// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      IPv6 input
 *      Linux INET6 implementation
 *
 *      Authors:
 *      Pedro Roque             <roque@di.fc.ul.pt>
 *      Ian P. Morris           <I.P.Morris@soton.ac.uk>
 *
 *      Based in linux/net/ipv4/ip_input.c
 */
/* Changes
 *
 *      Mitsuru KANDA @USAGI and
 *      YOSHIFUJI Hideaki @USAGI: Remove ipv6_parse_exthdrs().
 */

#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/in6.h>
#include <linux/icmpv6.h>
#include <linux/mroute6.h>
#include <linux/slab.h>
#include <linux/indirect_call_wrapper.h>

#include <linux/netfilter.h>
#include <linux/netfilter_ipv6.h>

#include <net/sock.h>
#include <net/snmp.h>
#include <net/udp.h>

#include <net/ipv6.h>
#include <net/protocol.h>
#include <net/transp_v6.h>
#include <net/rawv6.h>
#include <net/ndisc.h>
#include <net/ip6_route.h>
#include <net/addrconf.h>
#include <net/xfrm.h>
#include <net/inet_ecn.h>
#include <net/dst_metadata.h>

INDIRECT_CALLABLE_DECLARE(void tcp_v6_early_demux(struct sk_buff *));
static void ip6_rcv_finish_core(struct net *net, struct sock *sk,
                                struct sk_buff *skb)
{
        void (*edemux)(struct sk_buff *skb);

        if (net->ipv4.sysctl_ip_early_demux && !skb_dst(skb) && skb->sk == NULL) {
                const struct inet6_protocol *ipprot;

                ipprot = rcu_dereference(inet6_protos[ipv6_hdr(skb)->nexthdr]);
                if (ipprot && (edemux = READ_ONCE(ipprot->early_demux)))
                        INDIRECT_CALL_2(edemux, tcp_v6_early_demux,
                                        udp_v6_early_demux, skb);
        }
        if (!skb_valid_dst(skb))
                ip6_route_input(skb);
}

int ip6_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        /* if ingress device is enslaved to an L3 master device pass the
         * skb to its handler for processing
         */
        skb = l3mdev_ip6_rcv(skb);
        if (!skb)
                return NET_RX_SUCCESS;
        ip6_rcv_finish_core(net, sk, skb);

        return dst_input(skb);
}

static void ip6_sublist_rcv_finish(struct list_head *head)
{
        struct sk_buff *skb, *next;

        list_for_each_entry_safe(skb, next, head, list) {
                skb_list_del_init(skb);
                dst_input(skb);
        }
}

static bool ip6_can_use_hint(const struct sk_buff *skb,
                             const struct sk_buff *hint)
{
        return hint && !skb_dst(skb) &&
               ipv6_addr_equal(&ipv6_hdr(hint)->daddr, &ipv6_hdr(skb)->daddr);
}

static struct sk_buff *ip6_extract_route_hint(const struct net *net,
                                              struct sk_buff *skb)
{
        if (fib6_routes_require_src(net) || fib6_has_custom_rules(net))
                return NULL;

        return skb;
}

static void ip6_list_rcv_finish(struct net *net, struct sock *sk,
                                struct list_head *head)
{
        struct sk_buff *skb, *next, *hint = NULL;
        struct dst_entry *curr_dst = NULL;
        struct list_head sublist;

        INIT_LIST_HEAD(&sublist);
        list_for_each_entry_safe(skb, next, head, list) {
                struct dst_entry *dst;

                skb_list_del_init(skb);
                /* if ingress device is enslaved to an L3 master device pass the
                 * skb to its handler for processing
                 */
                skb = l3mdev_ip6_rcv(skb);
                if (!skb)
                        continue;

                if (ip6_can_use_hint(skb, hint))
                        skb_dst_copy(skb, hint);
                else
                        ip6_rcv_finish_core(net, sk, skb);
                dst = skb_dst(skb);
                if (curr_dst != dst) {
                        hint = ip6_extract_route_hint(net, skb);

                        /* dispatch old sublist */
                        if (!list_empty(&sublist))
                                ip6_sublist_rcv_finish(&sublist);
                        /* start new sublist */
                        INIT_LIST_HEAD(&sublist);
                        curr_dst = dst;
                }
                list_add_tail(&skb->list, &sublist);
        }
        /* dispatch final sublist */
        ip6_sublist_rcv_finish(&sublist);
}

static struct sk_buff *ip6_rcv_core(struct sk_buff *skb, struct net_device *dev,
                                    struct net *net)
{
        const struct ipv6hdr *hdr;
        u32 pkt_len;
        struct inet6_dev *idev;

        if (skb->pkt_type == PACKET_OTHERHOST) {
                kfree_skb(skb);
                return NULL;
        }

        rcu_read_lock();

        idev = __in6_dev_get(skb->dev);

