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diff --git a/tutorial/Tutorial.md b/tutorial/Tutorial.md deleted file mode 100644 index fefa8c8f6..000000000 --- a/tutorial/Tutorial.md +++ /dev/null @@ -1,859 +0,0 @@ -Open vSwitch Advanced Features Tutorial -======================================= - -Many tutorials cover the basics of OpenFlow. This is not such a -tutorial. Rather, a knowledge of the basics of OpenFlow is a -prerequisite. If you do not already understand how an OpenFlow flow -table works, please go read a basic tutorial and then continue reading -here afterward. - -It is also important to understand the basics of Open vSwitch before -you begin. If you have never used `ovs-vsctl` or `ovs-ofctl` before, -you should learn a little about them before proceeding. - -Most of the features covered in this tutorial are Open vSwitch -extensions to OpenFlow. Also, most of the features in this tutorial -are specific to the software Open vSwitch implementation. If you are -using an Open vSwitch port to an ASIC-based hardware switch, this -tutorial will not help you. - -This tutorial does not cover every aspect of the features that it -mentions. You can find the details elsewhere in the Open vSwitch -documentation, especially `ovs-ofctl(8)` and the comments in the -`include/openflow/nicira-ext.h` and `include/openvswitch/meta-flow.h` -header files. - -> In this tutorial, paragraphs set off like this designate notes -> with additional information that readers may wish to skip on a -> first read. - -Getting Started ---------------- - -This is a hands-on tutorial. To get the most out of it, you will need -Open vSwitch binaries. You do not, on the other hand, need any -physical networking hardware or even supervisor privilege on your -system. Instead, we will use a script called `ovs-sandbox`, which -accompanies the tutorial, that constructs a software simulated network -environment based on Open vSwitch. - -You can use `ovs-sandbox` three ways: - - * If you have already installed Open vSwitch on your system, then - you should be able to just run `ovs-sandbox` from this directory - without any options. - - * If you have not installed Open vSwitch (and you do not want to - install it), then you can build Open vSwitch according to the - instructions in [INSTALL.rst], without installing it. Then run - `./ovs-sandbox -b DIRECTORY` from this directory, substituting - the Open vSwitch build directory for `DIRECTORY`. - - * As a slight variant on the latter, you can run `make sandbox` - from an Open vSwitch build directory. - -When you run `ovs-sandbox`, it does the following: - - 1. **CAUTION:** Deletes any subdirectory of the current directory - named "sandbox" and any files in that directory. - - 2. Creates a new directory "sandbox" in the current directory. - - 3. Sets up special environment variables that ensure that Open - vSwitch programs will look inside the "sandbox" directory - instead of in the Open vSwitch installation directory. - - 4. If you are using a built but not installed Open vSwitch, - installs the Open vSwitch manpages in a subdirectory of - "sandbox" and adjusts the `MANPATH` environment variable to point - to this directory. This means that you can use, for example, - `man ovs-vsctl` to see a manpage for the `ovs-vsctl` program that - you built. - - 5. Creates an empty Open vSwitch configuration database under - "sandbox". - - 6. Starts `ovsdb-server` running under "sandbox". - - 7. Starts `ovs-vswitchd` running under "sandbox", passing special - options that enable a special "dummy" mode for testing. - - 8. Starts a nested interactive shell inside "sandbox". - -At this point, you can run all the usual Open vSwitch utilities from -the nested shell environment. You can, for example, use `ovs-vsctl` -to create a bridge: - - ovs-vsctl add-br br0 - -From Open vSwitch's perspective, the bridge that you create this way -is as real as any other. You can, for example, connect it to an -OpenFlow controller or use `ovs-ofctl` to examine and modify it and -its OpenFlow flow table. On the other hand, the bridge is not visible -to the operating system's network stack, so `ifconfig` or `ip` cannot -see it or affect it, which means that utilities like `ping` and -`tcpdump` will not work either. (That has its good side, too: you -can't screw up your computer's network stack by manipulating a -sandboxed OVS.) - -When you're done using OVS from the sandbox, exit the nested shell (by -entering the "exit" shell command or pressing Control+D). This will -kill the daemons that `ovs-sandbox` started, but it leaves the "sandbox" -directory and its contents in place. - -The sandbox directory contains log files for the Open vSwitch dameons. -You can examine them while you're running in the sandboxed environment -or after you exit. - -Using GDB ---------- - -GDB support is not required to go through the tutorial. It is added in case -user wants to explore the internals of OVS programs. - -GDB can already be used to debug any running process, with the usual -'gdb <program> <process-id>' command. - -'ovs-sandbox' also has a '-g' option for launching ovs-vswitchd under GDB. -This option can be handy for setting break points before ovs-vswitchd runs, -or for catching early segfaults. Similarly, a '-d' option can be used to -run ovsdb-server under GDB. Both options can be specified at the same time. - -In addition, a '-e' option also launches ovs-vswitchd under GDB. However, -instead of displaying a 'gdb>' prompt and waiting for user input, ovs-vswitchd -will start to execute immediately. '-r' option is the corresponding option -for running ovsdb-server under gdb with immediate execution. - -To avoid GDB mangling with the sandbox sub shell terminal, 'ovs-sandbox' -starts a new xterm to run each GDB session. For systems that do not support -X windows, GDB support is effectively disabled. - -When launching sandbox through the build tree's make file, the '-g' option -can be passed via the 'SANDBOXFLAGS' environment variable. -'make sandbox SANDBOXFLAGS=-g' will start the sandbox with ovs-vswitchd -running under GDB in its own xterm if X is available. - -Motivation ----------- - -The goal of this tutorial is to demonstrate the power of Open vSwitch -flow tables. The tutorial works through the implementation of a -MAC-learning switch with VLAN trunk and access ports. Outside of the -Open vSwitch features that we will discuss, OpenFlow provides at least -two ways to implement such a switch: - - 1. An OpenFlow controller to implement MAC learning in a - "reactive" fashion. Whenever a new MAC appears on the switch, - or a MAC moves from one switch port to another, the controller - adjusts the OpenFlow flow table to match. - - 2. The "normal" action. OpenFlow defines this action to submit a - packet to "the traditional non-OpenFlow pipeline of the - switch". That is, if a flow uses this action, then the packets - in the flow go through the switch in the same way that they - would if OpenFlow was not configured on the switch. - -Each of these approaches has unfortunate pitfalls. In the first -approach, using an OpenFlow controller to implement MAC learning, has -a significant cost in terms of network bandwidth and latency. It also -makes the controller more difficult to scale to large numbers of -switches, which is especially important in environments with thousands -of hypervisors (each of which contains a virtual OpenFlow switch). -MAC learning at an OpenFlow controller also behaves poorly if the -OpenFlow controller fails, slows down, or becomes unavailable due to -network problems. - -The second approach, using the "normal" action, has different -problems. First, little about the "normal" action is standardized, so -it behaves differently on switches from different vendors, and the -available features and how those features are configured (usually not -through OpenFlow) varies widely. Second, "normal" does not work well -with other OpenFlow actions. It is "all-or-nothing", with little -potential to adjust its behavior slightly or to compose it with other -features. - - -Scenario --------- - -We will construct Open vSwitch flow tables for a VLAN-capable, -MAC-learning switch that has four ports: - - * p1, a trunk port that carries all VLANs, on OpenFlow port 1. - - * p2, an access port for VLAN 20, on OpenFlow port 2. - - * p3 and p4, both access ports for VLAN 30, on OpenFlow ports 3 - and 4, respectively. - -> The ports' names