1.\" 2.\" Copyright 1996 Massachusetts Institute of Technology 3.\" 4.\" Permission to use, copy, modify, and distribute this software and 5.\" its documentation for any purpose and without fee is hereby 6.\" granted, provided that both the above copyright notice and this 7.\" permission notice appear in all copies, that both the above 8.\" copyright notice and this permission notice appear in all 9.\" supporting documentation, and that the name of M.I.T. not be used 10.\" in advertising or publicity pertaining to distribution of the 11.\" software without specific, written prior permission. M.I.T. makes 12.\" no representations about the suitability of this software for any 13.\" purpose. It is provided "as is" without express or implied 14.\" warranty. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''. M.I.T. DISCLAIMS 17.\" ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE, 18.\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 19.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT 20.\" SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22.\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF 23.\" USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 24.\" ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 25.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 26.\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27.\" SUCH DAMAGE. 28.\"
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29.\" $FreeBSD: head/share/man/man9/rtentry.9 256618 2013-10-16 10:36:42Z melifaro $
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29.\" $FreeBSD: head/share/man/man9/rtentry.9 262763 2014-03-05 01:17:47Z glebius $ |
30.\"
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31.Dd October 16, 2013
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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.
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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.
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92.It Vt "struct rt_metrics_lite rt_rmx" ;
93See below.
94If the
95.Dv RTF_UP
96flag is not present, the
97.Fn rtfree
98function will delete the route from the radix tree when the last
99reference drops.
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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_PRCLONING 161This flag is obsolete and simply ignored by facility. 162.It Dv RTF_PINNED 163Indicates that this route is immutable to a routing protocol. 164.It Dv RTF_LOCAL 165Indicates that the destination of this route is an address configured 166as belonging to this system. 167.It Dv RTF_BROADCAST 168Indicates that the destination is a broadcast address. 169.It Dv RTF_MULTICAST 170Indicates that the destination is a multicast address. 171.El 172.Pp
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167Every route has associated with it a set of metrics, stored in
168.Vt "struct rt_metrics_lite" .
169Metrics are supplied in
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173Several metrics are supplied in |
174.Vt "struct rt_metrics" 175passed with routing control messages via 176.Xr route 4 177API. 178Currently only 179.Vt rmx_mtu , rmx_expire , 180and 181.Vt rmx_pksent
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178metrics are used in
179.Vt "struct rt_metrics_lite" .
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182metrics are supplied. |
183All others are ignored. 184.Pp 185The following metrics are defined by 186.Vt "struct rt_metrics" : 187.Bl -tag -offset indent -width 6n 188.It Vt "u_long rmx_locks" ; 189Flag bits indicating which metrics the kernel is not permitted to 190dynamically modify. 191.It Vt "u_long rmx_mtu" ; 192MTU for this path. 193.It Vt "u_long rmx_hopcount" ; 194Number of intermediate systems on the path to this destination. 195.It Vt "u_long rmx_expire" ; 196The time 197(a la 198.Xr time 3 ) 199at which this route should expire, or zero if it should never expire. 200It is the responsibility of individual protocol suites to ensure that routes 201are actually deleted once they expire. 202.It Vt "u_long rmx_recvpipe" ; 203Nominally, the bandwidth-delay product for the path 204.Em from 205the destination 206.Em to 207this system. 208In practice, this value is used to set the size of the 209receive buffer (and thus the window in sliding-window protocols like 210.Tn TCP ) . 211.It Vt "u_long rmx_sendpipe" ; 212As before, but in the opposite direction. 213.It Vt "u_long rmx_ssthresh" ; 214The slow-start threshold used in 215.Tn TCP 216congestion-avoidance. 217.It Vt "u_long rmx_rtt" ; 218The round-trip time to this destination, in units of 219.Dv RMX_RTTUNIT 220per second. 221.It Vt "u_long rmx_rttvar" ; 222The average deviation of the round-trip time to this destination, in 223units of 224.Dv RMX_RTTUNIT 225per second. 226.It Vt "u_long rmx_pksent" ; 227A count of packets successfully sent via this route. 228.It Vt "u_long rmx_filler[4]" ; 229.\" XXX badly named 230Empty space available for protocol-specific information. 231.El 232.Sh SEE ALSO 233.Xr route 4 , 234.Xr route 8 , 235.Xr rtalloc 9 236.Sh HISTORY 237The 238.Vt rtentry 239structure first appeared in 240.Bx 4.2 . 241The radix-tree representation of the routing table and the 242.Vt rt_metrics 243structure first appeared in 244.Bx 4.3 reno . 245.Sh AUTHORS 246This manual page was written by 247.An Garrett Wollman . 248.Sh BUGS 249There are a number of historical relics remaining in this interface. 250The 251.Va rt_gateway 252and 253.Va rmx_filler 254fields could be named better.
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