Introduce GRPC_PROXY EnvVar Support

Introduce the ability to specify a dial context for GRPC connections.

go.mod

@@ -36,6 +36,7 @@ require (
 	github.com/spf13/cobra v1.1.3
 	github.com/spf13/pflag v1.0.5
 	github.com/stretchr/testify v1.7.0
+	golang.org/x/net v0.0.0-20210520170846-37e1c6afe023
 	golang.org/x/time v0.0.0-20210723032227-1f47c861a9ac
 	google.golang.org/grpc v1.38.0
 	gopkg.in/yaml.v2 v2.4.0

pkg/controller/registry/grpc/source.go

@@ -2,12 +2,17 @@ package grpc
 
 import (
 	"context"
+	"net"
+	"net/url"
+	"os"
 	"sync"
 	"time"
 
 	"github.com/operator-framework/operator-registry/pkg/client"
 
 	"github.com/sirupsen/logrus"
+	"golang.org/x/net/http/httpproxy"
+	"golang.org/x/net/proxy"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/connectivity"
 
@@ -100,10 +105,71 @@ func (s *SourceStore) Get(key registry.CatalogKey) *SourceConn {
 	return &source
 }
 
+func grpcProxyURL(addr string) (*url.URL, error) {
+	// Handle ip addresses
+	host, _, err := net.SplitHostPort(addr)
+	if err != nil {
+		return nil, err
+	}
+
+	url, err := url.Parse(host)
+	if err != nil {
+		return nil, err
+	}
+
+	// Hardcode fields required for proxy resolution
+	url.Host = addr
+	url.Scheme = "http"
+
+	// Override HTTPS_PROXY and HTTP_PROXY with GRPC_PROXY
+	proxyConfig := &httpproxy.Config{
+		HTTPProxy:  getGRPCProxyEnv(),
+		HTTPSProxy: getGRPCProxyEnv(),
+		NoProxy:    getEnvAny("NO_PROXY", "no_proxy"),
+		CGI:        os.Getenv("REQUEST_METHOD") != "",
+	}
+
+	// Check if a proxy should be used based on Environment variables
+	return proxyConfig.ProxyFunc()(url)
+}
+
+func getGRPCProxyEnv() string {
+	return getEnvAny("GRPC_PROXY", "grpc_proxy")
+}
+
+func getEnvAny(names ...string) string {
+	for _, n := range names {
+		if val := os.Getenv(n); val != "" {
+			return val
+		}
+	}
+	return ""
+}
+
+func grpcConnection(address string) (*grpc.ClientConn, error) {
+	// Check if a proxy should be used based on Environment variables
+	proxyURL, err := grpcProxyURL(address)
+	if err != nil {
+		return nil, err
+	}
+
+	if proxyURL != nil {
+		return grpc.Dial(address, grpc.WithInsecure(), grpc.WithContextDialer(func(ctx context.Context, addr string) (net.Conn, error) {
+			dialer, err := proxy.FromURL(proxyURL, &net.Dialer{})
+			if err != nil {
+				return nil, err
+			}
+			return dialer.Dial("tcp", addr)
+		}))
+	}
+
+	return grpc.Dial(address, grpc.WithInsecure())
+}
+
 func (s *SourceStore) Add(key registry.CatalogKey, address string) (*SourceConn, error) {
 	_ = s.Remove(key)
 
-	conn, err := grpc.Dial(address, grpc.WithInsecure())
+	conn, err := grpcConnection(address)
 	if err != nil {
 		return nil, err
 	}