1.. SPDX-License-Identifier: GPL-2.0 2 3=================== 4IPVLAN Driver HOWTO 5=================== 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 major 13exception of using L3 for mux-ing /demux-ing among slaves. This property makes 14the master device share the L2 with it's slave devices. I have developed this 15driver in conjunction with network namespaces and not sure if there is use case 16outside 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 module 24(CONFIG_IPVLAN=m). 25 26 273. Configuration: 28================= 29 30There are no module parameters for this driver and it can be configured 31using IProute2/ip utility. 32:: 33 34 ip link add link <master> name <slave> type ipvlan [ mode MODE ] [ FLAGS ] 35 where 36 MODE: l3 (default) | l3s | l2 37 FLAGS: bridge (default) | private | vepa 38 39e.g. 40 41 (a) Following will create IPvlan link with eth0 as master in 42 L3 bridge mode:: 43 44 bash# ip link add link eth0 name ipvl0 type ipvlan 45 (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 bridge 48 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 private 52 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 vepa 56 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 will 63operate in the same (selected) mode. The RX mode is almost identical except 64that in L3 mode the slaves wont 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 the 72slave device and packets are switched and queued to the master device to send 73out. 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 attached 80to the slave device and packets are switched to the stack instance of the 81master device for the L2 processing and routing from that instance will be 82used before packets are queued on the outbound device. In this mode the slaves 83will 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 less 90performance but that shouldn't matter since you are choosing this mode over plain-L3 91mode to make conn-tracking work. 92 935. Mode flags: 94============== 95 96At this time following mode flags are available 97 985.1 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 specify 102anything. This is the traditional mode where slaves can cross-talk among 103themselves 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 private 108mode. 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 as 114described in 802.1Qbg 115Note: VEPA mode in IPvlan has limitations. IPvlan uses the mac-address of the 116master-device, so the packets which are emitted in this mode for the adjacent 117neighbor 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 use 124case could very well define which device to choose. if one of the following 125situations 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 has 129 policy configured that allows only one mac per port. 130(b) No of virtual devices created on a master exceed the mac capacity and 131 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 network 133 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 ns0 159 ip netns add ns1 160 161(b) Create two ipvlan slaves on eth0 (master device):: 162 163 ip link add link eth0 ipvl0 type ipvlan mode l2 164 ip link add link eth0 ipvl1 type ipvlan mode l2 165 166(c) Assign slaves to the respective network namespaces:: 167 168 ip link set dev ipvl0 netns ns0 169 ip link set dev ipvl1 netns ns1 170 171(d) Now switch to the namespace (ns0 or ns1) to configure the slave devices 172 173 - For ns0:: 174 175 (1) ip netns exec ns0 bash 176 (2) ip link set dev ipvl0 up 177 (3) ip link set dev lo up 178 (4) ip -4 addr add 127.0.0.1 dev lo 179 (5) ip -4 addr add $IPADDR dev ipvl0 180 (6) ip -4 route add default via $ROUTER dev ipvl0 181 182 - For ns1:: 183 184 (1) ip netns exec ns1 bash 185 (2) ip link set dev ipvl1 up 186 (3) ip link set dev lo up 187 (4) ip -4 addr add 127.0.0.1 dev lo 188 (5) ip -4 addr add $IPADDR dev ipvl1 189 (6) ip -4 route add default via $ROUTER dev ipvl1 190