iproute(3) [plan9 man page]
IPROUTE(3) Library Functions Manual IPROUTE(3) NAME
iproute - Internet route table manager SYNOPSIS
bind -a #P /net /net/iproute /net/ipifc DESCRIPTION
The iproute device allows the specification of routes for families of IP addresses. It maintains a kernel-resident routing table for IP addresses used by TCP, IL and UDP. Each route consists of a destination IP address, an IP mask, and an IP gateway address. Every packet sent by the system is routed according to the route table. An address matches the route table entry when a packet's destination address matches the table destination address under the mask. When a match is found, the packet is sent to the gateway IP address. If there is no match, the packet is sent with the original destination address. If there are several matches, the one whose mask has the fewest leading zeros is chosen. (Because of the definition of IP masks, this mask preserves the largest portion of the address and is therefore the most specific.) This is forced by storing the routes in decreasing number of ones order and returning the first match. The default gateway has no ones in the mask and is thus the last matched. Reading iproute reports the current routes entered in the table. Writing control messages to iproute edits the table. Route entries are made by writing a string of format add ipdest mask ipgateway Entries are deleted by writing a string of format delete ipdest mask The whole table can be cleared by writing the string For example, to install a gateway address to accept all IP packets from a machine: % echo 'add 0.0.0.0 0.0.0.0 131.107.1.5' > /net/iproute % cat /net/iproute 0.0.0.0 & 0.0.0.0 -> 131.107.1.5 Reading ipifc reports the current IP interfaces being used, one line per interface, showing the device, the maximum transfer unit, the local address, the network mask, and the network address. SOURCE
/sys/src/9/port/deviproute.c SEE ALSO
ip(3), ipconfig(8) IPROUTE(3)
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routing(7P) Protocols routing(7P) NAME
routing - system support for packet network routing DESCRIPTION
The network facilities provide general packet routing. The routing interface described here can be used to maintain the system's IPv4 rout- ing table. It has been maintained for compatibility with older applications. The recommended interface for maintaining the system's routing tables is the routing socket, described at route(7P). The routing socket can be used to manipulate both the IPv4 and IPv6 routing tables of the system. Routing table maintenance may be implemented in applications processes. A simple set of data structures compose a "routing table" used in selecting the appropriate network interface when transmitting packets. This table contains a single entry for each route to a specific network or host. The routing table was designed to support routing for the Internet Protocol (IP), but its implementation is protocol independent and thus it may serve other protocols as well. User programs may manipulate this data base with the aid of two ioctl(2) commands, SIOCADDRT and SIOCDELRT. These commands allow the addition and deletion of a single routing table entry, respectively. Routing table manipulations may only be carried out by privileged user. A routing table entry has the following form, as defined in /usr/include/net/route.h: struct rtentry { unit_t rt_hash; /* to speed lookups */ struct sockaddr rt_dst; /* key */ struct sockaddr rt_gateway; /* value */ short rt_flags; /* up/down?, host/net */ short rt_refcnt; /* # held references */ unit_t rt_use; /* raw # packets forwarded */ /* * The kernel does not use this field, and without it the structure is * datamodel independent. */ #if !defined(_KERNEL) struct ifnet *rt_ifp; /* the answer: interface to use */ #endif /* !defined(_KERNEL) */ }; with rt_flags defined from: #define RTF_UP 0x1 /* route usable */ #define RTF_GATEWAY 0x2 /* destination is a gateway */ #define RTF_HOST 0x4 /* host entry (net otherwise) */ There are three types of routing table entries: those for a specific host, those for all hosts on a specific network, and those for any destination not matched by entries of the first two types, called a wildcard route. Each network interface installs a routing table entry when it is initialized. Normally the interface specifies if the route through it is a "direct" connection to the destination host or network. If the route is direct, the transport layer of a protocol family usually requests the packet be sent to the same host specified in the packet. Otherwise, the interface may be requested to address the packet to an entity different from the eventual recipient; essentially, the packet is forwarded. Routing table entries installed by a user process may not specify the hash, reference count, use, or interface fields; these are filled in by the routing routines. If a route is in use when it is deleted, meaning its rt_refcnt is non-zero, the resources associated with it will not be reclaimed until all references to it are removed. User processes read the routing tables through the /dev/ip device. The rt_use field contains the number of packets sent along the route. This value is used to select among multiple routes to the same desti- nation. When multiple routes to the same destination exist, the least used route is selected. A wildcard routing entry is specified with a zero destination address value. Wildcard routes are used only when the system fails to find a route to the destination host and network. The combination of wildcard routes and routing redirects can provide an economical mechanism for routing traffic. ERRORS
EEXIST A request was made to duplicate an existing entry. ESRCH A request was made to delete a non-existent entry. ENOBUFS Insufficient resources were available to install a new route. ENOMEM Insufficient resources were available to install a new route. ENETUNREACH The gateway is not directly reachable. For example, it does not match the destination/subnet on any of the network interfaces. FILES
/dev/ip IP device driver SEE ALSO
route(1M), ioctl(2), route(7P) SunOS 5.10 9 Nov 1999 routing(7P)