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diff --git a/docs/gettingstarted/developers/vnet.md b/docs/gettingstarted/developers/vnet.md index 97336a4cdf2..89169efb8d4 100644 --- a/docs/gettingstarted/developers/vnet.md +++ b/docs/gettingstarted/developers/vnet.md @@ -598,3 +598,186 @@ The verbose form displays all of the match rules, with hit-counters. To construct **matches**, add the values to match after the indicated keywords in the mask syntax. For example: "... mask l3 ip4 src" -> "... match l3 ip4 src 192.168.1.11" + +## VPP Packet Generator + +We use the VPP packet generator to inject packets into the forwarding +graph. The packet generator can replay pcap traces, and generate packets +out of whole cloth at respectably high performance. + +The VPP pg enables quite a variety of use-cases, ranging from functional +testing of new data-plane nodes to regression testing to performance +tuning. + +## PG setup scripts + +PG setup scripts describe traffic in detail, and leverage vpp debug +CLI mechanisms. It's reasonably unusual to construct a pg setup script +which doesn't include a certain amount of interface and FIB configuration. + +For example: + +``` + loop create + set int ip address loop0 192.168.1.1/24 + set int state loop0 up + + packet-generator new { + name pg0 + limit 100 + rate 1e6 + size 300-300 + interface loop0 + node ethernet-input + data { IP4: 1.2.3 -> 4.5.6 + UDP: 192.168.1.10 - 192.168.1.254 -> 192.168.2.10 + UDP: 1234 -> 2345 + incrementing 286 + } + } +``` + +A packet generator stream definition includes two major sections: +- Stream Parameter Setup +- Packet Data + +### Stream Parameter Setup + +Given the example above, let's look at how to set up stream +parameters: + +- **name pg0** - Name of the stream, in this case "pg0" + +- **limit 1000** - Number of packets to send when the stream is +enabled. "limit 0" means send packets continuously. + +- **maxframe \<nnn\>** - Maximum frame size. Handy for injecting +multiple frames no larger than \<nnn\>. Useful for checking dual / +quad loop codes + +- **rate 1e6** - Packet injection rate, in this case 1 MPPS. When not +specified, the packet generator injects packets as fast as possible + +- **size 300-300** - Packet size range, in this case send 300-byte packets + +- **interface loop0** - Packets appear as if they were received on the +specified interface. This datum is used in multiple ways: to select +graph arc feature configuration, to select IP FIBs. Configure +features e.g. on loop0 to exercise those features. + +- **tx-interface \<name\>** - Packets will be transmitted on the +indicated interface. Typically required only when injecting packets +into post-IP-rewrite graph nodes. + +- **pcap \<filename\>** - Replay packets from the indicated pcap +capture file. "make test" makes extensive use of this feature: +generate packets using scapy, save them in a .pcap file, then inject +them into the vpp graph via a vpp pg "pcap \<filename\>" stream +definition + +- **worker \<nn\>** - Generate packets for the stream using the +indicated vpp worker thread. The vpp pg generates and injects O(10 +MPPS / core). Use multiple stream definitions and worker threads to +generate and inject enough traffic to easily fill a 40 gbit pipe with +small packets. + +### Data definition + +Packet generator data definitions make use of a layered implementation +strategy. Networking layers are specified in order, and the notation can +seem a bit counter-intuitive. In the example above, the data +definition stanza constructs a set of L2-L4 headers layers, and +uses an incrementing fill pattern to round out the requested 300-byte +packets. + +- **IP4: 1.2.3 -> 4.5.6** - Construct an L2 (MAC) header with the ip4 +ethertype (0x800), src MAC address of 00:01:00:02:00:03 and dst MAC +address of 00:04:00:05:00:06. Mac addresses may be specified in either +_xxxx.xxxx.xxxx_ format or _xx:xx:xx:xx:xx:xx_ format. + +- **UDP: 192.168.1.10 - 192.168.1.254 -> 192.168.2.10** - Construct an +incrementing set of L3 (IPv4) headers for successive packets with +source addresses ranging from .10 to .254. All packets in the stream +have a constant dest address of 192.168.2.10. Set the protocol field +to 17, UDP. + +- **UDP: 1234 -> 2345** - Set the UDP source and destination ports to +1234 and 2345, respectively + +- **incrementing 256** - Insert up to 256 incrementing data bytes. + +Obvious variations involve "s/IP4/IP6/" in the above, along with +changing from IPv4 to IPv6 address notation. + +The vpp pg can set any / all IPv4 header fields, including tos, packet +length, mf / df / fragment id and offset, ttl, protocol, checksum, and +src/dst addresses. Take a look at ../src/vnet/ip/ip[46]_pg.c for +details. + +If all else fails, specify the entire packet data in hex: + +- **hex 0xabcd...** - copy hex data verbatim into the packet + +When replaying pcap files ("**pcap \<filename\>**"), do not specify a +data stanza. + +### Diagnosing "packet-generator new" parse failures + +If you want to inject packets into a brand-new graph node, remember +to tell the packet generator debug CLI how to parse the packet +data stanza. + +If the node expects L2 Ethernet MAC headers, specify ".unformat_buffer += unformat_ethernet_header": + +``` + /* *INDENT-OFF* */ + VLIB_REGISTER_NODE (ethernet_input_node) = + { + <snip> + .unformat_buffer = unformat_ethernet_header, + <snip> + }; +``` + +Beyond that, it may be necessary to set breakpoints in +.../src/vnet/pg/cli.c. Debug image suggested. + +When debugging new nodes, it may be far simpler to directly inject +ethernet frames - and add a corresponding vlib_buffer_advance in the +new node - than to modify the packet generator. + +## Debug CLI + +The descriptions above describe the "packet-generator new" debug CLI in +detail. + +Additional debug CLI commands include: + +``` + vpp# packet-generator enable [<stream-name>] +``` + +which enables the named stream, or all streams. + +``` + vpp# packet-generator disable [<stream-name>] +``` + +disables the named stream, or all streams. + + +``` + vpp# packet-generator delete <stream-name> +``` + +Deletes the named stream. + +``` + vpp# packet-generator configure <stream-name> [limit <nnn>] + [rate <f64-pps>] [size <nn>-<nn>] +``` + +Changes stream parameters without having to recreate the entire stream +definition. Note that re-issuing a "packet-generator new" command will +correctly recreate the named stream. |