// SPDX-License-Identifier: GPL-2.0
/* Copyright (C) 2016-2020 Authors of Cilium */

#include <bpf/ctx/skb.h>
#include <bpf/api.h>

#include <node_config.h>
#include <ep_config.h>

#define IS_BPF_HOST 1

#define EVENT_SOURCE HOST_EP_ID

/* Host endpoint ID for the template bpf_host object file. Will be replaced
 * at compile-time with the proper host endpoint ID.
 */
#define TEMPLATE_HOST_EP_ID 0xffff

/* These are configuration options which have a default value in their
 * respective header files and must thus be defined beforehand:
 */
/* Pass unknown ICMPv6 NS to stack */
#define ACTION_UNKNOWN_ICMP6_NS CTX_ACT_OK

/* Include policy_can_access_ingress() */
#define REQUIRES_CAN_ACCESS

/* CB_PROXY_MAGIC overlaps with CB_ENCRYPT_MAGIC */
#define ENCRYPT_OR_PROXY_MAGIC 0

#ifdef POD_ENDPOINT
# undef ENABLE_HOST_FIREWALL
#endif

/* Controls the inclusion of the CILIUM_CALL_SEND_ICMP6_ECHO_REPLY section in
 * the bpf_lxc object file.
 */
#define SKIP_ICMPV6_ECHO_HANDLING

#include "lib/common.h"
#include "lib/edt.h"
#include "lib/arp.h"
#include "lib/maps.h"
#include "lib/ipv6.h"
#include "lib/ipv4.h"
#include "lib/icmp6.h"
#include "lib/eth.h"
#include "lib/dbg.h"
#include "lib/proxy.h"
#include "lib/trace.h"
#include "lib/identity.h"
#include "lib/l3.h"
#include "lib/l4.h"
#include "lib/drop.h"
#include "lib/encap.h"
#include "lib/nat.h"
#include "lib/lb.h"
#include "lib/nodeport.h"
#include "lib/eps.h"
#include "lib/host_firewall.h"
#include "lib/overloadable.h"
#include "lib/encrypt.h"

#if defined(ENABLE_IPV4) || defined(ENABLE_IPV6)
static __always_inline int rewrite_dmac_to_host(struct __ctx_buff *ctx,
						__u32 src_identity)
{
	/* When attached to cilium_host, we rewrite the DMAC to the mac of
	 * cilium_host (peer) to ensure the packet is being considered to be
	 * addressed to the host (PACKET_HOST).
	 */
	union macaddr cilium_net_mac = CILIUM_NET_MAC;

	/* Rewrite to destination MAC of cilium_net (remote peer) */
	if (eth_store_daddr(ctx, (__u8 *) &cilium_net_mac.addr, 0) < 0)
		return send_drop_notify_error(ctx, src_identity, DROP_WRITE_ERROR,
					      CTX_ACT_OK, METRIC_INGRESS);

	return CTX_ACT_OK;
}

#define SECCTX_FROM_IPCACHE_OK	2
#ifndef SECCTX_FROM_IPCACHE
# define SECCTX_FROM_IPCACHE	0
#endif

static __always_inline bool identity_from_ipcache_ok(void)
{
	return SECCTX_FROM_IPCACHE == SECCTX_FROM_IPCACHE_OK;
}
#endif

#ifdef ENABLE_IPV6
static __always_inline __u32
derive_src_id(const union v6addr *node_ip, struct ipv6hdr *ip6, __u32 *identity)
{
	if (ipv6_match_prefix_64((union v6addr *) &ip6->saddr, node_ip)) {
		/* Read initial 4 bytes of header and then extract flowlabel */
		__u32 *tmp = (__u32 *) ip6;
		*identity = bpf_ntohl(*tmp & IPV6_FLOWLABEL_MASK);

		/* A remote node will map any HOST_ID source to be presented as
		 * REMOTE_NODE_ID, therefore any attempt to signal HOST_ID as
		 * source from a remote node can be dropped.
		 */
		if (*identity == HOST_ID)
			return DROP_INVALID_IDENTITY;
	}
	return 0;
}

# ifdef ENABLE_HOST_FIREWALL
static __always_inline __u32
ipcache_lookup_srcid6(struct __ctx_buff *ctx)
{
	struct remote_endpoint_info *info = NULL;
	void *data, *data_end;
	struct ipv6hdr *ip6;
	__u32 srcid = 0;

	if (!revalidate_data(ctx, &data, &data_end, &ip6))
		return DROP_INVALID;

	info = lookup_ip6_remote_endpoint((union v6addr *) &ip6->saddr);
	if (info != NULL)
		srcid = info->sec_label;
	cilium_dbg(ctx, info ? DBG_IP_ID_MAP_SUCCEED6 : DBG_IP_ID_MAP_FAILED6,
		   ip6->saddr.s6_addr32[3], srcid);

	return srcid;
}
# endif /* ENABLE_HOST_FIREWALL */

static __always_inline __u32
resolve_srcid_ipv6(struct __ctx_buff *ctx, __u32 srcid_from_proxy,
		   const bool from_host)
{
	__u32 src_id = WORLD_ID, srcid_from_ipcache = srcid_from_proxy;
	struct remote_endpoint_info *info = NULL;
	void *data, *data_end;
	struct ipv6hdr *ip6;
	union v6addr *src;
	int ret;

	if (!revalidate_data_maybe_pull(ctx, &data, &data_end, &ip6, !from_host))
		return DROP_INVALID;

	if (!from_host) {
		union v6addr node_ip = {};

		BPF_V6(node_ip, ROUTER_IP);
		ret = derive_src_id(&node_ip, ip6, &src_id);
		if (IS_ERR(ret))
			return ret;
	}

