mirror of https://github.com/mkerrisk/man-pages
place socket options in alpahbetical order
This commit is contained in:
Michael Kerrisk
parent
594a37e793
commit
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317
man7/socket.7
317
man7/socket.7
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@ -203,11 +203,102 @@ with the socket level set to
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.B SOL_SOCKET
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for all sockets:
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.\" FIXME Place following list in alphabetical order?
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.\"
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.\" SO_ACCEPTCONN is in SUSv3, and its origin is explained in
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.\" W R Stevens, UNPv1
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.TP
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.B SO_ACCEPTCONN
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Returns a value indicating whether or not this socket has been marked
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to accept connections with
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.BR listen ().
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The value 0 indicates that this is not a listening socket,
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the value 1 indicates that this is a listening socket.
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Can only be read
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with
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.BR getsockopt ().
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.TP
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.B SO_BSDCOMPAT
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Enable BSD bug-to-bug compatibility.
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This is used by the UDP protocol module in Linux 2.0 and 2.2.
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If enabled ICMP errors received for a UDP socket will not be passed
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to the user program.
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In later kernel versions, support for this option has been phased out:
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Linux 2.4 silently ignores it, and Linux 2.6 generates a kernel warning
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(printk()) if a program uses this option.
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Linux 2.0 also enabled BSD bug-to-bug compatibility
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options (random header changing, skipping of the broadcast flag) for raw
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sockets with this option, but that was removed in Linux 2.2.
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.TP
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.B SO_BINDTODEVICE
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Bind this socket to a particular device like \(lqeth0\(rq,
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as specified in the passed interface name. If the
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name is an empty string or the option length is zero, the socket device
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binding is removed. The passed option is a variable-length null terminated
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interface name string with the maximum size of
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.BR IFNAMSIZ .
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If a socket is bound to an interface,
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only packets received from that particular interface are processed by the
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socket. Note that this only works for some socket types, particularly
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.B AF_INET
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sockets. It is not supported for packet sockets (use normal
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.BR bind (8)
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there).
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.TP
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.B SO_BROADCAST
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Set or get the broadcast flag. When enabled, datagram sockets
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receive packets sent to a broadcast address and they are allowed to send
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packets to a broadcast address.
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This option has no effect on stream-oriented sockets.
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.TP
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.B SO_DEBUG
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Enable socket debugging. Only allowed for processes with the
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.B CAP_NET_ADMIN
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capability or an effective user ID of 0.
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.TP
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.B SO_ERROR
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Get and clear the pending socket error. Only valid as a
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.BR getsockopt ().
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Expects an integer.
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.TP
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.B SO_DONTROUTE
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Don't send via a gateway, only send to directly connected hosts.
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The same effect can be achieved by setting the
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.B MSG_DONTROUTE
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flag on a socket
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.BR send (2)
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operation. Expects an integer boolean flag.
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.TP
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.B SO_KEEPALIVE
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Enable sending of keep-alive messages on connection-oriented sockets.
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Expects an integer boolean flag.
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.TP
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.B SO_LINGER
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Sets or gets the
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.B SO_LINGER
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option. The argument is a
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.I linger
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structure.
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.sp
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.in +0.25i
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.nf
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struct linger {
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int l_onoff; /* linger active */
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int l_linger; /* how many seconds to linger for */
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};
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.fi
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.in -0.25i
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.IP
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When enabled, a
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.BR close (2)
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or
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.BR shutdown (2)
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will not return until all queued messages for the socket have been
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successfully sent or the linger timeout has been reached. Otherwise,
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the call returns immediately and the closing is done in the background.
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When the socket is closed as part of
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.BR exit (2),
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it always lingers in the background.
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.TP
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.B SO_OOBINLINE
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If this option is enabled,
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out-of-band data is directly placed into the receive data stream.
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@ -217,6 +308,46 @@ flag is set during receiving.
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.\" don't document it because it can do too much harm.
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.\".B SO_NO_CHECK
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.TP
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.B SO_PASSCRED
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Enable or disable the receiving of the
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.B SCM_CREDENTIALS
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control message. For more information see
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.BR unix (7).
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.TP
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.B SO_PEERCRED
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Return the credentials of the foreign process connected to this socket.
