docs for PR caddyserver/caddy#6573

src/docs/markdown/caddyfile/directives/bind.md

@@ -16,10 +16,13 @@ Note that binding sites inconsistently may result in unintended consequences. Fo
 ## Syntax
 
 ```caddy-d
-bind <hosts...>
+bind <hosts...> {
+	protocols <protocols...>
+}
 ```
 
 - **&lt;hosts...&gt;** is the list of host interfaces to bind which to bind the listener. 
+- **&lt;protocols...&gt;** is an optional override of the HTTP protocols to enable for the listener, see the [server options](/docs/caddyfile/options#protocols) for its accepted values and their meanings.
 
 
 ## Examples
@@ -64,6 +67,39 @@ example.com {
 }
 ```
 
+To bind to a Unix domain socket at `/run/caddy/stream.sock` that serves h1 and h2, and another at `/run/caddy/dgram.sock` that serves h3:
+
+```caddy
+example.com {
+	bind unix//run/caddy/stream.sock {
+		protocols h1 h2
+	}
+	bind unixgram//run/caddy/dgram.sock {
+		protocols h3
+	}
+}
+```
+
+To bind to inherited file descriptors specified with [environment placeholders](/docs/conventions#placeholders):
+
+```caddy
+http://example.com {
+	bind fd/{env.CADDY_HTTP_FD} {
+		protocols h1
+	}
+	redir https://example.com{uri} permanent
+}
+
+https://example.com {
+	bind fd/{env.CADDY_HTTPS_FD} {
+		protocols h1 h2
+	}
+	bind fdgram/{env.CADDY_HTTP3_FD} {
+		protocols h3
+	}
+}
+```
+
 To bind one domain to two different interfaces, with different responses:
 
 ```caddy

src/docs/markdown/caddyfile/options.md

@@ -56,7 +56,9 @@ Possible options are (click on each option to jump to its documentation):
 	debug
 	http_port    <port>
 	https_port   <port>
-	default_bind <hosts...>
+	default_bind <hosts...> {
+		protocols <protocols...>
+	}
 	order <dir1> first|last|[before|after <dir2>]
 	storage <module_name> {
 		<options...>
@@ -192,21 +194,44 @@ Default: `443`
 
 
 ##### `default_bind`
-The default bind address(es) to be used for all sites, if the [`bind` directive](/docs/caddyfile/directives/bind) is not used in the site. Default: empty, which binds to all interfaces.
+The default bind address(es) and optional HTTP protocol(s) (`h1|h2|h2c|h3`) to serve with them for all sites, if the [`bind` directive](/docs/caddyfile/directives/bind) is not used in the site. If multiple `default_bind` directives are present, each will be applied to servers with no `bind` directive in the order they were given. Default: empty, which binds to all interfaces, and serves the default protocols (`h1 h2 h3`) on them.
 
 <aside class="tip">
 
 Keep in mind that this will only apply to servers which are generated by the Caddyfile; this means that the HTTP server created by [Automatic HTTPS](/docs/automatic-https) for HTTP-to-HTTPS redirects will not inherit these bind addresses. To work around this, make sure to declare an `http://` site (it can be empty, with no directives) so that it exists when the Caddyfile is adapted, to receive the bind addresses.
 
 </aside>
 
+For example, to bind to `10.0.0.1` when no other address(es) are specified:
+
 ```caddy
 {
 	default_bind 10.0.0.1
 }
 ```
 
+To disable HTTP/3 unless otherwise specified:
+
+```caddy
+{
+	default_bind {
+		protocols h1 h2
+	}
+}
+```
 
+To create default listeners from file descriptors given by [environment variable placeholders](/docs/conventions#placeholders):
+
+```caddy
+{
+	default_bind fd/{env.CADDY_HTTPS_FD} {
+		protocols h1 h2
+	}
+	default_bind fdgram/{env.CADDY_HTTP3_FD} {
+		protocols h3
+	}
+}
+```
 
 ##### `order`
 Assigns an order to HTTP handler directive(s). As HTTP handlers execute in a sequential chain, it is necessary for the handlers to be executed in the right order. Standard directives have [a pre-defined order](/docs/caddyfile/directives#directive-order), but if using third-party HTTP handler modules, you'll need to define the order explicitly by either using this option or placing the directive in a [`route` block](/docs/caddyfile/directives/route). Ordering can be described absolutely (`first` or `last`), or relatively (`before` or `after`) to another directive.

src/docs/markdown/conventions.md

@@ -32,6 +32,7 @@ The network can be any of the following; ones suffixed with `4` or `6` are IPv4
 - UDP: `udp`, `udp4`, `udp6`
 - IP: `ip`, `ip4`, `ip6`
 - Unix: `unix`, `unixgram`, `unixpacket`
+- File descriptors: `fd`, `fdgram`
 
 The address part may be any of these forms:
 
@@ -42,10 +43,12 @@ The address part may be any of these forms:
 - `/path/to/unix/socket`
 - `/path/to/unix/socket|0200`
 
-The host may be any hostname, resolvable domain name, or IP address.
+The host may be any hostname, resolvable domain name, IP address, or file descriptor number.
 
 In the case of IPv6 addresses, the address must be enclosed in square brackets `[]`. The zone identifier (starting with `%`) is optional (often used for link-local addresses).
 
+In the case of file descriptors, the host must be an unsigned [integer literal](https://go.dev/ref/spec#Integer_literals).
+
 The port may be a single value (`:8080`) or an inclusive range (`:8080-8085`). A port range will be multiplied into singular addresses. Not all config fields accept port ranges. The special port `:0` means any available port.
 
 A unix socket path is only acceptable when using a `unix*` network type. The forward slash that separates the network and address is not considered part of the path.