        __IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_IN, skb->len);

        if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL ||
            !idev || unlikely(idev->cnf.disable_ipv6)) {
                __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
                goto drop;
        }

        memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));

        /*
         * Store incoming device index. When the packet will
         * be queued, we cannot refer to skb->dev anymore.
         *
         * BTW, when we send a packet for our own local address on a
         * non-loopback interface (e.g. ethX), it is being delivered
         * via the loopback interface (lo) here; skb->dev = loopback_dev.
         * It, however, should be considered as if it is being
         * arrived via the sending interface (ethX), because of the
         * nature of scoping architecture. --yoshfuji
         */
        IP6CB(skb)->iif = skb_valid_dst(skb) ? ip6_dst_idev(skb_dst(skb))->dev->ifindex : dev->ifindex;

        if (unlikely(!pskb_may_pull(skb, sizeof(*hdr))))
                goto err;

        hdr = ipv6_hdr(skb);

        if (hdr->version != 6)
                goto err;

        __IP6_ADD_STATS(net, idev,
                        IPSTATS_MIB_NOECTPKTS +
                                (ipv6_get_dsfield(hdr) & INET_ECN_MASK),
                        max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs));
        /*
         * RFC4291 2.5.3
         * The loopback address must not be used as the source address in IPv6
         * packets that are sent outside of a single node. [..]
         * A packet received on an interface with a destination address
         * of loopback must be dropped.
         */
        if ((ipv6_addr_loopback(&hdr->saddr) ||
             ipv6_addr_loopback(&hdr->daddr)) &&
            !(dev->flags & IFF_LOOPBACK) &&
            !netif_is_l3_master(dev))
                goto err;

        /* RFC4291 Errata ID: 3480
         * Interface-Local scope spans only a single interface on a
         * node and is useful only for loopback transmission of
         * multicast.  Packets with interface-local scope received
         * from another node must be discarded.
         */
        if (!(skb->pkt_type == PACKET_LOOPBACK ||
              dev->flags & IFF_LOOPBACK) &&
            ipv6_addr_is_multicast(&hdr->daddr) &&
            IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 1)
                goto err;

        /* If enabled, drop unicast packets that were encapsulated in link-layer
         * multicast or broadcast to protected against the so-called "hole-196"
         * attack in 802.11 wireless.
         */
        if (!ipv6_addr_is_multicast(&hdr->daddr) &&
            (skb->pkt_type == PACKET_BROADCAST ||
             skb->pkt_type == PACKET_MULTICAST) &&
            idev->cnf.drop_unicast_in_l2_multicast)
                goto err;

        /* RFC4291 2.7
         * Nodes must not originate a packet to a multicast address whose scope
         * field contains the reserved value 0; if such a packet is received, it
         * must be silently dropped.
         */
        if (ipv6_addr_is_multicast(&hdr->daddr) &&
            IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 0)
                goto err;

        /*
         * RFC4291 2.7
         * Multicast addresses must not be used as source addresses in IPv6
         * packets or appear in any Routing header.
         */
        if (ipv6_addr_is_multicast(&hdr->saddr))
                goto err;

        skb->transport_header = skb->network_header + sizeof(*hdr);
        IP6CB(skb)->nhoff = offsetof(struct ipv6hdr, nexthdr);

        pkt_len = ntohs(hdr->payload_len);

        /* pkt_len may be zero if Jumbo payload option is present */
        if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
                if (pkt_len + sizeof(struct ipv6hdr) > skb->len) {
                        __IP6_INC_STATS(net,
                                        idev, IPSTATS_MIB_INTRUNCATEDPKTS);
                        goto drop;
                }
                if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr))) {
                        __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
                        goto drop;
                }
                hdr = ipv6_hdr(skb);
        }

        if (hdr->nexthdr == NEXTHDR_HOP) {
                if (ipv6_parse_hopopts(skb) < 0) {
                        __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
                        rcu_read_unlock();
                        return NULL;
                }
        }

        rcu_read_unlock();

