// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2017 Facebook
#include <stddef.h>
#include <stdbool.h>
#include <string.h>
#include <linux/pkt_cls.h>
#include <linux/bpf.h>
#include <linux/in.h>
#include <linux/if_ether.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/icmp.h>
#include <linux/icmpv6.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>
#include "bpf_compiler.h"

static __always_inline __u32 rol32(__u32 word, unsigned int shift)
{
        return (word << shift) | (word >> ((-shift) & 31));
}

/* copy paste of jhash from kernel sources to make sure llvm
 * can compile it into valid sequence of bpf instructions
 */
#define __jhash_mix(a, b, c)                    \
{                                               \
        a -= c;  a ^= rol32(c, 4);  c += b;     \
        b -= a;  b ^= rol32(a, 6);  a += c;     \
        c -= b;  c ^= rol32(b, 8);  b += a;     \
        a -= c;  a ^= rol32(c, 16); c += b;     \
        b -= a;  b ^= rol32(a, 19); a += c;     \
        c -= b;  c ^= rol32(b, 4);  b += a;     \
}

#define __jhash_final(a, b, c)                  \
{                                               \
        c ^= b; c -= rol32(b, 14);              \
        a ^= c; a -= rol32(c, 11);              \
        b ^= a; b -= rol32(a, 25);              \
        c ^= b; c -= rol32(b, 16);              \
        a ^= c; a -= rol32(c, 4);               \
        b ^= a; b -= rol32(a, 14);              \
        c ^= b; c -= rol32(b, 24);              \
}

#define JHASH_INITVAL           0xdeadbeef

typedef unsigned int u32;

static __noinline
u32 jhash(const void *key, u32 length, u32 initval)
{
        u32 a, b, c;
        const unsigned char *k = key;

        a = b = c = JHASH_INITVAL + length + initval;

        while (length > 12) {
                a += *(u32 *)(k);
                b += *(u32 *)(k + 4);
                c += *(u32 *)(k + 8);
                __jhash_mix(a, b, c);
                length -= 12;
                k += 12;
        }
        switch (length) {
        case 12: c += (u32)k[11]<<24;
        case 11: c += (u32)k[10]<<16;
        case 10: c += (u32)k[9]<<8;
        case 9:  c += k[8];
        case 8:  b += (u32)k[7]<<24;
        case 7:  b += (u32)k[6]<<16;
        case 6:  b += (u32)k[5]<<8;
        case 5:  b += k[4];
        case 4:  a += (u32)k[3]<<24;
        case 3:  a += (u32)k[2]<<16;
        case 2:  a += (u32)k[1]<<8;
        case 1:  a += k[0];
                 __jhash_final(a, b, c);
        case 0: /* Nothing left to add */
                break;
        }

        return c;
}

__noinline
u32 __jhash_nwords(u32 a, u32 b, u32 c, u32 initval)
{
        a += initval;
        b += initval;
        c += initval;
        __jhash_final(a, b, c);
        return c;
}

__noinline
u32 jhash_2words(u32 a, u32 b, u32 initval)
{
        return __jhash_nwords(a, b, 0, initval + JHASH_INITVAL + (2 << 2));
}

struct flow_key {
        union {
                __be32 src;
                __be32 srcv6[4];
        };
        union {
                __be32 dst;
                __be32 dstv6[4];
        };
        union {
                __u32 ports;
                __u16 port16[2];
        };
        __u8 proto;
};

struct packet_description {
        struct flow_key flow;
        __u8 flags;
};

struct ctl_value {
        union {
                __u64 value;
                __u32 ifindex;
                __u8 mac[6];
        };
};

struct vip_definition {
        union {
                __be32 vip;
                __be32 vipv6[4];
        };
        __u16 port;
        __u16 family;
        __u8 proto;
};

struct vip_meta {
        __u32 flags;
        __u32 vip_num;
};

struct real_pos_lru {
        __u32 pos;
        __u64 atime;
};

