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.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH IP_TOS 2const (date) "Linux man-pages (unreleased)"
.SH NAME
IP_TOS
\-
type of service
.SH LIBRARY
Standard C library
.RI ( libc ,\~ \-lc )
.SH SYNOPSIS
.nf
.BR "#include <netinet/in.h>" " /* Definition of " IP* " constants */"
.B #include <sys/socket.h>
.P
.BI int\~setsockopt(int\~ sockfd ,\~IPPROTO_IP,\~IP_TOS,
.BI " const\~int\~*" tos ,\~sizeof(int));
.BI int\~getsockopt(int\~ sockfd ,\~IPPROTO_IP,\~IP_TOS,
.BI " int\~*" tos ,\~sizeof(int));
.fi
.SH DESCRIPTION
Set or receive the Type-Of-Service (TOS) field that is sent
with every IP packet originating from this socket.
It is used to prioritize packets on the network.
.P
There are some standard TOS flags defined:
.TP
.B IPTOS_LOWDELAY
to minimize delays for interactive traffic,
.TP
.B IPTOS_THROUGHPUT
to optimize throughput,
.TP
.B IPTOS_RELIABILITY
to optimize for reliability,
.TP
.B IPTOS_MINCOST
should be used for "filler data" where slow transmission doesn't matter.
.P
At most one of these TOS values can be specified.
Other bits are invalid and shall be cleared.
.P
Linux sends
.B IPTOS_LOWDELAY
datagrams first by default,
but the exact behavior depends on the configured queueing discipline.
.\" FIXME elaborate on this
.P
Some high-priority levels may require superuser privileges (the
.B CAP_NET_ADMIN
capability).
.\" The priority can also be set in a protocol-independent way by the
.\" .RB ( SOL_SOCKET ", " SO_PRIORITY )
.\" socket option (see
.\" .BR socket (7)).
.SH ERRORS
See
.BR IPPROTO_IP (2const).
See
.BR setsockopt (2).
See
.BR ip (7).
.SH HISTORY
Linux 1.0.
.SH SEE ALSO
.BR IPPROTO_IP (2const),
.BR setsockopt (2),
.BR ip (7)
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