1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
|
package oci
import (
"context"
"os"
"path/filepath"
"github.com/docker/docker/libnetwork/resolvconf"
"github.com/docker/docker/pkg/idtools"
"github.com/moby/buildkit/solver/pb"
"github.com/moby/buildkit/util/flightcontrol"
"github.com/pkg/errors"
)
var g flightcontrol.Group[struct{}]
var notFirstRun bool
var lastNotEmpty bool
// overridden by tests
var resolvconfPath = func(netMode pb.NetMode) string {
// The implementation of resolvconf.Path checks if systemd resolved is activated and chooses the internal
// resolv.conf (/run/systemd/resolve/resolv.conf) in such a case - see resolvconf_path.go of libnetwork.
// This, however, can be problematic, see https://github.com/moby/buildkit/issues/2404 and is not necessary
// in case the networking mode is set to host since the locally (127.0.0.53) running resolved daemon is
// accessible from inside a host networked container.
// For details of the implementation see https://github.com/moby/buildkit/pull/5207#discussion_r1705362230.
if netMode == pb.NetMode_HOST {
return "/etc/resolv.conf"
}
return resolvconf.Path()
}
type DNSConfig struct {
Nameservers []string
Options []string
SearchDomains []string
}
func GetResolvConf(ctx context.Context, stateDir string, idmap *idtools.IdentityMapping, dns *DNSConfig, netMode pb.NetMode) (string, error) {
p := filepath.Join(stateDir, "resolv.conf")
if netMode == pb.NetMode_HOST {
p = filepath.Join(stateDir, "resolv-host.conf")
}
_, err := g.Do(ctx, p, func(ctx context.Context) (struct{}, error) {
generate := !notFirstRun
notFirstRun = true
if !generate {
fi, err := os.Stat(p)
if err != nil {
if !errors.Is(err, os.ErrNotExist) {
return struct{}{}, errors.WithStack(err)
}
generate = true
}
if !generate {
fiMain, err := os.Stat(resolvconfPath(netMode))
if err != nil {
if !errors.Is(err, os.ErrNotExist) {
return struct{}{}, err
}
if lastNotEmpty {
generate = true
lastNotEmpty = false
}
} else if fi.ModTime().Before(fiMain.ModTime()) {
generate = true
}
}
}
if !generate {
return struct{}{}, nil
}
dt, err := os.ReadFile(resolvconfPath(netMode))
if err != nil && !errors.Is(err, os.ErrNotExist) {
return struct{}{}, errors.WithStack(err)
}
tmpPath := p + ".tmp"
if dns != nil {
var (
dnsNameservers = dns.Nameservers
dnsSearchDomains = dns.SearchDomains
dnsOptions = dns.Options
)
if len(dns.Nameservers) == 0 {
dnsNameservers = resolvconf.GetNameservers(dt, resolvconf.IP)
}
if len(dns.SearchDomains) == 0 {
dnsSearchDomains = resolvconf.GetSearchDomains(dt)
}
if len(dns.Options) == 0 {
dnsOptions = resolvconf.GetOptions(dt)
}
f, err := resolvconf.Build(tmpPath, dnsNameservers, dnsSearchDomains, dnsOptions)
if err != nil {
return struct{}{}, errors.WithStack(err)
}
dt = f.Content
}
if netMode != pb.NetMode_HOST || len(resolvconf.GetNameservers(dt, resolvconf.IP)) == 0 {
f, err := resolvconf.FilterResolvDNS(dt, true)
if err != nil {
return struct{}{}, errors.WithStack(err)
}
dt = f.Content
}
if err := os.WriteFile(tmpPath, dt, 0644); err != nil {
return struct{}{}, errors.WithStack(err)
}
if idmap != nil {
root := idmap.RootPair()
if err := os.Chown(tmpPath, root.UID, root.GID); err != nil {
return struct{}{}, errors.WithStack(err)
}
}
if err := os.Rename(tmpPath, p); err != nil {
return struct{}{}, errors.WithStack(err)
}
return struct{}{}, nil
})
if err != nil {
return "", err
}
return p, nil
}
|
