TesterClient

TesterClient is a synthetic chain-head validation node. It creates deterministic test traffic, sends it into the next node, verifies the deterministic response sequence that comes back, and aborts the process on any mismatch or timeout.

Use it to validate tunnel composition, framing, packet handling, ordering, and payload integrity. It is not a production traffic adapter.

Typical Placement

Stream-mode test:

TesterClient -> SomeTunnel -> SomeTunnel -> TesterServer

Packet-mode test:

TesterClient(packet-mode=true) -> PingClient -> PingServer -> TesterServer(packet-mode=true)

In this direct Ping chain, the normal packet-line Init/Est handshake starts the request flow; packet-start-immediately is not required.

Datagram-sensitive stream test:

TesterClient -> TcpOverUdpClient -> TcpOverUdpServer -> TesterServer

TesterClient must be the chain head. It is also a singleton node type, so a config should contain only one TesterClient instance.

Basic Examples

Stream mode:

{
  "name": "tester-client",
  "type": "TesterClient",
  "next": "next-node"
}

Packet mode:

{
  "name": "tester-client",
  "type": "TesterClient",
  "settings": {
    "packet-mode": true
  },
  "next": "packet-node"
}

Packet mode with synthetic IPv4 packets:

{
  "name": "tester-client",
  "type": "TesterClient",
  "settings": {
    "packet-mode": true,
    "packet-ipv4": {
      "source-ip": "198.51.100.10",
      "dest-ip": "203.0.113.20",
      "transport": "udp",
      "ttl": 64
    }
  },
  "next": "packet-node"
}

Required Fields

Field	Type	Description
name	string	User-chosen node name.
type	string	Must be TesterClient.
next	string	Node that receives the synthetic stream line or packet line.

settings is optional. If omitted, stream-mode defaults are used.

Settings

Field	Default	Description
packet-mode	false	Use worker packet lines instead of normal stream lines.
packet-start-immediately	false	Packet mode only. Start sending without waiting for downstream Est.
packet-start-delay-ms	0	Packet mode only. Delay used by the immediate-start packet path. Must be non-negative.
allow-early-response	false	Stream mode only. Accept downstream response bytes before the full request sequence has been sent.
packet-stateless	false	Packet mode only. Allow response packets to arrive out of order and identify chunks by packet size.
chunk-count	11	Use the first N chunks from the selected chunk table. Valid range is 1 through 11.
max-payload-size	0	Cap generated stream payload buffers or packet sizes. 0 means use the normal table/buffer size.
split-payload-delay-ms	1	Stream mode only. Delay between split payload sends when max-payload-size is active.
split-payload-burst	1	Stream mode only. Number of split buffers sent before applying split-payload-delay-ms. Must be positive.
dest-context	unset	Optional initial destination routing context copied onto each synthetic line before upstream Init.
packet-ipv4	unset	Packet mode only. Wrap each test packet in a synthetic IPv4 packet.

packet-stateless requires packet-mode=true. max-payload-size is not supported with packet-stateless=true.

Chunk Tables

The tester sends deterministic request chunks and expects deterministic response chunks. chunk-count selects a prefix of the active table.

Stream-mode chunk sizes:

1, 2, 4, 32, 512, 1024, 4096, 32768, 32769, 1048576, 2097152

Packet-mode chunk sizes:

1, 2, 4, 32, 64, 128, 256, 512, 1024, 1499, 1500

Packet-mode with raw IPv4 envelope:

21, 22, 24, 52, 84, 148, 276, 532, 1044, 1499, 1500

Packet-mode with IPv4 plus tcp, udp, or icmp transport headers:

41, 42, 44, 52, 84, 148, 276, 532, 1044, 1499, 1500

The byte pattern is deterministic and depends on chunk index, byte offset, flow id, and direction. The first request byte carries the flow id so a real transport hop can remap work to another worker without breaking verification.

Destination Context

dest-context lets tests seed line->routing_context.dest_ctx before upstream Init. This is useful for testing routers, connectors, and packet/UDP adapters that read destination metadata from the line.

{
  "dest-context": {
    "address": "example.com",
    "port": 443,
    "protocol": "tcp"
  }
}

Supported fields:

Field	Description
address	IP address or domain. Domains must fit in the address-context length limit.
port	Destination port, 1 through 65535.
protocol	tcp or udp.

Packet IPv4 Mode

packet-ipv4 is valid only with packet-mode=true. It turns each opaque packet payload into a complete synthetic IPv4 packet.

Required fields:

Field	Description
source-ip	IPv4 source address for request packets.
dest-ip	IPv4 destination address for request packets.

Optional fields:

Field	Default	Description
transport	none	Optional transport header: tcp, udp, icmp, raw, or none.
protocol	253	IPv4 protocol number. If transport is tcp, udp, or icmp, this must match that transport.
ttl	64	IPv4 TTL.

For response packets, source and destination addresses are reversed automatically. For tcp, udp, and icmp, deterministic transport headers are generated and verified. TCP and UDP use source port 40123 and destination port 40234 for requests, reversed for responses.

When packet-ipv4 is enabled, max-payload-size must still leave enough room for the configured IPv4 and transport headers.

Runtime Flow

On startup, TesterClient schedules one task per chain worker after 100 ms. Each worker task:

1. uses the worker packet line in packet mode, or creates a normal stream line otherwise
2. initializes this tunnel's line state
3. optionally copies dest-context into the line
4. sends upstream Init to the next tunnel
5. arms a 30000 ms watchdog

In normal stream mode, the client waits for downstream Est before sending request chunks. In packet mode, packet-start-immediately=true can bypass that wait.

Downstream Pause and Resume pause or resume request sending.

Verification

Stream mode:

• response bytes are buffered until each expected response chunk is complete
• chunks are verified in order
• extra bytes after the expected sequence fail the test
• downstream Finish before full verification fails the test

Packet mode:

• every response packet must match an expected response chunk exactly
• packet lines must stay alive during runtime
• receiving Finish on a packet line is a failure
• with packet-stateless=true, response chunks can arrive out of order, but each expected chunk must arrive exactly once

When every worker completes verification, TesterClient logs success and terminates the program with exit code 0. A mismatch, timeout, invalid lifecycle event, or packet-line death terminates the program with failure.

Node Metadata

Property	Value
Position	Chain head
Singleton	Yes
Normal line owner	Creates normal stream test lines
Packet mode	Uses worker packet lines and must not destroy them
Maximum workers	254
Watchdog	30000 ms per worker
Required left padding	0

Common Mistakes

• Using it in production. It is a validation node and may terminate the process intentionally.
• Forgetting next. TesterClient is a chain head that sends into another node.
• Enabling packet mode without any packet-layer node in the chain.
• Expecting packet mode to close packet lines. Packet lines are persistent worker helper lines.
• Combining packet-stateless=true with max-payload-size.
• Using packet-ipv4 without packet-mode=true.