BR  listening " and " closing.
 400
 401 .B all
 402 - for all the states
 403
 404 .B connected
 405 - all the states except for
 406 .BR listening " and " closed
 407
 408 .B synchronized
 409 - all the
 410 .B connected
 411 states except for
 412 .B syn-sent
 413
 414 .B bucket
 415 - states, which are maintained as minisockets, i.e.
 416 .BR time-wait " and " syn-recv
 417
 418 .B big
 419 - opposite to
 420 .B bucket
 421
 422 .SH USAGE EXAMPLES
 423 .TP
 424 .B ss -t -a
 425 Display all TCP sockets.
 426 .TP
 427 .B ss -t -a -Z
 428 Display all TCP sockets with process SELinux security contexts.
 429 .TP
 430 .B ss -u -a
 431 Display all UDP sockets.
 432 .TP
 433 .B ss -o state established '( dport = :ssh or sport = :ssh )'
 434 Display all established ssh connections.
 435 .TP
 436 .B ss -x src /tmp/.X11-unix/*
 437 Find all local processes connected to X server.
 438 .TP
 439 .B ss -o state fin-wait-1 '( sport = :http or sport = :https )' dst 193.233.7/24
 440 List all the tcp sockets in state FIN-WAIT-1 for our apache to network
 441 193.233.7/24 and look at their timers.
 442 .TP
 443 .B ss -a -A 'all,!tcp'
 444 List sockets in all states from all socket tables but TCP.
 445 .SH SEE ALSO
 446 .BR ip (8),
 447 .br
 448 .BR RFC " 793 "
 449 - https://tools.ietf.org/rfc/rfc793.txt (TCP states)
 450
 451 .SH AUTHOR
 452 .I ss
 453 was written by Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>.
 454 .PP
 455 This manual page was written by Michael Prokop <mika@grml.org>
 456 for the Debian project (but may be used by others).