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