// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      Spanning tree protocol; interface code
 *      Linux ethernet bridge
 *
 *      Authors:
 *      Lennert Buytenhek               <buytenh@gnu.org>
 */

#include <linux/kernel.h>
#include <linux/kmod.h>
#include <linux/etherdevice.h>
#include <linux/rtnetlink.h>
#include <net/switchdev.h>

#include "br_private.h"
#include "br_private_stp.h"


/* Port id is composed of priority and port number.
 * NB: some bits of priority are dropped to
 *     make room for more ports.
 */
static inline port_id br_make_port_id(__u8 priority, __u16 port_no)
{
        return ((u16)priority << BR_PORT_BITS)
                | (port_no & ((1<<BR_PORT_BITS)-1));
}

#define BR_MAX_PORT_PRIORITY ((u16)~0 >> BR_PORT_BITS)

/* called under bridge lock */
void br_init_port(struct net_bridge_port *p)
{
        int err;

        p->port_id = br_make_port_id(p->priority, p->port_no);
        br_become_designated_port(p);
        br_set_state(p, BR_STATE_BLOCKING);
        p->topology_change_ack = 0;
        p->config_pending = 0;

        err = __set_ageing_time(p->dev, p->br->ageing_time);
        if (err)
                netdev_err(p->dev, "failed to offload ageing time\n");
}

/* NO locks held */
void br_stp_enable_bridge(struct net_bridge *br)
{
        struct net_bridge_port *p;

        spin_lock_bh(&br->lock);
        if (br->stp_enabled == BR_KERNEL_STP)
                mod_timer(&br->hello_timer, jiffies + br->hello_time);
        mod_delayed_work(system_long_wq, &br->gc_work, HZ / 10);

        br_config_bpdu_generation(br);

        list_for_each_entry(p, &br->port_list, list) {
                if (netif_running(p->dev) && netif_oper_up(p->dev))
                        br_stp_enable_port(p);

        }
        spin_unlock_bh(&br->lock);
}

/* NO locks held */
void br_stp_disable_bridge(struct net_bridge *br)
{
        struct net_bridge_port *p;

        spin_lock_bh(&br->lock);
        list_for_each_entry(p, &br->port_list, list) {
                if (p->state != BR_STATE_DISABLED)
                        br_stp_disable_port(p);

        }

        __br_set_topology_change(br, 0);
        br->topology_change_detected = 0;
        spin_unlock_bh(&br->lock);

        timer_delete_sync(&br->hello_timer);
        timer_delete_sync(&br->topology_change_timer);
        timer_delete_sync(&br->tcn_timer);
        cancel_delayed_work_sync(&br->gc_work);
}

/* called under bridge lock */
void br_stp_enable_port(struct net_bridge_port *p)
{
        br_init_port(p);
        br_port_state_selection(p->br);
        br_ifinfo_notify(RTM_NEWLINK, NULL, p);
}

/* called under bridge lock */
void br_stp_disable_port(struct net_bridge_port *p)
{
        struct net_bridge *br = p->br;
        int wasroot;

        wasroot = br_is_root_bridge(br);
        br_become_designated_port(p);
        br_set_state(p, BR_STATE_DISABLED);
        p->topology_change_ack = 0;
        p->config_pending = 0;

        br_ifinfo_notify(RTM_NEWLINK, NULL, p);

        timer_delete(&p->message_age_timer);
        timer_delete(&p->forward_delay_timer);
        timer_delete(&p->hold_timer);

        if (!rcu_access_pointer(p->backup_port))
                br_fdb_delete_by_port(br, p, 0, 0);
        br_multicast_disable_port(p);

        br_configuration_update(br);

        br_port_state_selection(br);

        if (br_is_root_bridge(br) && !wasroot)
                br_become_root_bridge(br);
}

static int br_stp_call_user(struct net_bridge *br, char *arg)
{
        char *argv[] = { BR_STP_PROG, br->dev->name, arg, NULL };
        char *envp[] = { NULL };
        int rc;

        /* call userspace STP and report program errors */
        rc = call_usermodehelper(BR_STP_PROG, argv, envp, UMH_WAIT_PROC);
        if (rc > 0) {
                if (rc & 0xff)
                        br_debug(br, BR_STP_PROG " received signal %d\n",
                                 rc & 0x7f);
                else
                        br_debug(br, BR_STP_PROG " exited with code %d\n",
                                 (rc >> 8) & 0xff);
        }

        return rc;
}

static void br_stp_start(struct net_bridge *br)
{
        int err = -ENOENT;

        if (net_eq(dev_net(br->dev), &init_net))
                err = br_stp_call_user(br, "start");

        if (err && err != -ENOENT)
                br_err(br, "failed to start userspace STP (%d)\n", err);

        spin_lock_bh(&br->lock);

        if (br->bridge_forward_delay < BR_MIN_FORWARD_DELAY)
                __br_set_forward_delay(br, BR_MIN_FORWARD_DELAY);
        else if (br->bridge_forward_delay > BR_MAX_FORWARD_DELAY)
                __br_set_forward_delay(br, BR_MAX_FORWARD_DELAY);

        if (!err) {
                br->stp_enabled = BR_USER_STP;
                br_debug(br, "userspace STP started\n");
        } else {
                br->stp_enabled = BR_KERNEL_STP;
                br_debug(br, "using kernel STP\n");

                /* To start timers on any ports left in blocking */
                if (br->dev->flags & IFF_UP)
                        mod_timer(&br->hello_timer, jiffies + br->hello_time);
                br_port_state_selection(br);
        }

        spin_unlock_bh(&br->lock);
}

static void br_stp_stop(struct net_bridge *br)
{
        int err;

        if (br->stp_enabled == BR_USER_STP) {
                err = br_stp_call_user(br, "stop");
                if (err)
                        br_err(br, "failed to stop userspace STP (%d)\n", err);

