flow.c

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/*
 * Copyright (c) 2007-2011 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA
 */

#include "flow.h"
#include "datapath.h"
#include <linux/uaccess.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/if_ether.h>
#include <linux/if_vlan.h>
#include <net/llc_pdu.h>
#include <linux/kernel.h>
#include <linux/jhash.h>
#include <linux/jiffies.h>
#include <linux/llc.h>
#include <linux/module.h>
#include <linux/in.h>
#include <linux/rcupdate.h>
#include <linux/if_arp.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/icmp.h>
#include <linux/icmpv6.h>
#include <linux/rculist.h>
#include <net/ip.h>
#include <net/ipv6.h>
#include <net/ndisc.h>

static struct kmem_cache *flow_cache;

static int check_header(struct sk_buff *skb, int len)
{
    if (unlikely(skb->len < len))
        return -EINVAL;
    if (unlikely(!pskb_may_pull(skb, len)))
        return -ENOMEM;
    return 0;
}

static bool arphdr_ok(struct sk_buff *skb)
{
    return pskb_may_pull(skb, skb_network_offset(skb) +
                  sizeof(struct arp_eth_header));
}

static int check_iphdr(struct sk_buff *skb)
{
    unsigned int nh_ofs = skb_network_offset(skb);
    unsigned int ip_len;
    int err;

    err = check_header(skb, nh_ofs + sizeof(struct iphdr));
    if (unlikely(err))
        return err;

    ip_len = ip_hdrlen(skb);
    if (unlikely(ip_len < sizeof(struct iphdr) ||
             skb->len < nh_ofs + ip_len))
        return -EINVAL;

    skb_set_transport_header(skb, nh_ofs + ip_len);
    return 0;
}

static bool tcphdr_ok(struct sk_buff *skb)
{
    int th_ofs = skb_transport_offset(skb);
    int tcp_len;

    if (unlikely(!pskb_may_pull(skb, th_ofs + sizeof(struct tcphdr))))
        return false;

    tcp_len = tcp_hdrlen(skb);
    if (unlikely(tcp_len < sizeof(struct tcphdr) ||
             skb->len < th_ofs + tcp_len))
        return false;

    return true;
}

static bool udphdr_ok(struct sk_buff *skb)
{
    return pskb_may_pull(skb, skb_transport_offset(skb) +
                  sizeof(struct udphdr));
}

static bool icmphdr_ok(struct sk_buff *skb)
{
    return pskb_may_pull(skb, skb_transport_offset(skb) +
                  sizeof(struct icmphdr));
}

u64 ovs_flow_used_time(unsigned long flow_jiffies)
{
    struct timespec cur_ts;
    u64 cur_ms, idle_ms;

    ktime_get_ts(&cur_ts);
    idle_ms = jiffies_to_msecs(jiffies - flow_jiffies);
    cur_ms = (u64)cur_ts.tv_sec * MSEC_PER_SEC +
         cur_ts.tv_nsec / NSEC_PER_MSEC;

    return cur_ms - idle_ms;
}

#define SW_FLOW_KEY_OFFSET(field)       \
    (offsetof(struct sw_flow_key, field) +  \
     FIELD_SIZEOF(struct sw_flow_key, field))

static int parse_ipv6hdr(struct sk_buff *skb, struct sw_flow_key *key,
             int *key_lenp)
{
    unsigned int nh_ofs = skb_network_offset(skb);
    unsigned int nh_len;
    int payload_ofs;
    struct ipv6hdr *nh;
    uint8_t nexthdr;
    __be16 frag_off;
    int err;

