[proxy] Add --without-dns flag, and change meaning of --with-dns flag

prog/weaveproxy/main.go

@@ -36,7 +36,8 @@ func main() {
 	getopt.BoolVarLong(&c.TLSConfig.Enabled, "tls", 0, "Use TLS; implied by --tlsverify")
 	getopt.StringVarLong(&c.TLSConfig.Key, "tlskey", 0, "Path to TLS key file")
 	getopt.BoolVarLong(&c.TLSConfig.Verify, "tlsverify", 0, "Use TLS and verify the remote")
-	getopt.BoolVarLong(&c.WithDNS, "with-dns", 'w', "instruct created containers to use weaveDNS as their nameserver")
+	getopt.BoolVarLong(&c.WithDNS, "with-dns", 'w', "instruct created containers to always use weaveDNS as their nameserver")
+	getopt.BoolVarLong(&c.WithoutDNS, "without-dns", 0, "instruct created containers to never use weaveDNS as their nameserver")
 	getopt.BoolVarLong(&c.WithIPAM, "with-ipam", 'i', "automatically allocate addresses for containers without a WEAVE_CIDR")
 	getopt.Parse()
 
@@ -45,6 +46,10 @@ func main() {
 		os.Exit(0)
 	}
 
+	if c.WithDNS && c.WithoutDNS {
+		Error.Fatalf("Cannot use both '--with-dns' and '--without-dns' flags")
+	}
+
 	if debug {
 		InitDefaultLogging(true)
 	}

proxy/create_container_interceptor.go

@@ -81,7 +81,12 @@ func (i *createContainerInterceptor) setWeaveWaitEntrypoint(container *docker.Co
 }
 
 func (i *createContainerInterceptor) setWeaveDNS(container *createContainerRequestBody, r *http.Request) error {
-	if !i.proxy.WithDNS {
+	if i.proxy.WithoutDNS {
+		return nil
+	}
+
+	dnsDomain, dnsRunning := i.getDNSDomain()
+	if !(dnsRunning || i.proxy.WithDNS) {
 		return nil
 	}
 
@@ -95,13 +100,13 @@ func (i *createContainerInterceptor) setWeaveDNS(container *createContainerReque
 	if container.Hostname == "" && name != "" {
 		container.Hostname = name
 		// Strip trailing period because it's unusual to see it used on the end of a host name
-		container.Domainname = strings.TrimSuffix(i.getDNSDomain(), ".")
+		container.Domainname = strings.TrimSuffix(dnsDomain, ".")
 	}
 
 	return nil
 }
 
-func (i *createContainerInterceptor) getDNSDomain() (domain string) {
+func (i *createContainerInterceptor) getDNSDomain() (domain string, running bool) {
 	domain = nameserver.DefaultLocalDomain
 	dnsContainer, err := i.proxy.client.InspectContainer("weavedns")
 	if err != nil ||
@@ -122,7 +127,7 @@ func (i *createContainerInterceptor) getDNSDomain() (domain string) {
 		return
 	}
 
-	return string(b)
+	return string(b), true
 }
 
 func (i *createContainerInterceptor) InterceptResponse(r *http.Response) error {

proxy/proxy.go

@@ -37,6 +37,7 @@ type Config struct {
 	TLSConfig  TLSConfig
 	Version    string
 	WithDNS    bool
+	WithoutDNS bool
 	WithIPAM   bool
 }
 
@@ -61,7 +62,7 @@ func NewProxy(c Config) (*Proxy, error) {
 		},
 	}
 
-	if p.WithDNS {
+	if !p.WithoutDNS {
 		dockerBridgeIP, err := callWeave("docker-bridge-ip")
 		if err != nil {
 			return nil, err

site/proxy.md

@@ -115,13 +115,17 @@ are handled as before.
 
