.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.\" FIXME The following socket options are yet to be documented
.\"
.\"	IP_XFRM_POLICY (2.5.48)
.\"	    Needs CAP_NET_ADMIN
.\"
.\"	IP_IPSEC_POLICY (2.5.47)
.\"	    Needs CAP_NET_ADMIN
.\"
.\"	IP_MINTTL (2.6.34)
.\"	    commit d218d11133d888f9745802146a50255a4781d37a
.\"	    Author: Stephen Hemminger <shemminger@vyatta.com>
.\"
.\"	MCAST_JOIN_GROUP (2.4.22 / 2.6)
.\"
.\"	MCAST_BLOCK_SOURCE (2.4.22 / 2.6)
.\"
.\"	MCAST_UNBLOCK_SOURCE (2.4.22 / 2.6)
.\"
.\"	MCAST_LEAVE_GROUP (2.4.22 / 2.6)
.\"
.\"	MCAST_JOIN_SOURCE_GROUP (2.4.22 / 2.6)
.\"
.\"	MCAST_LEAVE_SOURCE_GROUP (2.4.22 / 2.6)
.\"
.\"	MCAST_MSFILTER (2.4.22 / 2.6)
.\"
.\"	IP_UNICAST_IF (3.4)
.\"	    commit 76e21053b5bf33a07c76f99d27a74238310e3c71
.\"	    Author: Erich E. Hoover <ehoover@mines.edu>
.\"
.TH IPPROTO_IP 2const 2026-01-05 "Linux man-pages 6.17"
.SH NAME
IPPROTO_IP
\-
Linux IPv4 protocol socket options
.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,\~int\~ opt ,
.BI "               const\~void\~" val [ size ],\~size_t\~ size );
.BI int\~getsockopt(int\~ sockfd ,\~IPPROTO_IP,\~int\~ opt ,
.BI "               void\~" val [ size ],\~size_t\~ size );
.fi
.SH DESCRIPTION
IP supports some protocol-specific socket options that can be set with
.BR setsockopt (2)
and read with
.BR getsockopt (2).
The socket option level for IP is
.BR IPPROTO_IP .
.\" or SOL_IP on Linux
.P
The following socket options are supported.
.TP
.BR IP_ADD_MEMBERSHIP (2const)
.TQ
.BR IP_ADD_SOURCE_MEMBERSHIP (2const)
.TQ
.BR IP_BIND_ADDRESS_NO_PORT (2const)
.TQ
.BR IP_BLOCK_SOURCE (2const)
.TQ
.BR IP_DROP_MEMBERSHIP (2const)
.TQ
.BR IP_DROP_SOURCE_MEMBERSHIP (2const)
.TQ
.BR IP_FREEBIND (2const)
.TQ
.BR IP_HDRINCL (2const)
.TQ
.BR IP_LOCAL_PORT_RANGE (2const)
.TQ
.BR IP_MSFILTER (2const)
.TQ
.BR IP_MTU (2const)
.TQ
.BR IP_MTU_DISCOVER (2const)
.TQ
.BR IP_MULTICAST_ALL (2const)
.TQ
.BR IP_MULTICAST_IF (2const)
.TQ
.BR IP_MULTICAST_LOOP (2const)
.TQ
.BR IP_MULTICAST_TTL (2const)
.TQ
.BR IP_NODEFRAG (2const)
.TQ
.BR IP_OPTIONS (2const)
.TQ
.BR IP_PASSSEC (2const)
.TQ
.BR IP_PKTINFO (2const)
.TQ
.BR IP_RECVERR (2const)
.TQ
.BR IP_RECVOPTS (2const)
.TQ
.BR IP_RECVORIGDSTADDR (2const)
.TQ
.BR IP_RECVTOS (2const)
.TQ
.BR IP_RECVTTL (2const)
.TQ
.BR IP_RETOPTS (2const)
.TQ
.BR IP_ROUTER_ALERT (2const)
.TQ
.BR IP_TOS (2const)
.TQ
.BR IP_TRANSPARENT (2const)
.TQ
.BR IP_TTL (2const)
.TQ
.BR IP_UNBLOCK_SOURCE (2const)
.SH ERRORS
See
.BR setsockopt (2).
See
.BR ip (7).
.TP
.B ENOPROTOOPT
.I opt
is invalid.
.\" .SH STANDARDS
.\" IP_XFRM_POLICY is Linux-specific
.\" IP_IPSEC_POLICY is a nonstandard extension, also present on some BSDs
.SH HISTORY
.TP
.B IPPROTO_IP
POSIX.1-2001.
.SH SEE ALSO
.BR setsockopt (2),
.BR ip (7)