+++ /dev/null
-<!doctype linuxdoc system>
-
-<article>
-
-<title>SS Utility: Quick Intro
-<author>Alexey Kuznetosv, <tt/kuznet@ms2.inr.ac.ru/
-<date>some_negative_number, 20 Sep 2001
-<abstract>
-<tt/ss/ is one another utility to investigate sockets.
-Functionally it is NOT better than <tt/netstat/ combined
-with some perl/awk scripts and though it is surely faster
-it is not enough to make it much better. :-)
-So, stop reading this now and do not waste your time.
-Well, certainly, it proposes some functionality, which current
-netstat is still not able to do, but surely will soon.
-</abstract>
-
-<sect>Why?
-
-<p> <tt>/proc</tt> interface is inadequate, unfortunately.
-When amount of sockets is enough large, <tt/netstat/ or even
-plain <tt>cat /proc/net/tcp/</tt> cause nothing but pains and curses.
-In linux-2.4 the desease became worse: even if amount
-of sockets is small reading <tt>/proc/net/tcp/</tt> is slow enough.
-
-This utility presents a new approach, which is supposed to scale
-well. I am not going to describe technical details here and
-will concentrate on description of the command.
-The only important thing to say is that it is not so bad idea
-to load module <tt/tcp_diag/, which can be found in directory
-<tt/Modules/ of <tt/iproute2/. If you do not make this <tt/ss/
-will work, but it falls back to <tt>/proc</tt> and becomes slow
-like <tt/netstat/, well, a bit faster yet (see section "Some numbers").
-
-<sect>Old news
-
-<p>
-In the simplest form <tt/ss/ is equivalent to netstat
-with some small deviations.
-
-<itemize>
-<item><tt/ss -t -a/ dumps all TCP sockets
-<item><tt/ss -u -a/ dumps all UDP sockets
-<item><tt/ss -w -a/ dumps all RAW sockets
-<item><tt/ss -x -a/ dumps all UNIX sockets
-</itemize>
-
-<p>
-Option <tt/-o/ shows TCP timers state.
-Option <tt/-e/ shows some extended information.
-Etc. etc. etc. Seems, all the options of netstat related to sockets
-are supported. Though not AX.25 and other bizarres. :-)
-If someone wants, he can make support for decnet and ipx.
-Some rudimentary support for them is already present in iproute2 libutils,
-and I will be glad to see these new members.
-
-<p>
-However, standard functionality is a bit different:
-
-<p>
-The first: without option <tt/-a/ sockets in states
-<tt/TIME-WAIT/ and <tt/SYN-RECV/ are skipped too.
-It is more reasonable default, I think.
-
-<p>
-The second: format of UNIX sockets is different. It coincides
-with tcp/udp. Though standard kernel still does not allow to
-see write/read queues and peer address of connected UNIX sockets,
-the patch doing this exists.
-
-<p>
-The third: default is to dump only TCP sockets, rather than all of the types.
-
-<p>
-The next: by default it does not resolve numeric host addresses (like <tt/ip/)!
-Resolving is enabled with option <tt/-r/. Service names, usually stored
-in local files, are resolved by default. Also, if service database
-does not contain references to a port, <tt/ss/ queries system
-<tt/rpcbind/. RPC services are prefixed with <tt/rpc./
-Resolution of services may be suppressed with option <tt/-n/.
-
-<p>
-It does not accept "long" options (I dislike them, sorry).
-So, address family is given with family identifier following
-option <tt/-f/ to be algined to iproute2 conventions.
-Mostly, it is to allow option parser to parse
-addresses correctly, but as side effect it really limits dumping
-to sockets supporting only given family. Option <tt/-A/ followed
-by list of socket tables to dump is also supported.
-Logically, id of socket table is different of _address_ family, which is
-another point of incompatibility. So, id is one of
-<tt/all/, <tt/tcp/, <tt/udp/,
-<tt/raw/, <tt/inet/, <tt/unix/, <tt/packet/, <tt/netlink/. See?
-Well, <tt/inet/ is just abbreviation for <tt/tcp|udp|raw/
-and it is not difficult to guess that <tt/packet/ allows
-to look at packet sockets. Actually, there are also some other abbreviations,
-f.e. <tt/unix_dgram/ selects only datagram UNIX sockets.
