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.Dd October 8, 1996 31.Os 32.Dt RTENTRY 9 33.Sh NAME 34.Nm rtentry 35.Nd structure of an entry in the kernel routing table 36.Sh SYNOPSIS 37.Fd #include <sys/types.h> 38.Fd #include <sys/socket.h> 39.Fd #include <net/route.h> 40.Sh DESCRIPTION 41The kernel provides a common mechanism by which all protocols can store 42and retrieve entries from a central table of routes. Parts of this 43mechanism are also used to interact with user-level processes by means 44of a socket in the 45.Xr route 4 46pseudo-protocol family. 47The 48.Aq Pa net/route.h 49header file defines the structures and manifest constants used in this 50facility. 51.Pp 52The basic structure a route is defined by 53.Dq Li struct rtentry , 54which includes the following fields: 55.Bl -tag -offset indent -width 6n 56.It Li "struct radix_node rt_nodes[2];" 57Glue used by the radix-tree routines. These members also include in 58their substructure the key (i.e., destination address) and mask used 59when the route was created. The 60.Fn rt_key \&rt 61and 62.Fn rt_mask \&rt 63macros can be used to extract this information (in the form of a 64.Dq Li "struct sockaddr *" ) 65given a 66.Li "struct rtentry *" . 67.It Li "struct sockaddr *rt_gateway;" 68The 69.Dq target 70of the route, which can either represent a destination in its own 71right (some protocols will put a link-layer address here), or some 72intermediate stop on the way to that destination (if the 73.Dv RTF_GATEWAY 74flag is set). 75.It Li "long rt_refcnt;" 76Route entries are reference-counted; this field indicates the number 77of external (to the radix tree) references. If the 78.Dv RTF_UP 79flag is not present, the 80.Fn rtfree 81function will delete the route from the radix tree when the last 82reference drops. 83.It Li "u_long rt_flags;" 84See below. 85.It Li "struct ifnet *rt_ifp;" 86.It Li "struct ifaddr *rt_ifa;" 87These two fields represent the 88.Dq answer , 89as it were, to the question posed by a route lookup; that is, they 90name the interface and interface address to be used in sending a 91packet to the destination or set of destinations which this route 92represents. 93.It Li "struct sockaddr *rt_genmask;" 94When the 95.Fn rtalloc 96family of functions performs a cloning operation as requested by the 97.Dv RTF_CLONING 98or 99.Dv RTF_PRCLONING 100flag, this field is used as the mask for the new route which is 101inserted into the table. If this field is a null pointer, then a host 102route is generated. 103.It Li "caddr_t rt_llinfo;" 104When the 105.Dv RTF_LLINFO 106flag is set, this field contains information specific to the link 107layer represented by the named interface address. (It is normally 108managed by the 109.Fn rt_ifa->ifa_rtrequest 110routine.) Protocols such as 111.Xr arp 4 112use this field to reference per-destination state internal to that 113protocol. 114.It Li "struct rt_metrics rt_rmx;" 115See below. 116.It Li "struct rtentry *rt_gwroute;" 117This member is a reference to a route whose destination is 118.Li rt_gateway . 119It is only used for 120.Dv RTF_GATEWAY 121routes. 122.\" .It Dv "int (*rt_output)();" 123.\" See below. 124.It Dv "struct rtentry *rt_parent;" 125A reference to the route from which this route was cloned, or a null 126pointer if this route was not generated by cloning. See also the 127.Dv RTF_WASCLONED 128flag. 129.El 130.Pp 131The following flag bits are defined: 132.Bl -tag -offset indent -width RTF_CHAINDELETE -compact 133.It Dv RTF_UP 134The route is not deleted. 135.It Dv RTF_GATEWAY 136The route points to an intermediate destination and not the ultimate 137recipient; the 138.Li rt_gateway 139and 140.Li rt_gwroute 141fields name that destination. 142.It Dv RTF_HOST 143This is a host route. 144.It Dv RTF_REJECT 145The destination is presently unreachable. This should result in an 146.Er EHOSTUNREACH 147error from output routines. 148.It Dv RTF_DYNAMIC 149This route was created dynamically by 150.Fn rtredirect . 151.It Dv RTF_MODIFIED 152This route was modified by 153.Fn rtredirect . 154.It Dv RTF_DONE 155Used only in the 156.Xr route 4 157protocol, indicating that the request was executed. 