Configuration: core directives

This page covers core KDL directives that control Ferron’s global HTTP behavior, network settings, and system-level limits.

Global-only directives

HTTP protocol & performance

• default_http_port <default_http_port: integer|null>
  • This directive specifies the default port for HTTP connections. If set as default_http_port #null, the implicit default HTTP port is disabled. Default: default_http_port 80
• default_https_port <default_https_port: integer|null>
  • This directive specifies the default port for HTTPS connections. If set as default_https_port #null, the implicit default HTTPS port is disabled. Default: default_https_port 443
• protocols <protocol: string> [<protocol: string> ...]
  • This directive specifies the enabled protocols for the web server. The supported protocols are "h1" (HTTP/1.x), "h2" (HTTP/2) and "h3" (HTTP/3; experimental). Default: protocols "h1" "h2"
• timeout <timeout: integer|null>
  • This directive specifies the maximum time (in milliseconds) for server to process the request, after which the server resets the connection. If set as timeout #null, the timeout is disabled. It’s not recommended to disable the timeout, as this might leave the server vulnerable to Slow HTTP attacks. Default: timeout 300000
• h2_initial_window_size <h2_initial_window_size: integer>
  • This directive specifies the HTTP/2 initial window size. Default: Hyper defaults
• h2_max_frame_size <h2_max_frame_size: integer>
  • This directive specifies the maximum HTTP/2 frame size. Default: Hyper defaults
• h2_max_concurrent_streams <h2_max_concurrent_streams: integer>
  • This directive specifies the maximum amount of concurrent HTTP/2 streams. Default: Hyper defaults
• h2_max_header_list_size <h2_max_header_list_size: integer>
  • This directive specifies the maximum HTTP/2 frame size. Default: Hyper defaults
• h2_enable_connect_protocol [h2_enable_connect_protocol: bool]
  • This directive specifies whether the CONNECT protocol in HTTP/2 is enabled. Default: Hyper defaults
• protocol_proxy [enable_proxy_protocol: bool]
  • This directive specifies whether the PROXY protocol acceptation is enabled. If enabled, the server will expect the PROXY protocol header at the beginning of each connection. Default: protocol_proxy #false
• buffer_request <request_buffer_size: integer|null>
  • This directive specifies the buffer size in bytes for incoming requests. If set as buffer_request #null, the request buffer is disabled. The request buffer can serve as an additional protection for underlying backend servers against Slowloris-style attacks. Default: buffer_request #null
• buffer_response <response_buffer_size: integer|null>
  • This directive specifies the buffer size in bytes for outgoing responses. If set as buffer_response #null, the response buffer is disabled. Default: buffer_response #null

Configuration example:

* {
    default_http_port 80
    default_https_port 443
    protocols "h1" "h2" "h3"
    timeout 300000
    h2_initial_window_size 65536
    h2_max_frame_size 16384
    h2_max_concurrent_streams 100
    h2_max_header_list_size 8192
    h2_enable_connect_protocol
    protocol_proxy #false
    buffer_request #null
    buffer_response #null
}

Networking & system

• listen_ip <listen_ip: string>
  • This directive specifies the IP address to listen. Default: listen_ip "::"
• io_uring [enable_io_uring: bool|null]
  • This directive specifies whether io_uring is enabled. If set as io_uring #null (supported on Ferron 2.4.0 and newer), io_uring is enabled with fallback with io_uring disabled. This directive has no effect for systems that don’t support io_uring and for web server builds that use Tokio instead of Monoio. Default: io_uring #null (Ferron 2.4.0 or newer), io_uring #true (Ferron 2.3.2 and older)
• tcp_send_buffer <tcp_send_buffer: integer>
  • This directive specifies the send buffer size in bytes for TCP listeners. Default: none
• tcp_recv_buffer <tcp_recv_buffer: integer>
  • This directive specifies the receive buffer size in bytes for TCP listeners. Default: none

Configuration example:

* {
    listen_ip "0.0.0.0"
    io_uring
    tcp_send_buffer 65536
    tcp_recv_buffer 65536
}