odhcp6c.sh

#!/bin/bash
########################################################################
#
# This script will replace Unifi's executable /usr/sbin/odhcp6c.           
# It will fetch active DHCP v4 client options from current                 
# ubios-udapi-server state, and then prepare DHCP v6 client options.
# DHCP v6 options are generated using a user-defined configuration file
# (/usr/local/etc/dhcpv6.conf), or with the default (dhcpv6-orange.conf)
# At the end, it will 'exec' a new version (provided) of odhcp6c
# (supporting the -K CoS option) with all needed DHCP options arguments
#
########################################################################

# "ubios-udapi-server" will call this script with arguments ("$@") : 
# -e -v -s /usr/share/ubios-udapi-server/ubios-odhcp6c-script -D -P 56 <WANinterface>
# -D means : Discard advertisements without any address or prefix proposed
# -P 56 comes from UI WAN section (defaut 48 to change for Orange)
# what we will get from Orange e.g. 2a01:cb00:647:6c00::/56)

SCRIPT_DIR=$(dirname ${0})
HDR="[dhcpv6-mod]"  # header set in all messages

DHCPV6_CONF=/data/local/etc/dhcpv6.conf                             # Customized conf, if exists
DEFAULT_DHCPV6_CONF=/data/dhcpv6-mod/dhcpv6-orange.conf             # Otherwise will take Orange conf
DHCP6C_SUPPORTED_OPTIONS=/data/dhcpv6-mod/supported-options.json    # Which DHCPv6 options are possible

# Default requested options (values for Orange), can be overriden in dhcpv6.conf
# vendor-opts(17), name-servers(23), domain-search(24)
default_dhcpv6_request_options="17,23,24"        

# Default basic odhcp6c cmd options, can be overriden in dhcpv6.conf
# -a deactivates support for reconfigure opcode, -f deactivates sending hostname, 
# -R deactivates requesting option not specified in -r (which are specified with [default_]dhcpv6_request_options)
default_odhcp6c_options="-a -f -R"

org_odhcp6c=/usr/sbin/odhcp6c-org       # We have renamed original to -org
dhcp6_client=${org_odhcp6c}             # We will "exec" that at the end if not in test mode
test_mode=0


##########################################################################
#    EXEC() UNIFI'S odhcp6c ORIGINAL BINARY AT THE END OF THIS SCRIPT    #
#    Input variables that must be set :                                  #
#    - dhcp6_client : original odhcp6c binary path (or /bin/echo)        #
#    - arg_without_e : original args passed to odhcp6c by udapi-server   #
#    - test_mode : 0 (false) or 1 (true)                                 #
#    - odhcp6c_options : modified options to pass to dhcp6_client        #
#    - odhcp6c_options_abbrev : obfuscated odhcp6c_options (log)         #
##########################################################################

execUnifiClient() {

    # If Unifi's binary has not been set (should not happen), we can't exec it, so we abort
    if [[ ! -x "${dhcp6_client}" ]]; then
        >&2 echo "$HDR $(colorRed 'ERROR:') Unifi dhcpv6 client ${dhcp6_client} not found or not executable"
        exit 1
    fi

    [[ -z "${odhcp6c_options}" ]] && odhcp6c_options_abbrev=""  # Typically when called from errExit()

    if [[ $test_mode -eq 1 ]]; then printf "$HDR odhcp6c would be called with options : "
    else
        echo "$HDR Sleeping 5 seconds before launching ${dhcp6_client}, to let udhcpc send its discover..."
        sleep 5
        echo "$HDR" $(colorGreen "Launching exec") "${dhcp6_client} ${odhcp6c_options_abbrev} ${arg_without_e}"
    fi

    exec ${dhcp6_client} ${odhcp6c_options} ${arg_without_e}

}

###########################################################
#                    MESSAGE UTILITIES                    # 
###########################################################

green='\E[32m'; red='\E[31m'; yellow='\E[33m'; clear='\E[0m'
colorGreen() { printf "$green$1$clear"; }
colorRed() { printf "$red$1$clear"; }
colorYellow() { printf "$yellow$1$clear"; }


errExit() {
    >&2 echo "$HDR $(colorRed 'ERROR:') $1"
    # In case of error in this script we want to pass the original arguments
    odhcp6c_options=""
    # We pass control to the original executable
    execUnifiClient
}

showPartOf() {   # show only some first and last chars of a string
    l=${#1}; ln=$(( (l-1) / 4 )); [[ $ln -gt 5 ]] && ln=5
    if [[ $l -le 4 ]]; then printf '.%.0s' $(seq 1 $l)
    else printf '%s...%s' ${1:0:$ln} ${1: -$ln}
    fi
}

###########################################################
#         ARG CHECKING AND VARIABLE INITIALIZATIONS       # 
###########################################################

[[ $# -lt 1 ]] && errExit "at least 1 (last argument) : WAN interface, e.g. eth4.832"

