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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | ERRORS | HISTORY | SEE ALSO | COLOPHON |
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IP_OPTIONS(2const) IP_OPTIONS(2const)
IP_OPTIONS - options to be sent with every packet
Standard C library (libc, -lc)
#include <netinet/in.h> /* Definition of IP* constants */
#include <sys/socket.h>
int setsockopt(int sockfd, IPPROTO_IP, IP_OPTIONS,
const void buf[size], size_t size);
int getsockopt(int sockfd, IPPROTO_IP, IP_OPTIONS,
void buf[size], size_t size);
Set or get the IP options to be sent with every packet from this
socket.
The arguments are a pointer to a memory buffer containing the
options and the buffer length.
The setsockopt(2) call sets the IP options associated with a
socket. The maximum option size for IPv4 is 40 bytes. See
RFC 791 for the allowed options.
When the initial connection request packet for a SOCK_STREAM
socket contains IP options, the IP options will be set
automatically to the options from the initial packet with routing
headers reversed.
Incoming packets are not allowed to change options after the
connection is established.
The processing of all incoming source routing options is disabled
by default and can be enabled by using the accept_source_route
/proc interface. Other options like timestamps are still handled.
For datagram sockets, IP options can be set only by the local
user.
Calling getsockopt(2) with IP_OPTIONS puts the current IP options
used for sending into the supplied buffer.
See IPPROTO_IP(2const). See setsockopt(2). See ip(7).
Linux 2.0.
IPPROTO_IP(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 2025-11-25 IP_OPTIONS(2const)
Pages that refer to this page: IP_HDRINCL(2const), IPPROTO_IP(2const), IP_RECVERR(2const), IP_RECVOPTS(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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