-
-<p>
-The next: well, I still do not know. :-)
-
-
-
-
-<sect>Time to talk about new functionality.
-
-<p>It is builtin filtering of socket lists.
-
-<sect1> Filtering by state.
-
-<p>
-<tt/ss/ allows to filter socket states, using keywords
-<tt/state/ and <tt/exclude/, followed by some state
-identifier.
-
-<p>
-State identifier are standard TCP state names (not listed,
-they are useless for you if you already do not know them)
-or abbreviations:
-
-<itemize>
-<item><tt/all/ - for all the states
-<item><tt/bucket/ - for TCP minisockets (<tt/TIME-WAIT|SYN-RECV/)
-<item><tt/big/ - all except for minisockets
-<item><tt/connected/ - not closed and not listening
-<item><tt/synchronized/ - connected and not <tt/SYN-SENT/
-</itemize>
-
-<p>
- F.e. to dump all tcp sockets except <tt/SYN-RECV/:
-
-<tscreen><verb>
- ss exclude SYN-RECV
-</verb></tscreen>
-
-<p>
- If neither <tt/state/ nor <tt/exclude/ directives
- are present,
- state filter defaults to <tt/all/ with option <tt/-a/
- or to <tt/all/,
- excluding listening, syn-recv, time-wait and closed sockets.
-
-<sect1> Filtering by addresses and ports.
-
-<p>
-Option list may contain address/port filter.
-It is boolean expression which consists of boolean operation
-<tt/or/, <tt/and/, <tt/not/ and predicates.
-Actually, all the flavors of names for boolean operations are eaten:
-<tt/&/, <tt/&&/, <tt/|/, <tt/||/, <tt/!/, but do not forget
-about special sense given to these symbols by unix shells and escape
-them correctly, when used from command line.
-
-<p>
-Predicates may be of the folowing kinds:
-
-<itemize>
-<item>A. Address/port match, where address is checked against mask
- and port is either wildcard or exact. It is one of:
-
-<tscreen><verb>
- dst prefix:port
- src prefix:port
- src unix:STRING
- src link:protocol:ifindex
- src nl:channel:pid
-</verb></tscreen>
-
- Both prefix and port may be absent or replaced with <tt/*/,
- which means wildcard. UNIX socket use more powerful scheme
- matching to socket names by shell wildcards. Also, prefixes
- unix: and link: may be omitted, if address family is evident
- from context (with option <tt/-x/ or with <tt/-f unix/
- or with <tt/unix/ keyword)
-
-<p>
- F.e.
-
-<tscreen><verb>
- dst 10.0.0.1
- dst 10.0.0.1:
- dst 10.0.0.1/32:
- dst 10.0.0.1:*
-</verb></tscreen>
- are equivalent and mean socket connected to
- any port on host 10.0.0.1
-
-<tscreen><verb>
- dst 10.0.0.0/24:22
-</verb></tscreen>
- sockets connected to port 22 on network
- 10.0.0.0...255.
-
-<p>
- Note that port separated of address with colon, which creates
- troubles with IPv6 addresses. Generally, we interpret the last
- colon as splitting port. To allow to give IPv6 addresses,
- trick like used in IPv6 HTTP URLs may be used:
-
-<tscreen><verb>
- dst [::1]
-</verb></tscreen>
- are sockets connected to ::1 on any port
-
-<p>
- Another way is <tt/dst ::1/128/. / helps to understand that
- colon is part of IPv6 address.
-
-<p>
- Now we can add another alias for <tt/dst 10.0.0.1/:
- <tt/dst [10.0.0.1]/. :-)
-
-<p> Address may be a DNS name. In this case all the addresses are looked
- up (in all the address families, if it is not limited by option <tt/-f/
- or special address prefix <tt/inet:/, <tt/inet6/) and resulting
- expression is <tt/or/ over all of them.
-
-<item> B. Port expressions:
-<tscreen><verb>
- dport >= :1024
- dport != :22
- sport < :32000
-</verb></tscreen>
- etc.
-
- All the relations: <tt/</, <tt/>/, <tt/=/, <tt/>=/, <tt/=/, <tt/==/,
- <tt/!=/, <tt/eq/, <tt/ge/, <tt/lt/, <tt/ne/...
