qca-nss-sfe/sfe_ipv6_gre.c - manifest_repos/sdk - Git at Google

 /*
  * sfe_ipv6_gre.c
  *	Shortcut forwarding engine file for IPv6 GRE
  *
  * 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/gre.h>
 #include <net/protocol.h>
 #include <linux/etherdevice.h>
 #include <linux/version.h>
 #include <net/ip6_checksum.h>

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

 /*
  * sfe_ipv6_recv_gre()
  *	Handle GRE packet receives and forwarding.
  */
 int sfe_ipv6_recv_gre(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,
 		      struct sfe_l2_info *l2_info, bool tun_outer)
 {
 	struct sfe_ipv6_connection_match *cm;
 	struct sfe_ipv6_addr *dest_ip;
 	struct sfe_ipv6_addr *src_ip;
 	struct net_device *xmit_dev;
 	bool bridge_flow;
 	bool passthrough;
 	bool ret;

 	/*
 	 * Is our packet too short to contain a valid UDP header?
 	 */
 	if (!pskb_may_pull(skb, (sizeof(struct gre_base_hdr) + ihl))) {

 		sfe_ipv6_exception_stats_inc(si, SFE_IPV6_EXCEPTION_EVENT_GRE_HEADER_INCOMPLETE);
 		DEBUG_TRACE("packet too short for GRE 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 = (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_GRE, src_ip, 0, dest_ip, 0);
 	}
 #else
 	cm = sfe_ipv6_find_connection_match_rcu(si, dev, IPPROTO_GRE, src_ip, 0, dest_ip, 0);
 #endif
 	if (unlikely(!cm)) {
 		rcu_read_unlock();
 		sfe_ipv6_exception_stats_inc(si, SFE_IPV6_EXCEPTION_EVENT_GRE_NO_CONNECTION);
 		DEBUG_TRACE("no connection match found dev %s src ip %pI6 dest ip %pI6\n", dev->name, src_ip, dest_ip);
 		return 0;
 	}

 	/*
 	 * Do we expect an ingress VLAN tag for this flow?
 	 */
 	if (unlikely(!sfe_vlan_validate_ingress_tag(skb, cm->ingress_vlan_hdr_cnt, cm->ingress_vlan_hdr, l2_info))) {
 		rcu_read_unlock();
 		sfe_ipv6_exception_stats_inc(si, SFE_IPV6_EXCEPTION_EVENT_INGRESS_VLAN_TAG_MISMATCH);
 		DEBUG_TRACE("VLAN tag mismatch. skb=%px\n", skb);
 		return 0;
 	}

 	/*
 	 * Source interface validate.
 	 */
 	if (unlikely((cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_SRC_INTERFACE_CHECK) && (cm->match_dev != dev))) {
 		if (!(cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_SRC_INTERFACE_CHECK_NO_FLUSH)) {
 			struct sfe_ipv6_connection *c = cm->connection;
 			int ret;
 			DEBUG_TRACE("flush on source interface check failure\n");
 			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("exception the packet on source interface check failure\n");
 		return 0;
 	}

 	passthrough = cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_PASSTHROUGH;

 	/*
 	 * 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_GRE_IP_OPTIONS_OR_INITIAL_FRAGMENT);
 		DEBUG_TRACE("Sync on find\n");
 		return 0;
 	}

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

 	/*
 	 * Does our hop_limit allow forwarding?
 	 */
 	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_GRE_SMALL_TTL);
 		DEBUG_TRACE("hop_limit too low\n");
 		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 1;
 		}

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

 	/*
 	 * Check if skb has enough headroom to write L2 headers
 	 */
 	if (unlikely(skb_headroom(skb) < cm->l2_hdr_size)) {
 		rcu_read_unlock();
 		DEBUG_WARN("%px: Not enough headroom: %u\n", skb, skb_headroom(skb));
 		sfe_ipv6_exception_stats_inc(si, SFE_IPV6_EXCEPTION_EVENT_NO_HEADROOM);
 		return 0;
 	}

 	/*
 	 * protocol handler will be valid only in decap-path.
 	 */
 	if (cm->proto) {
 		struct inet6_protocol *ipprot = cm->proto;
 		skb_reset_network_header(skb);
 		skb_pull(skb, ihl);
 		skb_reset_transport_header(skb);
 		skb->fast_forwarded = 1;

 		ret = ipprot->handler(skb);
 		if (ret) {
 			this_cpu_inc(si->stats_pcpu->packets_not_forwarded64);
 			rcu_read_unlock();
 			return 1;
 		}

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

 		this_cpu_inc(si->stats_pcpu->packets_forwarded64);
 		rcu_read_unlock();
 		DEBUG_TRACE("%p: %s decap done\n",skb, __func__);
 		return 1;
 	}

 	/*
 	 * 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_GRE_NEEDS_FRAGMENTATION);
 		DEBUG_TRACE("Larger than MTU\n");
 		return 0;
 	}

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

 	iph->hop_limit -= (u8)(!bridge_flow & !tun_outer);

 	/*
 	 * 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 add VLAN tags
 	 */
 	if (unlikely(cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_INSERT_EGRESS_VLAN_TAG)) {
 		sfe_vlan_add_tag(skb, cm->egress_vlan_hdr_cnt, cm->egress_vlan_hdr);
 	}

 	if (cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_WRITE_FAST_ETH_HDR) {
 		/*
 		 * 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);
 	} else if (cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_WRITE_L2_HDR) {
 		dev_hard_header(skb, xmit_dev, ETH_P_IPV6,
 				cm->xmit_dest_mac, cm->xmit_src_mac, len);
 	}

