#include <uapi/linux/bpf.h>
#include <uapi/linux/in.h>
#include <uapi/linux/if.h>
#include <uapi/linux/if_ether.h>
#include <uapi/linux/ip.h>
#include <uapi/linux/ipv6.h>
#include <uapi/linux/if_tunnel.h>
#include <bpf/bpf_helpers.h>
#include "bpf_legacy.h"
#define IP_MF           0x2000
#define IP_OFFSET       0x1FFF

struct vlan_hdr {
        __be16 h_vlan_TCI;
        __be16 h_vlan_encapsulated_proto;
};

struct flow_key_record {
        __be32 src;
        __be32 dst;
        union {
                __be32 ports;
                __be16 port16[2];
        };
        __u16 thoff;
        __u8 ip_proto;
};

static inline int proto_ports_offset(__u64 proto)
{
        switch (proto) {
        case IPPROTO_TCP:
        case IPPROTO_UDP:
        case IPPROTO_ESP:
        case IPPROTO_SCTP:
        case IPPROTO_UDPLITE:
                return 0;
        case IPPROTO_AH:
                return 4;
        default:
                return 0;
        }
}

static inline int ip_is_fragment(struct __sk_buff *ctx, __u64 nhoff)
{
        return load_half(ctx, nhoff + offsetof(struct iphdr, frag_off))
                & (IP_MF | IP_OFFSET);
}

static inline __u32 ipv6_addr_hash(struct __sk_buff *ctx, __u64 off)
{
        __u64 w0 = load_word(ctx, off);
        __u64 w1 = load_word(ctx, off + 4);
        __u64 w2 = load_word(ctx, off + 8);
        __u64 w3 = load_word(ctx, off + 12);

        return (__u32)(w0 ^ w1 ^ w2 ^ w3);
}

static inline __u64 parse_ip(struct __sk_buff *skb, __u64 nhoff, __u64 *ip_proto,
                             struct flow_key_record *flow)
{
        __u64 verlen;

        if (unlikely(ip_is_fragment(skb, nhoff)))
                *ip_proto = 0;
        else
                *ip_proto = load_byte(skb, nhoff + offsetof(struct iphdr, protocol));

        if (*ip_proto != IPPROTO_GRE) {
                flow->src = load_word(skb, nhoff + offsetof(struct iphdr, saddr));
                flow->dst = load_word(skb, nhoff + offsetof(struct iphdr, daddr));
        }

        verlen = load_byte(skb, nhoff + 0/*offsetof(struct iphdr, ihl)*/);
        if (likely(verlen == 0x45))
                nhoff += 20;
        else
                nhoff += (verlen & 0xF) << 2;

        return nhoff;
}

static inline __u64 parse_ipv6(struct __sk_buff *skb, __u64 nhoff, __u64 *ip_proto,
                               struct flow_key_record *flow)
{
        *ip_proto = load_byte(skb,
                              nhoff + offsetof(struct ipv6hdr, nexthdr));
        flow->src = ipv6_addr_hash(skb,
                                   nhoff + offsetof(struct ipv6hdr, saddr));
        flow->dst = ipv6_addr_hash(skb,
                                   nhoff + offsetof(struct ipv6hdr, daddr));
        nhoff += sizeof(struct ipv6hdr);

        return nhoff;
}

static inline bool flow_dissector(struct __sk_buff *skb,
                                  struct flow_key_record *flow)
{
        __u64 nhoff = ETH_HLEN;
        __u64 ip_proto;
        __u64 proto = load_half(skb, 12);
        int poff;

        if (proto == ETH_P_8021AD) {
                proto = load_half(skb, nhoff + offsetof(struct vlan_hdr,
                                                        h_vlan_encapsulated_proto));
                nhoff += sizeof(struct vlan_hdr);
        }

        if (proto == ETH_P_8021Q) {
                proto = load_half(skb, nhoff + offsetof(struct vlan_hdr,
                                                        h_vlan_encapsulated_proto));
                nhoff += sizeof(struct vlan_hdr);
        }

        if (likely(proto == ETH_P_IP))
                nhoff = parse_ip(skb, nhoff, &ip_proto, flow);
        else if (proto == ETH_P_IPV6)
                nhoff = parse_ipv6(skb, nhoff, &ip_proto, flow);
        else
                return false;

        switch (ip_proto) {
        case IPPROTO_GRE: {
                struct gre_hdr {
                        __be16 flags;
                        __be16 proto;
                };

                __u64 gre_flags = load_half(skb,
                                            nhoff + offsetof(struct gre_hdr, flags));
                __u64 gre_proto = load_half(skb,
                                            nhoff + offsetof(struct gre_hdr, proto));

                if (gre_flags & (GRE_VERSION|GRE_ROUTING))
                        break;

                proto = gre_proto;
                nhoff += 4;
                if (gre_flags & GRE_CSUM)
                        nhoff += 4;
                if (gre_flags & GRE_KEY)
                        nhoff += 4;
                if (gre_flags & GRE_SEQ)
                        nhoff += 4;

                if (proto == ETH_P_8021Q) {
                        proto = load_half(skb,
                                          nhoff + offsetof(struct vlan_hdr,
                                                           h_vlan_encapsulated_proto));
                        nhoff += sizeof(struct vlan_hdr);
                }

                if (proto == ETH_P_IP)
                        nhoff = parse_ip(skb, nhoff, &ip_proto, flow);
                else if (proto == ETH_P_IPV6)
                        nhoff = parse_ipv6(skb, nhoff, &ip_proto, flow);
                else
                        return false;
                break;
        }
        case IPPROTO_IPIP:
                nhoff = parse_ip(skb, nhoff, &ip_proto, flow);
                break;
        case IPPROTO_IPV6:
                nhoff = parse_ipv6(skb, nhoff, &ip_proto, flow);
                break;
        default:
                break;
        }

        flow->ip_proto = ip_proto;
        poff = proto_ports_offset(ip_proto);
        if (poff >= 0) {
                nhoff += poff;
                flow->ports = load_word(skb, nhoff);
        }

        flow->thoff = (__u16) nhoff;

        return true;
}

struct pair {
        long packets;
        long bytes;
};

struct {
        __uint(type, BPF_MAP_TYPE_HASH);
        __type(key, __be32);
        __type(value, struct pair);
        __uint(max_entries, 1024);
} hash_map SEC(".maps");

SEC("socket2")
int bpf_prog2(struct __sk_buff *skb)
{
        struct flow_key_record flow = {};
        struct pair *value;
        u32 key;

        if (!flow_dissector(skb, &flow))
                return 0;

        key = flow.dst;
        value = bpf_map_lookup_elem(&hash_map, &key);
        if (value) {
                __sync_fetch_and_add(&value->packets, 1);
                __sync_fetch_and_add(&value->bytes, skb->len);
        } else {
                struct pair val = {1, skb->len};

                bpf_map_update_elem(&hash_map, &key, &val, BPF_ANY);
        }
        return 0;
}

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