/*
 *  Copyright (C) 2019 Authors of Cilium
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#include <node_config.h>
#include <netdev_config.h>

#include <bpf/api.h>

#include <stdint.h>
#include <stdio.h>

#define SKIP_POLICY_MAP	1
#define SKIP_CALLS_MAP	1

#include "lib/utils.h"
#include "lib/common.h"
#include "lib/lb.h"
#include "lib/eps.h"
#include "lib/metrics.h"

#define SYS_REJECT	0
#define SYS_PROCEED	1

static __always_inline __maybe_unused bool is_v4_loopback(__be32 daddr)
{
	/* Check for 127.0.0.0/8 range, RFC3330. */
	return (daddr & bpf_htonl(0x7f000000)) == bpf_htonl(0x7f000000);
}

static __always_inline __maybe_unused bool is_v6_loopback(union v6addr *daddr)
{
	/* Check for ::1/128, RFC4291. */
	union v6addr loopback = { .addr[15] = 1, };
	return ipv6_addrcmp(&loopback, daddr) == 0;
}

static __always_inline __maybe_unused bool is_v4_in_v6(union v6addr *daddr)
{
	/* Check for ::FFFF:<IPv4 address>. */
	union v6addr dprobe  = {
		.addr[10] = 0xff,
		.addr[11] = 0xff,
	};
	union v6addr dmasked = {
		.d1 = daddr->d1,
	};
	dmasked.p3 = daddr->p3;
	return ipv6_addrcmp(&dprobe, &dmasked) == 0;
}

static __always_inline __maybe_unused void build_v4_in_v6(union v6addr *daddr,
							  __be32 v4)
{
	__builtin_memset(daddr, 0, sizeof(*daddr));
	daddr->addr[10] = 0xff;
	daddr->addr[11] = 0xff;
	daddr->p4 = v4;
}

/* Hack due to missing narrow ctx access. */
static __always_inline __maybe_unused __be16
ctx_dst_port(struct bpf_sock_addr *ctx)
{
	volatile __u32 dport = ctx->user_port;
	return (__be16)dport;
}

static __always_inline __maybe_unused __be16
ctx_src_port(struct bpf_sock *ctx)
{
	volatile __u32 sport = ctx->src_port;
	return (__be16)bpf_htons(sport);
}

static __always_inline __maybe_unused
void ctx_set_port(struct bpf_sock_addr *ctx, __be16 dport)
{
	ctx->user_port = (__u32)dport;
}

static __always_inline __maybe_unused
__u64 sock_local_cookie(struct bpf_sock_addr *ctx)
{
#ifdef HAVE_GET_SOCK_COOKIE
	/* prandom() breaks down on UDP, hence preference is on
	 * socket cookie as built-in selector. On older kernels,
	 * get_socket_cookie() provides a unique per netns cookie
	 * for the life-time of the socket. For newer kernels this
	 * is fixed to be a unique system _global_ cookie. Older
	 * kernels could have a cookie collision when two pods with
	 * different netns talk to same service backend, but that
	 * is fine since we always reverse translate to the same
	 * service IP/port pair. The only case that could happen
	 * for older kernels is that we have a cookie collision
	 * where one pod talks to the service IP/port and the
	 * other pod talks to that same specific backend IP/port
	 * directly _w/o_ going over service IP/port. Then the
	 * reverse sock addr is translated to the service IP/port.
	 * With a global socket cookie this collision cannot take
	 * place. There, only the even more unlikely case could
	 * happen where the same UDP socket talks first to the
	 * service and then to the same selected backend IP/port
	 * directly which can be considered negligible.
	 */
	return get_socket_cookie(ctx);
#else
	return ctx->protocol == IPPROTO_TCP ? get_prandom_u32() : 0;
#endif
}

static __always_inline __maybe_unused
bool sock_proto_enabled(uint32_t proto)
{
	switch (proto) {
#ifdef ENABLE_HOST_SERVICES_TCP
	case IPPROTO_TCP:
		return true;
#endif /* ENABLE_HOST_SERVICES_TCP */
#ifdef ENABLE_HOST_SERVICES_UDP
	case IPPROTO_UDPLITE:
	case IPPROTO_UDP:
		return true;
#endif /* ENABLE_HOST_SERVICES_UDP */
	default:
		return false;
	}
}

