Pull request 1927: 6006-use-address-processor

Updates #6006.

Squashed commit of the following:

commit ac27db95c12858b6ef182a0bd4acebab67a23993
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Tue Jul 18 15:47:17 2023 +0300

    all: imp code

commit 3936288512bfc2d44902ead6ab1bb5711f92b73c
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon Jul 17 19:23:46 2023 +0300

    all: imp client resolving

internal/home/httpclient.go

@@ -0,0 +1,47 @@
+package home
+
+import (
+	"context"
+	"crypto/tls"
+	"net"
+	"net/http"
+	"net/url"
+	"time"
+)
+
+// httpClient returns a new HTTP client that uses the AdGuard Home's own DNS
+// server for resolving hostnames.  The resulting client should not be used
+// until [Context.dnsServer] is initialized.
+//
+// TODO(a.garipov, e.burkov): This is rather messy.  Refactor.
+func httpClient() (c *http.Client) {
+	// Do not use Context.dnsServer.DialContext directly in the struct literal
+	// below, since Context.dnsServer may be nil when this function is called.
+	dialContext := func(ctx context.Context, network, addr string) (conn net.Conn, err error) {
+		return Context.dnsServer.DialContext(ctx, network, addr)
+	}
+
+	return &http.Client{
+		// TODO(a.garipov): Make configurable.
+		Timeout: time.Minute * 5,
+		Transport: &http.Transport{
+			DialContext: dialContext,
+			Proxy:       httpProxy,
+			TLSClientConfig: &tls.Config{
+				RootCAs:      Context.tlsRoots,
+				CipherSuites: Context.tlsCipherIDs,
+				MinVersion:   tls.VersionTLS12,
+			},
+		},
+	}
+}
+
+// httpProxy returns parses and returns an HTTP proxy URL from the config, if
+// any.
+func httpProxy(_ *http.Request) (u *url.URL, err error) {
+	if config.ProxyURL == "" {
+		return nil, nil
+	}
+
+	return url.Parse(config.ProxyURL)
+}