/*
 * sfe_ipv6_esp.c
 *	Shortcut forwarding engine - IPv6 ESP implementation
 *
 * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <linux/skbuff.h>
#include <net/protocol.h>
#include <net/ip6_checksum.h>
#include <linux/etherdevice.h>
#include <linux/version.h>

#include "sfe_debug.h"
#include "sfe_api.h"
#include "sfe.h"
#include "sfe_flow_cookie.h"
#include "sfe_ipv6.h"
#include "sfe_ipv6_esp.h"

/*
 * sfe_ipv6_recv_esp()
 *	Handle ESP packet receives and forwarding
 */
int sfe_ipv6_recv_esp(struct sfe_ipv6 *si, struct sk_buff *skb, struct net_device *dev,
				unsigned int len, struct ipv6hdr *iph, unsigned int ihl,
				bool sync_on_find, bool tun_outer)
{
	struct sfe_ipv6_connection_match *cm;
	struct sfe_ipv6_addr *src_ip;
	struct sfe_ipv6_addr *dest_ip;
	struct net_device *xmit_dev;
	struct inet6_protocol *ipprot;
	netdev_features_t features;
	bool bridge_flow;
	bool passthrough;
	bool fast_xmit;
	bool ret;

	/*
	 * Read the IP address from the iphdr, and set the src/dst ports to 0.
	 */
	src_ip = (struct sfe_ipv6_addr *)iph->saddr.s6_addr32;
	dest_ip = (struct sfe_ipv6_addr *)iph->daddr.s6_addr32;
	rcu_read_lock();

	/*
	 * Look for a connection match.
	 */
#ifdef CONFIG_NF_FLOW_COOKIE
	cm = si->sfe_flow_cookie_table[skb->flow_cookie & SFE_FLOW_COOKIE_MASK].match;
	if (unlikely(!cm)) {
		cm = sfe_ipv6_find_connection_match_rcu(si, dev, IPPROTO_ESP, src_ip, 0, dest_ip, 0);
	}
#else
	cm = sfe_ipv6_find_connection_match_rcu(si, dev, IPPROTO_ESP, src_ip, 0, dest_ip, 0);
#endif
	if (unlikely(!cm)) {
		rcu_read_unlock();
		sfe_ipv6_exception_stats_inc(si, SFE_IPV6_EXCEPTION_EVENT_ESP_NO_CONNECTION);

		DEBUG_TRACE("no connection found for esp packet\n");
		return 0;
	}

	/*
	 * Source interface validate.
	 */
	if (unlikely((cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_SRC_INTERFACE_CHECK) && (cm->match_dev != dev))) {
		struct sfe_ipv6_connection *c = cm->connection;
		int ret;

		spin_lock_bh(&si->lock);
		ret = sfe_ipv6_remove_connection(si, c);
		spin_unlock_bh(&si->lock);

		if (ret) {
			sfe_ipv6_flush_connection(si, c, SFE_SYNC_REASON_FLUSH);
		}
		rcu_read_unlock();
		sfe_ipv6_exception_stats_inc(si, SFE_IPV6_EXCEPTION_EVENT_INVALID_SRC_IFACE);
		DEBUG_TRACE("flush on wrong source interface check failure\n");
		return 0;
	}

	passthrough = cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_PASSTHROUGH;
	bridge_flow = !!(cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_BRIDGE_FLOW);

	/*
	 * If our packet has beern marked as "sync on find" we can't actually
	 * forward it in the fast path, but now that we've found an associated
	 * connection we need sync its status before exception it to slow path. unless
	 * it is passthrough packet.
	 * TODO: revisit to ensure that pass through traffic is not bypassing firewall for fragmented cases
	 */
	if (unlikely(sync_on_find) && !passthrough) {
		sfe_ipv6_sync_status(si, cm->connection, SFE_SYNC_REASON_STATS);
		rcu_read_unlock();

		sfe_ipv6_exception_stats_inc(si, SFE_IPV6_EXCEPTION_EVENT_ESP_IP_OPTIONS_OR_INITIAL_FRAGMENT);
		DEBUG_TRACE("Sync on find\n");
		return 0;
	}

	/*
	 * Check if skb was cloned. If it was, unshare it.
	 */
	if (unlikely(skb_cloned(skb))) {
		DEBUG_TRACE("%px: skb is a cloned skb\n", skb);
		skb = skb_unshare(skb, GFP_ATOMIC);
		if (!skb) {
			DEBUG_WARN("Failed to unshare the cloned skb\n");
			rcu_read_unlock();
			return 0;
		}

		/*
		 * Update the iphdr pointer with the unshared skb's data area.
		 */
		iph = (struct ipv6hdr *)skb->data;
	}