struct real_definition {
        union {
                __be32 dst;
                __be32 dstv6[4];
        };
        __u8 flags;
};

struct lb_stats {
        __u64 v2;
        __u64 v1;
};

struct {
        __uint(type, BPF_MAP_TYPE_HASH);
        __uint(max_entries, 512);
        __type(key, struct vip_definition);
        __type(value, struct vip_meta);
} vip_map SEC(".maps");

struct {
        __uint(type, BPF_MAP_TYPE_LRU_HASH);
        __uint(max_entries, 300);
        __uint(map_flags, 1U << 1);
        __type(key, struct flow_key);
        __type(value, struct real_pos_lru);
} lru_cache SEC(".maps");

struct {
        __uint(type, BPF_MAP_TYPE_ARRAY);
        __uint(max_entries, 12 * 655);
        __type(key, __u32);
        __type(value, __u32);
} ch_rings SEC(".maps");

struct {
        __uint(type, BPF_MAP_TYPE_ARRAY);
        __uint(max_entries, 40);
        __type(key, __u32);
        __type(value, struct real_definition);
} reals SEC(".maps");

struct {
        __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
        __uint(max_entries, 515);
        __type(key, __u32);
        __type(value, struct lb_stats);
} stats SEC(".maps");

struct {
        __uint(type, BPF_MAP_TYPE_ARRAY);
        __uint(max_entries, 16);
        __type(key, __u32);
        __type(value, struct ctl_value);
} ctl_array SEC(".maps");

struct eth_hdr {
        unsigned char eth_dest[6];
        unsigned char eth_source[6];
        unsigned short eth_proto;
};

static __noinline __u64 calc_offset(bool is_ipv6, bool is_icmp)
{
        __u64 off = sizeof(struct eth_hdr);
        if (is_ipv6) {
                off += sizeof(struct ipv6hdr);
                if (is_icmp)
                        off += sizeof(struct icmp6hdr) + sizeof(struct ipv6hdr);
        } else {
                off += sizeof(struct iphdr);
                if (is_icmp)
                        off += sizeof(struct icmphdr) + sizeof(struct iphdr);
        }
        return off;
}

static __attribute__ ((noinline))
bool parse_udp(void *data, void *data_end,
               bool is_ipv6, struct packet_description *pckt)
{

        bool is_icmp = !((pckt->flags & (1 << 0)) == 0);
        __u64 off = calc_offset(is_ipv6, is_icmp);
        struct udphdr *udp;
        udp = data + off;

        if (udp + 1 > data_end)
                return false;
        if (!is_icmp) {
                pckt->flow.port16[0] = udp->source;
                pckt->flow.port16[1] = udp->dest;
        } else {
                pckt->flow.port16[0] = udp->dest;
                pckt->flow.port16[1] = udp->source;
        }
        return true;
}

static __attribute__ ((noinline))
bool parse_tcp(void *data, void *data_end,
               bool is_ipv6, struct packet_description *pckt)
{

        bool is_icmp = !((pckt->flags & (1 << 0)) == 0);
        __u64 off = calc_offset(is_ipv6, is_icmp);
        struct tcphdr *tcp;

        tcp = data + off;
        if (tcp + 1 > data_end)
                return false;
        if (tcp->syn)
                pckt->flags |= (1 << 1);
        if (!is_icmp) {
                pckt->flow.port16[0] = tcp->source;
                pckt->flow.port16[1] = tcp->dest;
        } else {
                pckt->flow.port16[0] = tcp->dest;
                pckt->flow.port16[1] = tcp->source;
        }
        return true;
}

static __attribute__ ((noinline))
bool encap_v6(struct xdp_md *xdp, struct ctl_value *cval,
              struct packet_description *pckt,
              struct real_definition *dst, __u32 pkt_bytes)
{
        struct eth_hdr *new_eth;
        struct eth_hdr *old_eth;
        struct ipv6hdr *ip6h;
        __u32 ip_suffix;
        void *data_end;
        void *data;

