// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Handle bridge arp/nd proxy/suppress
 *
 *  Copyright (C) 2017 Cumulus Networks
 *  Copyright (c) 2017 Roopa Prabhu <roopa@cumulusnetworks.com>
 *
 *  Authors:
 *      Roopa Prabhu <roopa@cumulusnetworks.com>
 */

#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/neighbour.h>
#include <net/arp.h>
#include <linux/if_vlan.h>
#include <linux/inetdevice.h>
#include <net/addrconf.h>
#include <net/ipv6_stubs.h>
#if IS_ENABLED(CONFIG_IPV6)
#include <net/ip6_checksum.h>
#endif

#include "br_private.h"

void br_recalculate_neigh_suppress_enabled(struct net_bridge *br)
{
        struct net_bridge_port *p;
        bool neigh_suppress = false;

        list_for_each_entry(p, &br->port_list, list) {
                if (p->flags & (BR_NEIGH_SUPPRESS | BR_NEIGH_VLAN_SUPPRESS)) {
                        neigh_suppress = true;
                        break;
                }
        }

        br_opt_toggle(br, BROPT_NEIGH_SUPPRESS_ENABLED, neigh_suppress);
}

#if IS_ENABLED(CONFIG_INET)
static void br_arp_send(struct net_bridge *br, struct net_bridge_port *p,
                        struct net_device *dev, __be32 dest_ip, __be32 src_ip,
                        const unsigned char *dest_hw,
                        const unsigned char *src_hw,
                        const unsigned char *target_hw,
                        __be16 vlan_proto, u16 vlan_tci)
{
        struct net_bridge_vlan_group *vg;
        struct sk_buff *skb;
        u16 pvid;

        netdev_dbg(dev, "arp send dev %s dst %pI4 dst_hw %pM src %pI4 src_hw %pM\n",
                   dev->name, &dest_ip, dest_hw, &src_ip, src_hw);

        if (!vlan_tci) {
                arp_send(ARPOP_REPLY, ETH_P_ARP, dest_ip, dev, src_ip,
                         dest_hw, src_hw, target_hw);
                return;
        }

        skb = arp_create(ARPOP_REPLY, ETH_P_ARP, dest_ip, dev, src_ip,
                         dest_hw, src_hw, target_hw);
        if (!skb)
                return;

        if (p)
                vg = nbp_vlan_group_rcu(p);
        else
                vg = br_vlan_group_rcu(br);
        pvid = br_get_pvid(vg);
        if (pvid == (vlan_tci & VLAN_VID_MASK))
                vlan_tci = 0;

        if (vlan_tci)
                __vlan_hwaccel_put_tag(skb, vlan_proto, vlan_tci);

        if (p) {
                arp_xmit(skb);
        } else {
                skb_reset_mac_header(skb);
                __skb_pull(skb, skb_network_offset(skb));
                skb->ip_summed = CHECKSUM_UNNECESSARY;
                skb->pkt_type = PACKET_HOST;

                netif_rx(skb);
        }
}

static int br_chk_addr_ip(struct net_device *dev,
                          struct netdev_nested_priv *priv)
{
        __be32 ip = *(__be32 *)priv->data;
        struct in_device *in_dev;
        __be32 addr = 0;

        in_dev = __in_dev_get_rcu(dev);
        if (in_dev)
                addr = inet_confirm_addr(dev_net(dev), in_dev, 0, ip,
                                         RT_SCOPE_HOST);

        if (addr == ip)
                return 1;

        return 0;
}

static bool br_is_local_ip(struct net_device *dev, __be32 ip)
{
        struct netdev_nested_priv priv = {
                .data = (void *)&ip,
        };

        if (br_chk_addr_ip(dev, &priv))
                return true;

        /* check if ip is configured on upper dev */
        if (netdev_walk_all_upper_dev_rcu(dev, br_chk_addr_ip, &priv))
                return true;

        return false;
}

void br_do_proxy_suppress_arp(struct sk_buff *skb, struct net_bridge *br,
                              u16 vid, struct net_bridge_port *p)
{
        struct net_device *dev = br->dev;
        struct net_device *vlandev = dev;
        struct neighbour *n;
        struct arphdr *parp;
        u8 *arpptr, *sha;
        __be32 sip, tip;

