# PODNAME: Config::Model::models::Systemd::Section::Socket
# ABSTRACT:  Configuration class Systemd::Section::Socket
=head1 NAME

Config::Model::models::Systemd::Section::Socket - Configuration class Systemd::Section::Socket

=head1 DESCRIPTION

Configuration classes used by L<Config::Model>

A unit configuration file whose name ends in
C<.socket> encodes information about an IPC or
network socket or a file system FIFO controlled and supervised by
systemd, for socket-based activation.
This man page lists the configuration options specific to
this unit type. See
L<systemd.unit(5)|"https://manpages.debian.org/cgi-bin/man.cgi?query=systemd.unit&sektion=5&manpath=Debian+unstable+sid">
for the common options of all unit configuration files. The common
configuration items are configured in the generic [Unit] and
[Install] sections. The socket specific configuration options are
configured in the [Socket] section.
Additional options are listed in
L<systemd.exec(5)|"https://manpages.debian.org/cgi-bin/man.cgi?query=systemd.exec&sektion=5&manpath=Debian+unstable+sid">,
which define the execution environment the
ExecStartPre=, ExecStartPost=,
ExecStopPre= and ExecStopPost=
commands are executed in, and in
L<systemd.kill(5)|"https://manpages.debian.org/cgi-bin/man.cgi?query=systemd.kill&sektion=5&manpath=Debian+unstable+sid">,
which define the way the processes are terminated, and in
L<systemd.resource-control(5)|"https://manpages.debian.org/cgi-bin/man.cgi?query=systemd.resource-control&sektion=5&manpath=Debian+unstable+sid">,
which configure resource control settings for the processes of the
socket.
For each socket file, a matching service file must exist,
describing the service to start on incoming traffic on the socket
(see
L<systemd.service(5)|"https://manpages.debian.org/cgi-bin/man.cgi?query=systemd.service&sektion=5&manpath=Debian+unstable+sid">
for more information about .service files). The name of the
.service unit is by default the same as the name of the .socket
unit, but can be altered with the Service= option
described below. Depending on the setting of the
Accept= option described below, this .service
unit must either be named like the .socket unit, but with the
suffix replaced, unless overridden with Service=;
or it must be a template unit named the same way. Example: a
socket file foo.socket needs a matching
service foo.service if
Accept=false is set. If
Accept=true is set, a service template file
foo@.service must exist from which services
are instantiated for each incoming connection.
Unless DefaultDependencies= is set to
false, socket units will implicitly have
dependencies of type Requires= and
After= on sysinit.target
as well as dependencies of type Conflicts= and
Before= on
shutdown.target. These ensure that socket
units pull in basic system initialization, and are terminated
cleanly prior to system shutdown. Only sockets involved with early
boot or late system shutdown should disable this option.
Socket units will have a Before=
dependency on the service which they trigger added implicitly. No
implicit WantedBy= or
RequiredBy= dependency from the socket to the
service is added. This means that the service may be started
without the socket, in which case it must be able to open sockets
by itself. To prevent this, an explicit
Requires= dependency may be added.
Socket units may be used to implement on-demand starting of
services, as well as parallelized starting of services. See the
blog stories linked at the end for an introduction.
Note that the daemon software configured for socket
activation with socket units needs to be able to accept sockets
from systemd, either via systemd's native socket passing interface
(see
L<sd_listen_fds(3)|"https://manpages.debian.org/cgi-bin/man.cgi?query=sd_listen_fds&sektion=3&manpath=Debian+unstable+sid">
for details) or via the traditional
L<inetd(8)|"https://manpages.debian.org/cgi-bin/man.cgi?query=inetd&sektion=8&manpath=Debian+unstable+sid">-style
socket passing (i.e. sockets passed in via standard input and
output, using StandardInput=socket in the
service file).
This configuration class was generated from systemd documentation.
by L<parse-man.pl|https://github.com/dod38fr/config-model-systemd/contrib/parse-man.pl>


