#!/bin/bash
#
####################################################
# Fix for FreePBX Distro (SNG7) DHCP on Amazon EC2 #
####################################################
#
# https://github.com/kd4ned/freepbxdistro-aws-dhcpfix
#  (c)2018 Jeremy Gault / Voiceopia Communications <jeremy@voiceopia.com>
# You are free to use this script as needed.
#
dhconfig() {
    if [ -n "${old_ip_address}" ] && [ -n "${alias_ip_address}" ] &&
       [ ! "${alias_ip_address}" = "${old_ip_address}" ]; then
        # possible new alias, remove old alias first
        ip -4 addr del ${old_ip_address} dev ${interface} label ${interface}:0
    fi

    if [ -n "${old_ip_address}" ] &&
       [ ! "${old_ip_address}" = "${new_ip_address}" ]; then
        # IP address changed. Delete all routes, and clear the ARP cache.
        flush_dev ${interface}
    fi

    # make sure the interface is up
    ip link set dev ${interface} up

    # replace = add if it doesn't exist or override (update lifetimes) if it's there
    ip -4 addr replace ${new_ip_address}/${new_prefix} broadcast ${new_broadcast_address} dev ${interface} >/dev/null 2>&1


    if [ "${reason}" = "BOUND" ] || [ "${reason}" = "REBOOT" ] ||
       [ ! "${old_ip_address}" = "${new_ip_address}" ] ||
       [ ! "${old_subnet_mask}" = "${new_subnet_mask}" ] ||
       [ ! "${old_network_number}" = "${new_network_number}" ] ||
       [ ! "${old_broadcast_address}" = "${new_broadcast_address}" ] ||
       [ ! "${old_routers}" = "${new_routers}" ] ||
       [ ! "${old_interface_mtu}" = "${new_interface_mtu}" ]; then
        
        # The 576 MTU is only used for X.25 and dialup connections
        # where the admin wants low latency.  Such a low MTU can cause
        # problems with UDP traffic, among other things.  As such,
        # disallow MTUs from 576 and below by default, so that broken
        # MTUs are ignored, but higher stuff is allowed (1492, 1500, etc).
        if [ -n "${new_interface_mtu}" ] && [ ${new_interface_mtu} -gt 576 ]; then
            ip link set dev ${interface} mtu ${new_interface_mtu}
        fi

        # static routes
        if [ -n "${new_classless_static_routes}" ] ||
           [ -n "${new_static_routes}" ]; then
            if [ -n "${new_classless_static_routes}" ]; then
                IFS=', |' static_routes=(${new_classless_static_routes})
		# If the DHCP server returns both a Classless Static Routes option and
                # a Router option, the DHCP client MUST ignore the Router option. (RFC3442)
                new_routers=""
            else
                IFS=', |' static_routes=(${new_static_routes})
            fi
            route_targets=()

            for((i=0; i<${#static_routes[@]}; i+=2)); do
                target=${static_routes[$i]}
                if [ -n "${new_classless_static_routes}" ]; then
		    if [ ${target} = "0" ]; then
                        new_routers="${static_routes[$i+1]}"
                        continue
                    else
                        prefix=${target%%.*}
                        target=${target#*.}
                        IFS="." target_arr=(${target})
                        unset IFS
                        ((pads=4-${#target_arr[@]}))
                        for j in $(seq $pads); do
                            target="${target}.0"
                        done

                        # Client MUST zero any bits in the subnet number where the corresponding bit in the mask is zero.
                        # In other words, the subnet number installed in the routing table is the logical AND of
                        # the subnet number and subnet mask given in the Classless Static Routes option. (RFC3442)
                        target="$(get_network_address ${target} ${prefix})"
                    fi
                else
                    prefix=$(class_bits ${target})
                fi
                gateway=${static_routes[$i+1]}

                # special case 0.0.0.0 to allow static routing for link-local addresses
                # (including IPv4 multicast) which will not have a next-hop (#769463, #787318)
                if [ "${gateway}" = "0.0.0.0" ]; then
                    valid_gateway=0
                    scope='scope link'
                else
                    is_router_reachable ${gateway}
                    valid_gateway=$?
                    scope=''
                fi
                if [ ${valid_gateway} -eq 0 ]; then
                    metric=''
                    for t in ${route_targets[@]}; do
                        if [ ${t} = ${target} ]; then
                            if [ -z "${metric}" ]; then
                                metric=1
                            else
                                ((metric=metric+1))
                            fi
                        fi
                    done

                    if [ -n "${metric}" ]; then
                        metric="metric ${metric}"
                    fi

                    ip -4 route replace ${target}/${prefix} proto static via ${gateway} dev ${interface} ${metric} ${scope}

                    if [ $? -ne 0 ]; then
                        logmessage "failed to create static route: ${target}/${prefix} via ${gateway} dev ${interface} ${metric}"
                    else
                        route_targets=(${route_targets[@]} ${target})
                    fi
                fi
            done
        fi