#ifdef ENABLE_IPV4
#ifdef ENABLE_HOST_SERVICES_UDP
struct ipv4_revnat_tuple {
	__u64 cookie;
	__be32 address;
	__be16 port;
	__u16 pad;
};

struct ipv4_revnat_entry {
	__be32 address;
	__be16 port;
	__u16 rev_nat_index;
};

struct bpf_elf_map __section_maps LB4_REVERSE_NAT_SK_MAP = {
	.type		= BPF_MAP_TYPE_LRU_HASH,
	.size_key	= sizeof(struct ipv4_revnat_tuple),
	.size_value	= sizeof(struct ipv4_revnat_entry),
	.pinning	= PIN_GLOBAL_NS,
	.max_elem	= 256 * 1024,
};

static __always_inline int sock4_update_revnat(struct bpf_sock_addr *ctx,
					       struct lb4_backend *backend,
					       struct lb4_key *lkey,
					       struct lb4_service *slave_svc)
{
	struct ipv4_revnat_tuple rkey = {};
	struct ipv4_revnat_entry rval = {};

	rkey.cookie = sock_local_cookie(ctx);
	rkey.address = backend->address;
	rkey.port = backend->port;

	rval.address = lkey->address;
	rval.port = lkey->dport;
	rval.rev_nat_index = slave_svc->rev_nat_index;

	return map_update_elem(&LB4_REVERSE_NAT_SK_MAP, &rkey,
			       &rval, 0);
}
#else
static __always_inline int sock4_update_revnat(struct bpf_sock_addr *ctx,
					       struct lb4_backend *backend,
					       struct lb4_key *lkey,
					       struct lb4_service *slave_svc)
{
	return -1;
}
#endif /* ENABLE_HOST_SERVICES_UDP */

static __always_inline bool sock4_skip_xlate(struct lb4_service *svc,
					     __be32 address)
{
	if (is_v4_loopback(address))
		return false;
	if (svc->local_scope || lb4_svc_is_external_ip(svc)) {
		struct remote_endpoint_info *info;

		info = ipcache_lookup4(&IPCACHE_MAP, address,
				       V4_CACHE_KEY_LEN);
		if (info == NULL ||
		     (svc->local_scope && info->sec_label != HOST_ID) ||
		    (!svc->local_scope && info->sec_label != HOST_ID &&
					  info->sec_label != REMOTE_NODE_ID))
			return true;
	}

	return false;
}

static __always_inline
struct lb4_service *sock4_nodeport_wildcard_lookup(struct lb4_key *key,
						   const bool include_remote_hosts)
{
#ifdef ENABLE_NODEPORT
	struct remote_endpoint_info *info;
	__u16 service_port;

	service_port = bpf_ntohs(key->dport);
	if (service_port < NODEPORT_PORT_MIN ||
	    service_port > NODEPORT_PORT_MAX)
		return NULL;

	/* When connecting to node port services in our cluster that
	 * have either {REMOTE_NODE,HOST}_ID or loopback address, we
	 * do a wild-card lookup with IP of 0.
	 */
	if (is_v4_loopback(key->address))
		goto wildcard_lookup;

	info = ipcache_lookup4(&IPCACHE_MAP, key->address, V4_CACHE_KEY_LEN);
	if (info != NULL && (info->sec_label == HOST_ID ||
	    (include_remote_hosts && info->sec_label == REMOTE_NODE_ID)))
		goto wildcard_lookup;

	return NULL;
wildcard_lookup:
	key->address = 0;
	return lb4_lookup_service(key);
#else
	return NULL;
#endif /* ENABLE_NODEPORT */
}

static __always_inline int __sock4_xlate(struct bpf_sock_addr *ctx,
					 struct bpf_sock_addr *ctx_full)
{
	struct lb4_backend *backend;
	struct lb4_service *svc;
	struct lb4_key key = {
		.address	= ctx->user_ip4,
		.dport		= ctx_dst_port(ctx),
	};
	struct lb4_service *slave_svc;

	if (!sock_proto_enabled(ctx->protocol))
		return -ENOTSUP;

	/* Initial non-wildcarded lookup handles regular services
	 * deployed in nodeport range, external ip and partially
	 * nodeport services. If latter fails, we try wildcarded
	 * lookup for nodeport services.
	 */
	svc = lb4_lookup_service(&key);
	if (!svc) {
		key.dport = ctx_dst_port(ctx);

		svc = sock4_nodeport_wildcard_lookup(&key, true);
		if (svc && !lb4_svc_is_nodeport(svc))
			svc = NULL;
	}
	if (!svc)
		return -ENXIO;