        BR_INPUT_SKB_CB(skb)->proxyarp_replied = 0;

        if ((dev->flags & IFF_NOARP) ||
            !pskb_may_pull(skb, arp_hdr_len(dev)))
                return;

        parp = arp_hdr(skb);

        if (parp->ar_pro != htons(ETH_P_IP) ||
            parp->ar_hln != dev->addr_len ||
            parp->ar_pln != 4)
                return;

        arpptr = (u8 *)parp + sizeof(struct arphdr);
        sha = arpptr;
        arpptr += dev->addr_len;        /* sha */
        memcpy(&sip, arpptr, sizeof(sip));
        arpptr += sizeof(sip);
        arpptr += dev->addr_len;        /* tha */
        memcpy(&tip, arpptr, sizeof(tip));

        if (ipv4_is_loopback(tip) ||
            ipv4_is_multicast(tip))
                return;

        if (br_opt_get(br, BROPT_NEIGH_SUPPRESS_ENABLED)) {
                if (br_is_neigh_suppress_enabled(p, vid))
                        return;
                if (is_unicast_ether_addr(eth_hdr(skb)->h_dest) &&
                    parp->ar_op == htons(ARPOP_REQUEST))
                        return;
                if (parp->ar_op != htons(ARPOP_RREQUEST) &&
                    parp->ar_op != htons(ARPOP_RREPLY) &&
                    (ipv4_is_zeronet(sip) || sip == tip)) {
                        /* prevent flooding to neigh suppress ports */
                        BR_INPUT_SKB_CB(skb)->proxyarp_replied = 1;
                        return;
                }
        }

        if (parp->ar_op != htons(ARPOP_REQUEST))
                return;

        if (vid != 0) {
                vlandev = __vlan_find_dev_deep_rcu(br->dev, skb->vlan_proto,
                                                   vid);
                if (!vlandev)
                        return;
        }

        if (br_opt_get(br, BROPT_NEIGH_SUPPRESS_ENABLED) &&
            br_is_local_ip(vlandev, tip)) {
                /* its our local ip, so don't proxy reply
                 * and don't forward to neigh suppress ports
                 */
                BR_INPUT_SKB_CB(skb)->proxyarp_replied = 1;
                return;
        }

        n = neigh_lookup(&arp_tbl, &tip, vlandev);
        if (n) {
                struct net_bridge_fdb_entry *f;

                if (!(READ_ONCE(n->nud_state) & NUD_VALID)) {
                        neigh_release(n);
                        return;
                }

                f = br_fdb_find_rcu(br, n->ha, vid);
                if (f) {
                        bool replied = false;

                        if ((p && (p->flags & BR_PROXYARP)) ||
                            (f->dst && (f->dst->flags & BR_PROXYARP_WIFI)) ||
                            br_is_neigh_suppress_enabled(f->dst, vid)) {
                                if (!vid)
                                        br_arp_send(br, p, skb->dev, sip, tip,
                                                    sha, n->ha, sha, 0, 0);
                                else
                                        br_arp_send(br, p, skb->dev, sip, tip,
                                                    sha, n->ha, sha,
                                                    skb->vlan_proto,
                                                    skb_vlan_tag_get(skb));
                                replied = true;
                        }

                        /* If we have replied or as long as we know the
                         * mac, indicate to arp replied
                         */
                        if (replied ||
                            br_opt_get(br, BROPT_NEIGH_SUPPRESS_ENABLED))
                                BR_INPUT_SKB_CB(skb)->proxyarp_replied = 1;
                }

                neigh_release(n);
        }
}
#endif

#if IS_ENABLED(CONFIG_IPV6)
struct nd_msg *br_is_nd_neigh_msg(const struct sk_buff *skb, struct nd_msg *msg)
{
        struct nd_msg *m;

        m = skb_header_pointer(skb, skb_network_offset(skb) +
                               sizeof(struct ipv6hdr), sizeof(*msg), msg);
        if (!m)
                return NULL;

        if (m->icmph.icmp6_code != 0 ||
            (m->icmph.icmp6_type != NDISC_NEIGHBOUR_SOLICITATION &&
             m->icmph.icmp6_type != NDISC_NEIGHBOUR_ADVERTISEMENT))
                return NULL;

        return m;
}

static void br_nd_send(struct net_bridge *br, struct net_bridge_port *p,
                       struct sk_buff *request, struct neighbour *n,
                       __be16 vlan_proto, u16 vlan_tci)
{
        struct net_device *dev = request->dev;
        struct net_bridge_vlan_group *vg;
        struct nd_msg *na, *ns;
        struct sk_buff *reply;
        struct ipv6hdr *pip6;
        int na_olen = 8; /* opt hdr + ETH_ALEN for target */
        int ns_olen;
        int i, len;
        u8 *daddr;
        u16 pvid;

        if (!dev || skb_linearize(request))
                return;

        len = LL_RESERVED_SPACE(dev) + sizeof(struct ipv6hdr) +
                sizeof(*na) + na_olen + dev->needed_tailroom;

        reply = alloc_skb(len, GFP_ATOMIC);
        if (!reply)
                return;

        reply->protocol = htons(ETH_P_IPV6);
        reply->dev = dev;
        skb_reserve(reply, LL_RESERVED_SPACE(dev));
        skb_push(reply, sizeof(struct ethhdr));
        skb_set_mac_header(reply, 0);

        daddr = eth_hdr(request)->h_source;
        ns = (struct nd_msg *)(skb_network_header(request) +
                               sizeof(struct ipv6hdr));