are not significant. You could call them eth1 -> through eth4, or any other names you like. - -> An OpenFlow switch always has a "local" port as well. This -> scenario won't use the local port. - -Our switch design will consist of five main flow tables, each of which -implements one stage in the switch pipeline: - - Table 0: Admission control. - - Table 1: VLAN input processing. - - Table 2: Learn source MAC and VLAN for ingress port. - - Table 3: Look up learned port for destination MAC and VLAN. - - Table 4: Output processing. - -The section below describes how to set up the scenario, followed by a -section for each OpenFlow table. - -You can cut and paste the `ovs-vsctl` and `ovs-ofctl` commands in each -of the sections below into your `ovs-sandbox` shell. They are also -available as shell scripts in this directory, named `t-setup`, `t-stage0`, -`t-stage1`, ..., `t-stage4`. The `ovs-appctl` test commands are intended -for cutting and pasting and are not supplied separately. - - -Setup ------ - -To get started, start `ovs-sandbox`. Inside the interactive shell -that it starts, run this command: - - ovs-vsctl add-br br0 -- set Bridge br0 fail-mode=secure - -This command creates a new bridge "br0" and puts "br0" into so-called -"fail-secure" mode. For our purpose, this just means that the -OpenFlow flow table starts out empty. - -> If we did not do this, then the flow table would start out with a -> single flow that executes the "normal" action. We could use that -> feature to yield a switch that behaves the same as the switch we -> are currently building, but with the caveats described under -> "Motivation" above.) - -The new bridge has only one port on it so far, the "local port" br0. -We need to add p1, p2, p3, and p4. A shell "for" loop is one way to -do it: - - for i in 1 2 3 4; do - ovs-vsctl add-port br0 p$i -- set Interface p$i ofport_request=$i - ovs-ofctl mod-port br0 p$i up - done - -In addition to adding a port, the `ovs-vsctl` command above sets its -"ofport_request" column to ensure that port p1 is assigned OpenFlow -port 1, p2 is assigned OpenFlow port 2, and so on. - -> We could omit setting the ofport_request and let Open vSwitch -> choose port numbers for us, but it's convenient for the purposes -> of this tutorial because we can talk about OpenFlow port 1 and -> know that it corresponds to p1. - -The `ovs-ofctl` command above brings up the simulated interfaces, which -are down initially, using an OpenFlow request. The effect is similar -to `ifconfig up`, but the sandbox's interfaces are not visible to the -operating system and therefore `ifconfig` would not affect them. - -We have not configured anything related to VLANs or MAC learning. -That's because we're going to implement those features in the flow -table. - -To see what we've done so far to set up the scenario, you can run a -command like `ovs-vsctl show` or `ovs-ofctl show br0`. - - -Implementing Table 0: Admission control ---------------------------------------- - -Table 0 is where packets enter the switch. We use this stage to -discard packets that for one reason or another are invalid. For -example, packets with a multicast source address are not valid, so we -can add a flow to drop them at ingress to the switch with: - - ovs-ofctl add-flow br0 \ - "table=0, dl_src=01:00:00:00:00:00/01:00:00:00:00:00, actions=drop" - -A switch should also not forward IEEE 802.1D Spanning Tree Protocol -(STP) packets, so we can also add a flow to drop those and other -packets with reserved multicast protocols: - - ovs-ofctl add-flow br0 \ - "table=0, dl_dst=01:80:c2:00:00:00/ff:ff:ff:ff:ff:f0, actions=drop" - -We could add flows to drop other protocols, but these demonstrate the -pattern. - -We need one more flow, with a priority lower than the default, so that -flows that don't match either of the "drop" flows we added above go on -to pipeline stage 1 in OpenFlow table 1: - - ovs-ofctl add-flow br0 "table=0, priority=0, actions=resubmit(,1)" - -(The "resubmit" action is an Open vSwitch extension to OpenFlow.) - - -### Testing Table 0 - -If we were using Open vSwitch to set up a physical or a virtual -switch, then we would naturally test it by sending packets through it -one way or