- Use variant which you like more, but not forget to escape special
- characters when typing them in command line. :-)
-
- Note that port number syntactically coincides to the case A!
- You may even add an IP address, but it will not participate
- incomparison, except for <tt/==/ and <tt/!=/, which are equivalent
- to corresponding predicates of type A. F.e.
-<p>
-<tt/dst 10.0.0.1:22/
- is equivalent to <tt/dport eq 10.0.0.1:22/
- and
- <tt/not dst 10.0.0.1:22/ is equivalent to
- <tt/dport neq 10.0.0.1:22/
-
-<item>C. Keyword <tt/autobound/. It matches to sockets bound automatically
- on local system.
-
-</itemize>
-
-
-<sect> Examples
-
-<p>
-<itemize>
-<item>1. List all the tcp sockets in state <tt/FIN-WAIT-1/ for our apache
- to network 193.233.7/24 and look at their timers:
-
-<tscreen><verb>
- ss -o state fin-wait-1 \( sport = :http or sport = :https \) \
- dst 193.233.7/24
-</verb></tscreen>
-
- Oops, forgot to say that missing logical operation is
- equivalent to <tt/and/.
-
-<item> 2. Well, now look at the rest...
-
-<tscreen><verb>
- ss -o excl fin-wait-1
- ss state fin-wait-1 \( sport neq :http and sport neq :https \) \
- or not dst 193.233.7/24
-</verb></tscreen>
-
- Note that we have to do _two_ calls of ss to do this.
- State match is always anded to address/port match.
- The reason for this is purely technical: ss does fast skip of
- not matching states before parsing addresses and I consider the
- ability to skip fastly gobs of time-wait and syn-recv sockets
- as more important than logical generality.
-
-<item> 3. So, let's look at all our sockets using autobound ports:
-
-<tscreen><verb>
- ss -a -A all autobound
-</verb></tscreen>
-
-
-<item> 4. And eventually find all the local processes connected
- to local X servers:
-
-<tscreen><verb>
- ss -xp dst "/tmp/.X11-unix/*"
-</verb></tscreen>
-
- Pardon, this does not work with current kernel, patching is required.
- But we still can look at server side:
-
-<tscreen><verb>
- ss -x src "/tmp/.X11-unix/*"
-</verb></tscreen>
-
-</itemize>
-
-
-<sect> Returning to ground: real manual
-
-<p>
-<sect1> Command arguments
-
-<p> General format of arguments to <tt/ss/ is:
-
-<tscreen><verb>
- ss [ OPTIONS ] [ STATE-FILTER ] [ ADDRESS-FILTER ]
-</verb></tscreen>
-
-<sect2><tt/OPTIONS/
-<p> <tt/OPTIONS/ is list of single letter options, using common unix
-conventions.
-
-<itemize>
-<item><tt/-h/ - show help page
-<item><tt/-?/ - the same, of course
-<item><tt/-v/, <tt/-V/ - print version of <tt/ss/ and exit
-<item><tt/-s/ - print summary statistics. This option does not parse
-socket lists obtaining summary from various sources. It is useful
-when amount of sockets is so huge that parsing <tt>/proc/net/tcp</tt>
-is painful.
-<item><tt/-D FILE/ - do not display anything, just dump raw information
-about TCP sockets to <tt/FILE/ after applying filters. If <tt/FILE/ is <tt/-/
-<tt/stdout/ is used.
-<item><tt/-F FILE/ - read continuation of filter from <tt/FILE/.
-Each line of <tt/FILE/ is interpreted like single command line option.
-If <tt/FILE/ is <tt/-/ <tt/stdin/ is used.
-<item><tt/-r/ - try to resolve numeric address/ports
-<item><tt/-n/ - do not try to resolve ports
-<item><tt/-o/ - show some optional information, f.e. TCP timers
-<item><tt/-i/ - show some infomration specific to TCP (RTO, congestion
-window, slow start threshould etc.)
-<item><tt/-e/ - show even more optional information
-<item><tt/-m/ - show extended information on memory used by the socket.
-It is available only with <tt/tcp_diag/ enabled.
-<item><tt/-p/ - show list of processes owning the socket
-<item><tt/-f FAMILY/ - default address family used for parsing addresses.
