// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */

#include <stddef.h>
#include <stdbool.h>
#include <linux/bpf.h>
#include <linux/if_ether.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/in.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>
#include "bpf_compiler.h"
#include "xdp_lb_bench_common.h"
#include "bench_bpf_timing.bpf.h"

#ifndef IPPROTO_FRAGMENT
#define IPPROTO_FRAGMENT 44
#endif

/* jhash helpers */

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

#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

static inline __u32 __jhash_nwords(__u32 a, __u32 b, __u32 c, __u32 initval)
{
	a += initval;
	b += initval;
	c += initval;
	__jhash_final(a, b, c);
	return c;
}

static inline __u32 jhash_2words(__u32 a, __u32 b, __u32 initval)
{
	return __jhash_nwords(a, b, 0, initval + JHASH_INITVAL + (2 << 2));
}

static inline __u32 jhash2_4words(const __u32 *k, __u32 initval)
{
	__u32 a, b, c;

	a = b = c = JHASH_INITVAL + (4 << 2) + initval;

	a += k[0]; b += k[1]; c += k[2];
	__jhash_mix(a, b, c);

	a += k[3];
	__jhash_final(a, b, c);

	return c;
}

static __always_inline void ipv4_csum(struct iphdr *iph)
{
	__u16 *next_iph = (__u16 *)iph;
	__u32 csum = 0;
	int i;

	__pragma_loop_unroll_full
	for (i = 0; i < (int)(sizeof(*iph) >> 1); i++)
		csum += *next_iph++;

	csum = (csum & 0xffff) + (csum >> 16);
	csum = (csum & 0xffff) + (csum >> 16);
	iph->check = ~csum;
}

struct {
	__uint(type, BPF_MAP_TYPE_HASH);
	__uint(max_entries, 64);
	__type(key, struct vip_definition);
	__type(value, struct vip_meta);
} vip_map SEC(".maps");

struct lru_inner_map {
	__uint(type, BPF_MAP_TYPE_LRU_HASH);
	__type(key, struct flow_key);
	__type(value, struct real_pos_lru);
	__uint(max_entries, DEFAULT_LRU_SIZE);
} lru_inner SEC(".maps");

struct {
	__uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
	__type(key, __u32);
	__type(value, __u32);
	__uint(max_entries, BENCH_NR_CPUS);
	__array(values, struct lru_inner_map);
} lru_mapping SEC(".maps");

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

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

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

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

struct {
	__uint(type, BPF_MAP_TYPE_ARRAY);
	__uint(max_entries, 1);
	__type(key, __u32);
	__type(value, struct ctl_value);
} ctl_array SEC(".maps");

struct {
	__uint(type, BPF_MAP_TYPE_ARRAY);
	__uint(max_entries, 1);
	__type(key, __u32);
	__type(value, struct vip_definition);
} vip_miss_stats SEC(".maps");

struct {
	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
	__uint(max_entries, MAX_REALS);
	__type(key, __u32);
	__type(value, __u32);
} lru_miss_stats SEC(".maps");

volatile __u32 flow_mask;
volatile __u32 cold_lru;
__u32 batch_gen;

/*
 * old_eth MUST be read BEFORE writing the outer header because
 * bpf_xdp_adjust_head makes them overlap.
 */
static __always_inline int encap_v4(struct xdp_md *xdp, __be32 saddr, __be32 daddr,
				    __u16 payload_len, const __u8 *dst_mac)
{
	struct ethhdr *new_eth, *old_eth;
	void *data, *data_end;
	struct iphdr *iph;

	if (bpf_xdp_adjust_head(xdp, -(int)sizeof(struct iphdr)))
		return -1;

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

	new_eth = data;
	iph     = data + sizeof(struct ethhdr);
	old_eth = data + sizeof(struct iphdr);

	if (new_eth + 1 > data_end || old_eth + 1 > data_end || iph + 1 > data_end)
		return -1;

	__builtin_memcpy(new_eth->h_source, old_eth->h_dest, sizeof(new_eth->h_source));
	__builtin_memcpy(new_eth->h_dest, dst_mac, sizeof(new_eth->h_dest));
	new_eth->h_proto = bpf_htons(ETH_P_IP);

	__builtin_memset(iph, 0, sizeof(*iph));
	iph->version  = 4;
	iph->ihl      = sizeof(*iph) >> 2;
	iph->protocol = IPPROTO_IPIP;
	iph->tot_len  = bpf_htons(payload_len + sizeof(*iph));
	iph->ttl      = 64;
	iph->saddr    = saddr;
	iph->daddr    = daddr;
	ipv4_csum(iph);

	return 0;
}

static __always_inline int encap_v6(struct xdp_md *xdp, const __be32 saddr[4],
				    const __be32 daddr[4], __u8 nexthdr, __u16 payload_len,
				    const __u8 *dst_mac)
{
	struct ethhdr *new_eth, *old_eth;
	void *data, *data_end;
	struct ipv6hdr *ip6h;

	if (bpf_xdp_adjust_head(xdp, -(int)sizeof(struct ipv6hdr)))
		return -1;

