/*
 * Distributed under the terms of the GNU GPL version 2.
 * Copyright (c) 2007, 2008, 2009, 2010 Nicira Networks.
 *
 * Significant portions of this file may be copied from parts of the Linux
 * kernel, by Linus Torvalds and others.
 */

/* Functions for executing flow actions. */

#include <linux/skbuff.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/in6.h>
#include <linux/if_arp.h>
#include <linux/if_vlan.h>
#include <net/inet_ecn.h>
#include <net/ip.h>
#include <net/checksum.h>

#include "actions.h"
#include "datapath.h"
#include "openvswitch/xflow.h"
#include "vport.h"

static struct sk_buff *make_writable(struct sk_buff *skb, unsigned min_headroom, gfp_t gfp)
{
	if (skb_cloned(skb)) {
		struct sk_buff *nskb;
		unsigned headroom = max(min_headroom, skb_headroom(skb));

		nskb = skb_copy_expand(skb, headroom, skb_tailroom(skb), gfp);
		if (nskb) {
			set_skb_csum_bits(skb, nskb);
			kfree_skb(skb);
			return nskb;
		}
	} else {
		unsigned int hdr_len = (skb_transport_offset(skb)
					+ sizeof(struct tcphdr));
		if (pskb_may_pull(skb, min(hdr_len, skb->len)))
			return skb;
	}
	kfree_skb(skb);
	return NULL;
}

static struct sk_buff *vlan_pull_tag(struct sk_buff *skb)
{
	struct vlan_ethhdr *vh = vlan_eth_hdr(skb);
	struct ethhdr *eh;

	/* Verify we were given a vlan packet */
	if (vh->h_vlan_proto != htons(ETH_P_8021Q) || skb->len < VLAN_ETH_HLEN)
		return skb;

	if (OVS_CB(skb)->ip_summed == OVS_CSUM_COMPLETE)
		skb->csum = csum_sub(skb->csum, csum_partial(skb->data
					+ ETH_HLEN, VLAN_HLEN, 0));

	memmove(skb->data + VLAN_HLEN, skb->data, 2 * VLAN_ETH_ALEN);

	eh = (struct ethhdr *)skb_pull(skb, VLAN_HLEN);

	skb->protocol = eh->h_proto;
	skb->mac_header += VLAN_HLEN;

	return skb;
}

static struct sk_buff *modify_vlan_tci(struct datapath *dp, struct sk_buff *skb,
				       const struct xflow_key *key, const union xflow_action *a,
				       int n_actions, gfp_t gfp)
{
	__be16 mask = a->dl_tci.mask;
	__be16 tci = a->dl_tci.tci;

	skb = make_writable(skb, VLAN_HLEN, gfp);
	if (!skb)
		return ERR_PTR(-ENOMEM);

	if (skb->protocol == htons(ETH_P_8021Q)) {
		/* Modify vlan id, but maintain other TCI values */
		struct vlan_ethhdr *vh;
		__be16 old_tci;

		if (skb->len < VLAN_ETH_HLEN)
			return skb;

		vh = vlan_eth_hdr(skb);
		old_tci = vh->h_vlan_TCI;

		vh->h_vlan_TCI = (vh->h_vlan_TCI & ~mask) | tci;

		if (OVS_CB(skb)->ip_summed == OVS_CSUM_COMPLETE) {
			__be16 diff[] = { ~old_tci, vh->h_vlan_TCI };

			skb->csum = ~csum_partial((char *)diff, sizeof(diff),
						~skb->csum);
		}
	} else {
		int err;

		/* Add vlan header */

		/* Set up checksumming pointers for checksum-deferred packets
		 * on Xen.  Otherwise, dev_queue_xmit() will try to do this
		 * when we send the packet out on the wire, and it will fail at
		 * that point because skb_checksum_setup() will not look inside
		 * an 802.1Q header. */
		err = vswitch_skb_checksum_setup(skb);
		if (unlikely(err)) {
			kfree_skb(skb);
			return ERR_PTR(err);
		}

		/* GSO is not implemented for packets with an 802.1Q header, so
		 * we have to do segmentation before we add that header.
		 *
		 * GSO does work with hardware-accelerated VLAN tagging, but we
		 * can't use hardware-accelerated VLAN tagging since it
		 * requires the device to have a VLAN group configured (with
		 * e.g. vconfig(8)) and we don't do that.
		 *
		 * Having to do this here may be a performance loss, since we
		 * can't take advantage of TSO hardware support, although it
		 * does not make a measurable network performance difference
		 * for 1G Ethernet.  Fixing that would require patching the
		 * kernel (either to add GSO support to the VLAN protocol or to
		 * support hardware-accelerated VLAN tagging without VLAN
		 * groups configured). */
		if (skb_is_gso(skb)) {
			struct sk_buff *segs;

			segs = skb_gso_segment(skb, 0);
			kfree_skb(skb);
			if (unlikely(IS_ERR(segs)))
				return ERR_CAST(segs);

			do {
				struct sk_buff *nskb = segs->next;
				int err;

				segs->next = NULL;

