/* Copyright 2011-2014 Autronica Fire and Security AS
 *
 * 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.
 *
 * Author(s):
 *      2011-2014 Arvid Brodin, arvid.brodin@alten.se
 *
 * The HSR spec says never to forward the same frame twice on the same
 * interface. A frame is identified by its source MAC address and its HSR
 * sequence number. This code keeps track of senders and their sequence numbers
 * to allow filtering of duplicate frames, and to detect HSR ring errors.
 */

#include <linux/if_ether.h>
#include <linux/etherdevice.h>
#include <linux/slab.h>
#include <linux/rculist.h>
#include "hsr_main.h"
#include "hsr_framereg.h"
#include "hsr_netlink.h"


struct hsr_node {
        struct list_head        mac_list;
        unsigned char           MacAddressA[ETH_ALEN];
        unsigned char           MacAddressB[ETH_ALEN];
        /* Local slave through which AddrB frames are received from this node */
        enum hsr_port_type      AddrB_port;
        unsigned long           time_in[HSR_PT_PORTS];
        bool                    time_in_stale[HSR_PT_PORTS];
        u16                     seq_out[HSR_PT_PORTS];
        struct rcu_head         rcu_head;
};


/*      TODO: use hash lists for mac addresses (linux/jhash.h)?    */


/* seq_nr_after(a, b) - return true if a is after (higher in sequence than) b,
 * false otherwise.
 */
static bool seq_nr_after(u16 a, u16 b)
{
        /* Remove inconsistency where
         * seq_nr_after(a, b) == seq_nr_before(a, b)
         */
        if ((int) b - a == 32768)
                return false;

        return (((s16) (b - a)) < 0);
}
#define seq_nr_before(a, b)             seq_nr_after((b), (a))
#define seq_nr_after_or_eq(a, b)        (!seq_nr_before((a), (b)))
#define seq_nr_before_or_eq(a, b)       (!seq_nr_after((a), (b)))


bool hsr_addr_is_self(struct hsr_priv *hsr, unsigned char *addr)
{
        struct hsr_node *node;

        node = list_first_or_null_rcu(&hsr->self_node_db, struct hsr_node,
                                      mac_list);
        if (!node) {
                WARN_ONCE(1, "HSR: No self node\n");
                return false;
        }

        if (ether_addr_equal(addr, node->MacAddressA))
                return true;
        if (ether_addr_equal(addr, node->MacAddressB))
                return true;

        return false;
}

/* Search for mac entry. Caller must hold rcu read lock.
 */
static struct hsr_node *find_node_by_AddrA(struct list_head *node_db,
                                           const unsigned char addr[ETH_ALEN])
{
        struct hsr_node *node;

        list_for_each_entry_rcu(node, node_db, mac_list) {
                if (ether_addr_equal(node->MacAddressA, addr))
                        return node;
        }

        return NULL;
}


/* Helper for device init; the self_node_db is used in hsr_rcv() to recognize
 * frames from self that's been looped over the HSR ring.
 */
int hsr_create_self_node(struct list_head *self_node_db,
                         unsigned char addr_a[ETH_ALEN],
                         unsigned char addr_b[ETH_ALEN])
{
        struct hsr_node *node, *oldnode;

        node = kmalloc(sizeof(*node), GFP_KERNEL);
        if (!node)
                return -ENOMEM;

        ether_addr_copy(node->MacAddressA, addr_a);
        ether_addr_copy(node->MacAddressB, addr_b);

        rcu_read_lock();
        oldnode = list_first_or_null_rcu(self_node_db,
                                                struct hsr_node, mac_list);
        if (oldnode) {
                list_replace_rcu(&oldnode->mac_list, &node->mac_list);
                rcu_read_unlock();
                synchronize_rcu();
                kfree(oldnode);
        } else {
                rcu_read_unlock();
                list_add_tail_rcu(&node->mac_list, self_node_db);
        }

        return 0;
}


/* Allocate an hsr_node and add it to node_db. 'addr' is the node's AddressA;
 * seq_out is used to initialize filtering of outgoing duplicate frames
 * originating from the newly added node.
 */
struct hsr_node *hsr_add_node(struct list_head *node_db, unsigned char addr[],
                              u16 seq_out)
{
        struct hsr_node *node;
        unsigned long now;
        int i;

        node = kzalloc(sizeof(*node), GFP_ATOMIC);
        if (!node)
                return NULL;

        ether_addr_copy(node->MacAddressA, addr);

