Pull request 317: 379 fix ipv6 upstream

Updates #379.

Co-authored-by: Eugene Burkov [email protected]

Squashed commit of the following:

commit 767d954
Author: Stanislav Chzhen <[email protected]>
Date:   Tue Jan 30 19:31:07 2024 +0300

    upstream: imp code

commit 313c715
Author: Stanislav Chzhen <[email protected]>
Date:   Tue Jan 30 18:32:55 2024 +0300

    upstream: add todo

commit 83e1561
Author: Stanislav Chzhen <[email protected]>
Date:   Tue Jan 30 17:41:14 2024 +0300

    upstream: imp code

commit 5c48f20
Author: Stanislav Chzhen <[email protected]>
Date:   Tue Jan 30 14:42:48 2024 +0300

    upstream: fix ipv6 upstream

upstream/upstream.go

@@ -206,6 +206,7 @@ func validateUpstreamURL(u *url.URL) (err error) {
 	}
 
 	host := u.Host
+	// TODO(s.chzhen):  Consider using [netutil.SplitHostPort].
 	h, port, splitErr := net.SplitHostPort(host)
 	if splitErr == nil {
 		// Validate port.
@@ -217,7 +218,14 @@ func validateUpstreamURL(u *url.URL) (err error) {
 		host = h
 	}
 
-	_, err = netip.ParseAddr(host)
+	// If it's an IPv6 address enclosed in square brackets with no port.
+	//
+	// See https://github.com/AdguardTeam/dnsproxy/issues/379.
+	if strings.HasPrefix(host, "[") && strings.HasSuffix(host, "]") {
+		_, err = netip.ParseAddr(host[1 : len(host)-1])
+	} else {
+		_, err = netip.ParseAddr(host)
+	}
 	if err == nil {
 		return nil
 	}

upstream/upstream_test.go

@@ -260,6 +260,18 @@ func TestAddressToUpstream(t *testing.T) {
 		addr: "h3://one.one.one.one",
 		opt:  opt,
 		want: "https://one.one.one.one:443",
+	}, {
+		addr: "::ffff:1.1.1.1",
+		opt:  nil,
+		want: "[::ffff:1.1.1.1]:53",
+	}, {
+		addr: "https://[2606:4700:4700::1111]/dns-query",
+		opt:  nil,
+		want: "https://[2606:4700:4700::1111]:443/dns-query",
+	}, {
+		addr: "https://[2606:4700:4700::1111]:443/dns-query",
+		opt:  nil,
+		want: "https://[2606:4700:4700::1111]:443/dns-query",
 	}}
 
 	for _, tc := range testCases {