	/* Do not perform service translation for external IPs
	 * that are not a local address because we don't want
	 * a k8s service to easily do MITM attacks for a public
	 * IP address. But do the service translation if the IP
	 * is from the host.
	 */
	if (sock4_skip_xlate(svc, ctx->user_ip4))
		return -EPERM;

	key.slave = (sock_local_cookie(ctx_full) % svc->count) + 1;

	slave_svc = __lb4_lookup_slave(&key);
	if (!slave_svc) {
		update_metrics(0, METRIC_EGRESS, REASON_LB_NO_SLAVE);
		return -ENOENT;
	}

	backend = __lb4_lookup_backend(slave_svc->backend_id);
	if (!backend) {
		update_metrics(0, METRIC_EGRESS, REASON_LB_NO_BACKEND);
		return -ENOENT;
	}

	if (ctx->protocol != IPPROTO_TCP &&
	    sock4_update_revnat(ctx_full, backend, &key,
				slave_svc) < 0) {
		update_metrics(0, METRIC_EGRESS, REASON_LB_REVNAT_UPDATE);
		return -ENOMEM;
	}

	ctx->user_ip4	= backend->address;
	ctx_set_port(ctx, backend->port);

	return 0;
}

__section("from-sock4")
int sock4_xlate(struct bpf_sock_addr *ctx)
{
	__sock4_xlate(ctx, ctx);
	return SYS_PROCEED;
}

#if defined(ENABLE_NODEPORT) || defined(ENABLE_EXTERNAL_IP)
static __always_inline int __sock4_post_bind(struct bpf_sock *ctx)
{
	struct lb4_service *svc;
	struct lb4_key key = {
		.address	= ctx->src_ip4,
		.dport		= ctx_src_port(ctx),
	};

	if (!sock_proto_enabled(ctx->protocol))
		return 0;

	svc = lb4_lookup_service(&key);
	if (!svc) {
		/* Perform a wildcard lookup for the case where the caller tries
		 * to bind to loopback or an address with host identity
		 * (without remote hosts).
		 */
		key.dport = ctx_src_port(ctx);
		svc = sock4_nodeport_wildcard_lookup(&key, false);
	}

	/* If the sockaddr of this socket overlaps with a NodePort
	 * or ExternalIP service. We must reject this bind() call
	 * to avoid accidentally hijacking its traffic.
	 */
	if (svc && (lb4_svc_is_nodeport(svc) || lb4_svc_is_external_ip(svc)))
		return -EADDRINUSE;

	return 0;
}

__section("post-bind-sock4")
int sock4_post_bind(struct bpf_sock *ctx)
{
	if (__sock4_post_bind(ctx) < 0)
		return SYS_REJECT;

	return SYS_PROCEED;
}
#endif /* ENABLE_NODEPORT || ENABLE_EXTERNAL_IP */

#ifdef ENABLE_HOST_SERVICES_UDP
static __always_inline int __sock4_xlate_snd(struct bpf_sock_addr *ctx,
					     struct bpf_sock_addr *ctx_full)
{
	struct lb4_key lkey = {
		.address	= ctx->user_ip4,
		.dport		= ctx_dst_port(ctx),
	};
	struct lb4_backend *backend;
	struct lb4_service *svc;
	struct lb4_service *slave_svc;

	svc = lb4_lookup_service(&lkey);
	if (!svc) {
		lkey.dport = ctx_dst_port(ctx);
		svc = sock4_nodeport_wildcard_lookup(&lkey, true);
		if (svc && !lb4_svc_is_nodeport(svc))
			svc = NULL;
	}
	if (!svc)
		return -ENXIO;

	if (sock4_skip_xlate(svc, ctx->user_ip4))
		return -EPERM;

	lkey.slave = (sock_local_cookie(ctx_full) % svc->count) + 1;

	slave_svc = __lb4_lookup_slave(&lkey);
	if (!slave_svc) {
		update_metrics(0, METRIC_EGRESS, REASON_LB_NO_SLAVE);
		return -ENOENT;
	}

	backend = __lb4_lookup_backend(slave_svc->backend_id);
	if (!backend) {
		update_metrics(0, METRIC_EGRESS, REASON_LB_NO_BACKEND);
		return -ENOENT;
	}

