.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH IP_PKTINFO 2const 2025-12-01 "Linux man-pages 6.17"
.SH NAME
IP_PKTINFO
\-
information about the incoming packet
.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_PKTINFO,
.BI "               const\~int\~*" enable ,\~sizeof(int));
.fi
.SH DESCRIPTION
Pass an
.B IP_PKTINFO
ancillary message that contains a
.BR in_pktinfo (2type)
structure that supplies some information about the incoming packet.
This works only for datagram oriented sockets.
.P
The argument is a flag that tells the socket whether the
.B IP_PKTINFO
message should be passed or not.
.P
The message itself can be sent/retrieved
only as a control message with a packet using
.BR recvmsg (2)
or
.BR sendmsg (2).
.P
Not supported for
.B SOCK_STREAM
sockets.
.SH ERRORS
See
.BR IPPROTO_IP (2const).
See
.BR setsockopt (2).
See
.BR ip (7).
.SH VERSIONS
Some BSD sockets implementations provide
.B IP_RCVDSTADDR
and
.B IP_RECVIF
socket options to get the destination address and the interface of
received datagrams.
Linux has the more general
.B IP_PKTINFO
for the same task.
.SH STANDARDS
Linux.
.SH HISTORY
Linux 2.2.
.\" Precisely: since Linux 2.1.68
.SH SEE ALSO
.BR in_pktinfo (2const),
.BR IPPROTO_IP (2const),
.BR setsockopt (2),
.BR ip (7)