                /* To start timers on any ports left in blocking */
                spin_lock_bh(&br->lock);
                br_port_state_selection(br);
                spin_unlock_bh(&br->lock);
        }

        br->stp_enabled = BR_NO_STP;
}

int br_stp_set_enabled(struct net_bridge *br, unsigned long val,
                       struct netlink_ext_ack *extack)
{
        ASSERT_RTNL();

        if (br_mrp_enabled(br)) {
                NL_SET_ERR_MSG_MOD(extack,
                                   "STP can't be enabled if MRP is already enabled");
                return -EINVAL;
        }

        if (val) {
                if (br->stp_enabled == BR_NO_STP)
                        br_stp_start(br);
        } else {
                if (br->stp_enabled != BR_NO_STP)
                        br_stp_stop(br);
        }

        return 0;
}

/* called under bridge lock */
void br_stp_change_bridge_id(struct net_bridge *br, const unsigned char *addr)
{
        /* should be aligned on 2 bytes for ether_addr_equal() */
        unsigned short oldaddr_aligned[ETH_ALEN >> 1];
        unsigned char *oldaddr = (unsigned char *)oldaddr_aligned;
        struct net_bridge_port *p;
        int wasroot;

        wasroot = br_is_root_bridge(br);

        br_fdb_change_mac_address(br, addr);

        memcpy(oldaddr, br->bridge_id.addr, ETH_ALEN);
        memcpy(br->bridge_id.addr, addr, ETH_ALEN);
        eth_hw_addr_set(br->dev, addr);

        list_for_each_entry(p, &br->port_list, list) {
                if (ether_addr_equal(p->designated_bridge.addr, oldaddr))
                        memcpy(p->designated_bridge.addr, addr, ETH_ALEN);

                if (ether_addr_equal(p->designated_root.addr, oldaddr))
                        memcpy(p->designated_root.addr, addr, ETH_ALEN);
        }

        br_configuration_update(br);
        br_port_state_selection(br);
        if (br_is_root_bridge(br) && !wasroot)
                br_become_root_bridge(br);
}

/* should be aligned on 2 bytes for ether_addr_equal() */
static const unsigned short br_mac_zero_aligned[ETH_ALEN >> 1];

/* called under bridge lock */
bool br_stp_recalculate_bridge_id(struct net_bridge *br)
{
        const unsigned char *br_mac_zero =
                        (const unsigned char *)br_mac_zero_aligned;
        const unsigned char *addr = br_mac_zero;
        struct net_bridge_port *p;

        /* user has chosen a value so keep it */
        if (br->dev->addr_assign_type == NET_ADDR_SET)
                return false;

        list_for_each_entry(p, &br->port_list, list) {
                if (addr == br_mac_zero ||
                    memcmp(p->dev->dev_addr, addr, ETH_ALEN) < 0)
                        addr = p->dev->dev_addr;

        }

        if (ether_addr_equal(br->bridge_id.addr, addr))
                return false;   /* no change */

        br_stp_change_bridge_id(br, addr);
        return true;
}

/* Acquires and releases bridge lock */
void br_stp_set_bridge_priority(struct net_bridge *br, u16 newprio)
{
        struct net_bridge_port *p;
        int wasroot;

        spin_lock_bh(&br->lock);
        wasroot = br_is_root_bridge(br);

        list_for_each_entry(p, &br->port_list, list) {
                if (p->state != BR_STATE_DISABLED &&
                    br_is_designated_port(p)) {
                        p->designated_bridge.prio[0] = (newprio >> 8) & 0xFF;
                        p->designated_bridge.prio[1] = newprio & 0xFF;
                }

        }

        br->bridge_id.prio[0] = (newprio >> 8) & 0xFF;
        br->bridge_id.prio[1] = newprio & 0xFF;
        br_configuration_update(br);
        br_port_state_selection(br);
        if (br_is_root_bridge(br) && !wasroot)
                br_become_root_bridge(br);
        spin_unlock_bh(&br->lock);
}

/* called under bridge lock */
int br_stp_set_port_priority(struct net_bridge_port *p, unsigned long newprio)
{
        port_id new_port_id;

        if (newprio > BR_MAX_PORT_PRIORITY)
                return -ERANGE;

        new_port_id = br_make_port_id(newprio, p->port_no);
        if (br_is_designated_port(p))
                p->designated_port = new_port_id;

        p->port_id = new_port_id;
        p->priority = newprio;
        if (!memcmp(&p->br->bridge_id, &p->designated_bridge, 8) &&
            p->port_id < p->designated_port) {
                br_become_designated_port(p);
                br_port_state_selection(p->br);
        }

        return 0;
}

/* called under bridge lock */
int br_stp_set_path_cost(struct net_bridge_port *p, unsigned long path_cost)
{
        if (path_cost < BR_MIN_PATH_COST ||
            path_cost > BR_MAX_PATH_COST)
                return -ERANGE;

        p->flags |= BR_ADMIN_COST;
        p->path_cost = path_cost;
        br_configuration_update(p->br);
        br_port_state_selection(p->br);
        return 0;
}

ssize_t br_show_bridge_id(char *buf, const struct bridge_id *id)
{
        return sysfs_emit(buf, "%.2x%.2x.%.2x%.2x%.2x%.2x%.2x%.2x\n",
                          id->prio[0], id->prio[1],
                          id->addr[0], id->addr[1], id->addr[2],
                          id->addr[3], id->addr[4], id->addr[5]);
}