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This is only possible for connected
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.B PF_UNIX
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stream sockets and
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.B PF_UNIX
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stream and datagram socket pairs created using
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.BR socketpair (2);
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see
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.BR unix (7).
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The returned credentials are those that were in effect at the time
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of the call to
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.BR connect (2)
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or
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.BR socketpair (2).
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Argument is a
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.I ucred
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structure.
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Only valid as a
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.BR getsockopt ().
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.TP
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.B SO_PRIORITY
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Set the protocol-defined priority for all packets to be sent on
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this socket.
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Linux uses this value to order the networking queues:
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packets with a higher priority may be processed first depending
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on the selected device queueing discipline.
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For
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.BR ip (7),
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this also sets the IP type-of-service (TOS) field for outgoing packets.
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Setting a priority outside the range 0 to 6 requires the
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.B CAP_NET_ADMIN
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capability.
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.TP
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.BR SO_RCVLOWAT " and " SO_SNDLOWAT
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Specify the minimum number of bytes in the buffer until the socket layer
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will pass the data to the protocol
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@ -264,64 +395,29 @@ just as if the socket was specified to be nonblocking.
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If the timeout is set to zero (the default)
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then the operation will never timeout.
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.TP
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.B SO_BSDCOMPAT
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Enable BSD bug-to-bug compatibility.
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This is used by the UDP protocol module in Linux 2.0 and 2.2.
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If enabled ICMP errors received for a UDP socket will not be passed
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to the user program.
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In later kernel versions, support for this option has been phased out:
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Linux 2.4 silently ignores it, and Linux 2.6 generates a kernel warning
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(printk()) if a program uses this option.
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Linux 2.0 also enabled BSD bug-to-bug compatibility
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options (random header changing, skipping of the broadcast flag) for raw
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sockets with this option, but that was removed in Linux 2.2.
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.TP
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.B SO_PASSCRED
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Enable or disable the receiving of the
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.B SCM_CREDENTIALS
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control message. For more information see
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.BR unix (7).
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.TP
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.B SO_PEERCRED
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Return the credentials of the foreign process connected to this socket.
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This is only possible for connected
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.B PF_UNIX
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stream sockets and
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.B PF_UNIX
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stream and datagram socket pairs created using
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.BR socketpair (2);
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see
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.BR unix (7).
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The returned credentials are those that were in effect at the time
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of the call to
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.BR connect (2)
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or
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.BR socketpair (2).
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Argument is a
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.I ucred
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structure.
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Only valid as a
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.B SO_RCVBUF
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Sets or gets the maximum socket receive buffer in bytes.
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The kernel doubles this value (to allow space for bookkeeping overhead)
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when it is set using
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.\" Most (all?) other implementations do not do this -- MTK, Dec 05
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.BR setsockopt (),
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and this doubled value is returned by
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.BR getsockopt ().
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The default value is set by the
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.B rmem_default
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sysctl and the maximum allowed value is set by the
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.B rmem_max
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sysctl.
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The minimum (doubled) value for this option is 256.
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.TP
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.B SO_BINDTODEVICE
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Bind this socket to a particular device like \(lqeth0\(rq,
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as specified in the passed interface name. If the
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name is an empty string or the option length is zero, the socket device
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binding is removed. The passed option is a variable-length null terminated
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interface name string with the maximum size of
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.BR IFNAMSIZ .
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If a socket is bound to an interface,
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only packets received from that particular interface are processed by the
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socket. Note that this only works for some socket types, particularly
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.B AF_INET
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sockets. It is not supported for packet sockets (use normal
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.BR bind (8)
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there).
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.TP
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.B SO_DEBUG
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Enable socket debugging. Only allowed for processes with the
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.B CAP_NET_ADMIN
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capability or an effective user ID of 0.
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.BR SO_RCVBUFFORCE " (since Linux 2.6.14")
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Using this socket option, a privileged
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.RB ( CAP_NET_ADMIN )
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process can perform the same task as
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.BR SO_RCVBUF ,
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but the
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.B rmem_max
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limit can be overridden.
