linux-next/net/openvswitch/conntrack.c

/*
 * Copyright (c) 2015 Nicira, Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 */

#include <linux/module.h>
#include <linux/openvswitch.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/sctp.h>
#include <net/ip.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_labels.h>
#include <net/netfilter/nf_conntrack_seqadj.h>
#include <net/netfilter/nf_conntrack_zones.h>
#include <net/netfilter/ipv6/nf_defrag_ipv6.h>

#ifdef CONFIG_NF_NAT_NEEDED
#include <linux/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_core.h>
#include <net/netfilter/nf_nat_l3proto.h>
#endif

#include "datapath.h"
#include "conntrack.h"
#include "flow.h"
#include "flow_netlink.h"

struct ovs_ct_len_tbl {
	int maxlen;
	int minlen;
};

/* Metadata mark for masked write to conntrack mark */
struct md_mark {
	u32 value;
	u32 mask;
};

/* Metadata label for masked write to conntrack label. */
struct md_labels {
	struct ovs_key_ct_labels value;
	struct ovs_key_ct_labels mask;
};

enum ovs_ct_nat {
	OVS_CT_NAT = 1 << 0,     /* NAT for committed connections only. */
	OVS_CT_SRC_NAT = 1 << 1, /* Source NAT for NEW connections. */
	OVS_CT_DST_NAT = 1 << 2, /* Destination NAT for NEW connections. */
};

/* Conntrack action context for execution. */
struct ovs_conntrack_info {
	struct nf_conntrack_helper *helper;
	struct nf_conntrack_zone zone;
	struct nf_conn *ct;
	u8 commit : 1;
	u8 nat : 3;                 /* enum ovs_ct_nat */
	u16 family;
	struct md_mark mark;
	struct md_labels labels;
#ifdef CONFIG_NF_NAT_NEEDED
	struct nf_nat_range range;  /* Only present for SRC NAT and DST NAT. */
#endif
};

static void __ovs_ct_free_action(struct ovs_conntrack_info *ct_info);

static u16 key_to_nfproto(const struct sw_flow_key *key)
{
	switch (ntohs(key->eth.type)) {
	case ETH_P_IP:
		return NFPROTO_IPV4;
	case ETH_P_IPV6:
		return NFPROTO_IPV6;
	default:
		return NFPROTO_UNSPEC;
	}
}

/* Map SKB connection state into the values used by flow definition. */
static u8 ovs_ct_get_state(enum ip_conntrack_info ctinfo)
{
	u8 ct_state = OVS_CS_F_TRACKED;

	switch (ctinfo) {
	case IP_CT_ESTABLISHED_REPLY:
	case IP_CT_RELATED_REPLY:
		ct_state |= OVS_CS_F_REPLY_DIR;
		break;
	default:
		break;
	}

	switch (ctinfo) {
	case IP_CT_ESTABLISHED:
	case IP_CT_ESTABLISHED_REPLY:
		ct_state |= OVS_CS_F_ESTABLISHED;
		break;
	case IP_CT_RELATED:
	case IP_CT_RELATED_REPLY:
		ct_state |= OVS_CS_F_RELATED;
		break;
	case IP_CT_NEW:
		ct_state |= OVS_CS_F_NEW;
		break;
	default:
		break;
	}

	return ct_state;
}

static u32 ovs_ct_get_mark(const struct nf_conn *ct)
{
#if IS_ENABLED(CONFIG_NF_CONNTRACK_MARK)
	return ct ? ct->mark : 0;
#else
	return 0;
#endif
}

static void ovs_ct_get_labels(const struct nf_conn *ct,
			      struct ovs_key_ct_labels *labels)
{
	struct nf_conn_labels *cl = ct ? nf_ct_labels_find(ct) : NULL;

	if (cl) {
		size_t len = sizeof(cl->bits);

		if (len > OVS_CT_LABELS_LEN)
			len = OVS_CT_LABELS_LEN;
		else if (len < OVS_CT_LABELS_LEN)
			memset(labels, 0, OVS_CT_LABELS_LEN);
		memcpy(labels, cl->bits, len);
	} else {
		memset(labels, 0, OVS_CT_LABELS_LEN);
	}
}

static void __ovs_ct_update_key(struct sw_flow_key *key, u8 state,
				const struct nf_conntrack_zone *zone,
				const struct nf_conn *ct)
{
	key->ct.state = state;
	key->ct.zone = zone->id;
	key->ct.mark = ovs_ct_get_mark(ct);
	ovs_ct_get_labels(ct, &key->ct.labels);
}

/* Update 'key' based on skb->nfct.  If 'post_ct' is true, then OVS has
 * previously sent the packet to conntrack via the ct action.  If
 * 'keep_nat_flags' is true, the existing NAT flags retained, else they are
 * initialized from the connection status.
 */
static void ovs_ct_update_key(const struct sk_buff *skb,
			      const struct ovs_conntrack_info *info,
			      struct sw_flow_key *key, bool post_ct,
			      bool keep_nat_flags)
{
	const struct nf_conntrack_zone *zone = &nf_ct_zone_dflt;
	enum ip_conntrack_info ctinfo;
	struct nf_conn *ct;
	u8 state = 0;

	ct = nf_ct_get(skb, &ctinfo);
	if (ct) {
		state = ovs_ct_get_state(ctinfo);
		/* All unconfirmed entries are NEW connections. */
		if (!nf_ct_is_confirmed(ct))
			state |= OVS_CS_F_NEW;
		/* OVS persists the related flag for the duration of the
		 * connection.
		 */
		if (ct->master)
			state |= OVS_CS_F_RELATED;
		if (keep_nat_flags) {
			state |= key->ct.state & OVS_CS_F_NAT_MASK;
		} else {
			if (ct->status & IPS_SRC_NAT)
				state |= OVS_CS_F_SRC_NAT;
			if (ct->status & IPS_DST_NAT)
				state |= OVS_CS_F_DST_NAT;
		}
		zone = nf_ct_zone(ct);
	} else if (post_ct) {
		state = OVS_CS_F_TRACKED | OVS_CS_F_INVALID;
		if (info)
			zone = &info->zone;
	}
	__ovs_ct_update_key(key, state, zone, ct);
}

