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diff --git a/docs/developer/corearchitecture/vnet.rst b/docs/developer/corearchitecture/vnet.rst new file mode 100644 index 00000000000..812e2fb4f8a --- /dev/null +++ b/docs/developer/corearchitecture/vnet.rst @@ -0,0 +1,807 @@ +VNET (VPP Network Stack) +======================== + +The files associated with the VPP network stack layer are located in the +*./src/vnet* folder. The Network Stack Layer is basically an +instantiation of the code in the other layers. This layer has a vnet +library that provides vectorized layer-2 and 3 networking graph nodes, a +packet generator, and a packet tracer. + +In terms of building a packet processing application, vnet provides a +platform-independent subgraph to which one connects a couple of +device-driver nodes. + +Typical RX connections include “ethernet-input” [full software +classification, feeds ipv4-input, ipv6-input, arp-input etc.] and +“ipv4-input-no-checksum” [if hardware can classify, perform ipv4 header +checksum]. + +Effective graph dispatch function coding +---------------------------------------- + +Over the 15 years, multiple coding styles have emerged: a +single/dual/quad loop coding model (with variations) and a +fully-pipelined coding model. + +Single/dual loops +----------------- + +The single/dual/quad loop model variations conveniently solve problems +where the number of items to process is not known in advance: typical +hardware RX-ring processing. This coding style is also very effective +when a given node will not need to cover a complex set of dependent +reads. + +Here is an quad/single loop which can leverage up-to-avx512 SIMD vector +units to convert buffer indices to buffer pointers: + +.. code:: c + + static uword + simulated_ethernet_interface_tx (vlib_main_t * vm, + vlib_node_runtime_t * + node, vlib_frame_t * frame) + { + u32 n_left_from, *from; + u32 next_index = 0; + u32 n_bytes; + u32 thread_index = vm->thread_index; + vnet_main_t *vnm = vnet_get_main (); + vnet_interface_main_t *im = &vnm->interface_main; + vlib_buffer_t *bufs[VLIB_FRAME_SIZE], **b; + u16 nexts[VLIB_FRAME_SIZE], *next; + + n_left_from = frame->n_vectors; + from = vlib_frame_vector_args (frame); + + /* + * Convert up to VLIB_FRAME_SIZE indices in "from" to + * buffer pointers in bufs[] + */ + vlib_get_buffers (vm, from, bufs, n_left_from); + b = bufs; + next = nexts; + + /* + * While we have at least 4 vector elements (pkts) to process.. + */ + while (n_left_from >= 4) + { + /* Prefetch next quad-loop iteration. */ + if (PREDICT_TRUE (n_left_from >= 8)) + { + vlib_prefetch_buffer_header (b[4], STORE); + vlib_prefetch_buffer_header (b[5], STORE); + vlib_prefetch_buffer_header (b[6], STORE); + vlib_prefetch_buffer_header (b[7], STORE); + } + + /* + * $$$ Process 4x packets right here... + * set next[0..3] to send the packets where they need to go + */ + + do_something_to (b[0]); + do_something_to (b[1]); + do_something_to (b[2]); + do_something_to (b[3]); + + /* Process the next 0..4 packets */ + b += 4; + next += 4; + n_left_from -= 4; + } + /* + * Clean up 0...3 remaining packets at the end of the incoming frame + */ + while (n_left_from > 0) + { + /* + * $$$ Process one packet right here... + * set next[0..3] to send the packets where they need to go + */ + do_something_to (b[0]); + + /* Process the next packet */ + b += 1; + next += 1; + n_left_from -= 1; + } + + /* + * Send the packets along their respective next-node graph arcs + * Considerable locality of reference is expected, most if not all + * packets in the inbound vector will traverse the same next-node + * arc + */ + vlib_buffer_enqueue_to_next (vm, node, from, nexts, frame->n_vectors); + + return frame->n_vectors; + } + +Given a packet processing task to implement, it pays to scout around +looking for similar tasks, and think about using the same coding +pattern. It is not uncommon to recode a given graph node dispatch +function several times during performance optimization. + +Creating Packets from Scratch +----------------------------- + +At times, it’s necessary to create packets from scratch and send them. +Tasks like sending keepalives or actively opening connections come to +mind. Its not difficult, but accurate buffer metadata setup is required. + +Allocating Buffers +~~~~~~~~~~~~~~~~~~ + +Use vlib_buffer_alloc, which allocates a set of buffer indices. For +low-performance applications, it’s OK