/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#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_log.h>
#include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
#include <net/netfilter/ipv6/nf_conntrack_ipv6.h>

static unsigned int nf_ct_udp_timeout __read_mostly = 30*HZ;
static unsigned int nf_ct_udp_timeout_stream __read_mostly = 180*HZ;

static bool udp_pkt_to_tuple(const struct sk_buff *skb,
                             unsigned int dataoff,
                             struct nf_conntrack_tuple *tuple)
{
        const struct udphdr *hp;
        struct udphdr _hdr;

        /* Actually only need first 8 bytes. */
        hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
        if (hp == NULL)
                return false;

        tuple->src.u.udp.port = hp->source;
        tuple->dst.u.udp.port = hp->dest;

        return true;
}

static bool udp_invert_tuple(struct nf_conntrack_tuple *tuple,
                             const struct nf_conntrack_tuple *orig)
{
        tuple->src.u.udp.port = orig->dst.u.udp.port;
        tuple->dst.u.udp.port = orig->src.u.udp.port;
        return true;
}

/* Print out the per-protocol part of the tuple. */
static int udp_print_tuple(struct seq_file *s,
                           const struct nf_conntrack_tuple *tuple)
{
        return seq_printf(s, "sport=%hu dport=%hu ",
                          ntohs(tuple->src.u.udp.port),
                          ntohs(tuple->dst.u.udp.port));
}

/* Returns verdict for packet, and may modify conntracktype */
static int udp_packet(struct nf_conn *ct,
                      const struct sk_buff *skb,
                      unsigned int dataoff,
                      enum ip_conntrack_info ctinfo,
                      u_int8_t pf,
                      unsigned int hooknum)
{
        /* 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, nf_ct_udp_timeout_stream);
                /* 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, nf_ct_udp_timeout);

        return NF_ACCEPT;
}

/* Called when a new connection for this protocol found. */
static bool udp_new(struct nf_conn *ct, const struct sk_buff *skb,
                    unsigned int dataoff)
{
        return true;
}

static int udp_error(struct net *net, struct nf_conn *tmpl, struct sk_buff *skb,
                     unsigned int dataoff, enum ip_conntrack_info *ctinfo,
                     u_int8_t pf,
                     unsigned int hooknum)
{
        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 == NULL) {
                if (LOG_INVALID(net, IPPROTO_UDP))
                        nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
                                      "nf_ct_udp: short packet ");
                return -NF_ACCEPT;
        }

        /* Truncated/malformed packets */
        if (ntohs(hdr->len) > udplen || ntohs(hdr->len) < sizeof(*hdr)) {
                if (LOG_INVALID(net, IPPROTO_UDP))
                        nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
                                "nf_ct_udp: truncated/malformed packet ");
                return -NF_ACCEPT;
        }

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

        /* 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 (net->ct.sysctl_checksum && hooknum == NF_INET_PRE_ROUTING &&
            nf_checksum(skb, hooknum, dataoff, IPPROTO_UDP, pf)) {
                if (LOG_INVALID(net, IPPROTO_UDP))
                        nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
                                "nf_ct_udp: bad UDP checksum ");
                return -NF_ACCEPT;
        }

        return NF_ACCEPT;
}

#ifdef CONFIG_SYSCTL
static unsigned int udp_sysctl_table_users;
static struct ctl_table_header *udp_sysctl_header;
static struct ctl_table udp_sysctl_table[] = {
        {
                .procname       = "nf_conntrack_udp_timeout",
                .data           = &nf_ct_udp_timeout,
                .maxlen         = sizeof(unsigned int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_jiffies,
        },
        {
                .procname       = "nf_conntrack_udp_timeout_stream",
                .data           = &nf_ct_udp_timeout_stream,
                .maxlen         = sizeof(unsigned int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_jiffies,
        },
        { }
};
#ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
static struct ctl_table udp_compat_sysctl_table[] = {
        {
                .procname       = "ip_conntrack_udp_timeout",
                .data           = &nf_ct_udp_timeout,
                .maxlen         = sizeof(unsigned int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_jiffies,
        },
        {
                .procname       = "ip_conntrack_udp_timeout_stream",
                .data           = &nf_ct_udp_timeout_stream,
                .maxlen         = sizeof(unsigned int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_jiffies,
        },
        { }
};
#endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */
#endif /* CONFIG_SYSCTL */

struct nf_conntrack_l4proto nf_conntrack_l4proto_udp4 __read_mostly =
{
        .l3proto                = PF_INET,
        .l4proto                = IPPROTO_UDP,
        .name                   = "udp",
        .pkt_to_tuple           = udp_pkt_to_tuple,
        .invert_tuple           = udp_invert_tuple,
        .print_tuple            = udp_print_tuple,
        .packet                 = udp_packet,
        .new                    = udp_new,
        .error                  = udp_error,
#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_SYSCTL
        .ctl_table_users        = &udp_sysctl_table_users,
        .ctl_table_header       = &udp_sysctl_header,
        .ctl_table              = udp_sysctl_table,
#ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
        .ctl_compat_table       = udp_compat_sysctl_table,
#endif
#endif
};
EXPORT_SYMBOL_GPL(nf_conntrack_l4proto_udp4);

struct nf_conntrack_l4proto nf_conntrack_l4proto_udp6 __read_mostly =
{
        .l3proto                = PF_INET6,
        .l4proto                = IPPROTO_UDP,
        .name                   = "udp",
        .pkt_to_tuple           = udp_pkt_to_tuple,
        .invert_tuple           = udp_invert_tuple,
        .print_tuple            = udp_print_tuple,
        .packet                 = udp_packet,
        .new                    = udp_new,
        .error                  = udp_error,
#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_SYSCTL
        .ctl_table_users        = &udp_sysctl_table_users,
        .ctl_table_header       = &udp_sysctl_header,
        .ctl_table              = udp_sysctl_table,
#endif
};
EXPORT_SYMBOL_GPL(nf_conntrack_l4proto_udp6);