/*
 * Copyright (c) 2019 AVM GmbH <info@avm.de>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * 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, see <http://www.gnu.org/licenses/>.
 */
#include <avm/pa/avm_pa.h>
#include <avm/pa/avm_pa_hw.h>

#include <linux/if_ether.h>
#include <linux/if_vlan.h>
#include <linux/if_pppox.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/udp.h>
#include <linux/tcp.h>
#include <linux/slab.h>

#include <net/datapath_api.h>
#include <net/ppa/avm_mpe_api.h>
#include <net/ppa/ltq_mpe_api.h>

#include "hwpa.h"
#include "hwpa_prx.h"

/*
 * mpe-se/firmware is not robust against immediate reusage
 * of hw_session memory.
 * MxL proposes udelay(8) in mpe_hal_del_session_ipv{4,6},
 * so our 250ms approach is far more defensive.
 */
#define MPE_GRACE_PERIOD (HZ >> 2)

static struct kmem_cache *kmem;
static struct list_head free_list;
static struct delayed_work free_work;
static DEFINE_SPINLOCK(free_list_lock);

struct hkey {
	enum { HKEY_V4,
	       HKEY_V6,
	} tag;
	union {
		struct ipv4_hash_auto_key v4;
		struct ipv6_hash_auto_key v6;
	};
};

struct session {
	struct hkey key;
	unsigned long entry;
	struct session_mib last_mib;
	u8 templ_buf[AVM_PA_MAX_HEADER];
	struct session_action action;
	struct list_head free_list_node;
	unsigned long erase_time;
};

static enum hwpa_backend_rv extract_key_v6(const struct avm_pa_session *s,
                                           struct ipv6_hash_auto_key *k)
{
	const u16 *ports;
	const struct ipv6hdr *hdr;

	hdr = hwpa_get_hdr(&s->ingress, AVM_PA_IPV6);

	memcpy(&k->srcip, &hdr->saddr, sizeof(k->srcip));
	memcpy(&k->dstip, &hdr->daddr, sizeof(k->dstip));

	ports = hwpa_get_hdr(&s->ingress, AVM_PA_PORTS);
	k->srcport = ports[0];
	k->dstport = ports[1];

	switch (AVM_PA_PKTTYPE_IPPROTO(s->ingress.pkttype)) {
	case IPPROTO_UDP:
	case IPPROTO_UDPLITE:
		k->extn = 1;
		break;
	case IPPROTO_TCP:
		k->extn = 0;
		break;
	default:
		return HWPA_BACKEND_ERR_INTERNAL;
	}

	return HWPA_BACKEND_SUCCESS;
}

static enum hwpa_backend_rv extract_key_v4(const struct avm_pa_session *s,
                                           struct ipv4_hash_auto_key *k)
{
	const u16 *ports;
	const struct iphdr *hdr;

	hdr = hwpa_get_hdr(&s->ingress, AVM_PA_IPV4);

	memcpy(&k->srcip, &hdr->saddr, sizeof(k->srcip));
	memcpy(&k->dstip, &hdr->daddr, sizeof(k->dstip));

	ports = hwpa_get_hdr(&s->ingress, AVM_PA_PORTS);
	k->srcport = ports[0];
	k->dstport = ports[1];

	switch (AVM_PA_PKTTYPE_IPPROTO(s->ingress.pkttype)) {
	case IPPROTO_UDP:
	case IPPROTO_UDPLITE:
		k->extn = 1;
		break;
	case IPPROTO_TCP:
		k->extn = 0;
		break;
	default:
		return HWPA_BACKEND_ERR_INTERNAL;
	}

	return HWPA_BACKEND_SUCCESS;
}

static enum hwpa_backend_rv extract_key(const struct avm_pa_session *s,
                                           struct hkey *k)
{
	enum hwpa_backend_rv rv;

	switch (s->ingress.pkttype & AVM_PA_PKTTYPE_IP_MASK) {
	case AVM_PA_PKTTYPE_IPV6:
		rv = extract_key_v6(s, &k->v6);
		k->tag = HKEY_V6;
		break;
	case AVM_PA_PKTTYPE_IPV4:
		rv = extract_key_v4(s, &k->v4);
		k->tag = HKEY_V4;
		break;
	default:
		rv = HWPA_BACKEND_ERR_INTERNAL;
	}

	return rv;
}

static enum hwpa_backend_rv
        extract_action_pppoe(const struct avm_pa_pkt_match *eg_match,
                             struct session_action *a)
{
	struct pppoe_hdr *pppoe;

	pppoe = (void *)hwpa_get_hdr(eg_match, AVM_PA_PPPOE);
	if (pppoe) {
		/* MPE FW needs to fill the PPPoE template with a valid
		 * length. It does so by adding the amount of bytes it deems
		 * to be the inner packet length to the length contained in
		 * the template. Currently, the inner packet length is the
		 * length of the innermost IP frame.
		 */
		a->pppoe_offset_en = 1;
		a->pppoe_offset = eg_match->pppoe_offset;
		pppoe = (void *)(a->templ_buf + a->pppoe_offset);