158.It Dv RTF_CLONING 159When this route is returned as a result of a lookup, automatically 160create a new route using this one as a template and 161.Li rt_genmask 162(if present) as a mask. 163.It Dv RTF_XRESOLVE 164When this route is returned as a result of a lookup, send a report on 165the 166.Xr route 4 167interface requesting that an external process perform resolution for 168this route. (Used in conjunction with 169.Dv RTF_CLONING . ) 170.It Dv RTF_LLINFO 171Indicates that this route represents information being managed by a 172link layer's adaptation layer (e.g., 173.Tn ARP ) . 174.It Dv RTF_STATIC 175Indicates that this route was manually added by means of the 176.Xr route 8 177command. 178.It Dv RTF_BLACKHOLE 179Requests that output sent via this route be discarded. 180.It Dv RTF_PROTO1 181.It Dv RTF_PROTO2 182.It Dv RTF_PROTO3 183Protocol-specific. 184.It Dv RTF_PRCLONING 185Like 186.Dv RTF_CLONING , 187only managed by an entire protocol. (E.g., 188.Tn IP 189uses this flag to manage a per-host cache integrated with the routing 190table, for those destinations which do not have a link layer 191performing this function.) 192.It Dv RTF_WASCLONED 193Indicates that this route was generated as a result of cloning 194requested by the 195.Dv RTF_CLONING 196or 197.Dv RTF_PRCLONING 198flag. When set, the 199.Li rt_parent 200field indicates the route from which this one was generated. 201.It Dv RTF_PINNED 202(Reserved for future use to indicate routes which are not to be 203modified by a routing protocol.) 204.It Dv RTF_LOCAL 205Indicates that the destination of this route is an address configured 206as belonging to this system. 207.It Dv RTF_BROADCAST 208Indicates that the destination is a broadcast address. 209.It Dv RTF_MULTICAST 210Indicates that the destination is a multicast address. 211.El 212.Pp 213Every route has associated with it a set of metrics, defined by 214.Li struct rt_metrics : 215.Bl -tag -offset indent -width 6n 216.It Li "u_long rmx_locks;" 217Flag bits indicating which metrics the kernel is not permitted to 218dynamically modify. 219.It Li "u_long rmx_mtu;" 220MTU for this path. 221.It Li "u_long rmx_hopcount;" 222Number of intermediate systems on the path to this destination. 223.It Li "u_long rmx_expire;" 224The time 225(\*(aga la 226.Xr time 3 ) 227at which this route should expire, or zero if it should never expire. 228It is the responsibility of individual protocol suites to ensure that routes 229are actually deleted once they expire. 230.It Li "u_long rmx_recvpipe;" 231Nominally, the bandwidth-delay product for the path 232.Em from 233the destination 234.Em to 235this system. In practice, this value is used to set the size of the 236receive buffer (and thus the window in sliding-window protocols like 237.Tn TCP ) . 238.It Li "u_long rmx_sendpipe;" 239As before, but in the opposite direction. 240.It Li "u_long rmx_ssthresh;" 241The slow-start threshold used in 242.Tn TCP 243congestion-avoidance. 244.It Li "u_long rmx_rtt;" 245The round-trip time to this destination, in units of 246.Dv RMX_RTTUNIT 247per second. 248.It Li "u_long rmx_rttvar;" 249The average deviation of the round-type time to this destination, in 250units of 251.Dv RMX_RTTUNIT 252per second. 253.It Li "u_long rmx_pksent;" 254A count of packets successfully sent via this route. 255.It Li "u_long rmx_filler[4];" 256.\" XXX badly named 257Empty space available for protocol-specific information. 258.El 259.Sh SEE ALSO 260.Xr route 4 , 261.Xr route 8 , 262.Xr rtalloc 9 263.Sh HISTORY 264The 265.Nm rtentry 266structure first appeared in 267.Bx 4.2 . 268The radix-tree representation of the routing table and the 269.Nm rt_metrics 270structure first appeared in 271.Bx 4.3 reno . 272The 273.Nm RTF_PRCLONING 274mechanism first appeared in 275.Fx 2.0 . 276.Sh BUGS 277There are a number of historical relics remaining in this interface. 278The 279.Li rt_gateway 280and 281.Li rmx_filler 282fields could be named better. 283.Pp 284There is some disagreement over whether it is legitimate for 285.Dv RTF_LLINFO 286to be set by any process other than 287.Fn rt_ifa->ifa_rtrequest . 288.Sh AUTHORS 289This manual page was written by 290.An Garrett Wollman . 291