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| -rw-r--r-- | docs/gettingstarted/developers/vnet.md | 108 |
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diff --git a/docs/gettingstarted/developers/vnet.md b/docs/gettingstarted/developers/vnet.md index 79d539676b9..b8f878c2cd7 100644 --- a/docs/gettingstarted/developers/vnet.md +++ b/docs/gettingstarted/developers/vnet.md @@ -469,3 +469,111 @@ 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 and tx tracing + +vpp also supports rx and tx packet capture in pcap format, through the +"pcap rx trace" and "pcap tx trace" debug CLI commands + +This command is used to start or stop a packet capture, or show +the status of packet capture. Note that both "pcap rx trace" and +"pcap tx trace" are implemented. The command syntax is identical, +simply substitute rx for tx as needed. + +These commands have the following optional parameters: + +on|off- Used to start or stop a packet capture. + +- <b>max _nnnn_</b> - file size, number of packet captures. Once + <nnnn> 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. + +- <b>intfc _interface_ | _any_</b> - Used to specify a given interface, + or use '<em>any</em>' to run packet capture on all interfaces. + '<em>any</em>' is the default if not provided. Settings from a previous + packet capture are preserved, so '<em>any</em>' can be used to reset + the interface setting. + +- <b>file _filename_</b> - Used to specify the output filename. The + file will be placed in the '<em>/tmp</em>' directory. If _filename_ + already exists, file will be overwritten. If no filename is + provided, '<em>/tmp/rx.pcap or tx.pcap</em>' will be used, depending + on capture direction. Can only be updated when pcap capture is off. + +- <b>status</b> - Displays the current status and configured + attributes associated with a packet capture. If packet capture is in + progress, '<em>status</em>' also will return the number of packets + currently in the buffer. Any additional attributes entered on + command line with a '<em>status</em>' request will be ignored. + +- <b>filter</b> - 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" debug CLI command constructs an arbitrary set of + packet classifier tables for use with "pcap rx | tx trace," and + (eventually) with the vpp packet tracer + +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 +specifiying "buckets <nnn>" and "memory-size <xxx>" 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 classify filter + +``` + classify filter mask l3 ip4 src match l3 ip4 src 192.168.1.11" + pcap rx trace on max 100 filter +``` + +### Configure another fairly simple filter + +``` + classify filter mask l3 ip4 src dst match l3 ip4 src 192.168.1.10 dst 192.168.2.10 + pcap tx trace on max 100 filter +``` + +### Clear all current classifier filters + +``` + classify filter 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 <xxx>" 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" |