/* This is called to initialize CT key fields possibly coming in from the local
 * stack.
 */
void ovs_ct_fill_key(const struct sk_buff *skb, struct sw_flow_key *key)
{
	ovs_ct_update_key(skb, NULL, key, false, false);
}

int ovs_ct_put_key(const struct sw_flow_key *key, struct sk_buff *skb)
{
	if (nla_put_u32(skb, OVS_KEY_ATTR_CT_STATE, key->ct.state))
		return -EMSGSIZE;

	if (IS_ENABLED(CONFIG_NF_CONNTRACK_ZONES) &&
	    nla_put_u16(skb, OVS_KEY_ATTR_CT_ZONE, key->ct.zone))
		return -EMSGSIZE;

	if (IS_ENABLED(CONFIG_NF_CONNTRACK_MARK) &&
	    nla_put_u32(skb, OVS_KEY_ATTR_CT_MARK, key->ct.mark))
		return -EMSGSIZE;

	if (IS_ENABLED(CONFIG_NF_CONNTRACK_LABELS) &&
	    nla_put(skb, OVS_KEY_ATTR_CT_LABELS, sizeof(key->ct.labels),
		    &key->ct.labels))
		return -EMSGSIZE;

	return 0;
}

static int ovs_ct_set_mark(struct sk_buff *skb, struct sw_flow_key *key,
			   u32 ct_mark, u32 mask)
{
#if IS_ENABLED(CONFIG_NF_CONNTRACK_MARK)
	enum ip_conntrack_info ctinfo;
	struct nf_conn *ct;
	u32 new_mark;

	/* The connection could be invalid, in which case set_mark is no-op. */
	ct = nf_ct_get(skb, &ctinfo);
	if (!ct)
		return 0;

	new_mark = ct_mark | (ct->mark & ~(mask));
	if (ct->mark != new_mark) {
		ct->mark = new_mark;
		nf_conntrack_event_cache(IPCT_MARK, ct);
		key->ct.mark = new_mark;
	}

	return 0;
#else
	return -ENOTSUPP;
#endif
}

static int ovs_ct_set_labels(struct sk_buff *skb, struct sw_flow_key *key,
			     const struct ovs_key_ct_labels *labels,
			     const struct ovs_key_ct_labels *mask)
{
	enum ip_conntrack_info ctinfo;
	struct nf_conn_labels *cl;
	struct nf_conn *ct;
	int err;

	/* The connection could be invalid, in which case set_label is no-op.*/
	ct = nf_ct_get(skb, &ctinfo);
	if (!ct)
		return 0;

	cl = nf_ct_labels_find(ct);
	if (!cl) {
		nf_ct_labels_ext_add(ct);
		cl = nf_ct_labels_find(ct);
	}
	if (!cl || sizeof(cl->bits) < OVS_CT_LABELS_LEN)
		return -ENOSPC;

	err = nf_connlabels_replace(ct, (u32 *)labels, (u32 *)mask,
				    OVS_CT_LABELS_LEN / sizeof(u32));
	if (err)
		return err;

	ovs_ct_get_labels(ct, &key->ct.labels);
	return 0;
}

/* 'skb' should already be pulled to nh_ofs. */
static int ovs_ct_helper(struct sk_buff *skb, u16 proto)
{
	const struct nf_conntrack_helper *helper;
	const struct nf_conn_help *help;
	enum ip_conntrack_info ctinfo;
	unsigned int protoff;
	struct nf_conn *ct;
	int err;

	ct = nf_ct_get(skb, &ctinfo);
	if (!ct || ctinfo == IP_CT_RELATED_REPLY)
		return NF_ACCEPT;

	help = nfct_help(ct);
	if (!help)
		return NF_ACCEPT;

	helper = rcu_dereference(help->helper);
	if (!helper)
		return NF_ACCEPT;

	switch (proto) {
	case NFPROTO_IPV4:
		protoff = ip_hdrlen(skb);
		break;
	case NFPROTO_IPV6: {
		u8 nexthdr = ipv6_hdr(skb)->nexthdr;
		__be16 frag_off;
		int ofs;

		ofs = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &nexthdr,
				       &frag_off);
		if (ofs < 0 || (frag_off & htons(~0x7)) != 0) {
			pr_debug("proto header not found\n");
			return NF_ACCEPT;
		}
		protoff = ofs;
		break;
	}
	default:
		WARN_ONCE(1, "helper invoked on non-IP family!");
		return NF_DROP;
	}

	err = helper->help(skb, protoff, ct, ctinfo);
	if (err != NF_ACCEPT)
		return err;

	/* Adjust seqs after helper.  This is needed due to some helpers (e.g.,
	 * FTP with NAT) adusting the TCP payload size when mangling IP
	 * addresses and/or port numbers in the text-based control connection.
	 */
	if (test_bit(IPS_SEQ_ADJUST_BIT, &ct->status) &&
	    !nf_ct_seq_adjust(skb, ct, ctinfo, protoff))
		return NF_DROP;
	return NF_ACCEPT;
}

/* Returns 0 on success, -EINPROGRESS if 'skb' is stolen, or other nonzero
 * value if 'skb' is freed.
 */
static int handle_fragments(struct net *net, struct sw_flow_key *key,
			    u16 zone, struct sk_buff *skb)
{
	struct ovs_skb_cb ovs_cb = *OVS_CB(skb);
	int err;

	if (key->eth.type == htons(ETH_P_IP)) {
		enum ip_defrag_users user = IP_DEFRAG_CONNTRACK_IN + zone;

		memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
		err = ip_defrag(net, skb, user);
		if (err)
			return err;

		ovs_cb.mru = IPCB(skb)->frag_max_size;
#if IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
	} else if (key->eth.type == htons(ETH_P_IPV6)) {
		enum ip6_defrag_users user = IP6_DEFRAG_CONNTRACK_IN + zone;

		skb_orphan(skb);
		memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
		err = nf_ct_frag6_gather(net, skb, user);
		if (err)
			return err;

		key->ip.proto = ipv6_hdr(skb)->nexthdr;
		ovs_cb.mru = IP6CB(skb)->frag_max_size;
#endif
	} else {
		kfree_skb(skb);
		return -EPFNOSUPPORT;
	}

	key->ip.frag = OVS_FRAG_TYPE_NONE;
	skb_clear_hash(skb);
	skb->ignore_df = 1;
	*OVS_CB(skb) = ovs_cb;

	return 0;
}

static struct nf_conntrack_expect *
ovs_ct_expect_find(struct net *net, const struct nf_conntrack_zone *zone,
		   u16 proto, const struct sk_buff *skb)
{
	struct nf_conntrack_tuple tuple;

	if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb), proto, net, &tuple))
		return NULL;
	return __nf_ct_expect_find(net, zone, &tuple);
}