- Also this option limits listing to sockets supporting
- given address family. Currently the following families
- are supported: <tt/unix/, <tt/inet/, <tt/inet6/, <tt/link/,
- <tt/netlink/.
-<item><tt/-4/ - alias for <tt/-f inet/
-<item><tt/-6/ - alias for <tt/-f inet6/
-<item><tt/-0/ - alias for <tt/-f link/
-<item><tt/-A LIST-OF-TABLES/ - list of socket tables to dump, separated
- by commas. The following identifiers are understood:
- <tt/all/, <tt/inet/, <tt/tcp/, <tt/udp/, <tt/raw/,
- <tt/unix/, <tt/packet/, <tt/netlink/, <tt/unix_dgram/,
- <tt/unix_stream/, <tt/packet_raw/, <tt/packet_dgram/.
-<item><tt/-x/ - alias for <tt/-A unix/
-<item><tt/-t/ - alias for <tt/-A tcp/
-<item><tt/-u/ - alias for <tt/-A udp/
-<item><tt/-w/ - alias for <tt/-A raw/
-<item><tt/-a/ - show sockets of all the states. By default sockets
- in states <tt/LISTEN/, <tt/TIME-WAIT/, <tt/SYN_RECV/
- and <tt/CLOSE/ are skipped.
-<item><tt/-l/ - show only sockets in state <tt/LISTEN/
-</itemize>
-
-<sect2><tt/STATE-FILTER/
-
-<p><tt/STATE-FILTER/ allows to construct arbitrary set of
-states to match. Its syntax is sequence of keywords <tt/state/
-and <tt/exclude/ followed by identifier of state.
-Available identifiers are:
-
-<p>
-<itemize>
-<item> All standard TCP states: <tt/established/, <tt/syn-sent/,
-<tt/syn-recv/, <tt/fin-wait-1/, <tt/fin-wait-2/, <tt/time-wait/,
-<tt/closed/, <tt/close-wait/, <tt/last-ack/, <tt/listen/ and <tt/closing/.
-
-<item><tt/all/ - for all the states
-<item><tt/connected/ - all the states except for <tt/listen/ and <tt/closed/
-<item><tt/synchronized/ - all the <tt/connected/ states except for
-<tt/syn-sent/
-<item><tt/bucket/ - states, which are maintained as minisockets, i.e.
-<tt/time-wait/ and <tt/syn-recv/.
-<item><tt/big/ - opposite to <tt/bucket/
-</itemize>
-
-<sect2><tt/ADDRESS_FILTER/
-
-<p><tt/ADDRESS_FILTER/ is boolean expression with operations <tt/and/, <tt/or/
-and <tt/not/, which can be abbreviated in C style f.e. as <tt/&/,
-<tt/&&/.
-
-<p>
-Predicates check socket addresses, both local and remote.
-There are the following kinds of predicates:
-
-<itemize>
-<item> <tt/dst ADDRESS_PATTERN/ - matches remote address and port
-<item> <tt/src ADDRESS_PATTERN/ - matches local address and port
-<item> <tt/dport RELOP PORT/ - compares remote port to a number
-<item> <tt/sport RELOP PORT/ - compares local port to a number
-<item> <tt/autobound/ - checks that socket is bound to an ephemeral
- port
-</itemize>
-
-<p><tt/RELOP/ is some of <tt/<=/, <tt/>=/, <tt/==/ etc.
-To make this more convinient for use in unix shell, alphabetic
-FORTRAN-like notations <tt/le/, <tt/gt/ etc. are accepted as well.
-
-<p>The format and semantics of <tt/ADDRESS_PATTERN/ depends on address
-family.
-
-<itemize>
-<item><tt/inet/ - <tt/ADDRESS_PATTERN/ consists of IP prefix, optionally
-followed by colon and port. If prefix or port part is absent or replaced
-with <tt/*/, this means wildcard match.
-<item><tt/inet6/ - The same as <tt/inet/, only prefix refers to an IPv6
-address. Unlike <tt/inet/ colon becomes ambiguous, so that <tt/ss/ allows
-to use scheme, like used in URLs, where address is suppounded with
-<tt/[/ ... <tt/]/.
-<item><tt/unix/ - <tt/ADDRESS_PATTERN/ is shell-style wildcard.