	/* Packets from the proxy will already have a real identity. */
	if (identity_is_reserved(srcid_from_ipcache)) {
		src = (union v6addr *) &ip6->saddr;
		info = lookup_ip6_remote_endpoint(src);
		if (info != NULL && info->sec_label)
			srcid_from_ipcache = info->sec_label;
		cilium_dbg(ctx, info ? DBG_IP_ID_MAP_SUCCEED6 : DBG_IP_ID_MAP_FAILED6,
			   ((__u32 *) src)[3], srcid_from_ipcache);
	}

	if (from_host)
		src_id = srcid_from_ipcache;
	else if (src_id == WORLD_ID &&
		 identity_from_ipcache_ok() &&
		 !identity_is_reserved(srcid_from_ipcache))
		src_id = srcid_from_ipcache;
	return src_id;
}

static __always_inline int
handle_ipv6(struct __ctx_buff *ctx, __u32 secctx, const bool from_host)
{
	struct remote_endpoint_info *info = NULL;
	void *data, *data_end;
	struct ipv6hdr *ip6;
	union v6addr *dst;
	__u32 __maybe_unused remote_id = WORLD_ID;
	int ret, l3_off = ETH_HLEN, hdrlen;
	bool skip_redirect = false;
	struct endpoint_info *ep;
	__u8 nexthdr;

	if (!revalidate_data(ctx, &data, &data_end, &ip6))
		return DROP_INVALID;

	nexthdr = ip6->nexthdr;
	hdrlen = ipv6_hdrlen(ctx, ETH_HLEN, &nexthdr);
	if (hdrlen < 0)
		return hdrlen;

	if (likely(nexthdr == IPPROTO_ICMPV6)) {
		ret = icmp6_host_handle(ctx);
		if (ret == SKIP_HOST_FIREWALL)
			goto skip_host_firewall;
		if (IS_ERR(ret))
			return ret;
	}

#ifdef ENABLE_NODEPORT
	if (!from_host) {
		if (ctx_get_xfer(ctx) != XFER_PKT_NO_SVC &&
		    !bpf_skip_nodeport(ctx)) {
			ret = nodeport_lb6(ctx, secctx);
			if (ret < 0)
				return ret;
		}
#if defined(NO_REDIRECT) && !defined(ENABLE_REDIRECT_FAST)
		/* See IPv4 case for NO_REDIRECT/ENABLE_REDIRECT_FAST comments */
		skip_redirect = true;
#endif /* NO_REDIRECT && !ENABLE_REDIRECT_FAST */
		/* Verifier workaround: modified ctx access. */
		if (!revalidate_data(ctx, &data, &data_end, &ip6))
			return DROP_INVALID;
	}
#endif /* ENABLE_NODEPORT */

#ifdef ENABLE_HOST_FIREWALL
	if (from_host) {
		ret = ipv6_host_policy_egress(ctx, secctx);
		if (IS_ERR(ret))
			return ret;
	} else if (!ctx_skip_host_fw(ctx)) {
		ret = ipv6_host_policy_ingress(ctx, &remote_id);
		if (IS_ERR(ret))
			return ret;
	}
#endif /* ENABLE_HOST_FIREWALL */

	if (skip_redirect)
		return CTX_ACT_OK;

skip_host_firewall:
	if (from_host) {
		/* If we are attached to cilium_host at egress, this will
		 * rewrite the destination MAC address to the MAC of cilium_net.
		 */
		ret = rewrite_dmac_to_host(ctx, secctx);
		/* DIRECT PACKET READ INVALID */
		if (IS_ERR(ret))
			return ret;

		if (!revalidate_data(ctx, &data, &data_end, &ip6))
			return DROP_INVALID;
	}

	/* Lookup IPv4 address in list of local endpoints */
	ep = lookup_ip6_endpoint(ip6);
	if (ep) {
		/* Let through packets to the node-ip so they are
		 * processed by the local ip stack.
		 */
		if (ep->flags & ENDPOINT_F_HOST)
			return CTX_ACT_OK;

		return ipv6_local_delivery(ctx, l3_off, secctx, ep,
					   METRIC_INGRESS, from_host);
	}

	/* Below remainder is only relevant when traffic is pushed via cilium_host.
	 * For traffic coming from external, we're done here.
	 */
	if (!from_host)
		return CTX_ACT_OK;

#ifdef ENCAP_IFINDEX
	dst = (union v6addr *) &ip6->daddr;
	info = ipcache_lookup6(&IPCACHE_MAP, dst, V6_CACHE_KEY_LEN);
	if (info != NULL && info->tunnel_endpoint != 0) {
		ret = encap_and_redirect_with_nodeid(ctx, info->tunnel_endpoint,
							 info->key,
							 secctx, TRACE_PAYLOAD_LEN);

		/* If IPSEC is needed recirc through ingress to use xfrm stack
		 * and then result will routed back through bpf_netdev on egress
		 * but with encrypt marks.
		 */
		if (ret == IPSEC_ENDPOINT)
			return CTX_ACT_OK;
		else
			return ret;
	} else {
		struct endpoint_key key = {};

		/* IPv6 lookup key: daddr/96 */
		dst = (union v6addr *) &ip6->daddr;
		key.ip6.p1 = dst->p1;
		key.ip6.p2 = dst->p2;
		key.ip6.p3 = dst->p3;
		key.ip6.p4 = 0;
		key.family = ENDPOINT_KEY_IPV6;

		ret = encap_and_redirect_netdev(ctx, &key, secctx, TRACE_PAYLOAD_LEN);
		if (ret == IPSEC_ENDPOINT)
			return CTX_ACT_OK;
		else if (ret != DROP_NO_TUNNEL_ENDPOINT)
			return ret;
	}
#endif

	dst = (union v6addr *) &ip6->daddr;
	info = ipcache_lookup6(&IPCACHE_MAP, dst, V6_CACHE_KEY_LEN);
	if (info == NULL || info->sec_label == WORLD_ID) {
		/* See IPv4 comment. */
		return DROP_UNROUTABLE;
	}

#ifdef ENABLE_IPSEC
	if (info && info->key && info->tunnel_endpoint) {
		__u8 key = get_min_encrypt_key(info->key);

		set_encrypt_key_meta(ctx, key);
#ifdef IP_POOLS
		set_encrypt_dip(ctx, info->tunnel_endpoint);
#else
		set_identity_meta(ctx, secctx);
#endif
	}
#endif
	return CTX_ACT_OK;
}

static __always_inline int
tail_handle_ipv6(struct __ctx_buff *ctx, const bool from_host)
{
	__u32 proxy_identity = ctx_load_meta(ctx, CB_SRC_IDENTITY);
	int ret;

	ctx_store_meta(ctx, CB_SRC_IDENTITY, 0);

	ret = handle_ipv6(ctx, proxy_identity, from_host);
	if (IS_ERR(ret))
		return send_drop_notify_error(ctx, proxy_identity, ret,
					      CTX_ACT_DROP, METRIC_INGRESS);
	return ret;
}

