/* Copyright (c) 2015 PLUMgrid, http://plumgrid.com
 *
 * 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 <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 <uapi/linux/mpls.h>
#include <bpf/bpf_helpers.h>
#include "bpf_legacy.h"
#define IP_MF           0x2000
#define IP_OFFSET       0x1FFF

#define PARSE_VLAN 1
#define PARSE_MPLS 2
#define PARSE_IP 3
#define PARSE_IPV6 4

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];
        };
        __u32 ip_proto;
};

static inline void parse_eth_proto(struct __sk_buff *skb, u32 proto);

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);
}

struct globals {
        struct flow_key_record flow;
};

struct {
        __uint(type, BPF_MAP_TYPE_ARRAY);
        __type(key, __u32);
        __type(value, struct globals);
        __uint(max_entries, 32);
} percpu_map SEC(".maps");

/* user poor man's per_cpu until native support is ready */
static struct globals *this_cpu_globals(void)
{
        u32 key = bpf_get_smp_processor_id();

        return bpf_map_lookup_elem(&percpu_map, &key);
}

/* some simple stats for user space consumption */
struct pair {
        __u64 packets;
        __u64 bytes;
};

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

static void update_stats(struct __sk_buff *skb, struct globals *g)
{
        struct flow_key_record key = g->flow;
        struct pair *value;

        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);
        }
}

static __always_inline void parse_ip_proto(struct __sk_buff *skb,
                                           struct globals *g, __u32 ip_proto)
{
        __u32 nhoff = skb->cb[0];
        int poff;

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

                __u32 gre_flags = load_half(skb,
                                            nhoff + offsetof(struct gre_hdr, flags));
                __u32 gre_proto = load_half(skb,
                                            nhoff + offsetof(struct gre_hdr, proto));

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

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

                skb->cb[0] = nhoff;
                parse_eth_proto(skb, gre_proto);
                break;
        }
        case IPPROTO_IPIP:
                parse_eth_proto(skb, ETH_P_IP);
                break;
        case IPPROTO_IPV6:
                parse_eth_proto(skb, ETH_P_IPV6);
                break;
        case IPPROTO_TCP:
        case IPPROTO_UDP:
                g->flow.ports = load_word(skb, nhoff);
        case IPPROTO_ICMP:
                g->flow.ip_proto = ip_proto;
                update_stats(skb, g);
                break;
        default:
                break;
        }
}

SEC("socket")
int bpf_func_ip(struct __sk_buff *skb)
{
        struct globals *g = this_cpu_globals();
        __u32 nhoff, verlen, ip_proto;

        if (!g)
                return 0;

        nhoff = skb->cb[0];

        if (unlikely(ip_is_fragment(skb, nhoff)))
                return 0;

        ip_proto = load_byte(skb, nhoff + offsetof(struct iphdr, protocol));

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

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

        skb->cb[0] = nhoff;
        parse_ip_proto(skb, g, ip_proto);
        return 0;
}

SEC("socket")
int bpf_func_ipv6(struct __sk_buff *skb)
{
        struct globals *g = this_cpu_globals();
        __u32 nhoff, ip_proto;

        if (!g)
                return 0;

        nhoff = skb->cb[0];

        ip_proto = load_byte(skb,
                             nhoff + offsetof(struct ipv6hdr, nexthdr));
        g->flow.src = ipv6_addr_hash(skb,
                                     nhoff + offsetof(struct ipv6hdr, saddr));
        g->flow.dst = ipv6_addr_hash(skb,
                                     nhoff + offsetof(struct ipv6hdr, daddr));
        nhoff += sizeof(struct ipv6hdr);

        skb->cb[0] = nhoff;
        parse_ip_proto(skb, g, ip_proto);
        return 0;
}

SEC("socket")
int bpf_func_vlan(struct __sk_buff *skb)
{
        __u32 nhoff, proto;

        nhoff = skb->cb[0];

        proto = load_half(skb, nhoff + offsetof(struct vlan_hdr,
                                                h_vlan_encapsulated_proto));
        nhoff += sizeof(struct vlan_hdr);
        skb->cb[0] = nhoff;

        parse_eth_proto(skb, proto);

        return 0;
}

SEC("socket")
int bpf_func_mpls(struct __sk_buff *skb)
{
        __u32 nhoff, label;

        nhoff = skb->cb[0];

        label = load_word(skb, nhoff);
        nhoff += sizeof(struct mpls_label);
        skb->cb[0] = nhoff;

        if (label & MPLS_LS_S_MASK) {
                __u8 verlen = load_byte(skb, nhoff);
                if ((verlen & 0xF0) == 4)
                        parse_eth_proto(skb, ETH_P_IP);
                else
                        parse_eth_proto(skb, ETH_P_IPV6);
        } else {
                parse_eth_proto(skb, ETH_P_MPLS_UC);
        }

        return 0;
}

struct {
        __uint(type, BPF_MAP_TYPE_PROG_ARRAY);
        __uint(key_size, sizeof(u32));
        __uint(max_entries, 8);
        __array(values, u32 (void *));
} prog_array_init SEC(".maps") = {
        .values = {
                [PARSE_VLAN] = (void *)&bpf_func_vlan,
                [PARSE_IP]   = (void *)&bpf_func_ip,
                [PARSE_IPV6] = (void *)&bpf_func_ipv6,
                [PARSE_MPLS] = (void *)&bpf_func_mpls,
        },
};

/* Protocol dispatch routine. It tail-calls next BPF program depending
 * on eth proto. Note, we could have used ...
 *
 *   bpf_tail_call(skb, &prog_array_init, proto);
 *
 * ... but it would need large prog_array and cannot be optimised given
 * the map key is not static.
 */
static inline void parse_eth_proto(struct __sk_buff *skb, u32 proto)
{
        switch (proto) {
        case ETH_P_8021Q:
        case ETH_P_8021AD:
                bpf_tail_call(skb, &prog_array_init, PARSE_VLAN);
                break;
        case ETH_P_MPLS_UC:
        case ETH_P_MPLS_MC:
                bpf_tail_call(skb, &prog_array_init, PARSE_MPLS);
                break;
        case ETH_P_IP:
                bpf_tail_call(skb, &prog_array_init, PARSE_IP);
                break;
        case ETH_P_IPV6:
                bpf_tail_call(skb, &prog_array_init, PARSE_IPV6);
                break;
        }
}

SEC("socket")
int main_prog(struct __sk_buff *skb)
{
        __u32 nhoff = ETH_HLEN;
        __u32 proto = load_half(skb, 12);

        skb->cb[0] = nhoff;
        parse_eth_proto(skb, proto);
        return 0;
}

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