/*
 * Copyright (c) 2007-2013 Nicira, Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA
 */

#include <linux/version.h>

#include <linux/module.h>
#include <linux/if.h>
#include <linux/if_tunnel.h>
#include <linux/if_vlan.h>
#include <linux/icmp.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/kernel.h>
#include <linux/kmod.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/spinlock.h>

#include <net/gre.h>
#include <net/icmp.h>
#include <net/mpls.h>
#include <net/protocol.h>
#include <net/route.h>
#include <net/xfrm.h>

#include "gso.h"
#include "vlan.h"

#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,37) && \
	!defined(HAVE_VLAN_BUG_WORKAROUND)
#include <linux/module.h>

static int vlan_tso __read_mostly;
module_param(vlan_tso, int, 0644);
MODULE_PARM_DESC(vlan_tso, "Enable TSO for VLAN packets");
#else
#define vlan_tso true
#endif

#if LINUX_VERSION_CODE < KERNEL_VERSION(3,16,0)
static bool dev_supports_vlan_tx(struct net_device *dev)
{
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,37)
	return true;
#elif defined(HAVE_VLAN_BUG_WORKAROUND)
	return dev->features & NETIF_F_HW_VLAN_TX;
#else
	/* Assume that the driver is buggy. */
	return false;
#endif
}

/* Strictly this is not needed and will be optimised out
 * as this code is guarded by if LINUX_VERSION_CODE < KERNEL_VERSION(3,16,0).
 * It is here to make things explicit should the compatibility
 * code be extended in some way prior extending its life-span
 * beyond v3.16.
 */
static bool supports_mpls_gso(void)
{
/* MPLS GSO was introduced in v3.11, however it was not correctly
 * activated using mpls_features until v3.16. */
#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,16,0)
	return true;
#else
	return false;
#endif
}

int rpl_dev_queue_xmit(struct sk_buff *skb)
{
#undef dev_queue_xmit
	int err = -ENOMEM;
	bool vlan, mpls;

	vlan = mpls = false;

	/* Avoid traversing any VLAN tags that are present to determine if
	 * the ethtype is MPLS. Instead compare the mac_len (end of L2) and
	 * skb_network_offset() (beginning of L3) whose inequality will
	 * indicate the presence of an MPLS label stack. */
	if (skb->mac_len != skb_network_offset(skb) && !supports_mpls_gso())
		mpls = true;

	if (skb_vlan_tag_present(skb) && !dev_supports_vlan_tx(skb->dev))
		vlan = true;

	if (vlan || mpls) {
		int features;

		features = netif_skb_features(skb);

		if (vlan) {
			if (!vlan_tso)
				features &= ~(NETIF_F_TSO | NETIF_F_TSO6 |
					      NETIF_F_UFO | NETIF_F_FSO);

			skb = vlan_insert_tag_set_proto(skb, skb->vlan_proto,
							skb_vlan_tag_get(skb));
			if (unlikely(!skb))
				return err;
			vlan_set_tci(skb, 0);
		}

		/* As of v3.11 the kernel provides an mpls_features field in
		 * struct net_device which allows devices to advertise which
		 * features its supports for MPLS. This value defaults to
		 * NETIF_F_SG and as of v3.16.
		 *
		 * This compatibility code is intended for kernels older
		 * than v3.16 that do not support MPLS GSO and do not
		 * use mpls_features. Thus this code uses NETIF_F_SG
		 * directly in place of mpls_features.
		 */
		if (mpls)
			features &= NETIF_F_SG;

		if (netif_needs_gso(skb, features)) {
			struct sk_buff *nskb;

			nskb = skb_gso_segment(skb, features);
			if (!nskb) {
				if (unlikely(skb_cloned(skb) &&
				    pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
					goto drop;

				skb_shinfo(skb)->gso_type &= ~SKB_GSO_DODGY;
				goto xmit;
			}

			if (IS_ERR(nskb)) {
				err = PTR_ERR(nskb);
				goto drop;
			}
			consume_skb(skb);
			skb = nskb;

			do {
				nskb = skb->next;
				skb->next = NULL;
				err = dev_queue_xmit(skb);
				skb = nskb;
			} while (skb);