        /* We are only interested in time diffs here, so use current jiffies
         * as initialization. (0 could trigger an spurious ring error warning).
         */
        now = jiffies;
        for (i = 0; i < HSR_PT_PORTS; i++)
                node->time_in[i] = now;
        for (i = 0; i < HSR_PT_PORTS; i++)
                node->seq_out[i] = seq_out;

        list_add_tail_rcu(&node->mac_list, node_db);

        return node;
}

/* Get the hsr_node from which 'skb' was sent.
 */
struct hsr_node *hsr_get_node(struct list_head *node_db, struct sk_buff *skb,
                              bool is_sup)
{
        struct hsr_node *node;
        struct ethhdr *ethhdr;
        u16 seq_out;

        if (!skb_mac_header_was_set(skb))
                return NULL;

        ethhdr = (struct ethhdr *) skb_mac_header(skb);

        list_for_each_entry_rcu(node, node_db, mac_list) {
                if (ether_addr_equal(node->MacAddressA, ethhdr->h_source))
                        return node;
                if (ether_addr_equal(node->MacAddressB, ethhdr->h_source))
                        return node;
        }

        if (!is_sup)
                return NULL; /* Only supervision frame may create node entry */

        if (ethhdr->h_proto == htons(ETH_P_PRP)) {
                /* Use the existing sequence_nr from the tag as starting point
                 * for filtering duplicate frames.
                 */
                seq_out = hsr_get_skb_sequence_nr(skb) - 1;
        } else {
                WARN_ONCE(1, "%s: Non-HSR frame\n", __func__);
                seq_out = 0;
        }

        return hsr_add_node(node_db, ethhdr->h_source, seq_out);
}

/* Use the Supervision frame's info about an eventual MacAddressB for merging
 * nodes that has previously had their MacAddressB registered as a separate
 * node.
 */
void hsr_handle_sup_frame(struct sk_buff *skb, struct hsr_node *node_curr,
                          struct hsr_port *port_rcv)
{
        struct hsr_node *node_real;
        struct hsr_sup_payload *hsr_sp;
        struct list_head *node_db;
        int i;

        skb_pull(skb, sizeof(struct hsr_ethhdr_sp));
        hsr_sp = (struct hsr_sup_payload *) skb->data;

        if (ether_addr_equal(eth_hdr(skb)->h_source, hsr_sp->MacAddressA))
                /* Not sent from MacAddressB of a PICS_SUBS capable node */
                goto done;

        /* Merge node_curr (registered on MacAddressB) into node_real */
        node_db = &port_rcv->hsr->node_db;
        node_real = find_node_by_AddrA(node_db, hsr_sp->MacAddressA);
        if (!node_real)
                /* No frame received from AddrA of this node yet */
                node_real = hsr_add_node(node_db, hsr_sp->MacAddressA,
                                         HSR_SEQNR_START - 1);
        if (!node_real)
                goto done; /* No mem */
        if (node_real == node_curr)
                /* Node has already been merged */
                goto done;

        ether_addr_copy(node_real->MacAddressB, eth_hdr(skb)->h_source);
        for (i = 0; i < HSR_PT_PORTS; i++) {
                if (!node_curr->time_in_stale[i] &&
                    time_after(node_curr->time_in[i], node_real->time_in[i])) {
                        node_real->time_in[i] = node_curr->time_in[i];
                        node_real->time_in_stale[i] = node_curr->time_in_stale[i];
                }
                if (seq_nr_after(node_curr->seq_out[i], node_real->seq_out[i]))
                        node_real->seq_out[i] = node_curr->seq_out[i];
        }
        node_real->AddrB_port = port_rcv->type;

        list_del_rcu(&node_curr->mac_list);
        kfree_rcu(node_curr, rcu_head);

done:
        skb_push(skb, sizeof(struct hsr_ethhdr_sp));
}


/* 'skb' is a frame meant for this host, that is to be passed to upper layers.
 *
 * If the frame was sent by a node's B interface, replace the source
 * address with that node's "official" address (MacAddressA) so that upper
 * layers recognize where it came from.
 */
void hsr_addr_subst_source(struct hsr_node *node, struct sk_buff *skb)
{
        if (!skb_mac_header_was_set(skb)) {
                WARN_ONCE(1, "%s: Mac header not set\n", __func__);
                return;
        }