=head1 Elements

=head2 ListenStream

Specifies an address to listen on for a stream
(SOCK_STREAM), datagram
(SOCK_DGRAM), or sequential packet
(SOCK_SEQPACKET) socket, respectively.
The address can be written in various formats:If the address starts with a slash
(C</>), it is read as file system socket in
the AF_UNIX socket family.If the address starts with an at symbol
(C<@>), it is read as abstract namespace
socket in the AF_UNIX family. The
C<@> is replaced with a
NUL character before binding. For
details, see
L<unix(7)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>unix&C<sektion>7&C<manpath>Debian+unstable+sid">.If the address string is a single number, it is read as
port number to listen on via IPv6. Depending on the value of
C<BindIPv6Only> (see below) this might result
in the service being available via both IPv6 and IPv4
(default) or just via IPv6.
If the address string is a string in the format
v.w.x.y:z, it is read as IPv4 specifier for listening on an
address v.w.x.y on a port z.If the address string is a string in the format [x]:y,
it is read as IPv6 address x on a port y. Note that this might
make the service available via IPv4, too, depending on the
C<BindIPv6Only> setting (see below).
Note that SOCK_SEQPACKET (i.e.
C<ListenSequentialPacket>) is only available
for AF_UNIX sockets.
SOCK_STREAM (i.e.
C<ListenStream>) when used for IP sockets
refers to TCP sockets, SOCK_DGRAM (i.e.
C<ListenDatagram>) to UDP.These options may be specified more than once, in which
case incoming traffic on any of the sockets will trigger
service activation, and all listed sockets will be passed to
the service, regardless of whether there is incoming traffic
on them or not. If the empty string is assigned to any of
these options, the list of addresses to listen on is reset,
all prior uses of any of these options will have no
effect.It is also possible to have more than one socket unit
for the same service when using C<Service>,
and the service will receive all the sockets configured in all
the socket units. Sockets configured in one unit are passed in
the order of configuration, but no ordering between socket
units is specified.If an IP address is used here, it is often desirable to
listen on it before the interface it is configured on is up
and running, and even regardless of whether it will be up and
running at any point. To deal with this, it is recommended to
set the C<FreeBind> option described
below. I<< Optional. Type list of uniline.  >> 

=head2 ListenDatagram

Specifies an address to listen on for a stream
(SOCK_STREAM), datagram
(SOCK_DGRAM), or sequential packet
(SOCK_SEQPACKET) socket, respectively.
The address can be written in various formats:If the address starts with a slash
(C</>), it is read as file system socket in
the AF_UNIX socket family.If the address starts with an at symbol
(C<@>), it is read as abstract namespace
socket in the AF_UNIX family. The
C<@> is replaced with a
NUL character before binding. For
details, see
L<unix(7)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>unix&C<sektion>7&C<manpath>Debian+unstable+sid">.If the address string is a single number, it is read as
port number to listen on via IPv6. Depending on the value of
C<BindIPv6Only> (see below) this might result
in the service being available via both IPv6 and IPv4
(default) or just via IPv6.
If the address string is a string in the format
v.w.x.y:z, it is read as IPv4 specifier for listening on an
address v.w.x.y on a port z.If the address string is a string in the format [x]:y,
it is read as IPv6 address x on a port y. Note that this might
make the service available via IPv4, too, depending on the
C<BindIPv6Only> setting (see below).
Note that SOCK_SEQPACKET (i.e.
C<ListenSequentialPacket>) is only available
for AF_UNIX sockets.
SOCK_STREAM (i.e.
C<ListenStream>) when used for IP sockets
refers to TCP sockets, SOCK_DGRAM (i.e.
C<ListenDatagram>) to UDP.These options may be specified more than once, in which
case incoming traffic on any of the sockets will trigger
service activation, and all listed sockets will be passed to
the service, regardless of whether there is incoming traffic
on them or not. If the empty string is assigned to any of
these options, the list of addresses to listen on is reset,
all prior uses of any of these options will have no
effect.It is also possible to have more than one socket unit
for the same service when using C<Service>,
and the service will receive all the sockets configured in all
the socket units. Sockets configured in one unit are passed in
the order of configuration, but no ordering between socket
units is specified.If an IP address is used here, it is often desirable to
listen on it before the interface it is configured on is up
and running, and even regardless of whether it will be up and
running at any point. To deal with this, it is recommended to
set the C<FreeBind> option described
below. I<< Optional. Type list of uniline.  >> 

