2 VNET (VPP Network Stack)
3 ========================
5 The files associated with the VPP network stack layer are located in the
6 *./src/vnet* folder. The Network Stack Layer is basically an
7 instantiation of the code in the other layers. This layer has a vnet
8 library that provides vectorized layer-2 and 3 networking graph nodes, a
9 packet generator, and a packet tracer.
11 In terms of building a packet processing application, vnet provides a
12 platform-independent subgraph to which one connects a couple of
15 Typical RX connections include "ethernet-input" \[full software
16 classification, feeds ipv4-input, ipv6-input, arp-input etc.\] and
17 "ipv4-input-no-checksum" \[if hardware can classify, perform ipv4 header
20 Effective graph dispatch function coding
21 ----------------------------------------
23 Over the 15 years, multiple coding styles have emerged: a
24 single/dual/quad loop coding model (with variations) and a
25 fully-pipelined coding model.
30 The single/dual/quad loop model variations conveniently solve problems
31 where the number of items to process is not known in advance: typical
32 hardware RX-ring processing. This coding style is also very effective
33 when a given node will not need to cover a complex set of dependent
36 Here is an quad/single loop which can leverage up-to-avx512 SIMD vector
37 units to convert buffer indices to buffer pointers:
41 simulated_ethernet_interface_tx (vlib_main_t * vm,
43 node, vlib_frame_t * frame)
45 u32 n_left_from, *from;
48 u32 thread_index = vm->thread_index;
49 vnet_main_t *vnm = vnet_get_main ();
50 vnet_interface_main_t *im = &vnm->interface_main;
51 vlib_buffer_t *bufs[VLIB_FRAME_SIZE], **b;
52 u16 nexts[VLIB_FRAME_SIZE], *next;
54 n_left_from = frame->n_vectors;
55 from = vlib_frame_vector_args (frame);
58 * Convert up to VLIB_FRAME_SIZE indices in "from" to
59 * buffer pointers in bufs[]
61 vlib_get_buffers (vm, from, bufs, n_left_from);
66 * While we have at least 4 vector elements (pkts) to process..
68 while (n_left_from >= 4)
70 /* Prefetch next quad-loop iteration. */
71 if (PREDICT_TRUE (n_left_from >= 8))
73 vlib_prefetch_buffer_header (b[4], STORE);
74 vlib_prefetch_buffer_header (b[5], STORE);
75 vlib_prefetch_buffer_header (b[6], STORE);
76 vlib_prefetch_buffer_header (b[7], STORE);
80 * $$$ Process 4x packets right here...
81 * set next[0..3] to send the packets where they need to go
84 do_something_to (b[0]);
85 do_something_to (b[1]);
86 do_something_to (b[2]);
87 do_something_to (b[3]);
89 /* Process the next 0..4 packets */
95 * Clean up 0...3 remaining packets at the end of the incoming frame
97 while (n_left_from > 0)
100 * $$$ Process one packet right here...
101 * set next[0..3] to send the packets where they need to go
103 do_something_to (b[0]);
105 /* Process the next packet */
112 * Send the packets along their respective next-node graph arcs
113 * Considerable locality of reference is expected, most if not all
114 * packets in the inbound vector will traverse the same next-node
117 vlib_buffer_enqueue_to_next (vm, node, from, nexts, frame->n_vectors);
119 return frame->n_vectors;
123 Given a packet processing task to implement, it pays to scout around
124 looking for similar tasks, and think about using the same coding
125 pattern. It is not uncommon to recode a given graph node dispatch function
126 several times during performance optimization.
128 Creating Packets from Scratch
129 -----------------------------
131 At times, it's necessary to create packets from scratch and send
132 them. Tasks like sending keepalives or actively opening connections
133 come to mind. Its not difficult, but accurate buffer metadata setup is
136 ### Allocating Buffers
138 Use vlib_buffer_alloc, which allocates a set of buffer indices. For
139 low-performance applications, it's OK to allocate one buffer at a
140 time. Note that vlib_buffer_alloc(...) does NOT initialize buffer
143 In high-performance cases, allocate a vector of buffer indices,
144 and hand them out from the end of the vector; decrement _vec_len(..)
