/* Copyright (C) 2017 Cavium, Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of version 2 of the GNU General Public License
 * as published by the Free Software Foundation.
 */

#include "vmlinux.h"
#include "xdp_sample.bpf.h"
#include "xdp_sample_shared.h"

#define ETH_ALEN        6
#define ETH_P_8021Q     0x8100
#define ETH_P_8021AD    0x88A8

struct trie_value {
        __u8 prefix[4];
        __be64 value;
        int ifindex;
        int metric;
        __be32 gw;
};

/* Key for lpm_trie */
union key_4 {
        u32 b32[2];
        u8 b8[8];
};

struct arp_entry {
        __be64 mac;
        __be32 dst;
};

struct direct_map {
        struct arp_entry arp;
        int ifindex;
        __be64 mac;
};

/* Map for trie implementation */
struct {
        __uint(type, BPF_MAP_TYPE_LPM_TRIE);
        __uint(key_size, 8);
        __uint(value_size, sizeof(struct trie_value));
        __uint(max_entries, 50);
        __uint(map_flags, BPF_F_NO_PREALLOC);
} lpm_map SEC(".maps");

/* Map for ARP table */
struct {
        __uint(type, BPF_MAP_TYPE_HASH);
        __type(key, __be32);
        __type(value, __be64);
        __uint(max_entries, 50);
} arp_table SEC(".maps");

/* Map to keep the exact match entries in the route table */
struct {
        __uint(type, BPF_MAP_TYPE_HASH);
        __type(key, __be32);
        __type(value, struct direct_map);
        __uint(max_entries, 50);
} exact_match SEC(".maps");

struct {
        __uint(type, BPF_MAP_TYPE_DEVMAP);
        __uint(key_size, sizeof(int));
        __uint(value_size, sizeof(int));
        __uint(max_entries, 100);
} tx_port SEC(".maps");

SEC("xdp")
int xdp_router_ipv4_prog(struct xdp_md *ctx)
{
        void *data_end = (void *)(long)ctx->data_end;
        void *data = (void *)(long)ctx->data;
        struct ethhdr *eth = data;
        u64 nh_off = sizeof(*eth);
        struct datarec *rec;
        __be16 h_proto;
        u32 key = 0;

        rec = bpf_map_lookup_elem(&rx_cnt, &key);
        if (rec)
                NO_TEAR_INC(rec->processed);

        if (data + nh_off > data_end)
                goto drop;

        h_proto = eth->h_proto;
        if (h_proto == bpf_htons(ETH_P_8021Q) ||
            h_proto == bpf_htons(ETH_P_8021AD)) {
                struct vlan_hdr *vhdr;

                vhdr = data + nh_off;
                nh_off += sizeof(struct vlan_hdr);
                if (data + nh_off > data_end)
                        goto drop;

                h_proto = vhdr->h_vlan_encapsulated_proto;
        }

        switch (bpf_ntohs(h_proto)) {
        case ETH_P_ARP:
                if (rec)
                        NO_TEAR_INC(rec->xdp_pass);
                return XDP_PASS;
        case ETH_P_IP: {
                struct iphdr *iph = data + nh_off;
                struct direct_map *direct_entry;
                __be64 *dest_mac, *src_mac;
                int forward_to;

                if (iph + 1 > data_end)
                        goto drop;

                direct_entry = bpf_map_lookup_elem(&exact_match, &iph->daddr);

                /* Check for exact match, this would give a faster lookup */
                if (direct_entry && direct_entry->mac &&
                    direct_entry->arp.mac) {
                        src_mac = &direct_entry->mac;
                        dest_mac = &direct_entry->arp.mac;
                        forward_to = direct_entry->ifindex;
                } else {
                        struct trie_value *prefix_value;
                        union key_4 key4;

                        /* Look up in the trie for lpm */
                        key4.b32[0] = 32;
                        key4.b8[4] = iph->daddr & 0xff;
                        key4.b8[5] = (iph->daddr >> 8) & 0xff;
                        key4.b8[6] = (iph->daddr >> 16) & 0xff;
                        key4.b8[7] = (iph->daddr >> 24) & 0xff;

                        prefix_value = bpf_map_lookup_elem(&lpm_map, &key4);
                        if (!prefix_value)
                                goto drop;

                        forward_to = prefix_value->ifindex;
                        src_mac = &prefix_value->value;
                        if (!src_mac)
                                goto drop;

                        dest_mac = bpf_map_lookup_elem(&arp_table, &iph->daddr);
                        if (!dest_mac) {
                                if (!prefix_value->gw)
                                        goto drop;

                                dest_mac = bpf_map_lookup_elem(&arp_table,
                                                               &prefix_value->gw);
                                if (!dest_mac) {
                                        /* Forward the packet to the kernel in
                                         * order to trigger ARP discovery for
                                         * the default gw.
                                         */
                                        if (rec)
                                                NO_TEAR_INC(rec->xdp_pass);
                                        return XDP_PASS;
                                }
                        }
                }

                if (src_mac && dest_mac) {
                        int ret;

                        __builtin_memcpy(eth->h_dest, dest_mac, ETH_ALEN);
                        __builtin_memcpy(eth->h_source, src_mac, ETH_ALEN);

                        ret = bpf_redirect_map(&tx_port, forward_to, 0);
                        if (ret == XDP_REDIRECT) {
                                if (rec)
                                        NO_TEAR_INC(rec->xdp_redirect);
                                return ret;
                        }
                }
        }
        default:
                break;
        }
drop:
        if (rec)
                NO_TEAR_INC(rec->xdp_drop);

        return XDP_DROP;
}

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