	if (sock4_update_revnat(ctx_full, backend, &lkey,
				slave_svc) < 0) {
		update_metrics(0, METRIC_EGRESS, REASON_LB_REVNAT_UPDATE);
		return -ENOMEM;
	}

	ctx->user_ip4 = backend->address;
	ctx_set_port(ctx, backend->port);

	return 0;
}

__section("snd-sock4")
int sock4_xlate_snd(struct bpf_sock_addr *ctx)
{
	__sock4_xlate_snd(ctx, ctx);
	return SYS_PROCEED;
}

static __always_inline int __sock4_xlate_rcv(struct bpf_sock_addr *ctx,
					     struct bpf_sock_addr *ctx_full)
{
	struct ipv4_revnat_entry *rval;
	struct ipv4_revnat_tuple rkey = {
		.cookie		= sock_local_cookie(ctx_full),
		.address	= ctx->user_ip4,
		.port		= ctx_dst_port(ctx),
	};

	rval = map_lookup_elem(&LB4_REVERSE_NAT_SK_MAP, &rkey);
	if (rval) {
		struct lb4_service *svc;
		struct lb4_key lkey = {
			.address	= rval->address,
			.dport		= rval->port,
		};

		svc = lb4_lookup_service(&lkey);
		if (!svc || svc->rev_nat_index != rval->rev_nat_index) {
			map_delete_elem(&LB4_REVERSE_NAT_SK_MAP, &rkey);
			update_metrics(0, METRIC_INGRESS, REASON_LB_REVNAT_STALE);
			return -ENOENT;
		}

		ctx->user_ip4 = rval->address;
		ctx_set_port(ctx, rval->port);
		return 0;
	}

	return -ENXIO;
}

__section("rcv-sock4")
int sock4_xlate_rcv(struct bpf_sock_addr *ctx)
{
	__sock4_xlate_rcv(ctx, ctx);
	return SYS_PROCEED;
}
#endif /* ENABLE_HOST_SERVICES_UDP */
#endif /* ENABLE_IPV4 */

#if defined(ENABLE_IPV6) || defined(ENABLE_IPV4)
#ifdef ENABLE_HOST_SERVICES_UDP
struct ipv6_revnat_tuple {
	__u64 cookie;
	union v6addr address;
	__be16 port;
	__u16 pad;
};

struct ipv6_revnat_entry {
	union v6addr address;
	__be16 port;
	__u16 rev_nat_index;
};

struct bpf_elf_map __section_maps LB6_REVERSE_NAT_SK_MAP = {
	.type		= BPF_MAP_TYPE_LRU_HASH,
	.size_key	= sizeof(struct ipv6_revnat_tuple),
	.size_value	= sizeof(struct ipv6_revnat_entry),
	.pinning	= PIN_GLOBAL_NS,
	.max_elem	= 256 * 1024,
};

static __always_inline int sock6_update_revnat(struct bpf_sock_addr *ctx,
					       struct lb6_backend *backend,
					       struct lb6_key *lkey,
					       struct lb6_service *slave_svc)
{
	struct ipv6_revnat_tuple rkey = {};
	struct ipv6_revnat_entry rval = {};

	rkey.cookie = sock_local_cookie(ctx);
	rkey.address = backend->address;
	rkey.port = backend->port;

	rval.address = lkey->address;
	rval.port = lkey->dport;
	rval.rev_nat_index = slave_svc->rev_nat_index;

	return map_update_elem(&LB6_REVERSE_NAT_SK_MAP, &rkey,
			       &rval, 0);
}
#else
static __always_inline int sock6_update_revnat(struct bpf_sock_addr *ctx,
					       struct lb6_backend *backend,
					       struct lb6_key *lkey,
					       struct lb6_service *slave_svc)
{
	return -1;
}
#endif /* ENABLE_HOST_SERVICES_UDP */

static __always_inline void ctx_get_v6_address(struct bpf_sock_addr *ctx,
					       union v6addr *addr)
{
	addr->p1 = ctx->user_ip6[0];
	addr->p2 = ctx->user_ip6[1];
	addr->p3 = ctx->user_ip6[2];
	addr->p4 = ctx->user_ip6[3];
}

