#!/bin/sh
# SPDX-License-Identifier: GPL-2.0
# This is not an autoconf generated configure
#

# Output file which is input to Makefile
CONFIG_FINAL=config.mk
CONFIG=".${CONFIG}.tmp"

# Make a temp directory in build tree.
TMPDIR=$(mktemp -d config.XXXXXX)
trap 'status=$?; rm -rf $TMPDIR; rm -f $CONFIG; exit $status' EXIT HUP INT QUIT TERM

check_opts()
{
    : ${PRODUCTION:=0}
    : ${DYNAMIC_LIBXDP:=0}
    : ${MAX_DISPATCHER_ACTIONS:=10}
    : ${BPF_TARGET:=bpf}
    echo "PRODUCTION:=${PRODUCTION}" >>$CONFIG
    echo "DYNAMIC_LIBXDP:=${DYNAMIC_LIBXDP}" >>$CONFIG
    echo "MAX_DISPATCHER_ACTIONS:=${MAX_DISPATCHER_ACTIONS}" >>$CONFIG
    echo "BPF_TARGET:=${BPF_TARGET}" >>$CONFIG
}

find_tool()
{
    local tool_name
    local tool_path
    local v

    tool_name="$1"
    tool_path="$2"

    if [ "$tool_name" != "$tool_path" ] || command -v "$tool_path" >/dev/null 2>&1; then
        echo $tool_path
        return 0
    fi

    # we're looking for a binary with the same name as tool_name; try version
    # suffixes in order until we find one
    for v in 16 15 14 13 12 11; do
        tool_path="${tool_name}-$v"
        if command -v "$tool_path" >/dev/null 2>&1; then
            echo $tool_path
            return 0
        fi
    done

    # Fall back to supplied default, check in caller will error out
    echo $tool_name
}

check_toolchain()
{
    local emacs_version
    local clang_version
    local bpftool_version

    : ${PKG_CONFIG:=pkg-config}
    : ${CC=gcc}
    : ${LD=ld}
    : ${OBJCOPY=objcopy}
    : ${CLANG=clang}
    : ${LLC=llc}
    : ${M4=m4}
    : ${EMACS=emacs}
    : ${BPFTOOL=bpftool}
    : ${ARCH_INCLUDES=}

    CLANG=$(find_tool clang "$CLANG")
    LLC=$(find_tool llc "$LLC")

    for TOOL in $PKG_CONFIG $CC $LD $OBJCOPY $CLANG $LLC $M4 $BPFTOOL; do
        if [ ! $(command -v ${TOOL} 2>/dev/null) ]; then
            echo "*** ERROR: Cannot find tool ${TOOL}" ;
            exit 1;
        fi;
    done

    clang_version=$($CLANG --version | grep -Po '(?<=clang version )[[:digit:]]+')
    if [ "$?" -ne "0" ]; then
        echo "*** ERROR: Couldn't execute '$CLANG --version'"
        exit 1
    fi

    echo "Found clang binary '$CLANG' with version $clang_version (from '$($CLANG --version | head -n 1)')"
    if [ "$clang_version" -lt "11" ]; then
        echo "*** ERROR: Need LLVM version 11+, '$CLANG' is version $clang_version"
        [ -n "$RELAXED_LLVM_VERSION" ] || exit 1
    fi

    if ! command -v $EMACS >/dev/null 2>&1; then
        EMACS=""
    else
        emacs_version=$($EMACS --version 2>/dev/null | head -n 1)
        if echo $emacs_version | grep -Eq 'GNU Emacs 2[6789]'; then
            echo "using emacs: $emacs_version"
        else
            echo "not using emacs: $emacs_version"
            EMACS=""
        fi
    fi

    if [ -z "$EMACS" ] && [ "${FORCE_EMACS:-0}" -eq "1" ]; then
        echo "FORCE_EMACS is set, but no usable emacs found on system"
        rm -f "$CONFIG"
        exit 1
    fi

