Envoy currently provides two experimental extensions that can tap traffic:
Tap transport socket configuration¶
The tap transport socket is experimental and is currently under active development. There is currently a very limited set of match conditions, output configuration, output sinks, etc. Capabilities will be expanded over time and the configuration structures are likely to change.
To configure traffic tapping, add an envoy.transport_sockets.tap transport socket configuration to the listener or cluster. For a plain text socket this might look like:
transport_socket: name: envoy.transport_sockets.tap config: common_config: static_config: match_config: any_match: true output_config: sinks: - format: PROTO_BINARY file_per_tap: path_prefix: /some/tap/path transport_socket: name: envoy.transport_sockets.raw_buffer
For a TLS socket, this will be:
transport_socket: name: envoy.transport_sockets.tap config: common_config: static_config: match_config: any_match: true output_config: sinks: - format: PROTO_BINARY file_per_tap: path_prefix: /some/tap/path transport_socket: name: envoy.transport_sockets.tls config: <TLS context>
Each unique socket instance will generate a trace file prefixed with path_prefix. E.g. /some/tap/path_0.pb.
Buffered data limits¶
For buffered socket taps, Envoy will limit the amount of body data that is tapped to avoid OOM situations. The default limit is 1KiB for both received and transmitted data. This is configurable via the max_buffered_rx_bytes and max_buffered_tx_bytes settings. When a buffered socket tap is truncated, the trace will indicate truncation via the read_truncated and write_truncated fields as well as the body truncated field.
The tap transport socket supports both buffered and streaming, controlled by the streaming setting. When buffering, SocketBufferedTrace messages are emitted. When streaming, a series of SocketStreamedTraceSegment are emitted.
See the HTTP tap filter streaming documentation for more information. Most of the concepts overlap between the HTTP filter and the transport socket.
bazel run @envoy_api//tools:tap2pcap /some/tap/path_0.pb path_0.pcap tshark -r path_0.pcap -d "tcp.port==10000,http2" -P 1 0.000000 127.0.0.1 → 127.0.0.1 HTTP2 157 Magic, SETTINGS, WINDOW_UPDATE, HEADERS 2 0.013713 127.0.0.1 → 127.0.0.1 HTTP2 91 SETTINGS, SETTINGS, WINDOW_UPDATE 3 0.013820 127.0.0.1 → 127.0.0.1 HTTP2 63 SETTINGS 4 0.128649 127.0.0.1 → 127.0.0.1 HTTP2 5586 HEADERS 5 0.130006 127.0.0.1 → 127.0.0.1 HTTP2 7573 DATA 6 0.131044 127.0.0.1 → 127.0.0.1 HTTP2 3152 DATA, DATA