    *key_lenp = SW_FLOW_KEY_OFFSET(ipv6.label);

    err = check_header(skb, nh_ofs + sizeof(*nh));
    if (unlikely(err))
        return err;

    nh = ipv6_hdr(skb);
    nexthdr = nh->nexthdr;
    payload_ofs = (u8 *)(nh + 1) - skb->data;

    key->ip.proto = NEXTHDR_NONE;
    key->ip.tos = ipv6_get_dsfield(nh);
    key->ip.ttl = nh->hop_limit;
    key->ipv6.label = *(__be32 *)nh & htonl(IPV6_FLOWINFO_FLOWLABEL);
    key->ipv6.addr.src = nh->saddr;
    key->ipv6.addr.dst = nh->daddr;

    payload_ofs = ipv6_skip_exthdr(skb, payload_ofs, &nexthdr, &frag_off);
    if (unlikely(payload_ofs < 0))
        return -EINVAL;

    if (frag_off) {
        if (frag_off & htons(~0x7))
            key->ip.frag = OVS_FRAG_TYPE_LATER;
        else
            key->ip.frag = OVS_FRAG_TYPE_FIRST;
    }

    nh_len = payload_ofs - nh_ofs;
    skb_set_transport_header(skb, nh_ofs + nh_len);
    key->ip.proto = nexthdr;
    return nh_len;
}

static bool icmp6hdr_ok(struct sk_buff *skb)
{
    return pskb_may_pull(skb, skb_transport_offset(skb) +
                  sizeof(struct icmp6hdr));
}

#define TCP_FLAGS_OFFSET 13
#define TCP_FLAG_MASK 0x3f

void ovs_flow_used(struct sw_flow *flow, struct sk_buff *skb)
{
    u8 tcp_flags = 0;

    if ((flow->key.eth.type == htons(ETH_P_IP) ||
         flow->key.eth.type == htons(ETH_P_IPV6)) &&
        flow->key.ip.proto == IPPROTO_TCP &&
        likely(skb->len >= skb_transport_offset(skb) + sizeof(struct tcphdr))) {
        u8 *tcp = (u8 *)tcp_hdr(skb);
        tcp_flags = *(tcp + TCP_FLAGS_OFFSET) & TCP_FLAG_MASK;
    }

    spin_lock(&flow->lock);
    flow->used = jiffies;
    flow->packet_count++;
    flow->byte_count += skb->len;
    flow->tcp_flags |= tcp_flags;
    spin_unlock(&flow->lock);
}

struct sw_flow_actions *ovs_flow_actions_alloc(const struct nlattr *actions)
{
    int actions_len = nla_len(actions);
    struct sw_flow_actions *sfa;

    if (actions_len > MAX_ACTIONS_BUFSIZE)
        return ERR_PTR(-EINVAL);

    sfa = kmalloc(sizeof(*sfa) + actions_len, GFP_KERNEL);
    if (!sfa)
        return ERR_PTR(-ENOMEM);

    sfa->actions_len = actions_len;
    memcpy(sfa->actions, nla_data(actions), actions_len);
    return sfa;
}

struct sw_flow *ovs_flow_alloc(void)
{
    struct sw_flow *flow;

    flow = kmem_cache_alloc(flow_cache, GFP_KERNEL);
    if (!flow)
        return ERR_PTR(-ENOMEM);

    spin_lock_init(&flow->lock);
    flow->sf_acts = NULL;

    return flow;
}

static struct hlist_head *find_bucket(struct flow_table *table, u32 hash)
{
    hash = jhash_1word(hash, table->hash_seed);
    return flex_array_get(table->buckets,
                (hash & (table->n_buckets - 1)));
}

static struct flex_array *alloc_buckets(unsigned int n_buckets)
{
    struct flex_array *buckets;
    int i, err;

    buckets = flex_array_alloc(sizeof(struct hlist_head *),
                   n_buckets, GFP_KERNEL);
    if (!buckets)
        return NULL;

    err = flex_array_prealloc(buckets, 0, n_buckets, GFP_KERNEL);
    if (err) {
        flex_array_free(buckets);
        return NULL;
    }

    for (i = 0; i < n_buckets; i++)
        INIT_HLIST_HEAD((struct hlist_head *)
                    flex_array_get(buckets, i));

