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Move dummy DNS server to integration/internal/network

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Signed-off-by: Rob Murray <rob.murray@docker.com>
This commit is contained in:
Rob Murray 2024-04-04 09:19:45 +01:00
parent 6d30487d2e
commit d8b768149b
2 changed files with 72 additions and 64 deletions
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66
integration/internal/network/dns.go Normal file
View file

@ -0,0 +1,66 @@
package network
import (
"net"
"os"
"testing"
"github.com/miekg/dns"
"gotest.tools/v3/assert"
)
const DNSRespAddr = "10.11.12.13"
// WriteTempResolvConf writes a resolv.conf that only contains a single
// nameserver line, with address addr.
// It returns the name of the temp file. The temp file will be deleted
// automatically by a t.Cleanup().
func WriteTempResolvConf(t *testing.T, addr string) string {
t.Helper()
// Not using t.TempDir() here because in rootless mode, while the temporary
// directory gets mode 0777, it's a subdir of an 0700 directory owned by root.
// So, it's not accessible by the daemon.
f, err := os.CreateTemp("", "resolv.conf")
assert.NilError(t, err)
t.Cleanup(func() { os.Remove(f.Name()) })
err = f.Chmod(0644)
assert.NilError(t, err)
f.Write([]byte("nameserver " + addr + "\n"))
return f.Name()
}
// StartDaftDNS starts and returns a really, really daft DNS server that only
// responds to type-A requests, and always with address dnsRespAddr.
// The DNS server will be stopped automatically by a t.Cleanup().
func StartDaftDNS(t *testing.T, addr string) {
serveDNS := func(w dns.ResponseWriter, query *dns.Msg) {
if query.Question[0].Qtype == dns.TypeA {
resp := &dns.Msg{}
resp.SetReply(query)
answer := &dns.A{
Hdr: dns.RR_Header{
Name: query.Question[0].Name,
Rrtype: dns.TypeA,
Class: dns.ClassINET,
Ttl: 600,
},
}
answer.A = net.ParseIP(DNSRespAddr)
resp.Answer = append(resp.Answer, answer)
_ = w.WriteMsg(resp)
}
}
conn, err := net.ListenUDP("udp", &net.UDPAddr{
IP: net.ParseIP(addr),
Port: 53,
})
assert.NilError(t, err)
server := &dns.Server{Handler: dns.HandlerFunc(serveDNS), PacketConn: conn}
go func() {
_ = server.ActivateAndServe()
}()
t.Cleanup(func() { server.Shutdown() })
}

