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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | STANDARDS | HISTORY | SEE ALSO | COLOPHON |
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in_pktinfo(2type) in_pktinfo(2type)
in_pktinfo - information about the incoming packet
Standard C library (libc, -lc)
#include <netinet/in.h>
struct in_pktinfo {
unsigned int ipi_ifindex; /* Interface index */
struct in_addr ipi_spec_dst; /* Local address */
struct in_addr ipi_addr; /* Header Destination address */
};
recvmsg(2)
When returned by recvmsg(2), .ipi_ifindex is the unique index of
the interface the packet was received on.
.ipi_spec_dst is the preferred source address for replies to the
given packet.
.ipi_addr is the destination address in the packet header.
These addresses are usually the same, but can differ for broadcast
or multicast packets. Depending on the configured routes,
.ipi_spec_dst might belong to a different interface from the one
that received the packet.
sendmsg(2)
If IP_PKTINFO is passed to sendmsg(2) and .ipi_spec_dst is not
zero, then it is used as the local source address, for the routing
table lookup, and for setting up IP source route options.
When .ipi_ifindex is not zero, the primary local address of the
interface specified by the index overwrites .ipi_spec_dst for the
routing table lookup.
.ipi_addr is ignored.
Linux.
Linux 2.2.
IP_PKTINFO(2const), setsockopt(2), ip(7)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
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Linux man-pages 6.18 2025-11-26 in_pktinfo(2type)
Pages that refer to this page: IP_PKTINFO(2const)
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HTML rendering created 2026-05-24 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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