reverse-proxy/tasks/config/validation.md

id, name, status, depends_on, scope, risk, impact, level

id	name	status	depends_on	scope	risk	impact	level
config/validation	Implement config validation with all 18 validation rules and error reporting	complete	config/static-config	moderate	medium	component	implementation

Description

Implement comprehensive config validation per the 18 rules defined in config.md. Validation runs on startup (fail-fast, exit with non-zero code) and on reload (reject reload, log error).

Validation Rules (from config.md)

1. At least one [[listeners]] entry must exist
2. Each listener's bind_addr is not 0.0.0.0 unless allow_wildcard_bind is enabled (config OR CLI flag — OR relationship)
3. Each listener's bind_addr and https_port combination must be unique
4. In ACME mode, acme_domains must be non-empty
5. In manual mode, cert_path and key_path must both be set and files must be readable
6. Each site must have a host and upstream
7. Site host values must be unique across all listeners (no duplicate hostnames)
8. rate_limit.requests_per_second must be > 0
9. body.limit_bytes must be > 0
10. Each listener's bind_addr and http_port combination must be unique (if http_port > 0)
11. Within a listener, http_port and https_port must differ
12. https_port must be 1–65535 (required — TLS needs a port)
13. http_port must be 0 (disabled) or 1–65535
14. health_check_port must not conflict with any listener's http_port or https_port on the same bind address
15. Site host values must not include a port number (e.g., git.alk.dev, not git.alk.dev:443)
16. Site host values must be valid hostnames (not IP addresses, not including ports). Hostnames normalized to lowercase
17. upstream must be in host:port format where port is 1–65535
18. upstream_scheme values must be "http" or "https" (lowercase)

Error Reporting

On validation failure, collect ALL errors (don't stop at first) and report them together. This helps operators fix multiple issues in one pass. Use a Vec<ValidationError> that is logged or printed on startup failure.

Startup vs Reload Behavior

• Startup: If validation fails, exit with non-zero code and log all validation errors
• Reload: If validation fails, reject the reload, log all errors, keep old DynamicConfig active

Acceptance Criteria

• All 18 validation rules implemented
• Validation collects all errors (doesn't stop at first)
• ValidationError enum with descriptive messages for each rule
• validate(config: &StaticConfig, dynamic: &DynamicConfig) -> Result<(), Vec<ValidationError>> function
• Startup validation: exits with code 1 on failure, logs all errors
• Reload validation: rejects reload on failure, logs all errors, keeps old config
• allow_wildcard_bind OR logic: config flag OR CLI flag enables it
• Hostname normalization to lowercase during validation
• File existence check for manual mode cert_path and key_path
• Unit tests covering each validation rule with valid and invalid inputs
• Integration test: valid config from config.md examples passes all validation

References

• docs/architecture/config.md — full validation rules, default values, TOML format
• docs/architecture/decisions/016-explicit-bind-address.md — 0.0.0.0 rejection rationale
• docs/architecture/decisions/020-container-deployment.md — allow_wildcard_bind for containers

Notes

Rule 5 (file readability check for manual certs) should check that the files exist and are readable at validation time, not just that the paths are set. This provides early feedback on misconfiguration.

Summary

To be filled on completion