sfe_ipv4_udp.c - codeaurora/qca-nss-sfe - Gitiles

 /*
  * sfe_ipv4_udp.c
  *	Shortcut forwarding engine - IPv4 UDP implementation
  *
  * Copyright (c) 2013-2016, 2019-2020, The Linux Foundation. All rights reserved.
  * Copyright (c) 2021-2022 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/udp.h>
 #include <linux/etherdevice.h>
 #include <linux/lockdep.h>
 #include <linux/version.h>

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

 /*
  * sfe_ipv4_udp_sk_deliver()
  *	Deliver the packet to the protocol handler registered with Linux.
  *	To be called under rcu_read_lock()
  *	Returns:
  *	1 if the packet needs to be passed to Linux.
  *	0 if the packet is processed successfully.
  *	-1 if the packet is dropped in SFE.
  */
 static int sfe_ipv4_udp_sk_deliver(struct sk_buff *skb, struct sfe_ipv4_connection_match *cm, unsigned int ihl)
 {
 	struct udp_sock *up;
 	struct sock *sk;
 	int ret;
 	int (*encap_rcv)(struct sock *sk, struct sk_buff *skb);

 	/*
 	 * Call the decap handler for valid encap_rcv handler.
 	 */
 	up = rcu_dereference(cm->up);
 	encap_rcv = READ_ONCE(up->encap_rcv);
 	if (!encap_rcv) {
 		DEBUG_ERROR("%px: sfe: Error: up->encap_rcv is NULL\n", skb);
 		return 1;
 	}

 #if (LINUX_VERSION_CODE < KERNEL_VERSION(4, 13, 0))
 	nf_reset(skb);
 #else
 	nf_reset_ct(skb);
 #endif

 	skb_pull(skb, ihl);
 	skb_reset_transport_header(skb);

 	/*
 	 * Verify checksum before giving to encap_rcv handler function.
 	 * TODO: The following approach is ignorant for UDPLITE for now.
 	 * Instead, consider calling Linux API to do checksum validation.
 	 */
 	if (unlikely(skb->ip_summed != CHECKSUM_UNNECESSARY) && unlikely(skb->ip_summed != CHECKSUM_COMPLETE)) {
 		skb->csum = inet_compute_pseudo(skb, IPPROTO_UDP);
 		if (unlikely(__skb_checksum_complete(skb))) {
 			DEBUG_ERROR("%px: sfe: Invalid udp checksum\n", skb);
 			kfree_skb(skb);
 			return -1;
 		}
 		DEBUG_TRACE("%px: sfe: udp checksum verified in s/w correctly.\n", skb);
 	}

 	sk = (struct sock *)up;

 	/*
 	 * At this point, L4 checksum has already been verified and pkt is going
 	 * to Linux's tunnel decap-handler. Setting ip_summed field to CHECKSUM_NONE,
 	 * to ensure that later packet's inner header checksum is validated correctly.
 	 * TODO: Find the fix to set skb->ip_summed = CHECKSUM_NONE;
 	 */

 	/*
 	 * encap_rcv() returns the following value:
 	 * =0 if skb was successfully passed to the encap
 	 *    handler or was discarded by it.
 	 * >0 if skb should be passed on to UDP.
 	 * <0 if skb should be resubmitted as proto -N
 	 */
 	ret = encap_rcv(sk, skb);
 	if (unlikely(ret)) {
 		/*
 		 * If encap_rcv fails, vxlan driver drops the packet.
 		 * No need to free the skb here.
 		 */

 		DEBUG_ERROR("%px: sfe: udp-decap API return error: %d\n", skb, ret);
 		return -1;
 	}

 	return 0;
 }

 /*
  * 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 sfe_l2_info *l2_info, bool tun_outer)
 {
 	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 hw_csum;
 	bool ret;
 	int err;
 	bool bridge_flow;

 	/*
 	 * 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("%px: packet too short for UDP header\n", skb);
 		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
 	/*
 	 * 5-tuple lookup for UDP flow.
 	 */
 	cm = sfe_ipv4_find_connection_match_rcu(si, dev, IPPROTO_UDP, src_ip, src_port, dest_ip, dest_port);
 #endif
 	if (unlikely(!cm)) {