=head2 ListenSequentialPacket

Specifies an address to listen on for a stream
(SOCK_STREAM), datagram
(SOCK_DGRAM), or sequential packet
(SOCK_SEQPACKET) socket, respectively.
The address can be written in various formats:If the address starts with a slash
(C</>), it is read as file system socket in
the AF_UNIX socket family.If the address starts with an at symbol
(C<@>), it is read as abstract namespace
socket in the AF_UNIX family. The
C<@> is replaced with a
NUL character before binding. For
details, see
L<unix(7)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>unix&C<sektion>7&C<manpath>Debian+unstable+sid">.If the address string is a single number, it is read as
port number to listen on via IPv6. Depending on the value of
C<BindIPv6Only> (see below) this might result
in the service being available via both IPv6 and IPv4
(default) or just via IPv6.
If the address string is a string in the format
v.w.x.y:z, it is read as IPv4 specifier for listening on an
address v.w.x.y on a port z.If the address string is a string in the format [x]:y,
it is read as IPv6 address x on a port y. Note that this might
make the service available via IPv4, too, depending on the
C<BindIPv6Only> setting (see below).
Note that SOCK_SEQPACKET (i.e.
C<ListenSequentialPacket>) is only available
for AF_UNIX sockets.
SOCK_STREAM (i.e.
C<ListenStream>) when used for IP sockets
refers to TCP sockets, SOCK_DGRAM (i.e.
C<ListenDatagram>) to UDP.These options may be specified more than once, in which
case incoming traffic on any of the sockets will trigger
service activation, and all listed sockets will be passed to
the service, regardless of whether there is incoming traffic
on them or not. If the empty string is assigned to any of
these options, the list of addresses to listen on is reset,
all prior uses of any of these options will have no
effect.It is also possible to have more than one socket unit
for the same service when using C<Service>,
and the service will receive all the sockets configured in all
the socket units. Sockets configured in one unit are passed in
the order of configuration, but no ordering between socket
units is specified.If an IP address is used here, it is often desirable to
listen on it before the interface it is configured on is up
and running, and even regardless of whether it will be up and
running at any point. To deal with this, it is recommended to
set the C<FreeBind> option described
below. I<< Optional. Type list of uniline.  >> 

=head2 ListenFIFO

Specifies a file system FIFO to listen on.
This expects an absolute file system path as argument.
Behavior otherwise is very similar to the
C<ListenDatagram> directive
above. I<< Optional. Type uniline.  >> 

=head2 ListenSpecial

Specifies a special file in the file system to
listen on. This expects an absolute file system path as
argument. Behavior otherwise is very similar to the
C<ListenFIFO> directive above. Use this to
open character device nodes as well as special files in
/proc and
/sys. I<< Optional. Type uniline.  >> 

=head2 ListenNetlink

Specifies a Netlink family to create a socket
for to listen on. This expects a short string referring to the
AF_NETLINK family name (such as
audit or kobject-uevent)
as argument, optionally suffixed by a whitespace followed by a
multicast group integer. Behavior otherwise is very similar to
the C<ListenDatagram> directive
above. I<< Optional. Type uniline.  >> 

=head2 ListenMessageQueue

Specifies a POSIX message queue name to listen
on. This expects a valid message queue name (i.e. beginning
with /). Behavior otherwise is very similar to the
C<ListenFIFO> directive above. On Linux
message queue descriptors are actually file descriptors and
can be inherited between processes. I<< Optional. Type uniline.  >> 

