From 6b15ac48b3f675a208d18bb267b82305eb8c8457 Mon Sep 17 00:00:00 2001
From: Ian Kelling <iank@fsf.org>
Date: Thu, 23 May 2019 14:12:33 -0400
Subject: [PATCH] better docs and make err a hard dependency

---
 .gitignore |  1 +
 newns      | 59 ++++++++++++++++++++++++++++++------------------------
 2 files changed, 34 insertions(+), 26 deletions(-)
 create mode 100644 .gitignore

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..02b2e8d
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/err
\ No newline at end of file
diff --git a/newns b/newns
index ad4c06c..a2d896d 100755
--- a/newns
+++ b/newns
@@ -16,23 +16,19 @@
 
 [[ $EUID == 0 ]] || exec sudo -E "$BASH_SOURCE" "$@"
 
+tmp="$(readlink -f "${BASH_SOURCE}")"; script_dir="${tmp%/*}"
 if [[ ! $ERRHANDLE_PATH ]]; then
-  ERRHANDLE_PATH=$(readlink -f "${BASH_SOURCE}")
-  ERRHANDLE_PATH=$(readlink -f ${ERRHANDLE_PATH%/*}/../errhandle)
+  ERRHANDLE_PATH="$script_dir"/../errhandle/err
 fi
-err_sourced=true
-for p in $ERRHANDLE_PATH/{errcatch-function,bash-trace-function}; do
-  if [[ -e $p ]]; then
-    source $p
-  else
-    err_sourced=false
-  fi
-done
-if $err_sourced; then
-  errcatch
+if [[ -s $ERRHANDLE_PATH ]]; then
+  source $ERRHANDLE_PATH
 else
-  set -eE -o pipefail
-  trap 'echo "$0:$LINENO:error: \"$BASH_COMMAND\" returned $?" >&2' ERR
+  cd "$script_dir"
+  if ! wget -O err 'https://iankelling.org/git/?p=errhandle;a=blob_plain;f=err;hb=HEAD'; then
+    echo "$0: failed to get errhandle dependency" >&2
+    exit 1
+  fi
+  source err
 fi
 
 usage() {
@@ -50,12 +46,22 @@ Also creates a mount namespace with a cloned /run/resolvconf.
                 the first unused 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
+From a normal shell:
+
+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
+
+If you dont care about the mount namespace, you can leave that option off.
+
+
+For systemd:
+
+From within a systemd network namespace, we 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
+We also create a named mount namespace under /root/mount_namespaces, so we
+can alter some system config for this namespace. systemd
 command lines would be prefixed with:
 
 /usr/bin/nsenter --mount=/root/mount_namespaces/NS_NAME
@@ -66,13 +72,16 @@ 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.
 
-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.
+This script has a dependency which you can download manually or it
+will be automatically downloaded into the same directory.
+It handles errors by printing stack trace and and cleaning up the namespaces.
+To download manually,
+git clone https://iankelling.org/git/errhandle
+into an adjacent directory, or
+export ERRHANDLE_PATH to point to the 'err' file in that repo.
+
 
-Background:
+Background on this project (you can skip if you like):
 
 If we aren't creating a named network namespace, to join the namespace
 with a shell, I use:
@@ -81,9 +90,6 @@ 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,
 for openvpn having it's own resolv.conf by using it's user script which
@@ -91,6 +97,7 @@ 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.
 
+
 Note: for debugging, adding set -x is a pretty good option.
 
 Please email me if you have a patches, bugs, feedback, or republish this
-- 
2.30.2