 		/*
 		 * try a 4-tuple lookup; required for tunnels like vxlan.
 		 */
 		cm = sfe_ipv4_find_connection_match_rcu(si, dev, IPPROTO_UDP, src_ip, 0, dest_ip, dest_port);
 		if (unlikely(!cm)) {
 			rcu_read_unlock();
 			sfe_ipv4_exception_stats_inc(si, SFE_IPV4_EXCEPTION_EVENT_UDP_NO_CONNECTION);
 			DEBUG_TRACE("%px: sfe: no connection found in 4-tuple lookup.\n", skb);
 			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("%px: sfe: flush on find\n", cm);
 		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

 	bridge_flow = !!(cm->flags & SFE_IPV4_CONNECTION_MATCH_FLAG_BRIDGE_FLOW);

 	/*
 	 * Does our TTL allow forwarding?
 	 */
 	if (likely(!bridge_flow)) {
 		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("%px: larger than mtu\n", cm);
 		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;
 	}

 	/*
 	 * 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("%px: Failed to unshare the cloned skb\n", skb);
 			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);
 	}

 	/*
 	 * For PPPoE packets, match server MAC and session id
 	 */
 	if (unlikely(cm->flags & SFE_IPV4_CONNECTION_MATCH_FLAG_PPPOE_DECAP)) {
 		struct pppoe_hdr *ph;
 		struct ethhdr *eth;

 		if (unlikely(!sfe_l2_parse_flag_check(l2_info, SFE_L2_PARSE_FLAGS_PPPOE_INGRESS))) {
 			rcu_read_unlock();
 			DEBUG_TRACE("%px: PPPoE header not present in packet for PPPoE rule\n", skb);
 			sfe_ipv4_exception_stats_inc(si, SFE_IPV4_EXCEPTION_EVENT_INCORRECT_PPPOE_PARSING);
 			return 0;
 		}

 		ph = (struct pppoe_hdr *)(skb->head + sfe_l2_pppoe_hdr_offset_get(l2_info));
 		eth = (struct ethhdr *)(skb->head + sfe_l2_hdr_offset_get(l2_info));
 		if (unlikely(cm->pppoe_session_id != ntohs(ph->sid)) || unlikely(!(ether_addr_equal((u8*)cm->pppoe_remote_mac, (u8 *)eth->h_source)))) {
 			DEBUG_TRACE("%px: PPPoE sessions with session IDs %d and %d or server MACs %pM and %pM did not match\n",
 							skb, cm->pppoe_session_id, htons(ph->sid), cm->pppoe_remote_mac, eth->h_source);
 			rcu_read_unlock();
 			sfe_ipv4_exception_stats_inc(si, SFE_IPV4_EXCEPTION_EVENT_INVALID_PPPOE_SESSION);
 			return 0;
 		}
 		skb->protocol = htons(l2_info->protocol);
 		this_cpu_inc(si->stats_pcpu->pppoe_decap_packets_forwarded64);

 	} else if (unlikely(sfe_l2_parse_flag_check(l2_info, SFE_L2_PARSE_FLAGS_PPPOE_INGRESS))) {

 		/*
 		 * If packet contains PPPOE header but CME doesn't contain PPPoE flag yet we are exceptioning the packet to linux
 		 */
 		rcu_read_unlock();
 		DEBUG_TRACE("%px: CME doesn't contain PPPOE flag but packet has PPPoE header\n", skb);
 		sfe_ipv4_exception_stats_inc(si, SFE_IPV4_EXCEPTION_EVENT_PPPOE_NOT_SET_IN_CME);
 		return 0;
 	}

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

 	/*
 	 * For PPPoE flows, add PPPoE header before L2 header is added.
 	 */
 	if (cm->flags & SFE_IPV4_CONNECTION_MATCH_FLAG_PPPOE_ENCAP) {
 		if (unlikely(!sfe_pppoe_add_header(skb, cm->pppoe_session_id, PPP_IP))) {
 			rcu_read_unlock();
 			DEBUG_WARN("%px: PPPoE header addition failed\n", skb);
 			sfe_ipv4_exception_stats_inc(si, SFE_IPV4_EXCEPTION_EVENT_NO_HEADROOM);
 			return 0;
 		}
 		this_cpu_inc(si->stats_pcpu->pppoe_encap_packets_forwarded64);
 	}

 	/*
 	 * TODO: VLAN header should be added here when they are supported.
 	 */

 	/*
 	 * Enable HW csum if rx checksum is verified and xmit interface is CSUM offload capable.
 	 * Note: If L4 csum at Rx was found to be incorrect, we (router) should use incremental L4 checksum here
 	 * so that HW does not re-calculate/replace the L4 csum
 	 */
 	hw_csum = !!(cm->flags & SFE_IPV4_CONNECTION_MATCH_FLAG_CSUM_OFFLOAD) && (skb->ip_summed == CHECKSUM_UNNECESSARY);

