/* SPDX-License-Identifier: GPL-2.0 */

#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>

#include <xdp/prog_dispatcher.h>

/* While 'const volatile' sounds a little like an oxymoron, there's reason
 * behind the madness:
 *
 * - const places the data in rodata, where libbpf will mark it as read-only and
 *   frozen on program load, letting the kernel do dead code elimination based
 *   on the values.
 *
 * - volatile prevents the compiler from optimising away the checks based on the
 *   compile-time value of the variables, which is important since we will be
 *   changing the values before loading the program into the kernel.
 */
static volatile const struct xdp_dispatcher_config conf = {};

/* The volatile return value prevents the compiler from assuming it knows the
 * return value and optimising based on that.
 *
 * The function includes a no-op xdp_adjust_tail() call before returning, to
 * make sure the verifier doesn't disallow freplace with programs that
 * invalidate the packet data pointer.
 */
__attribute__ ((noinline))
int prog0(struct xdp_md *ctx) {
        volatile int ret = XDP_DISPATCHER_RETVAL;

        if (!ctx)
          return XDP_ABORTED;

        bpf_xdp_adjust_tail(ctx, 0);
        return ret;
}
__attribute__ ((noinline))
int prog1(struct xdp_md *ctx) {
        volatile int ret = XDP_DISPATCHER_RETVAL;

        if (!ctx)
          return XDP_ABORTED;

        bpf_xdp_adjust_tail(ctx, 0);
        return ret;
}
__attribute__ ((noinline))
int prog2(struct xdp_md *ctx) {
        volatile int ret = XDP_DISPATCHER_RETVAL;

        if (!ctx)
          return XDP_ABORTED;

        bpf_xdp_adjust_tail(ctx, 0);
        return ret;
}
__attribute__ ((noinline))
int prog3(struct xdp_md *ctx) {
        volatile int ret = XDP_DISPATCHER_RETVAL;

        if (!ctx)
          return XDP_ABORTED;

        bpf_xdp_adjust_tail(ctx, 0);
        return ret;
}
__attribute__ ((noinline))
int prog4(struct xdp_md *ctx) {
        volatile int ret = XDP_DISPATCHER_RETVAL;

        if (!ctx)
          return XDP_ABORTED;

        bpf_xdp_adjust_tail(ctx, 0);
        return ret;
}
__attribute__ ((noinline))
int prog5(struct xdp_md *ctx) {
        volatile int ret = XDP_DISPATCHER_RETVAL;

        if (!ctx)
          return XDP_ABORTED;

        bpf_xdp_adjust_tail(ctx, 0);
        return ret;
}
__attribute__ ((noinline))
int prog6(struct xdp_md *ctx) {
        volatile int ret = XDP_DISPATCHER_RETVAL;

        if (!ctx)
          return XDP_ABORTED;

        bpf_xdp_adjust_tail(ctx, 0);
        return ret;
}
__attribute__ ((noinline))
int prog7(struct xdp_md *ctx) {
        volatile int ret = XDP_DISPATCHER_RETVAL;

        if (!ctx)
          return XDP_ABORTED;

        bpf_xdp_adjust_tail(ctx, 0);
        return ret;
}
__attribute__ ((noinline))
int prog8(struct xdp_md *ctx) {
        volatile int ret = XDP_DISPATCHER_RETVAL;

        if (!ctx)
          return XDP_ABORTED;

        bpf_xdp_adjust_tail(ctx, 0);
        return ret;
}
__attribute__ ((noinline))
int prog9(struct xdp_md *ctx) {
        volatile int ret = XDP_DISPATCHER_RETVAL;

        if (!ctx)
          return XDP_ABORTED;

        bpf_xdp_adjust_tail(ctx, 0);
        return ret;
}


__attribute__ ((noinline))
int compat_test(struct xdp_md *ctx) {
        volatile int ret = XDP_DISPATCHER_RETVAL;

        if (!ctx)
          return XDP_ABORTED;
        return ret;
}


SEC("xdp")
int xdp_dispatcher(struct xdp_md *ctx)
{
        __u8 num_progs_enabled = conf.num_progs_enabled;
        int ret;

        if (num_progs_enabled < 1)
                goto out;
        ret = prog0(ctx);
        if (!((1U << ret) & conf.chain_call_actions[0]))
                return ret;

        if (num_progs_enabled < 2)
                goto out;
        ret = prog1(ctx);
        if (!((1U << ret) & conf.chain_call_actions[1]))
                return ret;

        if (num_progs_enabled < 3)
                goto out;
        ret = prog2(ctx);
        if (!((1U << ret) & conf.chain_call_actions[2]))
                return ret;

        if (num_progs_enabled < 4)
                goto out;
        ret = prog3(ctx);
        if (!((1U << ret) & conf.chain_call_actions[3]))
                return ret;

        if (num_progs_enabled < 5)
                goto out;
        ret = prog4(ctx);
        if (!((1U << ret) & conf.chain_call_actions[4]))
                return ret;

        if (num_progs_enabled < 6)
                goto out;
        ret = prog5(ctx);
        if (!((1U << ret) & conf.chain_call_actions[5]))
                return ret;

        if (num_progs_enabled < 7)
                goto out;
        ret = prog6(ctx);
        if (!((1U << ret) & conf.chain_call_actions[6]))
                return ret;

        if (num_progs_enabled < 8)
                goto out;
        ret = prog7(ctx);
        if (!((1U << ret) & conf.chain_call_actions[7]))
                return ret;

        if (num_progs_enabled < 9)
                goto out;
        ret = prog8(ctx);
        if (!((1U << ret) & conf.chain_call_actions[8]))
                return ret;

        if (num_progs_enabled < 10)
                goto out;
        ret = prog9(ctx);
        if (!((1U << ret) & conf.chain_call_actions[9]))
                return ret;

        /* keep a reference to the compat_test() function so we can use it
         * as an freplace target in xdp_multiprog__check_compat() in libxdp
         */
        if (num_progs_enabled < 11)
                goto out;
        ret = compat_test(ctx);
out:
        return XDP_PASS;
}

SEC("xdp")
int xdp_pass(struct xdp_md *ctx)
{
        return XDP_PASS;
}

char _license[] SEC("license") = "GPL";
__uint(dispatcher_version, XDP_DISPATCHER_VERSION) SEC(XDP_METADATA_SECTION);