Add DNS and network tools.

Author: DentonGentry

.devcontainer/Dockerfile

@@ -1,10 +1,12 @@
-# Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
+# Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
 # Use of this source code is governed by a BSD-style
 # license that can be found in the LICENSE file.
 
 FROM mcr.microsoft.com/vscode/devcontainers/universal:linux as builder
 USER root
 
+# Magic DNS in a container where /etc/resolv.conf is a bind mount needed
+# extra support, currently on a development branch.
 WORKDIR /go/src/tailscale
 COPY . ./
 RUN git clone https://github.com/tailscale/tailscale.git && cd tailscale && \
@@ -15,6 +17,7 @@ COPY . ./
 FROM mcr.microsoft.com/vscode/devcontainers/universal:linux
 USER root
 
+RUN apt-get update && apt-get install -y curl gpg dnsutils
 COPY tailscaled /etc/init.d
 COPY --from=builder /go/bin/tailscaled /usr/sbin/tailscaled
 COPY --from=builder /go/bin/tailscale /usr/bin/tailscale