 	/*
 	 * 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.
 		 */
 		if (unlikely(!hw_csum)) {
 			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.
 		 */
 		if (unlikely(!hw_csum)) {
 			udp_csum = udph->check;
 			if (likely(udp_csum)) {
 				u32 sum;

 				/*
 				 * TODO: Use a common API for below incremental checksum calculation
 				 * for IPv4/IPv6 UDP/TCP
 				 */
 				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;
 			}
 		}
 	}

 	/*
 	 * UDP sock will be valid only in decap-path.
 	 * Call encap_rcv function associated with udp_sock in cm.
 	 */
 	if (unlikely(cm->up)) {
 		/*
 		 * Call decap handler associated with sock.
 		 * Also validates UDP checksum before calling decap handler.
 		 */
 		err = sfe_ipv4_udp_sk_deliver(skb, cm, ihl);
 		if (unlikely(err == -1)) {
 			rcu_read_unlock();
 			this_cpu_inc(si->stats_pcpu->packets_dropped64);
 			return 1;
 		} else if (unlikely(err == 1)) {
 			rcu_read_unlock();
 			this_cpu_inc(si->stats_pcpu->packets_not_forwarded64);
 			return 0;
 		}

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

 		rcu_read_unlock();
 		this_cpu_inc(si->stats_pcpu->packets_forwarded64);
 		DEBUG_TRACE("%px: sfe: sfe_ipv4_recv_udp -> encap_rcv done.\n", skb);
 		return 1;
 	}

 	/*
 	 * Decrement our TTL
 	 * Except when called from hook function in post-decap.
 	 */
 	if (likely(!bridge_flow)) {
 		iph->ttl -= (u8)(!tun_outer);
 	}

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

 	/*
 	 * If HW checksum offload is not possible, full L3 checksum and incremental L4 checksum
 	 * are used to update the packet. Setting ip_summed to CHECKSUM_UNNECESSARY ensures checksum is
 	 * not recalculated further in packet path.
 	 */
 	if (likely(hw_csum)) {
 		skb->ip_summed = CHECKSUM_PARTIAL;
 	} else {
 		iph->check = sfe_ipv4_gen_ip_csum(iph);
 		skb->ip_summed = CHECKSUM_UNNECESSARY;
 	}

 	/*
 	 * 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, ntohs(skb->protocol),
 					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 = skb->protocol;
 			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("%px: sfe: SKB MARK is NON ZERO %x\n", skb, 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;
 }
	/*
	* sfe_ipv4_udp.c
	* Shortcut forwarding engine - IPv4 UDP implementation
	*
	* Copyright (c) 2013-2016, 2019-2020, The Linux Foundation. All rights reserved.
	* Copyright (c) 2021-2022 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/udp.h>
	#include <linux/etherdevice.h>
	#include <linux/lockdep.h>
	#include <linux/version.h>

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

	/*
	* sfe_ipv4_udp_sk_deliver()
	* Deliver the packet to the protocol handler registered with Linux.
	* To be called under rcu_read_lock()
	* Returns:
	* 1 if the packet needs to be passed to Linux.
	* 0 if the packet is processed successfully.
	* -1 if the packet is dropped in SFE.
	*/
	static int sfe_ipv4_udp_sk_deliver(struct sk_buff skb, struct sfe_ipv4_connection_match cm, unsigned int ihl)
	{
	struct udp_sock *up;
	struct sock *sk;
	int ret;
	int (encap_rcv)(struct sock sk, struct sk_buff *skb);

	/*
	* Call the decap handler for valid encap_rcv handler.
	*/
	up = rcu_dereference(cm->up);
	encap_rcv = READ_ONCE(up->encap_rcv);
	if (!encap_rcv) {
	DEBUG_ERROR("%px: sfe: Error: up->encap_rcv is NULL\n", skb);
	return 1;
	}

	#if (LINUX_VERSION_CODE < KERNEL_VERSION(4, 13, 0))
	nf_reset(skb);
	#else
	nf_reset_ct(skb);
	#endif

	skb_pull(skb, ihl);
	skb_reset_transport_header(skb);

