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[Linux manuál]

rtnetlink, NETLINK_ROUTE: Linuxová IPv4 směrovací patice

Originální popis anglicky: rtnetlink, NETLINK_ROUTE - Linux IPv4 routing socket

Návod, kniha: Linux Programmer's Manual

STRUČNĚ

#include <asm/types.h>
 
#include <linux/netlink.h>
 
#include <linux/rtnetlink.h>
 
#include <sys/socket.h>
 
rtnetlink_socket = socket(PF_NETLINK, int socket_type, NETLINK_ROUTE);
 

POPIS / INSTRUKCE

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, neighbour 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 only manipulated using 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 of rtattr 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, 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 struct net_device_stats Interface Statistics.
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 by rtaddr routing attributes.
 
struct ifaddrmsg
{
	unsigned char	ifa_family;	/* Address type */
	unsigned char	ifa_prefixlen;	/* Prefixlength of the 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 (currently AF_INET or AF_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 of IFA_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 of rtattr structures following. For RTM_GETROUTE setting rtm_dst_len and rtm_src_len to 0 means you get all entries for the specified routing table. For the other fields except rtm_table and rtm_protocol 0 is the wildcard.
 
struct rtmsg
{
	unsigned char	rtm_family;	/* Address family of route */
	unsigned char	rtm_dst_len;	/* Length of source */
	unsigned char	rtm_src_len;	/* Length of destination */ 
	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 distingush 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'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 multicast 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 arbitary 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 neighbour 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 bitmask 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
 
document the members of the struct better
 
The rtaddr struct has the following meanings for the rta_type field:
 
NDA_UNSPEC unknown type
NDA_DST a neighbour cache network layer destination address
NDA_LLADDR a neighbour 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.

VERSIONS

rtnetlink is a new feature of Linux 2.2.

BUGS

This manual page is lacking and incomplete.
 

SOUVISEJÍCÍ

cmsg(3), rtnetlink(3), ip(7), netlink(7)
1999-04-30 Linux Man Page
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