// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2007-2008 BalaBit IT Ltd.
 * Author: Krisztian Kovacs
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/skbuff.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <net/icmp.h>
#include <net/sock.h>
#include <net/inet_sock.h>
#include <net/inet6_hashtables.h>
#include <net/netfilter/nf_socket.h>
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
#include <net/netfilter/nf_conntrack.h>
#endif

static int
extract_icmp6_fields(const struct sk_buff *skb,
                     unsigned int outside_hdrlen,
                     int *protocol,
                     const struct in6_addr **raddr,
                     const struct in6_addr **laddr,
                     __be16 *rport,
                     __be16 *lport,
                     struct ipv6hdr *ipv6_var)
{
        const struct ipv6hdr *inside_iph;
        struct icmp6hdr *icmph, _icmph;
        __be16 *ports, _ports[2];
        u8 inside_nexthdr;
        __be16 inside_fragoff;
        int inside_hdrlen;

        icmph = skb_header_pointer(skb, outside_hdrlen,
                                   sizeof(_icmph), &_icmph);
        if (icmph == NULL)
                return 1;

        if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK)
                return 1;

        inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph),
                                        sizeof(*ipv6_var), ipv6_var);
        if (inside_iph == NULL)
                return 1;
        inside_nexthdr = inside_iph->nexthdr;

        inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) +
                                              sizeof(*ipv6_var),
                                         &inside_nexthdr, &inside_fragoff);
        if (inside_hdrlen < 0)
                return 1; /* hjm: Packet has no/incomplete transport layer headers. */

        if (inside_nexthdr != IPPROTO_TCP &&
            inside_nexthdr != IPPROTO_UDP)
                return 1;

        ports = skb_header_pointer(skb, inside_hdrlen,
                                   sizeof(_ports), &_ports);
        if (ports == NULL)
                return 1;

        /* the inside IP packet is the one quoted from our side, thus
         * its saddr is the local address */
        *protocol = inside_nexthdr;
        *laddr = &inside_iph->saddr;
        *lport = ports[0];
        *raddr = &inside_iph->daddr;
        *rport = ports[1];

        return 0;
}

static struct sock *
nf_socket_get_sock_v6(struct net *net, struct sk_buff *skb, int doff,
                      const u8 protocol,
                      const struct in6_addr *saddr, const struct in6_addr *daddr,
                      const __be16 sport, const __be16 dport,
                      const struct net_device *in)
{
        switch (protocol) {
        case IPPROTO_TCP:
                return inet6_lookup(net, skb, doff, saddr, sport, daddr, dport,
                                    in->ifindex);
        case IPPROTO_UDP:
                return udp6_lib_lookup(net, saddr, sport, daddr, dport,
                                       in->ifindex);
        }

        return NULL;
}

struct sock *nf_sk_lookup_slow_v6(struct net *net, const struct sk_buff *skb,
                                  const struct net_device *indev)
{
        __be16 dport, sport;
        const struct in6_addr *daddr = NULL, *saddr = NULL;
        struct ipv6hdr *iph = ipv6_hdr(skb), ipv6_var;
        struct sk_buff *data_skb = NULL;
        int doff = 0;
        int thoff = 0, tproto;
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
        enum ip_conntrack_info ctinfo;
        struct nf_conn const *ct;
#endif

        tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
        if (tproto < 0) {
                pr_debug("unable to find transport header in IPv6 packet, dropping\n");
                return NULL;
        }

        if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) {
                struct tcphdr _hdr;
                struct udphdr *hp;

                hp = skb_header_pointer(skb, thoff, tproto == IPPROTO_UDP ?
                                        sizeof(*hp) : sizeof(_hdr), &_hdr);
                if (hp == NULL)
                        return NULL;

                saddr = &iph->saddr;
                sport = hp->source;
                daddr = &iph->daddr;
                dport = hp->dest;
                data_skb = (struct sk_buff *)skb;
                doff = tproto == IPPROTO_TCP ?
                        thoff + __tcp_hdrlen((struct tcphdr *)hp) :
                        thoff + sizeof(*hp);

        } else if (tproto == IPPROTO_ICMPV6) {
                if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr,
                                         &sport, &dport, &ipv6_var))
                        return NULL;
        } else {
                return NULL;
        }

#if IS_ENABLED(CONFIG_NF_CONNTRACK)
        /* Do the lookup with the original socket address in
         * case this is a reply packet of an established
         * SNAT-ted connection.
         */
        ct = nf_ct_get(skb, &ctinfo);
        if (ct &&
            ((tproto != IPPROTO_ICMPV6 &&
              ctinfo == IP_CT_ESTABLISHED_REPLY) ||
             (tproto == IPPROTO_ICMPV6 &&
              ctinfo == IP_CT_RELATED_REPLY)) &&
            (ct->status & IPS_SRC_NAT_DONE)) {
                daddr = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.in6;
                dport = (tproto == IPPROTO_TCP) ?
                        ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port :
                        ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
        }
#endif

        return nf_socket_get_sock_v6(net, data_skb, doff, tproto, saddr, daddr,
                                     sport, dport, indev);
}
EXPORT_SYMBOL_GPL(nf_sk_lookup_slow_v6);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
MODULE_DESCRIPTION("Netfilter IPv6 socket lookup infrastructure");