145 as buffer indices are allocated. See tcp_alloc_tx_buffers(...) and
146 tcp_get_free_buffer_index(...) for an example.
148 ### Buffer Initialization Example
150 The following example shows the **main points**, but is not to be
151 blindly cut-'n-pasted.
159 /* Allocate a buffer */
160 if (vlib_buffer_alloc (vm, &bi0, 1) != 1)
163 b0 = vlib_get_buffer (vm, bi0);
165 /* At this point b0->current_data = 0, b0->current_length = 0 */
168 * Copy data into the buffer. This example ASSUMES that data will fit
169 * in a single buffer, and is e.g. an ip4 packet.
171 if (have_packet_rewrite)
173 clib_memcpy (b0->data, data, vec_len (data));
174 b0->current_length = vec_len (data);
178 /* OR, build a udp-ip packet (for example) */
179 ip = vlib_buffer_get_current (b0);
180 udp = (udp_header_t *) (ip + 1);
181 data_dst = (u8 *) (udp + 1);
183 ip->ip_version_and_header_length = 0x45;
185 ip->protocol = IP_PROTOCOL_UDP;
186 ip->length = clib_host_to_net_u16 (sizeof (*ip) + sizeof (*udp) +
188 ip->src_address.as_u32 = src_address->as_u32;
189 ip->dst_address.as_u32 = dst_address->as_u32;
190 udp->src_port = clib_host_to_net_u16 (src_port);
191 udp->dst_port = clib_host_to_net_u16 (dst_port);
192 udp->length = clib_host_to_net_u16 (vec_len (udp_data));
193 clib_memcpy (data_dst, udp_data, vec_len(udp_data));
195 if (compute_udp_checksum)
197 /* RFC 7011 section 10.3.2. */
198 udp->checksum = ip4_tcp_udp_compute_checksum (vm, b0, ip);
199 if (udp->checksum == 0)
200 udp->checksum = 0xffff;
202 b0->current_length = vec_len (sizeof (*ip) + sizeof (*udp) +
206 b0->flags |= VLIB_BUFFER_TOTAL_LENGTH_VALID;
208 /* sw_if_index 0 is the "local" interface, which always exists */
209 vnet_buffer (b0)->sw_if_index[VLIB_RX] = 0;
211 /* Use the default FIB index for tx lookup. Set non-zero to use another fib */
212 vnet_buffer (b0)->sw_if_index[VLIB_TX] = 0;
216 If your use-case calls for large packet transmission, use
217 vlib_buffer_chain_append_data_with_alloc(...) to create the requisite
220 ### Enqueueing packets for lookup and transmission
222 The simplest way to send a set of packets is to use
223 vlib_get_frame_to_node(...) to allocate fresh frame(s) to
224 ip4_lookup_node or ip6_lookup_node, add the constructed buffer
225 indices, and dispatch the frame using vlib_put_frame_to_node(...).
229 f = vlib_get_frame_to_node (vm, ip4_lookup_node.index);
230 f->n_vectors = vec_len(buffer_indices_to_send);
231 to_next = vlib_frame_vector_args (f);
233 for (i = 0; i < vec_len (buffer_indices_to_send); i++)
234 to_next[i] = buffer_indices_to_send[i];
236 vlib_put_frame_to_node (vm, ip4_lookup_node_index, f);
239 It is inefficient to allocate and schedule single packet frames.
240 That's typical in case you need to send one packet per second, but
241 should **not** occur in a for-loop!
246 Vlib includes a frame element \[packet\] trace facility, with a simple
247 debug CLI interface. The cli is straightforward: "trace add
248 input-node-name count" to start capturing packet traces.
250 To trace 100 packets on a typical x86\_64 system running the dpdk
251 plugin: "trace add dpdk-input 100". When using the packet generator:
252 "trace add pg-input 100"
254 To display the packet trace: "show trace"
256 Each graph node has the opportunity to capture its own trace data. It is
257 almost always a good idea to do so. The trace capture APIs are simple.