=head2 ListenUSBFunction

Specifies a USB
FunctionFS endpoint location to listen on, for
implementation of USB gadget functions. This expects an
absolute file system path as the argument. Behavior otherwise
is very similar to the C<ListenFIFO>
directive above. Use this to open the FunctionFS endpoint
ep0. When using this option, the
activated service has to have the
C<USBFunctionDescriptors> and
C<USBFunctionStrings> options set.
I<< Optional. Type uniline.  >> 

=head2 BindIPv6Only

Takes a one of default,
both or ipv6-only. Controls
the IPV6_V6ONLY socket option (see
L<ipv6(7)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>ipv6&C<sektion>7&C<manpath>Debian+unstable+sid">
for details). If both, IPv6 sockets bound
will be accessible via both IPv4 and IPv6. If
ipv6-only, they will be accessible via IPv6
only. If default (which is the default,
surprise!), the system wide default setting is used, as
controlled by
/proc/sys/net/ipv6/bindv6only, which in
turn defaults to the equivalent of
both. I<< Optional. Type uniline.  >> 

=head2 Backlog

Takes an unsigned integer argument. Specifies
the number of connections to queue that have not been accepted
yet. This setting matters only for stream and sequential
packet sockets. See
L<listen(2)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>listen&C<sektion>2&C<manpath>Debian+unstable+sid">
for details. Defaults to SOMAXCONN (128). I<< Optional. Type uniline.  >> 

=head2 BindToDevice

Specifies a network interface name to bind
this socket to. If set, traffic will only be accepted from the
specified network interfaces. This controls the
SO_BINDTODEVICE socket option (see L<socket(7)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>socket&C<sektion>7&C<manpath>Debian+unstable+sid">
for details). If this option is used, an automatic dependency
from this socket unit on the network interface device unit
(L<systemd.device(5)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>systemd.device&C<sektion>5&C<manpath>Debian+unstable+sid">
is created. Note that setting this parameter might result in
additional dependencies to be added to the unit (see
above). I<< Optional. Type uniline.  >> 

=head2 SocketUser

Takes a UNIX user/group name. When specified,
all AF_UNIX sockets and FIFO nodes in the file system are
owned by the specified user and group. If unset (the default),
the nodes are owned by the root user/group (if run in system
context) or the invoking user/group (if run in user context).
If only a user is specified but no group, then the group is
derived from the user's default group. I<< Optional. Type uniline.  >> 

=head2 SocketGroup

Takes a UNIX user/group name. When specified,
all AF_UNIX sockets and FIFO nodes in the file system are
owned by the specified user and group. If unset (the default),
the nodes are owned by the root user/group (if run in system
context) or the invoking user/group (if run in user context).
If only a user is specified but no group, then the group is
derived from the user's default group. I<< Optional. Type uniline.  >> 

=head2 SocketMode

If listening on a file system socket or FIFO,
this option specifies the file system access mode used when
creating the file node. Takes an access mode in octal
notation. Defaults to 0666. I<< Optional. Type uniline.  >> 

=head2 DirectoryMode

If listening on a file system socket or FIFO,
the parent directories are automatically created if needed.
This option specifies the file system access mode used when
creating these directories. Takes an access mode in octal
notation. Defaults to 0755. I<< Optional. Type uniline.  >> 

