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>,f<fwd_alloc>,
  93 .br
  94 .RS
  95 .RS
  96 w<wmem_queued>,o<opt_mem>,bl<back_log>)
  97 .RE
  98 .RE
  99 .P
 100 .TP
 101 .B <rmem_alloc>
 102 the memory allocated for receiving packet
 103 .P
 104 .TP
 105 .B <rcv_buf>
 106 the total memory can be allocated for receiving packet
 107 .P
 108 .TP
 109 .B <wmem_alloc>
 110 the memory used for sending packet (which has been sent to layer 3)
 111 .P
 112 .TP
 113 .B <snd_buf>
 114 the total memory can be allocated for sending packet
 115 .P
 116 .TP
 117 .B <fwd_alloc>
 118 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.
 119 .P
 120 .TP
 121 .B <wmem_queued>
 122 The memory allocated for sending packet (which has not been sent to layer 3)
 123 .P
 124 .TP
 125 .B <opt_mem>
 126 The memory used for storing socket option, e.g., the key for TCP MD5 signature
 127 .P
 128 .TP
 129 .B <back_log>
 130 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
 131 .RE
 132 .TP
 133 .B \-p, \-\-processes
 134 Show process using socket.
 135 .TP
 136 .B \-i, \-\-info
 137 Show internal TCP information. Below fields may appear:
 138 .RS
 139 .P
 140 .TP
 141 .B ts
 142 show string "ts" if the timestamp option is set
 143 .P
 144 .TP
 145 .B sack
 146 show string "sack" if the sack option is set
 147 .P
 148 .TP
 149 .B ecn
 150 show string "ecn" if the explicit congestion notification option is set
 151 .P
 152 .TP
 153 .B ecnseen
 154 show string "ecnseen" if the saw ecn flag is found in received packets
 155 .P
 156 .TP
 157 .B fastopen
 158 show string "fastopen" if the fastopen option is set
 159 .P
 160 .TP
 161 .B cong_alg
 162 the congestion algorithm name, the default congestion algorithm is "cubic"
 163 .P
 164 .TP
 165 .B wscale:<snd_wscale>:<rcv_wscale>
 166 if window scale option is used, this field shows the send scale factory and receive scale factory
 167 .P
 168 .TP
 169 .B rto:<icsk_rto>
 170 tcp re-transmission timeout value, the unit is millisecond
 171 .P
 172 .TP
 173 .B backoff:<icsk_backoff>
 174 used for exponential backoff re-transmission, the actual re-transmission timeout value is icsk_rto << icsk_backoff
 175 .P
 176 .TP
 177 .B rtt:<rtt>/<rttvar>
 178 rtt is the average round trip time, rttvar is the mean deviation of rtt, their units are millisecond
 179 .P
 180 .TP
 181 .B ato:<ato>
 182 ack timeout, unit is millisecond, used for delay ack mode
 183 .P
 184 .TP
 185 .B mss:<mss>
 186 max segment size
 187 .P
 188 .TP
 189 .B cwnd:<cwnd>
 190 congestion window size
 191 .P
 192 .TP
 193 .B pmtu:<pmtu>
 194 path MTU value
 195 .P
 196 .TP
 197 .B ssthresh:<ssthresh>
 198 tcp congestion window slow start threshold
 199 .P
 200 .TP
 201 .B bytes_acked:<bytes_acked>
 202 bytes acked
 203 .P
 204 .TP
 205 .B bytes_received:<bytes_received>
 206 bytes received
 207 .P
 208 .TP
 209 .B segs_out:<segs_out>
 210 segments sent out
 211 .P
 212 .TP
 213 .B segs_in:<segs_in>
 214 segments received
 215 .P
 216 .TP
 217 .B send <send_bps>bps
 218 egress bps
 219 .P
 220 .TP
 221 .B lastsnd:<lastsnd>
 222 how long time since the last packet sent, the unit is millisecond
 223 .P
 224 .TP
 225 .B lastrcv:<lastrcv>
 226 how long time since the last packet received, the unit is millisecond
 227 .P
 228 .TP
 229 .B lastack:<lastack>
 230 how long time since the last ack received, the unit is millisecond
 231 .P
 232 .TP
 233 .B pacing_rate <pacing_rate>bps/<max_pacing_rate>bps
 234 the pacing rate and max pacing rate
 235 .P
 236 .TP
 237 .B rcv_space:<rcv_space>
 238 a helper variable for TCP internal auto tuning socket receive buffer
 239 .RE
 240 .TP
 241 .B \-K, \-\-kill
 242 Attempts to forcibly close sockets. This option displays sockets that are
 243 successfully closed and silently skips sockets that the kernel does not support
 244 closing. It supports IPv4 and IPv6 sockets only.
 245 .TP
 246 .B \-s, \-\-summary
 247 Print summary statistics. This option does not parse socket lists obtaining
 248 summary from various sources. It is useful when amount of sockets is so huge
 249 that parsing /proc/net/tcp is painful.
 250 .TP
 251 .B \-E, \-\-events
 252 Continually display sockets as they are destroyed
 253 .TP
 254 .B \-Z, \-\-context
 255 As the
 256 .B \-p
 257 option but also shows process security context.
 258 .sp
 259 For
 260 .BR netlink (7)
 261 sockets the initiating process context is displayed as follows:
 262 .RS
 263 .RS
 264 .IP "1." 4
 265 If valid pid show the process context.
 266 .IP "2." 4
 267 If destination is kernel (pid = 0) show kernel initial context.
 268 .IP "3." 4
 269 If a unique identifier has been allocated by the kernel or netlink user,
 270 show context as "unavailable". This will generally indicate that a
 271 process has more than one netlink socket active.
