1routing(7P) Protocols routing(7P)
2
6 routing - system support for packet network routing
7
9 The network facilities provide general packet routing. The routing
10 interface described here can be used to maintain the system's IPv4
11 routing table. It has been maintained for compatibility with older
12 applications. The recommended interface for maintaining the system's
13 routing tables is the routing socket, described at route(7P). The rout‐
14 ing socket can be used to manipulate both the IPv4 and IPv6 routing
15 tables of the system. Routing table maintenance may be implemented in
16 applications processes.
17 A simple set of data structures compose a "routing table" used in
20 selecting the appropriate network interface when transmitting packets.
21 This table contains a single entry for each route to a specific network
22 or host. The routing table was designed to support routing for the
23 Internet Protocol (IP), but its implementation is protocol independent
24 and thus it may serve other protocols as well. User programs may manip‐
25 ulate this data base with the aid of two ioctl(2) commands, SIOCADDRT
26 and SIOCDELRT. These commands allow the addition and deletion of a sin‐
27 gle routing table entry, respectively. Routing table manipulations may
28 only be carried out by privileged user.
29 A routing table entry has the following form, as defined in
32 /usr/include/net/route.h:
33 struct rtentry {
35 unit_t rt_hash; /* to speed lookups */
36 struct sockaddr rt_dst; /* key */
37 struct sockaddr rt_gateway; /* value */
38 short rt_flags; /* up/down?, host/net */
39 short rt_refcnt; /* # held references */
40 unit_t rt_use; /* raw # packets forwarded */
41 /*
42 * The kernel does not use this field, and without it the structure is
43 * datamodel independent.
44 */
45 #if !defined(_KERNEL)
46 struct ifnet *rt_ifp; /* the answer: interface to use */
47 #endif /* !defined(_KERNEL) */
48 };
49 with rt_flags defined from:
53 #define RTF_UP 0x1 /* route usable */
55 #define RTF_GATEWAY 0x2 /* destination is a gateway */
56 #define RTF_HOST 0x4 /* host entry (net otherwise) */
57 There are three types of routing table entries: those for a specific
61 host, those for all hosts on a specific network, and those for any
62 destination not matched by entries of the first two types, called a
63 wildcard route. Each network interface installs a routing table entry
64 when it is initialized. Normally the interface specifies if the route
65 through it is a "direct" connection to the destination host or network.
66 If the route is direct, the transport layer of a protocol family usu‐
67 ally requests the packet be sent to the same host specified in the
68 packet. Otherwise, the interface may be requested to address the packet
69 to an entity different from the eventual recipient; essentially, the
70 packet is forwarded.
71 Routing table entries installed by a user process may not specify the
74 hash, reference count, use, or interface fields; these are filled in by
75 the routing routines. If a route is in use when it is deleted, meaning
76 its rt_refcnt is non-zero, the resources associated with it will not be
77 reclaimed until all references to it are removed.
78 User processes read the routing tables through the /dev/ip device.
81 The rt_use field contains the number of packets sent along the route.
84 This value is used to select among multiple routes to the same destina‐
85 tion. When multiple routes to the same destination exist, the least
86 used route is selected.
87 A wildcard routing entry is specified with a zero destination address
90 value. Wildcard routes are used only when the system fails to find a
91 route to the destination host and network. The combination of wildcard
92 routes and routing redirects can provide an economical mechanism for
93 routing traffic.
94
96 EEXIST A request was made to duplicate an existing entry.
97 ESRCH A request was made to delete a non-existent entry.
100 ENOBUFS Insufficient resources were available to install a new
103 route.
104 ENOMEM Insufficient resources were available to install a new
107 route.
108 ENETUNREACH The gateway is not directly reachable. For example, it
111 does not match the destination/subnet on any of the net‐
112 work interfaces.
113
116 /dev/ip IP device driver
117
120 route(1M), ioctl(2), route(7P)
121SunOS 5.11 9 Nov 1999 routing(7P)