			return err;
		}
	}
xmit:
	return dev_queue_xmit(skb);

drop:
	kfree_skb(skb);
	return err;
}
#endif /* 3.16 */

#if LINUX_VERSION_CODE < KERNEL_VERSION(3,18,0)
static __be16 __skb_network_protocol(struct sk_buff *skb)
{
	__be16 type = skb->protocol;
	int vlan_depth = ETH_HLEN;

	while (type == htons(ETH_P_8021Q) || type == htons(ETH_P_8021AD)) {
		struct vlan_hdr *vh;

		if (unlikely(!pskb_may_pull(skb, vlan_depth + VLAN_HLEN)))
			return 0;

		vh = (struct vlan_hdr *)(skb->data + vlan_depth);
		type = vh->h_vlan_encapsulated_proto;
		vlan_depth += VLAN_HLEN;
	}

	if (eth_p_mpls(type))
		type = ovs_skb_get_inner_protocol(skb);

	return type;
}

static struct sk_buff *tnl_skb_gso_segment(struct sk_buff *skb,
					   netdev_features_t features,
					   bool tx_path)
{
	struct iphdr *iph = ip_hdr(skb);
	int pkt_hlen = skb_inner_network_offset(skb); /* inner l2 + tunnel hdr. */
	int mac_offset = skb_inner_mac_offset(skb);
	struct sk_buff *skb1 = skb;
	struct sk_buff *segs;
	__be16 proto = skb->protocol;
	char cb[sizeof(skb->cb)];

	/* setup whole inner packet to get protocol. */
	__skb_pull(skb, mac_offset);
	skb->protocol = __skb_network_protocol(skb);

	/* setup l3 packet to gso, to get around segmentation bug on older kernel.*/
	__skb_pull(skb, (pkt_hlen - mac_offset));
	skb_reset_mac_header(skb);
	skb_reset_network_header(skb);
	skb_reset_transport_header(skb);

	/* From 3.9 kernel skb->cb is used by skb gso. Therefore
	 * make copy of it to restore it back. */
	memcpy(cb, skb->cb, sizeof(cb));

	segs = __skb_gso_segment(skb, 0, tx_path);
	if (!segs || IS_ERR(segs))
		goto free;

	skb = segs;
	while (skb) {
		__skb_push(skb, pkt_hlen);
		skb_reset_mac_header(skb);
		skb_reset_network_header(skb);
		skb_set_transport_header(skb, sizeof(struct iphdr));
		skb->mac_len = 0;

		memcpy(ip_hdr(skb), iph, pkt_hlen);
		memcpy(skb->cb, cb, sizeof(cb));
		OVS_GSO_CB(skb)->fix_segment(skb);

		skb->protocol = proto;
		skb = skb->next;
	}
free:
	consume_skb(skb1);
	return segs;
}

static int output_ip(struct sk_buff *skb)
{
	int ret = NETDEV_TX_OK;
	int err;

	memset(IPCB(skb), 0, sizeof(*IPCB(skb)));

#undef ip_local_out
	err = ip_local_out(skb);
	if (unlikely(net_xmit_eval(err)))
		ret = err;

	return ret;
}

int rpl_ip_local_out(struct sk_buff *skb)
{
	int ret = NETDEV_TX_OK;
	int id = -1;

	if (!OVS_GSO_CB(skb)->fix_segment)
		return output_ip(skb);

	if (skb_is_gso(skb)) {
		struct iphdr *iph;

		iph = ip_hdr(skb);
		id = ntohs(iph->id);
		skb = tnl_skb_gso_segment(skb, 0, false);
		if (!skb || IS_ERR(skb))
			return 0;
	}  else if (skb->ip_summed == CHECKSUM_PARTIAL) {
		int err;

		err = skb_checksum_help(skb);
		if (unlikely(err))
			return 0;
	}

	while (skb) {
		struct sk_buff *next_skb = skb->next;
		struct iphdr *iph;

		skb->next = NULL;

		iph = ip_hdr(skb);
		if (id >= 0)
			iph->id = htons(id++);

		ret = output_ip(skb);
		skb = next_skb;
	}
	return ret;
}
#endif /* 3.18 */