 ## <a name="dns"></a>Automatic discovery
 
-Containers started via the proxy are automatically registered in
-[weaveDNS](weavedns.html) if they have a hostname in the weaveDNS
-domain (usually `.weave.local`). In order for containers to be able to
-look up such names, their DNS resolver needs to be configured to point
-at weaveDNS. This can be done [manually](weavedns.html#without-run),
-or automatically by the proxy by launching it with the `--with-dns`
-option, i.e.
+Containers started via the proxy are
+automatically registered in [weaveDNS](weavedns.html) if they have a
+hostname in the weaveDNS domain (usually `.weave.local`). In order for
+containers to be able to look up such names, their DNS resolver needs
+to be configured to point at weaveDNS. This will be done automatically by the proxy
+ while weaveDNS is running. To disable this launch the proxy with the `--without-dns` option, i.e.
+
+    host1$ weave launch-proxy --without-dns
+
+To enable weaveDNS resolution when weaveDNS is not running, launch the
+proxy with the `--with-dns` option, i.e.
 
     host1$ weave launch-proxy --with-dns
 

test/630_proxy_dns_test.sh

@@ -7,14 +7,39 @@ C2=10.2.0.34
 C1_NAME=c1.weave.local
 C2_NAME=seetwo.weave.local
 
+boot_containers() {
+  proxy docker_on $HOST1 run -e WEAVE_CIDR=$C2/24 -dt --name=c2 -h $C2_NAME $DNS_IMAGE /bin/sh
+  proxy docker_on $HOST1 run -e WEAVE_CIDR=$C1/24 -dt --name=c1             $DNS_IMAGE /bin/sh
+}
+
+kill_containers() {
+  docker_on $HOST1 kill c1 c2
+  docker_on $HOST1 rm   c1 c2
+}
+
 start_suite "Proxy registers containers with dns"
 
-weave_on $HOST1 launch-dns 10.2.254.1/24 $WEAVEDNS_ARGS
-weave_on $HOST1 launch-proxy --with-dns
-proxy docker_on $HOST1 run -e WEAVE_CIDR=$C2/24 -dt --name=c2 -h $C2_NAME $DNS_IMAGE /bin/sh
-proxy docker_on $HOST1 run -e WEAVE_CIDR=$C1/24 -dt --name=c1             $DNS_IMAGE /bin/sh
+bridge_ip=$(weave_on $HOST1 docker-bridge-ip)
 
+weave_on $HOST1 launch-proxy --with-dns
+boot_containers
+assert "exec_on $HOST1 c1 cat /etc/resolv.conf" "nameserver $bridge_ip"
+assert "exec_on $HOST1 c2 cat /etc/resolv.conf" "nameserver $bridge_ip"
+weave_on $HOST1 stop-proxy
+kill_containers
+
+weave_on $HOST1 launch-dns 10.2.254.1/24 $WEAVEDNS_ARGS
+
+weave_on $HOST1 launch-proxy
+boot_containers
 assert_dns_record $HOST1 c1 $C2_NAME $C2
 assert_dns_record $HOST1 c2 $C1_NAME $C1
+weave_on $HOST1 stop-proxy
+kill_containers
+
+weave_on $HOST1 launch-proxy --without-dns
+boot_containers
+assert_no_dns_record $HOST1 c1 $C2_NAME
+assert_no_dns_record $HOST1 c2 $C1_NAME
 
 end_suite

weave

@@ -29,7 +29,7 @@ usage() {
     echo "weave launch       [-password <password>] [-nickname <nickname>] [-nodiscovery]"
     echo "                       [-iprange <cidr> [-ipsubnet <cidr>]] <peer> ..."
     echo "weave launch-dns   [<addr>]"
-    echo "weave launch-proxy [-D <endpoint>] [-H <endpoint>] [--with-dns] [--with-ipam]"
+    echo "weave launch-proxy [-D <endpoint>] [-H <endpoint>] [--with-dns|--without-dns] [--with-ipam]"
     echo "weave connect      [--replace] [<peer> ...]"
     echo "weave forget       <peer> ..."
     echo "weave run          [--with-dns] [<addr> ...] <docker run args> ..."