/* This replicates logic from nf_conntrack_core.c that is not exported. */
static enum ip_conntrack_info
ovs_ct_get_info(const struct nf_conntrack_tuple_hash *h)
{
	const struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);

	if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
		return IP_CT_ESTABLISHED_REPLY;
	/* Once we've had two way comms, always ESTABLISHED. */
	if (test_bit(IPS_SEEN_REPLY_BIT, &ct->status))
		return IP_CT_ESTABLISHED;
	if (test_bit(IPS_EXPECTED_BIT, &ct->status))
		return IP_CT_RELATED;
	return IP_CT_NEW;
}

/* Find an existing connection which this packet belongs to without
 * re-attributing statistics or modifying the connection state.  This allows an
 * skb->nfct lost due to an upcall to be recovered during actions execution.
 *
 * Must be called with rcu_read_lock.
 *
 * On success, populates skb->nfct and skb->nfctinfo, and returns the
 * connection.  Returns NULL if there is no existing entry.
 */
static struct nf_conn *
ovs_ct_find_existing(struct net *net, const struct nf_conntrack_zone *zone,
		     u8 l3num, struct sk_buff *skb)
{
	struct nf_conntrack_l3proto *l3proto;
	struct nf_conntrack_l4proto *l4proto;
	struct nf_conntrack_tuple tuple;
	struct nf_conntrack_tuple_hash *h;
	struct nf_conn *ct;
	unsigned int dataoff;
	u8 protonum;

	l3proto = __nf_ct_l3proto_find(l3num);
	if (l3proto->get_l4proto(skb, skb_network_offset(skb), &dataoff,
				 &protonum) <= 0) {
		pr_debug("ovs_ct_find_existing: Can't get protonum\n");
		return NULL;
	}
	l4proto = __nf_ct_l4proto_find(l3num, protonum);
	if (!nf_ct_get_tuple(skb, skb_network_offset(skb), dataoff, l3num,
			     protonum, net, &tuple, l3proto, l4proto)) {
		pr_debug("ovs_ct_find_existing: Can't get tuple\n");
		return NULL;
	}

	/* look for tuple match */
	h = nf_conntrack_find_get(net, zone, &tuple);
	if (!h)
		return NULL;   /* Not found. */

	ct = nf_ct_tuplehash_to_ctrack(h);

	skb->nfct = &ct->ct_general;
	skb->nfctinfo = ovs_ct_get_info(h);
	return ct;
}

/* Determine whether skb->nfct is equal to the result of conntrack lookup. */
static bool skb_nfct_cached(struct net *net,
			    const struct sw_flow_key *key,
			    const struct ovs_conntrack_info *info,
			    struct sk_buff *skb)
{
	enum ip_conntrack_info ctinfo;
	struct nf_conn *ct;

	ct = nf_ct_get(skb, &ctinfo);
	/* If no ct, check if we have evidence that an existing conntrack entry
	 * might be found for this skb.  This happens when we lose a skb->nfct
	 * due to an upcall.  If the connection was not confirmed, it is not
	 * cached and needs to be run through conntrack again.
	 */
	if (!ct && key->ct.state & OVS_CS_F_TRACKED &&
	    !(key->ct.state & OVS_CS_F_INVALID) &&
	    key->ct.zone == info->zone.id)
		ct = ovs_ct_find_existing(net, &info->zone, info->family, skb);
	if (!ct)
		return false;
	if (!net_eq(net, read_pnet(&ct->ct_net)))
		return false;
	if (!nf_ct_zone_equal_any(info->ct, nf_ct_zone(ct)))
		return false;
	if (info->helper) {
		struct nf_conn_help *help;

		help = nf_ct_ext_find(ct, NF_CT_EXT_HELPER);
		if (help && rcu_access_pointer(help->helper) != info->helper)
			return false;
	}

	return true;
}

#ifdef CONFIG_NF_NAT_NEEDED
/* Modelled after nf_nat_ipv[46]_fn().
 * range is only used for new, uninitialized NAT state.
 * Returns either NF_ACCEPT or NF_DROP.
 */
static int ovs_ct_nat_execute(struct sk_buff *skb, struct nf_conn *ct,
			      enum ip_conntrack_info ctinfo,
			      const struct nf_nat_range *range,
			      enum nf_nat_manip_type maniptype)
{
	int hooknum, nh_off, err = NF_ACCEPT;

	nh_off = skb_network_offset(skb);
	skb_pull(skb, nh_off);

	/* See HOOK2MANIP(). */
	if (maniptype == NF_NAT_MANIP_SRC)
		hooknum = NF_INET_LOCAL_IN; /* Source NAT */
	else
		hooknum = NF_INET_LOCAL_OUT; /* Destination NAT */

	switch (ctinfo) {
	case IP_CT_RELATED:
	case IP_CT_RELATED_REPLY:
		if (IS_ENABLED(CONFIG_NF_NAT_IPV4) &&
		    skb->protocol == htons(ETH_P_IP) &&
		    ip_hdr(skb)->protocol == IPPROTO_ICMP) {
			if (!nf_nat_icmp_reply_translation(skb, ct, ctinfo,
							   hooknum))
				err = NF_DROP;
			goto push;
		} else if (IS_ENABLED(CONFIG_NF_NAT_IPV6) &&
			   skb->protocol == htons(ETH_P_IPV6)) {
			__be16 frag_off;
			u8 nexthdr = ipv6_hdr(skb)->nexthdr;
			int hdrlen = ipv6_skip_exthdr(skb,
						      sizeof(struct ipv6hdr),
						      &nexthdr, &frag_off);

