1.\" 2.\" Copyright (c) 2001 Yar Tikhiy 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.\" $FreeBSD$ 27.\" 28.Dd December 13, 2006 29.Dt VLAN 4 30.Os 31.Sh NAME 32.Nm vlan 33.Nd "IEEE 802.1Q VLAN network interface" 34.Sh SYNOPSIS 35To compile this driver into the kernel, 36place the following lines in your 37kernel configuration file: 38.Bd -ragged -offset indent 39.Cd "device miibus" 40.Cd "device vlan" 41.Ed 42.Pp 43Alternatively, to load the driver as a 44module at boot time, place the following line in 45.Xr loader.conf 5 : 46.Bd -literal -offset indent 47if_vlan_load="YES" 48.Ed 49.Sh DESCRIPTION 50The 51.Nm 52driver demultiplexes frames tagged according to 53the IEEE 802.1Q standard into logical 54.Nm 55network interfaces, which allows routing/bridging between 56multiple VLANs through a single switch trunk port. 57.Pp 58Each 59.Nm 60interface is created at runtime using interface cloning. 61This is 62most easily done with the 63.Xr ifconfig 8 64.Cm create 65command or using the 66.Va cloned_interfaces 67variable in 68.Xr rc.conf 5 . 69.Pp 70To function, a 71.Nm 72interface must be assigned a parent interface and 73numeric VLAN tag using 74.Xr ifconfig 8 . 75A single parent can be assigned to multiple 76.Nm 77interfaces provided they have different tags. 78The parent interface is likely to be an Ethernet card connected 79to a properly configured switch port. 80The VLAN tag should match one of those set up in the switched 81network. 82.Pp 83Initially 84.Nm 85assumes the same minimum length for tagged and untagged frames. 86This mode is selected by the 87.Xr sysctl 8 88variable 89.Va net.link.vlan.soft_pad 90set to 0 (default). 91However, there are network devices that fail to adjust frame length, 92should it fall below the allowed minimum due to untagging. 93Such devices should be able to interoperate with 94.Nm 95after changing the value of 96.Va net.link.vlan.soft_pad 97to 1. 98In the latter mode, 99.Nm 100will pad short frames before tagging them 101so that their length stays not less than the minimum value 102after untagging by the non-compliant devices. 103.Sh HARDWARE 104The 105.Nm 106driver supports efficient operation over parent interfaces that can provide 107help in processing VLANs. 108Such interfaces are automatically recognized by their capabilities. 109Depending on the level of sophistication found in a physical 110interface, it may do full VLAN processing or just be able to 111receive and transmit frames exceeding the maximum Ethernet frame size 112by the length of a 802.1Q header. 113The capabilities may be user-controlled by the respective parameters to 114.Xr ifconfig 8 , 115.Cm vlanhwtag 116and 117.Cm vlanmtu . 118However, a physical interface is not obliged to react to them: 119It may have either capability enabled permanently without 120a way to turn it off. 121The whole issue is very specific to a particular device and its driver. 122.Pp 123By now, the list of physical interfaces able of full VLAN processing 124in the hardware is limited to the following devices: 125.Xr bge 4 , 126.Xr em 4 , 127.Xr ixgb 4 , 128.Xr msk 4 , 129.Xr nge 4 , 130.Xr re 4 , 131.Xr stge 4 , 132.Xr ti 4 , 133.Xr txp 4 , 134and 135.Xr vge 4 . 136.Pp 137The rest of the Ethernet interfaces can run 138VLANs using software emulation in the 139.Nm 140driver. 141However, most of them lack the capability 142of transmitting and receiving oversized frames. 143Assigning such an interface as the parent to 144.Nm 145will result in a reduced MTU on the corresponding 146.Nm 147interfaces. 148In the modern Internet, this is likely to cause 149.Xr tcp 4 150connectivity problems due to massive, inadequate 151.Xr icmp 4 152filtering that breaks the Path MTU Discovery mechanism. 153.Pp 154The interfaces that support oversized frames are as follows: 155.Bl -tag -width ".Xr fxp 4 " -offset indent 156.It Xr bfe 4 157supports long frames for 158.Nm 159natively. 160.It Xr dc 4 161supports long frames for 162.Nm 163natively. 164.It Xr de 4 165requires defining 166.Dv BIG_PACKET 167in the 168.Pa /usr/src/sys/pci/if_de.c 169source file and rebuilding the kernel 170or module. 171The hack works only for the 21041, 21140, and 21140A chips. 172.It Xr fxp 4 173supports long frames for 174.Nm 175natively. 176.It Xr gem 4 177supports long frames for 178.Nm 179natively. 180.It Xr hme 4 181supports long frames for 182.Nm 183natively. 184.It Xr le 4 185supports long frames for 186.Nm 187natively. 188.It Xr rl 4 189supports long frames for 190.Nm 191natively. 192.It Xr sis 4 193supports long frames for 194.Nm 195natively. 196.It Xr sk 4 197supports long frames for 198.Nm 199natively. 200.It Xr ste 4 201supports long frames for 202.Nm 203natively. 204.It Xr tl 4 205has support for long frames. 206.It Xr tx 4 207supports long frames for 208.Nm 209natively. 210.It Xr xl 4 211supports long frames only if the card is built on a newer chip 212(Cyclone and above). 213.El 214.Pp 215The 216.Nm 217driver automatically recognizes devices that natively support oversized frames 218for 219.Nm 220use and calculates the appropriate frame MTU based on the 221capabilities of the parent interface. 222The other interfaces listed above can handle oversized frames, 223but they do not advertise this ability of theirs. 224The MTU setting on 225.Nm 226can be corrected manually if used in conjunction with such parent interface. 227.Sh SEE ALSO 228.Xr kqueue 2 , 229.Xr miibus 4 , 230.Xr ifconfig 8 , 231.Xr sysctl 8 232.Sh BUGS 233No 802.1Q features except VLAN tagging are implemented. 234.Pp 235.Dv EVFILT_NETDEV 236events on a 237.Nm 238interface will be sent through 239.Xr kqueue 2 240only if the parent interface uses 241.Xr miibus 4 242for link state notification. 243