				/* GSO can change the checksum type so update.*/
				compute_ip_summed(segs, true);

				segs = __vlan_put_tag(segs, ntohs(tci));
				err = -ENOMEM;
				if (segs) {
					err = execute_actions(dp, segs,
							      key, a + 1,
							      n_actions - 1,
							      gfp);
				}

				if (unlikely(err)) {
					while ((segs = nskb)) {
						nskb = segs->next;
						segs->next = NULL;
						kfree_skb(segs);
					}
					return ERR_PTR(err);
				}

				segs = nskb;
			} while (segs->next);

			skb = segs;
			compute_ip_summed(skb, true);
		}

		/* The hardware-accelerated version of vlan_put_tag() works
		 * only for a device that has a VLAN group configured (with
		 * e.g. vconfig(8)), so call the software-only version
		 * __vlan_put_tag() directly instead.
		 */
		skb = __vlan_put_tag(skb, ntohs(tci));
		if (!skb)
			return ERR_PTR(-ENOMEM);

		/* GSO doesn't fix up the hardware computed checksum so this
		 * will only be hit in the non-GSO case. */
		if (OVS_CB(skb)->ip_summed == OVS_CSUM_COMPLETE)
			skb->csum = csum_add(skb->csum, csum_partial(skb->data
						+ ETH_HLEN, VLAN_HLEN, 0));
	}

	return skb;
}

static struct sk_buff *strip_vlan(struct sk_buff *skb, gfp_t gfp)
{
	skb = make_writable(skb, 0, gfp);
	if (skb)
		vlan_pull_tag(skb);

	return skb;
}

static struct sk_buff *set_dl_addr(struct sk_buff *skb,
				   const struct xflow_action_dl_addr *a,
				   gfp_t gfp)
{
	skb = make_writable(skb, 0, gfp);
	if (skb) {
		struct ethhdr *eh = eth_hdr(skb);
		if (a->type == XFLOWAT_SET_DL_SRC)
			memcpy(eh->h_source, a->dl_addr, ETH_ALEN);
		else
			memcpy(eh->h_dest, a->dl_addr, ETH_ALEN);
	}
	return skb;
}

/* Updates 'sum', which is a field in 'skb''s data, given that a 4-byte field
 * covered by the sum has been changed from 'from' to 'to'.  If set,
 * 'pseudohdr' indicates that the field is in the TCP or UDP pseudo-header.
 * Based on nf_proto_csum_replace4. */
static void update_csum(__sum16 *sum, struct sk_buff *skb,
			__be32 from, __be32 to, int pseudohdr)
{
	__be32 diff[] = { ~from, to };

	if (OVS_CB(skb)->ip_summed != OVS_CSUM_PARTIAL) {
		*sum = csum_fold(csum_partial((char *)diff, sizeof(diff),
				~csum_unfold(*sum)));
		if (OVS_CB(skb)->ip_summed == OVS_CSUM_COMPLETE && pseudohdr)
			skb->csum = ~csum_partial((char *)diff, sizeof(diff),
						~skb->csum);
	} else if (pseudohdr)
		*sum = ~csum_fold(csum_partial((char *)diff, sizeof(diff),
				csum_unfold(*sum)));
}

static bool is_ip(struct sk_buff *skb, const struct xflow_key *key)
{
	return (key->dl_type == htons(ETH_P_IP) &&
		skb->transport_header > skb->network_header);
}

static __sum16 *get_l4_checksum(struct sk_buff *skb, const struct xflow_key *key)
{
	int transport_len = skb->len - skb_transport_offset(skb);
	if (key->nw_proto == IPPROTO_TCP) {
		if (likely(transport_len >= sizeof(struct tcphdr)))
			return &tcp_hdr(skb)->check;
	} else if (key->nw_proto == IPPROTO_UDP) {
		if (likely(transport_len >= sizeof(struct udphdr)))
			return &udp_hdr(skb)->check;
	}
	return NULL;
}

static struct sk_buff *set_nw_addr(struct sk_buff *skb,
				   const struct xflow_key *key,
				   const struct xflow_action_nw_addr *a,
				   gfp_t gfp)
{
	struct iphdr *nh;
	__sum16 *check;
	__be32 *nwaddr;

	if (unlikely(!is_ip(skb, key)))
		return skb;

	skb = make_writable(skb, 0, gfp);
	if (unlikely(!skb))
		return NULL;

	nh = ip_hdr(skb);
	nwaddr = a->type == XFLOWAT_SET_NW_SRC ? &nh->saddr : &nh->daddr;

	check = get_l4_checksum(skb, key);
	if (likely(check))
		update_csum(check, skb, *nwaddr, a->nw_addr, 1);
	update_csum(&nh->check, skb, *nwaddr, a->nw_addr, 0);

