#!/bin/bash
# deny-rsync [message]: send an rsync-protocol error message

protocol_version=29
exit_code=4 # same as a daemon that refuses an option

# byte_escape 29 ==> \035
function byte_escape {
	octbyte="000$(bc <<<"obase=8; $1")"
	echo -n "\\${octbyte: -3}"
}

msg="$1"
if [ "${#msg}" -gt 255 ]; then
	# message is too long for this naive script to handle
	msg="${msg:0:252}..."
fi

# send protocol version
echo -ne "$(byte_escape $protocol_version)\\000\\000\\000"

# send checksum seed
echo -ne "\\000\\000\\000\\000"

# the following is equivalent to rwrite(FERROR, $msg)
# message header: length 17; MPLEX_BASE + code FERROR
echo -ne "$(byte_escape ${#msg})\\000\\000\\010"
# data
echo -n "$msg"

exit $exit_code