=head2 Accept

Takes a boolean argument. If true, a service
instance is spawned for each incoming connection and only the
connection socket is passed to it. If false, all listening
sockets themselves are passed to the started service unit, and
only one service unit is spawned for all connections (also see
above). This value is ignored for datagram sockets and FIFOs
where a single service unit unconditionally handles all
incoming traffic. Defaults to false. For
performance reasons, it is recommended to write new daemons
only in a way that is suitable for
C<Accept>false. A daemon listening on an
AF_UNIX socket may, but does not need to,
call
L<close(2)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>close&C<sektion>2&C<manpath>Debian+unstable+sid">
on the received socket before exiting. However, it must not
unlink the socket from a file system. It should not invoke
L<shutdown(2)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>shutdown&C<sektion>2&C<manpath>Debian+unstable+sid">
on sockets it got with C<Accept>false, but it
may do so for sockets it got with
C<Accept>true set. Setting
C<Accept>true is mostly useful to allow
daemons designed for usage with
L<inetd(8)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>inetd&C<sektion>8&C<manpath>Debian+unstable+sid">
to work unmodified with systemd socket
activation.For IPv4 and IPv6 connections, the REMOTE_ADDR
environment variable will contain the remote IP address, and REMOTE_PORT
will contain the remote port. This is the same as the format used by CGI.
For SOCK_RAW, the port is the IP protocol. I<< Optional. Type boolean.  >> 

=head2 Writable

Takes a boolean argument. May only be used in
conjunction with C<ListenSpecial>. If true,
the specified special file is opened in read-write mode, if
false, in read-only mode. Defaults to false. I<< Optional. Type boolean.  >> 

=head2 MaxConnections

The maximum number of connections to
simultaneously run services instances for, when
C<Accept>true is set. If more concurrent
connections are coming in, they will be refused until at least
one existing connection is terminated. This setting has no
effect on sockets configured with
C<Accept>false or datagram sockets. Defaults to
64. I<< Optional. Type uniline.  >> 

=head2 KeepAlive

Takes a boolean argument. If true, the TCP/IP
stack will send a keep alive message after 2h (depending on
the configuration of
/proc/sys/net/ipv4/tcp_keepalive_time)
for all TCP streams accepted on this socket. This controls the
SO_KEEPALIVE socket option (see
L<socket(7)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>socket&C<sektion>7&C<manpath>Debian+unstable+sid">
and the TCP
Keepalive HOWTO for details.) Defaults to
false. I<< Optional. Type boolean.  >> 

=head2 KeepAliveTimeSec

Takes time (in seconds) as argument. The connection needs to remain
idle before TCP starts sending keepalive probes. This controls the TCP_KEEPIDLE
socket option (see
L<socket(7)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>socket&C<sektion>7&C<manpath>Debian+unstable+sid">
and the TCP
Keepalive HOWTO for details.)
Defaults value is 7200 seconds (2 hours). I<< Optional. Type integer.  >> 

=head2 KeepAliveIntervalSec

Takes time (in seconds) as argument between
individual keepalive probes, if the socket option SO_KEEPALIVE
has been set on this socket. This controls
the TCP_KEEPINTVL socket option (see
L<socket(7)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>socket&C<sektion>7&C<manpath>Debian+unstable+sid">
and the TCP
Keepalive HOWTO for details.) Defaults value is 75
seconds. I<< Optional. Type integer.  >> 

=head2 KeepAliveProbes

Takes an integer as argument. It is the number of
unacknowledged probes to send before considering the
connection dead and notifying the application layer. This
controls the TCP_KEEPCNT socket option (see
L<socket(7)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>socket&C<sektion>7&C<manpath>Debian+unstable+sid">
and the TCP
Keepalive HOWTO for details.) Defaults value is
9. I<< Optional. Type integer.  >> 

=head2 NoDelay

Takes a boolean argument. TCP Nagle's
algorithm works by combining a number of small outgoing
messages, and sending them all at once. This controls the
TCP_NODELAY socket option (see
L<tcp(7)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>tcp&C<sektion>7&C<manpath>Debian+unstable+sid">
Defaults to false. I<< Optional. Type boolean.  >> 

=head2 Priority

Takes an integer argument controlling the
priority for all traffic sent from this socket. This controls
the SO_PRIORITY socket option (see
L<socket(7)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>socket&C<sektion>7&C<manpath>Debian+unstable+sid">
for details.). I<< Optional. Type integer.  >> 