    if $BPFTOOL gen help 2>&1 | grep 'gen help' > /dev/null; then
        bpftool_version=$($BPFTOOL version | head -n 1)
	echo "using $bpftool_version"
    else
	echo "bpftool doesn't support skeleton generation"
        exit 1
    fi

    if [ -z "$ARCH_INCLUDES" ]; then
        for dir in $(echo | $CC -Wp,-v -E - 2>&1 | grep '^ '); do
            local idir
            idir="${dir}/$(uname -m)-linux-gnu/"
            [ -d "$idir" ] && ARCH_INCLUDES="-I${idir} $ARCH_INCLUDES"
        done
    fi

    echo "PKG_CONFIG:=${PKG_CONFIG}" >>$CONFIG
    echo "CC:=${CC}" >>$CONFIG
    echo "LD:=${LD}" >>$CONFIG
    echo "OBJCOPY:=${OBJCOPY}" >>$CONFIG
    echo "CLANG:=${CLANG}" >>$CONFIG
    echo "LLC:=${LLC}" >>$CONFIG
    echo "M4:=${M4}" >>$CONFIG
    echo "EMACS:=${EMACS}" >>$CONFIG
    echo "ARCH_INCLUDES:=$ARCH_INCLUDES" >> $CONFIG
    echo "BPFTOOL:=${BPFTOOL}" >> $CONFIG
}

check_zlib()
{
    if ${PKG_CONFIG} zlib --exists; then
        echo "HAVE_ZLIB:=y" >>$CONFIG
        echo "yes"

        echo 'CFLAGS += -DHAVE_ZLIB' `${PKG_CONFIG} zlib --cflags` >> $CONFIG
        echo 'LDLIBS += ' `${PKG_CONFIG} zlib --libs` >>$CONFIG
    else
        echo "missing - this is required"
        return 1
    fi
}

check_elf()
{
    if ${PKG_CONFIG} libelf --exists; then
        echo "HAVE_ELF:=y" >>$CONFIG
        echo "yes"

        echo 'CFLAGS += -DHAVE_ELF' `${PKG_CONFIG} libelf --cflags` >> $CONFIG
        echo 'LDLIBS += ' `${PKG_CONFIG} libelf --libs` >>$CONFIG
    else
        echo "missing - this is required"
        return 1
    fi
}

check_pcap()
{
    local libpcap_err

    if ${PKG_CONFIG} libpcap --exists; then
        LIBPCAP_CFLAGS=$(${PKG_CONFIG} libpcap --cflags)
        LIBPCAP_LDLIBS=$(${PKG_CONFIG} libpcap --libs)
    else
        LIBPCAP_CFLAGS=""
        LIBPCAP_LDLIBS="-lpcap"
    fi

    cat >$TMPDIR/libpcaptest.c <<EOF
#define PCAP_DONT_INCLUDE_PCAP_BPF_H
#include <pcap/dlt.h>
#include <pcap/pcap.h>
int main(int argc, char **argv) {
    pcap_t *pcap = pcap_open_live("ifname", 100, 1, 1000, NULL);
    return 0;
}
EOF
    libpcap_err=$($CC -o $TMPDIR/libpcaptest $TMPDIR/libpcaptest.c  $LIBPCAP_CFLAGS $LIBPCAP_LDLIBS 2>&1)
    if [ "$?" -eq "0" ]; then
        echo "HAVE_PCAP:=y" >>$CONFIG
        [ -n "$LIBPCAP_CFLAGS" ] && echo 'CFLAGS += ' $LIBPCAP_CFLAGS >> $CONFIG
        echo "yes"
    else
        echo "missing - this is required"
        echo "error: $libpcap_err"
        return 1
    fi
}


check_libbpf_function()
{
    local FUNCTION_NAME
    local FUNCTION_ARGS
    local FUNCTION_DEFS
    local LIBBPF_CFLAGS
    local LIBBPF_LDLIBS
    local config_var
    FUNCTION_NAME="$1"
    FUNCTION_ARGS="$2"
    FUNCTION_DEFS="$3"
    LIBBPF_CFLAGS="$4"
    LIBBPF_LDLIBS="$5"

    config_var="LIBBPF_$(echo $FUNCTION_NAME | tr 'a-z' 'A-Z')"

    echo -n "  $FUNCTION_NAME support: "

