Merge pull request #1079 from weaveworks/68-rewrite-etc-hosts

LGTM.  Closes #68, with remainder to #1122

prog/weaveproxy/main.go

@@ -52,6 +52,7 @@ func main() {
 	mflag.StringVar(&logLevel, []string{"-log-level"}, "info", "logging level (debug, info, warning, error)")
 	ListVar(&c.ListenAddrs, []string{"H"}, defaultListenAddrs, "addresses on which to listen")
 	mflag.BoolVar(&c.NoDefaultIPAM, []string{"#-no-default-ipam", "-no-default-ipalloc"}, false, "do not automatically allocate addresses for containers without a WEAVE_CIDR")
+	mflag.BoolVar(&c.NoRewriteHosts, []string{"no-rewrite-hosts"}, false, "do not automatically rewrite /etc/hosts. Use if you need the docker IP to remain in /etc/hosts")
 	mflag.StringVar(&c.TLSConfig.CACert, []string{"#tlscacert", "-tlscacert"}, "", "Trust certs signed only by this CA")
 	mflag.StringVar(&c.TLSConfig.Cert, []string{"#tlscert", "-tlscert"}, "", "Path to TLS certificate file")
 	mflag.BoolVar(&c.TLSConfig.Enabled, []string{"#tls", "-tls"}, false, "Use TLS; implied by --tls-verify")

prog/weavewait/main.go

@@ -1,32 +1,56 @@
 package main
 
 import (
+	"bufio"
+	"bytes"
 	"fmt"
+	"io/ioutil"
+	"net"
 	"os"
 	"os/exec"
 	"os/signal"
+	"sort"
+	"strings"
 	"syscall"
 
-	"github.com/weaveworks/weave/net"
+	weavenet "github.com/weaveworks/weave/net"
 )
 
 func main() {
 	if len(os.Args) <= 1 {
 		os.Exit(0)
 	}
-	args := os.Args[1:]
+
+	var (
+		args         = os.Args[1:]
+		notInExec    = true
+		rewriteHosts = true
+	)
 
 	if args[0] == "-s" {
+		notInExec = false
+		rewriteHosts = false
 		args = args[1:]
-	} else {
+	}
+
+	if args[0] == "-h" {
+		rewriteHosts = false
+		args = args[1:]
+	}
+
+	if notInExec {
 		usr2 := make(chan os.Signal)
 		signal.Notify(usr2, syscall.SIGUSR2)
 		<-usr2
 	}
 
-	_, err := net.EnsureInterface("ethwe", -1)
+	iface, err := weavenet.EnsureInterface("ethwe", -1)
 	checkErr(err)
 
+	if rewriteHosts {
+		updateHosts(iface)
+	}
+
 	binary, err := exec.LookPath(args[0])
 	checkErr(err)
 
