.\" Copyright, the authors of the Linux man-pages project
.\"
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.TH IPPROTO_IP 2const 2025-11-25 "Linux man-pages 6.17"
.SH NAME
IPPROTO_IP
\-
include a user-supplied IP header
.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_HDRINCL,
.BI "               const\~int\~*" enable ,\~sizeof(int));
.fi
.SH DESCRIPTION
If enabled,
the user supplies an IP header in front of the user data.
.P
Valid only for
.B SOCK_RAW
sockets;
see
.BR raw (7)
for more information.
.P
When this flag is enabled,
the values set by
.BR IP_OPTIONS (2const),
.BR IP_TTL (2const),
and
.BR IP_TOS (2const)
are ignored.
.SH ERRORS
See
.BR IPPROTO_IP (2const).
See
.BR setsockopt (2).
See
.BR ip (7).
.SH HISTORY
Linux 2.0.
.SH SEE ALSO
.BR IPPROTO_IP (2const),
.BR setsockopt (2),
.BR ip (7)