        if (bpf_xdp_adjust_head(xdp, 0 - (int)sizeof(struct ipv6hdr)))
                return false;
        data = (void *)(long)xdp->data;
        data_end = (void *)(long)xdp->data_end;
        new_eth = data;
        ip6h = data + sizeof(struct eth_hdr);
        old_eth = data + sizeof(struct ipv6hdr);
        if (new_eth + 1 > data_end ||
            old_eth + 1 > data_end || ip6h + 1 > data_end)
                return false;
        memcpy(new_eth->eth_dest, cval->mac, 6);
        memcpy(new_eth->eth_source, old_eth->eth_dest, 6);
        new_eth->eth_proto = 56710;
        ip6h->version = 6;
        ip6h->priority = 0;
        memset(ip6h->flow_lbl, 0, sizeof(ip6h->flow_lbl));

        ip6h->nexthdr = IPPROTO_IPV6;
        ip_suffix = pckt->flow.srcv6[3] ^ pckt->flow.port16[0];
        ip6h->payload_len =
            bpf_htons(pkt_bytes + sizeof(struct ipv6hdr));
        ip6h->hop_limit = 4;

        ip6h->saddr.in6_u.u6_addr32[0] = 1;
        ip6h->saddr.in6_u.u6_addr32[1] = 2;
        ip6h->saddr.in6_u.u6_addr32[2] = 3;
        ip6h->saddr.in6_u.u6_addr32[3] = ip_suffix;
        memcpy(ip6h->daddr.in6_u.u6_addr32, dst->dstv6, 16);
        return true;
}

#ifndef __clang__
#pragma GCC push_options
/* GCC optimization collapses functions and increases the number of arguments
 * beyond the compatible amount supported by BPF.
 */
#pragma GCC optimize("-fno-ipa-sra")
#endif

static __attribute__ ((noinline))
bool encap_v4(struct xdp_md *xdp, struct ctl_value *cval,
              struct packet_description *pckt,
              struct real_definition *dst, __u32 pkt_bytes)
{

        __u32 ip_suffix = bpf_ntohs(pckt->flow.port16[0]);
        struct eth_hdr *new_eth;
        struct eth_hdr *old_eth;
        __u16 *next_iph_u16;
        struct iphdr *iph;
        __u32 csum = 0;
        void *data_end;
        void *data;

        ip_suffix <<= 15;
        ip_suffix ^= pckt->flow.src;
        if (bpf_xdp_adjust_head(xdp, 0 - (int)sizeof(struct iphdr)))
                return false;
        data = (void *)(long)xdp->data;
        data_end = (void *)(long)xdp->data_end;
        new_eth = data;
        iph = data + sizeof(struct eth_hdr);
        old_eth = data + sizeof(struct iphdr);
        if (new_eth + 1 > data_end ||
            old_eth + 1 > data_end || iph + 1 > data_end)
                return false;
        memcpy(new_eth->eth_dest, cval->mac, 6);
        memcpy(new_eth->eth_source, old_eth->eth_dest, 6);
        new_eth->eth_proto = 8;
        iph->version = 4;
        iph->ihl = 5;
        iph->frag_off = 0;
        iph->protocol = IPPROTO_IPIP;
        iph->check = 0;
        iph->tos = 1;
        iph->tot_len = bpf_htons(pkt_bytes + sizeof(struct iphdr));
        /* don't update iph->daddr, since it will overwrite old eth_proto
         * and multiple iterations of bpf_prog_run() will fail
         */

        iph->saddr = ((0xFFFF0000 & ip_suffix) | 4268) ^ dst->dst;
        iph->ttl = 4;

        next_iph_u16 = (__u16 *) iph;
        __pragma_loop_unroll_full
        for (int i = 0; i < sizeof(struct iphdr) >> 1; i++)
                csum += *next_iph_u16++;
        iph->check = ~((csum & 0xffff) + (csum >> 16));
        if (bpf_xdp_adjust_head(xdp, (int)sizeof(struct iphdr)))
                return false;
        return true;
}