    # If LIBBPF_LDLIBS is empty that means we're using the submodule version of
    # libbpf. We know it does support all the APIs we're testing for, so we hard
    # code it as supported. We can't actually run the check as the embedded
    # libbpf.a has not been built at configure time.
    if [ -z "$LIBBPF_LDLIBS" ]; then
        echo "HAVE_FEATURES+=${config_var}" >>"$CONFIG"
        echo "yes (submodule)"
        return 0;
    fi

    # If this is set we don't try to link against libbpf, as it may be in a
    # different submodule and have not been built yet. Instead, we'll copy over
    # the header files from the libbpf sources so those are used first,
    # triggering a compile error if the function we are testing for is missing.
    if [ -n "$LIBBPF_UNBUILT" ]; then
        LIBBPF_LDLIBS="-Xlinker --unresolved-symbols=ignore-in-object-files"
        LIBBPF_CFLAGS="-I$TMPDIR/include"
        mkdir -p "$TMPDIR/include"
        cp -r headers/bpf headers/linux headers/xdp "$TMPDIR/include/"
        cp "$LIBBPF_DIR"/src/bpf.h "$LIBBPF_DIR"/src/btf.h "$LIBBPF_DIR"/src/libbpf*.h "$TMPDIR/include/bpf"
        [ "$?" -eq 0 ] || return
    fi

    cat >$TMPDIR/libbpftest.c <<EOF
#include <bpf/libbpf.h>
#include <bpf/bpf.h>
#include <bpf/btf.h>
int main(int argc, char **argv) {
    ${FUNCTION_DEFS};
    ${FUNCTION_NAME}${FUNCTION_ARGS};
    return 0;
}
EOF
    compile_cmd="$CC -o $TMPDIR/libbpftest $TMPDIR/libbpftest.c -Werror $LIBBPF_CFLAGS $LIBBPF_LDLIBS"
    libbpf_err=$($compile_cmd 2>&1)
    if [ "$?" -eq "0" ]; then
        echo "HAVE_FEATURES+=${config_var}" >>"$CONFIG"
        echo "yes"
    else
        echo "no"
    fi
    if [ -n "$DEBUG_CONFIGURE" ]; then
        echo "    $compile_cmd"
        echo "${libbpf_err}" | sed 's/^/    /gm'
    fi
}

check_libbpf_functions()
{
    local LIBBPF_CFLAGS
    local LIBBPF_LDLIBS
    LIBBPF_CFLAGS="$1"
    LIBBPF_LDLIBS="$2"

    check_libbpf_function "perf_buffer__consume" "(NULL)" "" "$LIBBPF_CFLAGS" "$LIBBPF_LDLIBS"
    check_libbpf_function "btf__load_from_kernel_by_id" "(0)" "" "$LIBBPF_CFLAGS" "$LIBBPF_LDLIBS"
    check_libbpf_function "btf__type_cnt" "(0)" "$LIBBPF_CFLAGS" "" "$LIBBPF_LDLIBS"
    check_libbpf_function "bpf_object__next_map" "(NULL, NULL)" "" "$LIBBPF_CFLAGS" "$LIBBPF_LDLIBS"
    check_libbpf_function "bpf_object__next_program" "(NULL, NULL)" "" "$LIBBPF_CFLAGS" "$LIBBPF_LDLIBS"
    check_libbpf_function "bpf_program__insn_cnt" "(NULL)" "" "$LIBBPF_CFLAGS" "$LIBBPF_LDLIBS"
    check_libbpf_function "bpf_map_create" "(0, NULL, 0, 0, 0, NULL)" "" "$LIBBPF_CFLAGS" "$LIBBPF_LDLIBS"
    check_libbpf_function "perf_buffer__new_raw" "(0, 0, NULL, NULL, NULL, NULL)" "" "$LIBBPF_CFLAGS" "$LIBBPF_LDLIBS"
    check_libbpf_function "bpf_xdp_attach" "(0, 0, 0, NULL)" "" "$LIBBPF_CFLAGS" "$LIBBPF_LDLIBS"
    check_libbpf_function "bpf_map__set_autocreate" "(NULL, false)" "" "$LIBBPF_CFLAGS" "$LIBBPF_LDLIBS"
    check_libbpf_function "bpf_prog_test_run_opts" "(0, &opts)" "DECLARE_LIBBPF_OPTS(bpf_test_run_opts, opts, .batch_size = 1)" "$LIBBPF_CFLAGS" "$LIBBPF_LDLIBS"
}