259 The packet capture APIs snapshoot binary data, to minimize processing at
260 capture time. Each participating graph node initialization provides a
261 vppinfra format-style user function to pretty-print data when required
262 by the VLIB "show trace" command.
264 Set the VLIB node registration ".format\_trace" member to the name of
265 the per-graph node format function.
267 Here's a simple example:
270 u8 * my_node_format_trace (u8 * s, va_list * args)
272 vlib_main_t * vm = va_arg (*args, vlib_main_t *);
273 vlib_node_t * node = va_arg (*args, vlib_node_t *);
274 my_node_trace_t * t = va_arg (*args, my_trace_t *);
276 s = format (s, "My trace data was: %d", t-><whatever>);
282 The trace framework hands the per-node format function the data it
283 captured as the packet whizzed by. The format function pretty-prints the
286 Graph Dispatcher Pcap Tracing
287 -----------------------------
289 The vpp graph dispatcher knows how to capture vectors of packets in pcap
290 format as they're dispatched. The pcap captures are as follows:
293 VPP graph dispatch trace record description:
296 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
297 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
298 | Major Version | Minor Version | NStrings | ProtoHint |
299 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
300 | Buffer index (big endian) |
301 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
302 + VPP graph node name ... ... | NULL octet |
303 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
304 | Buffer Metadata ... ... | NULL octet |
305 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
306 | Buffer Opaque ... ... | NULL octet |
307 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
308 | Buffer Opaque 2 ... ... | NULL octet |
309 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
310 | VPP ASCII packet trace (if NStrings > 4) | NULL octet |
311 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
312 | Packet data (up to 16K) |
313 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
316 Graph dispatch records comprise a version stamp, an indication of how
317 many NULL-terminated strings will follow the record header and preceed
318 packet data, and a protocol hint.
320 The buffer index is an opaque 32-bit cookie which allows consumers of
321 these data to easily filter/track single packets as they traverse the
324 Multiple records per packet are normal, and to be expected. Packets
325 will appear multiple times as they traverse the vpp forwarding
326 graph. In this way, vpp graph dispatch traces are significantly
327 different from regular network packet captures from an end-station.
328 This property complicates stateful packet analysis.
330 Restricting stateful analysis to records from a single vpp graph node
331 such as "ethernet-input" seems likely to improve the situation.
333 As of this writing: major version = 1, minor version = 0. Nstrings
334 SHOULD be 4 or 5. Consumers SHOULD be wary values less than 4 or
335 greater than 5. They MAY attempt to display the claimed number of
336 strings, or they MAY treat the condition as an error.
338 Here is the current set of protocol hints:
343 VLIB_NODE_PROTO_HINT_NONE = 0,
344 VLIB_NODE_PROTO_HINT_ETHERNET,
345 VLIB_NODE_PROTO_HINT_IP4,
346 VLIB_NODE_PROTO_HINT_IP6,
347 VLIB_NODE_PROTO_HINT_TCP,
348 VLIB_NODE_PROTO_HINT_UDP,
349 VLIB_NODE_N_PROTO_HINTS,
350 } vlib_node_proto_hint_t;
353 Example: VLIB_NODE_PROTO_HINT_IP6 means that the first octet of packet
354 data SHOULD be 0x60, and should begin an ipv6 packet header.
356 Downstream consumers of these data SHOULD pay attention to the
357 protocol hint. They MUST tolerate inaccurate hints, which MAY occur
360 ### Dispatch Pcap Trace Debug CLI
362 To start a dispatch trace capture of up to 10,000 trace records:
365 pcap dispatch trace on max 10000 file dispatch.pcap
368 To start a dispatch trace which will also include standard vpp packet
369 tracing for packets which originate in dpdk-input:
372 pcap dispatch trace on max 10000 file dispatch.pcap buffer-trace dpdk-input 1000
374 To save the pcap trace, e.g. in /tmp/dispatch.pcap:
377 pcap dispatch trace off
380 ### Wireshark dissection of dispatch pcap traces
382 It almost goes without saying that we built a companion wireshark
383 dissector to display these traces. As of this writing, we have
384 upstreamed the wireshark dissector.