#ifndef __clang__
#pragma GCC pop_options
#endif

static __attribute__ ((noinline))
int swap_mac_and_send(void *data, void *data_end)
{
        unsigned char tmp_mac[6];
        struct eth_hdr *eth;

        eth = data;
        memcpy(tmp_mac, eth->eth_source, 6);
        memcpy(eth->eth_source, eth->eth_dest, 6);
        memcpy(eth->eth_dest, tmp_mac, 6);
        return XDP_TX;
}

static __attribute__ ((noinline))
int send_icmp_reply(void *data, void *data_end)
{
        struct icmphdr *icmp_hdr;
        __u16 *next_iph_u16;
        __u32 tmp_addr = 0;
        struct iphdr *iph;
        __u32 csum = 0;
        __u64 off = 0;

        if (data + sizeof(struct eth_hdr)
             + sizeof(struct iphdr) + sizeof(struct icmphdr) > data_end)
                return XDP_DROP;
        off += sizeof(struct eth_hdr);
        iph = data + off;
        off += sizeof(struct iphdr);
        icmp_hdr = data + off;
        icmp_hdr->type = 0;
        icmp_hdr->checksum += 0x0007;
        iph->ttl = 4;
        tmp_addr = iph->daddr;
        iph->daddr = iph->saddr;
        iph->saddr = tmp_addr;
        iph->check = 0;
        next_iph_u16 = (__u16 *) iph;
        __pragma_loop_unroll_full
        for (int i = 0; i < sizeof(struct iphdr) >> 1; i++)
                csum += *next_iph_u16++;
        iph->check = ~((csum & 0xffff) + (csum >> 16));
        return swap_mac_and_send(data, data_end);
}

static __attribute__ ((noinline))
int send_icmp6_reply(void *data, void *data_end)
{
        struct icmp6hdr *icmp_hdr;
        struct ipv6hdr *ip6h;
        __be32 tmp_addr[4];
        __u64 off = 0;

        if (data + sizeof(struct eth_hdr)
             + sizeof(struct ipv6hdr) + sizeof(struct icmp6hdr) > data_end)
                return XDP_DROP;
        off += sizeof(struct eth_hdr);
        ip6h = data + off;
        off += sizeof(struct ipv6hdr);
        icmp_hdr = data + off;
        icmp_hdr->icmp6_type = 129;
        icmp_hdr->icmp6_cksum -= 0x0001;
        ip6h->hop_limit = 4;
        memcpy(tmp_addr, ip6h->saddr.in6_u.u6_addr32, 16);
        memcpy(ip6h->saddr.in6_u.u6_addr32, ip6h->daddr.in6_u.u6_addr32, 16);
        memcpy(ip6h->daddr.in6_u.u6_addr32, tmp_addr, 16);
        return swap_mac_and_send(data, data_end);
}

static __attribute__ ((noinline))
int parse_icmpv6(void *data, void *data_end, __u64 off,
                 struct packet_description *pckt)
{
        struct icmp6hdr *icmp_hdr;
        struct ipv6hdr *ip6h;

        icmp_hdr = data + off;
        if (icmp_hdr + 1 > data_end)
                return XDP_DROP;
        if (icmp_hdr->icmp6_type == 128)
                return send_icmp6_reply(data, data_end);
        if (icmp_hdr->icmp6_type != 3)
                return XDP_PASS;
        off += sizeof(struct icmp6hdr);
        ip6h = data + off;
        if (ip6h + 1 > data_end)
                return XDP_DROP;
        pckt->flow.proto = ip6h->nexthdr;
        pckt->flags |= (1 << 0);
        memcpy(pckt->flow.srcv6, ip6h->daddr.in6_u.u6_addr32, 16);
        memcpy(pckt->flow.dstv6, ip6h->saddr.in6_u.u6_addr32, 16);
        return -1;
}