			if (hdrlen >= 0 && nexthdr == IPPROTO_ICMPV6) {
				if (!nf_nat_icmpv6_reply_translation(skb, ct,
								     ctinfo,
								     hooknum,
								     hdrlen))
					err = NF_DROP;
				goto push;
			}
		}
		/* Non-ICMP, fall thru to initialize if needed. */
	case IP_CT_NEW:
		/* Seen it before?  This can happen for loopback, retrans,
		 * or local packets.
		 */
		if (!nf_nat_initialized(ct, maniptype)) {
			/* Initialize according to the NAT action. */
			err = (range && range->flags & NF_NAT_RANGE_MAP_IPS)
				/* Action is set up to establish a new
				 * mapping.
				 */
				? nf_nat_setup_info(ct, range, maniptype)
				: nf_nat_alloc_null_binding(ct, hooknum);
			if (err != NF_ACCEPT)
				goto push;
		}
		break;

	case IP_CT_ESTABLISHED:
	case IP_CT_ESTABLISHED_REPLY:
		break;

	default:
		err = NF_DROP;
		goto push;
	}

	err = nf_nat_packet(ct, ctinfo, hooknum, skb);
push:
	skb_push(skb, nh_off);

	return err;
}

static void ovs_nat_update_key(struct sw_flow_key *key,
			       const struct sk_buff *skb,
			       enum nf_nat_manip_type maniptype)
{
	if (maniptype == NF_NAT_MANIP_SRC) {
		__be16 src;

		key->ct.state |= OVS_CS_F_SRC_NAT;
		if (key->eth.type == htons(ETH_P_IP))
			key->ipv4.addr.src = ip_hdr(skb)->saddr;
		else if (key->eth.type == htons(ETH_P_IPV6))
			memcpy(&key->ipv6.addr.src, &ipv6_hdr(skb)->saddr,
			       sizeof(key->ipv6.addr.src));
		else
			return;

		if (key->ip.proto == IPPROTO_UDP)
			src = udp_hdr(skb)->source;
		else if (key->ip.proto == IPPROTO_TCP)
			src = tcp_hdr(skb)->source;
		else if (key->ip.proto == IPPROTO_SCTP)
			src = sctp_hdr(skb)->source;
		else
			return;

		key->tp.src = src;
	} else {
		__be16 dst;

		key->ct.state |= OVS_CS_F_DST_NAT;
		if (key->eth.type == htons(ETH_P_IP))
			key->ipv4.addr.dst = ip_hdr(skb)->daddr;
		else if (key->eth.type == htons(ETH_P_IPV6))
			memcpy(&key->ipv6.addr.dst, &ipv6_hdr(skb)->daddr,
			       sizeof(key->ipv6.addr.dst));
		else
			return;

		if (key->ip.proto == IPPROTO_UDP)
			dst = udp_hdr(skb)->dest;
		else if (key->ip.proto == IPPROTO_TCP)
			dst = tcp_hdr(skb)->dest;
		else if (key->ip.proto == IPPROTO_SCTP)
			dst = sctp_hdr(skb)->dest;
		else
			return;

		key->tp.dst = dst;
	}
}

/* Returns NF_DROP if the packet should be dropped, NF_ACCEPT otherwise. */
static int ovs_ct_nat(struct net *net, struct sw_flow_key *key,
		      const struct ovs_conntrack_info *info,
		      struct sk_buff *skb, struct nf_conn *ct,
		      enum ip_conntrack_info ctinfo)
{
	enum nf_nat_manip_type maniptype;
	int err;

	if (nf_ct_is_untracked(ct)) {
		/* A NAT action may only be performed on tracked packets. */
		return NF_ACCEPT;
	}

	/* Add NAT extension if not confirmed yet. */
	if (!nf_ct_is_confirmed(ct) && !nf_ct_nat_ext_add(ct))
		return NF_ACCEPT;   /* Can't NAT. */

	/* Determine NAT type.
	 * Check if the NAT type can be deduced from the tracked connection.
	 * Make sure new expected connections (IP_CT_RELATED) are NATted only
	 * when committing.
	 */
	if (info->nat & OVS_CT_NAT && ctinfo != IP_CT_NEW &&
	    ct->status & IPS_NAT_MASK &&
	    (ctinfo != IP_CT_RELATED || info->commit)) {
		/* NAT an established or related connection like before. */
		if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY)
			/* This is the REPLY direction for a connection
			 * for which NAT was applied in the forward
			 * direction.  Do the reverse NAT.
			 */
			maniptype = ct->status & IPS_SRC_NAT
				? NF_NAT_MANIP_DST : NF_NAT_MANIP_SRC;
		else
			maniptype = ct->status & IPS_SRC_NAT
				? NF_NAT_MANIP_SRC : NF_NAT_MANIP_DST;
	} else if (info->nat & OVS_CT_SRC_NAT) {
		maniptype = NF_NAT_MANIP_SRC;
	} else if (info->nat & OVS_CT_DST_NAT) {
		maniptype = NF_NAT_MANIP_DST;
	} else {
		return NF_ACCEPT; /* Connection is not NATed. */
	}
	err = ovs_ct_nat_execute(skb, ct, ctinfo, &info->range, maniptype);

	/* Mark NAT done if successful and update the flow key. */
	if (err == NF_ACCEPT)
		ovs_nat_update_key(key, skb, maniptype);

	return err;
}
#else /* !CONFIG_NF_NAT_NEEDED */
static int ovs_ct_nat(struct net *net, struct sw_flow_key *key,
		      const struct ovs_conntrack_info *info,
		      struct sk_buff *skb, struct nf_conn *ct,
		      enum ip_conntrack_info ctinfo)
{
	return NF_ACCEPT;
}
#endif

/* Pass 'skb' through conntrack in 'net', using zone configured in 'info', if
 * not done already.  Update key with new CT state after passing the packet
 * through conntrack.
 * Note that if the packet is deemed invalid by conntrack, skb->nfct will be
 * set to NULL and 0 will be returned.
 */
static int __ovs_ct_lookup(struct net *net, struct sw_flow_key *key,
			   const struct ovs_conntrack_info *info,
			   struct sk_buff *skb)
{
	/* If we are recirculating packets to match on conntrack fields and
	 * committing with a separate conntrack action,  then we don't need to
	 * actually run the packet through conntrack twice unless it's for a
	 * different zone.
	 */
	bool cached = skb_nfct_cached(net, key, info, skb);
	enum ip_conntrack_info ctinfo;
	struct nf_conn *ct;

	if (!cached) {
		struct nf_conn *tmpl = info->ct;
		int err;