70
integration/networking/resolvconf_test.go
View file

@ -1,8 +1,6 @@
package networking
import (
"net"
"os"
"strings"
"testing"
@ -10,29 +8,11 @@ import (
"github.com/docker/docker/integration/internal/container"
"github.com/docker/docker/integration/internal/network"
"github.com/docker/docker/testutil/daemon"
"github.com/miekg/dns"
"gotest.tools/v3/assert"
is "gotest.tools/v3/assert/cmp"
"gotest.tools/v3/skip"
)
// writeTempResolvConf writes a resolv.conf that only contains a single
// nameserver line, with address addr.
// It returns the name of the temp file.
func writeTempResolvConf(t *testing.T, addr string) string {
t.Helper()
// Not using t.TempDir() here because in rootless mode, while the temporary
// directory gets mode 0777, it's a subdir of an 0700 directory owned by root.
// So, it's not accessible by the daemon.
f, err := os.CreateTemp("", "resolv.conf")
assert.NilError(t, err)
t.Cleanup(func() { os.Remove(f.Name()) })
err = f.Chmod(0644)
assert.NilError(t, err)
f.Write([]byte("nameserver " + addr + "\n"))
return f.Name()
}
// Regression test for https://github.com/moby/moby/issues/46968
func TestResolvConfLocalhostIPv6(t *testing.T) {
// No "/etc/resolv.conf" on Windows.
@ -40,7 +20,7 @@ func TestResolvConfLocalhostIPv6(t *testing.T) {
ctx := setupTest(t)
tmpFileName := writeTempResolvConf(t, "127.0.0.53")
tmpFileName := network.WriteTempResolvConf(t, "127.0.0.53")
d := daemon.New(t, daemon.WithEnvVars("DOCKER_TEST_RESOLV_CONF_PATH="+tmpFileName))
d.StartWithBusybox(ctx, t, "--experimental", "--ip6tables")
@ -81,43 +61,6 @@ options ndots:0
`))
}
const dnsRespAddr = "10.11.12.13"
// startDaftDNS starts and returns a really, really daft DNS server that only
// responds to type-A requests, and always with address dnsRespAddr.
func startDaftDNS(t *testing.T, addr string) *dns.Server {
serveDNS := func(w dns.ResponseWriter, query *dns.Msg) {
if query.Question[0].Qtype == dns.TypeA {
resp := &dns.Msg{}
resp.SetReply(query)
answer := &dns.A{
Hdr: dns.RR_Header{
Name: query.Question[0].Name,
Rrtype: dns.TypeA,
Class: dns.ClassINET,
Ttl: 600,
},
}
answer.A = net.ParseIP(dnsRespAddr)
resp.Answer = append(resp.Answer, answer)
_ = w.WriteMsg(resp)
}
}
conn, err := net.ListenUDP("udp", &net.UDPAddr{
IP: net.ParseIP(addr),
Port: 53,
})
assert.NilError(t, err)
server := &dns.Server{Handler: dns.HandlerFunc(serveDNS), PacketConn: conn}
go func() {
_ = server.ActivateAndServe()
}()
return server
}
// Check that when a container is connected to an internal network, DNS
// requests sent to daemon's internal DNS resolver are not forwarded to
// an upstream resolver listening on a localhost address.
@ -128,11 +71,10 @@ func TestInternalNetworkDNS(t *testing.T) {
ctx := setupTest(t)
// Start a DNS server on the loopback interface.
server := startDaftDNS(t, "127.0.0.1")
defer server.Shutdown()
network.StartDaftDNS(t, "127.0.0.1")
// Set up a temp resolv.conf pointing at that DNS server, and a daemon using it.
tmpFileName := writeTempResolvConf(t, "127.0.0.1")
tmpFileName := network.WriteTempResolvConf(t, "127.0.0.1")
d := daemon.New(t, daemon.WithEnvVars("DOCKER_TEST_RESOLV_CONF_PATH="+tmpFileName))
d.StartWithBusybox(ctx, t, "--experimental", "--ip6tables")
defer d.Stop(t)
@ -160,7 +102,7 @@ func TestInternalNetworkDNS(t *testing.T) {
res, err := container.Exec(ctx, c, ctrId, []string{"nslookup", "test.example"})
assert.NilError(t, err)
assert.Check(t, is.Equal(res.ExitCode, 0))
assert.Check(t, is.Contains(res.Stdout(), dnsRespAddr))
assert.Check(t, is.Contains(res.Stdout(), network.DNSRespAddr))
// Connect the container to the internal network as well.
// External DNS should still be used.
@ -169,7 +111,7 @@ func TestInternalNetworkDNS(t *testing.T) {
res, err = container.Exec(ctx, c, ctrId, []string{"nslookup", "test.example"})
assert.NilError(t, err)
assert.Check(t, is.Equal(res.ExitCode, 0))
assert.Check(t, is.Contains(res.Stdout(), dnsRespAddr))
assert.Check(t, is.Contains(res.Stdout(), network.DNSRespAddr))
// Disconnect from the external network.
// Expect no access to the external DNS.
@ -187,5 +129,5 @@ func TestInternalNetworkDNS(t *testing.T) {
res, err = container.Exec(ctx, c, ctrId, []string{"nslookup", "test.example"})
assert.NilError(t, err)
assert.Check(t, is.Equal(res.ExitCode, 0))
assert.Check(t, is.Contains(res.Stdout(), dnsRespAddr))
assert.Check(t, is.Contains(res.Stdout(), network.DNSRespAddr))
}