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