		/* Associate skb with specified zone. */
		if (tmpl) {
			if (skb->nfct)
				nf_conntrack_put(skb->nfct);
			nf_conntrack_get(&tmpl->ct_general);
			skb->nfct = &tmpl->ct_general;
			skb->nfctinfo = IP_CT_NEW;
		}

		/* Repeat if requested, see nf_iterate(). */
		do {
			err = nf_conntrack_in(net, info->family,
					      NF_INET_PRE_ROUTING, skb);
		} while (err == NF_REPEAT);

		if (err != NF_ACCEPT)
			return -ENOENT;

		/* Clear CT state NAT flags to mark that we have not yet done
		 * NAT after the nf_conntrack_in() call.  We can actually clear
		 * the whole state, as it will be re-initialized below.
		 */
		key->ct.state = 0;

		/* Update the key, but keep the NAT flags. */
		ovs_ct_update_key(skb, info, key, true, true);
	}

	ct = nf_ct_get(skb, &ctinfo);
	if (ct) {
		/* Packets starting a new connection must be NATted before the
		 * helper, so that the helper knows about the NAT.  We enforce
		 * this by delaying both NAT and helper calls for unconfirmed
		 * connections until the committing CT action.  For later
		 * packets NAT and Helper may be called in either order.
		 *
		 * NAT will be done only if the CT action has NAT, and only
		 * once per packet (per zone), as guarded by the NAT bits in
		 * the key->ct.state.
		 */
		if (info->nat && !(key->ct.state & OVS_CS_F_NAT_MASK) &&
		    (nf_ct_is_confirmed(ct) || info->commit) &&
		    ovs_ct_nat(net, key, info, skb, ct, ctinfo) != NF_ACCEPT) {
			return -EINVAL;
		}

		/* Userspace may decide to perform a ct lookup without a helper
		 * specified followed by a (recirculate and) commit with one.
		 * Therefore, for unconfirmed connections which we will commit,
		 * we need to attach the helper here.
		 */
		if (!nf_ct_is_confirmed(ct) && info->commit &&
		    info->helper && !nfct_help(ct)) {
			int err = __nf_ct_try_assign_helper(ct, info->ct,
							    GFP_ATOMIC);
			if (err)
				return err;
		}

		/* Call the helper only if:
		 * - nf_conntrack_in() was executed above ("!cached") for a
		 *   confirmed connection, or
		 * - When committing an unconfirmed connection.
		 */
		if ((nf_ct_is_confirmed(ct) ? !cached : info->commit) &&
		    ovs_ct_helper(skb, info->family) != NF_ACCEPT) {
			return -EINVAL;
		}
	}

	return 0;
}

/* Lookup connection and read fields into key. */
static int ovs_ct_lookup(struct net *net, struct sw_flow_key *key,
			 const struct ovs_conntrack_info *info,
			 struct sk_buff *skb)
{
	struct nf_conntrack_expect *exp;

	/* If we pass an expected packet through nf_conntrack_in() the
	 * expectation is typically removed, but the packet could still be
	 * lost in upcall processing.  To prevent this from happening we
	 * perform an explicit expectation lookup.  Expected connections are
	 * always new, and will be passed through conntrack only when they are
	 * committed, as it is OK to remove the expectation at that time.
	 */
	exp = ovs_ct_expect_find(net, &info->zone, info->family, skb);
	if (exp) {
		u8 state;

		/* NOTE: New connections are NATted and Helped only when
		 * committed, so we are not calling into NAT here.
		 */
		state = OVS_CS_F_TRACKED | OVS_CS_F_NEW | OVS_CS_F_RELATED;
		__ovs_ct_update_key(key, state, &info->zone, exp->master);
	} else {
		struct nf_conn *ct;
		int err;

		err = __ovs_ct_lookup(net, key, info, skb);
		if (err)
			return err;

		ct = (struct nf_conn *)skb->nfct;
		if (ct)
			nf_ct_deliver_cached_events(ct);
	}

	return 0;
}

static bool labels_nonzero(const struct ovs_key_ct_labels *labels)
{
	size_t i;

	for (i = 0; i < sizeof(*labels); i++)
		if (labels->ct_labels[i])
			return true;

	return false;
}

/* Lookup connection and confirm if unconfirmed. */
static int ovs_ct_commit(struct net *net, struct sw_flow_key *key,
			 const struct ovs_conntrack_info *info,
			 struct sk_buff *skb)
{
	int err;

	err = __ovs_ct_lookup(net, key, info, skb);
	if (err)
		return err;

	/* Apply changes before confirming the connection so that the initial
	 * conntrack NEW netlink event carries the values given in the CT
	 * action.
	 */
	if (info->mark.mask) {
		err = ovs_ct_set_mark(skb, key, info->mark.value,
				      info->mark.mask);
		if (err)
			return err;
	}
	if (labels_nonzero(&info->labels.mask)) {
		err = ovs_ct_set_labels(skb, key, &info->labels.value,
					&info->labels.mask);
		if (err)
			return err;
	}
	/* This will take care of sending queued events even if the connection
	 * is already confirmed.
	 */
	if (nf_conntrack_confirm(skb) != NF_ACCEPT)
		return -EINVAL;

	return 0;
}

/* Returns 0 on success, -EINPROGRESS if 'skb' is stolen, or other nonzero
 * value if 'skb' is freed.
 */
int ovs_ct_execute(struct net *net, struct sk_buff *skb,
		   struct sw_flow_key *key,
		   const struct ovs_conntrack_info *info)
{
	int nh_ofs;
	int err;

