Add Tailscale unstable channel and repo HEAD to integration tests

In preparation for the implementation of the new TS2021 protocol (Tailscale control protocol v2) we are expanding the test infrastructure

Dockerfile.tailscale

@@ -1,11 +1,12 @@
 FROM ubuntu:latest
 
 ARG TAILSCALE_VERSION
+ARG TAILSCALE_CHANNEL
 
 RUN apt-get update \
     && apt-get install -y gnupg curl \
-    && curl -fsSL https://pkgs.tailscale.com/stable/ubuntu/focal.gpg | apt-key add - \
+    && curl -fsSL https://pkgs.tailscale.com/${TAILSCALE_CHANNEL}/ubuntu/focal.gpg | apt-key add - \
-    && curl -fsSL https://pkgs.tailscale.com/stable/ubuntu/focal.list | tee /etc/apt/sources.list.d/tailscale.list \
+    && curl -fsSL https://pkgs.tailscale.com/${TAILSCALE_CHANNEL}/ubuntu/focal.list | tee /etc/apt/sources.list.d/tailscale.list \
     && apt-get update \
     && apt-get install -y ca-certificates tailscale=${TAILSCALE_VERSION} dnsutils \
     && rm -rf /var/lib/apt/lists/*

Dockerfile.tailscale-HEAD

@@ -0,0 +1,21 @@
+FROM golang:latest
+
+RUN apt-get update \
+    && apt-get install -y ca-certificates dnsutils git \
+    && rm -rf /var/lib/apt/lists/*
+
+
+RUN git clone https://github.com/tailscale/tailscale.git
+
+WORKDIR tailscale
+
+RUN sh build_dist.sh tailscale.com/cmd/tailscale
+RUN sh build_dist.sh tailscale.com/cmd/tailscaled
+
+RUN cp tailscale /usr/local/
+RUN cp tailscaled /usr/local/
+
+ADD integration_test/etc_embedded_derp/tls/server.crt /usr/local/share/ca-certificates/
+RUN chmod 644 /usr/local/share/ca-certificates/server.crt 
+
+RUN update-ca-certificates

integration_common_test.go

@@ -20,7 +20,7 @@ var (
 	IpPrefix4 = netaddr.MustParseIPPrefix("100.64.0.0/10")
 	IpPrefix6 = netaddr.MustParseIPPrefix("fd7a:115c:a1e0::/48")
 
-	tailscaleVersions = []string{"1.22.0", "1.20.4", "1.18.2", "1.16.2", "1.14.3", "1.12.3"}
+	tailscaleVersions = []string{"HEAD", "unstable", "1.22.0", "1.20.4", "1.18.2", "1.16.2", "1.14.3", "1.12.3"}
 )
 
 type TestNamespace struct {
@@ -128,6 +128,49 @@ func DockerAllowNetworkAdministration(config *docker.HostConfig) {
 	})
 }
 
+func getDockerBuildOptions(version string) *dockertest.BuildOptions {
+	var tailscaleBuildOptions *dockertest.BuildOptions
+	switch version {
+	case "HEAD":
+		tailscaleBuildOptions = &dockertest.BuildOptions{
+			Dockerfile: "Dockerfile.tailscale-HEAD",
+			ContextDir: ".",
+			BuildArgs:  []docker.BuildArg{},
+		}
+	case "unstable":
+		tailscaleBuildOptions = &dockertest.BuildOptions{
+			Dockerfile: "Dockerfile.tailscale",
+			ContextDir: ".",
+			BuildArgs: []docker.BuildArg{
+				{
+					Name:  "TAILSCALE_VERSION",
+					Value: "*", // Installs the latest version https://askubuntu.com/a/824926
+				},
+				{
+					Name:  "TAILSCALE_CHANNEL",
+					Value: "unstable",
+				},
+			},
+		}
+	default:
+		tailscaleBuildOptions = &dockertest.BuildOptions{
+			Dockerfile: "Dockerfile.tailscale",
+			ContextDir: ".",
+			BuildArgs: []docker.BuildArg{
+				{
+					Name:  "TAILSCALE_VERSION",
+					Value: version,
+				},
+				{
+					Name:  "TAILSCALE_CHANNEL",
+					Value: "stable",
+				},
+			},
+		}
+	}
+	return tailscaleBuildOptions
+}
+
 func getIPs(
 	tailscales map[string]dockertest.Resource,
 ) (map[string][]netaddr.IP, error) {

integration_embedded_derp_test.go

@@ -245,16 +245,8 @@ func (s *IntegrationDERPTestSuite) Join(
 
 func (s *IntegrationDERPTestSuite) tailscaleContainer(identifier, version string, network dockertest.Network,
 ) (string, *dockertest.Resource) {
-	tailscaleBuildOptions := &dockertest.BuildOptions{
+	tailscaleBuildOptions := getDockerBuildOptions(version)
-		Dockerfile: "Dockerfile.tailscale",
+
-		ContextDir: ".",
-		BuildArgs: []docker.BuildArg{
-			{
-				Name:  "TAILSCALE_VERSION",
-				Value: version,
-			},
-		},
-	}
 	hostname := fmt.Sprintf(
 		"tailscale-%s-%s",
 		strings.Replace(version, ".", "-", -1),

integration_test.go

@@ -168,16 +168,8 @@ func (s *IntegrationTestSuite) Join(
 func (s *IntegrationTestSuite) tailscaleContainer(
 	namespace, identifier, version string,
 ) (string, *dockertest.Resource) {
-	tailscaleBuildOptions := &dockertest.BuildOptions{
+	tailscaleBuildOptions := getDockerBuildOptions(version)
-		Dockerfile: "Dockerfile.tailscale",
+
-		ContextDir: ".",
-		BuildArgs: []docker.BuildArg{
-			{
-				Name:  "TAILSCALE_VERSION",
-				Value: version,
-			},
-		},
-	}
 	hostname := fmt.Sprintf(
 		"%s-tailscale-%s-%s",
 		namespace,