usage() {
cat <<EOF
-usage: ${0##*/} [OPTS] start|stop NETNS_NAME
-
--c, --create Create network namespace. For running outside systemd private net.
+usage: ${0##*/} [OPTS] start|stop NS_NAME
+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 systemd network namespace, nat it to the outside. If given
--c, or if in the default network namespace, create a named network
-namepace natted to the current netns.
+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.
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:
-/usr/bin/nsenter --mount=/root/mount_namespaces/NETNS_NAME
-
+/usr/bin/nsenter --mount=/root/mount_namespaces/NS_NAME
-"ip netns new ..." also does a mount namespace, then bind mounts each
-thing in /etc/netns/NETNS_NAME to /etc/NETNS_NAME. Note, for openvpn having it's own
-resolv.conf, this doesn't help much. What we actually want to do is copy
-/run/resolvconf somehwere, then bind mount it on top of /run/resolvconf.
+Note, this means that they can't run as unpriveledged users, but once
+systemd 233 comes out, it will have a bind mount option from within unit
+files, so the mount namespace won't be needed for most use cases, and I
+will update the script to that the mount namespace not created unless a
+flag is passed in. Patch welcome to add that flag before then.
-Once systemd 233 comes out, it will have a bind mount option from within
-unit files, so the mount namespace won't be needed for this use case.
-
-Recommmended dependency of errhandle to print stack trace on error:
+A recommmended dependency of this script is my other repo named "errhandle",
+which prints stack trace on error, and calls a cleanup function:
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:
+
+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
+copy /run/resolvconf somehwere then bind mount it on top of
+/run/resolvconf.
+
+Please email me if you have a patches, bugs, feedback, or republish this
+somewhere else: Ian Kelling <ian@iankelling.org>.
EOF
exit ${1:-0}
}
-## begin arg parsing ##
+#### begin arg parsing ####
create=false
-temp=$(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 ;;
fi
action=$1
-nn=$2 # network namespace / namespace name
-## end arg parsing ##
-
-## begin sanity checking ##
+nn=$2 # namespace name
+#### end arg parsing ####
+#### begin sanity checking ####
install_error=false
if ! type -p ip &>/dev/null; then
echo "please install the iproute2 package"
if $install_error; then
exit 1
fi
-
-## end sanity checking ##
+#### end sanity checking ####
v0=veth0-$nn
create=true
fi
+# make the default network namespace be named
target=/run/netns/default
if [[ ! -e $target && ! -L $target ]]; then
mkdir -p /run/netns
- # make the default network namespace be named
ln -s /proc/1/ns/net $target
fi
dexec() { ip netns exec default "$@"; }
-# head -n1 is defensive. Not sure if there is some weird feature
+# background: head -n1 is defensive. Not sure if there is some weird feature
# for 2 routes to be 0/0.
-gateway_if=$(ipd route list exact 0/0 | head -n1| sed -r 's/.*\s(\S+)\s*$/\1/')
+gateway_if=$(ipd route list exact 0/0 | head -n1| sed -r 's/.*dev\s+(\S+).*/\1/')
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
}
start() {
-
find_network
if ! $found; then
echo "$0: error: no open network found"
exit 1
fi
+ #### begin mount namespace setup ####
mkdir -p /root/mount_namespaces
if ! mountpoint /root/mount_namespaces >/dev/null; then
mount --bind /root/mount_namespaces /root/mount_namespaces
- mount --make-private /root/mount_namespaces
fi
+ # note: This is outside the mount condition because I've mysteriously
+ # had this become shared instead of private, perhaps it
+ # got remounted somehow and lost the setting.
+ mount --make-private /root/mount_namespaces
if [[ ! -e /root/mount_namespaces/$nn ]]; then
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 ####
if $create; then
ip -n $nn link set dev lo up
fi
-
-
echo 1 | dexec dd of=/proc/sys/net/ipv4/ip_forward 2>/dev/null
_errcatch_cleanup=stop
if $create; then
ip netns del $nn
fi
+ if mountpoint /root/mount_namespaces/$nn >/dev/null; then
+ umount /root/mount_namespaces/$nn
+ fi
}
case $action in
iankelling.org / git / newns / blobdiff