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

	new_eth = data;
	ip6h    = data + sizeof(struct ethhdr);
	old_eth = data + sizeof(struct ipv6hdr);

	if (new_eth + 1 > data_end || old_eth + 1 > data_end || ip6h + 1 > data_end)
		return -1;

	__builtin_memcpy(new_eth->h_source, old_eth->h_dest, sizeof(new_eth->h_source));
	__builtin_memcpy(new_eth->h_dest, dst_mac, sizeof(new_eth->h_dest));
	new_eth->h_proto = bpf_htons(ETH_P_IPV6);

	__builtin_memset(ip6h, 0, sizeof(*ip6h));
	ip6h->version     = 6;
	ip6h->nexthdr     = nexthdr;
	ip6h->payload_len = bpf_htons(payload_len);
	ip6h->hop_limit   = 64;
	__builtin_memcpy(&ip6h->saddr, saddr, sizeof(ip6h->saddr));
	__builtin_memcpy(&ip6h->daddr, daddr, sizeof(ip6h->daddr));

	return 0;
}

static __always_inline void update_stats(void *map, __u32 key, __u16 bytes)
{
	struct lb_stats *st = bpf_map_lookup_elem(map, &key);

	if (st) {
		st->v1 += 1;
		st->v2 += bytes;
	}
}

static __always_inline void count_action(int action)
{
	struct lb_stats *st;
	__u32 key;

	if (action == XDP_TX)
		key = STATS_XDP_TX;
	else if (action == XDP_PASS)
		key = STATS_XDP_PASS;
	else
		key = STATS_XDP_DROP;

	st = bpf_map_lookup_elem(&stats, &key);
	if (st)
		st->v1 += 1;
}

static __always_inline bool is_under_flood(void)
{
	__u32 key = STATS_NEW_CONN;
	struct lb_stats *conn_st = bpf_map_lookup_elem(&stats, &key);
	__u64 cur_time;

	if (!conn_st)
		return true;

	cur_time = bpf_ktime_get_ns();
	if ((cur_time - conn_st->v2) > ONE_SEC) {
		conn_st->v1 = 1;
		conn_st->v2 = cur_time;
	} else {
		conn_st->v1 += 1;
		if (conn_st->v1 > MAX_CONN_RATE)
			return true;
	}
	return false;
}

static __always_inline struct real_definition *connection_table_lookup(void *lru_map,
								       struct flow_key *flow,
								       __u32 *out_pos)
{
	struct real_pos_lru *dst_lru;
	struct real_definition *real;
	__u32 key;

	dst_lru = bpf_map_lookup_elem(lru_map, flow);
	if (!dst_lru)
		return NULL;

	/* UDP connections use atime-based timeout instead of FIN/RST */
	if (flow->proto == IPPROTO_UDP) {
		__u64 cur_time = bpf_ktime_get_ns();

		if (cur_time - dst_lru->atime > LRU_UDP_TIMEOUT)
			return NULL;
		dst_lru->atime = cur_time;
	}

	key = dst_lru->pos;
	*out_pos = key;
	real = bpf_map_lookup_elem(&reals, &key);
	return real;
}

static __always_inline bool get_packet_dst(struct real_definition **real, struct flow_key *flow,
					   struct vip_meta *vip_info, bool is_v6, void *lru_map,
					   bool is_rst, __u32 *out_pos)
{
	bool under_flood;
	__u32 hash, ch_key;
	__u32 *ch_val;
	__u32 real_pos;

	under_flood = is_under_flood();

	if (is_v6) {
		__u32 src_hash = jhash2_4words((__u32 *)flow->srcv6, MAX_VIPS);

		hash = jhash_2words(src_hash, flow->ports, CH_RING_SIZE);
	} else {
		hash = jhash_2words(flow->src, flow->ports, CH_RING_SIZE);
	}

	ch_key = CH_RING_SIZE * vip_info->vip_num + hash % CH_RING_SIZE;
	ch_val = bpf_map_lookup_elem(&ch_rings, &ch_key);
	if (!ch_val)
		return false;
	real_pos = *ch_val;

	*real = bpf_map_lookup_elem(&reals, &real_pos);
	if (!(*real))
		return false;

	if (!(vip_info->flags & F_LRU_BYPASS) && !under_flood && !is_rst) {
		struct real_pos_lru new_lru = { .pos = real_pos };

		if (flow->proto == IPPROTO_UDP)
			new_lru.atime = bpf_ktime_get_ns();
		bpf_map_update_elem(lru_map, flow, &new_lru, BPF_ANY);
	}