__section_tail(CILIUM_MAP_CALLS, CILIUM_CALL_IPV6_FROM_HOST)
int tail_handle_ipv6_from_host(struct __ctx_buff *ctx __maybe_unused)
{
	return tail_handle_ipv6(ctx, true);
}

__section_tail(CILIUM_MAP_CALLS, CILIUM_CALL_IPV6_FROM_LXC)
int tail_handle_ipv6_from_netdev(struct __ctx_buff *ctx)
{
	return tail_handle_ipv6(ctx, false);
}

# ifdef ENABLE_HOST_FIREWALL
static __always_inline int
handle_to_netdev_ipv6(struct __ctx_buff *ctx)
{
	void *data, *data_end;
	struct ipv6hdr *ip6;
	int hdrlen, ret;
	__u32 srcID = 0;
	__u8 nexthdr;

	if (!revalidate_data_pull(ctx, &data, &data_end, &ip6))
		return DROP_INVALID;

	nexthdr = ip6->nexthdr;
	hdrlen = ipv6_hdrlen(ctx, ETH_HLEN, &nexthdr);
	if (hdrlen < 0)
		return hdrlen;

	if (likely(nexthdr == IPPROTO_ICMPV6)) {
		ret = icmp6_host_handle(ctx);
		if (ret == SKIP_HOST_FIREWALL)
			return CTX_ACT_OK;
		if (IS_ERR(ret))
			return ret;
	}

	/* to-netdev is attached to the egress path of the native device. */
	srcID = ipcache_lookup_srcid6(ctx);
	return ipv6_host_policy_egress(ctx, srcID);
}
# endif
#endif /* ENABLE_IPV6 */

#ifdef ENABLE_IPV4
static __always_inline __u32
resolve_srcid_ipv4(struct __ctx_buff *ctx, __u32 srcid_from_proxy,
		   __u32 *sec_label, const bool from_host)
{
	__u32 src_id = WORLD_ID, srcid_from_ipcache = srcid_from_proxy;
	struct remote_endpoint_info *info = NULL;
	void *data, *data_end;
	struct iphdr *ip4;

	/* This is the first time revalidate_data() is going to be called in
	 * the "to-netdev" path. Make sure that we don't legitimately drop
	 * the packet if the skb arrived with the header not being not in the
	 * linear data.
	 */
	if (!revalidate_data_maybe_pull(ctx, &data, &data_end, &ip4, !from_host))
		return DROP_INVALID;

	/* Packets from the proxy will already have a real identity. */
	if (identity_is_reserved(srcid_from_ipcache)) {
		info = lookup_ip4_remote_endpoint(ip4->saddr);
		if (info != NULL) {
			*sec_label = info->sec_label;

			if (*sec_label) {
				/* When SNAT is enabled on traffic ingressing
				 * into Cilium, all traffic from the world will
				 * have a source IP of the host. It will only
				 * actually be from the host if "srcid_from_proxy"
				 * (passed into this function) reports the src as
				 * the host. So we can ignore the ipcache if it
				 * reports the source as HOST_ID.
				 */
#ifndef ENABLE_EXTRA_HOST_DEV
				if (*sec_label != HOST_ID)
					srcid_from_ipcache = *sec_label;
#else
				if ((*sec_label != HOST_ID &&
				     !from_host) || from_host)
					srcid_from_ipcache = *sec_label;
#endif /* ENABLE_EXTRA_HOST_DEV */
			}
		}
		cilium_dbg(ctx, info ? DBG_IP_ID_MAP_SUCCEED4 : DBG_IP_ID_MAP_FAILED4,
			   ip4->saddr, srcid_from_ipcache);
	}

	if (from_host)
		src_id = srcid_from_ipcache;
	/* If we could not derive the secctx from the packet itself but
	 * from the ipcache instead, then use the ipcache identity.
	 */
	else if (identity_from_ipcache_ok() &&
		 !identity_is_reserved(srcid_from_ipcache))
		src_id = srcid_from_ipcache;
	return src_id;
}

static __always_inline int
handle_ipv4(struct __ctx_buff *ctx, __u32 secctx,
	    __u32 ipcache_srcid __maybe_unused, const bool from_host)
{
	struct remote_endpoint_info *info = NULL;
	__u32 __maybe_unused remoteID = 0;
	struct ipv4_ct_tuple tuple = {};
	bool skip_redirect = false;
	struct endpoint_info *ep;
	void *data, *data_end;
	struct iphdr *ip4;
	int ret;

	if (!revalidate_data(ctx, &data, &data_end, &ip4))
		return DROP_INVALID;

/* If IPv4 fragmentation is disabled
 * AND a IPv4 fragmented packet is received,
 * then drop the packet.
 */
#ifndef ENABLE_IPV4_FRAGMENTS
	if (ipv4_is_fragment(ip4))
		return DROP_FRAG_NOSUPPORT;
#endif

#ifdef ENABLE_NODEPORT
	if (!from_host) {
		if (ctx_get_xfer(ctx) != XFER_PKT_NO_SVC &&
		    !bpf_skip_nodeport(ctx)) {
			ret = nodeport_lb4(ctx, secctx);
			if (ret < 0)
				return ret;
		}
#if defined(NO_REDIRECT) && !defined(ENABLE_REDIRECT_FAST)
		/* Without bpf_redirect_neigh() helper, we cannot redirect a
		 * packet to a local endpoint in the direct routing mode, as
		 * the redirect bypasses nf_conntrack table. This makes a
		 * second reply from the endpoint to be MASQUERADEd or to be
		 * DROP-ed by k8s's "--ctstate INVALID -j DROP" depending via
		 * which interface it was inputed. With bpf_redirect_neigh()
		 * we bypass request and reply path in the host namespace and
		 * do not run into this issue.
		 */
		skip_redirect = true;
#endif /* NO_REDIRECT && !ENABLE_REDIRECT_FAST */
		/* Verifier workaround: modified ctx access. */
		if (!revalidate_data(ctx, &data, &data_end, &ip4))
			return DROP_INVALID;
	}
#endif /* ENABLE_NODEPORT */

