gre-on-wg/gre-on-wg.sh

#!/bin/bash

set -euo pipefail

_="${DEBUG:=}"

strstrip() {
    sed -E -e 's/^\s*//' -e 's/\s*$//'
}

create_br() {
    local name
    name="$1"

    $DEBUG ip link add "$name" type bridge
}

create_gre() {
    local name local_ip remote_ip
    name="$1"
    local_ip="$(sed 's_/.*$__' <<< "$2")"
    remote_ip="$(sed 's_/.*$__' <<< "$3")"

    $DEBUG ip link add "$name" type gretap local "$local_ip" remote "$remote_ip"
    $DEBUG ip link set up "$name"
}

add_gre_to_br() {
    local br_name gre_name
    br_name="$1"
    gre_name="$2"

    $DEBUG ip link set "$gre_name" master "$br_name"
}

finish_br() {
    local name local_ip
    name="$1"
    local_ip="$2"

    $DEBUG ip addr add "$local_ip" dev "$name"
    $DEBUG ip link set up "$name"
}

read_wg_conf() {
    local filepath
    local local_ip remote_ips mode line
    filepath="$1"

    local_ip=
    remote_ips=
    mode=
    while read -r line; do
        line="$(strstrip <<< "$line")"
        if [[ "$line" = '[Interface]' ]]; then
            mode=interface
            continue
        elif [[ "$line" = '[Peer]' ]]; then
            mode=peer
            continue
        fi
        if [[ "$mode" = 'interface' ]] && [[ "$line"  =~ ^Address\ *=\ * ]]; then
            local_ip="$(awk -F= '{print $2}' <<< "$line" | strstrip)"
        elif [[ "$mode" = 'peer' ]] && [[ "$line" =~ ^AllowedIPs\ *=\ * ]]; then
            remote_ips="$remote_ips $(awk -F= '{print $2}' <<< "$line" | strstrip)"
        fi
    done < "$filepath"
    remote_ips="$(strstrip <<< "$remote_ips")"

    echo "$local_ip"
    echo "$remote_ips"
}

create_networks() {
    local wg_name local_ip local_ip_trans remote_ips
    local br_name n
    wg_name="$1"
    local_ip="$2"
    local_ip_trans="$3"
    remote_ips="$4"

    br_name="${wg_name}br1"
    n=1

    create_br "$br_name"
    for remote_ip in $remote_ips ; do
        create_gre "${wg_name}gre$n" "$local_ip" "$remote_ip"
        add_gre_to_br "$br_name" "${wg_name}gre$n"
        n=$((n+1))
    done

    finish_br "$br_name" "$local_ip_trans"
}

up() {
    local filepath translation_filepath
    local r local_ip remote_ips local_ip_trans
    filepath="$1"
    translation_filepath=
    if [[ "$filepath" =~ .*/.* ]]; then
        # path, not a name, leave as is
        :
    else
        if [[ $# -eq 1 ]]; then
            translation_filepath="$filepath"
        fi
        filepath="/etc/wireguard/$filepath.conf"
    fi

    if [[ -z "$translation_filepath" ]]; then
        translation_filepath="$2"
        if [[ "$translation_filepath" =~ .*/.* ]]; then
            # path, not a name, leave as is
            :
        else
            translation_filepath="/etc/gre-on-wg/$filepath.conf"
        fi
    fi

    r="$(read_wg_conf "$filepath")"
    local_ip="$(head -n1 <<< "$r")"
    remote_ips="$(tail -n1 <<< "$r")"
    unset r

    local_ip_trans="$(grep -E "$(sed 's_\._\\._g' <<< "$local_ip")" "$translation_filepath" | awk '{print $2}')"

    create_networks "$(basename --suffix='.conf' "$filepath")" "$local_ip" "$local_ip_trans" "$remote_ips"
}

down() {
    local filepath
    local wg_name link
    filepath="$1"
    if [[ "$filepath" =~ .*/.* ]]; then
        # path, not a name, leave as is
        :
    else
        filepath="/etc/wireguard/$filepath.conf"
    fi
    wg_name="$(basename --suffix=.conf "$filepath")"
    for link in $(ip link list | grep -Eo '^[0-9]+:\s+wg0[^:@]+' | sed -E 's/[0-9]+:\s+//'); do
        $DEBUG ip link del "$link"
    done
}

"$@"