static __attribute__ ((noinline))
int parse_icmp(void *data, void *data_end, __u64 off,
               struct packet_description *pckt)
{
        struct icmphdr *icmp_hdr;
        struct iphdr *iph;

        icmp_hdr = data + off;
        if (icmp_hdr + 1 > data_end)
                return XDP_DROP;
        if (icmp_hdr->type == 8)
                return send_icmp_reply(data, data_end);
        if ((icmp_hdr->type != 3) || (icmp_hdr->code != 4))
                return XDP_PASS;
        off += sizeof(struct icmphdr);
        iph = data + off;
        if (iph + 1 > data_end)
                return XDP_DROP;
        if (iph->ihl != 5)
                return XDP_DROP;
        pckt->flow.proto = iph->protocol;
        pckt->flags |= (1 << 0);
        pckt->flow.src = iph->daddr;
        pckt->flow.dst = iph->saddr;
        return -1;
}

static __attribute__ ((noinline))
__u32 get_packet_hash(struct packet_description *pckt,
                      bool hash_16bytes)
{
        if (hash_16bytes)
                return jhash_2words(jhash(pckt->flow.srcv6, 16, 12),
                                    pckt->flow.ports, 24);
        else
                return jhash_2words(pckt->flow.src, pckt->flow.ports,
                                    24);
}

__attribute__ ((noinline))
static bool get_packet_dst(struct real_definition **real,
                           struct packet_description *pckt,
                           struct vip_meta *vip_info,
                           bool is_ipv6, void *lru_map)
{
        struct real_pos_lru new_dst_lru = { };
        bool hash_16bytes = is_ipv6;
        __u32 *real_pos, hash, key;
        __u64 cur_time;

        if (vip_info->flags & (1 << 2))
                hash_16bytes = 1;
        if (vip_info->flags & (1 << 3)) {
                pckt->flow.port16[0] = pckt->flow.port16[1];
                memset(pckt->flow.srcv6, 0, 16);
        }
        hash = get_packet_hash(pckt, hash_16bytes);
        if (hash != 0x358459b7 /* jhash of ipv4 packet */  &&
            hash != 0x2f4bc6bb /* jhash of ipv6 packet */)
                return false;
        key = 2 * vip_info->vip_num + hash % 2;
        real_pos = bpf_map_lookup_elem(&ch_rings, &key);
        if (!real_pos)
                return false;
        key = *real_pos;
        *real = bpf_map_lookup_elem(&reals, &key);
        if (!(*real))
                return false;
        if (!(vip_info->flags & (1 << 1))) {
                __u32 conn_rate_key = 512 + 2;
                struct lb_stats *conn_rate_stats =
                    bpf_map_lookup_elem(&stats, &conn_rate_key);

                if (!conn_rate_stats)
                        return true;
                cur_time = bpf_ktime_get_ns();
                if ((cur_time - conn_rate_stats->v2) >> 32 > 0xffFFFF) {
                        conn_rate_stats->v1 = 1;
                        conn_rate_stats->v2 = cur_time;
                } else {
                        conn_rate_stats->v1 += 1;
                        if (conn_rate_stats->v1 >= 1)
                                return true;
                }
                if (pckt->flow.proto == IPPROTO_UDP)
                        new_dst_lru.atime = cur_time;
                new_dst_lru.pos = key;
                bpf_map_update_elem(lru_map, &pckt->flow, &new_dst_lru, 0);
        }
        return true;
}

__attribute__ ((noinline))
static void connection_table_lookup(struct real_definition **real,
                                    struct packet_description *pckt,
                                    void *lru_map)
{

        struct real_pos_lru *dst_lru;
        __u64 cur_time;
        __u32 key;

        dst_lru = bpf_map_lookup_elem(lru_map, &pckt->flow);
        if (!dst_lru)
                return;
        if (pckt->flow.proto == IPPROTO_UDP) {
                cur_time = bpf_ktime_get_ns();
                if (cur_time - dst_lru->atime > 300000)
                        return;
                dst_lru->atime = cur_time;
        }
        key = dst_lru->pos;
        *real = bpf_map_lookup_elem(&reals, &key);
}

