// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      Handle incoming frames
 *      Linux ethernet bridge
 *
 *      Authors:
 *      Lennert Buytenhek               <buytenh@gnu.org>
 */

#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/netfilter_bridge.h>
#ifdef CONFIG_NETFILTER_FAMILY_BRIDGE
#include <net/netfilter/nf_queue.h>
#endif
#include <linux/neighbour.h>
#include <net/arp.h>
#include <net/dsa.h>
#include <linux/export.h>
#include <linux/rculist.h>
#include "br_private.h"
#include "br_private_tunnel.h"

static int
br_netif_receive_skb(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        br_drop_fake_rtable(skb);
        return netif_receive_skb(skb);
}

static int br_pass_frame_up(struct sk_buff *skb, bool promisc)
{
        struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
        struct net_bridge *br = netdev_priv(brdev);
        struct net_bridge_vlan_group *vg;

        dev_sw_netstats_rx_add(brdev, skb->len);

        vg = br_vlan_group_rcu(br);

        /* Reset the offload_fwd_mark because there could be a stacked
         * bridge above, and it should not think this bridge it doing
         * that bridge's work forwarding out its ports.
         */
        br_switchdev_frame_unmark(skb);

        /* Bridge is just like any other port.  Make sure the
         * packet is allowed except in promisc mode when someone
         * may be running packet capture.
         */
        if (!(brdev->flags & IFF_PROMISC) &&
            !br_allowed_egress(vg, skb)) {
                kfree_skb(skb);
                return NET_RX_DROP;
        }

        indev = skb->dev;
        skb->dev = brdev;
        skb = br_handle_vlan(br, NULL, vg, skb);
        if (!skb)
                return NET_RX_DROP;
        /* update the multicast stats if the packet is IGMP/MLD */
        br_multicast_count(br, NULL, skb, br_multicast_igmp_type(skb),
                           BR_MCAST_DIR_TX);

        BR_INPUT_SKB_CB(skb)->promisc = promisc;

        return NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN,
                       dev_net(indev), NULL, skb, indev, NULL,
                       br_netif_receive_skb);
}

/* note: already called with rcu_read_lock */
int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
        struct net_bridge_port *p = br_port_get_rcu(skb->dev);
        enum br_pkt_type pkt_type = BR_PKT_UNICAST;
        struct net_bridge_fdb_entry *dst = NULL;
        struct net_bridge_mcast_port *pmctx;
        struct net_bridge_mdb_entry *mdst;
        bool local_rcv, mcast_hit = false;
        struct net_bridge_mcast *brmctx;
        struct net_bridge_vlan *vlan;
        struct net_bridge *br;
        bool promisc;
        u16 vid = 0;
        u8 state;

        if (!p)
                goto drop;

        br = p->br;

        if (br_mst_is_enabled(p)) {
                state = BR_STATE_FORWARDING;
        } else {
                if (p->state == BR_STATE_DISABLED) {
                        reason = SKB_DROP_REASON_BRIDGE_INGRESS_STP_STATE;
                        goto drop;
                }

                state = p->state;
        }

        brmctx = &p->br->multicast_ctx;
        pmctx = &p->multicast_ctx;
        if (!br_allowed_ingress(p->br, nbp_vlan_group_rcu(p), skb, &vid,
                                &state, &vlan))
                goto out;

        if (p->flags & BR_PORT_LOCKED) {
                struct net_bridge_fdb_entry *fdb_src =
                        br_fdb_find_rcu(br, eth_hdr(skb)->h_source, vid);

                if (!fdb_src) {
                        /* FDB miss. Create locked FDB entry if MAB is enabled
                         * and drop the packet.
                         */
                        if (p->flags & BR_PORT_MAB)
                                br_fdb_update(br, p, eth_hdr(skb)->h_source,
                                              vid, BIT(BR_FDB_LOCKED));
                        goto drop;
                } else if (READ_ONCE(fdb_src->dst) != p ||
                           test_bit(BR_FDB_LOCAL, &fdb_src->flags)) {
                        /* FDB mismatch. Drop the packet without roaming. */
                        goto drop;
                } else if (test_bit(BR_FDB_LOCKED, &fdb_src->flags)) {
                        /* FDB match, but entry is locked. Refresh it and drop
                         * the packet.
                         */
                        br_fdb_update(br, p, eth_hdr(skb)->h_source, vid,
                                      BIT(BR_FDB_LOCKED));
                        goto drop;
                }
        }

        nbp_switchdev_frame_mark(p, skb);