#ifdef ENABLE_NODEPORT
static __always_inline void ctx_get_v6_src_address(struct bpf_sock *ctx,
					       union v6addr *addr)
{
	addr->p1 = ctx->src_ip6[0];
	addr->p2 = ctx->src_ip6[1];
	addr->p3 = ctx->src_ip6[2];
	addr->p4 = ctx->src_ip6[3];
}
#endif /* ENABLE_NODEPORT */

static __always_inline void ctx_set_v6_address(struct bpf_sock_addr *ctx,
					       union v6addr *addr)
{
	ctx->user_ip6[0] = addr->p1;
	ctx->user_ip6[1] = addr->p2;
	ctx->user_ip6[2] = addr->p3;
	ctx->user_ip6[3] = addr->p4;
}

static __always_inline bool sock6_skip_xlate(struct lb6_service *svc,
					     union v6addr *address)
{
	if (is_v6_loopback(address))
		return false;
	if (svc->local_scope || lb6_svc_is_external_ip(svc)) {
		struct remote_endpoint_info *info;

		info = ipcache_lookup6(&IPCACHE_MAP, address,
				       V6_CACHE_KEY_LEN);
		if (info == NULL ||
		     (svc->local_scope && info->sec_label != HOST_ID) ||
		    (!svc->local_scope && info->sec_label != HOST_ID &&
					  info->sec_label != REMOTE_NODE_ID))
			return true;
	}

	return false;
}

static __always_inline
struct lb6_service *sock6_nodeport_wildcard_lookup(struct lb6_key *key,
						   bool include_remote_hosts)
{
#ifdef ENABLE_NODEPORT
	struct remote_endpoint_info *info;
	__u16 service_port;

	service_port = bpf_ntohs(key->dport);
	if (service_port < NODEPORT_PORT_MIN ||
	    service_port > NODEPORT_PORT_MAX)
		return NULL;

	/* When connecting to node port services in our cluster that
	 * have either {REMOTE_NODE,HOST}_ID or loopback address, we
	 * do a wild-card lookup with IP of 0.
	 */
	if (is_v6_loopback(&key->address))
		goto wildcard_lookup;

	info = ipcache_lookup6(&IPCACHE_MAP, &key->address, V6_CACHE_KEY_LEN);
	if (info != NULL && (info->sec_label == HOST_ID ||
	    (include_remote_hosts && info->sec_label == REMOTE_NODE_ID)))
		goto wildcard_lookup;

	return NULL;
wildcard_lookup:
	__builtin_memset(&key->address, 0, sizeof(key->address));
	return lb6_lookup_service(key);
#else
	return NULL;
#endif /* ENABLE_NODEPORT */
}

static __always_inline int sock6_xlate_v4_in_v6(struct bpf_sock_addr *ctx)
{
#ifdef ENABLE_IPV4
	struct bpf_sock_addr fake_ctx;
	union v6addr addr6;
	int ret;

	ctx_get_v6_address(ctx, &addr6);
	if (!is_v4_in_v6(&addr6))
		return -ENXIO;

	__builtin_memset(&fake_ctx, 0, sizeof(fake_ctx));
	fake_ctx.protocol  = ctx->protocol;
	fake_ctx.user_ip4  = addr6.p4;
	fake_ctx.user_port = ctx_dst_port(ctx);

	ret = __sock4_xlate(&fake_ctx, ctx);
	if (ret < 0)
		return ret;

	build_v4_in_v6(&addr6, fake_ctx.user_ip4);
	ctx_set_v6_address(ctx, &addr6);
	ctx_set_port(ctx, fake_ctx.user_port);

	return 0;
#endif /* ENABLE_IPV4 */
	return -ENXIO;
}

#if defined(ENABLE_NODEPORT) || defined(ENABLE_EXTERNAL_IP)
static __always_inline int sock6_post_bind_v4_in_v6(struct bpf_sock *ctx)
{
#ifdef ENABLE_IPV4
	struct bpf_sock fake_ctx;
	union v6addr addr6;

	ctx_get_v6_src_address(ctx, &addr6);
	if (!is_v4_in_v6(&addr6))
		return 0;