/* don't believe your eyes!
 * below function has 6 arguments whereas bpf and llvm allow maximum of 5
 * but since it's _static_ llvm can optimize one argument away
 */
__attribute__ ((noinline))
static int process_l3_headers_v6(struct packet_description *pckt,
                                 __u8 *protocol, __u64 off,
                                 __u16 *pkt_bytes, void *extra_args[2])
{
        struct ipv6hdr *ip6h;
        __u64 iph_len;
        int action;
        void *data = extra_args[0];
        void *data_end = extra_args[1];

        ip6h = data + off;
        if (ip6h + 1 > data_end)
                return XDP_DROP;
        iph_len = sizeof(struct ipv6hdr);
        *protocol = ip6h->nexthdr;
        pckt->flow.proto = *protocol;
        *pkt_bytes = bpf_ntohs(ip6h->payload_len);
        off += iph_len;
        if (*protocol == 45) {
                return XDP_DROP;
        } else if (*protocol == 59) {
                action = parse_icmpv6(data, data_end, off, pckt);
                if (action >= 0)
                        return action;
        } else {
                memcpy(pckt->flow.srcv6, ip6h->saddr.in6_u.u6_addr32, 16);
                memcpy(pckt->flow.dstv6, ip6h->daddr.in6_u.u6_addr32, 16);
        }
        return -1;
}

__attribute__ ((noinline))
static int process_l3_headers_v4(struct packet_description *pckt,
                                 __u8 *protocol, __u64 off,
                                 __u16 *pkt_bytes, void *extra_args[2])
{
        struct iphdr *iph;
        int action;
        void *data = extra_args[0];
        void *data_end = extra_args[1];

        iph = data + off;
        if (iph + 1 > data_end)
                return XDP_DROP;
        if (iph->ihl != 5)
                return XDP_DROP;
        *protocol = iph->protocol;
        pckt->flow.proto = *protocol;
        *pkt_bytes = bpf_ntohs(iph->tot_len);
        off += 20;
        if (iph->frag_off & 65343)
                return XDP_DROP;
        if (*protocol == IPPROTO_ICMP) {
                action = parse_icmp(data, data_end, off, pckt);
                if (action >= 0)
                        return action;
        } else {
                pckt->flow.src = iph->saddr;
                pckt->flow.dst = iph->daddr;
        }
        return -1;
}

__attribute__ ((noinline))
static int process_packet(void *data, __u64 off, void *data_end,
                          bool is_ipv6, struct xdp_md *xdp)
{

        struct real_definition *dst = NULL;
        struct packet_description pckt = { };
        struct vip_definition vip = { };
        struct lb_stats *data_stats;
        void *lru_map = &lru_cache;
        struct vip_meta *vip_info;
        __u32 lru_stats_key = 513;
        __u32 mac_addr_pos = 0;
        __u32 stats_key = 512;
        struct ctl_value *cval;
        __u16 pkt_bytes;
        __u8 protocol;
        __u32 vip_num;
        int action;
        void *extra_args[2] = { data, data_end };

        if (is_ipv6)
                action = process_l3_headers_v6(&pckt, &protocol, off,
                                               &pkt_bytes, extra_args);
        else
                action = process_l3_headers_v4(&pckt, &protocol, off,
                                               &pkt_bytes, extra_args);
        if (action >= 0)
                return action;
        protocol = pckt.flow.proto;
        if (protocol == IPPROTO_TCP) {
                if (!parse_tcp(data, data_end, is_ipv6, &pckt))
                        return XDP_DROP;
        } else if (protocol == IPPROTO_UDP) {
                if (!parse_udp(data, data_end, is_ipv6, &pckt))
                        return XDP_DROP;
        } else {
                return XDP_TX;
        }

