From d1896e86d03e9da712aa816c091cc30e6038fd46 Mon Sep 17 00:00:00 2001
From: Bryan Boreham <bjboreham@gmail.com>
Date: Tue, 23 Sep 2014 13:01:21 +0100
Subject: [PATCH] Redesigned attach/detach

---
 weaver/weave | 73 ++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 51 insertions(+), 22 deletions(-)

diff --git a/weaver/weave b/weaver/weave
index 7340dc3f..589a2710 100755
--- a/weaver/weave
+++ b/weaver/weave
@@ -103,7 +103,7 @@ stop_masquerading() {
 }
 
 # the following borrows from https://github.com/jpetazzo/pipework
-find_container_pid() {
+container_netns_preamble() {
     DOCKERPID=$(docker inspect --format='{{ .State.Pid }}' $1)
     [ "$DOCKERPID" = 0 ] && {
         echo "Container $1 not running." >&2
@@ -113,20 +113,40 @@ find_container_pid() {
         echo "Container $1 unknown to Docker." >&2
         exit 1
     }
-    return 0
-}
 
-configure_container_networking() {
-    find_container_pid $1
     NSPID=$DOCKERPID
 
     [ ! -d /var/run/netns ] && mkdir -p /var/run/netns
     rm -f /var/run/netns/$NSPID
     ln -s /proc/$NSPID/ns/net /var/run/netns/$NSPID
-
-    EXITCODE=1
     LOCAL_IFNAME="v${CONTAINER_IFNAME}pl${NSPID}"
     GUEST_IFNAME="v${CONTAINER_IFNAME}pg${NSPID}"
+
+    return 0
+}
+
+container_netns_cleanup() {
+    rm -f /var/run/netns/$NSPID
+}
+
+# Parameters are container ID, CIDR address
+configure_container_networking() {
+    container_netns_preamble $1
+
+    EXITCODE=1
+
+    # If veth name already exists then assume we set it up already;
+    # just add the IP address
+    if ip link show $LOCAL_IFNAME >/dev/null 2>&1 ; then
+        if ip netns exec $NSPID ip addr add $2 dev $CONTAINER_IFNAME ; then
+            EXITCODE=0
+        else
+            echo "Failed to attach address $2 to container $1" >&2
+        fi
+        container_netns_cleanup
+        return $EXITCODE
+    fi
+
     IP_TMPFILE=/tmp/weave_ip_output_$$
     rm -f $IP_TMPFILE
     if ip link add name $LOCAL_IFNAME mtu $MTU type veth peer name $GUEST_IFNAME mtu $MTU >$IP_TMPFILE 2>&1 ; then
@@ -155,18 +175,33 @@ configure_container_networking() {
     fi
 
     rm -f $IP_TMPFILE
-    rm -f /var/run/netns/$NSPID
+    container_netns_cleanup
 
     return $EXITCODE
 }
 
-takedown_container_networking() {
-    find_container_pid $1
-    NSPID=$DOCKERPID
+# Parameters are container ID, CIDR address, interface-name
+detach() {
+    container_netns_preamble $1
 
-    LOCAL_IFNAME="v${CONTAINER_IFNAME}pl${NSPID}"
+    EXITCODE=1
+    if ip netns exec $NSPID ip addr del $2 dev $CONTAINER_IFNAME ; then
+        # if no inet addresses remain then delete the veth
+        if [ $(ip netns exec $NSPID ip -f inet addr show dev ethwe | wc -c) -eq 0 ] ; then
+            if ip link del $LOCAL_IFNAME type veth ; then
+                EXITCODE=0
+            else
+                echo "Failed to delete virtual ethernet device $LOCAL_IFNAME from container $1" >&2
+            fi
+        else
+            EXITCODE=0
+        fi
+    else
+        echo "Failed to detach address $2 from container $1" >&2
+    fi
 
-    ip link del $LOCAL_IFNAME type veth || true
+    container_netns_cleanup
+    return $EXITCODE
 }
 
 case "$COMMAND" in
@@ -244,18 +279,12 @@ case "$COMMAND" in
         ;;
     attach)
         [ $# -gt 1 ] || usage
-        IPADDR=$1
-        shift 1
         create_bridge
-        CONTAINER=$1
-        shift 1
-        configure_container_networking $CONTAINER $IPADDR $CONTAINER_IFNAME
+        configure_container_networking $2 $1 $CONTAINER_IFNAME
         ;;
     detach)
-        [ $# -gt 0 ] || usage
-        CONTAINER=$1
-        shift 1
-        takedown_container_networking $CONTAINER
+        [ $# -gt 1 ] || usage
+        detach $2 $1
         ;;
     expose)
         [ $# -gt 0 ] || usage