/*
 * sfe_ipv4_udp.c
 *	Shortcut forwarding engine - IPv4 UDP implementation
 *
 * Copyright (c) 2013-2016, 2019-2020, The Linux Foundation. All rights reserved.
 * Copyright (c) 2021 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/udp.h>
#include <linux/etherdevice.h>
#include <linux/lockdep.h>

#include "sfe_debug.h"
#include "sfe_api.h"
#include "sfe.h"
#include "sfe_flow_cookie.h"
#include "sfe_ipv4.h"

/*
 * sfe_ipv4_recv_udp()
 *	Handle UDP packet receives and forwarding.
 */
int sfe_ipv4_recv_udp(struct sfe_ipv4 *si, struct sk_buff *skb, struct net_device *dev,
			     unsigned int len, struct iphdr *iph, unsigned int ihl, bool flush_on_find)
{
	struct udphdr *udph;
	__be32 src_ip;
	__be32 dest_ip;
	__be16 src_port;
	__be16 dest_port;
	struct sfe_ipv4_connection_match *cm;
	u8 ttl;
	struct net_device *xmit_dev;
	bool ret;

	/*
	 * Is our packet too short to contain a valid UDP header?
	 */
	if (unlikely(!pskb_may_pull(skb, (sizeof(struct udphdr) + ihl)))) {
		sfe_ipv4_exception_stats_inc(si, SFE_IPV4_EXCEPTION_EVENT_UDP_HEADER_INCOMPLETE);
		DEBUG_TRACE("packet too short for UDP header\n");
		return 0;
	}

	/*
	 * Read the IP address and port information.  Read the IP header data first
	 * because we've almost certainly got that in the cache.  We may not yet have
	 * the UDP header cached though so allow more time for any prefetching.
	 */
	src_ip = iph->saddr;
	dest_ip = iph->daddr;

	udph = (struct udphdr *)(skb->data + ihl);
	src_port = udph->source;
	dest_port = udph->dest;

	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_ipv4_find_connection_match_rcu(si, dev, IPPROTO_UDP, src_ip, src_port, dest_ip, dest_port);
	}
#else
	cm = sfe_ipv4_find_connection_match_rcu(si, dev, IPPROTO_UDP, src_ip, src_port, dest_ip, dest_port);
#endif
	if (unlikely(!cm)) {

		rcu_read_unlock();
		sfe_ipv4_exception_stats_inc(si, SFE_IPV4_EXCEPTION_EVENT_UDP_NO_CONNECTION);
		DEBUG_TRACE("no connection found\n");
		return 0;
	}

	/*
	 * If our packet has beern marked as "flush on find" we can't actually
	 * forward it in the fast path, but now that we've found an associated
	 * connection we can flush that out before we process the packet.
	 */
	if (unlikely(flush_on_find)) {
		struct sfe_ipv4_connection *c = cm->connection;
		spin_lock_bh(&si->lock);
		ret = sfe_ipv4_remove_connection(si, c);
		spin_unlock_bh(&si->lock);

		if (ret) {
			sfe_ipv4_flush_connection(si, c, SFE_SYNC_REASON_FLUSH);
		}
		rcu_read_unlock();
		sfe_ipv4_exception_stats_inc(si, SFE_IPV4_EXCEPTION_EVENT_UDP_IP_OPTIONS_OR_INITIAL_FRAGMENT);
		DEBUG_TRACE("flush on find\n");
		return 0;
	}

#ifdef CONFIG_XFRM
	/*
	 * We can't accelerate the flow on this direction, just let it go
	 * through the slow path.
	 */
	if (unlikely(!cm->flow_accel)) {
		rcu_read_unlock();
		this_cpu_inc(si->stats_pcpu->packets_not_forwarded64);
		return 0;
	}
#endif

	/*
	 * Does our TTL allow forwarding?
	 */
	ttl = iph->ttl;
	if (unlikely(ttl < 2)) {
		struct sfe_ipv4_connection *c = cm->connection;
		spin_lock_bh(&si->lock);
		ret = sfe_ipv4_remove_connection(si, c);
		spin_unlock_bh(&si->lock);

		if (ret) {
			sfe_ipv4_flush_connection(si, c, SFE_SYNC_REASON_FLUSH);
		}
		rcu_read_unlock();

		DEBUG_TRACE("ttl too low\n");
		sfe_ipv4_exception_stats_inc(si, SFE_IPV4_EXCEPTION_EVENT_UDP_SMALL_TTL);
		return 0;
	}