 272 .RE
 273 .RE
 274 .TP
 275 .B \-z, \-\-contexts
 276 As the
 277 .B \-Z
 278 option but also shows the socket context. The socket context is
 279 taken from the associated inode and is not the actual socket
 280 context held by the kernel. Sockets are typically labeled with the
 281 context of the creating process, however the context shown will reflect
 282 any policy role, type and/or range transition rules applied,
 283 and is therefore a useful reference.
 284 .TP
 285 .B \-N NSNAME, \-\-net=NSNAME
 286 Switch to the specified network namespace name.
 287 .TP
 288 .B \-b, \-\-bpf
 289 Show socket BPF filters (only administrators are allowed to get these information).
 290 .TP
 291 .B \-4, \-\-ipv4
 292 Display only IP version 4 sockets (alias for -f inet).
 293 .TP
 294 .B \-6, \-\-ipv6
 295 Display only IP version 6 sockets (alias for -f inet6).
 296 .TP
 297 .B \-0, \-\-packet
 298 Display PACKET sockets (alias for -f link).
 299 .TP
 300 .B \-t, \-\-tcp
 301 Display TCP sockets.
 302 .TP
 303 .B \-u, \-\-udp
 304 Display UDP sockets.
 305 .TP
 306 .B \-d, \-\-dccp
 307 Display DCCP sockets.
 308 .TP
 309 .B \-w, \-\-raw
 310 Display RAW sockets.
 311 .TP
 312 .B \-x, \-\-unix
 313 Display Unix domain sockets (alias for -f unix).
 314 .TP
 315 .B \-S, \-\-sctp
 316 Display SCTP sockets.
 317 .TP
 318 .B \-\-vsock
 319 Display vsock sockets (alias for -f vsock).
 320 .TP
 321 .B \-f FAMILY, \-\-family=FAMILY
 322 Display sockets of type FAMILY.
 323 Currently the following families are supported: unix, inet, inet6, link, netlink, vsock.
 324 .TP
 325 .B \-A QUERY, \-\-query=QUERY, \-\-socket=QUERY
 326 List of socket tables to dump, separated by commas. The following identifiers
 327 are understood: all, inet, tcp, udp, raw, unix, packet, netlink, unix_dgram,
 328 unix_stream, unix_seqpacket, packet_raw, packet_dgram, dccp, sctp,
 329 vsock_stream, vsock_dgram. Any item in the list may optionally be prefixed by
 330 an exclamation mark
 331 .RB ( ! )
 332 to exclude that socket table from being dumped.
 333 .TP
 334 .B \-D FILE, \-\-diag=FILE
 335 Do not display anything, just dump raw information about TCP sockets to FILE after applying filters. If FILE is - stdout is used.
 336 .TP
 337 .B \-F FILE, \-\-filter=FILE
 338 Read filter information from FILE.
 339 Each line of FILE is interpreted like single command line option. If FILE is - stdin is used.
 340 .TP
 341 .B FILTER := [ state STATE-FILTER ] [ EXPRESSION ]
 342 Please take a look at the official documentation for details regarding filters.
 343
 344 .SH STATE-FILTER
 345
 346 .B STATE-FILTER
 347 allows to construct arbitrary set of states to match. Its syntax is sequence of keywords state and exclude followed by identifier of state.
 348 .TP
 349 Available identifiers are:
 350
 351 All standard TCP states:
 352 .BR established ", " syn-sent ", " syn-recv ", " fin-wait-1 ", " fin-wait-2 ", " time-wait ", " closed ", " close-wait ", " last-ack ", "
 353 .BR  listening " and " closing.
 354
 355 .B all
 356 - for all the states
 357
 358 .B connected
 359 - all the states except for
 360 .BR listening " and " closed
 361
 362 .B synchronized
 363 - all the
 364 .B connected
 365 states except for
 366 .B syn-sent
 367
 368 .B bucket
 369 - states, which are maintained as minisockets, i.e.
 370 .BR time-wait " and " syn-recv
 371
 372 .B big
 373 - opposite to
 374 .B bucket
 375
 376 .SH USAGE EXAMPLES
 377 .TP
 378 .B ss -t -a
 379 Display all TCP sockets.
 380 .TP
 381 .B ss -t -a -Z
 382 Display all TCP sockets with process SELinux security contexts.
 383 .TP
 384 .B ss -u -a
 385 Display all UDP sockets.
 386 .TP
 387 .B ss -o state established '( dport = :ssh or sport = :ssh )'
 388 Display all established ssh connections.
 389 .TP
 390 .B ss -x src /tmp/.X11-unix/*
 391 Find all local processes connected to X server.
 392 .TP
 393 .B ss -o state fin-wait-1 '( sport = :http or sport = :https )' dst 193.233.7/24
 394 List all the tcp sockets in state FIN-WAIT-1 for our apache to network 193.233.7/24 and look at their timers.
 395 .TP
 396 .B ss -a -A 'all,!tcp'
 397 List sockets in all states from all socket tables but TCP.
 398 .SH SEE ALSO
 399 .BR ip (8),
 400 .br
 401 .BR RFC " 793 "
 402 - https://tools.ietf.org/rfc/rfc793.txt (TCP states)
 403
 404 .SH AUTHOR
 405 .I ss
 406 was written by Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>.
 407 .PP
 408 This manual page was written by Michael Prokop <mika@grml.org>
 409 for the Debian project (but may be used by others).