386 Since it will be a while before wireshark/master/latest makes it into
387 all of the popular Linux distros, please see the "How to build a vpp
388 dispatch trace aware Wireshark" page for build info.
390 Here is a sample packet dissection, with some fields omitted for
391 clarity. The point is that the wireshark dissector accurately
392 displays **all** of the vpp buffer metadata, and the name of the graph
396 Frame 1: 2216 bytes on wire (17728 bits), 2216 bytes captured (17728 bits)
397 Encapsulation type: USER 13 (58)
398 [Protocols in frame: vpp:vpp-metadata:vpp-opaque:vpp-opaque2:eth:ethertype:ip:tcp:data]
400 BufferIndex: 0x00036663
401 NodeName: ethernet-input
404 Metadata: current_data: 0, current_length: 102
405 Metadata: current_config_index: 0, flow_id: 0, next_buffer: 0
406 Metadata: error: 0, n_add_refs: 0, buffer_pool_index: 0
407 Metadata: trace_index: 0, recycle_count: 0, len_not_first_buf: 0
408 Metadata: free_list_index: 0
411 Opaque: raw: 00000007 ffffffff 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
412 Opaque: sw_if_index[VLIB_RX]: 7, sw_if_index[VLIB_TX]: -1
413 Opaque: L2 offset 0, L3 offset 0, L4 offset 0, feature arc index 0
414 Opaque: ip.adj_index[VLIB_RX]: 0, ip.adj_index[VLIB_TX]: 0
415 Opaque: ip.flow_hash: 0x0, ip.save_protocol: 0x0, ip.fib_index: 0
416 Opaque: ip.save_rewrite_length: 0, ip.rpf_id: 0
417 Opaque: ip.icmp.type: 0 ip.icmp.code: 0, ip.icmp.data: 0x0
418 Opaque: ip.reass.next_index: 0, ip.reass.estimated_mtu: 0
419 Opaque: ip.reass.fragment_first: 0 ip.reass.fragment_last: 0
420 Opaque: ip.reass.range_first: 0 ip.reass.range_last: 0
421 Opaque: ip.reass.next_range_bi: 0x0, ip.reass.ip6_frag_hdr_offset: 0
422 Opaque: mpls.ttl: 0, mpls.exp: 0, mpls.first: 0, mpls.save_rewrite_length: 0, mpls.bier.n_bytes: 0
423 Opaque: l2.feature_bitmap: 00000000, l2.bd_index: 0, l2.l2_len: 0, l2.shg: 0, l2.l2fib_sn: 0, l2.bd_age: 0
424 Opaque: l2.feature_bitmap_input: none configured, L2.feature_bitmap_output: none configured
425 Opaque: l2t.next_index: 0, l2t.session_index: 0
426 Opaque: l2_classify.table_index: 0, l2_classify.opaque_index: 0, l2_classify.hash: 0x0
427 Opaque: policer.index: 0
428 Opaque: ipsec.flags: 0x0, ipsec.sad_index: 0
430 Opaque: map_t.v6.saddr: 0x0, map_t.v6.daddr: 0x0, map_t.v6.frag_offset: 0, map_t.v6.l4_offset: 0
431 Opaque: map_t.v6.l4_protocol: 0, map_t.checksum_offset: 0, map_t.mtu: 0
432 Opaque: ip_frag.mtu: 0, ip_frag.next_index: 0, ip_frag.flags: 0x0
433 Opaque: cop.current_config_index: 0
434 Opaque: lisp.overlay_afi: 0
435 Opaque: tcp.connection_index: 0, tcp.seq_number: 0, tcp.seq_end: 0, tcp.ack_number: 0, tcp.hdr_offset: 0, tcp.data_offset: 0
436 Opaque: tcp.data_len: 0, tcp.flags: 0x0
437 Opaque: sctp.connection_index: 0, sctp.sid: 0, sctp.ssn: 0, sctp.tsn: 0, sctp.hdr_offset: 0
438 Opaque: sctp.data_offset: 0, sctp.data_len: 0, sctp.subconn_idx: 0, sctp.flags: 0x0
439 Opaque: snat.flags: 0x0
442 Opaque2: raw: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
443 Opaque2: qos.bits: 0, qos.source: 0
444 Opaque2: loop_counter: 0
445 Opaque2: gbp.flags: 0, gbp.src_epg: 0
446 Opaque2: pg_replay_timestamp: 0
448 Ethernet II, Src: 06:d6:01:41:3b:92 (06:d6:01:41:3b:92), Dst: IntelCor_3d:f6 Transmission Control Protocol, Src Port: 22432, Dst Port: 54084, Seq: 1, Ack: 1, Len: 36
450 Destination Port: 54084
451 TCP payload (36 bytes)
454 0000 cf aa 8b f5 53 14 d4 c7 29 75 3e 56 63 93 9d 11 ....S...)u>Vc...