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.TP
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.B SO_REUSEADDR
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Indicates that the rules used in validating addresses supplied in a
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@ -336,39 +432,6 @@ When the listening socket is bound to
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with a specific port then it is not possible
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to bind to this port for any local address.
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.TP
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.B SO_TYPE
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Gets the socket type as an integer (like
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.BR SOCK_STREAM ).
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Can only be read
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with
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.BR getsockopt ().
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.\" SO_ACCEPTCONN is in SUSv3, and its origin is explained in
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.\" W R Stevens, UNPv1
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.TP
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.B SO_ACCEPTCONN
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Returns a value indicating whether or not this socket has been marked
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to accept connections with
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.BR listen ().
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The value 0 indicates that this is not a listening socket,
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the value 1 indicates that this is a listening socket.
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Can only be read
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with
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.BR getsockopt ().
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.TP
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.B SO_DONTROUTE
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Don't send via a gateway, only send to directly connected hosts.
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The same effect can be achieved by setting the
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.B MSG_DONTROUTE
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flag on a socket
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.BR send (2)
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operation. Expects an integer boolean flag.
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.TP
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.B SO_BROADCAST
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Set or get the broadcast flag. When enabled, datagram sockets
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receive packets sent to a broadcast address and they are allowed to send
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packets to a broadcast address.
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This option has no effect on stream-oriented sockets.
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.TP
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.B SO_SNDBUF
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Sets or gets the maximum socket send buffer in bytes.
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The kernel doubles this value (to allow space for bookkeeping overhead)
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@ -393,75 +456,6 @@ but the
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.B wmem_max
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limit can be overridden.
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.TP
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.B SO_RCVBUF
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Sets or gets the maximum socket receive buffer in bytes.
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The kernel doubles this value (to allow space for bookkeeping overhead)
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when it is set using
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.\" Most (all?) other implementations do not do this -- MTK, Dec 05
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.BR setsockopt (),
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and this doubled value is returned by
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.BR getsockopt ().
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The default value is set by the
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.B rmem_default
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sysctl and the maximum allowed value is set by the
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.B rmem_max
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sysctl.
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The minimum (doubled) value for this option is 256.
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.TP
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.BR SO_RCVBUFFORCE " (since Linux 2.6.14")
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Using this socket option, a privileged
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.RB ( CAP_NET_ADMIN )
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process can perform the same task as
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.BR SO_RCVBUF ,
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but the
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.B rmem_max
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limit can be overridden.
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.TP
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.B SO_LINGER
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Sets or gets the
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.B SO_LINGER
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option. The argument is a
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.I linger
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structure.
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.sp
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.in +0.25i
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.nf
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struct linger {
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int l_onoff; /* linger active */
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int l_linger; /* how many seconds to linger for */
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};
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.fi
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.in -0.25i
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.IP
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When enabled, a
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.BR close (2)
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or
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.BR shutdown (2)
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will not return until all queued messages for the socket have been
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successfully sent or the linger timeout has been reached. Otherwise,
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the call returns immediately and the closing is done in the background.
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When the socket is closed as part of
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.BR exit (2),
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it always lingers in the background.
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.TP
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.B SO_PRIORITY
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Set the protocol-defined priority for all packets to be sent on
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this socket.
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Linux uses this value to order the networking queues:
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packets with a higher priority may be processed first depending
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on the selected device queueing discipline.
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For
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.BR ip (7),
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this also sets the IP type-of-service (TOS) field for outgoing packets.
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Setting a priority outside the range 0 to 6 requires the
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.B CAP_NET_ADMIN
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capability.
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.TP
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.B SO_ERROR
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Get and clear the pending socket error. Only valid as a
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.BR getsockopt ().
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Expects an integer.
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.TP
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.B SO_TIMESTAMP
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Enable or disable the receiving of the
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.B SO_TIMESTAMP
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@ -476,6 +470,13 @@ reception time of the last packet passed to the user in this call.
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See
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.BR cmsg (3)
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for details on control messages.
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.TP
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.B SO_TYPE
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Gets the socket type as an integer (like
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.BR SOCK_STREAM ).
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Can only be read
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with
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.BR getsockopt ().
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.SH SIGNALS
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When writing onto a connection-oriented socket that has been shut down
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(by the local or the remote end)
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