	*out_pos = real_pos;
	return true;
}

static __always_inline void update_vip_lru_miss_stats(struct vip_definition *vip, bool is_v6,
						      __u32 real_idx)
{
	struct vip_definition *miss_vip;
	__u32 key = 0;
	__u32 *cnt;

	miss_vip = bpf_map_lookup_elem(&vip_miss_stats, &key);
	if (!miss_vip)
		return;

	if (is_v6) {
		if (miss_vip->vipv6[0] != vip->vipv6[0] || miss_vip->vipv6[1] != vip->vipv6[1] ||
		    miss_vip->vipv6[2] != vip->vipv6[2] || miss_vip->vipv6[3] != vip->vipv6[3])
			return;
	} else {
		if (miss_vip->vip != vip->vip)
			return;
	}

	if (miss_vip->port != vip->port || miss_vip->proto != vip->proto)
		return;

	cnt = bpf_map_lookup_elem(&lru_miss_stats, &real_idx);
	if (cnt)
		*cnt += 1;
}

static __noinline int process_packet(struct xdp_md *xdp)
{
	void *data     = (void *)(long)xdp->data;
	void *data_end = (void *)(long)xdp->data_end;
	struct ethhdr *eth = data;
	struct real_definition *dst = NULL;
	struct vip_definition vip_def = {};
	struct ctl_value *cval;
	struct flow_key flow = {};
	struct vip_meta *vip_info;
	struct lb_stats *data_stats;
	struct udphdr *uh;
	__be32 tnl_src[4];
	void *lru_map;
	void *l4;
	__u16 payload_len;
	__u32 real_pos = 0, cpu_num, key;
	__u8 proto;
	int action = XDP_DROP;
	bool is_v6, is_syn = false, is_rst = false;

	if (eth + 1 > data_end)
		goto out;

	if (eth->h_proto == bpf_htons(ETH_P_IPV6)) {
		is_v6 = true;
	} else if (eth->h_proto == bpf_htons(ETH_P_IP)) {
		is_v6 = false;
	} else {
		action = XDP_PASS;
		goto out;
	}

	if (is_v6) {
		struct ipv6hdr *ip6h = (void *)(eth + 1);

		if (ip6h + 1 > data_end)
			goto out;
		if (ip6h->nexthdr == IPPROTO_FRAGMENT)
			goto out;

		payload_len = sizeof(struct ipv6hdr) + bpf_ntohs(ip6h->payload_len);
		proto = ip6h->nexthdr;

		__builtin_memcpy(flow.srcv6, &ip6h->saddr, sizeof(flow.srcv6));
		__builtin_memcpy(flow.dstv6, &ip6h->daddr, sizeof(flow.dstv6));
		__builtin_memcpy(vip_def.vipv6, &ip6h->daddr, sizeof(vip_def.vipv6));
		l4 = (void *)(ip6h + 1);
	} else {
		struct iphdr *iph = (void *)(eth + 1);

		if (iph + 1 > data_end)
			goto out;
		if (iph->ihl != 5)
			goto out;
		if (iph->frag_off & bpf_htons(PCKT_FRAGMENTED))
			goto out;

		payload_len = bpf_ntohs(iph->tot_len);
		proto = iph->protocol;

		flow.src    = iph->saddr;
		flow.dst    = iph->daddr;
		vip_def.vip = iph->daddr;
		l4 = (void *)(iph + 1);
	}

	/* TCP and UDP share the same port layout at offset 0 */
	if (proto != IPPROTO_TCP && proto != IPPROTO_UDP) {
		action = XDP_PASS;
		goto out;
	}

	uh = l4;
	if ((void *)(uh + 1) > data_end)
		goto out;
	flow.port16[0] = uh->source;
	flow.port16[1] = uh->dest;

	if (proto == IPPROTO_TCP) {
		struct tcphdr *th = l4;

		if ((void *)(th + 1) > data_end)
			goto out;
		is_syn = th->syn;
		is_rst = th->rst;
	}

	flow.proto    = proto;
	vip_def.port  = flow.port16[1];
	vip_def.proto = proto;

	vip_info = bpf_map_lookup_elem(&vip_map, &vip_def);
	if (!vip_info) {
		action = XDP_PASS;
		goto out;
	}

	key = STATS_LRU;
	data_stats = bpf_map_lookup_elem(&stats, &key);
	if (!data_stats)
		goto out;
	data_stats->v1 += 1;

	cpu_num = bpf_get_smp_processor_id();
	lru_map = bpf_map_lookup_elem(&lru_mapping, &cpu_num);
	if (!lru_map)
		goto out;

	if (!(vip_info->flags & F_LRU_BYPASS) && !is_syn)
		dst = connection_table_lookup(lru_map, &flow, &real_pos);

