libpod,netavark: correctly set /etc/resolv.conf for custom dns server and make --dns functional

libpod/container_internal_common.go

@@ -1993,24 +1993,35 @@ func (c *Container) generateResolvConf() error {
 		return err
 	}
 
+	networkBackend := c.runtime.config.Network.NetworkBackend
 	nameservers := make([]string, 0, len(c.runtime.config.Containers.DNSServers)+len(c.config.DNSServer))
-	nameservers = append(nameservers, c.runtime.config.Containers.DNSServers...)
-	for _, ip := range c.config.DNSServer {
-		nameservers = append(nameservers, ip.String())
+
+	// If NetworkBackend is `netavark` do not populate `/etc/resolv.conf`
+	// with custom dns server since after https://github.com/containers/netavark/pull/452
+	// netavark will always set required `nameservers` in statsBlock and libpod
+	// will correctly populate `networkNameServers`. Also see https://github.com/containers/podman/issues/16172
+
+	// Exception: Populate `/etc/resolv.conf` if container is not connected to any network
+	// ( i.e len(netStatus)==0 ) since in such case netavark is not invoked at all.
+	if networkBackend != string(types.Netavark) || len(netStatus) == 0 {
+		nameservers = append(nameservers, c.runtime.config.Containers.DNSServers...)
+		for _, ip := range c.config.DNSServer {
+			nameservers = append(nameservers, ip.String())
+		}
 	}
 	// If the user provided dns, it trumps all; then dns masq; then resolv.conf
-	var search []string
 	keepHostServers := false
 	if len(nameservers) == 0 {
 		keepHostServers = true
 		// first add the nameservers from the networks status
 		nameservers = networkNameServers
-		// when we add network dns server we also have to add the search domains
-		search = networkSearchDomains
 		// slirp4netns has a built in DNS forwarder.
 		nameservers = c.addSlirp4netnsDNS(nameservers)
 	}
 
+	// Set DNS search domains
+	search := networkSearchDomains
+
 	if len(c.config.DNSSearch) > 0 || len(c.runtime.config.Containers.DNSSearches) > 0 {
 		customSearch := make([]string, 0, len(c.config.DNSSearch)+len(c.runtime.config.Containers.DNSSearches))
 		customSearch = append(customSearch, c.runtime.config.Containers.DNSSearches...)

libpod/networking_common.go

@@ -39,9 +39,15 @@ func (c *Container) convertPortMappings() []types.PortMapping {
 }
 
 func (c *Container) getNetworkOptions(networkOpts map[string]types.PerNetworkOptions) types.NetworkOptions {
+	nameservers := make([]string, 0, len(c.runtime.config.Containers.DNSServers)+len(c.config.DNSServer))
+	nameservers = append(nameservers, c.runtime.config.Containers.DNSServers...)
+	for _, ip := range c.config.DNSServer {
+		nameservers = append(nameservers, ip.String())
+	}
 	opts := types.NetworkOptions{
 		ContainerID:   c.config.ID,
 		ContainerName: getNetworkPodName(c),
+		DNSServers:    nameservers,
 	}
 	opts.PortMappings = c.convertPortMappings()
 

test/e2e/run_networking_test.go

@@ -126,6 +126,37 @@ var _ = Describe("Podman run networking", func() {
 		Expect(session).Should(Exit(0))
 	})
 
+	It("podman verify resolv.conf with --dns + --network", func() {
+		// Following test is only functional with netavark and aardvark
+		// since new behaviour depends upon output from of statusBlock
+		SkipIfCNI(podmanTest)
+		net := createNetworkName("IntTest")
+		session := podmanTest.Podman([]string{"network", "create", net})
+		session.WaitWithDefaultTimeout()
+		defer podmanTest.removeNetwork(net)
+		Expect(session).Should(Exit(0))
+
+		session = podmanTest.Podman([]string{"run", "--name", "con1", "--dns", "1.1.1.1", "--network", net, ALPINE, "cat", "/etc/resolv.conf"})
+		session.WaitWithDefaultTimeout()
+		Expect(session).Should(Exit(0))
+		// Must not contain custom dns server in containers
+		// `/etc/resolv.conf` since custom dns-server is
+		// already expected to be present and processed by
+		// Podman's DNS resolver i.e ( aarvark-dns or dnsname ).
+		Expect(session.OutputToString()).ToNot(ContainSubstring("nameserver 1.1.1.1"))
+		// But /etc/resolve.conf must contain othe nameserver
+		// i.e dns server configured for network.
+		Expect(session.OutputToString()).To(ContainSubstring("nameserver"))
+
+		session = podmanTest.Podman([]string{"run", "--name", "con2", "--dns", "1.1.1.1", ALPINE, "cat", "/etc/resolv.conf"})
+		session.WaitWithDefaultTimeout()
+		Expect(session).Should(Exit(0))
+		// All the networks being used by following container
+		// don't have dns_enabled in such scenario `/etc/resolv.conf`
+		// must contain nameserver which were specified via `--dns`.
+		Expect(session.OutputToString()).To(ContainSubstring("nameserver 1.1.1.1"))
+	})
+
 	It("podman run network expose port 222", func() {
 		SkipIfRootless("iptables is not supported for rootless users")
 		session := podmanTest.Podman([]string{"run", "-dt", "--expose", "222-223", "-P", ALPINE, "/bin/sh"})

test/system/500-networking.bats

@@ -651,7 +651,7 @@ EOF
 "
 
     CONTAINERS_CONF=$containersconf run_podman run --rm $IMAGE cat /etc/resolv.conf
-    is "$output" "search example.com$nl.*" "correct search domain"
+    is "$output" "search example.com.*" "correct search domain"
     is "$output" ".*nameserver 1.1.1.1${nl}nameserver $searchIP${nl}nameserver 1.0.0.1${nl}nameserver 8.8.8.8" "nameserver order is correct"
 
     # create network with dns
@@ -660,9 +660,13 @@ EOF
     run_podman network create --subnet "$subnet.0/24"  $netname
     # custom server overwrites the network dns server
     CONTAINERS_CONF=$containersconf run_podman run --network $netname --rm $IMAGE cat /etc/resolv.conf
-    is "$output" "search example.com$nl.*" "correct search domain"
-    is "$output" ".*nameserver 1.1.1.1${nl}nameserver $searchIP${nl}nameserver 1.0.0.1${nl}nameserver 8.8.8.8" "nameserver order is correct"
-
+    is "$output" "search example.com.*" "correct search domain"
+    local store=$output
+    if is_netavark; then
+	is "$store" ".*nameserver $subnet.1.*" "integrated dns nameserver is set"
+    else
+	is "$store" ".*nameserver 1.1.1.1${nl}nameserver $searchIP${nl}nameserver 1.0.0.1${nl}nameserver 8.8.8.8" "nameserver order is correct"
+    fi
     # we should use the integrated dns server
     run_podman run --network $netname --rm $IMAGE cat /etc/resolv.conf
     is "$output" "search dns.podman.*" "correct search domain"