		/* read as: inner_ip_offset - (pppoe_offset + pppoe_size)
		 * This is supposed to be the length of the static part of the
		 * PPPoE payload. MPE considers the length of the innermost IP
		 * frame to be variable across a specific flow and adds it
		 * itself for each packet.
		 */
		pppoe->length = eg_match->ip_offset -
		                (eg_match->pppoe_offset +
		                 sizeof(*pppoe));
	}

	return HWPA_BACKEND_SUCCESS;
}

static enum hwpa_backend_rv
extract_action_nat(const struct avm_pa_pkt_match *ig_match,
		   const struct avm_pa_pkt_match *eg_match,
		   struct session_action *a)
{
	const void *addr_snat, *addr_dnat;
	size_t addr_size;
	bool port_snat, port_dnat;

	/* compare UDP/TCP ports and copy translated value */
	{
		const u16 *ig_ports, *eg_ports;
		ig_ports = hwpa_get_hdr(ig_match, AVM_PA_PORTS);
		eg_ports = hwpa_get_hdr(eg_match, AVM_PA_PORTS);

		port_snat = ig_ports[0] != eg_ports[0];
		if (port_snat)
			a->new_src_port = eg_ports[0];

		port_dnat = ig_ports[1] != eg_ports[1];
		if (port_dnat)
			a->new_dst_port = eg_ports[1];

		if (port_snat || port_dnat)
			a->routing_flag = 1;
	}

	/* check for NAT and copy address */
	if ((eg_match->pkttype & AVM_PA_PKTTYPE_IP_MASK) ==
	    AVM_PA_PKTTYPE_IPV6) {
		const struct ipv6hdr *ip6_ig, *ip6_eg;

		//a->eIpType = GSW_RT_IP_V6;

		ip6_ig =
			(struct ipv6hdr *)hwpa_get_hdr(ig_match, (AVM_PA_IPV6));
		ip6_eg =
			(struct ipv6hdr *)hwpa_get_hdr(eg_match, (AVM_PA_IPV6));

		addr_size = sizeof(ip6_ig->daddr);

		addr_dnat = (port_dnat || memcmp(&ip6_ig->daddr, &ip6_eg->daddr,
						 addr_size)) ?
				    &ip6_eg->daddr :
				    NULL;
		addr_snat = (port_snat || memcmp(&ip6_ig->saddr, &ip6_eg->saddr,
						 addr_size)) ?
				    &ip6_eg->saddr :
				    NULL;
	} else {
		const struct iphdr *ip4_ig, *ip4_eg;

		//a->eIpType = GSW_RT_IP_V4;

		ip4_ig = (struct iphdr *)hwpa_get_hdr(ig_match, (AVM_PA_IPV4));
		ip4_eg = (struct iphdr *)hwpa_get_hdr(eg_match, (AVM_PA_IPV4));

		addr_size = sizeof(ip4_ig->daddr);

		addr_dnat = (port_dnat || memcmp(&ip4_ig->daddr, &ip4_eg->daddr,
						 addr_size)) ?
				    &ip4_eg->daddr :
				    NULL;
		addr_snat = (port_snat || memcmp(&ip4_ig->saddr, &ip4_eg->saddr,
						 addr_size)) ?
				    &ip4_eg->saddr :
				    NULL;
	}
	if (addr_dnat) {
		a->new_dst_ip_en = 1;
		memcpy(&a->new_dst_ip, addr_dnat, addr_size);
	}
	if (addr_snat) {
		a->new_src_ip_en = 1;
		memcpy(&a->new_src_ip, addr_snat, addr_size);
	}
	if (addr_snat || addr_dnat) {
	}