        memcpy(&eth_hdr(skb)->h_source, node->MacAddressA, ETH_ALEN);
}

/* 'skb' is a frame meant for another host.
 * 'port' is the outgoing interface
 *
 * Substitute the target (dest) MAC address if necessary, so the it matches the
 * recipient interface MAC address, regardless of whether that is the
 * recipient's A or B interface.
 * This is needed to keep the packets flowing through switches that learn on
 * which "side" the different interfaces are.
 */
void hsr_addr_subst_dest(struct hsr_node *node_src, struct sk_buff *skb,
                         struct hsr_port *port)
{
        struct hsr_node *node_dst;

        if (!skb_mac_header_was_set(skb)) {
                WARN_ONCE(1, "%s: Mac header not set\n", __func__);
                return;
        }

        if (!is_unicast_ether_addr(eth_hdr(skb)->h_dest))
                return;

        node_dst = find_node_by_AddrA(&port->hsr->node_db, eth_hdr(skb)->h_dest);
        if (!node_dst) {
                WARN_ONCE(1, "%s: Unknown node\n", __func__);
                return;
        }
        if (port->type != node_dst->AddrB_port)
                return;

        ether_addr_copy(eth_hdr(skb)->h_dest, node_dst->MacAddressB);
}


void hsr_register_frame_in(struct hsr_node *node, struct hsr_port *port,
                           u16 sequence_nr)
{
        /* Don't register incoming frames without a valid sequence number. This
         * ensures entries of restarted nodes gets pruned so that they can
         * re-register and resume communications.
         */
        if (seq_nr_before(sequence_nr, node->seq_out[port->type]))
                return;

        node->time_in[port->type] = jiffies;
        node->time_in_stale[port->type] = false;
}

/* 'skb' is a HSR Ethernet frame (with a HSR tag inserted), with a valid
 * ethhdr->h_source address and skb->mac_header set.
 *
 * Return:
 *       1 if frame can be shown to have been sent recently on this interface,
 *       0 otherwise, or
 *       negative error code on error
 */
int hsr_register_frame_out(struct hsr_port *port, struct hsr_node *node,
                           u16 sequence_nr)
{
        if (seq_nr_before_or_eq(sequence_nr, node->seq_out[port->type]))
                return 1;

        node->seq_out[port->type] = sequence_nr;
        return 0;
}


static struct hsr_port *get_late_port(struct hsr_priv *hsr,
                                      struct hsr_node *node)
{
        if (node->time_in_stale[HSR_PT_SLAVE_A])
                return hsr_port_get_hsr(hsr, HSR_PT_SLAVE_A);
        if (node->time_in_stale[HSR_PT_SLAVE_B])
                return hsr_port_get_hsr(hsr, HSR_PT_SLAVE_B);

        if (time_after(node->time_in[HSR_PT_SLAVE_B],
                       node->time_in[HSR_PT_SLAVE_A] +
                                        msecs_to_jiffies(MAX_SLAVE_DIFF)))
                return hsr_port_get_hsr(hsr, HSR_PT_SLAVE_A);
        if (time_after(node->time_in[HSR_PT_SLAVE_A],
                       node->time_in[HSR_PT_SLAVE_B] +
                                        msecs_to_jiffies(MAX_SLAVE_DIFF)))
                return hsr_port_get_hsr(hsr, HSR_PT_SLAVE_B);

        return NULL;
}


/* Remove stale sequence_nr records. Called by timer every
 * HSR_LIFE_CHECK_INTERVAL (two seconds or so).
 */
void hsr_prune_nodes(unsigned long data)
{
        struct hsr_priv *hsr;
        struct hsr_node *node;
        struct hsr_port *port;
        unsigned long timestamp;
        unsigned long time_a, time_b;

        hsr = (struct hsr_priv *) data;

        rcu_read_lock();
        list_for_each_entry_rcu(node, &hsr->node_db, mac_list) {
                /* Shorthand */
                time_a = node->time_in[HSR_PT_SLAVE_A];
                time_b = node->time_in[HSR_PT_SLAVE_B];