#ifdef ENABLE_HOST_FIREWALL
	if (from_host) {
		/* We're on the egress path of cilium_host. */
		ret = ipv4_host_policy_egress(ctx, secctx, ipcache_srcid);
		if (IS_ERR(ret))
			return ret;
	} else if (!ctx_skip_host_fw(ctx)) {
		/* We're on the ingress path of the native device. */
		ret = ipv4_host_policy_ingress(ctx, &remoteID);
		if (IS_ERR(ret))
			return ret;
	}
#endif /* ENABLE_HOST_FIREWALL */

	if (skip_redirect)
		return CTX_ACT_OK;

	tuple.nexthdr = ip4->protocol;

	if (from_host) {
		/* If we are attached to cilium_host at egress, this will
		 * rewrite the destination MAC address to the MAC of cilium_net.
		 */
		ret = rewrite_dmac_to_host(ctx, secctx);
		/* DIRECT PACKET READ INVALID */
		if (IS_ERR(ret))
			return ret;

		if (!revalidate_data(ctx, &data, &data_end, &ip4))
			return DROP_INVALID;
	}

	/* Lookup IPv4 address in list of local endpoints and host IPs */
	ep = lookup_ip4_endpoint(ip4);
	if (ep) {
		/* Let through packets to the node-ip so they are processed by
		 * the local ip stack.
		 */
		if (ep->flags & ENDPOINT_F_HOST)
			return CTX_ACT_OK;

		return ipv4_local_delivery(ctx, ETH_HLEN, secctx, ip4, ep,
					   METRIC_INGRESS, from_host);
	}

	/* Below remainder is only relevant when traffic is pushed via cilium_host.
	 * For traffic coming from external, we're done here.
	 */
	if (!from_host)
		return CTX_ACT_OK;

#ifdef ENCAP_IFINDEX
	info = ipcache_lookup4(&IPCACHE_MAP, ip4->daddr, V4_CACHE_KEY_LEN);
	if (info != NULL && info->tunnel_endpoint != 0) {
		ret = encap_and_redirect_with_nodeid(ctx, info->tunnel_endpoint,
						     info->key, secctx,
						     TRACE_PAYLOAD_LEN);

		if (ret == IPSEC_ENDPOINT)
			return CTX_ACT_OK;
		else
			return ret;
	} else {
		/* IPv4 lookup key: daddr & IPV4_MASK */
		struct endpoint_key key = {};

		key.ip4 = ip4->daddr & IPV4_MASK;
		key.family = ENDPOINT_KEY_IPV4;

		cilium_dbg(ctx, DBG_NETDEV_ENCAP4, key.ip4, secctx);
		ret = encap_and_redirect_netdev(ctx, &key, secctx, TRACE_PAYLOAD_LEN);
		if (ret == IPSEC_ENDPOINT)
			return CTX_ACT_OK;
		else if (ret != DROP_NO_TUNNEL_ENDPOINT)
			return ret;
	}
#endif

	info = ipcache_lookup4(&IPCACHE_MAP, ip4->daddr, V4_CACHE_KEY_LEN);
	if (info == NULL || info->sec_label == WORLD_ID) {
		/* We have received a packet for which no ipcache entry exists,
		 * we do not know what to do with this packet, drop it.
		 *
		 * The info == NULL test is soley to satisfy verifier requirements
		 * as in Cilium case we'll always hit the 0.0.0.0/32 catch-all
		 * entry. Therefore we need to test for WORLD_ID. It is clearly
		 * wrong to route a ctx to cilium_host for which we don't know
		 * anything about it as otherwise we'll run into a routing loop.
		 */
		return DROP_UNROUTABLE;
	}

#ifdef ENABLE_IPSEC
	if (info && info->key && info->tunnel_endpoint) {
		__u8 key = get_min_encrypt_key(info->key);

		set_encrypt_key_meta(ctx, key);
#ifdef IP_POOLS
		set_encrypt_dip(ctx, info->tunnel_endpoint);
#else
		set_identity_meta(ctx, secctx);
#endif
	}
#endif
	return CTX_ACT_OK;
}

static __always_inline int
tail_handle_ipv4(struct __ctx_buff *ctx, __u32 ipcache_srcid, const bool from_host)
{
	__u32 proxy_identity = ctx_load_meta(ctx, CB_SRC_IDENTITY);
	int ret;

	ctx_store_meta(ctx, CB_SRC_IDENTITY, 0);

	ret = handle_ipv4(ctx, proxy_identity, ipcache_srcid, from_host);
	if (IS_ERR(ret))
		return send_drop_notify_error(ctx, proxy_identity,
					      ret, CTX_ACT_DROP, METRIC_INGRESS);
	return ret;
}

__section_tail(CILIUM_MAP_CALLS, CILIUM_CALL_IPV4_FROM_HOST)
int tail_handle_ipv4_from_host(struct __ctx_buff *ctx)
{
	__u32 ipcache_srcid = 0;

#if defined(ENABLE_HOST_FIREWALL) && !defined(ENABLE_MASQUERADE)
	ipcache_srcid = ctx_load_meta(ctx, CB_IPCACHE_SRC_LABEL);
	ctx_store_meta(ctx, CB_IPCACHE_SRC_LABEL, 0);
#endif

	return tail_handle_ipv4(ctx, ipcache_srcid, true);
}

__section_tail(CILIUM_MAP_CALLS, CILIUM_CALL_IPV4_FROM_LXC)
int tail_handle_ipv4_from_netdev(struct __ctx_buff *ctx)
{
	return tail_handle_ipv4(ctx, 0, false);
}
#endif /* ENABLE_IPV4 */

#ifdef ENABLE_IPSEC
#ifndef ENCAP_IFINDEX
static __always_inline int
do_netdev_encrypt_pools(struct __ctx_buff *ctx __maybe_unused)
{
	int ret = 0;
#ifdef IP_POOLS
	__u32 tunnel_endpoint = 0;
	void *data, *data_end;
	__u32 tunnel_source = IPV4_ENCRYPT_IFACE;
	struct iphdr *iphdr;
	__be32 sum;

	tunnel_endpoint = ctx_load_meta(ctx, 4);
	ctx->mark = 0;

	if (!revalidate_data(ctx, &data, &data_end, &iphdr)) {
		ret = DROP_INVALID;
		goto drop_err;
	}