	/* TODO using this would be nice */
	//ip4h->tos |= (s_act->new_inner_dscp << 2);

	return HWPA_BACKEND_SUCCESS;
}

/* implementations required by backend */
enum hwpa_backend_rv hwpa_backend_add_session(const struct avm_pa_session *s,
                                              unsigned long *handle_out)
{
	//struct ipv4_hash_auto_key;
	struct session_action *action;
	struct net_device *dev;
	struct net_device *ig_dev;
	const struct avm_pa_egress *eg;
	const struct avm_pa_pkt_match *ig_match, *eg_match;
	enum hwpa_backend_rv rv;
	struct session *hws;
	uint32_t ppa_rv;
	bool is_wlan;
	bool is_vani;
	PPA_SUBIF dp_port = { 0 };

	hws = kmem_cache_alloc(kmem, GFP_KERNEL);
	if (!hws)
		return HWPA_BACKEND_ERR_INTERNAL;

	memset(hws, 0, sizeof(*hws));

	rv = extract_key(s, &hws->key);
	if (rv != HWPA_BACKEND_SUCCESS)
		goto err;

	rv = HWPA_BACKEND_ERR_INTERNAL;

	action = &hws->action;

	eg = avm_pa_first_egress(s);
	ig_match = &s->ingress;
	eg_match = &eg->match;

	ig_dev = hwpa_get_netdev(s->ingress_pid_handle);
	if (!ig_dev)
		goto err;

	dev_put(ig_dev);

	dev = hwpa_get_netdev(eg->pid_handle);

	if (!dev)
		goto err;

	/* for dc-wlan we need to lookup vap and stationId (by destmac), which
	 * is stored in subifid and uc_vap_list[0], respectively */
	if (dp_get_netif_subifid(dev, NULL, NULL,
				 eg->destmac ? eg->destmac->mac : NULL,
				 &dp_port, 0)) {
		dev_put(dev);
		goto err;
	}
	dev_put(dev);

	is_wlan = (dp_port.alloc_flag & DP_F_FAST_WLAN);
	is_vani = (dp_port.alloc_flag & DP_F_VUNI) && (dp_port.data_flag & DP_SUBIF_VANI);

	if (is_vani) {
		PPA_SUBIF dp_port_vuni = { 0 };

		if (dp_get_netif_subifid(dp_port.associate_netif, NULL, NULL, NULL, &dp_port_vuni, 0))
			goto err;

		/* in PON-TX-direction we want to bypass VANI/VUNI bridge, 
		 * thus we are only interested in VUNI parameters
		 * VANI (which is represented by dp_port) is not interesting
		 * for MPE */
		dp_port = dp_port_vuni;

		/* TODO where is the qos index / vap for GPON coming from? */
	}

	action->entry_vld = 1;
	action->redirect = !is_vani;
	action->dst_pmac_port_num = 1;
	action->dst_pmac_port_list[0] = dp_port.port_id;

	action->uc_vap_list[0] = dp_port.subif;

	switch (ig_match->pkttype & AVM_PA_PKTTYPE_IPENCAP_MASK) {
	case AVM_PA_PKTTYPE_IPV4ENCAP:
		action->tunnel_type = TUNL_6RD;
		break;
	case AVM_PA_PKTTYPE_IPV6ENCAP:
		action->tunnel_type = TUNL_DSLITE;
		break;
	default:
		action->tunnel_type = TUNL_NULL;
		break;
	}

	/* GRE key */
	action->key_en = 0;

	/* ipsec tunnel */
	action->tunnel_id = 0;


	action->templ_len = s->mod.push_l2_len + s->mod.push_encap_len;
	if (action->templ_len > sizeof(hws->templ_buf))
		goto err;

	/* Need a local copy of the template for modifications */
	action->templ_buf = hws->templ_buf;
	memcpy(action->templ_buf, HDRCOPY(&s->mod), action->templ_len);

	action->pkt_len_delta = s->mod.push_l2_len - s->mod.pull_l2_len;

	/* decrease ttl */
	action->routing_flag = s->routed;

	action->mtu = eg->mtu + 1;

	extract_action_pppoe(eg_match, action);
	extract_action_nat(ig_match, eg_match, action);

	/* tunnel_rm_en causes MPE FW to remove encapsulation matching the
	 * tunnel type automatically. It does so by determining the equivalent
	 * of pull_encap_len and subtracting it from the delta.
	 * One could either choose to let MPE FW remove encapsulation based on
	 * classification data of the incoming packet, or to make the
	 * adjustment to pkt_len_delta manually. The latter would strip the
	 * same length from any packet matching 5-tuple and tunnel_type.
	 * The manual approach seems less safe. Ignore pull_encap_len and let
	 * MPE FW do its thing.
	 */
	action->tunnel_rm_en = !!s->mod.pull_encap_len;
	action->pkt_len_delta += s->mod.push_encap_len;

	/* activates IPIP
	 * template offset of outer ip
	 */
	action->tunnel_ip_offset_en = !!s->mod.push_encap_len;
	action->tunnel_ip_offset = s->mod.push_l2_len;

	/* template offset of inner ip */
	action->in_eth_iphdr_offset_en = s->mod.push_l2_len + s->mod.push_encap_len;

