Use a fixed (and old) version of the docker client

As noted in #388 comment 76958961, we need the docker client to be as
old as possible while supporting what weave needs to do. At the minute
that means version 1.3.1.

The `apk` package index does not have old versions of docker, so the
most direct way of getting a docker executable is to download the
specific version from https://get.docker.com.

.gitignore

@@ -36,3 +36,4 @@ releases
 weave.tar
 weavedns.tar
 weaveexec.tar
+weaveexec/docker*.tgz

Makefile

@@ -17,6 +17,10 @@ WEAVER_EXPORT=weave.tar
 WEAVEDNS_EXPORT=weavedns.tar
 WEAVEEXEC_EXPORT=weaveexec.tar
 
+WEAVEEXEC_DOCKER_VERSION=1.3.1
+DOCKER_DISTRIB=weaveexec/docker-$(WEAVEEXEC_DOCKER_VERSION).tgz
+DOCKER_DISTRIB_URL=https://get.docker.com/builds/Linux/x86_64/docker-$(WEAVEEXEC_DOCKER_VERSION).tgz
+
 all: $(WEAVER_EXPORT) $(WEAVEDNS_EXPORT) $(WEAVEEXEC_EXPORT)
 
 update:
@@ -45,11 +49,15 @@ $(WEAVEDNS_EXPORT): weavedns/Dockerfile $(WEAVEDNS_EXE)
 	$(SUDO) docker build -t $(WEAVEDNS_IMAGE) weavedns
 	$(SUDO) docker save $(WEAVEDNS_IMAGE):latest > $@
 
-$(WEAVEEXEC_EXPORT): weaveexec/Dockerfile weave
+$(WEAVEEXEC_EXPORT): weaveexec/Dockerfile $(DOCKER_DISTRIB) weave
 	cp weave weaveexec/weave
+	cp $(DOCKER_DISTRIB) weaveexec/docker.tgz
 	$(SUDO) docker build -t $(WEAVEEXEC_IMAGE) weaveexec
 	$(SUDO) docker save $(WEAVEEXEC_IMAGE):latest > $@
 
+$(DOCKER_DISTRIB):
+	curl -o $(DOCKER_DISTRIB) $(DOCKER_DISTRIB_URL)
+
 # Add more directories in here as more tests are created
 tests:
 	cd router; go test -cover -tags netgo

weaveexec/Dockerfile

@@ -1,7 +1,8 @@
 FROM gliderlabs/alpine
 MAINTAINER Weaveworks Inc <help@weave.works>
 WORKDIR /home/weave
-RUN ["apk", "add", "--update", "ethtool", "conntrack-tools", "curl", "iptables", "iproute2", "docker"]
+RUN ["apk", "add", "--update", "ethtool", "conntrack-tools", "curl", "iptables", "iproute2"]
 RUN ["sh", "-c", "rm -rf /var/cache/apk/*"]
 ADD ./weave /home/weave/
+ADD ./docker.tgz /
 ENTRYPOINT ["/home/weave/weave"]