@@ -39,3 +63,92 @@ func checkErr(err error) {
 		os.Exit(1)
 	}
 }
+
+func updateHosts(iface *net.Interface) {
+	addrs, err := iface.Addrs()
+	checkErr(err)
+	if len(addrs) == 0 {
+		return
+	}
+	hostname, err := os.Hostname()
+	checkErr(err)
+
+	hosts := parseHosts()
+
+	// Remove existing ips pointing to our hostname
+	toRemove := []string{}
+	for ip, addrs := range hosts {
+		for _, addr := range addrs {
+			if addr == hostname {
+				toRemove = append(toRemove, ip)
+				break
+			}
+		}
+	}
+	for _, ip := range toRemove {
+		delete(hosts, ip)
+	}
+
+	// Add the weave ip(s)
+	for _, addr := range addrs {
+		if addr, ok := addr.(*net.IPNet); ok {
+			ip := addr.IP.String()
+			hosts[ip] = append(hosts[ip], hostname)
+		}
+	}
+
+	writeHosts(hosts)
+}
+
+func parseHosts() map[string][]string {
+	f, err := os.Open("/etc/hosts")
+	checkErr(err)
+	defer f.Close()
+	ips := map[string][]string{}
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		line := scanner.Text()
+
+		// Remove any comments
+		if i := strings.IndexByte(line, '#'); i != -1 {
+			line = line[:i]
+		}
+
+		fields := strings.Fields(line)
+		if len(fields) > 0 {
+			ips[fields[0]] = append(ips[fields[0]], fields[1:]...)
+		}
+	}
+	checkErr(scanner.Err())
+	return ips
+}
+
+func writeHosts(contents map[string][]string) {
+	ips := []string{}
+	for ip := range contents {
+		ips = append(ips, ip)
+	}
+	sort.Strings(ips)
+
+	buf := &bytes.Buffer{}
+	fmt.Fprintln(buf, "# modified by weave")
+	for _, ip := range ips {
+		if addrs := contents[ip]; len(addrs) > 0 {
+			fmt.Fprintf(buf, "%s\t%s\n", ip, strings.Join(uniqueStrs(addrs), " "))
+		}
+	}
+	checkErr(ioutil.WriteFile("/etc/hosts", buf.Bytes(), 644))
+}
+
+func uniqueStrs(s []string) []string {
+	m := map[string]struct{}{}
+	result := []string{}
+	for _, str := range s {
+		if _, ok := m[str]; !ok {
+			m[str] = struct{}{}
+			result = append(result, str)
+		}
+	}
+	sort.Strings(result)
+	return result
+}

proxy/create_container_interceptor.go

@@ -92,7 +92,11 @@ func (i *createContainerInterceptor) setWeaveWaitEntrypoint(container *docker.Co
 	}
 
 	if len(container.Entrypoint) == 0 || container.Entrypoint[0] != weaveWaitEntrypoint[0] {
-		container.Entrypoint = append(weaveWaitEntrypoint, container.Entrypoint...)
+		entrypoint := weaveWaitEntrypoint
+		if i.proxy.NoRewriteHosts {
+			entrypoint = append(entrypoint, "-h")
+		}
+		container.Entrypoint = append(entrypoint, container.Entrypoint...)
 	}
 
 	return nil

proxy/proxy.go

@@ -29,12 +29,13 @@ var (
 )
 
 type Config struct {
-	ListenAddrs   []string
-	NoDefaultIPAM bool
-	TLSConfig     TLSConfig
-	Version       string
-	WithDNS       bool
-	WithoutDNS    bool
+	ListenAddrs    []string
+	NoDefaultIPAM  bool
+	NoRewriteHosts bool
+	TLSConfig      TLSConfig
+	Version        string
+	WithDNS        bool
+	WithoutDNS     bool
 }
 
 type Proxy struct {

test/610_proxy_wait_for_weave_test.sh

@@ -19,4 +19,7 @@ COMMITTED_IMAGE=$(proxy docker_on $HOST1 commit c1)
 assert_raises "proxy docker_on $HOST1 run --name c2 $COMMITTED_IMAGE"
 assert "entrypoint c2" "$(entrypoint $COMMITTED_IMAGE)"
 
+# Check weave IP is first ip returned, so java (etc) prefer weave.
+assert "proxy docker_on $HOST1 run -e 'WEAVE_CIDR=10.2.1.1/24' $BASE_IMAGE hostname -i | cut -d' ' -f1" "10.2.1.1"
+
 end_suite

weave

@@ -36,7 +36,7 @@ weave launch-router [--password <password>] [--nickname <nickname>]
                       [--no-discovery] [--init-peer-count <count>] <peer> ...
 weave launch-dns    [<addr>]
 weave launch-proxy  [-H <endpoint>] [--with-dns | --without-dns]
-                      [--no-default-ipalloc]
+                      [--no-default-ipalloc] [--no-rewrite-hosts]
 weave connect       [--replace] [<peer> ...]
 weave forget        <peer> ...
 weave run           [--with-dns | --without-dns] [<addr> ...]