	/* When IP_POOLS is enabled ip addresses are not
	 * assigned on a per node basis so lacking node
	 * affinity we can not use IP address to assign the
	 * destination IP. Instead rewrite it here from cb[].
	 */
	sum = csum_diff(&iphdr->daddr, 4, &tunnel_endpoint, 4, 0);
	if (ctx_store_bytes(ctx, ETH_HLEN + offsetof(struct iphdr, daddr),
	    &tunnel_endpoint, 4, 0) < 0) {
		ret = DROP_WRITE_ERROR;
		goto drop_err;
	}
	if (l3_csum_replace(ctx, ETH_HLEN + offsetof(struct iphdr, check),
	    0, sum, 0) < 0) {
		ret = DROP_CSUM_L3;
		goto drop_err;
	}

	if (!revalidate_data(ctx, &data, &data_end, &iphdr)) {
		ret = DROP_INVALID;
		goto drop_err;
	}

	sum = csum_diff(&iphdr->saddr, 4, &tunnel_source, 4, 0);
	if (ctx_store_bytes(ctx, ETH_HLEN + offsetof(struct iphdr, saddr),
	    &tunnel_source, 4, 0) < 0) {
		ret = DROP_WRITE_ERROR;
		goto drop_err;
	}
	if (l3_csum_replace(ctx, ETH_HLEN + offsetof(struct iphdr, check),
	    0, sum, 0) < 0) {
		ret = DROP_CSUM_L3;
		goto drop_err;
	}
drop_err:
#endif /* IP_POOLS */
	return ret;
}

static __always_inline int
do_netdev_encrypt_fib(struct __ctx_buff *ctx __maybe_unused,
		      __u16 proto __maybe_unused,
		      int *encrypt_iface __maybe_unused)
{
	int ret = 0;
	/* Only do FIB lookup if both the BPF helper is supported and we know
	 * the egress ineterface. If we don't have an egress interface,
	 * typically in an environment with many egress devs than we have
	 * to let the stack decide how to egress the packet. EKS is the
	 * example of an environment with multiple egress interfaces.
	 */
#if defined(BPF_HAVE_FIB_LOOKUP) && defined(ENCRYPT_IFACE)
	struct bpf_fib_lookup fib_params = {};
	void *data, *data_end;
	int err;

	if (proto ==  bpf_htons(ETH_P_IP)) {
		struct iphdr *ip4;

		if (!revalidate_data(ctx, &data, &data_end, &ip4)) {
			ret = DROP_INVALID;
			goto drop_err_fib;
		}

		fib_params.family = AF_INET;
		fib_params.ipv4_src = ip4->saddr;
		fib_params.ipv4_dst = ip4->daddr;
	} else {
		struct ipv6hdr *ip6;

		if (!revalidate_data(ctx, &data, &data_end, &ip6)) {
			ret = DROP_INVALID;
			goto drop_err_fib;
		}

		fib_params.family = AF_INET6;
		ipv6_addr_copy((union v6addr *) &fib_params.ipv6_src, (union v6addr *) &ip6->saddr);
		ipv6_addr_copy((union v6addr *) &fib_params.ipv6_dst, (union v6addr *) &ip6->daddr);
	}

	fib_params.ifindex = *encrypt_iface;

	err = fib_lookup(ctx, &fib_params, sizeof(fib_params),
		    BPF_FIB_LOOKUP_DIRECT | BPF_FIB_LOOKUP_OUTPUT);
	if (err != 0) {
		ret = DROP_NO_FIB;
		goto drop_err_fib;
	}
	if (eth_store_daddr(ctx, fib_params.dmac, 0) < 0) {
		ret = DROP_WRITE_ERROR;
		goto drop_err_fib;
	}
	if (eth_store_saddr(ctx, fib_params.smac, 0) < 0) {
		ret = DROP_WRITE_ERROR;
		goto drop_err_fib;
	}
	*encrypt_iface = fib_params.ifindex;
drop_err_fib:
#endif /* BPF_HAVE_FIB_LOOKUP */
	return ret;
}

static __always_inline int do_netdev_encrypt(struct __ctx_buff *ctx, __u16 proto)
{
	int encrypt_iface = 0;
	int ret = 0;
#if defined(ENCRYPT_IFACE) && defined(BPF_HAVE_FIB_LOOKUP)
	encrypt_iface = ENCRYPT_IFACE;
#endif
	ret = do_netdev_encrypt_pools(ctx);
	if (ret)
		return send_drop_notify_error(ctx, 0, ret, CTX_ACT_DROP, METRIC_INGRESS);

	ret = do_netdev_encrypt_fib(ctx, proto, &encrypt_iface);
	if (ret)
		return send_drop_notify_error(ctx, 0, ret, CTX_ACT_DROP, METRIC_INGRESS);

	bpf_clear_meta(ctx);
#ifdef BPF_HAVE_FIB_LOOKUP
	/* Redirect only works if we have a fib lookup to set the MAC
	 * addresses. Otherwise let the stack do the routing and fib
	 * Note, without FIB lookup implemented the packet may have
	 * incorrect dmac leaving bpf_host so will need to mark as
	 * PACKET_HOST or otherwise fixup MAC addresses.
	 */
	if (encrypt_iface)
		return redirect(encrypt_iface, 0);
#endif
	return CTX_ACT_OK;
}

#else /* ENCAP_IFINDEX */
static __always_inline int do_netdev_encrypt_encap(struct __ctx_buff *ctx)
{
	__u32 seclabel, tunnel_endpoint = 0;

	seclabel = get_identity(ctx);
	tunnel_endpoint = ctx_load_meta(ctx, 4);
	ctx->mark = 0;

	bpf_clear_meta(ctx);
	return __encap_and_redirect_with_nodeid(ctx, tunnel_endpoint, seclabel, TRACE_PAYLOAD_LEN);
}

static __always_inline int do_netdev_encrypt(struct __ctx_buff *ctx, __u16 proto __maybe_unused)
{
	return do_netdev_encrypt_encap(ctx);
}
#endif /* ENCAP_IFINDEX */
#endif /* ENABLE_IPSEC */

static __always_inline int
do_netdev(struct __ctx_buff *ctx, __u16 proto, const bool from_host)
{
	__u32 __maybe_unused identity = 0;
	__u32 __maybe_unused ipcache_srcid = 0;
	int ret;