# Interface name provided by udapi-server as last arg, we will look for it in JSON config
arg_iface="${@: -1}"

if [[ "$1" == "test" ]]; then   # if 1st arg is "test" (simulation) don't exec dhcpv6 client at the end
    dhcp6_client=/bin/echo    # so that we don't really call odhcp6c 
    test_mode=1
    shift
    if [[ $# -ne 1 ]]; then
        >&2 echo "$HDR $(colorRed 'ERROR:') test mode has 2 arguments, e.g. $0 test eth4.832" 
        exit 1
    fi
    arg_iface=$1
    echo "$HDR $(colorYellow 'NOTE: running in test mode') using interface ${arg_iface}"    
    DHCPV6_CONF=${SCRIPT_DIR}/test-files/dhcpv6.conf      # test conf, if exists
    DEFAULT_DHCPV6_CONF=${SCRIPT_DIR}/dhcpv6-orange.conf  # otherwise will take Orange conf
    DHCP6C_SUPPORTED_OPTIONS=${SCRIPT_DIR}/supported-options.json
fi

# To remove the -e (log in stderr) provided by udapi-server in order to avoid duplicated messages in syslog daemon.log
arg_without_e=$(echo " $@" | sed "s/ -e//")

[[ ! -x "$dhcp6_client" ]] && errExit "could not find odhcp6c executable $dhcp6_client"
echo "$HDR Selected DHCPv6 client executable (with support for CoS) : ${dhcp6_client}"


###########################################################
#    FETCHING DHCP V4 OPTIONS FROM UBIOS-UDAPI-CLIENT     #
###########################################################

interface_json=$(ubios-udapi-client GET -r /interfaces | jq -r '.[] | select(.identification.id=="'${arg_iface}'")')
[[ -z "$interface_json" ]] && errExit "could not retrieve interface $arg_iface using ubios-udapi-client GET"

dhcpopt_json=$(echo $interface_json | jq -r '.ipv4.dhcpOptions')
[[ "$dhcpopt_json" == "null" ]] && errExit "could not retrieve dhcpOptions of interface ${arg_iface}"

# If there was no V4 option set on the interface, then do nothing and exec original odhcp6c
if [[ "$dhcpopt_json" == "[]" ]]; then 
    echo "$HDR No DHCPv4 options set for interface ${arg_iface}, nothing to do"
    execUnifiClient
fi

for optn in $(echo $dhcpopt_json | jq -r '.[].optionNumber'); do
    val=$(echo $dhcpopt_json | jq -r '.[] | select(.optionNumber=='"${optn}"') | .value')
    if [[ "$val" =~ ^[[:xdigit:]]+$ ]]; then
        val=$(echo -n "$val" | tr 'abcdef' 'ABCDEF')                # e.g. from 789abc to 789ABC
        valX="${val}"
    elif [[ "$val" =~ ^([[:xdigit:]]{2}:)*[[:xdigit:]]{2}$ ]]; then
        val=$(echo -n "$val" | tr 'abcdef' 'ABCDEF' | tr -d ':')    # e.g. from 78:9a:bc to 789ABC
        valX="${val}"
    else # it's a string
        valX=$(echo -n "$val" | xxd -p -u -c9999)     # string to hexdump : e.g. Live to 4C697665
    fi
    optv4[optn]="$val"
    optv4_hex[optn]="$valX"
    optv4_hexlen[optn]=$(printf '%04x' $((${#valX}/2)))
    echo "$HDR Fetched DHCPv4 option ${optn} : length=${#val} value="$(showPartOf "${val}")
done

# Fetch either MAC Adress Clone or DHCPv4 option 61, the latter takes precedence if both were entered
macaddr=$(echo $interface_json | jq -r '.identification.macOverride' | tr 'abcdef' 'ABCDEF' | tr -d ':')
[ -z "${optv4[61]}" ] && optv4[61]="${macaddr}" || macaddr="${optv4[61]}"
if [[ "$macaddr" == "null" ]]; then
    macaddr=""
    echo "$HDR $(colorYellow "WARNING:") could not fetch MAC Address clone (or option 61) from DHCPv4 config"
else 
    echo "$HDR Fetched MAC Address Clone (or option 61): length=${#macaddr}"
    [ "${#macaddr}" -ne 12 ] && echo "$HDR $(colorYellow "WARNING:") length of macaddress clone is ${#macaddr}, not 12 digits"
fi

# Fetch IPv4 CoS, if set we will use it for -K <CoS>, can be overriden by dhcpv6_cos setting of dhcpv6.conf
dhcpv4_cos=$(echo $interface_json | jq -r '.ipv4.cos')
[ "${dhcpv4_cos}" == "null" ] && dhcpv4_cos=0
echo "$HDR Fetched DHCPv4 CoS of ${dhcpv4_cos}"

# Provide duid_time_hex for the dhcpv6.conf file in case user needs 32-byte DUID time field
duid_time_dec=$(( ($(date +%s) - 946684800) % 2**32 ))
duid_time_hex=$(printf '%04x' $duid_time_dec | tr 'abcdef' 'ABCDEF')


###########################################################
#    EXECUTE DHCPV6_CONF TO GENERATE DHCP V6 OPTIONS      #
###########################################################

