linux-brain/net/netfilter/nf_conntrack_proto_udp.c

// 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->net, state->pf,
			       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;

	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));

	if (!nf_ct_is_confirmed(ct))
		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 (test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
		unsigned long extra = timeouts[UDP_CT_UNREPLIED];

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

		nf_ct_refresh_acct(ct, ctinfo, skb, extra);

		/* 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;
}

#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->net, state->pf,
			       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]);
		/* 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];
}

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