// SPDX-License-Identifier: GPL-2.0-only
/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
 */

#include <linux/types.h>
#include <linux/timer.h>
#include <linux/module.h>
#include <linux/udp.h>
#include <linux/seq_file.h>
#include <linux/skbuff.h>
#include <linux/ipv6.h>
#include <net/ip6_checksum.h>
#include <net/checksum.h>

#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_ipv6.h>
#include <net/netfilter/nf_conntrack_l4proto.h>
#include <net/netfilter/nf_conntrack_ecache.h>
#include <net/netfilter/nf_conntrack_timeout.h>
#include <net/netfilter/nf_log.h>
#include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
#include <net/netfilter/ipv6/nf_conntrack_ipv6.h>

static const unsigned int udp_timeouts[UDP_CT_MAX] = {
        [UDP_CT_UNREPLIED]      = 30*HZ,
        [UDP_CT_REPLIED]        = 120*HZ,
};

static unsigned int *udp_get_timeouts(struct net *net)
{
        return nf_udp_pernet(net)->timeouts;
}

static void udp_error_log(const struct sk_buff *skb,
                          const struct nf_hook_state *state,
                          const char *msg)
{
        nf_l4proto_log_invalid(skb, state, IPPROTO_UDP, "%s", msg);
}

static bool udp_error(struct sk_buff *skb,
                      unsigned int dataoff,
                      const struct nf_hook_state *state)
{
        unsigned int udplen = skb->len - dataoff;
        const struct udphdr *hdr;
        struct udphdr _hdr;

        /* Header is too small? */
        hdr = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
        if (!hdr) {
                udp_error_log(skb, state, "short packet");
                return true;
        }

        /* Truncated/malformed packets */
        if (ntohs(hdr->len) > udplen || ntohs(hdr->len) < sizeof(*hdr)) {
                udp_error_log(skb, state, "truncated/malformed packet");
                return true;
        }

        /* Packet with no checksum */
        if (!hdr->check)
                return false;

        /* Checksum invalid? Ignore.
         * We skip checking packets on the outgoing path
         * because the checksum is assumed to be correct.
         * FIXME: Source route IP option packets --RR */
        if (state->hook == NF_INET_PRE_ROUTING &&
            state->net->ct.sysctl_checksum &&
            nf_checksum(skb, state->hook, dataoff, IPPROTO_UDP, state->pf)) {
                udp_error_log(skb, state, "bad checksum");
                return true;
        }

        return false;
}

/* Returns verdict for packet, and may modify conntracktype */
int nf_conntrack_udp_packet(struct nf_conn *ct,
                            struct sk_buff *skb,
                            unsigned int dataoff,
                            enum ip_conntrack_info ctinfo,
                            const struct nf_hook_state *state)
{
        unsigned int *timeouts;
        unsigned long status;

        if (udp_error(skb, dataoff, state))
                return -NF_ACCEPT;

        timeouts = nf_ct_timeout_lookup(ct);
        if (!timeouts)
                timeouts = udp_get_timeouts(nf_ct_net(ct));

        status = READ_ONCE(ct->status);
        if ((status & IPS_CONFIRMED) == 0)
                ct->proto.udp.stream_ts = 2 * HZ + jiffies;

        /* If we've seen traffic both ways, this is some kind of UDP
         * stream. Set Assured.
         */
        if (status & IPS_SEEN_REPLY) {
                unsigned long extra = timeouts[UDP_CT_UNREPLIED];
                bool stream = false;

                /* Still active after two seconds? Extend timeout. */
                if (time_after(jiffies, ct->proto.udp.stream_ts)) {
                        extra = timeouts[UDP_CT_REPLIED];
                        stream = (status & IPS_ASSURED) == 0;
                }

                nf_ct_refresh_acct(ct, ctinfo, skb, extra);

                /* never set ASSURED for IPS_NAT_CLASH, they time out soon */
                if (unlikely((status & IPS_NAT_CLASH)))
                        return NF_ACCEPT;

                /* Also, more likely to be important, and not a probe */
                if (stream && !test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
                        nf_conntrack_event_cache(IPCT_ASSURED, ct);
        } else {
                nf_ct_refresh_acct(ct, ctinfo, skb, timeouts[UDP_CT_UNREPLIED]);
        }
        return NF_ACCEPT;
}

#ifdef CONFIG_NF_CT_PROTO_UDPLITE
static void udplite_error_log(const struct sk_buff *skb,
                              const struct nf_hook_state *state,
                              const char *msg)
{
        nf_l4proto_log_invalid(skb, state, IPPROTO_UDPLITE, "%s", msg);
}

static bool udplite_error(struct sk_buff *skb,
                          unsigned int dataoff,
                          const struct nf_hook_state *state)
{
        unsigned int udplen = skb->len - dataoff;
        const struct udphdr *hdr;
        struct udphdr _hdr;
        unsigned int cscov;

        /* Header is too small? */
        hdr = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
        if (!hdr) {
                udplite_error_log(skb, state, "short packet");
                return true;
        }

        cscov = ntohs(hdr->len);
        if (cscov == 0) {
                cscov = udplen;
        } else if (cscov < sizeof(*hdr) || cscov > udplen) {
                udplite_error_log(skb, state, "invalid checksum coverage");
                return true;
        }

        /* UDPLITE mandates checksums */
        if (!hdr->check) {
                udplite_error_log(skb, state, "checksum missing");
                return true;
        }