another, perhaps with common network testing tools like -`ping` and `tcpdump` or more specialized tools like Scapy. That's -difficult with our simulated switch, since it's not visible to the -operating system. - -But our simulated switch has a few specialized testing tools. The -most powerful of these tools is `ofproto/trace`. Given a switch and -the specification of a flow, `ofproto/trace` shows, step-by-step, how -such a flow would be treated as it goes through the switch. - - -### EXAMPLE 1 - -Try this command: - - ovs-appctl ofproto/trace br0 in_port=1,dl_dst=01:80:c2:00:00:05 - -The output should look something like this: - - Flow: metadata=0,in_port=1,vlan_tci=0x0000,dl_src=00:00:00:00:00:00,dl_dst=01:80:c2:00:00:05,dl_type=0x0000 - Rule: table=0 cookie=0 dl_dst=01:80:c2:00:00:00/ff:ff:ff:ff:ff:f0 - OpenFlow actions=drop - - Final flow: unchanged - Datapath actions: drop - -The first block of lines describes an OpenFlow table lookup. The -first line shows the fields used for the table lookup (which is mostly -zeros because that's the default if we don't specify everything). The -second line gives the OpenFlow flow that the fields matched (called a -"rule" because that is the name used inside Open vSwitch for an -OpenFlow flow). In this case, we see that this packet that has a -reserved multicast destination address matches the rule that drops -those packets. The third line gives the rule's OpenFlow actions. - -The second block of lines summarizes the results, which are not very -interesting here. - - -### EXAMPLE 2 - -Try another command: - - ovs-appctl ofproto/trace br0 in_port=1,dl_dst=01:80:c2:00:00:10 - -The output should be: - - Flow: metadata=0,in_port=1,vlan_tci=0x0000,dl_src=00:00:00:00:00:00,dl_dst=01:80:c2:00:00:10,dl_type=0x0000 - Rule: table=0 cookie=0 priority=0 - OpenFlow actions=resubmit(,1) - - Resubmitted flow: unchanged - Resubmitted regs: reg0=0x0 reg1=0x0 reg2=0x0 reg3=0x0 reg4=0x0 reg5=0x0 reg6=0x0 reg7=0x0 - Resubmitted odp: drop - No match - - Final flow: unchanged - Datapath actions: drop - -This time the flow we handed to `ofproto/trace` doesn't match any of -our "drop" rules, so it falls through to the low-priority "resubmit" -rule, which we see in the rule and the actions selected in the first -block. The "resubmit" causes a second lookup in OpenFlow table 1, -described by the additional block of indented text in the output. We -haven't yet added any flows to OpenFlow table 1, so no flow actually -matches in the second lookup. Therefore, the packet is still actually -dropped, which means that the externally observable results would be -identical to our first example. - - -Implementing Table 1: VLAN Input Processing -------------------------------------------- - -A packet that enters table 1 has already passed basic validation in -table 0. The purpose of table 1 is validate the packet's VLAN, based -on the VLAN configuration of the switch port through which the packet -entered the switch. We will also use it to attach a VLAN header to -packets that arrive on an access port, which allows later processing -stages to rely on the packet's VLAN always being part of the VLAN -header, reducing special cases. - -Let's start by adding a low-priority flow that drops all packets, -before we add flows that pass through acceptable packets. You can -think of this as a "default drop" rule: - - ovs-ofctl add-flow br0 "table=1, priority=0, actions=drop" - -Our trunk port p1, on OpenFlow port 1, is an easy case. p1 accepts -any packet regardless of whether it has a VLAN header or what the VLAN -was, so we can add a flow that resubmits everything on input port 1 to -the next table: - - ovs-ofctl add-flow br0 \ - "table=1, priority=99, in_port=1, actions=resubmit(,2)" - -On the access ports, we want to accept any packet that has no VLAN -header, tag it with the access port's VLAN number, and then pass it -along to the next stage: - - ovs-ofctl add-flows br0 - <<'EOF' - table=1, priority=99, in_port=2, vlan_tci=0, actions=mod_vlan_vid:20, resubmit(,2) - table=1, priority=99, in_port=3, vlan_tci=0, actions=mod_vlan_vid:30, resubmit(,2) - table=1, priority=99, in_port=4, vlan_tci=0, actions=mod_vlan_vid:30, resubmit(,2) - EOF - -We don't write any rules