// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2022 Intel */

#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>
#include <linux/if_ether.h>
#include <linux/ip.h>
#include <linux/errno.h>
#include "xsk_xdp_common.h"

struct {
        __uint(type, BPF_MAP_TYPE_XSKMAP);
        __uint(max_entries, 2);
        __uint(key_size, sizeof(int));
        __uint(value_size, sizeof(int));
} xsk SEC(".maps");

static unsigned int idx;
int adjust_value = 0;
int count = 0;

SEC("xdp.frags") int xsk_def_prog(struct xdp_md *xdp)
{
        return bpf_redirect_map(&xsk, 0, XDP_DROP);
}

SEC("xdp.frags") int xsk_xdp_drop(struct xdp_md *xdp)
{
        /* Drop every other packet */
        if (idx++ % 2)
                return XDP_DROP;

        return bpf_redirect_map(&xsk, 0, XDP_DROP);
}

SEC("xdp.frags") int xsk_xdp_populate_metadata(struct xdp_md *xdp)
{
        void *data, *data_meta;
        struct xdp_info *meta;
        int err;

        /* Reserve enough for all custom metadata. */
        err = bpf_xdp_adjust_meta(xdp, -(int)sizeof(struct xdp_info));
        if (err)
                return XDP_DROP;

        data = (void *)(long)xdp->data;
        data_meta = (void *)(long)xdp->data_meta;

        if (data_meta + sizeof(struct xdp_info) > data)
                return XDP_DROP;

        meta = data_meta;
        meta->count = count++;

        return bpf_redirect_map(&xsk, 0, XDP_DROP);
}

SEC("xdp") int xsk_xdp_shared_umem(struct xdp_md *xdp)
{
        void *data = (void *)(long)xdp->data;
        void *data_end = (void *)(long)xdp->data_end;
        struct ethhdr *eth = data;

        if (eth + 1 > data_end)
                return XDP_DROP;

        /* Redirecting packets based on the destination MAC address */
        idx = ((unsigned int)(eth->h_dest[5])) / 2;
        if (idx > MAX_SOCKETS)
                return XDP_DROP;

        return bpf_redirect_map(&xsk, idx, XDP_DROP);
}

SEC("xdp.frags") int xsk_xdp_adjust_tail(struct xdp_md *xdp)
{
        __u32 buff_len, curr_buff_len;
        int ret;

        buff_len = bpf_xdp_get_buff_len(xdp);
        if (buff_len == 0)
                return XDP_DROP;

        ret = bpf_xdp_adjust_tail(xdp, adjust_value);
        if (ret < 0) {
                /* Handle unsupported cases */
                if (ret == -EOPNOTSUPP) {
                        /* Set adjust_value to -EOPNOTSUPP to indicate to userspace that this case
                         * is unsupported
                         */
                        adjust_value = -EOPNOTSUPP;
                        return bpf_redirect_map(&xsk, 0, XDP_DROP);
                }

                return XDP_DROP;
        }

        curr_buff_len = bpf_xdp_get_buff_len(xdp);
        if (curr_buff_len != buff_len + adjust_value)
                return XDP_DROP;

        if (curr_buff_len > buff_len) {
                __u32 *pkt_data = (void *)(long)xdp->data;
                __u32 len, words_to_end, seq_num;

                len = curr_buff_len - PKT_HDR_ALIGN;
                words_to_end = len / sizeof(*pkt_data) - 1;
                seq_num = words_to_end;

                /* Convert sequence number to network byte order. Store this in the last 4 bytes of
                 * the packet. Use 'adjust_value' to determine the position at the end of the
                 * packet for storing the sequence number.
                 */
                seq_num = __constant_htonl(words_to_end);
                bpf_xdp_store_bytes(xdp, curr_buff_len - sizeof(seq_num), &seq_num,
                                    sizeof(seq_num));
        }

        return bpf_redirect_map(&xsk, 0, XDP_DROP);
}

char _license[] SEC("license") = "GPL";