	/*
	 * proto decap packet.
	 *	Invoke the inet_protocol handler for delivery of the packet.
	 */
	ipprot = rcu_dereference(cm->proto);
	if (likely(ipprot)) {
		skb_reset_network_header(skb);
		skb_pull(skb, ihl);
		skb_reset_transport_header(skb);
		xmit_dev = cm->xmit_dev;
		skb->dev = xmit_dev;

		ret = ipprot->handler(skb);
		if (ret) {
			rcu_read_unlock();
			this_cpu_inc(si->stats_pcpu->packets_not_forwarded64);
			DEBUG_TRACE("ESP handler returned error %u\n", ret);
			return 0;
		}

		rcu_read_unlock();
		this_cpu_inc(si->stats_pcpu->packets_forwarded64);
		return 1;
	}

	/*
	 * esp passthrough / ip local out scenarios
	 */
	/*
	 * If our packet is larger than the MTU of the transmit interface then
	 * we can't forward it easily.
	 */
	if (unlikely(len > cm->xmit_dev_mtu)) {
		sfe_ipv6_sync_status(si, cm->connection, SFE_SYNC_REASON_STATS);
		rcu_read_unlock();

		sfe_ipv6_exception_stats_inc(si, SFE_IPV6_EXCEPTION_EVENT_ESP_NEEDS_FRAGMENTATION);
		DEBUG_TRACE("Larger than MTU\n");
		return 0;
	}

	/*
	 * need to ensure that TTL is >=2.
	 */
	if (!bridge_flow && (iph->hop_limit < 2) && passthrough) {
		sfe_ipv6_sync_status(si, cm->connection, SFE_SYNC_REASON_STATS);
		rcu_read_unlock();

		sfe_ipv6_exception_stats_inc(si, SFE_IPV6_EXCEPTION_EVENT_ESP_SMALL_TTL);
		DEBUG_TRACE("hop_limit too low\n");
		return 0;
	}

	/*
	 * decrement TTL by 1.
	 */
	iph->hop_limit = iph->hop_limit - (u8)(!bridge_flow && !tun_outer);

	/*
	 * Update DSCP
	 */
	if (unlikely(cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_DSCP_REMARK)) {
		sfe_ipv6_change_dsfield(iph, cm->dscp);
	}

	/*
	 * Update traffic stats.
	 */
	atomic_inc(&cm->rx_packet_count);
	atomic_add(len, &cm->rx_byte_count);

	xmit_dev = cm->xmit_dev;
	skb->dev = xmit_dev;

	/*
	 * write the layer - 2 header.
	 */
	if (likely(cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_WRITE_L2_HDR)) {
		if (unlikely(!(cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_WRITE_FAST_ETH_HDR))) {
			dev_hard_header(skb, xmit_dev, ETH_P_IPV6, cm->xmit_dest_mac, cm->xmit_src_mac, len);
		} else {
			/*
			 * For the simple case we write this really fast.
			 */
			struct ethhdr *eth = (struct ethhdr *)__skb_push(skb, ETH_HLEN);
			eth->h_proto = htons(ETH_P_IPV6);
			ether_addr_copy((u8 *)eth->h_dest, (u8 *)cm->xmit_dest_mac);
			ether_addr_copy((u8 *)eth->h_source, (u8 *)cm->xmit_src_mac);
		}
	}

	/*
	 * Update priority of skb.
	 */
	if (unlikely(cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_PRIORITY_REMARK)) {
		skb->priority = cm->priority;
	}

	/*
	 * Mark outgoing packet.
	 */
	if (unlikely(cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_MARK)) {
		skb->mark = cm->mark;
	}

	/*
	 * For the first packets, check if it could got fast xmit.
	 */
	if (unlikely(!(cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_FAST_XMIT_FLOW_CHECKED)
				&& (cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_FAST_XMIT_DEV_ADMISSION))){
		cm->features = netif_skb_features(skb);
		if (likely(sfe_fast_xmit_check(skb, cm->features))) {
			cm->flags |= SFE_IPV6_CONNECTION_MATCH_FLAG_FAST_XMIT;
		}
		cm->flags |= SFE_IPV6_CONNECTION_MATCH_FLAG_FAST_XMIT_FLOW_CHECKED;
	}

	features = cm->features;
	fast_xmit = !!(cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_FAST_XMIT);

	rcu_read_unlock();
	this_cpu_inc(si->stats_pcpu->packets_forwarded64);
	prefetch(skb_shinfo(skb));

	/*
	 * We do per packet condition check before we could fast xmit the
	 * packet.
	 */
	if (likely(fast_xmit && dev_fast_xmit(skb, xmit_dev, features))) {
		this_cpu_inc(si->stats_pcpu->packets_fast_xmited64);
		return 1;
	}

	/*
	 * Mark that this packet has been fast forwarded.
	 */
	skb->fast_forwarded = 1;

	dev_queue_xmit(skb);
	return 1;
}