that match packets with 802.1Q that enter -this stage on any of the access ports, so the "default drop" rule we -added earlier causes them to be dropped, which is ordinarily what we -want for access ports. - -> Another variation of access ports allows ingress of packets tagged -> with VLAN 0 (aka 802.1p priority tagged packets). To allow such -> packets, replace "vlan_tci=0" by "vlan_tci=0/0xfff" above. - - -### Testing Table 1 - -`ofproto/trace` allows us to test the ingress VLAN rules that we added -above. - - -### EXAMPLE 1: Packet on Trunk Port - -Here's a test of a packet coming in on the trunk port: - - ovs-appctl ofproto/trace br0 in_port=1,vlan_tci=5 - -The output shows the lookup in table 0, the resubmit to table 1, and -the resubmit to table 2 (which does nothing because we haven't put -anything there yet): - - Flow: metadata=0,in_port=1,vlan_tci=0x0005,dl_src=00:00:00:00:00:00,dl_dst=00:00:00:00:00:00,dl_type=0x0000 - Rule: table=0 cookie=0 priority=0 - OpenFlow actions=resubmit(,1) - - Resubmitted flow: unchanged - Resubmitted regs: reg0=0x0 reg1=0x0 reg2=0x0 reg3=0x0 reg4=0x0 reg5=0x0 reg6=0x0 reg7=0x0 - Resubmitted odp: drop - Rule: table=1 cookie=0 priority=99,in_port=1 - OpenFlow actions=resubmit(,2) - - Resubmitted flow: unchanged - Resubmitted regs: reg0=0x0 reg1=0x0 reg2=0x0 reg3=0x0 reg4=0x0 reg5=0x0 reg6=0x0 reg7=0x0 - Resubmitted odp: drop - No match - - Final flow: unchanged - Datapath actions: drop - - -### EXAMPLE 2: Valid Packet on Access Port - -Here's a test of a valid packet (a packet without an 802.1Q header) -coming in on access port p2: - - ovs-appctl ofproto/trace br0 in_port=2 - -The output is similar to that for the previous case, except that it -additionally tags the packet with p2's VLAN 20 before it passes it -along to table 2: - - Flow: metadata=0,in_port=2,vlan_tci=0x0000,dl_src=00:00:00:00:00:00,dl_dst=00:00:00:00:00:00,dl_type=0x0000 - Rule: table=0 cookie=0 priority=0 - OpenFlow actions=resubmit(,1) - - Resubmitted flow: unchanged - Resubmitted regs: reg0=0x0 reg1=0x0 reg2=0x0 reg3=0x0 reg4=0x0 reg5=0x0 reg6=0x0 reg7=0x0 - Resubmitted odp: drop - Rule: table=1 cookie=0 priority=99,in_port=2,vlan_tci=0x0000 - OpenFlow actions=mod_vlan_vid:20,resubmit(,2) - - Resubmitted flow: metadata=0,in_port=2,dl_vlan=20,dl_vlan_pcp=0,dl_src=00:00:00:00:00:00,dl_dst=00:00:00:00:00:00,dl_type=0x0000 - Resubmitted regs: reg0=0x0 reg1=0x0 reg2=0x0 reg3=0x0 reg4=0x0 reg5=0x0 reg6=0x0 reg7=0x0 - Resubmitted odp: drop - No match - - Final flow: unchanged - Datapath actions: drop - - -### EXAMPLE 3: Invalid Packet on Access Port - -This tests an invalid packet (one that includes an 802.1Q header) -coming in on access port p2: - - ovs-appctl ofproto/trace br0 in_port=2,vlan_tci=5 - -The output shows the packet matching the default drop rule: - - Flow: metadata=0,in_port=2,vlan_tci=0x0005,dl_src=00:00:00:00:00:00,dl_dst=00:00:00:00:00:00,dl_type=0x0000 - Rule: table=0 cookie=0 priority=0 - OpenFlow actions=resubmit(,1) - - Resubmitted flow: unchanged - Resubmitted regs: reg0=0x0 reg1=0x0 reg2=0x0 reg3=0x0 reg4=0x0 reg5=0x0 reg6=0x0 reg7=0x0 - Resubmitted odp: drop - Rule: table=1 cookie=0 priority=0 - OpenFlow actions=drop - - Final flow: unchanged - Datapath actions: drop - - -Implementing Table 2: MAC+VLAN Learning for Ingress Port --------------------------------------------------------- - -This table allows the switch we're implementing to learn that the -packet's source MAC is located on the packet's ingress port in the -packet's VLAN. - -> This table is a good example why table 1 added a VLAN tag to -> packets that entered the switch through an access port. We want -> to associate a MAC+VLAN with a port regardless of whether the VLAN -> in question was originally part of the packet or whether it was an -> assumed VLAN associated with an access port. - -It only takes a single flow to do this. The following command adds -it: - - ovs-ofctl add-flow br0 \ - "table=2 actions=learn(table=10, NXM_OF_VLAN_TCI[0..11], \ - NXM_OF_ETH_DST[]=NXM_OF_ETH_SRC[], \ - load:NXM_OF_IN_PORT[]->NXM_NX_REG0[0..15]), \ - resubmit(,3)" - -The "learn" action (an Open vSwitch extension to OpenFlow) modifies a -flow table based on the content of the flow