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1.. SPDX-License-Identifier: GPL-2.02 3===================4IPVLAN Driver HOWTO5===================6 7Initial Release:8 Mahesh Bandewar <maheshb AT google.com>9 101. Introduction:11================12This is conceptually very similar to the macvlan driver with one major13exception of using L3 for mux-ing /demux-ing among slaves. This property makes14the master device share the L2 with its slave devices. I have developed this15driver in conjunction with network namespaces and not sure if there is use case16outside of it.17 18 192. Building and Installation:20=============================21 22In order to build the driver, please select the config item CONFIG_IPVLAN.23The driver can be built into the kernel (CONFIG_IPVLAN=y) or as a module24(CONFIG_IPVLAN=m).25 26 273. Configuration:28=================29 30There are no module parameters for this driver and it can be configured31using IProute2/ip utility.32::33 34 ip link add link <master> name <slave> type ipvlan [ mode MODE ] [ FLAGS ]35 where36 MODE: l3 (default) | l3s | l237 FLAGS: bridge (default) | private | vepa38 39e.g.40 41 (a) Following will create IPvlan link with eth0 as master in42 L3 bridge mode::43 44 bash# ip link add link eth0 name ipvl0 type ipvlan45 (b) This command will create IPvlan link in L2 bridge mode::46 47 bash# ip link add link eth0 name ipvl0 type ipvlan mode l2 bridge48 49 (c) This command will create an IPvlan device in L2 private mode::50 51 bash# ip link add link eth0 name ipvlan type ipvlan mode l2 private52 53 (d) This command will create an IPvlan device in L2 vepa mode::54 55 bash# ip link add link eth0 name ipvlan type ipvlan mode l2 vepa56 57 584. Operating modes:59===================60 61IPvlan has two modes of operation - L2 and L3. For a given master device,62you can select one of these two modes and all slaves on that master will63operate in the same (selected) mode. The RX mode is almost identical except64that in L3 mode the slaves won't receive any multicast / broadcast traffic.65L3 mode is more restrictive since routing is controlled from the other (mostly)66default namespace.67 684.1 L2 mode:69------------70 71In this mode TX processing happens on the stack instance attached to the72slave device and packets are switched and queued to the master device to send73out. In this mode the slaves will RX/TX multicast and broadcast (if applicable)74as well.75 764.2 L3 mode:77------------78 79In this mode TX processing up to L3 happens on the stack instance attached80to the slave device and packets are switched to the stack instance of the81master device for the L2 processing and routing from that instance will be82used before packets are queued on the outbound device. In this mode the slaves83will not receive nor can send multicast / broadcast traffic.84 854.3 L3S mode:86-------------87 88This is very similar to the L3 mode except that iptables (conn-tracking)89works in this mode and hence it is L3-symmetric (L3s). This will have slightly less90performance but that shouldn't matter since you are choosing this mode over plain-L391mode to make conn-tracking work.92 935. Mode flags:94==============95 96At this time following mode flags are available97 985.1 bridge:99-----------100This is the default option. To configure the IPvlan port in this mode,101user can choose to either add this option on the command-line or don't specify102anything. This is the traditional mode where slaves can cross-talk among103themselves apart from talking through the master device.104 1055.2 private:106------------107If this option is added to the command-line, the port is set in private108mode. i.e. port won't allow cross communication between slaves.109 1105.3 vepa:111---------112If this is added to the command-line, the port is set in VEPA mode.113i.e. port will offload switching functionality to the external entity as114described in 802.1Qbg115Note: VEPA mode in IPvlan has limitations. IPvlan uses the mac-address of the116master-device, so the packets which are emitted in this mode for the adjacent117neighbor will have source and destination mac same. This will make the switch /118router send the redirect message.119 1206. What to choose (macvlan vs. ipvlan)?121=======================================122 123These two devices are very similar in many regards and the specific use124case could very well define which device to choose. if one of the following125situations defines your use case then you can choose to use ipvlan:126 127 128(a) The Linux host that is connected to the external switch / router has129 policy configured that allows only one mac per port.130(b) No of virtual devices created on a master exceed the mac capacity and131 puts the NIC in promiscuous mode and degraded performance is a concern.132(c) If the slave device is to be put into the hostile / untrusted network133 namespace where L2 on the slave could be changed / misused.134 135 1366. Example configuration:137=========================138 139::140 141 +=============================================================+142 | Host: host1 |143 | |144 | +----------------------+ +----------------------+ |145 | | NS:ns0 | | NS:ns1 | |146 | | | | | |147 | | | | | |148 | | ipvl0 | | ipvl1 | |149 | +----------#-----------+ +-----------#----------+ |150 | # # |151 | ################################ |152 | # eth0 |153 +==============================#==============================+154 155 156(a) Create two network namespaces - ns0, ns1::157 158 ip netns add ns0159 ip netns add ns1160 161(b) Create two ipvlan slaves on eth0 (master device)::162 163 ip link add link eth0 ipvl0 type ipvlan mode l2164 ip link add link eth0 ipvl1 type ipvlan mode l2165 166(c) Assign slaves to the respective network namespaces::167 168 ip link set dev ipvl0 netns ns0169 ip link set dev ipvl1 netns ns1170 171(d) Now switch to the namespace (ns0 or ns1) to configure the slave devices172 173 - For ns0::174 175 (1) ip netns exec ns0 bash176 (2) ip link set dev ipvl0 up177 (3) ip link set dev lo up178 (4) ip -4 addr add 127.0.0.1 dev lo179 (5) ip -4 addr add $IPADDR dev ipvl0180 (6) ip -4 route add default via $ROUTER dev ipvl0181 182 - For ns1::183 184 (1) ip netns exec ns1 bash185 (2) ip link set dev ipvl1 up186 (3) ip link set dev lo up187 (4) ip -4 addr add 127.0.0.1 dev lo188 (5) ip -4 addr add $IPADDR dev ipvl1189 (6) ip -4 route add default via $ROUTER dev ipvl1190