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In a typical IPvlan L3 setup where master is in default-ns and each slave is into different (slave) ns. In this setup egress packet processing for traffic originating from slave-ns will hit all NF_HOOKs in slave-ns as well as default-ns. However same is not true for ingress processing. All these NF_HOOKs are hit only in the slave-ns skipping them in the default-ns. IPvlan in L3 mode is restrictive and if admins want to deploy iptables rules in default-ns, this asymmetric data path makes it impossible to do so. This patch makes use of the l3_rcv() (added as part of l3mdev enhancements) to perform input route lookup on RX packets without changing the skb->dev and then uses nf_hook at NF_INET_LOCAL_IN to change the skb->dev just before handing over skb to L4. Signed-off-by: Mahesh Bandewar <maheshb@google.com> CC: David Ahern <dsa@cumulusnetworks.com> Reviewed-by: David Ahern <dsa@cumulusnetworks.com> Signed-off-by: David S. Miller <davem@davemloft.net>
113 lines
4.6 KiB
Plaintext
113 lines
4.6 KiB
Plaintext
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IPVLAN Driver HOWTO
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Initial Release:
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Mahesh Bandewar <maheshb AT google.com>
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1. Introduction:
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This is conceptually very similar to the macvlan driver with one major
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exception of using L3 for mux-ing /demux-ing among slaves. This property makes
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the master device share the L2 with it's slave devices. I have developed this
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driver in conjunction with network namespaces and not sure if there is use case
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outside of it.
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2. Building and Installation:
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In order to build the driver, please select the config item CONFIG_IPVLAN.
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The driver can be built into the kernel (CONFIG_IPVLAN=y) or as a module
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(CONFIG_IPVLAN=m).
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3. Configuration:
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There are no module parameters for this driver and it can be configured
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using IProute2/ip utility.
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ip link add link <master-dev> <slave-dev> type ipvlan mode { l2 | l3 | l3s }
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e.g. ip link add link ipvl0 eth0 type ipvlan mode l2
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4. Operating modes:
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IPvlan has two modes of operation - L2 and L3. For a given master device,
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you can select one of these two modes and all slaves on that master will
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operate in the same (selected) mode. The RX mode is almost identical except
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that in L3 mode the slaves wont receive any multicast / broadcast traffic.
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L3 mode is more restrictive since routing is controlled from the other (mostly)
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default namespace.
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4.1 L2 mode:
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In this mode TX processing happens on the stack instance attached to the
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slave device and packets are switched and queued to the master device to send
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out. In this mode the slaves will RX/TX multicast and broadcast (if applicable)
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as well.
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4.2 L3 mode:
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In this mode TX processing up to L3 happens on the stack instance attached
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to the slave device and packets are switched to the stack instance of the
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master device for the L2 processing and routing from that instance will be
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used before packets are queued on the outbound device. In this mode the slaves
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will not receive nor can send multicast / broadcast traffic.
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4.3 L3S mode:
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This is very similar to the L3 mode except that iptables (conn-tracking)
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works in this mode and hence it is L3-symmetric (L3s). This will have slightly less
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performance but that shouldn't matter since you are choosing this mode over plain-L3
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mode to make conn-tracking work.
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5. What to choose (macvlan vs. ipvlan)?
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These two devices are very similar in many regards and the specific use
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case could very well define which device to choose. if one of the following
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situations defines your use case then you can choose to use ipvlan -
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(a) The Linux host that is connected to the external switch / router has
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policy configured that allows only one mac per port.
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(b) No of virtual devices created on a master exceed the mac capacity and
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puts the NIC in promiscuous mode and degraded performance is a concern.
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(c) If the slave device is to be put into the hostile / untrusted network
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namespace where L2 on the slave could be changed / misused.
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6. Example configuration:
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+=============================================================+
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| Host: host1 |
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| +----------------------+ +----------------------+ |
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| | NS:ns0 | | NS:ns1 | |
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| | | | | |
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| | | | | |
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| | ipvl0 | | ipvl1 | |
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| +----------#-----------+ +-----------#----------+ |
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| # # |
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| ################################ |
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| # eth0 |
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+==============================#==============================+
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(a) Create two network namespaces - ns0, ns1
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ip netns add ns0
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ip netns add ns1
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(b) Create two ipvlan slaves on eth0 (master device)
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ip link add link eth0 ipvl0 type ipvlan mode l2
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ip link add link eth0 ipvl1 type ipvlan mode l2
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(c) Assign slaves to the respective network namespaces
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ip link set dev ipvl0 netns ns0
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ip link set dev ipvl1 netns ns1
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(d) Now switch to the namespace (ns0 or ns1) to configure the slave devices
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- For ns0
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(1) ip netns exec ns0 bash
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(2) ip link set dev ipvl0 up
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(3) ip link set dev lo up
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(4) ip -4 addr add 127.0.0.1 dev lo
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(5) ip -4 addr add $IPADDR dev ipvl0
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(6) ip -4 route add default via $ROUTER dev ipvl0
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- For ns1
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(1) ip netns exec ns1 bash
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(2) ip link set dev ipvl1 up
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(3) ip link set dev lo up
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(4) ip -4 addr add 127.0.0.1 dev lo
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(5) ip -4 addr add $IPADDR dev ipvl1
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(6) ip -4 route add default via $ROUTER dev ipvl1
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