        /* Do we need option processing ? */
        ns_olen = request->len - (skb_network_offset(request) +
                                  sizeof(struct ipv6hdr)) - sizeof(*ns);
        for (i = 0; i < ns_olen - 1; i += (ns->opt[i + 1] << 3)) {
                if (!ns->opt[i + 1] || i + (ns->opt[i + 1] << 3) > ns_olen) {
                        kfree_skb(reply);
                        return;
                }
                if (ns->opt[i] == ND_OPT_SOURCE_LL_ADDR) {
                        if ((ns->opt[i + 1] << 3) >=
                            sizeof(struct nd_opt_hdr) + ETH_ALEN)
                                daddr = ns->opt + i + sizeof(struct nd_opt_hdr);
                        break;
                }
        }

        /* Ethernet header */
        ether_addr_copy(eth_hdr(reply)->h_dest, daddr);
        ether_addr_copy(eth_hdr(reply)->h_source, n->ha);
        eth_hdr(reply)->h_proto = htons(ETH_P_IPV6);
        reply->protocol = htons(ETH_P_IPV6);

        skb_pull(reply, sizeof(struct ethhdr));
        skb_set_network_header(reply, 0);
        skb_put(reply, sizeof(struct ipv6hdr));

        /* IPv6 header */
        pip6 = ipv6_hdr(reply);
        memset(pip6, 0, sizeof(struct ipv6hdr));
        pip6->version = 6;
        pip6->priority = ipv6_hdr(request)->priority;
        pip6->nexthdr = IPPROTO_ICMPV6;
        pip6->hop_limit = 255;
        pip6->daddr = ipv6_hdr(request)->saddr;
        pip6->saddr = *(struct in6_addr *)n->primary_key;

        skb_pull(reply, sizeof(struct ipv6hdr));
        skb_set_transport_header(reply, 0);

        na = (struct nd_msg *)skb_put(reply, sizeof(*na) + na_olen);

        /* Neighbor Advertisement */
        memset(na, 0, sizeof(*na) + na_olen);
        na->icmph.icmp6_type = NDISC_NEIGHBOUR_ADVERTISEMENT;
        na->icmph.icmp6_router = (n->flags & NTF_ROUTER) ? 1 : 0;
        na->icmph.icmp6_override = 1;
        na->icmph.icmp6_solicited = 1;
        na->target = ns->target;
        ether_addr_copy(&na->opt[2], n->ha);
        na->opt[0] = ND_OPT_TARGET_LL_ADDR;
        na->opt[1] = na_olen >> 3;

        na->icmph.icmp6_cksum = csum_ipv6_magic(&pip6->saddr,
                                                &pip6->daddr,
                                                sizeof(*na) + na_olen,
                                                IPPROTO_ICMPV6,
                                                csum_partial(na, sizeof(*na) + na_olen, 0));

        pip6->payload_len = htons(sizeof(*na) + na_olen);

        skb_push(reply, sizeof(struct ipv6hdr));
        skb_push(reply, sizeof(struct ethhdr));

        reply->ip_summed = CHECKSUM_UNNECESSARY;

        if (p)
                vg = nbp_vlan_group_rcu(p);
        else
                vg = br_vlan_group_rcu(br);
        pvid = br_get_pvid(vg);
        if (pvid == (vlan_tci & VLAN_VID_MASK))
                vlan_tci = 0;

        if (vlan_tci)
                __vlan_hwaccel_put_tag(reply, vlan_proto, vlan_tci);

        netdev_dbg(dev, "nd send dev %s dst %pI6 dst_hw %pM src %pI6 src_hw %pM\n",
                   dev->name, &pip6->daddr, daddr, &pip6->saddr, n->ha);

        if (p) {
                dev_queue_xmit(reply);
        } else {
                skb_reset_mac_header(reply);
                __skb_pull(reply, skb_network_offset(reply));
                reply->ip_summed = CHECKSUM_UNNECESSARY;
                reply->pkt_type = PACKET_HOST;

                netif_rx(reply);
        }
}

static int br_chk_addr_ip6(struct net_device *dev,
                           struct netdev_nested_priv *priv)
{
        struct in6_addr *addr = (struct in6_addr *)priv->data;

        if (ipv6_chk_addr(dev_net(dev), addr, dev, 0))
                return 1;

        return 0;
}

static bool br_is_local_ip6(struct net_device *dev, struct in6_addr *addr)