455 0010 e5 f2 92 27 86 56 4c 21 ce c5 23 46 d7 eb ec 0d ...'.VL!..#F....
456 0020 a8 98 36 5a ..6Z
457 Data: cfaa8bf55314d4c729753e5663939d11e5f2922786564c21…
461 It's a matter of a couple of mouse-clicks in Wireshark to filter the
462 trace to a specific buffer index. With that specific kind of filtration,
463 one can watch a packet walk through the forwarding graph; noting any/all
464 metadata changes, header checksum changes, and so forth.
466 This should be of significant value when developing new vpp graph
467 nodes. If new code mispositions b->current_data, it will be completely
468 obvious from looking at the dispatch trace in wireshark.
470 ## pcap rx, tx, and drop tracing
472 vpp also supports rx, tx, and drop packet capture in pcap format,
473 through the "pcap trace" debug CLI command.
475 This command is used to start or stop a packet capture, or show the
476 status of packet capture. Each of "pcap trace rx", "pcap trace tx",
477 and "pcap trace drop" is implemented. Supply one or more of "rx",
478 "tx", and "drop" to enable multiple simultaneous capture types.
480 These commands have the following optional parameters:
482 - <b>rx</b> - trace received packets.
484 - <b>tx</b> - trace transmitted packets.
486 - <b>drop</b> - trace dropped packets.
488 - <b>max _nnnn_</b> - file size, number of packet captures. Once
489 <nnnn> packets have been received, the trace buffer buffer is flushed
490 to the indicated file. Defaults to 1000. Can only be updated if packet
493 - <b>max-bytes-per-pkt _nnnn_</b> - maximum number of bytes to trace
494 on a per-packet basis. Must be >32 and less than 9000. Default value:
497 - <b>filter</b> - Use the pcap rx / tx / drop trace filter, which must
498 be configured. Use <b>classify filter pcap...</b> to configure the
499 filter. The filter will only be executed if the per-interface or
500 any-interface tests fail.
502 - <b>intfc _interface_ | _any_</b> - Used to specify a given interface,
503 or use '<em>any</em>' to run packet capture on all interfaces.
504 '<em>any</em>' is the default if not provided. Settings from a previous
505 packet capture are preserved, so '<em>any</em>' can be used to reset
506 the interface setting.
508 - <b>file _filename_</b> - Used to specify the output filename. The
509 file will be placed in the '<em>/tmp</em>' directory. If _filename_
510 already exists, file will be overwritten. If no filename is
511 provided, '<em>/tmp/rx.pcap or tx.pcap</em>' will be used, depending
512 on capture direction. Can only be updated when pcap capture is off.
514 - <b>status</b> - Displays the current status and configured
515 attributes associated with a packet capture. If packet capture is in
516 progress, '<em>status</em>' also will return the number of packets
517 currently in the buffer. Any additional attributes entered on
518 command line with a '<em>status</em>' request will be ignored.
520 - <b>filter</b> - Capture packets which match the current packet
521 trace filter set. See next section. Configure the capture filter
524 ## packet trace capture filtering
526 The "classify filter pcap | <interface-name> | trace" debug CLI command
527 constructs an arbitrary set of packet classifier tables for use with
528 "pcap rx | tx | drop trace," and with the vpp packet tracer on a
529 per-interface or system-wide basis.
531 Packets which match a rule in the classifier table chain will be
532 traced. The tables are automatically ordered so that matches in the
533 most specific table are tried first.