        /* Checksum invalid? Ignore. */
        if (state->hook == NF_INET_PRE_ROUTING &&
            state->net->ct.sysctl_checksum &&
            nf_checksum_partial(skb, state->hook, dataoff, cscov, IPPROTO_UDP,
                                state->pf)) {
                udplite_error_log(skb, state, "bad checksum");
                return true;
        }

        return false;
}

/* Returns verdict for packet, and may modify conntracktype */
int nf_conntrack_udplite_packet(struct nf_conn *ct,
                                struct sk_buff *skb,
                                unsigned int dataoff,
                                enum ip_conntrack_info ctinfo,
                                const struct nf_hook_state *state)
{
        unsigned int *timeouts;

        if (udplite_error(skb, dataoff, state))
                return -NF_ACCEPT;

        timeouts = nf_ct_timeout_lookup(ct);
        if (!timeouts)
                timeouts = udp_get_timeouts(nf_ct_net(ct));

        /* If we've seen traffic both ways, this is some kind of UDP
           stream.  Extend timeout. */
        if (test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
                nf_ct_refresh_acct(ct, ctinfo, skb,
                                   timeouts[UDP_CT_REPLIED]);

                if (unlikely((ct->status & IPS_NAT_CLASH)))
                        return NF_ACCEPT;

                /* Also, more likely to be important, and not a probe */
                if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
                        nf_conntrack_event_cache(IPCT_ASSURED, ct);
        } else {
                nf_ct_refresh_acct(ct, ctinfo, skb, timeouts[UDP_CT_UNREPLIED]);
        }
        return NF_ACCEPT;
}
#endif

#ifdef CONFIG_NF_CONNTRACK_TIMEOUT

#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nfnetlink_cttimeout.h>

static int udp_timeout_nlattr_to_obj(struct nlattr *tb[],
                                     struct net *net, void *data)
{
        unsigned int *timeouts = data;
        struct nf_udp_net *un = nf_udp_pernet(net);

        if (!timeouts)
                timeouts = un->timeouts;

        /* set default timeouts for UDP. */
        timeouts[UDP_CT_UNREPLIED] = un->timeouts[UDP_CT_UNREPLIED];
        timeouts[UDP_CT_REPLIED] = un->timeouts[UDP_CT_REPLIED];

        if (tb[CTA_TIMEOUT_UDP_UNREPLIED]) {
                timeouts[UDP_CT_UNREPLIED] =
                        ntohl(nla_get_be32(tb[CTA_TIMEOUT_UDP_UNREPLIED])) * HZ;
        }
        if (tb[CTA_TIMEOUT_UDP_REPLIED]) {
                timeouts[UDP_CT_REPLIED] =
                        ntohl(nla_get_be32(tb[CTA_TIMEOUT_UDP_REPLIED])) * HZ;
        }
        return 0;
}

static int
udp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
{
        const unsigned int *timeouts = data;

        if (nla_put_be32(skb, CTA_TIMEOUT_UDP_UNREPLIED,
                         htonl(timeouts[UDP_CT_UNREPLIED] / HZ)) ||
            nla_put_be32(skb, CTA_TIMEOUT_UDP_REPLIED,
                         htonl(timeouts[UDP_CT_REPLIED] / HZ)))
                goto nla_put_failure;
        return 0;

nla_put_failure:
        return -ENOSPC;
}

static const struct nla_policy
udp_timeout_nla_policy[CTA_TIMEOUT_UDP_MAX+1] = {
       [CTA_TIMEOUT_UDP_UNREPLIED]      = { .type = NLA_U32 },
       [CTA_TIMEOUT_UDP_REPLIED]        = { .type = NLA_U32 },
};
#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */

void nf_conntrack_udp_init_net(struct net *net)
{
        struct nf_udp_net *un = nf_udp_pernet(net);
        int i;

        for (i = 0; i < UDP_CT_MAX; i++)
                un->timeouts[i] = udp_timeouts[i];

#if IS_ENABLED(CONFIG_NF_FLOW_TABLE)
        un->offload_timeout = 30 * HZ;
#endif
}

const struct nf_conntrack_l4proto nf_conntrack_l4proto_udp =
{
        .l4proto                = IPPROTO_UDP,
        .allow_clash            = true,
#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
        .tuple_to_nlattr        = nf_ct_port_tuple_to_nlattr,
        .nlattr_to_tuple        = nf_ct_port_nlattr_to_tuple,
        .nlattr_tuple_size      = nf_ct_port_nlattr_tuple_size,
        .nla_policy             = nf_ct_port_nla_policy,
#endif
#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
        .ctnl_timeout           = {
                .nlattr_to_obj  = udp_timeout_nlattr_to_obj,
                .obj_to_nlattr  = udp_timeout_obj_to_nlattr,
                .nlattr_max     = CTA_TIMEOUT_UDP_MAX,
                .obj_size       = sizeof(unsigned int) * CTA_TIMEOUT_UDP_MAX,
                .nla_policy     = udp_timeout_nla_policy,
        },
#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
};

#ifdef CONFIG_NF_CT_PROTO_UDPLITE
const struct nf_conntrack_l4proto nf_conntrack_l4proto_udplite =
{
        .l4proto                = IPPROTO_UDPLITE,
        .allow_clash            = true,
#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
        .tuple_to_nlattr        = nf_ct_port_tuple_to_nlattr,
        .nlattr_to_tuple        = nf_ct_port_nlattr_to_tuple,
        .nlattr_tuple_size      = nf_ct_port_nlattr_tuple_size,
        .nla_policy             = nf_ct_port_nla_policy,
#endif
#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
        .ctnl_timeout           = {
                .nlattr_to_obj  = udp_timeout_nlattr_to_obj,
                .obj_to_nlattr  = udp_timeout_obj_to_nlattr,
                .nlattr_max     = CTA_TIMEOUT_UDP_MAX,
                .obj_size       = sizeof(unsigned int) * CTA_TIMEOUT_UDP_MAX,
                .nla_policy     = udp_timeout_nla_policy,
        },
#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
};
#endif