=head2 DeferAcceptSec

Takes time (in seconds) as argument. If set,
the listening process will be awakened only when data arrives
on the socket, and not immediately when connection is
established. When this option is set, the
TCP_DEFER_ACCEPT socket option will be
used (see
L<tcp(7)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>tcp&C<sektion>7&C<manpath>Debian+unstable+sid">),
and the kernel will ignore initial ACK packets without any
data. The argument specifies the approximate amount of time
the kernel should wait for incoming data before falling back
to the normal behavior of honouring empty ACK packets. This
option is beneficial for protocols where the client sends the
data first (e.g. HTTP, in contrast to SMTP), because the
server process will not be woken up unnecessarily before it
can take any action.
If the client also uses the
TCP_DEFER_ACCEPT option, the latency of
the initial connection may be reduced, because the kernel will
send data in the final packet establishing the connection (the
third packet in the "three-way handshake").Disabled by default. I<< Optional. Type integer.  >> 

=head2 ReceiveBuffer

Takes an integer argument controlling the
receive or send buffer sizes of this socket, respectively.
This controls the SO_RCVBUF and SO_SNDBUF socket options (see
L<socket(7)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>socket&C<sektion>7&C<manpath>Debian+unstable+sid">
for details.). The usual suffixes K, M, G are supported and
are understood to the base of 1024. I<< Optional. Type integer.  >> 

=head2 SendBuffer

Takes an integer argument controlling the
receive or send buffer sizes of this socket, respectively.
This controls the SO_RCVBUF and SO_SNDBUF socket options (see
L<socket(7)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>socket&C<sektion>7&C<manpath>Debian+unstable+sid">
for details.). The usual suffixes K, M, G are supported and
are understood to the base of 1024. I<< Optional. Type integer.  >> 

=head2 IPTOS

Takes an integer argument controlling the IP
Type-Of-Service field for packets generated from this socket.
This controls the IP_TOS socket option (see
L<ip(7)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>ip&C<sektion>7&C<manpath>Debian+unstable+sid">
for details.). Either a numeric string or one of
low-delay, throughput,
reliability or low-cost may
be specified. I<< Optional. Type integer.  >> 

=head2 IPTTL

Takes an integer argument controlling the IPv4
Time-To-Live/IPv6 Hop-Count field for packets generated from
this socket. This sets the IP_TTL/IPV6_UNICAST_HOPS socket
options (see
L<ip(7)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>ip&C<sektion>7&C<manpath>Debian+unstable+sid">
and
L<ipv6(7)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>ipv6&C<sektion>7&C<manpath>Debian+unstable+sid">
for details.) I<< Optional. Type integer.  >> 

=head2 Mark

Takes an integer value. Controls the firewall
mark of packets generated by this socket. This can be used in
the firewall logic to filter packets from this socket. This
sets the SO_MARK socket option. See
L<iptables(8)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>iptables&C<sektion>8&C<manpath>Debian+unstable+sid">
for details. I<< Optional. Type integer.  >> 

=head2 ReusePort

Takes a boolean value. If true, allows
multiple
L<bind(2)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>bind&C<sektion>2&C<manpath>Debian+unstable+sid">s
to this TCP or UDP port. This controls the SO_REUSEPORT socket
option. See
L<socket(7)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>socket&C<sektion>7&C<manpath>Debian+unstable+sid">
for details. I<< Optional. Type boolean.  >> 

=head2 SmackLabel

Takes a string value. Controls the extended
attributes C<security.SMACK64>,
C<security.SMACK64IPIN> and
C<security.SMACK64IPOUT>, respectively, i.e.
the security label of the FIFO, or the security label for the
incoming or outgoing connections of the socket, respectively.
See Smack.txt
for details. I<< Optional. Type uniline.  >> 

=head2 SmackLabelIPIn

Takes a string value. Controls the extended
attributes C<security.SMACK64>,
C<security.SMACK64IPIN> and
C<security.SMACK64IPOUT>, respectively, i.e.
the security label of the FIFO, or the security label for the
incoming or outgoing connections of the socket, respectively.
See Smack.txt
for details. I<< Optional. Type uniline.  >> 

