// SPDX-License-Identifier: GPL-2.0-only
#include <net/netfilter/nf_tproxy.h>
#include <linux/module.h>
#include <net/inet6_hashtables.h>
#include <net/addrconf.h>
#include <net/udp.h>
#include <net/tcp.h>

const struct in6_addr *
nf_tproxy_laddr6(struct sk_buff *skb, const struct in6_addr *user_laddr,
              const struct in6_addr *daddr)
{
        struct inet6_dev *indev;
        struct inet6_ifaddr *ifa;
        struct in6_addr *laddr;

        if (!ipv6_addr_any(user_laddr))
                return user_laddr;
        laddr = NULL;

        indev = __in6_dev_get(skb->dev);
        if (indev) {
                read_lock_bh(&indev->lock);
                list_for_each_entry(ifa, &indev->addr_list, if_list) {
                        if (ifa->flags & (IFA_F_TENTATIVE | IFA_F_DEPRECATED))
                                continue;

                        laddr = &ifa->addr;
                        break;
                }
                read_unlock_bh(&indev->lock);
        }

        return laddr ? laddr : daddr;
}
EXPORT_SYMBOL_GPL(nf_tproxy_laddr6);

struct sock *
nf_tproxy_handle_time_wait6(struct sk_buff *skb, int tproto, int thoff,
                         struct net *net,
                         const struct in6_addr *laddr,
                         const __be16 lport,
                         struct sock *sk)
{
        const struct ipv6hdr *iph = ipv6_hdr(skb);
        struct tcphdr _hdr, *hp;

        hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
        if (hp == NULL) {
                inet_twsk_put(inet_twsk(sk));
                return NULL;
        }

        if (hp->syn && !hp->rst && !hp->ack && !hp->fin) {
                /* SYN to a TIME_WAIT socket, we'd rather redirect it
                 * to a listener socket if there's one */
                struct sock *sk2;

                sk2 = nf_tproxy_get_sock_v6(net, skb, thoff, tproto,
                                            &iph->saddr,
                                            nf_tproxy_laddr6(skb, laddr, &iph->daddr),
                                            hp->source,
                                            lport ? lport : hp->dest,
                                            skb->dev, NF_TPROXY_LOOKUP_LISTENER);
                if (sk2) {
                        nf_tproxy_twsk_deschedule_put(inet_twsk(sk));
                        sk = sk2;
                }
        }

        return sk;
}
EXPORT_SYMBOL_GPL(nf_tproxy_handle_time_wait6);

struct sock *
nf_tproxy_get_sock_v6(struct net *net, struct sk_buff *skb, int thoff,
                      const u8 protocol,
                      const struct in6_addr *saddr, const struct in6_addr *daddr,
                      const __be16 sport, const __be16 dport,
                      const struct net_device *in,
                      const enum nf_tproxy_lookup_t lookup_type)
{
        struct sock *sk;

        switch (protocol) {
        case IPPROTO_TCP: {
                struct tcphdr _hdr, *hp;

                hp = skb_header_pointer(skb, thoff,
                                        sizeof(struct tcphdr), &_hdr);
                if (hp == NULL)
                        return NULL;

                switch (lookup_type) {
                case NF_TPROXY_LOOKUP_LISTENER:
                        sk = inet6_lookup_listener(net, skb,
                                                   thoff + __tcp_hdrlen(hp),
                                                   saddr, sport,
                                                   daddr, ntohs(dport),
                                                   in->ifindex, 0);

                        if (sk && !refcount_inc_not_zero(&sk->sk_refcnt))
                                sk = NULL;
                        /* NOTE: we return listeners even if bound to
                         * 0.0.0.0, those are filtered out in
                         * xt_socket, since xt_TPROXY needs 0 bound
                         * listeners too
                         */
                        break;
                case NF_TPROXY_LOOKUP_ESTABLISHED:
                        sk = __inet6_lookup_established(net, saddr, sport, daddr,
                                                        ntohs(dport), in->ifindex, 0);
                        break;
                default:
                        BUG();
                }
                break;
                }
        case IPPROTO_UDP:
                sk = udp6_lib_lookup(net, saddr, sport, daddr, dport,
                                     in->ifindex);
                if (sk) {
                        int connected = (sk->sk_state == TCP_ESTABLISHED);
                        int wildcard = ipv6_addr_any(&sk->sk_v6_rcv_saddr);

                        /* NOTE: we return listeners even if bound to
                         * 0.0.0.0, those are filtered out in
                         * xt_socket, since xt_TPROXY needs 0 bound
                         * listeners too
                         */
                        if ((lookup_type == NF_TPROXY_LOOKUP_ESTABLISHED && (!connected || wildcard)) ||
                            (lookup_type == NF_TPROXY_LOOKUP_LISTENER && connected)) {
                                sock_put(sk);
                                sk = NULL;
                        }
                }
                break;
        default:
                WARN_ON(1);
                sk = NULL;
        }

        pr_debug("tproxy socket lookup: proto %u %pI6:%u -> %pI6:%u, lookup type: %d, sock %p\n",
                 protocol, saddr, ntohs(sport), daddr, ntohs(dport), lookup_type, sk);

        return sk;
}
EXPORT_SYMBOL_GPL(nf_tproxy_get_sock_v6);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs");
MODULE_DESCRIPTION("Netfilter IPv6 transparent proxy support");