From 8ad148b34b2af334e4705ddf21cb602757d2c536 Mon Sep 17 00:00:00 2001
From: Andrew Engelbrecht <andrew@engelbrecht.io>
Date: Fri, 15 Oct 2021 01:24:12 -0400
Subject: [PATCH] send protocol version # for checking compatibility

the protocol version number allows us to print errors about mismatched
versions if the client-server API changes in the future
---
 kaya        | 4 ++++
 kaya-client | 8 ++++++++
 2 files changed, 12 insertions(+)

diff --git a/kaya b/kaya
index 17e6e33..41a44cb 100755
--- a/kaya
+++ b/kaya
@@ -24,6 +24,9 @@ set -eE -o pipefail
 trap 'echo "$0:$LINENO:error: \"$BASH_COMMAND\" exit status: $?, PIPESTATUS: ${PIPESTATUS[*]}" >&2' ERR
 
 
+# first stable version of API between kaya and kaya-client
+kaya_protocol_version=1
+
 kaya-usage() {
     cat << EOF >&2
 
@@ -134,6 +137,7 @@ start-backup() {
     # make the backup over a forwarded port
     cat << EOF | ssh -R "${remote_port}:localhost:${local_port}" "${remote_user}@${hostname}" kaya-client \
         "${remote_port@Q}" "${hostname@Q}" "${backup_options[@]@Q}"
+${kaya_protocol_version}
 ${password}
 EOF
 
diff --git a/kaya-client b/kaya-client
index e57cd61..f8e2ff6 100755
--- a/kaya-client
+++ b/kaya-client
@@ -23,6 +23,14 @@ shopt -s inherit_errexit 2>/dev/null ||: # ignore fail in bash < 4.4
 set -eE -o pipefail
 trap 'echo "$0:$LINENO:error: \"$BASH_COMMAND\" exit status: $?, PIPESTATUS: ${PIPESTATUS[*]}" >&2' ERR
 
+read -r kaya_protocol_version
+
+if [[ $kaya_protocol_version != 1 ]] ; then
+    echo "kaya-client: error: mismatched protocol version with kaya" >&2
+    echo "kaya-client: error: kaya protocol version: ${kaya_protocol_version} kaya-client protocol version: 1" >&2
+    exit 1
+fi
+
 read -r password
 
 port="$1"
-- 
2.25.1