xref: /freebsd/share/man/man9/rtentry.9 (revision ca987d4641cdcd7f27e153db17c5bf064934faf5)
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31.Dd March 5, 2014
32.Dt RTENTRY 9
33.Os
34.Sh NAME
35.Nm rtentry
36.Nd structure of an entry in the kernel routing table
37.Sh SYNOPSIS
38.In sys/types.h
39.In sys/socket.h
40.In net/route.h
41.Sh DESCRIPTION
42The kernel provides a common mechanism by which all protocols can store
43and retrieve entries from a central table of routes.
44Parts of this
45mechanism are also used to interact with user-level processes by means
46of a socket in the
47.Xr route 4
48pseudo-protocol family.
49The
50.In net/route.h
51header file defines the structures and manifest constants used in this
52facility.
53.Pp
54The basic structure of a route is defined by
55.Vt "struct rtentry" ,
56which includes the following fields:
57.Bl -tag -offset indent -width 6n
58.It Vt "struct radix_node rt_nodes[2]" ;
59Glue used by the radix-tree routines.
60These members also include in
61their substructure the key (i.e., destination address) and mask used
62when the route was created.
63The
64.Fn rt_key rt
65and
66.Fn rt_mask rt
67macros can be used to extract this information (in the form of a
68.Vt "struct sockaddr *" )
69given a
70.Vt "struct rtentry *" .
71.It Vt "struct sockaddr *rt_gateway" ;
72The
73.Dq target
74of the route, which can either represent a destination in its own
75right (some protocols will put a link-layer address here), or some
76intermediate stop on the way to that destination (if the
77.Dv RTF_GATEWAY
78flag is set).
79.It Vt "int rt_flags" ;
80See below.
81If the
82.Dv RTF_UP
83flag is not present, the
84.Fn rtfree
85function will delete the route from the radix tree when the last
86reference drops.
87.It Vt "int rt_refcnt" ;
88Route entries are reference-counted; this field indicates the number
89of external (to the radix tree) references.
90.It Vt "struct ifnet *rt_ifp" ;
91.It Vt "struct ifaddr *rt_ifa" ;
92These two fields represent the
93.Dq answer ,
94as it were, to the question posed by a route lookup; that is, they
95name the interface and interface address to be used in sending a
96packet to the destination or set of destinations which this route
97represents.
98.It Vt "u_long rt_mtu";
99See description of rmx_mtu below.
100.It Vt "u_long rt_weight";
101See description of rmx_weight below.
102.It Vt "u_long rt_expire";
103See description of rmx_expire below.
104.It Vt "counter64_t rt_pksent";
105See description of rmx_pksent below.
106.It Vt "struct rtentry *rt_gwroute" ;
107This member is a reference to a route whose destination is
108.Va rt_gateway .
109It is only used for
110.Dv RTF_GATEWAY
111routes.
112.It Vt "struct mtx rt_mtx" ;
113Mutex to lock this routing entry.
114.El
115.Pp
116The following flag bits are defined:
117.Bl -tag -offset indent -width ".Dv RTF_BLACKHOLE" -compact
118.It Dv RTF_UP
119The route is not deleted.
120.It Dv RTF_GATEWAY
121The route points to an intermediate destination and not the ultimate
122recipient; the
123.Va rt_gateway
124and
125.Va rt_gwroute
126fields name that destination.
127.It Dv RTF_HOST
128This is a host route.
129.It Dv RTF_REJECT
130The destination is presently unreachable.
131This should result in an
132.Er EHOSTUNREACH
133error from output routines.
134.It Dv RTF_DYNAMIC
135This route was created dynamically by
136.Fn rtredirect .
137.It Dv RTF_MODIFIED
138This route was modified by
139.Fn rtredirect .
140.It Dv RTF_DONE
141Used only in the
142.Xr route 4
143protocol, indicating that the request was executed.
144.It Dv RTF_XRESOLVE
145When this route is returned as a result of a lookup, send a report on
146the
147.Xr route 4
148interface requesting that an external process perform resolution for
149this route.
150.It Dv RTF_STATIC
151Indicates that this route was manually added by means of the
152.Xr route 8
153command.
154.It Dv RTF_BLACKHOLE
155Requests that output sent via this route be discarded.
156.It Dv RTF_PROTO1
157.It Dv RTF_PROTO2
158.It Dv RTF_PROTO3
159Protocol-specific.
160.It Dv RTF_PINNED
161Indicates that this route is immutable to a routing protocol.
162.It Dv RTF_LOCAL
163Indicates that the destination of this route is an address configured
164as belonging to this system.
165.It Dv RTF_BROADCAST
166Indicates that the destination is a broadcast address.
167.It Dv RTF_MULTICAST
168Indicates that the destination is a multicast address.
169.El
170.Pp
171Several metrics are supplied in
172.Vt "struct rt_metrics"
173passed with routing control messages via
174.Xr route 4
175API.
176Currently only
177.Vt rmx_mtu , rmx_expire ,
178and
179.Vt rmx_pksent
180metrics are supplied.
181All others are ignored.
182.Pp
183The following metrics are defined by
184.Vt "struct rt_metrics" :
185.Bl -tag -offset indent -width 6n
186.It Vt "u_long rmx_locks" ;
187Flag bits indicating which metrics the kernel is not permitted to
188dynamically modify.
189.It Vt "u_long rmx_mtu" ;
190MTU for this path.
191.It Vt "u_long rmx_hopcount" ;
192Number of intermediate systems on the path to this destination.
193.It Vt "u_long rmx_expire" ;
194The time
195(a la
196.Xr time 3 )
197at which this route should expire, or zero if it should never expire.
198It is the responsibility of individual protocol suites to ensure that routes
199are actually deleted once they expire.
200.It Vt "u_long rmx_recvpipe" ;
201Nominally, the bandwidth-delay product for the path
202.Em from
203the destination
204.Em to
205this system.
206In practice, this value is used to set the size of the
207receive buffer (and thus the window in sliding-window protocols like
208.Tn TCP ) .
209.It Vt "u_long rmx_sendpipe" ;
210As before, but in the opposite direction.
211.It Vt "u_long rmx_ssthresh" ;
212The slow-start threshold used in
213.Tn TCP
214congestion-avoidance.
215.It Vt "u_long rmx_rtt" ;
216The round-trip time to this destination, in units of
217.Dv RMX_RTTUNIT
218per second.
219.It Vt "u_long rmx_rttvar" ;
220The average deviation of the round-trip time to this destination, in
221units of
222.Dv RMX_RTTUNIT
223per second.
224.It Vt "u_long rmx_pksent" ;
225A count of packets successfully sent via this route.
226.It Vt "u_long rmx_filler[4]" ;
227.\" XXX badly named
228Empty space available for protocol-specific information.
229.El
230.Sh SEE ALSO
231.Xr route 4 ,
232.Xr route 8 ,
233.Xr rtalloc 9
234.Sh HISTORY
235The
236.Vt rtentry
237structure first appeared in
238.Bx 4.2 .
239The radix-tree representation of the routing table and the
240.Vt rt_metrics
241structure first appeared in
242.Bx 4.3 reno .
243.Sh AUTHORS
244This manual page was written by
245.An Garrett Wollman .
246.Sh BUGS
247There are a number of historical relics remaining in this interface.
248The
249.Va rt_gateway
250and
251.Va rmx_filler
252fields could be named better.
253