{
        struct netdev_nested_priv priv = {
                .data = (void *)addr,
        };

        if (br_chk_addr_ip6(dev, &priv))
                return true;

        /* check if ip is configured on upper dev */
        if (netdev_walk_all_upper_dev_rcu(dev, br_chk_addr_ip6, &priv))
                return true;

        return false;
}

void br_do_suppress_nd(struct sk_buff *skb, struct net_bridge *br,
                       u16 vid, struct net_bridge_port *p, struct nd_msg *msg)
{
        struct net_device *dev = br->dev;
        struct net_device *vlandev = NULL;
        struct in6_addr *saddr, *daddr;
        struct ipv6hdr *iphdr;
        struct neighbour *n;

        BR_INPUT_SKB_CB(skb)->proxyarp_replied = 0;

        if (br_is_neigh_suppress_enabled(p, vid))
                return;

        if (is_unicast_ether_addr(eth_hdr(skb)->h_dest) &&
            msg->icmph.icmp6_type == NDISC_NEIGHBOUR_SOLICITATION)
                return;

        if (msg->icmph.icmp6_type == NDISC_NEIGHBOUR_ADVERTISEMENT &&
            !msg->icmph.icmp6_solicited) {
                /* prevent flooding to neigh suppress ports */
                BR_INPUT_SKB_CB(skb)->proxyarp_replied = 1;
                return;
        }

        if (msg->icmph.icmp6_type != NDISC_NEIGHBOUR_SOLICITATION)
                return;

        iphdr = ipv6_hdr(skb);
        saddr = &iphdr->saddr;
        daddr = &iphdr->daddr;

        if (ipv6_addr_any(saddr) || !ipv6_addr_cmp(saddr, daddr)) {
                /* prevent flooding to neigh suppress ports */
                BR_INPUT_SKB_CB(skb)->proxyarp_replied = 1;
                return;
        }

        if (vid != 0) {
                /* build neigh table lookup on the vlan device */
                vlandev = __vlan_find_dev_deep_rcu(br->dev, skb->vlan_proto,
                                                   vid);
                if (!vlandev)
                        return;
        } else {
                vlandev = dev;
        }

        if (br_is_local_ip6(vlandev, &msg->target)) {
                /* its our own ip, so don't proxy reply
                 * and don't forward to arp suppress ports
                 */
                BR_INPUT_SKB_CB(skb)->proxyarp_replied = 1;
                return;
        }

        n = neigh_lookup(ipv6_stub->nd_tbl, &msg->target, vlandev);
        if (n) {
                struct net_bridge_fdb_entry *f;

                if (!(READ_ONCE(n->nud_state) & NUD_VALID)) {
                        neigh_release(n);
                        return;
                }

                f = br_fdb_find_rcu(br, n->ha, vid);
                if (f) {
                        bool replied = false;

                        if (br_is_neigh_suppress_enabled(f->dst, vid)) {
                                if (vid != 0)
                                        br_nd_send(br, p, skb, n,
                                                   skb->vlan_proto,
                                                   skb_vlan_tag_get(skb));
                                else
                                        br_nd_send(br, p, skb, n, 0, 0);
                                replied = true;
                        }

                        /* If we have replied or as long as we know the
                         * mac, indicate to NEIGH_SUPPRESS ports that we
                         * have replied
                         */
                        if (replied ||
                            br_opt_get(br, BROPT_NEIGH_SUPPRESS_ENABLED))
                                BR_INPUT_SKB_CB(skb)->proxyarp_replied = 1;
                }
                neigh_release(n);
        }
}
#endif

bool br_is_neigh_suppress_enabled(const struct net_bridge_port *p, u16 vid)
{
        if (!p)
                return false;

        if (!vid)
                return !!(p->flags & BR_NEIGH_SUPPRESS);

        if (p->flags & BR_NEIGH_VLAN_SUPPRESS) {
                struct net_bridge_vlan_group *vg = nbp_vlan_group_rcu(p);
                struct net_bridge_vlan *v;

                v = br_vlan_find(vg, vid);
                if (!v)
                        return false;
                return !!(v->priv_flags & BR_VLFLAG_NEIGH_SUPPRESS_ENABLED);
        } else {
                return !!(p->flags & BR_NEIGH_SUPPRESS);
        }
}