currently being processed. -Here's how you can interpret each part of the "learn" action above: - - table=10 - - Modify flow table 10. This will be the MAC learning table. - - NXM_OF_VLAN_TCI[0..11] - - Make the flow that we add to flow table 10 match the same VLAN - ID that the packet we're currently processing contains. This - effectively scopes the MAC learning entry to a single VLAN, - which is the ordinary behavior for a VLAN-aware switch. - - NXM_OF_ETH_DST[]=NXM_OF_ETH_SRC[] - - Make the flow that we add to flow table 10 match, as Ethernet - destination, the Ethernet source address of the packet we're - currently processing. - - load:NXM_OF_IN_PORT[]->NXM_NX_REG0[0..15] - - Whereas the preceding parts specify fields for the new flow to - match, this specifies an action for the flow to take when it - matches. The action is for the flow to load the ingress port - number of the current packet into register 0 (a special field - that is an Open vSwitch extension to OpenFlow). - -> A real use of "learn" for MAC learning would probably involve two -> additional elements. First, the "learn" action would specify a -> hard_timeout for the new flow, to enable a learned MAC to -> eventually expire if no new packets were seen from a given source -> within a reasonable interval. Second, one would usually want to -> limit resource consumption by using the Flow_Table table in the -> Open vSwitch configuration database to specify a maximum number of -> flows in table 10. - -This definitely calls for examples. - - -### Testing Table 2 - -### EXAMPLE 1 - -Try the following test command: - - ovs-appctl ofproto/trace br0 in_port=1,vlan_tci=20,dl_src=50:00:00:00:00:01 -generate - -The output shows that "learn" was executed, but it isn't otherwise -informative, so we won't include it here. - -The `-generate` keyword is new. Ordinarily, `ofproto/trace` has no -side effects: "output" actions do not actually output packets, "learn" -actions do not actually modify the flow table, and so on. With -`-generate`, though, `ofproto/trace` does execute "learn" actions. -That's important now, because we want to see the effect of the "learn" -action on table 10. You can see that by running: - - ovs-ofctl dump-flows br0 table=10 - -which (omitting the "duration" and "idle_age" fields, which will vary -based on how soon you ran this command after the previous one, as well -as some other uninteresting fields) prints something like: - - NXST_FLOW reply (xid=0x4): - table=10, vlan_tci=0x0014/0x0fff,dl_dst=50:00:00:00:00:01 actions=load:0x1->NXM_NX_REG0[0..15] - -You can see that the packet coming in on VLAN 20 with source MAC -50:00:00:00:00:01 became a flow that matches VLAN 20 (written in -hexadecimal) and destination MAC 50:00:00:00:00:01. The flow loads -port number 1, the input port for the flow we tested, into register 0. - - -### EXAMPLE 2 - -Here's a second test command: - - ovs-appctl ofproto/trace br0 in_port=2,dl_src=50:00:00:00:00:01 -generate - -The flow that this command tests has the same source MAC and VLAN as -example 1, although the VLAN comes from an access port VLAN rather -than an 802.1Q header. If we again dump the flows for table 10 with: - - ovs-ofctl dump-flows br0 table=10 - -then we see that the flow we saw previously has changed to indicate -that the learned port is port 2, as we would expect: - - NXST_FLOW reply (xid=0x4): - table=10, vlan_tci=0x0014/0x0fff,dl_dst=50:00:00:00:00:01 actions=load:0x2->NXM_NX_REG0[0..15] - - -Implementing Table 3: Look Up Destination Port ----------------------------------------------- - -This table figures out what port we should send the packet to based on -the destination MAC and VLAN. That is, if we've learned the location -of the destination (from table 2 processing some previous packet with -that destination as its source), then we want to send the packet -there. - -We need only one flow to do the lookup: - - ovs-ofctl add-flow br0 \ - "table=3 priority=50 actions=resubmit(,10), resubmit(,4)" - -The flow's first action resubmits to table 10, the table that the -"learn" action modifies. As you saw previously, the learned flows in -this table write the learned port into register 0. If the destination -for our packet hasn't