nmcli-cli-ipv6-copy

#!/bin/bash
#
# nmcli-cli-ipv6-copy
#
# Copyright (c) 2019-2026 Jun Futagawa (jfut)
#
# This software is released under the MIT License.
# http://opensource.org/licenses/mit-license.php

ECHO_OR_EXECUTE="echo"

print_command() {
    # Print the nmcli command in a reusable shell-quoted form.
    printf '%q' "$1"
    shift
    printf ' %q' "$@"
    printf '\n'
}

echo_or_execute() {
    local RET

    if [[ -z "${ECHO_OR_EXECUTE}" ]]; then
        printf 'Applying: '
        print_command "$@"
        "$@"
        RET=$?
        if [[ ${RET} -ne 0 ]]; then
            echo "Error: command failed (${RET})." >&2
            exit "${RET}"
        fi
    else
        print_command "$@"
    fi
}

nmcli_value() {
    # Convert only nmcli's unset marker to an empty string.
    local value=${1:-}
    [[ "${value}" == "--" ]] && value=""
    printf '%s' "${value}"
}

usage() {
    cat << _EOF_
Usage:

    $0 [-n] [-x] SRC_IF_NAME DEST_IF_NAME

    Options:
        -n No interface check (Default: check interface)
        -x Run command (Default: echo only)

    Examples:
        $0 eno1 bond1
        $0 bond1 br1
        $0 eno1 (show current configuration)

_EOF_
}

check() {
    local SRC_IF_NAME=${1:-}
    local DEST_IF_NAME=${2:-${SRC_IF_NAME}}

    # Check interface: src
    nmcli connection show "${SRC_IF_NAME}" > /dev/null 2>&1
    RET=$?
    if [[ ${RET} -ne 0 ]]; then
        echo "Error: Source interface \"${SRC_IF_NAME}\" not found."
        exit 1
    fi

    # Check interface: dest
    nmcli connection show "${DEST_IF_NAME}" > /dev/null 2>&1
    RET=$?
    if [[ ${RET} -ne 0 ]]; then
        echo "Error: Destination interface \"${DEST_IF_NAME}\" not found."
        exit 1
    fi
}

ipv6_copy() {
    local SRC_IF_NAME=${1:-}
    local DEST_IF_NAME=${2:-${SRC_IF_NAME}}

    # IP
    SRC_IP_SUBNET=$(nmcli_value "$(nmcli -g ipv6.addresses connection show "${SRC_IF_NAME}")")
    SRC_METHOD=$(nmcli_value "$(nmcli -g ipv6.method connection show "${SRC_IF_NAME}")")
    echo_or_execute nmcli connection modify "${DEST_IF_NAME}" ipv6.addresses "${SRC_IP_SUBNET}" ipv6.method "${SRC_METHOD}"

    # Gateway
    SRC_GATEWAY=$(nmcli_value "$(nmcli -g ipv6.gateway connection show "${SRC_IF_NAME}")")
    echo_or_execute nmcli connection modify "${DEST_IF_NAME}" ipv6.gateway "${SRC_GATEWAY}"

    # DNS
    SRC_DNS=$(nmcli_value "$(nmcli -g ipv6.dns connection show "${SRC_IF_NAME}")")
    echo_or_execute nmcli connection modify "${DEST_IF_NAME}" ipv6.dns "${SRC_DNS}"

    cat << _EOF_

# Next steps:
# -> Change IP address
#    nmcli-cli-ipv6 "${DEST_IF_NAME}" ...
# -> Restart the interface:
#    nmcli-cli-restart "${DEST_IF_NAME}"
#
# -> Create a bond interface:
#    nmcli-cli-bond-add bond1 mode=... "${DEST_IF_NAME}" "ens2f0"
# -> Create a vlan interface:
#    nmcli-cli-vlan-add "${DEST_IF_NAME}.100" 100 "${DEST_IF_NAME}"
# -> Create a bridge interface:
#    nmcli-cli-bridge-add br1 "${DEST_IF_NAME}"
_EOF_
}

# Main
main() {
    local NO_CHECK="no"
    while getopts nxh OPT; do
        case "${OPT}" in
            "n" )
                NO_CHECK="yes" ;;
            "x" )
                ECHO_OR_EXECUTE="" ;;
            "h" )
                usage
                exit 0
                ;;
            * )
                usage
                exit 1
                ;;
        esac
    done
    shift $((OPTIND - 1))

    [[ $# -lt 1 ]] && usage && exit 1

    if [[ "${NO_CHECK}" = "no" ]]; then
        check "${@}"
    fi

    if [[ "${ECHO_OR_EXECUTE}" = "echo" ]]; then
        echo "# ${ECHO_OR_EXECUTE} only."
    fi

    ipv6_copy "${@}"
}

[[ ${#BASH_SOURCE[@]} = 1 ]] && main "${@}"