	/* The conntrack module expects to be working at L3. */
	nh_ofs = skb_network_offset(skb);
	skb_pull(skb, nh_ofs);

	if (key->ip.frag != OVS_FRAG_TYPE_NONE) {
		err = handle_fragments(net, key, info->zone.id, skb);
		if (err)
			return err;
	}

	if (info->commit)
		err = ovs_ct_commit(net, key, info, skb);
	else
		err = ovs_ct_lookup(net, key, info, skb);

	skb_push(skb, nh_ofs);
	if (err)
		kfree_skb(skb);
	return err;
}

static int ovs_ct_add_helper(struct ovs_conntrack_info *info, const char *name,
			     const struct sw_flow_key *key, bool log)
{
	struct nf_conntrack_helper *helper;
	struct nf_conn_help *help;

	helper = nf_conntrack_helper_try_module_get(name, info->family,
						    key->ip.proto);
	if (!helper) {
		OVS_NLERR(log, "Unknown helper \"%s\"", name);
		return -EINVAL;
	}

	help = nf_ct_helper_ext_add(info->ct, helper, GFP_KERNEL);
	if (!help) {
		module_put(helper->me);
		return -ENOMEM;
	}

	rcu_assign_pointer(help->helper, helper);
	info->helper = helper;
	return 0;
}

#ifdef CONFIG_NF_NAT_NEEDED
static int parse_nat(const struct nlattr *attr,
		     struct ovs_conntrack_info *info, bool log)
{
	struct nlattr *a;
	int rem;
	bool have_ip_max = false;
	bool have_proto_max = false;
	bool ip_vers = (info->family == NFPROTO_IPV6);

	nla_for_each_nested(a, attr, rem) {
		static const int ovs_nat_attr_lens[OVS_NAT_ATTR_MAX + 1][2] = {
			[OVS_NAT_ATTR_SRC] = {0, 0},
			[OVS_NAT_ATTR_DST] = {0, 0},
			[OVS_NAT_ATTR_IP_MIN] = {sizeof(struct in_addr),
						 sizeof(struct in6_addr)},
			[OVS_NAT_ATTR_IP_MAX] = {sizeof(struct in_addr),
						 sizeof(struct in6_addr)},
			[OVS_NAT_ATTR_PROTO_MIN] = {sizeof(u16), sizeof(u16)},
			[OVS_NAT_ATTR_PROTO_MAX] = {sizeof(u16), sizeof(u16)},
			[OVS_NAT_ATTR_PERSISTENT] = {0, 0},
			[OVS_NAT_ATTR_PROTO_HASH] = {0, 0},
			[OVS_NAT_ATTR_PROTO_RANDOM] = {0, 0},
		};
		int type = nla_type(a);

		if (type > OVS_NAT_ATTR_MAX) {
			OVS_NLERR(log,
				  "Unknown NAT attribute (type=%d, max=%d).\n",
				  type, OVS_NAT_ATTR_MAX);
			return -EINVAL;
		}

		if (nla_len(a) != ovs_nat_attr_lens[type][ip_vers]) {
			OVS_NLERR(log,
				  "NAT attribute type %d has unexpected length (%d != %d).\n",
				  type, nla_len(a),
				  ovs_nat_attr_lens[type][ip_vers]);
			return -EINVAL;
		}

		switch (type) {
		case OVS_NAT_ATTR_SRC:
		case OVS_NAT_ATTR_DST:
			if (info->nat) {
				OVS_NLERR(log,
					  "Only one type of NAT may be specified.\n"
					  );
				return -ERANGE;
			}
			info->nat |= OVS_CT_NAT;
			info->nat |= ((type == OVS_NAT_ATTR_SRC)
					? OVS_CT_SRC_NAT : OVS_CT_DST_NAT);
			break;

		case OVS_NAT_ATTR_IP_MIN:
			nla_memcpy(&info->range.min_addr, a,
				   sizeof(info->range.min_addr));
			info->range.flags |= NF_NAT_RANGE_MAP_IPS;
			break;

		case OVS_NAT_ATTR_IP_MAX:
			have_ip_max = true;
			nla_memcpy(&info->range.max_addr, a,
				   sizeof(info->range.max_addr));
			info->range.flags |= NF_NAT_RANGE_MAP_IPS;
			break;

		case OVS_NAT_ATTR_PROTO_MIN:
			info->range.min_proto.all = htons(nla_get_u16(a));
			info->range.flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
			break;

		case OVS_NAT_ATTR_PROTO_MAX:
			have_proto_max = true;
			info->range.max_proto.all = htons(nla_get_u16(a));
			info->range.flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
			break;

		case OVS_NAT_ATTR_PERSISTENT:
			info->range.flags |= NF_NAT_RANGE_PERSISTENT;
			break;

		case OVS_NAT_ATTR_PROTO_HASH:
			info->range.flags |= NF_NAT_RANGE_PROTO_RANDOM;
			break;

		case OVS_NAT_ATTR_PROTO_RANDOM:
			info->range.flags |= NF_NAT_RANGE_PROTO_RANDOM_FULLY;
			break;

		default:
			OVS_NLERR(log, "Unknown nat attribute (%d).\n", type);
			return -EINVAL;
		}
	}

	if (rem > 0) {
		OVS_NLERR(log, "NAT attribute has %d unknown bytes.\n", rem);
		return -EINVAL;
	}
	if (!info->nat) {
		/* Do not allow flags if no type is given. */
		if (info->range.flags) {
			OVS_NLERR(log,
				  "NAT flags may be given only when NAT range (SRC or DST) is also specified.\n"
				  );
			return -EINVAL;
		}
		info->nat = OVS_CT_NAT;   /* NAT existing connections. */
	} else if (!info->commit) {
		OVS_NLERR(log,
			  "NAT attributes may be specified only when CT COMMIT flag is also specified.\n"
			  );
		return -EINVAL;
	}
	/* Allow missing IP_MAX. */
	if (info->range.flags & NF_NAT_RANGE_MAP_IPS && !have_ip_max) {
		memcpy(&info->range.max_addr, &info->range.min_addr,
		       sizeof(info->range.max_addr));
	}
	/* Allow missing PROTO_MAX. */
	if (info->range.flags & NF_NAT_RANGE_PROTO_SPECIFIED &&
	    !have_proto_max) {
		info->range.max_proto.all = info->range.min_proto.all;
	}
	return 0;
}
#endif