been learned, then there will be no matching -flow, and so the "resubmit" turns into a no-op. Because registers are -initialized to 0, we can use a register 0 value of 0 in our next -pipeline stage as a signal to flood the packet. - -The second action resubmits to table 4, continuing to the next -pipeline stage. - -We can add another flow to skip the learning table lookup for -multicast and broadcast packets, since those should always be flooded: - - ovs-ofctl add-flow br0 \ - "table=3 priority=99 dl_dst=01:00:00:00:00:00/01:00:00:00:00:00 \ - actions=resubmit(,4)" - -> We don't strictly need to add this flow, because multicast -> addresses will never show up in our learning table. (In turn, -> that's because we put a flow into table 0 to drop packets that -> have a multicast source address.) - - -### Testing Table 3 - -### EXAMPLE - -Here's a command that should cause OVS to learn that f0:00:00:00:00:01 -is on p1 in VLAN 20: - - ovs-appctl ofproto/trace br0 in_port=1,dl_vlan=20,dl_src=f0:00:00:00:00:01,dl_dst=90:00:00:00:00:01 -generate - -Here's an excerpt from the output that shows (from the "no match" -looking up the resubmit to table 10) that the flow's destination was -unknown: - - Resubmitted flow: unchanged - Resubmitted regs: reg0=0x0 reg1=0x0 reg2=0x0 reg3=0x0 reg4=0x0 reg5=0x0 reg6=0x0 reg7=0x0 - Resubmitted odp: drop - Rule: table=3 cookie=0 priority=50 - OpenFlow actions=resubmit(,10),resubmit(,4) - - Resubmitted flow: unchanged - Resubmitted regs: reg0=0x0 reg1=0x0 reg2=0x0 reg3=0x0 reg4=0x0 reg5=0x0 reg6=0x0 reg7=0x0 - Resubmitted odp: drop - No match - -You can verify that the packet's source was learned two ways. The -most direct way is to dump the learning table with: - - ovs-ofctl dump-flows br0 table=10 - -which ought to show roughly the following, with extraneous details -removed: - - table=10, vlan_tci=0x0014/0x0fff,dl_dst=f0:00:00:00:00:01 actions=load:0x1->NXM_NX_REG0[0..15] - -> If you tried the examples for the previous step, or if you did -> some of your own experiments, then you might see additional flows -> there. These additional flows are harmless. If they bother you, -> then you can remove them with `ovs-ofctl del-flows br0 table=10`. - -The other way is to inject a packet to take advantage of the learning -entry. For example, we can inject a packet on p2 whose destination is -the MAC address that we just learned on p1: - - ovs-appctl ofproto/trace br0 in_port=2,dl_src=90:00:00:00:00:01,dl_dst=f0:00:00:00:00:01 -generate - -Here's an interesting excerpt from that command's output. This group -of lines traces the "resubmit(,10)", showing that the packet matched -the learned flow for the first MAC we used, loading the OpenFlow port -number for the learned port p1 into register 0: - - Resubmitted flow: unchanged - Resubmitted regs: reg0=0x0 reg1=0x0 reg2=0x0 reg3=0x0 reg4=0x0 reg5=0x0 reg6=0x0 reg7=0x0 - Resubmitted odp: drop - Rule: table=10 cookie=0 vlan_tci=0x0014/0x0fff,dl_dst=f0:00:00:00:00:01 - OpenFlow actions=load:0x1->NXM_NX_REG0[0..15] - - -If you read the commands above carefully, then you might have noticed -that they simply have the Ethernet source and destination addresses -exchanged. That means that if we now rerun the first `ovs-appctl` -command above, e.g.: - - ovs-appctl ofproto/trace br0 in_port=1,dl_vlan=20,dl_src=f0:00:00:00:00:01,dl_dst=90:00:00:00:00:01 -generate - -then we see in the output that the destination has now been learned: - - Resubmitted flow: unchanged - Resubmitted regs: reg0=0x0 reg1=0x0 reg2=0x0 reg3=0x0 reg4=0x0 reg5=0x0 reg6=0x0 reg7=0x0 - Resubmitted odp: drop - Rule: table=10 cookie=0 vlan_tci=0x0014/0x0fff,dl_dst=90:00:00:00:00:01 - OpenFlow actions=load:0x2->NXM_NX_REG0[0..15] - - -Implementing Table 4: Output Processing ---------------------------------------- - -At entry to stage 4, we know that register 0 contains either the -desired output port or is zero if the packet should be flooded. We -also know that the packet's VLAN is in its 802.1Q header, even if the -VLAN was implicit because the packet came in on an access port. - -The job of the final pipeline stage is to actually output packets. -The job is trivial for output to our trunk port p1: - - ovs-ofctl add-flow br0 "table=4 