Section (3) rtnetlink
Name
rtnetlink — macros to manipulate rtnetlink messages
Synopsis
#include <asm/types.h> #include <linux/netlink.h> #include <linux/rtnetlink.h> #include <sys/socket.h>
rtnetlink_socket =
socket( |
AF_NETLINK, |
int socket_type, | |
NETLINK_ROUTE) ; |
int
RTA_OK( |
struct rtattr *rta, |
int rtabuflen) ; |
void
*RTA_DATA( |
struct rtattr *rta) ; |
unsigned int
RTA_PAYLOAD( |
struct rtattr *rta) ; |
struct rtattr
*RTA_NEXT( |
struct rtattr *rta, |
unsigned int rtabuflen) ; |
unsigned int
RTA_LENGTH( |
unsigned int length) ; |
unsigned int
RTA_SPACE( |
unsigned int length) ; |
DESCRIPTION
All rtnetlink(7) messages consist of a netlink(7) message header and appended attributes. The attributes should be manipulated only using the macros provided here.
RTA_OK
(rta
, attrlen
) returns true if
rta
points to a valid
routing attribute; attrlen
is the running length
of the attribute buffer. When not true then you must assume
there are no more attributes in the message, even if
attrlen
is
nonzero.
RTA_DATA
(rta
) returns a pointer to the
start of this attribute_zsingle_quotesz_s data.
RTA_PAYLOAD
(rta
) returns the length of this
attribute_zsingle_quotesz_s data.
RTA_NEXT
(rta
, attrlen
) gets the next
attribute after rta
.
Calling this macro will update attrlen
. You should use
RTA_OK
to check the validity of
the returned pointer.
RTA_LENGTH
(len
) returns the length which
is required for len
bytes of data plus the header.
RTA_SPACE
(len
) returns the amount of
space which will be needed in a message with len
bytes of data.
EXAMPLE
Creating a rtnetlink message to set the MTU of a device:
#include <linux/rtnetlink.h> ... struct { struct nlmsghdr nh; struct ifinfomsg if; char attrbuf[512]; } req; struct rtattr *rta; unsigned int mtu = 1000; int rtnetlink_sk = socket(AF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE); memset(&req, 0, sizeof(req)); req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg)); req.nh.nlmsg_flags = NLM_F_REQUEST; req.nh.nlmsg_type = RTM_NEWLINK; req.if.ifi_family = AF_UNSPEC; req.if.ifi_index = INTERFACE_INDEX; req.if.ifi_change = 0xffffffff; /* ??? */ rta = (struct rtattr *)(((char *) &req) + NLMSG_ALIGN(req.nh.nlmsg_len)); rta−>rta_type = IFLA_MTU; rta−>rta_len = RTA_LENGTH(sizeof(unsigned int)); req.nh.nlmsg_len = NLMSG_ALIGN(req.nh.nlmsg_len) + RTA_LENGTH(sizeof(mtu)); memcpy(RTA_DATA(rta), &mtu, sizeof(mtu)); send(rtnetlink_sk, &req, req.nh.nlmsg_len, 0);
COLOPHON
This page is part of release 4.16 of the Linux man-pages
project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
This man page is Copyright (C) 1999 Andi Kleen <akmuc.de>. %%%LICENSE_START(VERBATIM_ONE_PARA) Permission is granted to distribute possibly modified copies of this page provided the header is included verbatim, and in case of nontrivial modification author and date of the modification is added to the header. %%%LICENSE_END $Id: rtnetlink.3,v 1.2 1999/05/18 10:35:10 freitag Exp $ |
Section (7) rtnetlink
Name
rtnetlink — Linux IPv4 routing socket
Synopsis
#include <asm/types.h> #include <linux/netlink.h> #include <linux/rtnetlink.h> #include <sys/socket.h>
rtnetlink_socket =
socket( |
AF_NETLINK, |
int socket_type, | |
NETLINK_ROUTE) ; |
DESCRIPTION
Rtnetlink allows the kernel_zsingle_quotesz_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 NETLINK_ROUTE
sockets. It is
based on netlink messages; see netlink(7) for more
information.
Routing attributes
Some rtnetlink messages have optional attributes after the initial header:
struct rtattr { unsigned short rta_len
; /* Length of option */unsigned short rta_type
; /* Type of option */ /* Data follows */};
These attributes should be manipulated using only the RTA_* macros or libnetlink, see rtnetlink(3).