                /* Check for timestamps old enough to risk wrap-around */
                if (time_after(jiffies, time_a + MAX_JIFFY_OFFSET/2))
                        node->time_in_stale[HSR_PT_SLAVE_A] = true;
                if (time_after(jiffies, time_b + MAX_JIFFY_OFFSET/2))
                        node->time_in_stale[HSR_PT_SLAVE_B] = true;

                /* Get age of newest frame from node.
                 * At least one time_in is OK here; nodes get pruned long
                 * before both time_ins can get stale
                 */
                timestamp = time_a;
                if (node->time_in_stale[HSR_PT_SLAVE_A] ||
                    (!node->time_in_stale[HSR_PT_SLAVE_B] &&
                    time_after(time_b, time_a)))
                        timestamp = time_b;

                /* Warn of ring error only as long as we get frames at all */
                if (time_is_after_jiffies(timestamp +
                                        msecs_to_jiffies(1.5*MAX_SLAVE_DIFF))) {
                        rcu_read_lock();
                        port = get_late_port(hsr, node);
                        if (port != NULL)
                                hsr_nl_ringerror(hsr, node->MacAddressA, port);
                        rcu_read_unlock();
                }

                /* Prune old entries */
                if (time_is_before_jiffies(timestamp +
                                        msecs_to_jiffies(HSR_NODE_FORGET_TIME))) {
                        hsr_nl_nodedown(hsr, node->MacAddressA);
                        list_del_rcu(&node->mac_list);
                        /* Note that we need to free this entry later: */
                        kfree_rcu(node, rcu_head);
                }
        }
        rcu_read_unlock();
}


void *hsr_get_next_node(struct hsr_priv *hsr, void *_pos,
                        unsigned char addr[ETH_ALEN])
{
        struct hsr_node *node;

        if (!_pos) {
                node = list_first_or_null_rcu(&hsr->node_db,
                                              struct hsr_node, mac_list);
                if (node)
                        ether_addr_copy(addr, node->MacAddressA);
                return node;
        }

        node = _pos;
        list_for_each_entry_continue_rcu(node, &hsr->node_db, mac_list) {
                ether_addr_copy(addr, node->MacAddressA);
                return node;
        }

        return NULL;
}


int hsr_get_node_data(struct hsr_priv *hsr,
                      const unsigned char *addr,
                      unsigned char addr_b[ETH_ALEN],
                      unsigned int *addr_b_ifindex,
                      int *if1_age,
                      u16 *if1_seq,
                      int *if2_age,
                      u16 *if2_seq)
{
        struct hsr_node *node;
        struct hsr_port *port;
        unsigned long tdiff;


        rcu_read_lock();
        node = find_node_by_AddrA(&hsr->node_db, addr);
        if (!node) {
                rcu_read_unlock();
                return -ENOENT; /* No such entry */
        }

        ether_addr_copy(addr_b, node->MacAddressB);

        tdiff = jiffies - node->time_in[HSR_PT_SLAVE_A];
        if (node->time_in_stale[HSR_PT_SLAVE_A])
                *if1_age = INT_MAX;
#if HZ <= MSEC_PER_SEC
        else if (tdiff > msecs_to_jiffies(INT_MAX))
                *if1_age = INT_MAX;
#endif
        else
                *if1_age = jiffies_to_msecs(tdiff);

        tdiff = jiffies - node->time_in[HSR_PT_SLAVE_B];
        if (node->time_in_stale[HSR_PT_SLAVE_B])
                *if2_age = INT_MAX;
#if HZ <= MSEC_PER_SEC
        else if (tdiff > msecs_to_jiffies(INT_MAX))
                *if2_age = INT_MAX;
#endif
        else
                *if2_age = jiffies_to_msecs(tdiff);

        /* Present sequence numbers as if they were incoming on interface */
        *if1_seq = node->seq_out[HSR_PT_SLAVE_B];
        *if2_seq = node->seq_out[HSR_PT_SLAVE_A];

        if (node->AddrB_port != HSR_PT_NONE) {
                port = hsr_port_get_hsr(hsr, node->AddrB_port);
                *addr_b_ifindex = port->dev->ifindex;
        } else {
                *addr_b_ifindex = -1;
        }

        rcu_read_unlock();

        return 0;
}