1/*
 2 *
 3 * Copyright 2020 gRPC authors.
 4 *
 5 * Licensed under the Apache License, Version 2.0 (the "License");
 6 * you may not use this file except in compliance with the License.
 7 * You may obtain a copy of the License at
 8 *
 9 *     http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 */
18
19// Package unix implements a resolver for unix targets.
20package unix
21
22import (
23	"fmt"
24
25	"google.golang.org/grpc/internal/transport/networktype"
26	"google.golang.org/grpc/resolver"
27)
28
29const unixScheme = "unix"
30const unixAbstractScheme = "unix-abstract"
31
32type builder struct {
33	scheme string
34}
35
36func (b *builder) Build(target resolver.Target, cc resolver.ClientConn, _ resolver.BuildOptions) (resolver.Resolver, error) {
37	if target.URL.Host != "" {
38		return nil, fmt.Errorf("invalid (non-empty) authority: %v", target.URL.Host)
39	}
40
41	// gRPC was parsing the dial target manually before PR #4817, and we
42	// switched to using url.Parse() in that PR. To avoid breaking existing
43	// resolver implementations we ended up stripping the leading "/" from the
44	// endpoint. This obviously does not work for the "unix" scheme. Hence we
45	// end up using the parsed URL instead.
46	endpoint := target.URL.Path
47	if endpoint == "" {
48		endpoint = target.URL.Opaque
49	}
50	addr := resolver.Address{Addr: endpoint}
51	if b.scheme == unixAbstractScheme {
52		// We can not prepend \0 as c++ gRPC does, as in Golang '@' is used to signify we do
53		// not want trailing \0 in address.
54		addr.Addr = "@" + addr.Addr
55	}
56	cc.UpdateState(resolver.State{Addresses: []resolver.Address{networktype.Set(addr, "unix")}})
57	return &nopResolver{}, nil
58}
59
60func (b *builder) Scheme() string {
61	return b.scheme
62}
63
64func (b *builder) OverrideAuthority(resolver.Target) string {
65	return "localhost"
66}
67
68type nopResolver struct {
69}
70
71func (*nopResolver) ResolveNow(resolver.ResolveNowOptions) {}
72
73func (*nopResolver) Close() {}
74
75func init() {
76	resolver.Register(&builder{scheme: unixScheme})
77	resolver.Register(&builder{scheme: unixAbstractScheme})
78}