	*nwaddr = a->nw_addr;

	return skb;
}

static struct sk_buff *set_nw_tos(struct sk_buff *skb,
				   const struct xflow_key *key,
				   const struct xflow_action_nw_tos *a,
				   gfp_t gfp)
{
	if (unlikely(!is_ip(skb, key)))
		return skb;

	skb = make_writable(skb, 0, gfp);
	if (skb) {
		struct iphdr *nh = ip_hdr(skb);
		u8 *f = &nh->tos;
		u8 old = *f;
		u8 new;

		/* Set the DSCP bits and preserve the ECN bits. */
		new = a->nw_tos | (nh->tos & INET_ECN_MASK);
		update_csum(&nh->check, skb, htons((u16)old),
			    htons((u16)new), 0);
		*f = new;
	}
	return skb;
}

static struct sk_buff *set_tp_port(struct sk_buff *skb,
				   const struct xflow_key *key,
				   const struct xflow_action_tp_port *a,
				   gfp_t gfp)
{
	struct udphdr *th;
	__sum16 *check;
	__be16 *port;

	if (unlikely(!is_ip(skb, key)))
		return skb;

	skb = make_writable(skb, 0, gfp);
	if (unlikely(!skb))
		return NULL;

	/* Must follow make_writable() since that can move the skb data. */
	check = get_l4_checksum(skb, key);
	if (unlikely(!check))
		return skb;

	/*
	 * Update port and checksum.
	 *
	 * This is OK because source and destination port numbers are at the
	 * same offsets in both UDP and TCP headers, and get_l4_checksum() only
	 * supports those protocols.
	 */
	th = udp_hdr(skb);
	port = a->type == XFLOWAT_SET_TP_SRC ? &th->source : &th->dest;
	update_csum(check, skb, *port, a->tp_port, 0);
	*port = a->tp_port;

	return skb;
}

/**
 * is_spoofed_arp - check for invalid ARP packet
 *
 * @skb: skbuff containing an Ethernet packet, with network header pointing
 * just past the Ethernet and optional 802.1Q header.
 * @key: flow key extracted from @skb by flow_extract()
 *
 * Returns true if @skb is an invalid Ethernet+IPv4 ARP packet: one with screwy
 * or truncated header fields or one whose inner and outer Ethernet address
 * differ.
 */
static bool is_spoofed_arp(struct sk_buff *skb, const struct xflow_key *key)
{
	struct arp_eth_header *arp;

	if (key->dl_type != htons(ETH_P_ARP))
		return false;

	if (skb_network_offset(skb) + sizeof(struct arp_eth_header) > skb->len)
		return true;

	arp = (struct arp_eth_header *)skb_network_header(skb);
	return (arp->ar_hrd != htons(ARPHRD_ETHER) ||
		arp->ar_pro != htons(ETH_P_IP) ||
		arp->ar_hln != ETH_ALEN ||
		arp->ar_pln != 4 ||
		compare_ether_addr(arp->ar_sha, eth_hdr(skb)->h_source));
}

static void do_output(struct datapath *dp, struct sk_buff *skb, int out_port)
{
	struct dp_port *p;

	if (!skb)
		goto error;

	p = rcu_dereference(dp->ports[out_port]);
	if (!p)
		goto error;

	vport_send(p->vport, skb);
	return;

error:
	kfree_skb(skb);
}

/* Never consumes 'skb'.  Returns a port that 'skb' should be sent to, -1 if
 * none.  */
static int output_group(struct datapath *dp, __u16 group,
			struct sk_buff *skb, gfp_t gfp)
{
	struct dp_port_group *g = rcu_dereference(dp->groups[group]);
	int prev_port = -1;
	int i;

	if (!g)
		return -1;
	for (i = 0; i < g->n_ports; i++) {
		struct dp_port *p = rcu_dereference(dp->ports[g->ports[i]]);
		if (!p || OVS_CB(skb)->dp_port == p)
			continue;
		if (prev_port != -1) {
			struct sk_buff *clone = skb_clone(skb, gfp);
			if (!clone)
				return -1;
			do_output(dp, clone, prev_port);
		}
		prev_port = p->port_no;
	}
	return prev_port;
}

static int output_control(struct datapath *dp, struct sk_buff *skb, u32 arg,
			  gfp_t gfp)
{
	skb = skb_clone(skb, gfp);
	if (!skb)
		return -ENOMEM;
	return dp_output_control(dp, skb, _XFLOWL_ACTION_NR, arg);
}

