From: Ian Kelling <iank@fsf.org>
Date: Sat, 4 Nov 2017 22:35:25 +0000 (-0400)
Subject: fix docker and stop command
X-Git-Url: https://iankelling.org/git/?p=newns;a=commitdiff_plain;h=b0239f31ed6ba299fbbde710c3ebb080bd5f8c12

fix docker and stop command
---

diff --git a/newns b/newns
index e4d1f86..cd2466b 100755
--- a/newns
+++ b/newns
@@ -74,11 +74,15 @@ in.
 
 Background:
 
-This script does not make the namespace be named like ip does, because
-the naming is not necessary, although it could have been done with some
-more work. For debugging and joining the namespace with a bash shell, I
-use nsenter -n -m -t \$(pgrep PROCESS_IN_NAMESPACE) bash.  Note: if I
-knew how to easily ask systemd what pid a unit has, i would do that.
+If we aren't creating a named network namespace, to join the namespace
+with a shell, I use:
+nsenter -n -m -t \$(pgrep PROCESS_IN_NAMESPACE) bash
+
+Note: if I knew how to easily ask systemd what pid a unit has, i would
+do that.
+
+If we do create the netns, to join it with a shell, we can do
+/usr/bin/nsenter --mount=/root/mount_namespaces/NAME --net=/var/run/netns/NAME bash
 
 "ip netns new ..." also does a mount namespace, then bind
 mounts each file/dir in /etc/netns/NS_NAME to /etc/NS_NAME. Note,
@@ -167,9 +171,28 @@ mexec() { /usr/bin/nsenter --mount=/root/mount_namespaces/$nn "$@"; }
 # background: head -n1 is defensive. Not sure if there is some weird feature
 # for 2 routes to be 0/0.
 gateway_if=$(ipd route list exact 0/0 | head -n1| sed -r 's/.*dev\s+(\S+).*/\1/')
+
+if [[ ! $gateway_if ]]; then
+    cat >&2 <<EOF
+$0: error: failed to find gateway interface. No output from:
+ipd route list exact 0/0 | head -n1| sed -r 's/.*dev\s+(\S+).*/\1/'
+output from "ipd route list exact 0/0":
+$(ipd route list exact 0/0)
+EOF
+    exit 1
+fi
+
 nat() { dexec iptables -t nat $1 POSTROUTING -o $gateway_if -j MASQUERADE \
               -m comment --comment "systemd network namespace nat"; }
 
+# d = default
+diptables-add() {
+    if ! dexec iptables -C "$@" &>/dev/null; then
+        dexec iptables -I "$@"
+    fi
+
+}
+
 find_network() {
     if [[ $network ]]; then
         return
@@ -208,6 +231,12 @@ start() {
         touch /root/mount_namespaces/$nn
     fi
     if ! mountpoint /root/mount_namespaces/$nn >/dev/null; then
+        # Here, we specify that we only want mount changes changes under
+        # this mountpoint to be propagated into the bind, but changes
+        # from within the bind do not propagate to outside the bind.
+        #
+        # slave is documented in.
+        # /usr/share/doc/linux-doc-4.9/Documentation/filesystems/sharedsubtree.txt.gz
         # documentation on propagation is a bit weird because it
         # confusingly talks about binds, namespaces, and mirrors (which
         # seems to be just another name for bind), shared subtrees
@@ -215,9 +244,7 @@ start() {
         # properly specify whether the documentation applies to binds,
         # namespaces, or both. Notably, propagation for binds is marked
         # on the original mount point, and propagation for a mount
-        # namespace is marked on mounts within the namespace.  Here, we
-        # specify that we want mount changes propagated to us, but not
-        # back.
+        # namespace is marked on mounts within the namespace.
         unshare --propagation slave --mount=/root/mount_namespaces/$nn /bin/true
     fi
 
@@ -232,9 +259,9 @@ start() {
     echo 1 | dexec dd of=/proc/sys/net/ipv4/ip_forward 2>/dev/null
 
     # docker helpfully changes the default FORWARD to drop...
-    if ! dexec iptables -C FORWARD -i $v0 -j ACCEPT &>/dev/null; then
-        dexec iptables -A FORWARD -i $v0 -j ACCEPT
-    fi
+    diptables-add FORWARD -i $v0 -j ACCEPT
+    diptables-add FORWARD -o $v0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
+
 
     _errcatch_cleanup=stop
     ipnn link add $v0 type veth peer name $v1
@@ -285,7 +312,7 @@ stop() {
         if nat -C &>/dev/null; then nat -D; fi
     fi
     dexec iptables -D FORWARD -i $v0 -j ACCEPT ||:
-    if $create; then
+    if $create && [[ -e /var/run/netns/client ]]; then
         ip netns del $nn
     fi