Messages
Rtnetlink consists of these message types (in addition to standard netlink messages):
RTM_NEWLINK
,RTM_DELLINK
,RTM_GETLINK
-
Create, remove or get information about a specific network interface. These messages contain an
ifinfomsg
structure followed by a series ofrtattr
structures.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 */}; ifi_flags
contains the device flags, see netdevice(7);ifi_index
is the unique interface index (since Linux 3.7, it is possible to feed a nonzero value with theRTM_NEWLINK
message, thus creating a link with the givenifindex
);ifi_change
is reserved for future use and should be always set to 0xFFFFFFFF.
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 | see below | Interface Statistics. |
The value type for IFLA_STATS
is struct rtnl_link_stats
(struct
net_device_stats in Linux 2.4 and earlier).
RTM_NEWADDR
,RTM_DELADDR
,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 2.0. In Linux 2.2, these messages support IPv4 and IPv6 addresses. They contain an
ifaddrmsg
structure, optionally followed byrtattr
routing attributes.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 */int ifa_index
;/* Interface index */}; ifa_family
is the address family type (currentlyAF_INET
orAF_INET6
),ifa_prefixlen
is the length of the address mask of the address if defined for the family (like for IPv4),ifa_scope
is the address scope,ifa_index
is the interface index of the interface the address is associated with.ifa_flags
is a flag word ofIFA_F_SECONDARY
for secondary address (old alias interface),IFA_F_PERMANENT
for a permanent address set by the user and other undocumented flags.
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. |
RTM_NEWROUTE
,RTM_DELROUTE
,RTM_GETROUTE
-
Create, remove or receive information about a network route. These messages contain an
rtmsg
structure with an optional sequence ofrtattr
structures following. ForRTM_GETROUTE
, settingrtm_dst_len
andrtm_src_len
to 0 means you get all entries for the specified routing table. For the other fields, exceptrtm_table
andrtm_protocol
, 0 is the wildcard.struct rtmsg { unsigned char rtm_family
;/* Address family of route */unsigned char rtm_dst_len
;/* Length of destination */unsigned char rtm_src_len
;/* Length of source */unsigned char rtm_tos
;/* TOS filter */unsigned char rtm_table
;/* Routing table ID */unsigned char rtm_protocol
;/* Routing protocol; see below */unsigned char rtm_scope
;/* See below */unsigned char rtm_type
;/* See below */unsigned int rtm_flags
;};
rtm_type | Route type |
RTN_UNSPEC | unknown route |
RTN_UNICAST | a gateway or direct route |
RTN_LOCAL | a local interface route |
RTN_BROADCAST | a local broadcast route (sent as a broadcast) |
RTN_ANYCAST | a local broadcast route (sent as a unicast) |
RTN_MULTICAST | a multicast route |
RTN_BLACKHOLE | a packet dropping route |
RTN_UNREACHABLE | an unreachable destination |
RTN_PROHIBIT | a packet rejection route |
RTN_THROW | continue routing lookup in another table |
RTN_NAT | a network address translation rule |
RTN_XRESOLVE | refer to an external resolver (not implemented) |
rtm_protocol | Route origin. |
RTPROT_UNSPEC | unknown |
RTPROT_REDIRECT | by an ICMP redirect (currently unused) |
RTPROT_KERNEL | by the kernel |
RTPROT_BOOT | during boot |
RTPROT_STATIC | by the administrator |
Values larger than RTPROT_STATIC
are not interpreted by the
kernel, they are just for user information. They may be
used to tag the source of a routing information or to
distinguish between multiple routing daemons. See
<
linux/rtnetlink.h
>
for the routing daemon identifiers
which are already assigned.
-
rtm_scope
is the distance to the destination:
RT_SCOPE_UNIVERSE | global route |
RT_SCOPE_SITE | interior route in the local autonomous system |
RT_SCOPE_LINK | route on this link |
RT_SCOPE_HOST | route on the local host |
RT_SCOPE_NOWHERE | destination doesn_zsingle_quotesz_t exist |
The values between RT_SCOPE_UNIVERSE
and RT_SCOPE_SITE
are available to the
user.
