CLI / Env / YAML

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Every flag has an environment variable (CPE_SIM_*) and a YAML key. Precedence is flag > env > file > defaults.

The CLI is parsed by internal/cpeconfig. Unknown flags, unknown YAML keys, and unknown CPE_SIM_* env vars all reject at startup so typos surface loudly instead of silently no-op'ing.

Required

Flag Env YAML Notes
--profile CPE_SIM_PROFILE profile Path to a YAML/JSON profile file or directory of YAML files. No built-in fallback; the simulator is vendor-neutral and will not assume a data model.
--acs-url CPE_SIM_ACS_URL acsURL The ACS's CWMP endpoint. Required for TR-069 mode.

For TR-369 (USP) mode, --acs-url may be omitted as long as --usp-mtp is set; see USP Agent.

ACS / TR-069

Flag Env YAML Default Notes
--acs-url CPE_SIM_ACS_URL acsURL (required for CWMP) Outbound CWMP endpoint URL.
--acs-username CPE_SIM_ACS_USERNAME acsUsername "" HTTP Basic / Digest auth username.
--acs-password CPE_SIM_ACS_PASSWORD acsPassword "" HTTP Basic / Digest auth password.
--acs-timeout CPE_SIM_ACS_TIMEOUT acsTimeout 30s Per-request timeout. Go duration syntax (30s, 1m, …).
--tls-skip-verify CPE_SIM_TLS_SKIP_VERIFY tlsSkipVerify false Disable TLS verification for outbound HTTPS. Insecure.
--ca-cert-file CPE_SIM_CA_CERT_FILE caCertFile "" PEM-encoded CA bundle for TLS verification.

Connection Request listener (TR-069)

Flag Env YAML Default Notes
--cr-bind-addr CPE_SIM_CR_BIND_ADDR crBindAddr "" TCP bind address for the CR listener. Empty disables the listener. Setting it enables daemon mode.
--cr-path CPE_SIM_CR_PATH crPath /cr URL path the listener serves. With fleet.count > 1, each CPE gets /<cr-path>/<cpe-id>.
--cr-publish-path CPE_SIM_CR_PUBLISH_PATH crPublishPath (required when --cr-bind-addr is set) Tree path the listener URL is written to.

See Connection Request Listener for a deeper treatment.

Process / runtime

Flag Env YAML Default Notes
--seed CPE_SIM_SEED seed 0 Root RNG seed for jitter, generators, and per-CPE streams. 0 derives from time.Now().UnixNano() and is logged as root_seed=<N>.
--concurrency CPE_SIM_CONCURRENCY concurrency 1 Reserved for parallel session control. Today this is the bootstrap goroutine count used by bootstrapAll; fleet.count from the profile is the per-CPE count.
--config CPE_SIM_CONFIG (n/a) "" Path to a YAML config file holding any of the keys in this reference.
--log-level CPE_SIM_LOG_LEVEL logLevel info debug / info / warn / error.
--log-format CPE_SIM_LOG_FORMAT logFormat text text / json.
--version (n/a) (n/a) (n/a) Print version and exit. Consumed by main() before flag parsing so it composes cleanly with the rest of the flag set.

Determinism notes

When --seed is unset (or 0), the simulator picks a time-derived seed and logs:

INFO rng initialized seed_supplied=false root_seed=4823019283749132

Pass that value back via --seed=4823019283749132 to replay the run byte-for-byte. Per-CPE streams are derived from FNV-64a hash of (rootSeed, cpeID) so changing the fleet size doesn't shift earlier CPEs' streams.

YAML config file

Any of the keys above can live in a YAML file pointed at by --config:

acsURL: http://acs.local:7547/cwmp
acsTimeout: 1m
profile: /etc/cpe-sim/profile.yaml
crBindAddr: 0.0.0.0:7547
crPath: /cr
crPublishPath: Device.ManagementServer.ConnectionRequestURL
seed: 1
logLevel: info
logFormat: json

Unknown YAML keys reject (KnownFields = true) so a typo like caCert instead of caCertFile fails at startup with a precise error.

Resolution order

  1. Defaults are loaded.
  2. --config (or CPE_SIM_CONFIG) is resolved by pre-scanning args; the named YAML file (if present) overlays defaults.
  3. Every CPE_SIM_* env var is applied. Any unknown key in this prefix rejects.
  4. Flag parsing applies. Each flag's default is the post-env value, so flags only override when the caller explicitly sets them.
  5. Validation runs (interval > 0, log-level in known set, --cr-publish-path present when --cr-bind-addr is set, etc.).
  6. The validated Config is returned.

Error UX

Invalid flag / env / YAML errors include the source:

cpe-sim: cpeconfig.Load: env "CPE_SIM_ACS_TIMEOOT": unknown env key (typo? prefix CPE_SIM_ is reserved for cpe-sim)
cpe-sim: cpeconfig.Load: cr-publish-path is required when cr-bind-addr is set
  (no default; supply the parameter-tree path the listener URL should be written to,
  e.g. Device.ManagementServer.ConnectionRequestURL for TR-181 or
  InternetGatewayDevice.ManagementServer.ConnectionRequestURL for TR-098)

When in doubt, run with --help to see every flag with its current default (which reflects whatever env / config-file values resolved before flag parsing).

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