X-Git-Url: https://iankelling.org/git/?a=blobdiff_plain;f=newns;h=76c7adf53c6aa4b623572eeb3cb07227f7cfbecb;hb=b9cf4000a50a83b7f757212030e18b00104ab01f;hp=6da77278eedc873e0f97babb4ad3367d5b24aff8;hpb=49df8bd697275ea5d331efc114440a0fde964935;p=newns

diff --git a/newns b/newns
index 6da7727..76c7adf 100755
--- a/newns
+++ b/newns
@@ -38,21 +38,20 @@ fi
 usage() {
     cat <<EOF
 usage: ${0##*/} [OPTS] start|stop NS_NAME
-Setup new or systemd created network namespace with nat and mount namespace
-
--c, --create    Create network namespace. For running outside systemd private net.
+Nat a network namespace. create a mount ns. systemd friendly
+
+-c, --create    Create a named network namespace. When running from
+                the same network namespace as pid 1, this is set automatically.
+                This is the case when running outside a systemd created
+                private network.
+-n NETWORK      x.x.x /24 private network to use. If not specified, uses
+                the first one starting at 10.173.1
 -h, --help      Show this help and exit.
 
 From within a systemd network namespace, nat it to the outside. This
 would be called from ExecStartPre, and or subsequent units called with
 JoinsNamespaceOf= and PrivateNetwork=true.
 
-If given -c, or if in the default network namespace, create a named
-network namepace natted to the current netns.
-
-Uses /24 network, finding the first locally unused one starting at
-10.173.0.
-
 Also create a named mount namespace under /root/mount_namespaces, so we
 can alter some system config for this namespace. Subsequent systemd
 command lines would be prefixed with:
@@ -71,7 +70,15 @@ https://iankelling.org/git/?p=errhandle, set ERRHANDLE_PATH, or put it
 in a directory adjacent to the absolute, resolved directory this file is
 in.
 
-Background: "ip netns new ..." also does a mount namespace, then bind
+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.
+
+"ip netns new ..." also does a mount namespace, then bind
 mounts each file/dir in /etc/netns/NS_NAME to /etc/NS_NAME. Note,
 for openvpn having it's own resolv.conf by using it's user script which
 calls resolvconf, this doesn't help much. What we actually want to do is
@@ -87,11 +94,12 @@ EOF
 
 #### begin arg parsing ####
 create=false
-temp=$(getopt -l help,create hc "$@") || usage 1
+temp=$(getopt -l help,create hcn: "$@") || usage 1
 eval set -- "$temp"
 while true; do
     case $1 in
         -c|--create) create=true; shift ;;
+        -n) network=$2; shift 2 ;;
         -h|--help) usage ;;
         --) shift; break ;;
         *) echo "$0: Internal error!" ; exit 1 ;;
@@ -154,10 +162,13 @@ nat() { dexec iptables -t nat $1 POSTROUTING -o $gateway_if -j MASQUERADE \
               -m comment --comment "systemd network namespace nat"; }
 
 find_network() {
+    if [[ $network ]]; then
+        return
+    fi
     found=false
     existing=false
     ips="$(ipd addr show | awk '$1 == "inet" {print $2}')"
-    for ((i=0; i <= 254; i++)); do
+    for ((i=1; i <= 254; i++)); do
         network=$ip_base.$i
         if printf "%s\n" "$ips" | grep "^${network//./\\.}" >/dev/null; then
             existing=true
@@ -185,7 +196,17 @@ start() {
         touch /root/mount_namespaces/$nn
     fi
     if ! mountpoint /root/mount_namespaces/$nn >/dev/null; then
-        unshare --mount=/root/mount_namespaces/$nn
+        # 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
+        # (which seems to a term for binds and namespaces), and does not
+        # 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.
+        unshare --propagation slave --mount=/root/mount_namespaces/$nn
     fi
     ####   end mount namespace setup ####