	/*
	 * 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)) {
		struct sfe_ipv4_connection *c = cm->connection;
		spin_lock_bh(&si->lock);
		ret = sfe_ipv4_remove_connection(si, c);
		spin_unlock_bh(&si->lock);

		DEBUG_TRACE("larger than mtu\n");
		if (ret) {
			sfe_ipv4_flush_connection(si, c, SFE_SYNC_REASON_FLUSH);
		}
		rcu_read_unlock();
		sfe_ipv4_exception_stats_inc(si, SFE_IPV4_EXCEPTION_EVENT_UDP_NEEDS_FRAGMENTATION);
		return 0;
	}

	/*
	 * From this point on we're good to modify the packet.
	 */

	/*
	 * Check if skb was cloned. If it was, unshare it. Because
	 * the data area is going to be written in this path and we don't want to
	 * change the cloned skb's data section.
	 */
	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 iph and udph pointers with the unshared skb's data area.
		 */
		iph = (struct iphdr *)skb->data;
		udph = (struct udphdr *)(skb->data + ihl);
	}

	/*
	 * Update DSCP
	 */
	if (unlikely(cm->flags & SFE_IPV4_CONNECTION_MATCH_FLAG_DSCP_REMARK)) {
		iph->tos = (iph->tos & SFE_IPV4_DSCP_MASK) | cm->dscp;
	}

	/*
	 * Decrement our TTL.
	 */
	iph->ttl = ttl - 1;

	/*
	 * Do we have to perform translations of the source address/port?
	 */
	if (unlikely(cm->flags & SFE_IPV4_CONNECTION_MATCH_FLAG_XLATE_SRC)) {
		u16 udp_csum;

		iph->saddr = cm->xlate_src_ip;
		udph->source = cm->xlate_src_port;

		/*
		 * Do we have a non-zero UDP checksum?  If we do then we need
		 * to update it.
		 */
		udp_csum = udph->check;
		if (likely(udp_csum)) {
			u32 sum;

			if (unlikely(skb->ip_summed == CHECKSUM_PARTIAL)) {
				sum = udp_csum + cm->xlate_src_partial_csum_adjustment;
			} else {
				sum = udp_csum + cm->xlate_src_csum_adjustment;
			}

			sum = (sum & 0xffff) + (sum >> 16);
			udph->check = (u16)sum;
		}
	}

	/*
	 * Do we have to perform translations of the destination address/port?
	 */
	if (unlikely(cm->flags & SFE_IPV4_CONNECTION_MATCH_FLAG_XLATE_DEST)) {
		u16 udp_csum;

		iph->daddr = cm->xlate_dest_ip;
		udph->dest = cm->xlate_dest_port;

		/*
		 * Do we have a non-zero UDP checksum?  If we do then we need
		 * to update it.
		 */
		udp_csum = udph->check;
		if (likely(udp_csum)) {
			u32 sum;

			if (unlikely(skb->ip_summed == CHECKSUM_PARTIAL)) {
				sum = udp_csum + cm->xlate_dest_partial_csum_adjustment;
			} else {
				sum = udp_csum + cm->xlate_dest_csum_adjustment;
			}

			sum = (sum & 0xffff) + (sum >> 16);
			udph->check = (u16)sum;
		}
	}

	/*
	 * Replace the IP checksum.
	 */
	iph->check = sfe_ipv4_gen_ip_csum(iph);

	/*
	 * 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;

	/*
	 * Check to see if we need to write a header.
	 */
	if (likely(cm->flags & SFE_IPV4_CONNECTION_MATCH_FLAG_WRITE_L2_HDR)) {
		if (unlikely(!(cm->flags & SFE_IPV4_CONNECTION_MATCH_FLAG_WRITE_FAST_ETH_HDR))) {
			dev_hard_header(skb, xmit_dev, ETH_P_IP,
					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_IP);
			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_IPV4_CONNECTION_MATCH_FLAG_PRIORITY_REMARK)) {
		skb->priority = cm->priority;
	}

	/*
	 * Mark outgoing packet.
	 */
	skb->mark = cm->connection->mark;
	if (skb->mark) {
		DEBUG_TRACE("SKB MARK is NON ZERO %x\n", skb->mark);
	}

	rcu_read_unlock();

	this_cpu_inc(si->stats_pcpu->packets_forwarded64);

	/*
	 * We're going to check for GSO flags when we transmit the packet so
	 * start fetching the necessary cache line now.
	 */
	prefetch(skb_shinfo(skb));

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

	/*
	 * Send the packet on its way.
	 */
	dev_queue_xmit(skb);

	return 1;
}