=head2 SmackLabelIPOut

Takes a string value. Controls the extended
attributes C<security.SMACK64>,
C<security.SMACK64IPIN> and
C<security.SMACK64IPOUT>, respectively, i.e.
the security label of the FIFO, or the security label for the
incoming or outgoing connections of the socket, respectively.
See Smack.txt
for details. I<< Optional. Type uniline.  >> 

=head2 SELinuxContextFromNet

Takes a boolean argument. When true, systemd
will attempt to figure out the SELinux label used for the
instantiated service from the information handed by the peer
over the network. Note that only the security level is used
from the information provided by the peer. Other parts of the
resulting SELinux context originate from either the target
binary that is effectively triggered by socket unit or from
the value of the C<SELinuxContext> option.
This configuration option only affects sockets with
C<Accept> mode set to
C<true>. Also note that this option is useful
only when MLS/MCS SELinux policy is deployed. Defaults to
C<false>. I<< Optional. Type boolean.  >> 

=head2 PipeSize

Takes a size in bytes. Controls the pipe
buffer size of FIFOs configured in this socket unit. See
L<fcntl(2)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>fcntl&C<sektion>2&C<manpath>Debian+unstable+sid">
for details. The usual suffixes K, M, G are supported and are
understood to the base of 1024. I<< Optional. Type uniline.  >> 

=head2 MessageQueueMaxMessages

These two settings take integer values and
control the mq_maxmsg field or the mq_msgsize field,
respectively, when creating the message queue. Note that
either none or both of these variables need to be set. See
L<mq_setattr(3)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>mq_setattr&C<sektion>3&C<manpath>Debian+unstable+sid">
for details. I<< Optional. Type uniline.  >> 

=head2 FreeBind

Takes a boolean value. Controls whether the
socket can be bound to non-local IP addresses. This is useful
to configure sockets listening on specific IP addresses before
those IP addresses are successfully configured on a network
interface. This sets the IP_FREEBIND socket option. For
robustness reasons it is recommended to use this option
whenever you bind a socket to a specific IP address. Defaults
to false. I<< Optional. Type boolean.  >> 

=head2 Transparent

Takes a boolean value. Controls the
IP_TRANSPARENT socket option. Defaults to
false. I<< Optional. Type boolean.  >> 

=head2 Broadcast

Takes a boolean value. This controls the
SO_BROADCAST socket option, which allows broadcast datagrams
to be sent from this socket. Defaults to
false. I<< Optional. Type boolean.  >> 

=head2 PassCredentials

Takes a boolean value. This controls the
SO_PASSCRED socket option, which allows
AF_UNIX sockets to receive the
credentials of the sending process in an ancillary message.
Defaults to false. I<< Optional. Type boolean.  >> 

=head2 PassSecurity

Takes a boolean value. This controls the
SO_PASSSEC socket option, which allows
AF_UNIX sockets to receive the security
context of the sending process in an ancillary message.
Defaults to false. I<< Optional. Type boolean.  >> 

=head2 TCPCongestion

Takes a string value. Controls the TCP
congestion algorithm used by this socket. Should be one of
"westwood", "veno", "cubic", "lp" or any other available
algorithm supported by the IP stack. This setting applies only
to stream sockets. I<< Optional. Type uniline.  >> 

=head2 ExecStartPre

Takes one or more command lines, which are
executed before or after the listening sockets/FIFOs are
created and bound, respectively. The first token of the
command line must be an absolute filename, then followed by
arguments for the process. Multiple command lines may be
specified following the same scheme as used for
C<ExecStartPre> of service unit
files. I<< Optional. Type list of uniline.  >> 