-
The
rtm_flags
have the following meanings:
RTM_F_NOTIFY | if the route changes, notify the user via rtnetlink |
RTM_F_CLONED | route is cloned from another route |
RTM_F_EQUALIZE | a multipath equalizer (not yet implemented) |
rtm_table
specifies the routing table
RT_TABLE_UNSPEC | an unspecified routing table |
RT_TABLE_DEFAULT | the default table |
RT_TABLE_MAIN | the main table |
RT_TABLE_LOCAL | the local table |
The user may assign arbitrary values between
RT_TABLE_UNSPEC
and
RT_TABLE_DEFAULT
.
Attributes | ||
rta_type | value type | description |
RTA_UNSPEC | - | ignored. |
RTA_DST | protocol address | Route destination address. |
RTA_SRC | protocol address | Route source address. |
RTA_IIF | int | Input interface index. |
RTA_OIF | int | Output interface index. |
RTA_GATEWAY | protocol address | The gateway of the route |
RTA_PRIORITY | int | Priority of route. |
RTA_PREFSRC | ||
RTA_METRICS | int | Route metric |
RTA_MULTIPATH | ||
RTA_PROTOINFO | ||
RTA_FLOW | ||
RTA_CACHEINFO |
Fill these values in!
RTM_NEWNEIGH
,RTM_DELNEIGH
,RTM_GETNEIGH
-
Add, remove or receive information about a neighbor table entry (e.g., an ARP entry). The message contains an
ndmsg
structure.struct ndmsg { unsigned char ndm_family
;int ndm_ifindex
;/* Interface index */__u16 ndm_state
;/* State */__u8 ndm_flags
;/* Flags */__u8 ndm_type
;}; struct nda_cacheinfo { __u32 ndm_confirmed
;__u32 ndm_used
;__u32 ndm_updated
;__u32 ndm_refcnt
;}; ndm_state
is a bit mask of the following states:
NUD_INCOMPLETE | a currently resolving cache entry |
NUD_REACHABLE | a confirmed working cache entry |
NUD_STALE | an expired cache entry |
NUD_DELAY | an entry waiting for a timer |
NUD_PROBE | a cache entry that is currently reprobed |
NUD_FAILED | an invalid cache entry |
NUD_NOARP | a device with no destination cache |
NUD_PERMANENT | a static entry |
Valid ndm_flags
are:
NTF_PROXY | a proxy arp entry |
NTF_ROUTER | an IPv6 router |
The rtattr
struct has the following meanings for the rta_type
field:
NDA_UNSPEC | unknown type |
NDA_DST | a neighbor cache n/w layer destination address |
NDA_LLADDR | a neighbor cache link layer address |
NDA_CACHEINFO | cache statistics. |
If the rta_type
field is NDA_CACHEINFO
, then
a struct
nda_cacheinfo header follows
RTM_NEWRULE
,RTM_DELRULE
,RTM_GETRULE
-
Add, delete or retrieve a routing rule. Carries a struct rtmsg
RTM_NEWQDISC
,RTM_DELQDISC
,RTM_GETQDISC
-
Add, remove or get a queueing discipline. The message contains a struct tcmsg and may be followed by a series of attributes.
struct tcmsg { unsigned char tcm_family
;int tcm_ifindex
;/* interface index */__u32 tcm_handle
;/* Qdisc handle */__u32 tcm_parent
;/* Parent qdisc */__u32 tcm_info
;};
Attributes | ||
rta_type | value type | Description |
TCA_UNSPEC | - | unspecified |
TCA_KIND | asciiz string | Name of queueing discipline |
TCA_OPTIONS | byte sequence | Qdisc-specific options follow |
TCA_STATS | struct tc_stats | Qdisc statistics. |
TCA_XSTATS | qdisc-specific | Module-specific statistics. |
TCA_RATE | struct tc_estimator | Rate limit. |
In addition, various other qdisc-module-specific attributes are allowed. For more information see the appropriate include files.
RTM_NEWTCLASS
,RTM_DELTCLASS
,RTM_GETTCLASS
-
Add, remove or get a traffic class. These messages contain a struct tcmsg as described above.
RTM_NEWTFILTER
,RTM_DELTFILTER
,RTM_GETTFILTER
-
Add, remove or receive information about a traffic filter. These messages contain a struct tcmsg as described above.
COLOPHON
This page is part of release 4.16 of the Linux man-pages
project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
t This man page is Copyright (C) 1999 Andi Kleen <akmuc.de>. %%%LICENSE_START(VERBATIM_ONE_PARA) Permission is granted to distribute possibly modified copies of this page provided the header is included verbatim, and in case of nontrivial modification author and date of the modification is added to the header. %%%LICENSE_END 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 $ |