static const struct ovs_ct_len_tbl ovs_ct_attr_lens[OVS_CT_ATTR_MAX + 1] = {
	[OVS_CT_ATTR_COMMIT]	= { .minlen = 0, .maxlen = 0 },
	[OVS_CT_ATTR_ZONE]	= { .minlen = sizeof(u16),
				    .maxlen = sizeof(u16) },
	[OVS_CT_ATTR_MARK]	= { .minlen = sizeof(struct md_mark),
				    .maxlen = sizeof(struct md_mark) },
	[OVS_CT_ATTR_LABELS]	= { .minlen = sizeof(struct md_labels),
				    .maxlen = sizeof(struct md_labels) },
	[OVS_CT_ATTR_HELPER]	= { .minlen = 1,
				    .maxlen = NF_CT_HELPER_NAME_LEN },
#ifdef CONFIG_NF_NAT_NEEDED
	/* NAT length is checked when parsing the nested attributes. */
	[OVS_CT_ATTR_NAT]	= { .minlen = 0, .maxlen = INT_MAX },
#endif
};

static int parse_ct(const struct nlattr *attr, struct ovs_conntrack_info *info,
		    const char **helper, bool log)
{
	struct nlattr *a;
	int rem;

	nla_for_each_nested(a, attr, rem) {
		int type = nla_type(a);
		int maxlen = ovs_ct_attr_lens[type].maxlen;
		int minlen = ovs_ct_attr_lens[type].minlen;

		if (type > OVS_CT_ATTR_MAX) {
			OVS_NLERR(log,
				  "Unknown conntrack attr (type=%d, max=%d)",
				  type, OVS_CT_ATTR_MAX);
			return -EINVAL;
		}
		if (nla_len(a) < minlen || nla_len(a) > maxlen) {
			OVS_NLERR(log,
				  "Conntrack attr type has unexpected length (type=%d, length=%d, expected=%d)",
				  type, nla_len(a), maxlen);
			return -EINVAL;
		}

		switch (type) {
		case OVS_CT_ATTR_COMMIT:
			info->commit = true;
			break;
#ifdef CONFIG_NF_CONNTRACK_ZONES
		case OVS_CT_ATTR_ZONE:
			info->zone.id = nla_get_u16(a);
			break;
#endif
#ifdef CONFIG_NF_CONNTRACK_MARK
		case OVS_CT_ATTR_MARK: {
			struct md_mark *mark = nla_data(a);

			if (!mark->mask) {
				OVS_NLERR(log, "ct_mark mask cannot be 0");
				return -EINVAL;
			}
			info->mark = *mark;
			break;
		}
#endif
#ifdef CONFIG_NF_CONNTRACK_LABELS
		case OVS_CT_ATTR_LABELS: {
			struct md_labels *labels = nla_data(a);

			if (!labels_nonzero(&labels->mask)) {
				OVS_NLERR(log, "ct_labels mask cannot be 0");
				return -EINVAL;
			}
			info->labels = *labels;
			break;
		}
#endif
		case OVS_CT_ATTR_HELPER:
			*helper = nla_data(a);
			if (!memchr(*helper, '\0', nla_len(a))) {
				OVS_NLERR(log, "Invalid conntrack helper");
				return -EINVAL;
			}
			break;
#ifdef CONFIG_NF_NAT_NEEDED
		case OVS_CT_ATTR_NAT: {
			int err = parse_nat(a, info, log);

			if (err)
				return err;
			break;
		}
#endif
		default:
			OVS_NLERR(log, "Unknown conntrack attr (%d)",
				  type);
			return -EINVAL;
		}
	}

#ifdef CONFIG_NF_CONNTRACK_MARK
	if (!info->commit && info->mark.mask) {
		OVS_NLERR(log,
			  "Setting conntrack mark requires 'commit' flag.");
		return -EINVAL;
	}
#endif
#ifdef CONFIG_NF_CONNTRACK_LABELS
	if (!info->commit && labels_nonzero(&info->labels.mask)) {
		OVS_NLERR(log,
			  "Setting conntrack labels requires 'commit' flag.");
		return -EINVAL;
	}
#endif
	if (rem > 0) {
		OVS_NLERR(log, "Conntrack attr has %d unknown bytes", rem);
		return -EINVAL;
	}

	return 0;
}

bool ovs_ct_verify(struct net *net, enum ovs_key_attr attr)
{
	if (attr == OVS_KEY_ATTR_CT_STATE)
		return true;
	if (IS_ENABLED(CONFIG_NF_CONNTRACK_ZONES) &&
	    attr == OVS_KEY_ATTR_CT_ZONE)
		return true;
	if (IS_ENABLED(CONFIG_NF_CONNTRACK_MARK) &&
	    attr == OVS_KEY_ATTR_CT_MARK)
		return true;
	if (IS_ENABLED(CONFIG_NF_CONNTRACK_LABELS) &&
	    attr == OVS_KEY_ATTR_CT_LABELS) {
		struct ovs_net *ovs_net = net_generic(net, ovs_net_id);

		return ovs_net->xt_label;
	}

	return false;
}

int ovs_ct_copy_action(struct net *net, const struct nlattr *attr,
		       const struct sw_flow_key *key,
		       struct sw_flow_actions **sfa,  bool log)
{
	struct ovs_conntrack_info ct_info;
	const char *helper = NULL;
	u16 family;
	int err;

	family = key_to_nfproto(key);
	if (family == NFPROTO_UNSPEC) {
		OVS_NLERR(log, "ct family unspecified");
		return -EINVAL;
	}

	memset(&ct_info, 0, sizeof(ct_info));
	ct_info.family = family;

	nf_ct_zone_init(&ct_info.zone, NF_CT_DEFAULT_ZONE_ID,
			NF_CT_DEFAULT_ZONE_DIR, 0);

	err = parse_ct(attr, &ct_info, &helper, log);
	if (err)
		return err;

	/* Set up template for tracking connections in specific zones. */
	ct_info.ct = nf_ct_tmpl_alloc(net, &ct_info.zone, GFP_KERNEL);
	if (!ct_info.ct) {
		OVS_NLERR(log, "Failed to allocate conntrack template");
		return -ENOMEM;
	}