# set -u will stop DHCPV6_CONF execution if using any optv4[] not found in JSON
if [ -f ${DHCPV6_CONF}.${arg_iface} ]; then
    DHCPV6_CONF=${DHCPV6_CONF}.${arg_iface}
    echo "$HDR Found interface-specific dhcp6c options file ${DHCPV6_CONF}"
elif [ -f ${DHCPV6_CONF} ]; then
    echo "$HDR Found dhcp6c options file ${DHCPV6_CONF}"
else 
    echo "$HDR $(colorYellow 'WARNING:') took default dhcp6c options file ${DEFAULT_DHCPV6_CONF}, as ${DHCPV6_CONF} was not found"
    DHCPV6_CONF=${DEFAULT_DHCPV6_CONF}
fi

trap "errExit 'problem running '"${DHCPV6_CONF}"', probably a reference to a nonexistent V4 option'" EXIT
set -u
. ${DHCPV6_CONF} || errExit "problem running dhcp6 config file ${DHCPV6_CONF}"
set +u
trap - EXIT


###########################################################
#       CHECK AND FORMAT GENERATED DHCP V6 OPTIONS        #
###########################################################

# Supported DHCPv6 options of odhcp6c
supported_options_json=$(cat $DHCP6C_SUPPORTED_OPTIONS | jq -r '.supportedOptions[]')

# Initialize odhcp6c_options with minimum options for odhcp6c cmd
if [[ -z "${odhcp6c_options+x}" ]]; then
    odhcp6c_options="${default_odhcp6c_options}"  # see at the top of this script for the default
else
    echo "$HDR" "NOTE: default overriden to odhcp6c_options=${odhcp6c_options}"
fi

# -r argument : requested options from DHCP server, comma-separated
if [[ -z "${dhcpv6_request_options+x}" ]]; then
    dhcpv6_request_options="${default_dhcpv6_request_options}"  # see at the top of this script for the default
else
    echo "$HDR" "NOTE: default overriden to dhcpv6_request_options=${dhcpv6_request_options}"
fi
[[ -n "${dhcpv6_request_options}" ]] && odhcp6c_options="${odhcp6c_options} -r${dhcpv6_request_options}"

# Set DHCPv6 CoS, to same as DHCPv4 CoS except if user specified a different value dhcpv6_cos (should not happen...)
if [[ -z "${dhcpv6_cos+x}" ]]; then
    dhcpv6_cos=${dhcpv4_cos}
    echo "$HDR Generated DHCPv6 CoS of ${dhcpv6_cos} (default is to set to the same value as DHCPv4 CoS)"
else
    if [[ "${dhcpv6_cos}" == "${dhcpv4_cos}" ]]; then
        echo "$HDR" $(colorYellow "NOTE:") "dhcpv6_cos=${dhcpv6_cos} setting is useless, as DHCPv4 CoS ${dhcpv4_cos} is copied by default, consider removing the setting"
    else
        echo "$HDR" $(colorYellow "WARNING: dhcpv6_cos=${dhcpv6_cos} setting is not the same as DHCPv4 CoS ${dhcpv4_cos}, please check !")
    fi
fi
[[ -n "${dhcpv6_cos}" ]] && odhcp6c_options="${odhcp6c_options} -K${dhcpv6_cos}"

odhcp6c_options_abbrev="${odhcp6c_options}"

# Iterate over V6 options set in DHCPV6_CONF to construct odhcp6c arguments
for n in ${!optv6[@]}; do
    format=$(echo -n $supported_options_json | jq -r 'select(.number=='"${n}"') | .optionFormat')
    [[ $? -ne 0 ]] && errExit "unsupported DHCPv6 option $n specified in ${DHCPV6_CONF}"
    alias=$(echo -n $supported_options_json | jq -r 'select(.number=='"${n}"') | .optionAlias')
    odhcp6cOption=$(echo -n $supported_options_json | jq -r 'select(.number=='"${n}"') | .odhcp6cOption')
    val=${optv6[n]}
    if [[ "$format" == "string" ]]; then
        val2="${val}"   # already readable string, needs no transformation
    elif [[ "$val" =~ ^[[:xdigit:]]+$ ]]; then
        val2="${val}"   # already hexstring, needs no transformation
    elif [[ "$val" =~ ^([[:xdigit:]]{2}:)*[[:xdigit:]]{2}$ ]]; then
        val2=$(echo -n "$val" | tr 'abcdef' 'ABCDEF' | tr -d ':')    # e.g. from 78:9a:bc to 789ABC
    else
        val2=$(echo -n "$val" | xxd -p -u -c9999)     # string to hexdump : e.g. Live to 4C697665
    fi
    echo "$HDR Generated DHCPv6 option $n : length=${#val2} value="$(showPartOf "${val2}")" (${alias}, ${odhcp6cOption})"
    odhcp6c_options="${odhcp6c_options} ${odhcp6cOption}${val2}"
    odhcp6c_options_abbrev="${odhcp6c_options_abbrev} ${odhcp6cOption}$(showPartOf "${val2}")" 
done

echo "$HDR Successfully generated ${#optv6[@]} DHCPv6 options using ${DHCPV6_CONF}"

# Replace the current shell with Unifi's original odhcp6c binary (via exec) 
execUnifiClient