        /* Must drop socket now because of tproxy. */
        if (!skb_sk_is_prefetched(skb))
                skb_orphan(skb);

        return skb;
err:
        __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
drop:
        rcu_read_unlock();
        kfree_skb(skb);
        return NULL;
}

int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
{
        struct net *net = dev_net(skb->dev);

        skb = ip6_rcv_core(skb, dev, net);
        if (skb == NULL)
                return NET_RX_DROP;
        return NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,
                       net, NULL, skb, dev, NULL,
                       ip6_rcv_finish);
}

static void ip6_sublist_rcv(struct list_head *head, struct net_device *dev,
                            struct net *net)
{
        NF_HOOK_LIST(NFPROTO_IPV6, NF_INET_PRE_ROUTING, net, NULL,
                     head, dev, NULL, ip6_rcv_finish);
        ip6_list_rcv_finish(net, NULL, head);
}

/* Receive a list of IPv6 packets */
void ipv6_list_rcv(struct list_head *head, struct packet_type *pt,
                   struct net_device *orig_dev)
{
        struct net_device *curr_dev = NULL;
        struct net *curr_net = NULL;
        struct sk_buff *skb, *next;
        struct list_head sublist;

        INIT_LIST_HEAD(&sublist);
        list_for_each_entry_safe(skb, next, head, list) {
                struct net_device *dev = skb->dev;
                struct net *net = dev_net(dev);

                skb_list_del_init(skb);
                skb = ip6_rcv_core(skb, dev, net);
                if (skb == NULL)
                        continue;

                if (curr_dev != dev || curr_net != net) {
                        /* dispatch old sublist */
                        if (!list_empty(&sublist))
                                ip6_sublist_rcv(&sublist, curr_dev, curr_net);
                        /* start new sublist */
                        INIT_LIST_HEAD(&sublist);
                        curr_dev = dev;
                        curr_net = net;
                }
                list_add_tail(&skb->list, &sublist);
        }
        /* dispatch final sublist */
        if (!list_empty(&sublist))
                ip6_sublist_rcv(&sublist, curr_dev, curr_net);
}

INDIRECT_CALLABLE_DECLARE(int tcp_v6_rcv(struct sk_buff *));

/*
 *      Deliver the packet to the host
 */
void ip6_protocol_deliver_rcu(struct net *net, struct sk_buff *skb, int nexthdr,
                              bool have_final)
{
        const struct inet6_protocol *ipprot;
        struct inet6_dev *idev;
        unsigned int nhoff;
        bool raw;

        /*
         *      Parse extension headers
         */

resubmit:
        idev = ip6_dst_idev(skb_dst(skb));
        nhoff = IP6CB(skb)->nhoff;
        if (!have_final) {
                if (!pskb_pull(skb, skb_transport_offset(skb)))
                        goto discard;
                nexthdr = skb_network_header(skb)[nhoff];
        }

resubmit_final:
        raw = raw6_local_deliver(skb, nexthdr);
        ipprot = rcu_dereference(inet6_protos[nexthdr]);
        if (ipprot) {
                int ret;

                if (have_final) {
                        if (!(ipprot->flags & INET6_PROTO_FINAL)) {
                                /* Once we've seen a final protocol don't
                                 * allow encapsulation on any non-final
                                 * ones. This allows foo in UDP encapsulation
                                 * to work.
                                 */
                                goto discard;
                        }
                } else if (ipprot->flags & INET6_PROTO_FINAL) {
                        const struct ipv6hdr *hdr;
                        int sdif = inet6_sdif(skb);
                        struct net_device *dev;

                        /* Only do this once for first final protocol */
                        have_final = true;

                        /* Free reference early: we don't need it any more,
                           and it may hold ip_conntrack module loaded
                           indefinitely. */
                        nf_reset_ct(skb);

                        skb_postpull_rcsum(skb, skb_network_header(skb),
                                           skb_network_header_len(skb));
                        hdr = ipv6_hdr(skb);

                        /* skb->dev passed may be master dev for vrfs. */
                        if (sdif) {
                                dev = dev_get_by_index_rcu(net, sdif);
                                if (!dev)
                                        goto discard;
                        } else {
                                dev = skb->dev;
                        }

