route.7p (2010 09)

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route(7P) route(7P)

NAME

route - kernel packet forwarding database

SYNOPSIS

#include <sys/types.h>

#include <sys/socket.h>

#include <net/route.h>

#include <net/if.h>

s = socket(AF_ROUTE, SOCK_RAW,

family );

DESCRIPTION

This manpage describes routing socket interface to read and write kernel routing messages.

The information on how to transmit network packets is maintained by the HP-UX kernel in the routing

information database, also known as the routing table. A user process can read or update information in

the routing table by sending routing messages to the kernel via an AF_ROUTE socket. The message

types are described in more detail in the Message Types section below.

The family parameter in the

socket system call shown in the SYNOPSIS may be used to ﬁlter the rout-

ing messages the caller receives. The valid values for family are:

AF_INET get routing messages affecting the Internet Protocol.

AF_INET6 get routing messages affecting the Internet Protocol version 6.

AF_UNSPEC get routing messages affecting both AF_INET and AF_INET6 protocols.

Entries in the routing table specify the appropriate remote host or gateway to use when transmitting

packets. These entries are either host-speciﬁc, or are applicable to all hosts located on a generic subnet-

work, as speciﬁed by a netmask value.

After the system boots, each protocol family adds entries to the routing table for each network interface

conﬁgured and ready to transmit network trafﬁc. Normally, the route entry is speciﬁed as a direct con-

nection to the destination host or network. For direct routes, the transport layer of the network stack

sends packets directly to the host speciﬁed in the packet header. For non-direct routes, the interface for-

wards the packet to the gateway listed in the routing entry for that interface.

When routing packets, the kernel attempts to ﬁnd an optimal route for each destination. If more than

one entry matches the netmask of the destination, the kernel selects the route with the greater number of

1’s in the netmask.

A default (wildcard) route is used if no other route to a particular remote host or network can be located.

A default route is speciﬁed with an all 0 destination address value and a netmask of all 0’s. Default

routes, in combination with routing redirects, provide an economical mechanism for routing network

trafﬁc.

If no routing entry is found, the destination is declared as unreachable, and a routing-miss message

(RTM_MISS) is generated to any user processes using the routing socket facilities, as described below.

Message Types

After creating a routing socket, the process can send commands to the kernel by writing to the socket.

The process can read information from the kernel by reading from the socket. The following message

types can be used to communicate routing information between the user process and the kernel:

RTM_ADD add route

RTM_CHANGE change gateway, metrics or ﬂags

RTM_DELADDR address being removed from interface

RTM_DELETE delete route

RTM_GET report metrics and other information

RTM_IFINFO interface going up, down, etc.

RTM_LOSING kernel suspects route is failing

RTM_LOCK lock speciﬁed metrics

RTM_MISS lookup on this address failed

RTM_NEWADDR address being added to interface

RTM_REDIRECT kernel instructs to use different route

RTM_RESOLVE request to resolve destination to link-layer address

All 12 message types can be used to read information from the kernel. To write to the kernel, the process

can issue RTM_ADD, RTM_DELETE, or RTM_GET message types to update information in the routing

HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (6 pages)

PAGE 1
route(7P) route(7P) NAME route - kernel packet forwarding database SYNOPSIS #include #include #include #include s = socket(AF_ROUTE, SOCK_RAW, family ); DESCRIPTION This manpage describes routing socket interface to read and write kernel routing messages. The information on how to transmit network packets is maintained by the HP-UX kernel in the routing information database, also known as the routing table.
PAGE 2
route(7P) route(7P) table. Message types RTM_CHANGE and RTM_LOCK are not supported on HP-UX. If a user process issues these messages, [EOPNOTSUPP] error will be returned. Message Structure Messages are formed by a message header followed by a small number of socket address structures. What message header to use depends on the message type. The RTM_IFINFO messages use the if_msghdr header. The RTM_NEWADDR and RTM_DELADDR messages use the ifa_msghdr header. All other message types use the rt_msghdr header.
PAGE 3
route(7P) route(7P) /* generic interface information */ uint8_t ifi_type; /* ethernet, tokenring, etc */ uint8_t ifi_physical; /* AUI, Thinnet, 10base-T, etc */ uint8_t ifi_addrlen; /* media address length */ uint8_t ifi_hdrlen; /* media header length */ uint8_t ifi_recvquota; /* polling quota for receive intrs */ uint8_t ifi_xmitquota; /* polling quota for xmit intrs */ uint32_t ifi_mtu; /* maximum transmission unit */ uint32_t ifi_metric; /* routing metric (external only) */ uint32_t ifi_baudrate; /* li
PAGE 4
route(7P) route(7P) ignores any values contained in these fields. This applies to the following fields: Structure Fields Not Used rt_msghdr rtm_use, rtm_inits, rtm_rmx, except for rtm_rmx.rmx_mtu and rtm_rmx.rmx_rtt if_msghdr ifm_data, except for ifm_data.ifi_mtu, ifm_data.ifi_metric, ifm_data.ifi_ipackets, and ifm_data.
PAGE 5
route(7P) route(7P) /* * the destination address being added follows * the routing header */ sin1 = (struct sockaddr_in *)(rtm + 1); sin1->sin_family = AF_INET; sin1->sin_addr.s_addr = inet_addr(argv[1]); /* * the gateway address being added follows the * destination address */ sin2 = (struct sockaddr_in *)(sin1 + 1); sin2->sin_family = AF_INET; sin2->sin_addr.
PAGE 6
(Notes) A (Notes) rA 6 Hewlett-Packard Company −1− HP-UX 11i Version 3: September 2010