get_libbpf_version()
{
    local libbpf_dir
    local version
    libbpf_dir="$1"

    if [ -f "${libbpf_dir}/libbpf.map" ]; then
        version=$(grep -oE '^LIBBPF_([0-9.]+)' "${libbpf_dir}/libbpf.map" | sort -rV | head -n1 | cut -d'_' -f2)
    else
        version=unknown
    fi

    echo $version
}

check_libbpf()
{
    local libbpf_err

    if [ "${FORCE_SUBDIR_LIBBPF:-0}" -ne "1" ] && ${PKG_CONFIG} libbpf --exists && [ -z "$LIBBPF_DIR" ]; then

        LIBBPF_CFLAGS=$(${PKG_CONFIG} libbpf --cflags)
        LIBBPF_LDLIBS=$(${PKG_CONFIG} libbpf --libs)
        LIBBPF_VERSION=$(${PKG_CONFIG} libbpf --modversion)

        cat >$TMPDIR/libbpftest.c <<EOF
#include <bpf/libbpf.h>
#include <bpf/bpf.h>
#include <bpf/btf.h>
int main(int argc, char **argv) {
    void *ptr;
    DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts, .pin_root_path = "/path");
    DECLARE_LIBBPF_OPTS(bpf_link_create_opts, lopts, .target_btf_id = 0);
    (void) bpf_object__open_file("file", &opts);
    (void) bpf_program__name(ptr);
    (void) bpf_map__set_initial_value(ptr, ptr, 0);
    return 0;
}
EOF

        libbpf_err=$($CC -o $TMPDIR/libbpftest $TMPDIR/libbpftest.c -Werror $LIBBPF_CFLAGS $LIBBPF_LDLIBS 2>&1)
        if [ "$?" -eq "0" ]; then
            echo "SYSTEM_LIBBPF:=y" >>$CONFIG
            echo "LIBBPF_VERSION=$LIBBPF_VERSION" >>$CONFIG
            echo 'CFLAGS += ' $LIBBPF_CFLAGS >> $CONFIG
            echo 'LDLIBS += ' $LIBBPF_LDLIBS >>$CONFIG
            echo 'OBJECT_LIBBPF = ' >>$CONFIG
            echo "system v$LIBBPF_VERSION"

            check_libbpf_functions "$LIBBPF_CFLAGS" "$LIBBPF_LDLIBS"
            return 0
        fi
    else
        libbpf_err="${PKG_CONFIG} couldn't find libbpf"
    fi

    if [ "${FORCE_SYSTEM_LIBBPF:-0}" -eq "1" ]; then
        echo "FORCE_SYSTEM_LIBBPF is set, but no usable libbpf found on system"
        echo "error: $libbpf_err"
        rm -f "$CONFIG"
        exit 1
    fi

    if [ -n "$LIBBPF_DIR" ]; then
        [ -z "$LIBBPF_INCLUDE_DIR" ] && LIBBPF_INCLUDE_DIR="$(readlink -m ${LIBBPF_DIR}/include)"
        [ -z "$LIBBPF_LIB_DIR" ] && LIBBPF_LIB_DIR="$(readlink -m ${LIBBPF_DIR}/src)"
        LIBBPF_VERSION=$(get_libbpf_version "$LIBBPF_DIR/src")
        OBJECT_LIBBPF=
        echo "custom v$LIBBPF_VERSION"
        check_libbpf_functions "-I${LIBBPF_INCLUDE_DIR}" "-L${LIBBPF_LIB_DIR} -l:libbpf.a"
    else
        if ! [ -d "lib/libbpf/src" ] && [ -f ".gitmodules" ] && [ -e ".git" ]; then
            git submodule init && git submodule update
        fi

