Module config 

Configuration file loading and validation.

The configuration is TOML. Unknown keys are rejected so typos surface at startup instead of being silently ignored:

[server]
listen = "0.0.0.0:443"
cert   = "/etc/volto/fullchain.pem"
key    = "/etc/volto/privkey.pem"
alpn   = ["h3"]      # optional, this is the default
shutdown_grace = 5   # seconds to let tunnels finish after SIGTERM, 0..3600

[auth]
users = [{ username = "user1", password = "..." }]

[limits]
udp_session_timeout  = 180   # seconds
max_targets_per_conn = 256
max_connections      = 256
connect_timeout      = 10    # seconds, 0 disables the budget
ip_family_preference = "ipv4" # ipv4 | ipv6 | system
max_streams_bidi     = 1024  # 1..65536
max_idle_timeout     = 60    # seconds
keep_alive_interval  = 20    # seconds, must be < max_idle_timeout / 2
initial_mtu          = 1200  # bytes, 1200..1452
mtu_discovery        = true
mtu_upper_bound      = 1452  # bytes, initial_mtu..1472
congestion_control   = "bbr" # bbr | cubic | newreno
initial_rtt_ms       = 333   # milliseconds, 10..10000
socket_recv_buffer   = 2097152 # bytes, 0 keeps the OS default
socket_send_buffer   = 2097152 # bytes, 0 keeps the OS default

[security]
allow_private_networks   = false
denied_ports             = [25]
unanswered_packet_budget = 64
max_auth_failures        = 5
expected_sni             = []   # non-empty turns the SNI gate on

[log]
level  = "info"      # optional, this is the default
keylog = false       # write TLS secrets to $SSLKEYLOGFILE (debug only)

Every section except [server] is optional, and every key within them has a default, so a minimal file is four lines. Two consequences of that are worth stating explicitly, because they are the difference between a safe and an unsafe deployment:

• an absent or empty [auth].users disables authentication, and
• [security] defaults deny private address space but nothing else.

Config::warnings reports the first of those at startup.

Rejecting unknown keys also makes a configuration file forward-only: one written for this version does not load on a release that predates any key in it, so the file has to be edited before a rollback rather than after the service fails to start. docs/configuration.md carries the operator’s half of that (which key arrived in which release, and why the policy stays).

Structs

Auth

[auth] — the accepted credentials.

Config

The complete server configuration.

Limits

[limits] — resource and lifetime limits.

Log

[log] — logging settings.

Security

[security] — destination policy and abuse mitigations.

Server

[server] — the QUIC listener and its TLS identity.

User

One set of HTTP Basic credentials.

Enums

CongestionControl

QUIC congestion controller, selected by [limits].congestion_control.

IpFamilyPreference

Which address family a target name is tried on first, selected by [limits].ip_family_preference.

Constants

DEFAULT_ALPN

ALPN protocol identifiers advertised when the config does not say otherwise.

DEFAULT_CONNECT_TIMEOUT

Default budget for reaching a target, in seconds.

DEFAULT_DENIED_PORTS

Ports no target may be reached on unless the operator says otherwise.

DEFAULT_INITIAL_MTU

Default initial QUIC packet size, in bytes.

DEFAULT_INITIAL_RTT_MS

Default round-trip time assumed before the first measurement, in milliseconds.

DEFAULT_KEEP_ALIVE_INTERVAL

Default keep-alive interval, in seconds.

DEFAULT_LOG_LEVEL

Log level used when [log].level is absent.

DEFAULT_MAX_AUTH_FAILURES

Default number of authentication failures tolerated on one connection.

DEFAULT_MAX_CONNECTIONS

Default cap on simultaneously open QUIC connections.

DEFAULT_MAX_IDLE_TIMEOUT

Default QUIC idle timeout, in seconds.

DEFAULT_MAX_STREAMS_BIDI

Default concurrent client-initiated bidirectional streams per connection.

DEFAULT_MAX_TARGETS_PER_CONN

Default number of concurrent tunnels allowed on one QUIC connection.

DEFAULT_MTU_UPPER_BOUND

Default ceiling for path MTU discovery, in bytes.

DEFAULT_SHUTDOWN_GRACE

Default grace period for a graceful shutdown, in seconds.

DEFAULT_SOCKET_RECV_BUFFER

Default UDP socket receive buffer to request, in bytes.

DEFAULT_SOCKET_SEND_BUFFER

Default UDP socket send buffer to request, in bytes.

DEFAULT_UDP_SESSION_TIMEOUT

Default UDP session idle timeout, in seconds.

DEFAULT_UNANSWERED_PACKET_BUDGET

Default number of packets a UDP session may send before the target answers.

EXAMPLE_PLACEHOLDER_PASSWORD

The password script/config.example.toml ships, which no running server may keep.

MAX_EXPECTED_SNI

The longest host name a server_name extension can carry, in bytes.

MAX_INITIAL_MTU

The largest initial_mtu this server accepts, in bytes.

MAX_MTU_UPPER_BOUND

The largest mtu_upper_bound this server accepts, in bytes.

MIN_INITIAL_MTU

The smallest initial_mtu QUIC permits (RFC 9000 §14).