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.TH SS 8
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.SH NAME
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ss \- another utility to investigate sockets
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.SH SYNOPSIS
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.B ss
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.RI [ options ] " [ FILTER ]"
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.SH DESCRIPTION
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.B ss
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is used to dump socket statistics. It allows showing information similar
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to
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.IR netstat .
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It can display more TCP and state informations than other tools.
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.SH OPTIONS
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When no option is used ss displays a list of
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open non-listening sockets (e.g. TCP/UNIX/UDP) that have established connection.
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.TP
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.B \-h, \-\-help
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Show summary of options.
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.TP
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.B \-V, \-\-version
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Output version information.
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.TP
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.B \-H, \-\-no-header
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Suppress header line.
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.TP
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.B \-n, \-\-numeric
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Do not try to resolve service names.
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.TP
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.B \-r, \-\-resolve
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Try to resolve numeric address/ports.
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.TP
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.B \-a, \-\-all
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Display both listening and non-listening (for TCP this means established connections) sockets.
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.TP
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.B \-l, \-\-listening
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Display only listening sockets (these are omitted by default).
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.TP
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.B \-o, \-\-options
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Show timer information. For tcp protocol, the output format is:
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.RS
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.P
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timer:(<timer_name>,<expire_time>,<retrans>)
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.P
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.TP
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.B <timer_name>
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the name of the timer, there are five kind of timer names:
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.RS
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.P
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.BR on ": means one of these timers: tcp retrans timer, tcp early retrans timer and tail loss probe timer"
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.P
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.BR keepalive ": tcp keep alive timer"
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.P
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.BR timewait ": timewait stage timer"
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.P
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.BR persist ": zero window probe timer"
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.P
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.BR unknown ": none of the above timers"
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.RE
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.TP
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.B <expire_time>
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how long time the timer will expire
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.P
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.TP
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.B <retrans>
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how many times the retran occurs
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.RE
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.TP
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.B \-e, \-\-extended
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Show detailed socket information. The output format is:
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.RS
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.P
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uid:<uid_number> ino:<inode_number> sk:<cookie>
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.P
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.TP
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.B <uid_number>
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the user id the socket belongs to
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.P
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.TP
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.B <inode_number>
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the socket's inode number in VFS
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.P
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.TP
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.B <cookie>
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an uuid of the socket
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.RE
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.TP
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.B \-m, \-\-memory
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Show socket memory usage. The output format is:
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.RS
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.P
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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>)
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.P
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.TP
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.B <rmem_alloc>
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the memory allocated for receiving packet
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.P
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.TP
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.B <rcv_buf>
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the total memory can be allocated for receiving packet
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.P
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.TP
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.B <wmem_alloc>
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the memory used for sending packet (which has been sent to layer 3)
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.P
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.TP
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.B <snd_buf>
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the total memory can be allocated for sending packet
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.P
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.TP
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.B <fwd_alloc>
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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.
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.P
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.TP
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.B <wmem_queued>
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The memory allocated for sending packet (which has not been sent to layer 3)
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.P
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.TP
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.B <opt_mem>
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The memory used for storing socket option, e.g., the key for TCP MD5 signature
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.P
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.TP
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.B <back_log>
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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
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.RE
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.TP
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.B \-p, \-\-processes
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Show process using socket.
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.TP
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.B \-i, \-\-info
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Show internal TCP information. Below fields may appear:
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.RS
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.P
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.TP
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.B ts
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show string "ts" if the timestamp option is set
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.P
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.TP
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.B sack
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show string "sack" if the sack option is set
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.P
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.TP
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.B ecn
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show string "ecn" if the explicit congestion notification option is set
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.P
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.TP
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.B ecnseen
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show string "ecnseen" if the saw ecn flag is found in received packets
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.P
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.TP
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.B fastopen
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show string "fastopen" if the fastopen option is set
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.P
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.TP
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.B cong_alg
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the congestion algorithm name, the default congestion algorithm is "cubic"
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.P
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.TP
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.B wscale:<snd_wscale>:<rcv_wscale>
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if window scale option is used, this field shows the send scale factory and receive scale factory
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.P
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.TP
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.B rto:<icsk_rto>
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tcp re-transmission timeout value, the unit is millisecond
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.P
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.TP
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.B backoff:<icsk_backoff>
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used for exponential backoff re-transmission, the actual re-transmission timeout value is icsk_rto << icsk_backoff
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.P
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.TP
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.B rtt:<rtt>/<rttvar>
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rtt is the average round trip time, rttvar is the mean deviation of rtt, their units are millisecond
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.P
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.TP
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.B ato:<ato>
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ack timeout, unit is millisecond, used for delay ack mode
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.P
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.TP
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.B mss:<mss>
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max segment size
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.P
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.TP
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.B cwnd:<cwnd>
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congestion window size
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.P
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.TP
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.B ssthresh:<ssthresh>
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tcp congestion window slow start threshold
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.P
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.TP
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.B bytes_acked:<bytes_acked>
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bytes acked
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.P
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.TP
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.B bytes_received:<bytes_received>
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bytes received
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.P
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.TP
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.B segs_out:<segs_out>
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segments sent out
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.P
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.TP
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.B segs_in:<segs_in>
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segments received
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.P
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.TP
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.B send <send_bps>bps
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egress bps
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.P
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.TP
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.B lastsnd:<lastsnd>
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how long time since the last packet sent, the unit is millisecond
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.P
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.TP
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.B lastrcv:<lastrcv>
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how long time since the last packet received, the unit is millisecond
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.P
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.TP
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.B lastack:<lastack>
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how long time since the last ack received, the unit is millisecond
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.P
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.TP
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.B pacing_rate <pacing_rate>bps/<max_pacing_rate>bps
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the pacing rate and max pacing rate
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.P
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.TP
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.B rcv_space:<rcv_space>
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a helper variable for TCP internal auto tuning socket receive buffer
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.RE
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.TP
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.B \-K, \-\-kill
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Attempts to forcibly close sockets. This option displays sockets that are
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successfully closed and silently skips sockets that the kernel does not support
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closing. It supports IPv4 and IPv6 sockets only.