        # gateways
        if [[ ( "${DEFROUTE}" != "no" ) &&
              (( -z "${GATEWAYDEV}" ) || ( "${GATEWAYDEV}" = "${interface}" )) ]]; then
            if [[ ( -z "$GATEWAY" ) ||
                  (( -n "$DHCLIENT_IGNORE_GATEWAY" ) && ( "$DHCLIENT_IGNORE_GATEWAY" = [Yy]* )) ]]; then
                metric="${METRIC:-}"
                let i="${METRIC:-0}"
                default_routers=()

                for router in ${new_routers} ; do
                    added_router=-

                    for r in ${default_routers[@]} ; do
                        if [ "${r}" = "${router}" ]; then
                            added_router=1
                        fi
                    done

                    if [ -z "${router}" ] ||
                       [ "${added_router}" = "1" ] ||
                       [ $(IFS=. ip2num ${router}) -le 0 ] ||
                       [[ ( "${router}" = "${new_broadcast_address}" ) &&
                          ( "${new_subnet_mask}" != "255.255.255.255" ) ]]; then
                        continue
                    fi

                    default_routers=(${default_routers[@]} ${router})
                    add_default_gateway ${router} ${metric}
                    let i=i+1
                    metric=${i}
                done
            elif [ -n "${GATEWAY}" ]; then
                routersubnet=$(get_network_address ${GATEWAY} ${new_subnet_mask})
                mysubnet=$(get_network_address ${new_ip_address} ${new_subnet_mask})

                if [ "${routersubnet}" = "${mysubnet}" ]; then
                    ip -4 route replace default via ${GATEWAY} dev ${interface}
                fi
            fi
        fi
    fi

    if [ ! "${new_ip_address}" = "${alias_ip_address}" ] &&
       [ -n "${alias_ip_address}" ]; then
        # Reset the alias address (fix: this should really only do this on changes)
        ip -4 addr flush dev ${interface} label ${interface}:0 >/dev/null 2>&1
        ip -4 addr replace ${alias_ip_address}/${alias_prefix} broadcast ${alias_broadcast_address} dev ${interface} label ${interface}:0
        ip -4 route replace ${alias_ip_address}/32 dev ${interface}
    fi
    
    # After dhclient brings an interface UP with a new IP address, subnet mask, 
    # and routes, in the REBOOT/BOUND states -> search for "dhclient-up-hooks".
    if [ "${reason}" = "BOUND" ] || [ "${reason}" = "REBOOT" ] ||
       [ ! "${old_ip_address}" = "${new_ip_address}" ] ||
       [ ! "${old_subnet_mask}" = "${new_subnet_mask}" ] ||
       [ ! "${old_network_number}" = "${new_network_number}" ] ||
       [ ! "${old_broadcast_address}" = "${new_broadcast_address}" ] ||
       [ ! "${old_routers}" = "${new_routers}" ] ||
       [ ! "${old_interface_mtu}" = "${new_interface_mtu}" ]; then
        
        if [ -x ${ETCDIR}/dhclient-${interface}-up-hooks ]; then
            . ${ETCDIR}/dhclient-${interface}-up-hooks
        elif [ -x ${ETCDIR}/dhclient-up-hooks ]; then
            . ${ETCDIR}/dhclient-up-hooks
        fi
    fi

    make_resolv_conf

    if [ -n "${new_host_name}" ] && need_hostname; then
        hostname ${new_host_name} || echo "See -nc option in dhclient(8) man page."
    fi

    if [[ ( "${DHCP_TIME_OFFSET_SETS_TIMEZONE}" = [yY1]* ) &&
          ( -n "${new_time_offset}" ) ]]; then
        # DHCP option "time-offset" is requested by default and should be
        # handled.  The geographical zone abbreviation cannot be determined
        # from the GMT offset, but the $ZONEINFO/Etc/GMT$offset file can be
        # used - note: this disables DST.
        ((z=new_time_offset/3600))
        ((hoursWest=$(printf '%+d' $z)))

        if (( $hoursWest < 0 )); then
            # tzdata treats negative 'hours west' as positive 'gmtoff'!
            ((hoursWest*=-1))
        fi

        tzfile=/usr/share/zoneinfo/Etc/GMT$(printf '%+d' ${hoursWest})
        if [ -e ${tzfile} ]; then
            cp -fp ${tzfile} /etc/localtime
            touch /etc/localtime
        fi
    fi

    execute_client_side_configuration_scripts "config"
}

# Section 18.1.8. (Receipt of Reply Messages) of RFC 3315 says:
# The client SHOULD perform duplicate address detection on each of
# the addresses in any IAs it receives in the Reply message before
# using that address for traffic.
add_ipv6_addr_with_DAD() {
            ip -6 addr replace ${new_ip6_address}/${new_ip6_prefixlen} \
                dev ${interface} scope global

            # repeatedly test whether newly added address passed
            # duplicate address detection (DAD)
            for i in $(seq 5); do
                sleep 1 # give the DAD some time

                addr=$(ip -6 addr show dev ${interface} \
                       | grep ${new_ip6_address}/${new_ip6_prefixlen})

                # tentative flag == DAD is still not complete
                tentative=$(echo "${addr}" | grep tentative)
                # dadfailed flag == address is already in use somewhere else
                dadfailed=$(echo "${addr}" | grep dadfailed)

                if [ -n "${dadfailed}" ] ; then
                    # address was added with valid_lft/preferred_lft 'forever', remove it
                    ip -6 addr del ${new_ip6_address}/${new_ip6_prefixlen} dev ${interface}
                    exit_with_hooks 3
                fi
                if [ -z "${tentative}" ] ; then
                    if [ -n "${addr}" ]; then
                        # DAD is over
                        return 0
                    else
                        # address was auto-removed (or not added at all)
                        exit_with_hooks 3
                    fi
                fi
            done
            return 0
}