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.\" 29.\" $FreeBSD$ 30.\" 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