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.TP
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.B \-s, \-\-summary
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Print summary statistics. This option does not parse socket lists obtaining
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summary from various sources. It is useful when amount of sockets is so huge
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that parsing /proc/net/tcp is painful.
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.TP
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.B \-Z, \-\-context
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As the
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.B \-p
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option but also shows process security context.
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.sp
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For
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.BR netlink (7)
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sockets the initiating process context is displayed as follows:
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.RS
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.RS
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.IP "1." 4
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If valid pid show the process context.
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.IP "2." 4
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If destination is kernel (pid = 0) show kernel initial context.
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.IP "3." 4
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If a unique identifier has been allocated by the kernel or netlink user,
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show context as "unavailable". This will generally indicate that a
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process has more than one netlink socket active.
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.RE
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.RE
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.TP
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.B \-z, \-\-contexts
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As the
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.B \-Z
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option but also shows the socket context. The socket context is
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taken from the associated inode and is not the actual socket
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context held by the kernel. Sockets are typically labeled with the
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context of the creating process, however the context shown will reflect
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any policy role, type and/or range transition rules applied,
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and is therefore a useful reference.
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.TP
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.B \-N NSNAME, \-\-net=NSNAME
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Switch to the specified network namespace name.
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.TP
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.B \-b, \-\-bpf
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Show socket BPF filters (only administrators are allowed to get these information).
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.TP
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.B \-4, \-\-ipv4
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Display only IP version 4 sockets (alias for -f inet).
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.TP
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.B \-6, \-\-ipv6
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Display only IP version 6 sockets (alias for -f inet6).
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.TP
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.B \-0, \-\-packet
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Display PACKET sockets (alias for -f link).
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.TP
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.B \-t, \-\-tcp
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Display TCP sockets.
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.TP
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.B \-u, \-\-udp
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Display UDP sockets.
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.TP
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.B \-d, \-\-dccp
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Display DCCP sockets.
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.TP
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.B \-w, \-\-raw
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Display RAW sockets.
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.TP
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.B \-x, \-\-unix
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Display Unix domain sockets (alias for -f unix).
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.TP
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.B \-S, \-\-sctp
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Display SCTP sockets.
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.TP
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.B \-f FAMILY, \-\-family=FAMILY
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Display sockets of type FAMILY.
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Currently the following families are supported: unix, inet, inet6, link, netlink.
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.TP
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.B \-A QUERY, \-\-query=QUERY, \-\-socket=QUERY
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List of socket tables to dump, separated by commas. The following identifiers
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are understood: all, inet, tcp, udp, raw, unix, packet, netlink, unix_dgram,
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unix_stream, unix_seqpacket, packet_raw, packet_dgram, dccp, sctp.
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.TP
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.B \-D FILE, \-\-diag=FILE
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Do not display anything, just dump raw information about TCP sockets to FILE after applying filters. If FILE is - stdout is used.
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.TP
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.B \-F FILE, \-\-filter=FILE
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Read filter information from FILE.
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Each line of FILE is interpreted like single command line option. If FILE is - stdin is used.
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.TP
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.B FILTER := [ state STATE-FILTER ] [ EXPRESSION ]
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Please take a look at the official documentation (Debian package iproute-doc) for details regarding filters.
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.SH STATE-FILTER
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.B STATE-FILTER
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allows to construct arbitrary set of states to match. Its syntax is sequence of keywords state and exclude followed by identifier of state.
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.TP
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Available identifiers are:
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All standard TCP states:
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.BR established ", " syn-sent ", " syn-recv ", " fin-wait-1 ", " fin-wait-2 ", " time-wait ", " closed ", " close-wait ", " last-ack ", "
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.BR listening " and " closing.
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.B all
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- for all the states
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.B connected
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- all the states except for
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.BR listening " and " closed
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.B synchronized
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- all the
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.B connected
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states except for
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.B syn-sent
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.B bucket
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- states, which are maintained as minisockets, i.e.
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.BR time-wait " and " syn-recv
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.B big
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- opposite to
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.B bucket
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.SH USAGE EXAMPLES
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.TP
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.B ss -t -a
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Display all TCP sockets.
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.TP
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.B ss -t -a -Z
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Display all TCP sockets with process SELinux security contexts.
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.TP
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.B ss -u -a
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Display all UDP sockets.
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.TP
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.B ss -o state established '( dport = :ssh or sport = :ssh )'
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Display all established ssh connections.
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.TP
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.B ss -x src /tmp/.X11-unix/*
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Find all local processes connected to X server.
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.TP
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.B ss -o state fin-wait-1 '( sport = :http or sport = :https )' dst 193.233.7/24
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List all the tcp sockets in state FIN-WAIT-1 for our apache to network 193.233.7/24 and look at their timers.
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.SH SEE ALSO
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.BR ip (8),
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.BR /usr/share/doc/iproute-doc/ss.html " (package iproute<74>doc)",
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.br
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.BR RFC " 793 "
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- https://tools.ietf.org/rfc/rfc793.txt (TCP states)
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.SH AUTHOR
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.I ss
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was written by Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>.
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.PP
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This manual page was written by Michael Prokop <mika@grml.org>
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for the Debian project (but may be used by others).
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