Use custom for of grpc-go and unify client and server

vendor/google.golang.org/grpc/resolver/dns/dns_resolver.go

@@ -24,7 +24,6 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"math/rand"
 	"net"
 	"os"
 	"strconv"
@@ -34,6 +33,7 @@ import (
 
 	"golang.org/x/net/context"
 	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/internal/grpcrand"
 	"google.golang.org/grpc/resolver"
 )
 
@@ -51,8 +51,13 @@ const (
 )
 
 var (
-	errMissingAddr = errors.New("missing address")
-	randomGen      = rand.New(rand.NewSource(time.Now().UnixNano()))
+	errMissingAddr = errors.New("dns resolver: missing address")
+
+	// Addresses ending with a colon that is supposed to be the separator
+	// between host and port is not allowed.  E.g. "::" is a valid address as
+	// it is an IPv6 address (host only) and "[::]:" is invalid as it ends with
+	// a colon as the host and port separator
+	errEndsWithColon = errors.New("dns resolver: missing port after port-separator colon")
 )
 
 // NewBuilder creates a dnsBuilder which is used to factory DNS resolvers.
@@ -67,6 +72,9 @@ type dnsBuilder struct {
 
 // Build creates and starts a DNS resolver that watches the name resolution of the target.
 func (b *dnsBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOption) (resolver.Resolver, error) {
+	if target.Authority != "" {
+		return nil, fmt.Errorf("Default DNS resolver does not support custom DNS server")
+	}
 	host, port, err := parseTarget(target.Endpoint)
 	if err != nil {
 		return nil, err
@@ -295,7 +303,6 @@ func formatIP(addr string) (addrIP string, ok bool) {
 // target: "ipv4-host:80" returns host: "ipv4-host", port: "80"
 // target: "[ipv6-host]" returns host: "ipv6-host", port: "443"
 // target: ":80" returns host: "localhost", port: "80"
-// target: ":" returns host: "localhost", port: "443"
 func parseTarget(target string) (host, port string, err error) {
 	if target == "" {
 		return "", "", errMissingAddr
@@ -305,15 +312,15 @@ func parseTarget(target string) (host, port string, err error) {
 		return target, defaultPort, nil
 	}
 	if host, port, err = net.SplitHostPort(target); err == nil {
+		if port == "" {
+			// If the port field is empty (target ends with colon), e.g. "[::1]:", this is an error.
+			return "", "", errEndsWithColon
+		}
 		// target has port, i.e ipv4-host:port, [ipv6-host]:port, host-name:port
 		if host == "" {
 			// Keep consistent with net.Dial(): If the host is empty, as in ":80", the local system is assumed.
 			host = "localhost"
 		}
-		if port == "" {
-			// If the port field is empty(target ends with colon), e.g. "[::1]:", defaultPort is used.
-			port = defaultPort
-		}
 		return host, port, nil
 	}
 	if host, port, err = net.SplitHostPort(target + ":" + defaultPort); err == nil {
@@ -346,7 +353,7 @@ func chosenByPercentage(a *int) bool {
 	if a == nil {
 		return true
 	}
-	return randomGen.Intn(100)+1 <= *a
+	return grpcrand.Intn(100)+1 <= *a
 }
 
 func canaryingSC(js string) string {