    return buckets;
}

static void free_buckets(struct flex_array *buckets)
{
    flex_array_free(buckets);
}

struct flow_table *ovs_flow_tbl_alloc(int new_size)
{
    struct flow_table *table = kmalloc(sizeof(*table), GFP_KERNEL);

    if (!table)
        return NULL;

    table->buckets = alloc_buckets(new_size);

    if (!table->buckets) {
        kfree(table);
        return NULL;
    }
    table->n_buckets = new_size;
    table->count = 0;
    table->node_ver = 0;
    table->keep_flows = false;
    get_random_bytes(&table->hash_seed, sizeof(u32));

    return table;
}

void ovs_flow_tbl_destroy(struct flow_table *table)
{
    int i;

    if (!table)
        return;

    if (table->keep_flows)
        goto skip_flows;

    for (i = 0; i < table->n_buckets; i++) {
        struct sw_flow *flow;
        struct hlist_head *head = flex_array_get(table->buckets, i);
        struct hlist_node *node, *n;
        int ver = table->node_ver;

        hlist_for_each_entry_safe(flow, node, n, head, hash_node[ver]) {
            hlist_del_rcu(&flow->hash_node[ver]);
            ovs_flow_free(flow);
        }
    }

skip_flows:
    free_buckets(table->buckets);
    kfree(table);
}

static void flow_tbl_destroy_rcu_cb(struct rcu_head *rcu)
{
    struct flow_table *table = container_of(rcu, struct flow_table, rcu);

    ovs_flow_tbl_destroy(table);
}

void ovs_flow_tbl_deferred_destroy(struct flow_table *table)
{
    if (!table)
        return;

    call_rcu(&table->rcu, flow_tbl_destroy_rcu_cb);
}

struct sw_flow *ovs_flow_tbl_next(struct flow_table *table, u32 *bucket, u32 *last)
{
    struct sw_flow *flow;
    struct hlist_head *head;
    struct hlist_node *n;
    int ver;
    int i;

    ver = table->node_ver;
    while (*bucket < table->n_buckets) {
        i = 0;
        head = flex_array_get(table->buckets, *bucket);
        hlist_for_each_entry_rcu(flow, n, head, hash_node[ver]) {
            if (i < *last) {
                i++;
                continue;
            }
            *last = i + 1;
            return flow;
        }
        (*bucket)++;
        *last = 0;
    }

    return NULL;
}

static void flow_table_copy_flows(struct flow_table *old, struct flow_table *new)
{
    int old_ver;
    int i;

    old_ver = old->node_ver;
    new->node_ver = !old_ver;

    /* Insert in new table. */
    for (i = 0; i < old->n_buckets; i++) {
        struct sw_flow *flow;
        struct hlist_head *head;
        struct hlist_node *n;

        head = flex_array_get(old->buckets, i);

        hlist_for_each_entry(flow, n, head, hash_node[old_ver])
            ovs_flow_tbl_insert(new, flow);
    }
    old->keep_flows = true;
}

static struct flow_table *__flow_tbl_rehash(struct flow_table *table, int n_buckets)
{
    struct flow_table *new_table;

    new_table = ovs_flow_tbl_alloc(n_buckets);
    if (!new_table)
        return ERR_PTR(-ENOMEM);

    flow_table_copy_flows(table, new_table);

    return new_table;
}

struct flow_table *ovs_flow_tbl_rehash(struct flow_table *table)
{
    return __flow_tbl_rehash(table, table->n_buckets);
}

struct flow_table *ovs_flow_tbl_expand(struct flow_table *table)
{
    return __flow_tbl_rehash(table, table->n_buckets * 2);
}

void ovs_flow_free(struct sw_flow *flow)
{
    if (unlikely(!flow))
        return;

    kfree((struct sf_flow_acts __force *)flow->sf_acts);
    kmem_cache_free(flow_cache, flow);
}