                        if (ipv6_addr_is_multicast(&hdr->daddr) &&
                            !ipv6_chk_mcast_addr(dev, &hdr->daddr,
                                                 &hdr->saddr) &&
                            !ipv6_is_mld(skb, nexthdr, skb_network_header_len(skb)))
                                goto discard;
                }
                if (!(ipprot->flags & INET6_PROTO_NOPOLICY) &&
                    !xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb))
                        goto discard;

                ret = INDIRECT_CALL_2(ipprot->handler, tcp_v6_rcv, udpv6_rcv,
                                      skb);
                if (ret > 0) {
                        if (ipprot->flags & INET6_PROTO_FINAL) {
                                /* Not an extension header, most likely UDP
                                 * encapsulation. Use return value as nexthdr
                                 * protocol not nhoff (which presumably is
                                 * not set by handler).
                                 */
                                nexthdr = ret;
                                goto resubmit_final;
                        } else {
                                goto resubmit;
                        }
                } else if (ret == 0) {
                        __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
                }
        } else {
                if (!raw) {
                        if (xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
                                __IP6_INC_STATS(net, idev,
                                                IPSTATS_MIB_INUNKNOWNPROTOS);
                                icmpv6_send(skb, ICMPV6_PARAMPROB,
                                            ICMPV6_UNK_NEXTHDR, nhoff);
                        }
                        kfree_skb(skb);
                } else {
                        __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
                        consume_skb(skb);
                }
        }
        return;

discard:
        __IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
        kfree_skb(skb);
}

static int ip6_input_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        rcu_read_lock();
        ip6_protocol_deliver_rcu(net, skb, 0, false);
        rcu_read_unlock();

        return 0;
}


int ip6_input(struct sk_buff *skb)
{
        return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_IN,
                       dev_net(skb->dev), NULL, skb, skb->dev, NULL,
                       ip6_input_finish);
}
EXPORT_SYMBOL_GPL(ip6_input);

int ip6_mc_input(struct sk_buff *skb)
{
        int sdif = inet6_sdif(skb);
        const struct ipv6hdr *hdr;
        struct net_device *dev;
        bool deliver;

        __IP6_UPD_PO_STATS(dev_net(skb_dst(skb)->dev),
                         __in6_dev_get_safely(skb->dev), IPSTATS_MIB_INMCAST,
                         skb->len);

        /* skb->dev passed may be master dev for vrfs. */
        if (sdif) {
                rcu_read_lock();
                dev = dev_get_by_index_rcu(dev_net(skb->dev), sdif);
                if (!dev) {
                        rcu_read_unlock();
                        kfree_skb(skb);
                        return -ENODEV;
                }
        } else {
                dev = skb->dev;
        }

        hdr = ipv6_hdr(skb);
        deliver = ipv6_chk_mcast_addr(dev, &hdr->daddr, NULL);
        if (sdif)
                rcu_read_unlock();

#ifdef CONFIG_IPV6_MROUTE
        /*
         *      IPv6 multicast router mode is now supported ;)
         */
        if (dev_net(skb->dev)->ipv6.devconf_all->mc_forwarding &&
            !(ipv6_addr_type(&hdr->daddr) &
              (IPV6_ADDR_LOOPBACK|IPV6_ADDR_LINKLOCAL)) &&
            likely(!(IP6CB(skb)->flags & IP6SKB_FORWARDED))) {
                /*
                 * Okay, we try to forward - split and duplicate
                 * packets.
                 */
                struct sk_buff *skb2;
                struct inet6_skb_parm *opt = IP6CB(skb);

                /* Check for MLD */
                if (unlikely(opt->flags & IP6SKB_ROUTERALERT)) {
                        /* Check if this is a mld message */
                        u8 nexthdr = hdr->nexthdr;
                        __be16 frag_off;
                        int offset;

                        /* Check if the value of Router Alert
                         * is for MLD (0x0000).
                         */
                        if (opt->ra == htons(IPV6_OPT_ROUTERALERT_MLD)) {
                                deliver = false;

                                if (!ipv6_ext_hdr(nexthdr)) {
                                        /* BUG */
                                        goto out;
                                }
                                offset = ipv6_skip_exthdr(skb, sizeof(*hdr),
                                                          &nexthdr, &frag_off);
                                if (offset < 0)
                                        goto out;

                                if (ipv6_is_mld(skb, nexthdr, offset))
                                        deliver = true;

                                goto out;
                        }
                        /* unknown RA - process it normally */
                }

                if (deliver)
                        skb2 = skb_clone(skb, GFP_ATOMIC);
                else {
                        skb2 = skb;
                        skb = NULL;
                }

                if (skb2) {
                        ip6_mr_input(skb2);
                }
        }
out:
#endif
        if (likely(deliver))
                ip6_input(skb);
        else {
                /* discard */
                kfree_skb(skb);
        }

        return 0;
}