Always use host netns

[awh]

Fixes #1589,#1746.

This PR currently depends on an as yet unmerged change in mesh (weaveworks/mesh#5); that should be merged first and this PR rebased accordingly.

[awh]

Addressed comments and updated mesh dependency.

[rade]

I think connect_container_to_bridge can be simplified now that it only gets called for application containers and hence always operates on a proper netns. In particular the interface 'down'ing (and elaborate explanatory comment) should no longer be necessary.

[rade]

The old multiweave lets one launch additional peers, and also stop just some of the peers, by setting FIRST_WEAVE, e.g.

NUM_WEAVES=10 bin/multiweave launch
FIRST_WEAVE=11 NUM_WEAVES=10 bin/multiweave launch
FIRST_WEAVE=11 NUM_WEAVES=10 bin/multiweave stop

This is no longer possible since a) 'launch' will trip over the multiweave bridge creation, and b) 'stop' will remove the bridge even though there are still weaves connected to it.

Suggested fix:

• only create multiweave bridge if it doesn't exist already
• remove ip addresses from multiweave when stopping individual weaves, and only delete multweave if there are no more addresses left

[rade]

The old multiweave lets one launch additional peers, and also stop just some of the peers, by setting FIRST_WEAVE

...and now so does the new multiweave.

[rade]

For posterity, here is a patch to multiweave that makes it use just distinct ports instead of IPs. This does work but results in some "connection shutting down due to error: cannot connect to ourself" noise.

diff --git a/bin/multiweave b/bin/multiweave
index 40654b4..090776e 100755
--- a/bin/multiweave
+++ b/bin/multiweave
@@ -15,8 +15,6 @@ START=${FIRST_WEAVE:-1}
 COUNT=${NUM_WEAVES:-28}
 FINISH=$((START+COUNT-1))

-SUBNET=192.168.7
-
 weavedir=$(dirname $0)/..

 # Generate a random MAC value - copied from 'weave' script
@@ -30,24 +28,21 @@ random_mac() {
 weave() {
     i=$1
     shift
-    WEAVE_CONTAINER_NAME=weave$i WEAVE_HTTP_ADDR=$SUBNET.$i:6784 $weavedir/weave "$@"
+    WEAVE_CONTAINER_NAME=weave$i WEAVE_HTTP_ADDR=127.0.0.1:$((6000+i)) WEAVE_PORT=$((5000+i)) $weavedir/weave "$@"
 }

 case "$1" in
     launch)
         shift 1
         echo $(date -R) launching
-        ip link show multiweave >/dev/null 2>&1 || sudo ip link add name multiweave type bridge
         for i in $(seq $START $FINISH); do
-            IP=$SUBNET.$i
-            sudo ip addr add $IP/24 dev multiweave
-            weave $i launch-router --datapath '' --iface '' --no-dns --host $IP \
+            weave $i launch-router --datapath '' --iface '' --no-dns --port $((5000+i)) \
                 --name $(random_mac) --nickname weave$i "$@"
         done
         echo $(date -R) connecting
         [ $START -gt 1 ] || START=2
         for i in $(seq $START $FINISH); do
-            TO=$SUBNET.$((i-1))
+            TO=localhost:$((5000+i-1))
             echo connecting weave$i to $TO
             weave $i connect $TO
         done
@@ -55,12 +50,9 @@ case "$1" in
         ;;
     stop)
         for i in $(seq $FINISH -1 $START); do
-            IP=$SUBNET.$i
             echo Stopping weave$i
             weave $i stop-router
-            sudo ip addr del $IP/24 dev multiweave || true
         done
-        [ -z "$(ip -4 -o addr show multiweave)" ] && sudo ip link del multiweave
         ;;
     *)
             weave "$@"