535 It's reasonably likely that folks will configure a single table with
536 one or two matches. As a result, we configure 8 hash buckets and 128K
537 of match rule space by default. One can override the defaults by
538 specifying "buckets <nnn>" and "memory-size <xxx>" as desired.
540 To build up complex filter chains, repeatedly issue the classify
541 filter debug CLI command. Each command must specify the desired mask
542 and match values. If a classifier table with a suitable mask already
543 exists, the CLI command adds a match rule to the existing table. If
544 not, the CLI command add a new table and the indicated mask rule
546 ### Configure a simple pcap classify filter
549 classify filter pcap mask l3 ip4 src match l3 ip4 src 192.168.1.11
550 pcap trace rx max 100 filter
553 ### Configure a simple per-interface capture filter
556 classify filter GigabitEthernet3/0/0 mask l3 ip4 src match l3 ip4 src 192.168.1.11"
557 pcap trace rx max 100 intfc GigabitEthernet3/0/0
560 Note that per-interface capture filters are _always_ applied.
562 ### Clear per-interface capture filters
565 classify filter GigabitEthernet3/0/0 del
568 ### Configure another fairly simple pcap classify filter
571 classify filter pcap mask l3 ip4 src dst match l3 ip4 src 192.168.1.10 dst 192.168.2.10
572 pcap trace tx max 100 filter
575 ### Configure a vpp packet tracer filter
578 classify filter trace mask l3 ip4 src dst match l3 ip4 src 192.168.1.10 dst 192.168.2.10
579 trace add dpdk-input 100 filter
582 ### Clear all current classifier filters
585 classify filter [pcap | <interface> | trace] del
588 ### To inspect the classifier tables
591 show classify table [verbose]
594 The verbose form displays all of the match rules, with hit-counters.
596 ### Terse description of the "mask <xxx>" syntax:
599 l2 src dst proto tag1 tag2 ignore-tag1 ignore-tag2 cos1 cos2 dot1q dot1ad
600 l3 ip4 <ip4-mask> ip6 <ip6-mask>
601 <ip4-mask> version hdr_length src[/width] dst[/width]
602 tos length fragment_id ttl protocol checksum
603 <ip6-mask> version traffic-class flow-label src dst proto
604 payload_length hop_limit protocol
605 l4 tcp <tcp-mask> udp <udp_mask> src_port dst_port
606 <tcp-mask> src dst # ports
607 <udp-mask> src_port dst_port
610 To construct **matches**, add the values to match after the indicated
611 keywords in the mask syntax. For example: "... mask l3 ip4 src" ->
612 "... match l3 ip4 src 192.168.1.11"
614 ## VPP Packet Generator
616 We use the VPP packet generator to inject packets into the forwarding
617 graph. The packet generator can replay pcap traces, and generate packets
618 out of whole cloth at respectably high performance.
620 The VPP pg enables quite a variety of use-cases, ranging from functional
621 testing of new data-plane nodes to regression testing to performance
626 PG setup scripts describe traffic in detail, and leverage vpp debug
627 CLI mechanisms. It's reasonably unusual to construct a pg setup script
628 which doesn't include a certain amount of interface and FIB configuration.
634 set int ip address loop0 192.168.1.1/24
635 set int state loop0 up
637 packet-generator new {
644 data { IP4: 1.2.3 -> 4.5.6
645 UDP: 192.168.1.10 - 192.168.1.254 -> 192.168.2.10
652 A packet generator stream definition includes two major sections:
653 - Stream Parameter Setup
656 ### Stream Parameter Setup
658 Given the example above, let's look at how to set up stream
661 - **name pg0** - Name of the stream, in this case "pg0"
663 - **limit 1000** - Number of packets to send when the stream is
664 enabled. "limit 0" means send packets continuously.
666 - **maxframe \<nnn\>** - Maximum frame size. Handy for injecting
667 multiple frames no larger than \<nnn\>. Useful for checking dual /
670 - **rate 1e6** - Packet injection rate, in this case 1 MPPS. When not
671 specified, the packet generator injects packets as fast as possible
673 - **size 300-300** - Packet size range, in this case send 300-byte packets
675 - **interface loop0** - Packets appear as if they were received on the
676 specified interface. This datum is used in multiple ways: to select
677 graph arc feature configuration, to select IP FIBs. Configure
678 features e.g. on loop0 to exercise those features.