	/*
	* Verify checksum before giving to encap_rcv handler function.
	* TODO: The following approach is ignorant for UDPLITE for now.
	* Instead, consider calling Linux API to do checksum validation.
	*/
	if (unlikely(skb->ip_summed != CHECKSUM_UNNECESSARY) && unlikely(skb->ip_summed != CHECKSUM_COMPLETE)) {
	skb->csum = inet_compute_pseudo(skb, IPPROTO_UDP);
	if (unlikely(__skb_checksum_complete(skb))) {
	DEBUG_ERROR("%px: sfe: Invalid udp checksum\n", skb);
	kfree_skb(skb);
	return -1;
	}
	DEBUG_TRACE("%px: sfe: udp checksum verified in s/w correctly.\n", skb);
	}

	sk = (struct sock *)up;

	/*
	* At this point, L4 checksum has already been verified and pkt is going
	* to Linux's tunnel decap-handler. Setting ip_summed field to CHECKSUM_NONE,
	* to ensure that later packet's inner header checksum is validated correctly.
	* TODO: Find the fix to set skb->ip_summed = CHECKSUM_NONE;
	*/

	/*
	* encap_rcv() returns the following value:
	* =0 if skb was successfully passed to the encap
	* handler or was discarded by it.
	* >0 if skb should be passed on to UDP.
	* <0 if skb should be resubmitted as proto -N
	*/
	ret = encap_rcv(sk, skb);
	if (unlikely(ret)) {
	/*
	* If encap_rcv fails, vxlan driver drops the packet.
	* No need to free the skb here.
	*/

	DEBUG_ERROR("%px: sfe: udp-decap API return error: %d\n", skb, ret);
	return -1;
	}

	return 0;
	}

	/*
	* 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 sfe_l2_info *l2_info, bool tun_outer)
	{
	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 hw_csum;
	bool ret;
	int err;
	bool bridge_flow;

	/*
	* 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("%px: packet too short for UDP header\n", skb);
	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
	/*
	* 5-tuple lookup for UDP flow.
	*/
	cm = sfe_ipv4_find_connection_match_rcu(si, dev, IPPROTO_UDP, src_ip, src_port, dest_ip, dest_port);
	#endif
	if (unlikely(!cm)) {

	/*
	* try a 4-tuple lookup; required for tunnels like vxlan.
	*/
	cm = sfe_ipv4_find_connection_match_rcu(si, dev, IPPROTO_UDP, src_ip, 0, dest_ip, dest_port);
	if (unlikely(!cm)) {
	rcu_read_unlock();
	sfe_ipv4_exception_stats_inc(si, SFE_IPV4_EXCEPTION_EVENT_UDP_NO_CONNECTION);
	DEBUG_TRACE("%px: sfe: no connection found in 4-tuple lookup.\n", skb);
	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("%px: sfe: flush on find\n", cm);
	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

	bridge_flow = !!(cm->flags & SFE_IPV4_CONNECTION_MATCH_FLAG_BRIDGE_FLOW);

	/*
	* Does our TTL allow forwarding?
	*/
	if (likely(!bridge_flow)) {
	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("%px: larger than mtu\n", cm);
	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;
	}

	/*
	* 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("%px: Failed to unshare the cloned skb\n", skb);
	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);
	}

	/*
	* For PPPoE packets, match server MAC and session id
	*/
	if (unlikely(cm->flags & SFE_IPV4_CONNECTION_MATCH_FLAG_PPPOE_DECAP)) {
	struct pppoe_hdr *ph;
	struct ethhdr *eth;

	if (unlikely(!sfe_l2_parse_flag_check(l2_info, SFE_L2_PARSE_FLAGS_PPPOE_INGRESS))) {
	rcu_read_unlock();
	DEBUG_TRACE("%px: PPPoE header not present in packet for PPPoE rule\n", skb);
	sfe_ipv4_exception_stats_inc(si, SFE_IPV4_EXCEPTION_EVENT_INCORRECT_PPPOE_PARSING);
	return 0;
	}

	ph = (struct pppoe_hdr *)(skb->head + sfe_l2_pppoe_hdr_offset_get(l2_info));
	eth = (struct ethhdr *)(skb->head + sfe_l2_hdr_offset_get(l2_info));
	if (unlikely(cm->pppoe_session_id != ntohs(ph->sid)) \|\| unlikely(!(ether_addr_equal((u8)cm->pppoe_remote_mac, (u8 )eth->h_source)))) {
	DEBUG_TRACE("%px: PPPoE sessions with session IDs %d and %d or server MACs %pM and %pM did not match\n",
	skb, cm->pppoe_session_id, htons(ph->sid), cm->pppoe_remote_mac, eth->h_source);
	rcu_read_unlock();
	sfe_ipv4_exception_stats_inc(si, SFE_IPV4_EXCEPTION_EVENT_INVALID_PPPOE_SESSION);
	return 0;
	}
	skb->protocol = htons(l2_info->protocol);
	this_cpu_inc(si->stats_pcpu->pppoe_decap_packets_forwarded64);