to allocate one buffer at a time. +Note that vlib_buffer_alloc(…) does NOT initialize buffer metadata. See +below. + +In high-performance cases, allocate a vector of buffer indices, and hand +them out from the end of the vector; decrement \_vec_len(..) as buffer +indices are allocated. See tcp_alloc_tx_buffers(…) and +tcp_get_free_buffer_index(…) for an example. + +Buffer Initialization Example +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The following example shows the **main points**, but is not to be +blindly cut-’n-pasted. + +.. code:: c + + u32 bi0; + vlib_buffer_t *b0; + ip4_header_t *ip; + udp_header_t *udp; + + /* Allocate a buffer */ + if (vlib_buffer_alloc (vm, &bi0, 1) != 1) + return -1; + + b0 = vlib_get_buffer (vm, bi0); + + /* At this point b0->current_data = 0, b0->current_length = 0 */ + + /* + * Copy data into the buffer. This example ASSUMES that data will fit + * in a single buffer, and is e.g. an ip4 packet. + */ + if (have_packet_rewrite) + { + clib_memcpy (b0->data, data, vec_len (data)); + b0->current_length = vec_len (data); + } + else + { + /* OR, build a udp-ip packet (for example) */ + ip = vlib_buffer_get_current (b0); + udp = (udp_header_t *) (ip + 1); + data_dst = (u8 *) (udp + 1); + + ip->ip_version_and_header_length = 0x45; + ip->ttl = 254; + ip->protocol = IP_PROTOCOL_UDP; + ip->length = clib_host_to_net_u16 (sizeof (*ip) + sizeof (*udp) + + vec_len(udp_data)); + ip->src_address.as_u32 = src_address->as_u32; + ip->dst_address.as_u32 = dst_address->as_u32; + udp->src_port = clib_host_to_net_u16 (src_port); + udp->dst_port = clib_host_to_net_u16 (dst_port); + udp->length = clib_host_to_net_u16 (vec_len (udp_data)); + clib_memcpy (data_dst, udp_data, vec_len(udp_data)); + + if (compute_udp_checksum) + { + /* RFC 7011 section 10.3.2. */ + udp->checksum = ip4_tcp_udp_compute_checksum (vm, b0, ip); + if (udp->checksum == 0) + udp->checksum = 0xffff; + } + b0->current_length = vec_len (sizeof (*ip) + sizeof (*udp) + + vec_len (udp_data)); + + } + b0->flags |= VLIB_BUFFER_TOTAL_LENGTH_VALID; + + /* sw_if_index 0 is the "local" interface, which always exists */ + vnet_buffer (b0)->sw_if_index[VLIB_RX] = 0; + + /* Use the default FIB index for tx lookup. Set non-zero to use another fib */ + vnet_buffer (b0)->sw_if_index[VLIB_TX] = 0; + +If your use-case calls for large packet transmission, use +vlib_buffer_chain_append_data_with_alloc(…) to create the requisite +buffer chain. + +Enqueueing packets for lookup and transmission +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The simplest way to send a set of packets is to use +vlib_get_frame_to_node(…) to allocate fresh frame(s) to ip4_lookup_node +or ip6_lookup_node, add the constructed buffer indices, and dispatch the +frame using vlib_put_frame_to_node(…). + +.. code:: c + + vlib_frame_t *f; + f = vlib_get_frame_to_node (vm, ip4_lookup_node.index); + f->n_vectors = vec_len(buffer_indices_to_send); + to_next = vlib_frame_vector_args (f); + + for (i = 0; i < vec_len (buffer_indices_to_send); i++) + to_next[i] = buffer_indices_to_send[i]; + + vlib_put_frame_to_node (vm, ip4_lookup_node_index, f); + +It is inefficient to allocate and schedule single packet frames. That’s +typical in case you need to send one packet per second, but should +**not** occur in a for-loop! + +Packet tracer +------------- + +Vlib includes a frame element [packet] trace facility, with a simple +debug CLI interface. The cli is straightforward: “trace add +input-node-name count” to start capturing packet traces. + +To trace 100 packets on a typical x86_64 system running the dpdk plugin: +“trace add dpdk-input 100”. When using the packet generator: “trace add +pg-input 100” + +To display the packet trace: “show trace” + +Each graph node has the opportunity to capture its own trace data. It is +almost always a good idea to do so. The trace capture APIs are simple. + +The packet capture APIs snapshoot binary data, to minimize processing at +capture time. Each participating graph node initialization provides a +vppinfra format-style user function to pretty-print data when required +by the VLIB “show trace” command. + +Set the VLIB node registration “.format_trace” member to the name of the +per-graph node format function. + +Here’s a simple example: + +.. code:: c + + u8 * my_node_format_trace (u8 * s, va_list * args) + { + vlib_main_t * vm = va_arg (*args, vlib_main_t *); + vlib_node_t * node = va_arg (*args, vlib_node_t *); + my_node_trace_t * t = va_arg (*args, my_trace_t *); + + s = format (s, "My trace data was: %d", t-><whatever>); + + return s; + } + +The trace framework hands the per-node format function the data it +captured as the packet whizzed by. The format function pretty-prints the +data as desired. + +Graph Dispatcher Pcap Tracing +----------------------------- + +The vpp graph dispatcher knows how to capture vectors of packets in pcap +format as they’re dispatched. The pcap captures are as follows: + +:: + + VPP graph dispatch trace record description: + + 0 1 2 3 + 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 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Major Version | Minor Version | NStrings | ProtoHint | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Buffer index (big endian) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + VPP graph node name ... ... | NULL octet | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Buffer Metadata ... ... | NULL octet | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Buffer Opaque ... ... | NULL octet | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Buffer Opaque 2 ... ... | NULL octet | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | VPP ASCII packet trace (if NStrings > 4) | NULL octet | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Packet data (up to 16K) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +Graph dispatch records comprise a version stamp, an indication of how +many NULL-terminated strings will follow the record header and preceed +packet data, and a protocol hint. + +The buffer index is an opaque 32-bit cookie which allows consumers of +these data to easily filter/track single packets as they traverse the +forwarding graph. + +Multiple records per packet are normal, and to be expected. Packets will +appear multiple times as they traverse the vpp forwarding graph. In this +way, vpp graph dispatch traces are significantly different from regular +network packet captures from an end-station. This property complicates +stateful packet analysis. + +Restricting stateful analysis to records from a single vpp graph node +such as “ethernet-input” seems likely to improve the situation. + +As of this writing: major version = 1, minor version = 0. Nstrings +SHOULD be 4 or 5. Consumers SHOULD be wary values less than 4 or greater +than 5. They MAY attempt to display the claimed number of strings, or +they MAY treat the condition as an error. + +Here is the current set of protocol hints: + +.. code:: c + + typedef enum + { + VLIB_NODE_PROTO_HINT_NONE = 0, + VLIB_NODE_PROTO_HINT_ETHERNET, + VLIB_NODE_PROTO_HINT_IP4, + VLIB_NODE_PROTO_HINT_IP6, + VLIB_NODE_PROTO_HINT_TCP, + VLIB_NODE_PROTO_HINT_UDP, + VLIB_NODE_N_PROTO_HINTS, + } vlib_node_proto_hint_t; + +Example: VLIB_NODE_PROTO_HINT_IP6 means that the first octet of packet +data SHOULD be 0x60, and should begin an ipv6 packet header. + +Downstream consumers of these data SHOULD pay attention to the protocol +hint. They MUST tolerate inaccurate hints, which MAY occur from time to +time. + +Dispatch Pcap Trace Debug CLI +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To start a dispatch trace capture of up to 10,000 trace records: + +:: + + pcap dispatch trace on max 10000 file dispatch.pcap + +To start a dispatch trace which will also include standard vpp packet +tracing for packets which originate in dpdk-input: + +:: + + pcap dispatch trace on max 10000 file dispatch.pcap buffer-trace dpdk-input 1000 + +To save the pcap trace, e.g. in /tmp/dispatch.pcap: + +:: + + pcap dispatch trace off + +Wireshark dissection of dispatch pcap traces +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +It almost goes without saying that we built a companion wireshark +dissector to display these traces. As of this writing, we have +upstreamed the wireshark dissector. + +Since it will be a while before wireshark/master/latest makes it into +all of the popular Linux distros, please see the “How to build a vpp +dispatch trace aware Wireshark” page for build info. + +Here is a sample packet dissection, with some fields omitted for +clarity. The point is that the wireshark dissector accurately displays +**all** of the vpp buffer metadata, and the name of the graph node in +question. + +:: + + Frame 1: 2216 bytes on wire (17728 bits), 2216 bytes captured (17728 bits) + Encapsulation type: USER 13 (58) + [Protocols