#ifdef ENABLE_IPSEC
	if (from_host) {
		__u32 magic = ctx->mark & MARK_MAGIC_HOST_MASK;

		if (magic == MARK_MAGIC_ENCRYPT)
			return do_netdev_encrypt(ctx, proto);
	} else {
		int done = do_decrypt(ctx, proto);

		if (!done)
			return CTX_ACT_OK;
	}
#endif
	bpf_clear_meta(ctx);

	if (from_host) {
		int trace = TRACE_FROM_HOST;
		bool from_proxy;

		from_proxy = inherit_identity_from_host(ctx, &identity);
		if (from_proxy)
			trace = TRACE_FROM_PROXY;
		send_trace_notify(ctx, trace, identity, 0, 0,
				  ctx->ingress_ifindex, 0, TRACE_PAYLOAD_LEN);
	} else {
		bpf_skip_nodeport_clear(ctx);
		send_trace_notify(ctx, TRACE_FROM_NETWORK, 0, 0, 0,
				  ctx->ingress_ifindex, 0, TRACE_PAYLOAD_LEN);
	}

	switch (proto) {
# if defined ENABLE_ARP_PASSTHROUGH || defined ENABLE_ARP_RESPONDER
	case bpf_htons(ETH_P_ARP):
		ret = CTX_ACT_OK;
		break;
# endif
#ifdef ENABLE_IPV6
	case bpf_htons(ETH_P_IPV6):
		identity = resolve_srcid_ipv6(ctx, identity, from_host);
		ctx_store_meta(ctx, CB_SRC_IDENTITY, identity);
		if (from_host)
			ep_tail_call(ctx, CILIUM_CALL_IPV6_FROM_HOST);
		else
			ep_tail_call(ctx, CILIUM_CALL_IPV6_FROM_LXC);
		/* See comment below for IPv4. */
		return send_drop_notify_error(ctx, identity, DROP_MISSED_TAIL_CALL,
					      CTX_ACT_OK, METRIC_INGRESS);
#endif
#ifdef ENABLE_IPV4
	case bpf_htons(ETH_P_IP):
		identity = resolve_srcid_ipv4(ctx, identity, &ipcache_srcid,
					      from_host);
		ctx_store_meta(ctx, CB_SRC_IDENTITY, identity);
		if (from_host) {
# if defined(ENABLE_HOST_FIREWALL) && !defined(ENABLE_MASQUERADE)
			/* If we don't rely on BPF-based masquerading, we need
			 * to pass the srcid from ipcache to host firewall. See
			 * comment in ipv4_host_policy_egress() for details.
			 */
			ctx_store_meta(ctx, CB_IPCACHE_SRC_LABEL, ipcache_srcid);
# endif
			ep_tail_call(ctx, CILIUM_CALL_IPV4_FROM_HOST);
		} else {
			ep_tail_call(ctx, CILIUM_CALL_IPV4_FROM_LXC);
		}
		/* We are not returning an error here to always allow traffic to
		 * the stack in case maps have become unavailable.
		 *
		 * Note: Since drop notification requires a tail call as well,
		 * this notification is unlikely to succeed.
		 */
		return send_drop_notify_error(ctx, identity, DROP_MISSED_TAIL_CALL,
					      CTX_ACT_OK, METRIC_INGRESS);
#endif
	default:
#ifdef ENABLE_HOST_FIREWALL
		ret = send_drop_notify_error(ctx, identity, DROP_UNKNOWN_L3,
					     CTX_ACT_DROP, METRIC_INGRESS);
#else
		/* Pass unknown traffic to the stack */
		ret = CTX_ACT_OK;
#endif /* ENABLE_HOST_FIREWALL */
	}

	return ret;
}

/**
 * handle_netdev
 * @ctx		The packet context for this program
 * @from_host	True if the packet is from the local host
 *
 * Handle netdev traffic coming towards the Cilium-managed network.
 */
static __always_inline int
handle_netdev(struct __ctx_buff *ctx, const bool from_host)
{
	__u16 proto;

	if (!validate_ethertype(ctx, &proto)) {
#ifdef ENABLE_HOST_FIREWALL
		int ret = DROP_UNSUPPORTED_L2;

		return send_drop_notify(ctx, SECLABEL, WORLD_ID, 0, ret,
					CTX_ACT_DROP, METRIC_EGRESS);
#else
		send_trace_notify(ctx, TRACE_TO_STACK, HOST_ID, 0, 0, 0,
				  REASON_FORWARDED, 0);
		/* Pass unknown traffic to the stack */
		return CTX_ACT_OK;
#endif /* ENABLE_HOST_FIREWALL */
	}

	return do_netdev(ctx, proto, from_host);
}

/*
 * from-netdev is attached as a tc ingress filter to one or more physical devices
 * managed by Cilium (e.g., eth0). This program is only attached when:
 * - the host firewall is enabled, or
 * - BPF NodePort is enabled
 */
__section("from-netdev")
int from_netdev(struct __ctx_buff *ctx)
{
	return handle_netdev(ctx, false);
}

/*
 * from-host is attached as a tc egress filter to the node's 'cilium_host'
 * interface if present.
 */
__section("from-host")
int from_host(struct __ctx_buff *ctx)
{
	/* Traffic from the host ns going through cilium_host device must
	 * not be subject to EDT rate-limiting.
	 */
	edt_set_aggregate(ctx, 0);
	return handle_netdev(ctx, true);
}

/*
 * to-netdev is attached as a tc egress filter to one or more physical devices
 * managed by Cilium (e.g., eth0). This program is only attached when:
 * - the host firewall is enabled, or
 * - BPF NodePort is enabled
 */
__section("to-netdev")
int to_netdev(struct __ctx_buff *ctx __maybe_unused)
{
	__u32 __maybe_unused src_id = 0;
	__u16 __maybe_unused proto = 0;
	int ret = CTX_ACT_OK;