-<item><tt/packet/ - format looks like <tt/inet/, only interface index
-stays instead of port and link layer protocol id instead of address.
-<item><tt/netlink/ - format looks like <tt/inet/, only socket pid
-stays instead of port and netlink channel instead of address.
-</itemize>
-
-<p><tt/PORT/ is syntactically <tt/ADDRESS_PATTERN/ with wildcard
-address part. Certainly, it is undefined for UNIX sockets.
-
-<sect1> Environment variables
-
-<p>
-<tt/ss/ allows to change source of information using various
-environment variables:
-
-<p>
-<itemize>
-<item> <tt/PROC_SLABINFO/ to override <tt>/proc/slabinfo</tt>
-<item> <tt/PROC_NET_TCP/ to override <tt>/proc/net/tcp</tt>
-<item> <tt/PROC_NET_UDP/ to override <tt>/proc/net/udp</tt>
-<item> etc.
-</itemize>
-
-<p>
-Variable <tt/PROC_ROOT/ allows to change root of all the <tt>/proc/</tt>
-hierarchy.
-
-<p>
-Variable <tt/TCPDIAG_FILE/ prescribes to open a file instead of
-requesting kernel to dump information about TCP sockets.
-
-
-<p> This option is used mainly to investigate bug reports,
-when dumps of files usually found in <tt>/proc/</tt> are recevied
-by e-mail.
-
-<sect1> Output format
-
-<p>Six columns. The first is <tt/Netid/, it denotes socket type and
-transport protocol, when it is ambiguous: <tt/tcp/, <tt/udp/, <tt/raw/,
-<tt/u_str/ is abbreviation for <tt/unix_stream/, <tt/u_dgr/ for UNIX
-datagram sockets, <tt/nl/ for netlink, <tt/p_raw/ and <tt/p_dgr/ for
-raw and datagram packet sockets. This column is optional, it will
-be hidden, if filter selects an unique netid.
-
-<p>
-The second column is <tt/State/. Socket state is displayed here.
-The names are standard TCP names, except for <tt/UNCONN/, which
-cannot happen for TCP, but normal for not connected sockets
-of another types. Again, this column can be hidden.
-
-<p>
-Then two columns (<tt/Recv-Q/ and <tt/Send-Q/) showing amount of data
-queued for receive and transmit.
-
-<p>
-And the last two columns display local address and port of the socket
-and its peer address, if the socket is connected.
-
-<p>
-If options <tt/-o/, <tt/-e/ or <tt/-p/ were given, options are
-displayed not in fixed positions but separated by spaces pairs:
-<tt/option:value/. If value is not a single number, it is presented
-as list of values, enclosed to <tt/(/ ... <tt/)/ and separated with
-commas. F.e.
-
-<tscreen><verb>
- timer:(keepalive,111min,0)
-</verb></tscreen>
-is typical format for TCP timer (option <tt/-o/).
-
-<tscreen><verb>
- users:((X,113,3))
-</verb></tscreen>
-is typical for list of users (option <tt/-p/).
-
-
-<sect>Some numbers
-
-<p>
-Well, let us use <tt/pidentd/ and a tool <tt/ibench/ to measure
-its performance. It is 30 requests per second here. Nothing to test,
-it is too slow. OK, let us patch pidentd with patch from directory
-Patches. After this it handles about 4300 requests per second
-and becomes handy tool to pollute socket tables with lots of timewait
-buckets.
-
-<p>
-So, each test starts from pollution tables with 30000 sockets
-and then doing full dump of the table piped to wc and measuring
-timings with time:
-
-<p>Results:
-
-<itemize>
-<item> <tt/netstat -at/ - 15.6 seconds
-<item> <tt/ss -atr/, but without <tt/tcp_diag/ - 5.4 seconds
-<item> <tt/ss -atr/ with <tt/tcp_diag/ - 0.47 seconds
-</itemize>
-
-No comments. Though one comment is necessary, most of time
-without <tt/tcp_diag/ is wasted inside kernel with completely
-blocked networking. More than 10 seconds, yes. <tt/tcp_diag/
-does the same work for 100 milliseconds of system time.
-
-</article>
git://git.onelab.eu / iproute2.git / blobdiff