        if (is_ipv6)
                memcpy(vip.vipv6, pckt.flow.dstv6, 16);
        else
                vip.vip = pckt.flow.dst;
        vip.port = pckt.flow.port16[1];
        vip.proto = pckt.flow.proto;
        vip_info = bpf_map_lookup_elem(&vip_map, &vip);
        if (!vip_info) {
                vip.port = 0;
                vip_info = bpf_map_lookup_elem(&vip_map, &vip);
                if (!vip_info)
                        return XDP_PASS;
                if (!(vip_info->flags & (1 << 4)))
                        pckt.flow.port16[1] = 0;
        }
        if (data_end - data > 1400)
                return XDP_DROP;
        data_stats = bpf_map_lookup_elem(&stats, &stats_key);
        if (!data_stats)
                return XDP_DROP;
        data_stats->v1 += 1;
        if (!dst) {
                if (vip_info->flags & (1 << 0))
                        pckt.flow.port16[0] = 0;
                if (!(pckt.flags & (1 << 1)) && !(vip_info->flags & (1 << 1)))
                        connection_table_lookup(&dst, &pckt, lru_map);
                if (dst)
                        goto out;
                if (pckt.flow.proto == IPPROTO_TCP) {
                        struct lb_stats *lru_stats =
                            bpf_map_lookup_elem(&stats, &lru_stats_key);

                        if (!lru_stats)
                                return XDP_DROP;
                        if (pckt.flags & (1 << 1))
                                lru_stats->v1 += 1;
                        else
                                lru_stats->v2 += 1;
                }
                if (!get_packet_dst(&dst, &pckt, vip_info, is_ipv6, lru_map))
                        return XDP_DROP;
                data_stats->v2 += 1;
        }
out:
        cval = bpf_map_lookup_elem(&ctl_array, &mac_addr_pos);
        if (!cval)
                return XDP_DROP;
        if (dst->flags & (1 << 0)) {
                if (!encap_v6(xdp, cval, &pckt, dst, pkt_bytes))
                        return XDP_DROP;
        } else {
                if (!encap_v4(xdp, cval, &pckt, dst, pkt_bytes))
                        return XDP_DROP;
        }
        vip_num = vip_info->vip_num;
        data_stats = bpf_map_lookup_elem(&stats, &vip_num);
        if (!data_stats)
                return XDP_DROP;
        data_stats->v1 += 1;
        data_stats->v2 += pkt_bytes;

        data = (void *)(long)xdp->data;
        data_end = (void *)(long)xdp->data_end;
        if (data + 4 > data_end)
                return XDP_DROP;
        *(u32 *)data = dst->dst;
        return XDP_DROP;
}

SEC("xdp")
int balancer_ingress_v4(struct xdp_md *ctx)
{
        void *data = (void *)(long)ctx->data;
        void *data_end = (void *)(long)ctx->data_end;
        struct eth_hdr *eth = data;
        __u32 eth_proto;
        __u32 nh_off;

        nh_off = sizeof(struct eth_hdr);
        if (data + nh_off > data_end)
                return XDP_DROP;
        eth_proto = bpf_ntohs(eth->eth_proto);
        if (eth_proto == ETH_P_IP)
                return process_packet(data, nh_off, data_end, 0, ctx);
        else
                return XDP_DROP;
}

SEC("xdp")
int balancer_ingress_v6(struct xdp_md *ctx)
{
        void *data = (void *)(long)ctx->data;
        void *data_end = (void *)(long)ctx->data_end;
        struct eth_hdr *eth = data;
        __u32 eth_proto;
        __u32 nh_off;

        nh_off = sizeof(struct eth_hdr);
        if (data + nh_off > data_end)
                return XDP_DROP;
        eth_proto = bpf_ntohs(eth->eth_proto);
        if (eth_proto == ETH_P_IPV6)
                return process_packet(data, nh_off, data_end, 1, ctx);
        else
                return XDP_DROP;
}

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