	__set_bit(IPS_CONFIRMED_BIT, &ct_info.ct->status);
	nf_conntrack_get(&ct_info.ct->ct_general);

	if (helper) {
		err = ovs_ct_add_helper(&ct_info, helper, key, log);
		if (err)
			goto err_free_ct;
	}

	err = ovs_nla_add_action(sfa, OVS_ACTION_ATTR_CT, &ct_info,
				 sizeof(ct_info), log);
	if (err)
		goto err_free_ct;

	return 0;
err_free_ct:
	__ovs_ct_free_action(&ct_info);
	return err;
}

#ifdef CONFIG_NF_NAT_NEEDED
static bool ovs_ct_nat_to_attr(const struct ovs_conntrack_info *info,
			       struct sk_buff *skb)
{
	struct nlattr *start;

	start = nla_nest_start(skb, OVS_CT_ATTR_NAT);
	if (!start)
		return false;

	if (info->nat & OVS_CT_SRC_NAT) {
		if (nla_put_flag(skb, OVS_NAT_ATTR_SRC))
			return false;
	} else if (info->nat & OVS_CT_DST_NAT) {
		if (nla_put_flag(skb, OVS_NAT_ATTR_DST))
			return false;
	} else {
		goto out;
	}

	if (info->range.flags & NF_NAT_RANGE_MAP_IPS) {
		if (IS_ENABLED(CONFIG_NF_NAT_IPV4) &&
		    info->family == NFPROTO_IPV4) {
			if (nla_put_in_addr(skb, OVS_NAT_ATTR_IP_MIN,
					    info->range.min_addr.ip) ||
			    (info->range.max_addr.ip
			     != info->range.min_addr.ip &&
			     (nla_put_in_addr(skb, OVS_NAT_ATTR_IP_MAX,
					      info->range.max_addr.ip))))
				return false;
		} else if (IS_ENABLED(CONFIG_NF_NAT_IPV6) &&
			   info->family == NFPROTO_IPV6) {
			if (nla_put_in6_addr(skb, OVS_NAT_ATTR_IP_MIN,
					     &info->range.min_addr.in6) ||
			    (memcmp(&info->range.max_addr.in6,
				    &info->range.min_addr.in6,
				    sizeof(info->range.max_addr.in6)) &&
			     (nla_put_in6_addr(skb, OVS_NAT_ATTR_IP_MAX,
					       &info->range.max_addr.in6))))
				return false;
		} else {
			return false;
		}
	}
	if (info->range.flags & NF_NAT_RANGE_PROTO_SPECIFIED &&
	    (nla_put_u16(skb, OVS_NAT_ATTR_PROTO_MIN,
			 ntohs(info->range.min_proto.all)) ||
	     (info->range.max_proto.all != info->range.min_proto.all &&
	      nla_put_u16(skb, OVS_NAT_ATTR_PROTO_MAX,
			  ntohs(info->range.max_proto.all)))))
		return false;

	if (info->range.flags & NF_NAT_RANGE_PERSISTENT &&
	    nla_put_flag(skb, OVS_NAT_ATTR_PERSISTENT))
		return false;
	if (info->range.flags & NF_NAT_RANGE_PROTO_RANDOM &&
	    nla_put_flag(skb, OVS_NAT_ATTR_PROTO_HASH))
		return false;
	if (info->range.flags & NF_NAT_RANGE_PROTO_RANDOM_FULLY &&
	    nla_put_flag(skb, OVS_NAT_ATTR_PROTO_RANDOM))
		return false;
out:
	nla_nest_end(skb, start);

	return true;
}
#endif

int ovs_ct_action_to_attr(const struct ovs_conntrack_info *ct_info,
			  struct sk_buff *skb)
{
	struct nlattr *start;

	start = nla_nest_start(skb, OVS_ACTION_ATTR_CT);
	if (!start)
		return -EMSGSIZE;

	if (ct_info->commit && nla_put_flag(skb, OVS_CT_ATTR_COMMIT))
		return -EMSGSIZE;
	if (IS_ENABLED(CONFIG_NF_CONNTRACK_ZONES) &&
	    nla_put_u16(skb, OVS_CT_ATTR_ZONE, ct_info->zone.id))
		return -EMSGSIZE;
	if (IS_ENABLED(CONFIG_NF_CONNTRACK_MARK) && ct_info->mark.mask &&
	    nla_put(skb, OVS_CT_ATTR_MARK, sizeof(ct_info->mark),
		    &ct_info->mark))
		return -EMSGSIZE;
	if (IS_ENABLED(CONFIG_NF_CONNTRACK_LABELS) &&
	    labels_nonzero(&ct_info->labels.mask) &&
	    nla_put(skb, OVS_CT_ATTR_LABELS, sizeof(ct_info->labels),
		    &ct_info->labels))
		return -EMSGSIZE;
	if (ct_info->helper) {
		if (nla_put_string(skb, OVS_CT_ATTR_HELPER,
				   ct_info->helper->name))
			return -EMSGSIZE;
	}
#ifdef CONFIG_NF_NAT_NEEDED
	if (ct_info->nat && !ovs_ct_nat_to_attr(ct_info, skb))
		return -EMSGSIZE;
#endif
	nla_nest_end(skb, start);

	return 0;
}

void ovs_ct_free_action(const struct nlattr *a)
{
	struct ovs_conntrack_info *ct_info = nla_data(a);

	__ovs_ct_free_action(ct_info);
}

static void __ovs_ct_free_action(struct ovs_conntrack_info *ct_info)
{
	if (ct_info->helper)
		module_put(ct_info->helper->me);
	if (ct_info->ct)
		nf_ct_tmpl_free(ct_info->ct);
}

void ovs_ct_init(struct net *net)
{
	unsigned int n_bits = sizeof(struct ovs_key_ct_labels) * BITS_PER_BYTE;
	struct ovs_net *ovs_net = net_generic(net, ovs_net_id);

	if (nf_connlabels_get(net, n_bits - 1)) {
		ovs_net->xt_label = false;
		OVS_NLERR(true, "Failed to set connlabel length");
	} else {
		ovs_net->xt_label = true;
	}
}

void ovs_ct_exit(struct net *net)
{
	struct ovs_net *ovs_net = net_generic(net, ovs_net_id);

	if (ovs_net->xt_label)
		nf_connlabels_put(net);
}