        LIBBPF_VERSION=$(get_libbpf_version "lib/libbpf/src")
        LIBBPF_INCLUDE_DIR='$(LIB_DIR)/libbpf/src/root/usr/include'
        LIBBPF_LIB_DIR='$(LIB_DIR)/libbpf/src'
        OBJECT_LIBBPF="${LIBBPF_LIB_DIR}/libbpf.a"
        echo "submodule v$LIBBPF_VERSION"
        check_libbpf_functions "" ""
    fi

    echo "SYSTEM_LIBBPF:=n" >> $CONFIG
    echo "LIBBPF_VERSION=$LIBBPF_VERSION" >>$CONFIG
    echo "CFLAGS += -I${LIBBPF_INCLUDE_DIR}" >>$CONFIG
    echo "BPF_CFLAGS += -I${LIBBPF_INCLUDE_DIR}" >>$CONFIG
    echo "LDFLAGS += -L${LIBBPF_LIB_DIR}" >>$CONFIG
    echo 'LDLIBS += -l:libbpf.a' >>$CONFIG
    echo "OBJECT_LIBBPF = ${OBJECT_LIBBPF}" >>$CONFIG

    echo -n "zlib support: "
    check_zlib || exit 1

    echo -n "ELF support: "
    check_elf || exit 1

    echo -n "pcap support: "
    check_pcap || exit 1

}

check_secure_getenv()
{
    cat >$TMPDIR/secure_getenv.c <<EOF
#define _GNU_SOURCE
#include <stdlib.h>
int main(int argc, char **argv) {
	secure_getenv("test");
    return 0;
}
EOF
    secure_getenv_err=$($CC -o $TMPDIR/secure_getenv $TMPDIR/secure_getenv.c 2>&1)
    if [ "$?" -eq "0" ]; then
        echo "HAVE_FEATURES += SECURE_GETENV" >>"$CONFIG"
        echo "yes"
    else
        echo "no"
    fi
}

quiet_config()
{
    cat <<EOF
# user can control verbosity similar to kernel builds (e.g., V=1)
ifeq ("\$(origin V)", "command line")
  VERBOSE = \$(V)
endif
ifndef VERBOSE
  VERBOSE = 0
endif
ifeq (\$(VERBOSE),1)
  Q =
else
  Q = @
endif
ifeq (\$(VERBOSE),0)
MAKEFLAGS += --no-print-directory
endif


ifeq (\$(VERBOSE), 0)
    QUIET_CC       = @echo '    CC       '\$@;
    QUIET_CLANG    = @echo '    CLANG    '\$@;
    QUIET_LLC      = @echo '    LLC      '\$@;
    QUIET_LINK     = @echo '    LINK     '\$@;
    QUIET_INSTALL  = @echo '    INSTALL  '\$@;
    QUIET_M4       = @echo '    M4       '\$@;
    QUIET_GEN      = @echo '    GEN      '\$@;
endif
EOF
}

echo "# Generated config" >$CONFIG
quiet_config >> $CONFIG

check_opts
check_toolchain

echo -n "libbpf support: "
check_libbpf

echo -n "secure_getenv support: "
check_secure_getenv

if [ -n "$KERNEL_HEADERS" ]; then
    echo "kernel headers: $KERNEL_HEADERS"
    echo "CFLAGS += -I$KERNEL_HEADERS" >>$CONFIG
    echo "BPF_CFLAGS += -I$KERNEL_HEADERS" >>$CONFIG
fi

mv $CONFIG $CONFIG_FINAL