	__builtin_memset(&fake_ctx, 0, sizeof(fake_ctx));
	fake_ctx.protocol = ctx->protocol;
	fake_ctx.src_ip4  = addr6.p4;
	fake_ctx.src_port = ctx->src_port;

	return __sock4_post_bind(&fake_ctx);
#endif /* ENABLE_IPV4 */
	return 0;
}

static __always_inline int __sock6_post_bind(struct bpf_sock *ctx)
{
	struct lb6_service *svc;
	struct lb6_key key = {
		.dport		= ctx_src_port(ctx),
	};

	if (!sock_proto_enabled(ctx->protocol))
		return 0;

	ctx_get_v6_src_address(ctx, &key.address);

	svc = lb6_lookup_service(&key);
	if (!svc) {
		key.dport = ctx_src_port(ctx);
		svc = sock6_nodeport_wildcard_lookup(&key, false);
		if (!svc)
			return sock6_post_bind_v4_in_v6(ctx);
	}

	if (svc && (lb6_svc_is_nodeport(svc) || lb6_svc_is_external_ip(svc)))
		return -EADDRINUSE;

	return 0;
}

__section("post-bind-sock6")
int sock6_post_bind(struct bpf_sock *ctx)
{
	if (__sock6_post_bind(ctx) < 0)
		return SYS_REJECT;

	return SYS_PROCEED;
}
#endif /* ENABLE_NODEPORT || ENABLE_EXTERNAL_IP */

static __always_inline int __sock6_xlate(struct bpf_sock_addr *ctx)
{
	struct lb6_backend *backend;
	struct lb6_service *svc;
	struct lb6_key key = {
		.dport		= ctx_dst_port(ctx),
	};
	struct lb6_service *slave_svc;
	union v6addr v6_orig;

	if (!sock_proto_enabled(ctx->protocol))
		return -ENOTSUP;

	ctx_get_v6_address(ctx, &key.address);
	v6_orig = key.address;

	svc = lb6_lookup_service(&key);
	if (!svc) {
		key.dport = ctx_dst_port(ctx);

		svc = sock6_nodeport_wildcard_lookup(&key, true);
		if (svc && !lb6_svc_is_nodeport(svc))
			svc = NULL;
		else if (!svc)
			return sock6_xlate_v4_in_v6(ctx);
	}
	if (!svc)
		return -ENXIO;

	if (sock6_skip_xlate(svc, &v6_orig))
		return -EPERM;

	key.slave = (sock_local_cookie(ctx) % svc->count) + 1;

	slave_svc = __lb6_lookup_slave(&key);
	if (!slave_svc) {
		update_metrics(0, METRIC_EGRESS, REASON_LB_NO_SLAVE);
		return -ENOENT;
	}

	backend = __lb6_lookup_backend(slave_svc->backend_id);
	if (!backend) {
		update_metrics(0, METRIC_EGRESS, REASON_LB_NO_BACKEND);
		return -ENOENT;
	}

	if (ctx->protocol != IPPROTO_TCP &&
	    sock6_update_revnat(ctx, backend, &key,
			        slave_svc) < 0) {
		update_metrics(0, METRIC_EGRESS, REASON_LB_REVNAT_UPDATE);
		return -ENOMEM;
	}

	ctx_set_v6_address(ctx, &backend->address);
	ctx_set_port(ctx, backend->port);

	return 0;
}

__section("from-sock6")
int sock6_xlate(struct bpf_sock_addr *ctx)
{
	__sock6_xlate(ctx);
	return SYS_PROCEED;
}

#ifdef ENABLE_HOST_SERVICES_UDP
static __always_inline int sock6_xlate_snd_v4_in_v6(struct bpf_sock_addr *ctx)
{
#ifdef ENABLE_IPV4
	struct bpf_sock_addr fake_ctx;
	union v6addr addr6;
	int ret;

	ctx_get_v6_address(ctx, &addr6);
	if (!is_v4_in_v6(&addr6))
		return -ENXIO;

	__builtin_memset(&fake_ctx, 0, sizeof(fake_ctx));
	fake_ctx.protocol  = ctx->protocol;
	fake_ctx.user_ip4  = addr6.p4;
	fake_ctx.user_port = ctx_dst_port(ctx);

	ret = __sock4_xlate_snd(&fake_ctx, ctx);
	if (ret < 0)
		return ret;

	build_v4_in_v6(&addr6, fake_ctx.user_ip4);
	ctx_set_v6_address(ctx, &addr6);
	ctx_set_port(ctx, fake_ctx.user_port);

	return 0;
#endif /* ENABLE_IPV4 */
	return -ENXIO;
}

static __always_inline int __sock6_xlate_snd(struct bpf_sock_addr *ctx)
{
	struct lb6_backend *backend;
	struct lb6_service *svc;
	struct lb6_key lkey = {
		.dport		= ctx_dst_port(ctx),
	};
	struct lb6_service *slave_svc;
	union v6addr v6_orig;

