Changing Ubuntu Net manager to write to /etc/resolv.conf.d/base

[#123916651]

Signed-off-by: Cornelius Schumacher <[email protected]>

platform/net/ubuntu_net_manager.go

@@ -353,27 +353,52 @@ func (net UbuntuNetManager) ifaceNames(dhcpConfigs DHCPInterfaceConfigurations,
 func (net UbuntuNetManager) writeResolvConf(networks boshsettings.Networks) error {
 	buffer := bytes.NewBuffer([]byte{})
 
-	const ubuntuResolvConfTemplate = `# Generated by bosh-agent
+	const resolvConfTemplate = `# Generated by bosh-agent
 {{ range .DNSServers }}nameserver {{ . }}
 {{ end }}`
 
-	t := template.Must(template.New("resolv-conf").Parse(ubuntuResolvConfTemplate))
+	t := template.Must(template.New("resolv-conf").Parse(resolvConfTemplate))
 
 	// Keep DNS servers in the order specified by the network
 	dnsNetwork, _ := networks.DefaultNetworkFor("dns")
 
 	type dnsConfigArg struct {
 		DNSServers []string
 	}
+
 	dnsServersArg := dnsConfigArg{dnsNetwork.DNS}
+
 	err := t.Execute(buffer, dnsServersArg)
 	if err != nil {
-		return bosherr.WrapError(err, "Generating config from template")
+		return bosherr.WrapError(err, "Generating DNS config from template")
+	}
+
+	if len(dnsNetwork.DNS) > 0 {
+		// Write out base so that releases may overwrite head
+		err = net.fs.WriteFile("/etc/resolvconf/resolv.conf.d/base", buffer.Bytes())
+		if err != nil {
+			return bosherr.WrapError(err, "Writing to /etc/resolvconf/resolv.conf.d/base")
+		}
+	} else {
+		// For the first time before resolv.conf is symlinked to /run/...
+		// inherit possibly configured resolv.conf
+
+		targetPath, err := net.fs.ReadLink("/etc/resolv.conf")
+		if err != nil {
+			return bosherr.WrapError(err, "Reading /etc/resolv.conf symlink")
+		}
+
+		if targetPath == "/etc/resolv.conf" {
+			err := net.fs.CopyFile("/etc/resolv.conf", "/etc/resolvconf/resolv.conf.d/base")
+			if err != nil {
+				return bosherr.WrapError(err, "Copying /etc/resolv.conf for backwards compat")
+			}
+		}
 	}
 
-	err = net.fs.WriteFile("/etc/resolvconf/resolv.conf.d/head", buffer.Bytes())
+	err = net.fs.Symlink("/run/resolvconf/resolv.conf", "/etc/resolv.conf")
 	if err != nil {
-		return bosherr.WrapError(err, "Writing to /etc/resolvconf/resolv.conf.d/head")
+		return bosherr.WrapError(err, "Setting up /etc/resolv.conf symlink")
 	}
 
 	_, _, _, err = net.cmdRunner.RunCommand("resolvconf", "-u")

platform/net/ubuntu_net_manager_test.go

@@ -202,8 +202,118 @@ dns-nameservers 8.8.8.8 9.9.9.9`
 		})
 