#ifdef ENABLE_HOST_FIREWALL
	if (!proto && !validate_ethertype(ctx, &proto)) {
		ret = DROP_UNSUPPORTED_L2;
		goto out;
	}

	policy_clear_mark(ctx);

	switch (proto) {
# if defined ENABLE_ARP_PASSTHROUGH || defined ENABLE_ARP_RESPONDER
	case bpf_htons(ETH_P_ARP):
		ret = CTX_ACT_OK;
		break;
# endif
# ifdef ENABLE_IPV6
	case bpf_htons(ETH_P_IPV6):
		ret = handle_to_netdev_ipv6(ctx);
		break;
# endif
# ifdef ENABLE_IPV4
	case bpf_htons(ETH_P_IP): {
		void *data, *data_end;
		struct iphdr *ip4;
		__u32 ipcache_srcid = 0;

		/* to-netdev is attached to the egress path of the native
		 * device.
		 */
		if ((ctx->mark & MARK_MAGIC_HOST_MASK) == MARK_MAGIC_HOST)
			src_id = HOST_ID;
		src_id = resolve_srcid_ipv4(ctx, src_id, &ipcache_srcid, true);

		if (!revalidate_data(ctx, &data, &data_end, &ip4))
			return DROP_INVALID;

		/* We need to pass the srcid from ipcache to host firewall. See
		 * comment in ipv4_host_policy_egress() for details.
		 */
		ret = ipv4_host_policy_egress(ctx, src_id, ipcache_srcid);
		break;
	}
# endif
	default:
		ret = DROP_UNKNOWN_L3;
		break;
	}
out:
	if (IS_ERR(ret))
		return send_drop_notify_error(ctx, src_id, ret, CTX_ACT_DROP,
					      METRIC_EGRESS);
#endif /* ENABLE_HOST_FIREWALL */

#if defined(ENABLE_BANDWIDTH_MANAGER)
	ret = edt_sched_departure(ctx);
	/* No send_drop_notify_error() here given we're rate-limiting. */
	if (ret == CTX_ACT_DROP) {
		update_metrics(ctx_full_len(ctx), METRIC_EGRESS,
			       -DROP_EDT_HORIZON);
		return ret;
	}
#endif

#if defined(ENABLE_NODEPORT) && \
	(!defined(ENABLE_DSR) || \
	 (defined(ENABLE_DSR) && defined(ENABLE_DSR_HYBRID)) || \
	 defined(ENABLE_MASQUERADE) || \
	 defined(ENABLE_EGRESS_GATEWAY))
	if ((ctx->mark & MARK_MAGIC_SNAT_DONE) != MARK_MAGIC_SNAT_DONE) {
		ret = handle_nat_fwd(ctx);
		if (IS_ERR(ret))
			return send_drop_notify_error(ctx, 0, ret,
						      CTX_ACT_DROP,
						      METRIC_EGRESS);
	}
#endif
#ifdef ENABLE_HEALTH_CHECK
	ret = lb_handle_health(ctx);
	if (IS_ERR(ret))
		return send_drop_notify_error(ctx, 0, ret, CTX_ACT_DROP,
					      METRIC_EGRESS);
#endif
	send_trace_notify(ctx, TRACE_TO_NETWORK, src_id, 0, 0,
			  0, ret, 0);
	return ret;
}

/*
 * to-host is attached as a tc ingress filter to both the 'cilium_host' and
 * 'cilium_net' devices if present.
 */
__section("to-host")
int to_host(struct __ctx_buff *ctx)
{
	__u32 magic = ctx_load_meta(ctx, ENCRYPT_OR_PROXY_MAGIC);
	__u16 __maybe_unused proto = 0;
	int ret = CTX_ACT_OK;
	bool traced = false;
	__u32 srcID = 0;

	if ((magic & MARK_MAGIC_HOST_MASK) == MARK_MAGIC_ENCRYPT) {
		ctx->mark = magic; /* CB_ENCRYPT_MAGIC */
		srcID = ctx_load_meta(ctx, CB_ENCRYPT_IDENTITY);
		set_identity_mark(ctx, srcID);
	} else if ((magic & 0xFFFF) == MARK_MAGIC_TO_PROXY) {
		/* Upper 16 bits may carry proxy port number */
		__be16 port = magic >> 16;

		ctx_store_meta(ctx, 0, CB_PROXY_MAGIC);
		ret = ctx_redirect_to_proxy_first(ctx, port);
		if (IS_ERR(ret))
			goto out;
		/* We already traced this in the previous prog with more
		 * background context, skip trace here.
		 */
		traced = true;
	}

#ifdef ENABLE_IPSEC
	/* Encryption stack needs this when IPSec headers are
	 * rewritten without FIB helper because we do not yet
	 * know correct MAC address which will cause the stack
	 * to mark as PACKET_OTHERHOST and drop.
	 */
	ctx_change_type(ctx, PACKET_HOST);
#endif

	if (!traced)
		send_trace_notify(ctx, TRACE_TO_STACK, srcID, 0, 0,
				  CILIUM_IFINDEX, ret, 0);

#ifdef ENABLE_HOST_FIREWALL
	if (!validate_ethertype(ctx, &proto)) {
		ret = DROP_UNSUPPORTED_L2;
		goto out;
	}

	policy_clear_mark(ctx);

	switch (proto) {
# if defined ENABLE_ARP_PASSTHROUGH || defined ENABLE_ARP_RESPONDER
	case bpf_htons(ETH_P_ARP):
		ret = CTX_ACT_OK;
		break;
# endif
# ifdef ENABLE_IPV6
	case bpf_htons(ETH_P_IPV6):
		ret = ipv6_host_policy_ingress(ctx, &srcID);
		break;
# endif
# ifdef ENABLE_IPV4
	case bpf_htons(ETH_P_IP):
		ret = ipv4_host_policy_ingress(ctx, &srcID);
		break;
# endif
	default:
		ret = DROP_UNKNOWN_L3;
		break;
	}
#else
	ret = CTX_ACT_OK;
#endif /* ENABLE_HOST_FIREWALL */