 	/*
 	 * 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;
 	}

 	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_ipv6_gre.c
	* Shortcut forwarding engine file for IPv6 GRE
	*
	* 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/gre.h>
	#include <net/protocol.h>
	#include <linux/etherdevice.h>
	#include <linux/version.h>
	#include <net/ip6_checksum.h>

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

	/*
	* sfe_ipv6_recv_gre()
	* Handle GRE packet receives and forwarding.
	*/
	int sfe_ipv6_recv_gre(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,
	struct sfe_l2_info *l2_info, bool tun_outer)
	{
	struct sfe_ipv6_connection_match *cm;
	struct sfe_ipv6_addr *dest_ip;
	struct sfe_ipv6_addr *src_ip;
	struct net_device *xmit_dev;
	bool bridge_flow;
	bool passthrough;
	bool ret;

	/*
	* Is our packet too short to contain a valid UDP header?
	*/
	if (!pskb_may_pull(skb, (sizeof(struct gre_base_hdr) + ihl))) {

	sfe_ipv6_exception_stats_inc(si, SFE_IPV6_EXCEPTION_EVENT_GRE_HEADER_INCOMPLETE);
	DEBUG_TRACE("packet too short for GRE 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 = (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_GRE, src_ip, 0, dest_ip, 0);
	}
	#else
	cm = sfe_ipv6_find_connection_match_rcu(si, dev, IPPROTO_GRE, src_ip, 0, dest_ip, 0);
	#endif
	if (unlikely(!cm)) {
	rcu_read_unlock();
	sfe_ipv6_exception_stats_inc(si, SFE_IPV6_EXCEPTION_EVENT_GRE_NO_CONNECTION);
	DEBUG_TRACE("no connection match found dev %s src ip %pI6 dest ip %pI6\n", dev->name, src_ip, dest_ip);
	return 0;
	}

	/*
	* Do we expect an ingress VLAN tag for this flow?
	*/
	if (unlikely(!sfe_vlan_validate_ingress_tag(skb, cm->ingress_vlan_hdr_cnt, cm->ingress_vlan_hdr, l2_info))) {
	rcu_read_unlock();
	sfe_ipv6_exception_stats_inc(si, SFE_IPV6_EXCEPTION_EVENT_INGRESS_VLAN_TAG_MISMATCH);
	DEBUG_TRACE("VLAN tag mismatch. skb=%px\n", skb);
	return 0;
	}

	/*
	* Source interface validate.
	*/
	if (unlikely((cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_SRC_INTERFACE_CHECK) && (cm->match_dev != dev))) {
	if (!(cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_SRC_INTERFACE_CHECK_NO_FLUSH)) {
	struct sfe_ipv6_connection *c = cm->connection;
	int ret;
	DEBUG_TRACE("flush on source interface check failure\n");
	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("exception the packet on source interface check failure\n");
	return 0;
	}

	passthrough = cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_PASSTHROUGH;

	/*
	* 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_GRE_IP_OPTIONS_OR_INITIAL_FRAGMENT);
	DEBUG_TRACE("Sync on find\n");
	return 0;
	}

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

	/*
	* Does our hop_limit allow forwarding?
	*/
	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_GRE_SMALL_TTL);
	DEBUG_TRACE("hop_limit too low\n");
	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 1;
	}

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

	/*
	* Check if skb has enough headroom to write L2 headers
	*/
	if (unlikely(skb_headroom(skb) < cm->l2_hdr_size)) {
	rcu_read_unlock();
	DEBUG_WARN("%px: Not enough headroom: %u\n", skb, skb_headroom(skb));
	sfe_ipv6_exception_stats_inc(si, SFE_IPV6_EXCEPTION_EVENT_NO_HEADROOM);
	return 0;
	}

	/*
	* protocol handler will be valid only in decap-path.
	*/
	if (cm->proto) {
	struct inet6_protocol *ipprot = cm->proto;
	skb_reset_network_header(skb);
	skb_pull(skb, ihl);
	skb_reset_transport_header(skb);
	skb->fast_forwarded = 1;

	ret = ipprot->handler(skb);
	if (ret) {
	this_cpu_inc(si->stats_pcpu->packets_not_forwarded64);
	rcu_read_unlock();
	return 1;
	}

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

	this_cpu_inc(si->stats_pcpu->packets_forwarded64);
	rcu_read_unlock();
	DEBUG_TRACE("%p: %s decap done\n",skb, __func__);
	return 1;
	}

	/*
	* 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_GRE_NEEDS_FRAGMENTATION);
	DEBUG_TRACE("Larger than MTU\n");
	return 0;
	}

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

	iph->hop_limit -= (u8)(!bridge_flow & !tun_outer);

	/*
	* 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 add VLAN tags
	*/
	if (unlikely(cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_INSERT_EGRESS_VLAN_TAG)) {
	sfe_vlan_add_tag(skb, cm->egress_vlan_hdr_cnt, cm->egress_vlan_hdr);
	}

	if (cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_WRITE_FAST_ETH_HDR) {
	/*
	* 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);
	} else if (cm->flags & SFE_IPV6_CONNECTION_MATCH_FLAG_WRITE_L2_HDR) {
	dev_hard_header(skb, xmit_dev, ETH_P_IPV6,
	cm->xmit_dest_mac, cm->xmit_src_mac, len);
	}

	/*
	* 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;
	}

	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;
	}