man*/: srcfix (Use .P instead of .PP or .LP)

[thirdparty/man-pages.git] / man7 / rtnetlink.7

'\" t
.\" SPDX-License-Identifier: Linux-man-pages-1-para
.\"
.\" This man page is Copyright (C) 1999 Andi Kleen <ak@muc.de>.
.\"
.\" Based on the original comments from Alexey Kuznetsov, written with
.\" help from Matthew Wilcox.
.\" $Id: rtnetlink.7,v 1.8 2000/01/22 01:55:04 freitag Exp $
.\"
.TH rtnetlink 7 (date) "Linux man-pages (unreleased)"
.SH NAME
rtnetlink \- Linux routing socket
.SH SYNOPSIS
.nf
.B #include <asm/types.h>
.B #include <linux/netlink.h>
.B #include <linux/rtnetlink.h>
.B #include <sys/socket.h>
.P
.BI "rtnetlink_socket = socket(AF_NETLINK, int " socket_type ", NETLINK_ROUTE);"
.fi
.SH DESCRIPTION
Rtnetlink allows the kernel's routing tables to be read and altered.
It is used within the kernel to communicate between
various subsystems, though this usage is not documented here, and for
communication with user-space programs.
Network routes, IP addresses, link parameters, neighbor setups, queueing
disciplines, traffic classes and packet classifiers may all be controlled
through
.B NETLINK_ROUTE
sockets.
It is based on netlink messages; see
.BR netlink (7)
for more information.
.\" FIXME . ? all these macros could be moved to rtnetlink(3)
.SS Routing attributes
Some rtnetlink messages have optional attributes after the initial header:
.P
.in +4n
.EX
struct rtattr {
    unsigned short rta_len;    /* Length of option */
    unsigned short rta_type;   /* Type of option */
    /* Data follows */
};
.EE
.in
.P
These attributes should be manipulated using only the RTA_* macros
or libnetlink, see
.BR rtnetlink (3).
.SS Messages
Rtnetlink consists of these message types
(in addition to standard netlink messages):
.TP
.B RTM_NEWLINK
.TQ
.B RTM_DELLINK
.TQ
.B RTM_GETLINK
Create, remove, or get information about a specific network interface.
These messages contain an
.I ifinfomsg
structure followed by a series of
.I rtattr
structures.
.IP
.EX
struct ifinfomsg {
    unsigned char  ifi_family; /* AF_UNSPEC */
    unsigned short ifi_type;   /* Device type */
    int            ifi_index;  /* Interface index */
    unsigned int   ifi_flags;  /* Device flags  */
    unsigned int   ifi_change; /* change mask */
};
.EE
.IP
.\" FIXME Document ifinfomsg.ifi_type
.I ifi_flags
contains the device flags, see
.BR netdevice (7);
.I ifi_index
is the unique interface index
(since Linux 3.7, it is possible to feed a nonzero value with the
.B RTM_NEWLINK
message, thus creating a link with the given
.IR ifindex );
.I ifi_change
is reserved for future use and should be always set to 0xFFFFFFFF.
.TS
tab(:);
c s s
lb l l.
Routing attributes
rta_type:Value type:Description
_
IFLA_UNSPEC:-:unspecified
IFLA_ADDRESS:hardware address:interface L2 address
IFLA_BROADCAST:hardware address:L2 broadcast address
IFLA_IFNAME:asciiz string:Device name
IFLA_MTU:unsigned int:MTU of the device
IFLA_LINK:int:Link type
IFLA_QDISC:asciiz string:Queueing discipline
IFLA_STATS:T{
see below
T}:Interface Statistics
IFLA_PERM_ADDRESS:hardware address:T{
hardware address provided by device (since Linux 5.5)
T}
.TE
.IP
The value type for
.B IFLA_STATS
is
.I struct rtnl_link_stats
.RI ( "struct net_device_stats"
in Linux 2.4 and earlier).
.TP
.B RTM_NEWADDR
.TQ
.B RTM_DELADDR
.TQ
.B RTM_GETADDR
Add, remove, or receive information about an IP address associated with
an interface.
In Linux 2.2, an interface can carry multiple IP addresses,
this replaces the alias device concept in Linux 2.0.
In Linux 2.2, these messages
support IPv4 and IPv6 addresses.
They contain an
.I ifaddrmsg
structure, optionally followed by
.I rtattr
routing attributes.
.IP
.EX
struct ifaddrmsg {
    unsigned char ifa_family;    /* Address type */
    unsigned char ifa_prefixlen; /* Prefixlength of address */
    unsigned char ifa_flags;     /* Address flags */
    unsigned char ifa_scope;     /* Address scope */
    unsigned int  ifa_index;     /* Interface index */
};
.EE
.IP
.I ifa_family
is the address family type (currently
.B AF_INET
or
.BR AF_INET6 ),
.I ifa_prefixlen
is the length of the address mask of the address if defined for the
family (like for IPv4),
.I ifa_scope
is the address scope,
.I ifa_index
is the interface index of the interface the address is associated with.
.I ifa_flags
is a flag word of
.B IFA_F_SECONDARY
for secondary address (old alias interface),
.B IFA_F_PERMANENT
for a permanent address set by the user and other undocumented flags.
.TS
tab(:);
c s s
lb l l.
Attributes
rta_type:Value type:Description
_
IFA_UNSPEC:-:unspecified
IFA_ADDRESS:raw protocol address:interface address
IFA_LOCAL:raw protocol address:local address
IFA_LABEL:asciiz string:name of the interface
IFA_BROADCAST:raw protocol address:broadcast address
IFA_ANYCAST:raw protocol address:anycast address
IFA_CACHEINFO:struct ifa_cacheinfo:Address information
.TE
.\" FIXME Document struct ifa_cacheinfo
.TP
.B RTM_NEWROUTE
.TQ
.B RTM_DELROUTE
.TQ
.B RTM_GETROUTE
Create, remove, or receive information about a network route.
These messages contain an
.I rtmsg
structure with an optional sequence of
.I rtattr
structures following.
For
.BR RTM_GETROUTE ,
setting
.I rtm_dst_len
and
.I rtm_src_len
to 0 means you get all entries for the specified routing table.
For the other fields, except
.I rtm_table
and
.IR rtm_protocol ,
0 is the wildcard.
.IP
.EX
struct rtmsg {
    unsigned char rtm_family;   /* Address family of route */