	} else if (unlikely(sfe_l2_parse_flag_check(l2_info, SFE_L2_PARSE_FLAGS_PPPOE_INGRESS))) {

	/*
	* If packet contains PPPOE header but CME doesn't contain PPPoE flag yet we are exceptioning the packet to linux
	*/
	rcu_read_unlock();
	DEBUG_TRACE("%px: CME doesn't contain PPPOE flag but packet has PPPoE header\n", skb);
	sfe_ipv4_exception_stats_inc(si, SFE_IPV4_EXCEPTION_EVENT_PPPOE_NOT_SET_IN_CME);
	return 0;
	}

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

	/*
	* For PPPoE flows, add PPPoE header before L2 header is added.
	*/
	if (cm->flags & SFE_IPV4_CONNECTION_MATCH_FLAG_PPPOE_ENCAP) {
	if (unlikely(!sfe_pppoe_add_header(skb, cm->pppoe_session_id, PPP_IP))) {
	rcu_read_unlock();
	DEBUG_WARN("%px: PPPoE header addition failed\n", skb);
	sfe_ipv4_exception_stats_inc(si, SFE_IPV4_EXCEPTION_EVENT_NO_HEADROOM);
	return 0;
	}
	this_cpu_inc(si->stats_pcpu->pppoe_encap_packets_forwarded64);
	}

	/*
	* TODO: VLAN header should be added here when they are supported.
	*/

	/*
	* Enable HW csum if rx checksum is verified and xmit interface is CSUM offload capable.
	* Note: If L4 csum at Rx was found to be incorrect, we (router) should use incremental L4 checksum here
	* so that HW does not re-calculate/replace the L4 csum
	*/
	hw_csum = !!(cm->flags & SFE_IPV4_CONNECTION_MATCH_FLAG_CSUM_OFFLOAD) && (skb->ip_summed == CHECKSUM_UNNECESSARY);

	/*
	* 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.
	*/
	if (unlikely(!hw_csum)) {
	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.
	*/
	if (unlikely(!hw_csum)) {
	udp_csum = udph->check;
	if (likely(udp_csum)) {
	u32 sum;

	/*
	* TODO: Use a common API for below incremental checksum calculation
	* for IPv4/IPv6 UDP/TCP
	*/
	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;
	}
	}
	}

	/*
	* UDP sock will be valid only in decap-path.
	* Call encap_rcv function associated with udp_sock in cm.
	*/
	if (unlikely(cm->up)) {
	/*
	* Call decap handler associated with sock.
	* Also validates UDP checksum before calling decap handler.
	*/
	err = sfe_ipv4_udp_sk_deliver(skb, cm, ihl);
	if (unlikely(err == -1)) {
	rcu_read_unlock();
	this_cpu_inc(si->stats_pcpu->packets_dropped64);
	return 1;
	} else if (unlikely(err == 1)) {
	rcu_read_unlock();
	this_cpu_inc(si->stats_pcpu->packets_not_forwarded64);
	return 0;
	}

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

	rcu_read_unlock();
	this_cpu_inc(si->stats_pcpu->packets_forwarded64);
	DEBUG_TRACE("%px: sfe: sfe_ipv4_recv_udp -> encap_rcv done.\n", skb);
	return 1;
	}

	/*
	* Decrement our TTL
	* Except when called from hook function in post-decap.
	*/
	if (likely(!bridge_flow)) {
	iph->ttl -= (u8)(!tun_outer);
	}

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

	/*
	* If HW checksum offload is not possible, full L3 checksum and incremental L4 checksum
	* are used to update the packet. Setting ip_summed to CHECKSUM_UNNECESSARY ensures checksum is
	* not recalculated further in packet path.
	*/
	if (likely(hw_csum)) {
	skb->ip_summed = CHECKSUM_PARTIAL;
	} else {
	iph->check = sfe_ipv4_gen_ip_csum(iph);
	skb->ip_summed = CHECKSUM_UNNECESSARY;
	}

	/*
	* 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, ntohs(skb->protocol),
	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 = skb->protocol;
	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("%px: sfe: SKB MARK is NON ZERO %x\n", skb, 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;
	}