out:
	if (IS_ERR(ret))
		return send_drop_notify_error(ctx, srcID, ret, CTX_ACT_DROP,
					      METRIC_INGRESS);

	return ret;
}

#if defined(ENABLE_HOST_FIREWALL) && !defined(ENABLE_ROUTING)
#ifdef ENABLE_IPV6
declare_tailcall_if(__or(__and(is_defined(ENABLE_IPV4), is_defined(ENABLE_IPV6)),
			 is_defined(DEBUG)), CILIUM_CALL_IPV6_TO_HOST_POLICY_ONLY)
int tail_ipv6_host_policy_ingress(struct __ctx_buff *ctx)
{
	__u32 srcID = 0;
	int ret;

	ret = ipv6_host_policy_ingress(ctx, &srcID);
	if (IS_ERR(ret))
		return send_drop_notify_error(ctx, srcID, ret, CTX_ACT_DROP,
					      METRIC_INGRESS);
	return ret;
}
#endif /* ENABLE_IPV6 */

#ifdef ENABLE_IPV4
declare_tailcall_if(__or(__and(is_defined(ENABLE_IPV4), is_defined(ENABLE_IPV6)),
			 is_defined(DEBUG)), CILIUM_CALL_IPV4_TO_HOST_POLICY_ONLY)
int tail_ipv4_host_policy_ingress(struct __ctx_buff *ctx)
{
	__u32 srcID = 0;
	int ret;

	ret = ipv4_host_policy_ingress(ctx, &srcID);
	if (IS_ERR(ret))
		return send_drop_notify_error(ctx, srcID, ret, CTX_ACT_DROP,
					      METRIC_INGRESS);
	return ret;
}
#endif /* ENABLE_IPV4 */

static __always_inline int
/* Handles packet from a local endpoint entering the host namespace. Applies
 * ingress host policies.
 */
to_host_from_lxc(struct __ctx_buff *ctx __maybe_unused)
{
	int ret = CTX_ACT_OK;
	__u16 proto = 0;

	if (!validate_ethertype(ctx, &proto)) {
		ret = DROP_UNSUPPORTED_L2;
		goto out;
	}

	switch (proto) {
# if defined ENABLE_ARP_PASSTHROUGH || defined ENABLE_ARP_RESPONDER
	case bpf_htons(ETH_P_ARP):
		ret = CTX_ACT_OK;
		break;
# endif
# ifdef ENABLE_IPV6
	case bpf_htons(ETH_P_IPV6):
		invoke_tailcall_if(__or(__and(is_defined(ENABLE_IPV4),
					      is_defined(ENABLE_IPV6)),
					is_defined(DEBUG)),
				   CILIUM_CALL_IPV6_TO_HOST_POLICY_ONLY,
				   tail_ipv6_host_policy_ingress);
		break;
# endif
# ifdef ENABLE_IPV4
	case bpf_htons(ETH_P_IP):
		invoke_tailcall_if(__or(__and(is_defined(ENABLE_IPV4),
					      is_defined(ENABLE_IPV6)),
					is_defined(DEBUG)),
				   CILIUM_CALL_IPV6_TO_HOST_POLICY_ONLY,
				   tail_ipv4_host_policy_ingress);
		break;
# endif
	default:
		ret = DROP_UNKNOWN_L3;
		break;
	}

out:
	if (IS_ERR(ret))
		return send_drop_notify_error(ctx, 0, ret, CTX_ACT_DROP,
					      METRIC_INGRESS);
	return ret;
}

/* Handles packets that left the host namespace and will enter a local
 * endpoint's namespace. Applies egress host policies before handling
 * control back to bpf_lxc.
 */
static __always_inline int
from_host_to_lxc(struct __ctx_buff *ctx)
{
	int ret = CTX_ACT_OK;
	__u16 proto = 0;

	if (!validate_ethertype(ctx, &proto))
		return DROP_UNSUPPORTED_L2;

	switch (proto) {
# if defined ENABLE_ARP_PASSTHROUGH || defined ENABLE_ARP_RESPONDER
	case bpf_htons(ETH_P_ARP):
		ret = CTX_ACT_OK;
		break;
# endif
# ifdef ENABLE_IPV6
	case bpf_htons(ETH_P_IPV6):
		ret = ipv6_host_policy_egress(ctx, HOST_ID);
		break;
# endif
# ifdef ENABLE_IPV4
	case bpf_htons(ETH_P_IP):
		/* The last parameter, ipcache_srcid, is only required when
		 * the src_id is not HOST_ID. For details, see
		 * whitelist_snated_egress_connections.
		 * We only arrive here from bpf_lxc if we know the
		 * src_id is HOST_ID. Therefore, we don't need to pass a value
		 * for the last parameter. That avoids an ipcache lookup.
		 */
		ret = ipv4_host_policy_egress(ctx, HOST_ID, 0);
		break;
# endif
	default:
		ret = DROP_UNKNOWN_L3;
		break;
	}

	return ret;
}

/* When per-endpoint routes are enabled, packets to and from local endpoints
 * will tail call into this program to enforce egress and ingress host policies.
 * Packets to the local endpoints will then tail call back to the original
 * bpf_lxc program.
 */
__section_tail(CILIUM_MAP_POLICY, TEMPLATE_HOST_EP_ID)
handle_lxc_traffic(struct __ctx_buff *ctx)
{
	bool from_host = ctx_load_meta(ctx, CB_FROM_HOST);
	__u32 lxc_id;
	int ret;

	if (from_host) {
		ret = from_host_to_lxc(ctx);
		if (IS_ERR(ret))
			return send_drop_notify_error(ctx, HOST_ID, ret, CTX_ACT_DROP,
						      METRIC_EGRESS);

		lxc_id = ctx_load_meta(ctx, CB_DST_ENDPOINT_ID);
		ctx_store_meta(ctx, CB_SRC_LABEL, HOST_ID);
		tail_call_dynamic(ctx, &POLICY_CALL_MAP, lxc_id);
		return DROP_MISSED_TAIL_CALL;
	}

	return to_host_from_lxc(ctx);
}
#endif /* ENABLE_HOST_FIREWALL && !ENABLE_ROUTING */

BPF_LICENSE("GPL");