New program netcheck to check if network overlaps routes

.gitignore

@@ -35,6 +35,7 @@ prog/weavedns/weavedns
 prog/weaveproxy/weaveproxy
 prog/sigproxy/sigproxy
 prog/weavewait/weavewait
+prog/netcheck/netcheck
 tools/bin
 tools/build
 releases
@@ -45,6 +46,7 @@ prog/weaveexec/weave
 prog/weaveexec/weaveproxy
 prog/weaveexec/weavewait
 prog/weaveexec/sigproxy
+prog/weaveexec/netcheck
 prog/weaveexec/docker*.tgz
 Vagrantfile.local
 test/tls/*.pem

Makefile

@@ -14,8 +14,9 @@ WEAVEDNS_EXE=prog/weavedns/weavedns
 WEAVEPROXY_EXE=prog/weaveproxy/weaveproxy
 SIGPROXY_EXE=prog/sigproxy/sigproxy
 WEAVEWAIT_EXE=prog/weavewait/weavewait
+NETCHECK_EXE=prog/netcheck/netcheck
 
-EXES=$(WEAVER_EXE) $(WEAVEDNS_EXE) $(SIGPROXY_EXE) $(WEAVEPROXY_EXE) $(WEAVEWAIT_EXE)
+EXES=$(WEAVER_EXE) $(WEAVEDNS_EXE) $(SIGPROXY_EXE) $(WEAVEPROXY_EXE) $(WEAVEWAIT_EXE) $(NETCHECK_EXE)
 
 WEAVER_IMAGE=$(DOCKERHUB_USER)/weave
 WEAVEDNS_IMAGE=$(DOCKERHUB_USER)/weavedns
@@ -40,7 +41,7 @@ travis: $(EXES)
 update: $(EXES)
 	go get -u -f -v -tags -netgo $(addprefix ./,$(dir $(EXES)))
 
-$(WEAVER_EXE) $(WEAVEDNS_EXE) $(WEAVEPROXY_EXE): common/*.go common/*/*.go net/*.go
+$(WEAVER_EXE) $(WEAVEDNS_EXE) $(WEAVEPROXY_EXE) $(NETCHECK_EXE): common/*.go common/*/*.go net/*.go
 	go get -tags netgo ./$(@D)
 	go build -ldflags "-extldflags \"-static\" -X main.version $(WEAVE_VERSION)" -tags netgo -o $@ ./$(@D)
 	@strings $@ | grep cgo_stub\\\.go >/dev/null || { \
@@ -73,11 +74,12 @@ $(WEAVEDNS_EXPORT): prog/weavedns/Dockerfile $(WEAVEDNS_EXE)
 	$(SUDO) docker build -t $(WEAVEDNS_IMAGE) prog/weavedns
 	$(SUDO) docker save $(WEAVEDNS_IMAGE):latest > $@
 
-$(WEAVEEXEC_EXPORT): prog/weaveexec/Dockerfile $(DOCKER_DISTRIB) weave $(SIGPROXY_EXE) $(WEAVEPROXY_EXE) $(WEAVEWAIT_EXE)
+$(WEAVEEXEC_EXPORT): prog/weaveexec/Dockerfile $(DOCKER_DISTRIB) weave $(SIGPROXY_EXE) $(WEAVEPROXY_EXE) $(WEAVEWAIT_EXE) $(NETCHECK_EXE)
 	cp weave prog/weaveexec/weave
 	cp $(SIGPROXY_EXE) prog/weaveexec/sigproxy
 	cp $(WEAVEPROXY_EXE) prog/weaveexec/weaveproxy
 	cp $(WEAVEWAIT_EXE) prog/weaveexec/weavewait
+	cp $(NETCHECK_EXE) prog/weaveexec/netcheck
 	cp $(DOCKER_DISTRIB) prog/weaveexec/docker.tgz
 	$(SUDO) docker build -t $(WEAVEEXEC_IMAGE) prog/weaveexec
 	$(SUDO) docker save $(WEAVEEXEC_IMAGE):latest > $@

prog/netcheck/netcheck.go

@@ -0,0 +1,31 @@
+/* netcheck: check whether a given network overlaps with any existing routes */
+package main
+
+import (
+	"fmt"
+	"net"
+	"os"
+
+	weavenet "github.com/weaveworks/weave/net"
+)
+
+func fatal(err error) {
+	fmt.Println(err)
+	os.Exit(1)
+}
+
+func main() {
+	if len(os.Args) <= 1 {
+		os.Exit(0)
+	}
+
+	ipRangeStr := os.Args[1]
+	_, ipnet, err := net.ParseCIDR(ipRangeStr)
+	if err != nil {
+		fatal(err)
+	}
+	if err := weavenet.CheckNetworkFree(ipnet); err != nil {
+		fatal(err)
+	}
+	os.Exit(0)
+}

prog/weaveexec/Dockerfile

@@ -16,6 +16,7 @@ WORKDIR /home/weave
 ADD ./weave /home/weave/
 ADD ./sigproxy /home/weave/
 ADD ./weaveproxy /home/weave/
+ADD ./netcheck /usr/bin/
 ADD ./weavewait /w/w
 ADD ./docker.tgz /