in frame: vpp:vpp-metadata:vpp-opaque:vpp-opaque2:eth:ethertype:ip:tcp:data] + VPP Dispatch Trace + BufferIndex: 0x00036663 + NodeName: ethernet-input + VPP Buffer Metadata + Metadata: flags: + Metadata: current_data: 0, current_length: 102 + Metadata: current_config_index: 0, flow_id: 0, next_buffer: 0 + Metadata: error: 0, n_add_refs: 0, buffer_pool_index: 0 + Metadata: trace_index: 0, recycle_count: 0, len_not_first_buf: 0 + Metadata: free_list_index: 0 + Metadata: + VPP Buffer Opaque + Opaque: raw: 00000007 ffffffff 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 + Opaque: sw_if_index[VLIB_RX]: 7, sw_if_index[VLIB_TX]: -1 + Opaque: L2 offset 0, L3 offset 0, L4 offset 0, feature arc index 0 + Opaque: ip.adj_index[VLIB_RX]: 0, ip.adj_index[VLIB_TX]: 0 + Opaque: ip.flow_hash: 0x0, ip.save_protocol: 0x0, ip.fib_index: 0 + Opaque: ip.save_rewrite_length: 0, ip.rpf_id: 0 + Opaque: ip.icmp.type: 0 ip.icmp.code: 0, ip.icmp.data: 0x0 + Opaque: ip.reass.next_index: 0, ip.reass.estimated_mtu: 0 + Opaque: ip.reass.fragment_first: 0 ip.reass.fragment_last: 0 + Opaque: ip.reass.range_first: 0 ip.reass.range_last: 0 + Opaque: ip.reass.next_range_bi: 0x0, ip.reass.ip6_frag_hdr_offset: 0 + Opaque: mpls.ttl: 0, mpls.exp: 0, mpls.first: 0, mpls.save_rewrite_length: 0, mpls.bier.n_bytes: 0 + Opaque: l2.feature_bitmap: 00000000, l2.bd_index: 0, l2.l2_len: 0, l2.shg: 0, l2.l2fib_sn: 0, l2.bd_age: 0 + Opaque: l2.feature_bitmap_input: none configured, L2.feature_bitmap_output: none configured + Opaque: l2t.next_index: 0, l2t.session_index: 0 + Opaque: l2_classify.table_index: 0, l2_classify.opaque_index: 0, l2_classify.hash: 0x0 + Opaque: policer.index: 0 + Opaque: ipsec.flags: 0x0, ipsec.sad_index: 0 + Opaque: map.mtu: 0 + Opaque: map_t.v6.saddr: 0x0, map_t.v6.daddr: 0x0, map_t.v6.frag_offset: 0, map_t.v6.l4_offset: 0 + Opaque: map_t.v6.l4_protocol: 0, map_t.checksum_offset: 0, map_t.mtu: 0 + Opaque: ip_frag.mtu: 0, ip_frag.next_index: 0, ip_frag.flags: 0x0 + Opaque: cop.current_config_index: 0 + Opaque: lisp.overlay_afi: 0 + 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 + Opaque: tcp.data_len: 0, tcp.flags: 0x0 + Opaque: sctp.connection_index: 0, sctp.sid: 0, sctp.ssn: 0, sctp.tsn: 0, sctp.hdr_offset: 0 + Opaque: sctp.data_offset: 0, sctp.data_len: 0, sctp.subconn_idx: 0, sctp.flags: 0x0 + Opaque: snat.flags: 0x0 + Opaque: + VPP Buffer Opaque2 + Opaque2: raw: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 + Opaque2: qos.bits: 0, qos.source: 0 + Opaque2: loop_counter: 0 + Opaque2: gbp.flags: 0, gbp.src_epg: 0 + Opaque2: pg_replay_timestamp: 0 + Opaque2: + 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 + Source Port: 22432 + Destination Port: 54084 + TCP payload (36 bytes) + Data (36 bytes) + + 0000 cf aa 8b f5 53 14 d4 c7 29 75 3e 56 63 93 9d 11 ....S...)u>Vc... + 0010 e5 f2 92 27 86 56 4c 21 ce c5 23 46 d7 eb ec 0d ...'.VL!..#F.... + 0020 a8 98 36 5a ..6Z + Data: cfaa8bf55314d4c729753e5663939d11e5f2922786564c21… + [Length: 36] + +It’s a matter of a couple of mouse-clicks in Wireshark to filter the +trace to a specific buffer index. With that specific kind of filtration, +one can watch a packet walk through the forwarding graph; noting any/all +metadata changes, header checksum changes, and so forth. + +This should be of significant value when developing new vpp graph nodes. +If new code mispositions b->current_data, it will be completely obvious +from looking at the dispatch trace in wireshark. + +pcap rx, tx, and drop tracing +----------------------------- + +vpp also supports rx, tx, and drop packet capture in pcap format, +through the “pcap trace” debug CLI command. + +This command is used to start or stop a packet capture, or show the +status of packet capture. Each of “pcap trace rx”, “pcap trace tx”, and +“pcap trace drop” is implemented. Supply one or more of “rx”, “tx”, and +“drop” to enable multiple simultaneous capture types. + +These commands have the following optional parameters: + +- rx - trace received packets. + +- tx - trace transmitted packets. + +- drop - trace dropped packets. + +- max *nnnn*\ - file size, number of packet captures. Once packets + have been received, the trace buffer buffer is flushed to the + indicated file. Defaults to 1000. Can only be updated if packet + capture is off. + +- max-bytes-per-pkt *nnnn*\ - maximum number of bytes to trace on a + per-packet basis. Must be >32 and less than 9000. Default value: + + 512. + +- filter - Use the pcap rx / tx / drop trace filter, which must be + configured. Use classify filter pcap… to configure the filter. The + filter will only be executed if the per-interface or any-interface + tests fail. + +- intfc *interface* \| *any*\ - Used to specify a given interface, or + use ‘any’ to run packet capture on all interfaces. ‘any’ is the + default if not provided. Settings from a previous packet capture are + preserved, so ‘any’ can be used to reset the interface setting. + +- file *filename*\ - Used to specify the output filename. The file + will be placed in the ‘/tmp’ directory. If *filename* already exists, + file will be overwritten. If no filename is provided, ‘/tmp/rx.pcap + or tx.pcap’ will be used, depending on capture direction. Can only be + updated when pcap capture is off. + +- status - Displays the current status and configured attributes + associated with a packet capture. If packet capture is in progress, + ‘status’ also will return the number of packets currently in the + buffer. Any additional attributes entered on command line with a + ‘status’ request will be ignored. + +- filter - Capture packets which match the current packet trace filter + set. See next section. Configure the capture filter first. + +packet trace capture filtering +------------------------------ + +The “classify filter pcap \| \| trace” debug CLI command constructs an +arbitrary set of packet classifier tables for use with “pcap rx \| tx \| +drop trace,” and with the vpp packet tracer on a per-interface or +system-wide basis. + +Packets which match a rule in the classifier table chain will be traced. +The tables are automatically ordered so that matches in the most +specific table are tried first. + +It’s reasonably likely that folks will configure a single table with one +or two matches. As a result, we configure 8 hash buckets and 128K of +match rule space by default. One can override the defaults by specifying +“buckets ” and “memory-size ” as desired. + +To build up complex filter chains, repeatedly issue the classify filter +debug CLI command. Each command must specify the desired mask and match +values. If a classifier table with a suitable mask already exists, the +CLI command adds a match rule to the existing table. If not, the CLI +command add a new table and the indicated mask rule + +Configure a simple pcap classify filter +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + classify filter pcap mask l3 ip4 src match l3 ip4 src 192.168.1.11 + pcap trace rx max 100 filter + +Configure a simple per-interface capture filter +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + classify filter GigabitEthernet3/0/0 mask l3 ip4 src match l3 ip4 src 192.168.1.11" + pcap trace rx max 100 intfc GigabitEthernet3/0/0 + +Note that per-interface capture filters are *always* applied. + +Clear per-interface capture filters +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + classify filter GigabitEthernet3/0/0 del + +Configure another fairly simple pcap classify filter +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + classify filter pcap mask l3 ip4 src dst match l3 ip4 src 192.168.1.10 dst 192.168.2.10 + pcap trace tx max 100 filter + +Configure a vpp packet tracer filter +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + classify filter trace mask l3 ip4 src dst match l3 ip4 src 192.168.1.10 dst 192.168.2.10 + trace add dpdk-input 100 filter + +Clear all current classifier filters +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + classify filter [pcap | <interface> | trace] del + +To inspect the classifier tables +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + show classify table [verbose] + +The verbose form displays all of the match rules, with hit-counters. + +Terse description of the “mask ” syntax: +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + l2 src dst proto tag1 tag2 ignore-tag1 ignore-tag2 cos1 cos2 dot1q dot1ad + l3 ip4 <ip4-mask> ip6 <ip6-mask> + <ip4-mask> version hdr_length src[/width] dst[/width] + tos length fragment_id ttl protocol checksum + <ip6-mask> version traffic-class flow-label src dst proto + payload_length hop_limit protocol + l4 tcp <tcp-mask> udp <udp_mask> src_port dst_port + <tcp-mask> src dst # ports + <udp-mask> src_port dst_port + +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”: + +.. code:: c + + 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. |