/* Send a copy of this packet up to the sFlow agent, along with extra
 * information about what happened to it. */
static void sflow_sample(struct datapath *dp, struct sk_buff *skb,
			 const union xflow_action *a, int n_actions,
			 gfp_t gfp, struct dp_port *dp_port)
{
	struct xflow_sflow_sample_header *hdr;
	unsigned int actlen = n_actions * sizeof(union xflow_action);
	unsigned int hdrlen = sizeof(struct xflow_sflow_sample_header);
	struct sk_buff *nskb;

	nskb = skb_copy_expand(skb, actlen + hdrlen, 0, gfp);
	if (!nskb)
		return;

	memcpy(__skb_push(nskb, actlen), a, actlen);
	hdr = (struct xflow_sflow_sample_header*)__skb_push(nskb, hdrlen);
	hdr->n_actions = n_actions;
	hdr->sample_pool = atomic_read(&dp_port->sflow_pool);
	dp_output_control(dp, nskb, _XFLOWL_SFLOW_NR, 0);
}

/* Execute a list of actions against 'skb'. */
int execute_actions(struct datapath *dp, struct sk_buff *skb,
		    const struct xflow_key *key,
		    const union xflow_action *a, int n_actions,
		    gfp_t gfp)
{
	/* Every output action needs a separate clone of 'skb', but the common
	 * case is just a single output action, so that doing a clone and
	 * then freeing the original skbuff is wasteful.  So the following code
	 * is slightly obscure just to avoid that. */
	int prev_port = -1;
	u32 priority = skb->priority;
	int err;

	if (dp->sflow_probability) {
		struct dp_port *p = OVS_CB(skb)->dp_port;
		if (p) {
			atomic_inc(&p->sflow_pool);
			if (dp->sflow_probability == UINT_MAX ||
			    net_random() < dp->sflow_probability)
				sflow_sample(dp, skb, a, n_actions, gfp, p);
		}
	}

	OVS_CB(skb)->tun_id = 0;

	for (; n_actions > 0; a++, n_actions--) {
		if (prev_port != -1) {
			do_output(dp, skb_clone(skb, gfp), prev_port);
			prev_port = -1;
		}

		switch (a->type) {
		case XFLOWAT_OUTPUT:
			prev_port = a->output.port;
			break;

		case XFLOWAT_OUTPUT_GROUP:
			prev_port = output_group(dp, a->output_group.group,
						 skb, gfp);
			break;

		case XFLOWAT_CONTROLLER:
			err = output_control(dp, skb, a->controller.arg, gfp);
			if (err) {
				kfree_skb(skb);
				return err;
			}
			break;

		case XFLOWAT_SET_TUNNEL:
			OVS_CB(skb)->tun_id = a->tunnel.tun_id;
			break;

		case XFLOWAT_SET_DL_TCI:
			skb = modify_vlan_tci(dp, skb, key, a, n_actions, gfp);
			if (IS_ERR(skb))
				return PTR_ERR(skb);
			break;

		case XFLOWAT_STRIP_VLAN:
			skb = strip_vlan(skb, gfp);
			break;

		case XFLOWAT_SET_DL_SRC:
		case XFLOWAT_SET_DL_DST:
			skb = set_dl_addr(skb, &a->dl_addr, gfp);
			break;

		case XFLOWAT_SET_NW_SRC:
		case XFLOWAT_SET_NW_DST:
			skb = set_nw_addr(skb, key, &a->nw_addr, gfp);
			break;

		case XFLOWAT_SET_NW_TOS:
			skb = set_nw_tos(skb, key, &a->nw_tos, gfp);
			break;

		case XFLOWAT_SET_TP_SRC:
		case XFLOWAT_SET_TP_DST:
			skb = set_tp_port(skb, key, &a->tp_port, gfp);
			break;

		case XFLOWAT_SET_PRIORITY:
			skb->priority = a->priority.priority;
			break;

		case XFLOWAT_POP_PRIORITY:
			skb->priority = priority;
			break;

		case XFLOWAT_DROP_SPOOFED_ARP:
			if (unlikely(is_spoofed_arp(skb, key)))
				goto exit;
			break;
		}
		if (!skb)
			return -ENOMEM;
	}
exit:
	if (prev_port != -1)
		do_output(dp, skb, prev_port);
	else
		kfree_skb(skb);
	return 0;
}