reg0=1 actions=1" - -For output to the access ports, we just have to strip the VLAN header -before outputting the packet: - - ovs-ofctl add-flows br0 - <<'EOF' - table=4 reg0=2 actions=strip_vlan,2 - table=4 reg0=3 actions=strip_vlan,3 - table=4 reg0=4 actions=strip_vlan,4 - EOF - -The only slightly tricky part is flooding multicast and broadcast -packets and unicast packets with unlearned destinations. For those, -we need to make sure that we only output the packets to the ports that -carry our packet's VLAN, and that we include the 802.1Q header in the -copy output to the trunk port but not in copies output to access -ports: - - ovs-ofctl add-flows br0 - <<'EOF' - table=4 reg0=0 priority=99 dl_vlan=20 actions=1,strip_vlan,2 - table=4 reg0=0 priority=99 dl_vlan=30 actions=1,strip_vlan,3,4 - table=4 reg0=0 priority=50 actions=1 - EOF - -> Our rules rely on the standard OpenFlow behavior that an output -> action will not forward a packet back out the port it came in on. -> That is, if a packet comes in on p1, and we've learned that the -> packet's destination MAC is also on p1, so that we end up with -> "actions=1" as our actions, the switch will not forward the packet -> back out its input port. The multicast/broadcast/unknown -> destination cases above also rely on this behavior. - - -### Testing Table 4 - -### EXAMPLE 1: Broadcast, Multicast, and Unknown Destination - -Try tracing a broadcast packet arriving on p1 in VLAN 30: - - ovs-appctl ofproto/trace br0 in_port=1,dl_dst=ff:ff:ff:ff:ff:ff,dl_vlan=30 - -The interesting part of the output is the final line, which shows that -the switch would remove the 802.1Q header and then output the packet to -p3 and p4, which are access ports for VLAN 30: - - Datapath actions: pop_vlan,3,4 - -Similarly, if we trace a broadcast packet arriving on p3: - - ovs-appctl ofproto/trace br0 in_port=3,dl_dst=ff:ff:ff:ff:ff:ff - -then we see that it is output to p1 with an 802.1Q tag and then to p4 -without one: - - Datapath actions: push_vlan(vid=30,pcp=0),1,pop_vlan,4 - -> Open vSwitch could simplify the datapath actions here to just -> "4,push_vlan(vid=30,pcp=0),1" but it is not smart enough to do so. - -The following are also broadcasts, but the result is to drop the -packets because the VLAN only belongs to the input port: - - ovs-appctl ofproto/trace br0 in_port=1,dl_dst=ff:ff:ff:ff:ff:ff - ovs-appctl ofproto/trace br0 in_port=1,dl_dst=ff:ff:ff:ff:ff:ff,dl_vlan=55 - -Try some other broadcast cases on your own: - - ovs-appctl ofproto/trace br0 in_port=1,dl_dst=ff:ff:ff:ff:ff:ff,dl_vlan=20 - ovs-appctl ofproto/trace br0 in_port=2,dl_dst=ff:ff:ff:ff:ff:ff - ovs-appctl ofproto/trace br0 in_port=4,dl_dst=ff:ff:ff:ff:ff:ff - -You can see the same behavior with multicast packets and with unicast -packets whose destination has not been learned, e.g.: - - ovs-appctl ofproto/trace br0 in_port=4,dl_dst=01:00:00:00:00:00 - ovs-appctl ofproto/trace br0 in_port=1,dl_dst=90:12:34:56:78:90,dl_vlan=20 - ovs-appctl ofproto/trace br0 in_port=1,dl_dst=90:12:34:56:78:90,dl_vlan=30 - - -### EXAMPLE 2: MAC Learning - -Let's follow the same pattern as we did for table 3. First learn a -MAC on port p1 in VLAN 30: - - ovs-appctl ofproto/trace br0 in_port=1,dl_vlan=30,dl_src=10:00:00:00:00:01,dl_dst=20:00:00:00:00:01 -generate - -You can see from the last line of output that the packet's destination -is unknown, so it gets flooded to both p3 and p4, the other ports in -VLAN 30: - - Datapath actions: pop_vlan,3,4 - -Then reverse the MACs and learn the first flow's destination on port -p4: - - ovs-appctl ofproto/trace br0 in_port=4,dl_src=20:00:00:00:00:01,dl_dst=10:00:00:00:00:01 -generate - -The last line of output shows that the this packet's destination is -known to be p1, as learned from our previous command: - - Datapath actions: push_vlan(vid=30,pcp=0),1 - -Now, if we rerun our first command: - - ovs-appctl ofproto/trace br0 in_port=1,dl_vlan=30,dl_src=10:00:00:00:00:01,dl_dst=20:00:00:00:00:01 -generate - -we can see that the result is no longer a flood but to the specified -learned destination port p4: - - Datapath actions: pop_vlan,4 - - -Contact -======= - -bugs@openvswitch.org -http://openvswitch.org/ - -[INSTALL.rst]:../INSTALL.rst |