	if (!dst) {
		if (flow.proto == IPPROTO_TCP) {
			struct lb_stats *miss_st;

			key = STATS_LRU_MISS;
			miss_st = bpf_map_lookup_elem(&stats, &key);
			if (miss_st)
				miss_st->v1 += 1;
		}

		if (!get_packet_dst(&dst, &flow, vip_info, is_v6, lru_map, is_rst, &real_pos))
			goto out;

		update_vip_lru_miss_stats(&vip_def, is_v6, real_pos);
		data_stats->v2 += 1;
	}

	key = 0;
	cval = bpf_map_lookup_elem(&ctl_array, &key);
	if (!cval)
		goto out;

	update_stats(&stats, vip_info->vip_num, payload_len);
	update_stats(&reals_stats, real_pos, payload_len);

	if (is_v6) {
		create_encap_ipv6_src(flow.port16[0], flow.srcv6[0], tnl_src);
		if (encap_v6(xdp, tnl_src, dst->dstv6, IPPROTO_IPV6, payload_len, cval->mac))
			goto out;
	} else if (dst->flags & F_IPV6) {
		create_encap_ipv6_src(flow.port16[0], flow.src, tnl_src);
		if (encap_v6(xdp, tnl_src, dst->dstv6, IPPROTO_IPIP, payload_len, cval->mac))
			goto out;
	} else {
		if (encap_v4(xdp, create_encap_ipv4_src(flow.port16[0], flow.src), dst->dst,
			     payload_len, cval->mac))
			goto out;
	}

	action = XDP_TX;

out:
	count_action(action);
	return action;
}

static __always_inline int strip_encap(struct xdp_md *xdp, const struct ethhdr *saved_eth)
{
	void *data = (void *)(long)xdp->data;
	void *data_end = (void *)(long)xdp->data_end;
	struct ethhdr *eth = data;
	int hdr_sz;

	if (eth + 1 > data_end)
		return -1;

	hdr_sz = (eth->h_proto == bpf_htons(ETH_P_IPV6)) ? (int)sizeof(struct ipv6hdr)
							 : (int)sizeof(struct iphdr);

	if (bpf_xdp_adjust_head(xdp, hdr_sz))
		return -1;

	data     = (void *)(long)xdp->data;
	data_end = (void *)(long)xdp->data_end;
	eth      = data;

	if (eth + 1 > data_end)
		return -1;

	__builtin_memcpy(eth, saved_eth, sizeof(*saved_eth));
	return 0;
}

static __always_inline void randomize_src(struct xdp_md *xdp, int saddr_off, __u32 *rand_state)
{
	void *data     = (void *)(long)xdp->data;
	void *data_end = (void *)(long)xdp->data_end;
	__u32 *saddr   = data + saddr_off;

	*rand_state ^= *rand_state << 13;
	*rand_state ^= *rand_state >> 17;
	*rand_state ^= *rand_state << 5;

	if ((void *)(saddr + 1) <= data_end)
		*saddr = *rand_state & flow_mask;
}

SEC("xdp")
int xdp_lb_bench(struct xdp_md *xdp)
{
	void *data     = (void *)(long)xdp->data;
	void *data_end = (void *)(long)xdp->data_end;
	struct ethhdr *eth = data;
	struct ethhdr saved_eth;
	__u32 rand_state = 0;
	__u32 batch_hash = 0;
	int saddr_off = 0;
	bool is_v6;

	if (eth + 1 > data_end)
		return XDP_DROP;

	__builtin_memcpy(&saved_eth, eth, sizeof(saved_eth));

	is_v6 = (saved_eth.h_proto == bpf_htons(ETH_P_IPV6));

	saddr_off = sizeof(struct ethhdr) + (is_v6 ? offsetof(struct ipv6hdr, saddr) :
					     offsetof(struct iphdr, saddr));

	if (flow_mask)
		rand_state = bpf_get_prandom_u32() | 1;

	if (cold_lru) {
		__u32 *saddr = data + saddr_off;

		batch_gen++;
		batch_hash = (batch_gen + bpf_get_smp_processor_id()) * KNUTH_HASH_MULT;
		if ((void *)(saddr + 1) <= data_end)
			*saddr ^= batch_hash;
	}

	return BENCH_BPF_LOOP(
		process_packet(xdp),
		({
			if (__bench_result == XDP_TX) {
				if (strip_encap(xdp, &saved_eth))
					return XDP_DROP;
				if (rand_state)
					randomize_src(xdp, saddr_off, &rand_state);
			}
			if (cold_lru) {
				void *d = (void *)(long)xdp->data;
				void *de = (void *)(long)xdp->data_end;
				__u32 *__sa = d + saddr_off;

				if ((void *)(__sa + 1) <= de)
					*__sa ^= batch_hash;
			}
		})
	);
}

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