add license banner for GNU AGPLv3 (#15178)

Bonus: rewrite subnet re-use of Transport

internal/config/subnet/config.go

@@ -0,0 +1,93 @@
+// Copyright (c) 2015-2021 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package subnet
+
+import (
+	"net/http"
+	"net/url"
+	"strings"
+
+	"github.com/minio/minio/internal/config"
+	"github.com/minio/pkg/env"
+	xnet "github.com/minio/pkg/net"
+)
+
+// DefaultKVS - default KV config for subnet settings
+var DefaultKVS = config.KVS{
+	config.KV{
+		Key:   config.License, // Deprecated Dec 2021
+		Value: "",
+	},
+	config.KV{
+		Key:   config.APIKey,
+		Value: "",
+	},
+	config.KV{
+		Key:   config.Proxy,
+		Value: "",
+	},
+}
+
+// Config represents the subnet related configuration
+type Config struct {
+	// The subnet license token - Deprecated Dec 2021
+	License string `json:"license"`
+
+	// The subnet api key
+	APIKey string `json:"api_key"`
+
+	// The HTTP(S) proxy URL to use for connecting to SUBNET
+	ProxyURL *xnet.URL `json:"proxy_url"`
+
+	// Transport configured with proxy_url if set optionally.
+	transport *http.Transport
+}
+
+// LookupConfig - lookup config and override with valid environment settings if any.
+func LookupConfig(kvs config.KVS, transport http.RoundTripper) (cfg Config, err error) {
+	if err = config.CheckValidKeys(config.SubnetSubSys, kvs, DefaultKVS); err != nil {
+		return cfg, err
+	}
+
+	proxy := env.Get(config.EnvMinIOSubnetProxy, kvs.Get(config.Proxy))
+	if len(proxy) > 0 {
+		cfg.ProxyURL, err = xnet.ParseHTTPURL(proxy)
+		if err != nil {
+			return cfg, err
+		}
+
+	}
+
+	cfg.License = strings.TrimSpace(env.Get(config.EnvMinIOSubnetLicense, kvs.Get(config.License)))
+	cfg.APIKey = strings.TrimSpace(env.Get(config.EnvMinIOSubnetAPIKey, kvs.Get(config.APIKey)))
+
+	if transport == nil {
+		// when transport is nil, it means we are just validating the
+		// inputs not performing any network calls.
+		return cfg, nil
+	}
+
+	// Make sure to clone the transport before editing the ProxyURL
+	ctransport := transport.(*http.Transport).Clone()
+	if cfg.ProxyURL != nil {
+		ctransport.Proxy = http.ProxyURL((*url.URL)(cfg.ProxyURL))
+	}
+	cfg.transport = ctransport
+
+	return cfg, nil
+}