=head2 ExecStartPost

Takes one or more command lines, which are
executed before or after the listening sockets/FIFOs are
created and bound, respectively. The first token of the
command line must be an absolute filename, then followed by
arguments for the process. Multiple command lines may be
specified following the same scheme as used for
C<ExecStartPre> of service unit
files. I<< Optional. Type list of uniline.  >> 

=head2 ExecStopPre

Additional commands that are executed before
or after the listening sockets/FIFOs are closed and removed,
respectively. Multiple command lines may be specified
following the same scheme as used for
C<ExecStartPre> of service unit
files. I<< Optional. Type list of uniline.  >> 

=head2 ExecStopPost

Additional commands that are executed before
or after the listening sockets/FIFOs are closed and removed,
respectively. Multiple command lines may be specified
following the same scheme as used for
C<ExecStartPre> of service unit
files. I<< Optional. Type list of uniline.  >> 

=head2 TimeoutSec

Configures the time to wait for the commands
specified in C<ExecStartPre>,
C<ExecStartPost>,
C<ExecStopPre> and
C<ExecStopPost> to finish. If a command does
not exit within the configured time, the socket will be
considered failed and be shut down again. All commands still
running will be terminated forcibly via
SIGTERM, and after another delay of this
time with SIGKILL. (See
C<KillMode> in
L<systemd.kill(5)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>systemd.kill&C<sektion>5&C<manpath>Debian+unstable+sid">.)
Takes a unit-less value in seconds, or a time span value such
as "5min 20s". Pass C<0> to disable the
timeout logic. Defaults to
C<DefaultTimeoutStartSec> from the manager
configuration file (see
L<systemd-system.conf(5)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>systemd-system.conf&C<sektion>5&C<manpath>Debian+unstable+sid">).
I<< Optional. Type uniline.  >> 

=head2 Service

Specifies the service unit name to activate on
incoming traffic. This setting is only allowed for sockets
with C<Accept>no. It defaults to the service
that bears the same name as the socket (with the suffix
replaced). In most cases, it should not be necessary to use
this option. Note that setting this parameter might result in
additional dependencies to be added to the unit (see
above). I<< Optional. Type uniline.  >> 

=head2 RemoveOnStop

Takes a boolean argument. If enabled, any file
nodes created by this socket unit are removed when it is
stopped. This applies to AF_UNIX sockets in the file system,
POSIX message queues, FIFOs, as well as any symlinks to them
configured with C<Symlinks>. Normally, it
should not be necessary to use this option, and is not
recommended as services might continue to run after the socket
unit has been terminated and it should still be possible to
communicate with them via their file system node. Defaults to
off. I<< Optional. Type boolean.  >> 

=head2 Symlinks

Takes a list of file system paths. The
specified paths will be created as symlinks to the AF_UNIX
socket path or FIFO path of this socket unit. If this setting
is used, only one AF_UNIX socket in the file system or one
FIFO may be configured for the socket unit. Use this option to
manage one or more symlinked alias names for a socket, binding
their lifecycle together. Defaults to the empty
list. I<< Optional. Type uniline.  >> 

=head2 FileDescriptorName

Assigns a name to all file descriptors this
socket unit encapsulates. This is useful to help activated
services identify specific file descriptors, if multiple fds
are passed. Services may use the
L<sd_listen_fds_with_names(3)|"https://manpages.debian.org/cgi-bin/man.cgi?C<query>sd_listen_fds_with_names&C<sektion>3&C<manpath>Debian+unstable+sid">
call to acquire the names configured for the received file
descriptors. Names may contain any ASCII character, but must
exclude control characters and C<:>, and must
be at most 255 characters in length. If this setting is not
used, the file descriptor name defaults to the name of the
socket unit, including its .socket
suffix. I<< Optional. Type uniline.  >> 

=head1 SEE ALSO

=over

=item *

L<cme>

=back

=head1 COPYRIGHT

=over

=item 2010-2016 Lennart Poettering and others

=item 2016 Dominique Dumont


=back

=head1 LICENSE

=over

=item LGPLv2.1+


=back

=cut