        /* insert into forwarding database after filtering to avoid spoofing */
        if (p->flags & BR_LEARNING)
                br_fdb_update(br, p, eth_hdr(skb)->h_source, vid, 0);

        promisc = !!(br->dev->flags & IFF_PROMISC);
        local_rcv = promisc;

        if (is_multicast_ether_addr(eth_hdr(skb)->h_dest)) {
                /* by definition the broadcast is also a multicast address */
                if (is_broadcast_ether_addr(eth_hdr(skb)->h_dest)) {
                        pkt_type = BR_PKT_BROADCAST;
                        local_rcv = true;
                } else {
                        pkt_type = BR_PKT_MULTICAST;
                        if (br_multicast_rcv(&brmctx, &pmctx, vlan, skb, vid))
                                goto drop;
                }
        }

        if (state == BR_STATE_LEARNING) {
                reason = SKB_DROP_REASON_BRIDGE_INGRESS_STP_STATE;
                goto drop;
        }

        BR_INPUT_SKB_CB(skb)->brdev = br->dev;
        BR_INPUT_SKB_CB(skb)->src_port_isolated = !!(p->flags & BR_ISOLATED);

        if (IS_ENABLED(CONFIG_INET) &&
            (skb->protocol == htons(ETH_P_ARP) ||
             skb->protocol == htons(ETH_P_RARP))) {
                br_do_proxy_suppress_arp(skb, br, vid, p);
        } else if (ipv6_mod_enabled() &&
                   skb->protocol == htons(ETH_P_IPV6) &&
                   br_opt_get(br, BROPT_NEIGH_SUPPRESS_ENABLED) &&
                   pskb_may_pull(skb, sizeof(struct ipv6hdr) +
                                 sizeof(struct nd_msg)) &&
                   ipv6_hdr(skb)->nexthdr == IPPROTO_ICMPV6) {
                        struct nd_msg *msg, _msg;

                        msg = br_is_nd_neigh_msg(skb, &_msg);
                        if (msg)
                                br_do_suppress_nd(skb, br, vid, p, msg);
        }

        switch (pkt_type) {
        case BR_PKT_MULTICAST:
                mdst = br_mdb_entry_skb_get(brmctx, skb, vid);
                if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
                    br_multicast_querier_exists(brmctx, eth_hdr(skb), mdst)) {
                        if ((mdst && mdst->host_joined) ||
                            br_multicast_is_router(brmctx, skb) ||
                            br->dev->flags & IFF_ALLMULTI) {
                                local_rcv = true;
                                DEV_STATS_INC(br->dev, multicast);
                        }
                        mcast_hit = true;
                } else {
                        local_rcv = true;
                        DEV_STATS_INC(br->dev, multicast);
                }
                break;
        case BR_PKT_UNICAST:
                dst = br_fdb_find_rcu(br, eth_hdr(skb)->h_dest, vid);
                if (unlikely(!dst && vid &&
                             br_opt_get(br, BROPT_FDB_LOCAL_VLAN_0))) {
                        dst = br_fdb_find_rcu(br, eth_hdr(skb)->h_dest, 0);
                        if (dst &&
                            (!test_bit(BR_FDB_LOCAL, &dst->flags) ||
                             test_bit(BR_FDB_ADDED_BY_USER, &dst->flags)))
                                dst = NULL;
                }
                break;
        default:
                break;
        }

        if (dst) {
                unsigned long now = jiffies;

                if (test_bit(BR_FDB_LOCAL, &dst->flags))
                        return br_pass_frame_up(skb, false);

                if (now != READ_ONCE(dst->used))
                        WRITE_ONCE(dst->used, now);
                br_forward(dst->dst, skb, local_rcv, false);
        } else {
                if (!mcast_hit)
                        br_flood(br, skb, pkt_type, local_rcv, false, vid);
                else
                        br_multicast_flood(mdst, skb, brmctx, local_rcv, false);
        }

        if (local_rcv)
                return br_pass_frame_up(skb, promisc);

out:
        return 0;
drop:
        kfree_skb_reason(skb, reason);
        goto out;
}
EXPORT_SYMBOL_GPL(br_handle_frame_finish);

static void __br_handle_local_finish(struct sk_buff *skb)
{
        struct net_bridge_port *p = br_port_get_rcu(skb->dev);
        u16 vid = 0;

