From 8500a256d3d7c198fd5859f4464dd4d8f25eae93 Mon Sep 17 00:00:00 2001
From: Erich Eckner <git@eckner.net>
Date: Wed, 19 Dec 2018 11:23:02 +0100
Subject: initial commit

---
 dd-resume | 137 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 137 insertions(+)
 create mode 100755 dd-resume

diff --git a/dd-resume b/dd-resume
new file mode 100755
index 0000000..848c459
--- /dev/null
+++ b/dd-resume
@@ -0,0 +1,137 @@
+#!/bin/bash
+
+# copy resumably with dd via network
+
+script_name=$(basename "$0")
+
+usage() {
+  >&2 printf 'usage:\n'
+  >&2 printf '  %s in-host in-dev out-dev log-file\n' "${script_name}"
+  >&2 printf '  %s -s in-dev start-position remote-port\n' "${script_name}"
+  exit 1
+}
+
+dd_options='bs=1M'
+
+for needed in dd nc ss screen pgrep kill ssh; do
+  if ! which "${needed}" >/dev/null; then
+    >&2 printf 'please install required program %s\n' "${needed}"
+    exit 1
+  fi
+done
+
+if [ "x$1" = 'x-s' ]; then
+  shift
+  if [ $# -ne 3 ]; then
+    >&2 printf 'expected 3 arguments, got %s:\n' "$#"
+    >&2 printf '"%s" ' "$@"
+    >&2 printf '\n'
+    usage
+  fi
+  dev="$1"
+  start="$2"
+  remote_ip="${SSH_CLIENT%% *}"
+  if [ -z "${remote_ip}" ]; then
+    >&2 printf 'cannot obtain remote ip\n'
+    exit 1
+  fi
+  remote_port="$3"
+  if [ ! -r "${dev}" ]; then
+    >&2 printf 'cannot read from %s\n\n' "${dev}"
+    usage
+  fi
+  set +o pipefail
+  dd if="${dev}" ${dd_options} skip="${start}" 2>/dev/null | \
+    nc -cn "${remote_ip}" "${remote_port}"
+  exit $?
+fi
+
+if [ $# -ne 4 ]; then
+  usage
+fi
+remote_host="$1"
+remote_dev="$2"
+local_dev="$3"
+log_file="$4"
+
+if [ ! -w "${log_file%/*}" ] && [ ! -w "${log_file}" ]; then
+  >&2 printf 'cannot write/create log-file %s\n\n' "${log_file}"
+  usage
+fi
+
+if [ ! -w "${local_dev}" ]; then
+  >&2 printf 'cannot write to out-dev %s\n\n' "${local_dev}"
+  usage
+fi
+
+start=0
+if [ -f "${log_file}" ]; then
+  start=$(
+    sed -n '
+      1 {
+        s/^start: //
+        p
+        q
+      }
+    ' "${log_file}"
+  )
+  copied=$(
+    sed '
+      s/^\([0-9]\+\)+0 records out$/\1/
+      t
+      d
+    ' "${log_file}" | \
+    sort -n | \
+    tail -n1
+  )
+  if [ -n "${copied}" ]; then
+    start=$((start+copied))
+  fi
+fi
+
+if pgrep -ax dd || pgrep -ax nc; then
+  >&2 printf 'another dd or nc is already running - this won'"'"'t work\n'
+  exit 1
+fi
+
+printf 'start: %s\n' "${start}" > \
+  "${log_file}"
+
+screen -d -m bash -c '
+  set +o pipefail
+  nc -l -c | \
+    dd of="'"${local_dev}"'" '"${dd_options}"' seek='"${start}"' 2>>"'"${log_file}"'" >/dev/null
+  printf '"'"'\nwrite-pipe-exit: %s\n'"'"' $? >>"'"${log_file}"'"
+'
+
+for i in {1..20}; do
+  if [ -n "${port}" ]; then
+    break
+  elif [ ${i} -gt 1 ]; then
+    sleep 0.1
+  fi
+  nc_pid=$(
+    pgrep -x nc
+  )
+  dd_pid=$(
+    pgrep -x dd
+  )
+  port=$(
+    ss -nlp | \
+      grep -F ",pid=${nc_pid}," | \
+      awk '{print $5}' | \
+      sed 's/^.*://'
+  )
+done
+if [ -z "${port}" ]; then
+  >&2 printf 'could not determine listening port\n'
+  exit 1
+fi
+screen -d -m bash -c '
+  while kill -SIGUSR1 '"${dd_pid}"'; do
+    sleep 1
+  done
+'
+
+ssh "${remote_host}" "${script_name} -s ${remote_dev} ${start} ${port}"
+printf '\nssh-exit: %s\n' $? >>"${log_file}"
-- 
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