	/* Structure is IP + UDP + IP */
	action->tunnel_udp_offset_en = !!s->mod.push_udpoffset;
	action->tunnel_udp_offset = s->mod.push_udpoffset;

	if (hws->key.tag == HKEY_V6) {
		ppa_rv = mpe_add_session_v6(&hws->key.v6, action, &hws->entry);
	} else {
		ppa_rv = mpe_add_session_v4(&hws->key.v4, action, &hws->entry);
	}

	if (ppa_rv)
		goto err;

	if (hws->action.sess_mib_ix_en)
		mpe_hal_get_session_mib(hws->key.tag == HKEY_V6,
				action->sess_mib_ix, &hws->last_mib);

	*handle_out = (unsigned long)hws;
	return HWPA_BACKEND_SUCCESS;

err:
	kmem_cache_free(kmem, hws);
	return rv;
}

enum hwpa_backend_rv hwpa_backend_rem_session(unsigned long handle)
{
	struct session *hws;

	hws = (void *)handle;

	/* in case mpe-se-does not read its session_lookup_table immediately
	 * do at least invalidate session-action, so that mpe-firmware will not
	 * apply this action any longer.
	 */
	hws->action.entry_vld = 0;
	mb();

	if (hws->key.tag == HKEY_V4) {
		mpe_del_session_v4(&hws->key.v4, hws->entry);
	} else {
		mpe_del_session_v6(&hws->key.v6, hws->entry);
	}

	/* wait for MPE_GRACE_PERIOD, before we do kmem_cache_free */
	hws->erase_time = jiffies + MPE_GRACE_PERIOD;
	spin_lock(&free_list_lock);
	list_add_tail(&hws->free_list_node, &free_list);
	spin_unlock(&free_list_lock);
	schedule_delayed_work(&free_work, MPE_GRACE_PERIOD);

	return HWPA_BACKEND_SUCCESS;
}


static inline bool
in_grace_period(struct session *hws)
{
      return time_is_after_eq_jiffies(hws->erase_time);
}

static void mpe_free_worker(struct work_struct *work)
{
	struct list_head* pos;
	struct list_head* tmp;

	spin_lock(&free_list_lock);
	list_for_each_safe(pos, tmp, &free_list) {
		struct session *hws = list_entry(pos, struct session, free_list_node);

		if (in_grace_period(hws)){
			schedule_delayed_work(&free_work, hws->erase_time - jiffies);
			spin_unlock(&free_list_lock);
			return;
		}
		list_del(pos);
		kmem_cache_free(kmem, hws);
	}
	spin_unlock(&free_list_lock);
}

enum hwpa_backend_rv hwpa_backend_stats(unsigned long handle,
                                        struct avm_pa_session_stats *stats)
{
	struct session_mib session_mib;
	struct session *hws;

	hws = (void *)handle;
	memset(stats, 0, sizeof(*stats));

	if (!hws->action.sess_mib_ix_en)
		return HWPA_BACKEND_SUCCESS;

	if (mpe_hal_get_session_mib(hws->key.tag == HKEY_V6,
	                            hws->action.sess_mib_ix, &session_mib))
		return HWPA_BACKEND_SUCCESS;

	stats->tx_pkts = session_mib.mib.pkt - hws->last_mib.mib.pkt;
	stats->tx_bytes = session_mib.mib.bytes - hws->last_mib.mib.bytes;

	hws->last_mib = session_mib;

	stats->validflags |=
	        AVM_PA_SESSION_STATS_VALID_BYTES * !!stats->tx_pkts;
	stats->validflags |=
	        AVM_PA_SESSION_STATS_VALID_PKTS * !!stats->tx_bytes;

	return HWPA_BACKEND_SUCCESS;
}

enum hwpa_backend_rv backend_activate_hw(avm_pid_handle pid_handle)
{
	struct net_device *dev = hwpa_get_netdev(pid_handle);

	if (set_mpe_checksum_netdev(dev) != 0)
		return HWPA_BACKEND_SUCCESS;

	return HWPA_BACKEND_ERR_INTERNAL;
}

enum hwpa_backend_rv hwpa_backend_init(void)
{
	kmem = kmem_cache_create("offpa_sess", sizeof(struct session), 0,
	                         SLAB_HWCACHE_ALIGN | SLAB_RED_ZONE, NULL);
	INIT_LIST_HEAD(&free_list);
	INIT_DELAYED_WORK(&free_work, mpe_free_worker);

	return HWPA_BACKEND_SUCCESS;
}

void hwpa_backend_exit(void)
{
	cancel_delayed_work_sync(&free_work);
	kmem_cache_destroy(kmem);
}