        /* check if vlan is allowed, to avoid spoofing */
        if ((p->flags & BR_LEARNING) &&
            nbp_state_should_learn(p) &&
            !br_opt_get(p->br, BROPT_NO_LL_LEARN) &&
            br_should_learn(p, skb, &vid))
                br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid, 0);
}

/* note: already called with rcu_read_lock */
static int br_handle_local_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        __br_handle_local_finish(skb);

        /* return 1 to signal the okfn() was called so it's ok to use the skb */
        return 1;
}

static int nf_hook_bridge_pre(struct sk_buff *skb, struct sk_buff **pskb)
{
#ifdef CONFIG_NETFILTER_FAMILY_BRIDGE
        struct nf_hook_entries *e = NULL;
        struct nf_hook_state state;
        unsigned int verdict, i;
        struct net *net;
        int ret;

        net = dev_net(skb->dev);
#ifdef CONFIG_JUMP_LABEL
        if (!static_key_false(&nf_hooks_needed[NFPROTO_BRIDGE][NF_BR_PRE_ROUTING]))
                goto frame_finish;
#endif

        e = rcu_dereference(net->nf.hooks_bridge[NF_BR_PRE_ROUTING]);
        if (!e)
                goto frame_finish;

        nf_hook_state_init(&state, NF_BR_PRE_ROUTING,
                           NFPROTO_BRIDGE, skb->dev, NULL, NULL,
                           net, br_handle_frame_finish);

        for (i = 0; i < e->num_hook_entries; i++) {
                verdict = nf_hook_entry_hookfn(&e->hooks[i], skb, &state);
                switch (verdict & NF_VERDICT_MASK) {
                case NF_ACCEPT:
                        if (BR_INPUT_SKB_CB(skb)->br_netfilter_broute) {
                                *pskb = skb;
                                return RX_HANDLER_PASS;
                        }
                        break;
                case NF_DROP:
                        kfree_skb(skb);
                        return RX_HANDLER_CONSUMED;
                case NF_QUEUE:
                        ret = nf_queue(skb, &state, i, verdict);
                        if (ret == 1)
                                continue;
                        return RX_HANDLER_CONSUMED;
                default: /* STOLEN */
                        return RX_HANDLER_CONSUMED;
                }
        }
frame_finish:
        net = dev_net(skb->dev);
        br_handle_frame_finish(net, NULL, skb);
#else
        br_handle_frame_finish(dev_net(skb->dev), NULL, skb);
#endif
        return RX_HANDLER_CONSUMED;
}

/* Return 0 if the frame was not processed otherwise 1
 * note: already called with rcu_read_lock
 */
static int br_process_frame_type(struct net_bridge_port *p,
                                 struct sk_buff *skb)
{
        struct br_frame_type *tmp;

        hlist_for_each_entry_rcu(tmp, &p->br->frame_type_list, list)
                if (unlikely(tmp->type == skb->protocol))
                        return tmp->frame_handler(p, skb);

        return 0;
}

/*
 * Return NULL if skb is handled
 * note: already called with rcu_read_lock
 */
static rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
{
        enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
        struct net_bridge_port *p;
        struct sk_buff *skb = *pskb;
        const unsigned char *dest = eth_hdr(skb)->h_dest;

        if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
                return RX_HANDLER_PASS;

        if (!is_valid_ether_addr(eth_hdr(skb)->h_source)) {
                reason = SKB_DROP_REASON_MAC_INVALID_SOURCE;
                goto drop;
        }

        skb = skb_share_check(skb, GFP_ATOMIC);
        if (!skb)
                return RX_HANDLER_CONSUMED;

        memset(skb->cb, 0, sizeof(struct br_input_skb_cb));
        br_tc_skb_miss_set(skb, false);

        p = br_port_get_rcu(skb->dev);
        if (p->flags & BR_VLAN_TUNNEL)
                br_handle_ingress_vlan_tunnel(skb, p, nbp_vlan_group_rcu(p));

        if (unlikely(is_link_local_ether_addr(dest))) {
                u16 fwd_mask = p->br->group_fwd_mask_required;

