#!/bin/bash
# Send an error message via the rsync-protocol to a non-daemon client rsync.
#
# Usage:  deny-rsync "message"

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

# e.g. byte_escape 29 => \035
function byte_escape {
    echo -ne "\\0$(printf "%o" $1)"
}

msg="$1"
if [ "${#msg}" -gt 254 ]; then
    # truncate a message that is too long for this naive script to handle
    msg="${msg:0:251}..."
fi
msglen=$(( ${#msg} + 1 )) # add 1 for the newline we append below

# 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, "$msg\n")
# message header: length 17; MPLEX_BASE + code FERROR
echo -ne "$(byte_escape $msglen)\\000\\000\\010"
# data
echo -E "$msg"

# make sure the client gets the message and not a write error
sleep 1

exit $exit_code