	ctx_get_v6_address(ctx, &lkey.address);
	v6_orig = lkey.address;

	svc = lb6_lookup_service(&lkey);
	if (!svc) {
		lkey.dport = ctx_dst_port(ctx);

		svc = sock6_nodeport_wildcard_lookup(&lkey, true);
		if (svc && !lb6_svc_is_nodeport(svc))
			svc = NULL;
		else if (!svc)
			return sock6_xlate_snd_v4_in_v6(ctx);
	}
	if (!svc)
		return -ENXIO;

	if (sock6_skip_xlate(svc, &v6_orig))
		return -EPERM;

	lkey.slave = (sock_local_cookie(ctx) % svc->count) + 1;

	slave_svc = __lb6_lookup_slave(&lkey);
	if (!slave_svc) {
		update_metrics(0, METRIC_EGRESS, REASON_LB_NO_SLAVE);
		return -ENOENT;
	}

	backend = __lb6_lookup_backend(slave_svc->backend_id);
	if (!backend) {
		update_metrics(0, METRIC_EGRESS, REASON_LB_NO_BACKEND);
		return -ENOENT;
	}

	if (sock6_update_revnat(ctx, backend, &lkey,
			        slave_svc) < 0) {
		update_metrics(0, METRIC_EGRESS, REASON_LB_REVNAT_UPDATE);
		return -ENOMEM;
	}

	ctx_set_v6_address(ctx, &backend->address);
	ctx_set_port(ctx, backend->port);

	return 0;
}

__section("snd-sock6")
static __always_inline int sock6_xlate_snd(struct bpf_sock_addr *ctx)
{
	__sock6_xlate_snd(ctx);
	return SYS_PROCEED;
}

static __always_inline int sock6_xlate_rcv_v4_in_v6(struct bpf_sock_addr *ctx)
{
#ifdef ENABLE_IPV4
	struct bpf_sock_addr fake_ctx;
	union v6addr addr6;
	int ret;

	ctx_get_v6_address(ctx, &addr6);
	if (!is_v4_in_v6(&addr6))
		return -ENXIO;

	__builtin_memset(&fake_ctx, 0, sizeof(fake_ctx));
	fake_ctx.protocol  = ctx->protocol;
	fake_ctx.user_ip4  = addr6.p4;
	fake_ctx.user_port = ctx_dst_port(ctx);

	ret = __sock4_xlate_rcv(&fake_ctx, ctx);
	if (ret < 0)
		return ret;

	build_v4_in_v6(&addr6, fake_ctx.user_ip4);
	ctx_set_v6_address(ctx, &addr6);
	ctx_set_port(ctx, fake_ctx.user_port);

	return 0;
#endif /* ENABLE_IPV4 */
	return -ENXIO;
}

static __always_inline int __sock6_xlate_rcv(struct bpf_sock_addr *ctx)
{
	struct ipv6_revnat_tuple rkey = {};
	struct ipv6_revnat_entry *rval;

	rkey.cookie = sock_local_cookie(ctx);
	rkey.port = ctx_dst_port(ctx);
	ctx_get_v6_address(ctx, &rkey.address);

	rval = map_lookup_elem(&LB6_REVERSE_NAT_SK_MAP, &rkey);
	if (rval) {
		struct lb6_service *svc;
		struct lb6_key lkey = {
			.address	= rval->address,
			.dport		= rval->port,
		};

		svc = lb6_lookup_service(&lkey);
		if (!svc || svc->rev_nat_index != rval->rev_nat_index) {
			map_delete_elem(&LB6_REVERSE_NAT_SK_MAP, &rkey);
			update_metrics(0, METRIC_INGRESS, REASON_LB_REVNAT_STALE);
			return -ENOENT;
		}

		ctx_set_v6_address(ctx, &rval->address);
		ctx_set_port(ctx, rval->port);
		return 0;
	}

	return sock6_xlate_rcv_v4_in_v6(ctx);
}

__section("rcv-sock6")
int sock6_xlate_rcv(struct bpf_sock_addr *ctx)
{
	__sock6_xlate_rcv(ctx);
	return SYS_PROCEED;
}
#endif /* ENABLE_HOST_SERVICES_UDP */
#endif /* ENABLE_IPV6 || ENABLE_IPV4 */

BPF_LICENSE("GPL");