                /*
                 * See IEEE 802.1D Table 7-10 Reserved addresses
                 *
                 * Assignment                           Value
                 * Bridge Group Address         01-80-C2-00-00-00
                 * (MAC Control) 802.3          01-80-C2-00-00-01
                 * (Link Aggregation) 802.3     01-80-C2-00-00-02
                 * 802.1X PAE address           01-80-C2-00-00-03
                 *
                 * 802.1AB LLDP                 01-80-C2-00-00-0E
                 *
                 * Others reserved for future standardization
                 */
                fwd_mask |= p->group_fwd_mask;
                switch (dest[5]) {
                case 0x00:      /* Bridge Group Address */
                        /* If STP is turned off,
                           then must forward to keep loop detection */
                        if (p->br->stp_enabled == BR_NO_STP ||
                            fwd_mask & (1u << dest[5]))
                                goto forward;
                        *pskb = skb;
                        __br_handle_local_finish(skb);
                        return RX_HANDLER_PASS;

                case 0x01:      /* IEEE MAC (Pause) */
                        reason = SKB_DROP_REASON_MAC_IEEE_MAC_CONTROL;
                        goto drop;

                case 0x0E:      /* 802.1AB LLDP */
                        fwd_mask |= p->br->group_fwd_mask;
                        if (fwd_mask & (1u << dest[5]))
                                goto forward;
                        *pskb = skb;
                        __br_handle_local_finish(skb);
                        return RX_HANDLER_PASS;

                default:
                        /* Allow selective forwarding for most other protocols */
                        fwd_mask |= p->br->group_fwd_mask;
                        if (fwd_mask & (1u << dest[5]))
                                goto forward;
                }

                BR_INPUT_SKB_CB(skb)->promisc = false;

                /* The else clause should be hit when nf_hook():
                 *   - returns < 0 (drop/error)
                 *   - returns = 0 (stolen/nf_queue)
                 * Thus return 1 from the okfn() to signal the skb is ok to pass
                 */
                if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN,
                            dev_net(skb->dev), NULL, skb, skb->dev, NULL,
                            br_handle_local_finish) == 1) {
                        return RX_HANDLER_PASS;
                } else {
                        return RX_HANDLER_CONSUMED;
                }
        }

        if (unlikely(br_process_frame_type(p, skb)))
                return RX_HANDLER_PASS;

forward:
        if (br_mst_is_enabled(p))
                goto defer_stp_filtering;

        switch (p->state) {
        case BR_STATE_FORWARDING:
        case BR_STATE_LEARNING:
defer_stp_filtering:
                if (ether_addr_equal(p->br->dev->dev_addr, dest))
                        skb->pkt_type = PACKET_HOST;

                return nf_hook_bridge_pre(skb, pskb);
        default:
                reason = SKB_DROP_REASON_BRIDGE_INGRESS_STP_STATE;
drop:
                kfree_skb_reason(skb, reason);
        }
        return RX_HANDLER_CONSUMED;
}

/* This function has no purpose other than to appease the br_port_get_rcu/rtnl
 * helpers which identify bridged ports according to the rx_handler installed
 * on them (so there _needs_ to be a bridge rx_handler even if we don't need it
 * to do anything useful). This bridge won't support traffic to/from the stack,
 * but only hardware bridging. So return RX_HANDLER_PASS so we don't steal
 * frames from the ETH_P_XDSA packet_type handler.
 */
static rx_handler_result_t br_handle_frame_dummy(struct sk_buff **pskb)
{
        return RX_HANDLER_PASS;
}

rx_handler_func_t *br_get_rx_handler(const struct net_device *dev)
{
        if (netdev_uses_dsa(dev))
                return br_handle_frame_dummy;

        return br_handle_frame;
}

void br_add_frame(struct net_bridge *br, struct br_frame_type *ft)
{
        hlist_add_head_rcu(&ft->list, &br->frame_type_list);
}

void br_del_frame(struct net_bridge *br, struct br_frame_type *ft)
{
        struct br_frame_type *tmp;

        hlist_for_each_entry(tmp, &br->frame_type_list, list)
                if (ft == tmp) {
                        hlist_del_rcu(&ft->list);
                        return;
                }
}