680 - **tx-interface \<name\>** - Packets will be transmitted on the
681 indicated interface. Typically required only when injecting packets
682 into post-IP-rewrite graph nodes.
684 - **pcap \<filename\>** - Replay packets from the indicated pcap
685 capture file. "make test" makes extensive use of this feature:
686 generate packets using scapy, save them in a .pcap file, then inject
687 them into the vpp graph via a vpp pg "pcap \<filename\>" stream
690 - **worker \<nn\>** - Generate packets for the stream using the
691 indicated vpp worker thread. The vpp pg generates and injects O(10
692 MPPS / core). Use multiple stream definitions and worker threads to
693 generate and inject enough traffic to easily fill a 40 gbit pipe with
698 Packet generator data definitions make use of a layered implementation
699 strategy. Networking layers are specified in order, and the notation can
700 seem a bit counter-intuitive. In the example above, the data
701 definition stanza constructs a set of L2-L4 headers layers, and
702 uses an incrementing fill pattern to round out the requested 300-byte
705 - **IP4: 1.2.3 -> 4.5.6** - Construct an L2 (MAC) header with the ip4
706 ethertype (0x800), src MAC address of 00:01:00:02:00:03 and dst MAC
707 address of 00:04:00:05:00:06. Mac addresses may be specified in either
708 _xxxx.xxxx.xxxx_ format or _xx:xx:xx:xx:xx:xx_ format.
710 - **UDP: 192.168.1.10 - 192.168.1.254 -> 192.168.2.10** - Construct an
711 incrementing set of L3 (IPv4) headers for successive packets with
712 source addresses ranging from .10 to .254. All packets in the stream
713 have a constant dest address of 192.168.2.10. Set the protocol field
716 - **UDP: 1234 -> 2345** - Set the UDP source and destination ports to
717 1234 and 2345, respectively
719 - **incrementing 256** - Insert up to 256 incrementing data bytes.
721 Obvious variations involve "s/IP4/IP6/" in the above, along with
722 changing from IPv4 to IPv6 address notation.
724 The vpp pg can set any / all IPv4 header fields, including tos, packet
725 length, mf / df / fragment id and offset, ttl, protocol, checksum, and
726 src/dst addresses. Take a look at ../src/vnet/ip/ip[46]_pg.c for
729 If all else fails, specify the entire packet data in hex:
731 - **hex 0xabcd...** - copy hex data verbatim into the packet
733 When replaying pcap files ("**pcap \<filename\>**"), do not specify a
736 ### Diagnosing "packet-generator new" parse failures
738 If you want to inject packets into a brand-new graph node, remember
739 to tell the packet generator debug CLI how to parse the packet
742 If the node expects L2 Ethernet MAC headers, specify ".unformat_buffer
743 = unformat_ethernet_header":
747 VLIB_REGISTER_NODE (ethernet_input_node) =
750 .unformat_buffer = unformat_ethernet_header,
755 Beyond that, it may be necessary to set breakpoints in
756 .../src/vnet/pg/cli.c. Debug image suggested.
758 When debugging new nodes, it may be far simpler to directly inject
759 ethernet frames - and add a corresponding vlib_buffer_advance in the
760 new node - than to modify the packet generator.
764 The descriptions above describe the "packet-generator new" debug CLI in
767 Additional debug CLI commands include:
770 vpp# packet-generator enable [<stream-name>]
773 which enables the named stream, or all streams.
776 vpp# packet-generator disable [<stream-name>]
779 disables the named stream, or all streams.
783 vpp# packet-generator delete <stream-name>
786 Deletes the named stream.
789 vpp# packet-generator configure <stream-name> [limit <nnn>]
790 [rate <f64-pps>] [size <nn>-<nn>]
793 Changes stream parameters without having to recreate the entire stream
794 definition. Note that re-issuing a "packet-generator new" command will
795 correctly recreate the named stream.