 		Context("networks is preconfigured", func() {
+			var networks boshsettings.Networks
+			BeforeEach(func() {
+				dhcpNetwork.Preconfigured = true
+				staticNetwork.Preconfigured = true
+				networks = boshsettings.Networks{
+					"first":  dhcpNetwork,
+					"second": staticNetwork,
+				}
+
+				Expect(networks.IsPreconfigured()).To(BeTrue())
+			})
+
+			Context("when there are configured DNS servers", func() {
+				BeforeEach(func() {
+					networks = boshsettings.Networks{
+						"first": dhcpNetwork,
+					}
+				})
+
+				It("writes DNS to /etc/resolvconf/resolv.conf.d/base", func() {
+					err := netManager.SetupNetworking(networks, nil)
+					Expect(err).ToNot(HaveOccurred())
+
+					resolvConfBase := fs.GetFileTestStat("/etc/resolvconf/resolv.conf.d/base")
+					Expect(resolvConfBase).ToNot(BeNil())
+
+					expectedResolvConfBase := `# Generated by bosh-agent
+nameserver 8.8.8.8
+nameserver 9.9.9.9
+`
+					Expect(resolvConfBase.StringContents()).To(Equal(expectedResolvConfBase))
+				})
+
+				Context("when writing to ../resolv.conf.d/base fails", func() {
+					It("fails reporting the error", func() {
+						fs.WriteFileError = errors.New("fake-write-file-error")
+
+						err := netManager.SetupNetworking(networks, nil)
+						Expect(err).To(HaveOccurred())
+						Expect(err.Error()).To(ContainSubstring("Writing to /etc/resolvconf/resolv.conf.d/base"))
+					})
+				})
+			})
+
+			Context("when no DNS servers are configured", func() {
+				BeforeEach(func() {
+					dhcpNetwork.DNS = []string{}
+					networks = boshsettings.Networks{
+						"first":  dhcpNetwork,
+						"second": staticNetwork,
+					}
+				})
+
+				Context("when could not read link /etc/resolv.conf", func() {
+					It("fails reporting error", func() {
+						fs.ReadLinkError = errors.New("fake-read-link-error")
+
+						err := netManager.SetupNetworking(networks, nil)
+						Expect(err).To(HaveOccurred())
+						Expect(err.Error()).To(ContainSubstring("Reading /etc/resolv.conf symlink"))
+					})
+				})
+
+				Context("when /etc/resolv.conf is no symlink", func() {
+					BeforeEach(func() {
+						err := fs.Symlink("/etc/resolv.conf", "/etc/resolv.conf")
+						Expect(err).ToNot(HaveOccurred())
+
+						err = fs.WriteFileString("/etc/resolv.conf", "fake-content")
+						Expect(err).ToNot(HaveOccurred())
+					})
+
+					It("copies /etc/resolv.conf to .../resolv.conf.d/base", func() {
+						err := netManager.SetupNetworking(networks, nil)
+						Expect(err).ToNot(HaveOccurred())
+
+						contents, err := fs.ReadFile("/etc/resolvconf/resolv.conf.d/base")
+						Expect(err).ToNot(HaveOccurred())
+						Expect(string(contents)).To(Equal("fake-content"))
+					})
+
+					Context("when copying fails", func() {
+						It("fails reporting the error", func() {
+							fs.CopyFileError = errors.New("fake-copy-error")
+
+							err := netManager.SetupNetworking(networks, nil)
+							Expect(err).To(HaveOccurred())
+							Expect(err.Error()).To(ContainSubstring("Copying /etc/resolv.conf for backwards compat"))
+						})
+					})
+				})
+			})
 
-			It("writes dns servers in /etc/resolvconf/resolv.conf.d/head", func() {
+			It("forces /etc/resolv.conf to be a symlink", func() {
+				err := netManager.SetupNetworking(networks, nil)
+				Expect(err).ToNot(HaveOccurred())
+				Expect(fs.ReadLink("/etc/resolv.conf")).To(Equal("/run/resolvconf/resolv.conf"))
+			})
+
+			Context("when symlink command fails", func() {
+				BeforeEach(func() {
+					fs.SymlinkError = errors.New("fake-symlink-error")
+				})
+
+				It("fails reporting error", func() {
+					err := netManager.SetupNetworking(networks, nil)
+					Expect(err).To(HaveOccurred())
+					Expect(err.Error()).To(ContainSubstring("Setting up /etc/resolv.conf symlink"))
+				})
+			})
+
+			It("writes dns servers in /etc/resolvconf/resolv.conf.d/base", func() {
 				dhcpNetwork.Preconfigured = true
 				staticNetwork.Preconfigured = true
 				networks := boshsettings.Networks{
@@ -216,7 +326,7 @@ dns-nameservers 8.8.8.8 9.9.9.9`
 				err := netManager.SetupNetworking(networks, nil)
 				Expect(err).ToNot(HaveOccurred())
 
-				resolvConfHead := fs.GetFileTestStat("/etc/resolvconf/resolv.conf.d/head")
+				resolvConfHead := fs.GetFileTestStat("/etc/resolvconf/resolv.conf.d/base")
 				Expect(resolvConfHead).ToNot(BeNil())
 
 				expectedResolvConfHead = `# Generated by bosh-agent
@@ -240,7 +350,6 @@ nameserver 9.9.9.9
 				Expect(len(cmdRunner.RunCommands)).To(Equal(1))
 				Expect(cmdRunner.RunCommands[0]).To(Equal([]string{"resolvconf", "-u"}))
 			})
-
 		})
 
 		It("writes interfaces in /etc/network/interfaces in alphabetic order", func() {