/* RCU callback used by ovs_flow_deferred_free. */
static void rcu_free_flow_callback(struct rcu_head *rcu)
{
    struct sw_flow *flow = container_of(rcu, struct sw_flow, rcu);

    ovs_flow_free(flow);
}

/* Schedules 'flow' to be freed after the next RCU grace period.
 * The caller must hold rcu_read_lock for this to be sensible. */
void ovs_flow_deferred_free(struct sw_flow *flow)
{
    call_rcu(&flow->rcu, rcu_free_flow_callback);
}

/* Schedules 'sf_acts' to be freed after the next RCU grace period.
 * The caller must hold rcu_read_lock for this to be sensible. */
void ovs_flow_deferred_free_acts(struct sw_flow_actions *sf_acts)
{
    kfree_rcu(sf_acts, rcu);
}

static int parse_vlan(struct sk_buff *skb, struct sw_flow_key *key)
{
    struct qtag_prefix {
        __be16 eth_type; /* ETH_P_8021Q */
        __be16 tci;
    };
    struct qtag_prefix *qp;

    if (unlikely(skb->len < sizeof(struct qtag_prefix) + sizeof(__be16)))
        return 0;

    if (unlikely(!pskb_may_pull(skb, sizeof(struct qtag_prefix) +
                     sizeof(__be16))))
        return -ENOMEM;

    qp = (struct qtag_prefix *) skb->data;
    key->eth.tci = qp->tci | htons(VLAN_TAG_PRESENT);
    __skb_pull(skb, sizeof(struct qtag_prefix));

    return 0;
}

static __be16 parse_ethertype(struct sk_buff *skb)
{
    struct llc_snap_hdr {
        u8  dsap;  /* Always 0xAA */
        u8  ssap;  /* Always 0xAA */
        u8  ctrl;
        u8  oui[3];
        __be16 ethertype;
    };
    struct llc_snap_hdr *llc;
    __be16 proto;

    proto = *(__be16 *) skb->data;
    __skb_pull(skb, sizeof(__be16));

    if (ntohs(proto) >= 1536)
        return proto;

    if (skb->len < sizeof(struct llc_snap_hdr))
        return htons(ETH_P_802_2);

    if (unlikely(!pskb_may_pull(skb, sizeof(struct llc_snap_hdr))))
        return htons(0);

    llc = (struct llc_snap_hdr *) skb->data;
    if (llc->dsap != LLC_SAP_SNAP ||
        llc->ssap != LLC_SAP_SNAP ||
        (llc->oui[0] | llc->oui[1] | llc->oui[2]) != 0)
        return htons(ETH_P_802_2);

    __skb_pull(skb, sizeof(struct llc_snap_hdr));
    return llc->ethertype;
}

static int parse_icmpv6(struct sk_buff *skb, struct sw_flow_key *key,
            int *key_lenp, int nh_len)
{
    struct icmp6hdr *icmp = icmp6_hdr(skb);
    int error = 0;
    int key_len;

    /* The ICMPv6 type and code fields use the 16-bit transport port
     * fields, so we need to store them in 16-bit network byte order.
     */
    key->ipv6.tp.src = htons(icmp->icmp6_type);
    key->ipv6.tp.dst = htons(icmp->icmp6_code);
    key_len = SW_FLOW_KEY_OFFSET(ipv6.tp);

    if (icmp->icmp6_code == 0 &&
        (icmp->icmp6_type == NDISC_NEIGHBOUR_SOLICITATION ||
         icmp->icmp6_type == NDISC_NEIGHBOUR_ADVERTISEMENT)) {
        int icmp_len = skb->len - skb_transport_offset(skb);
        struct nd_msg *nd;
        int offset;

        key_len = SW_FLOW_KEY_OFFSET(ipv6.nd);

        /* In order to process neighbor discovery options, we need the
         * entire packet.
         */
        if (unlikely(icmp_len < sizeof(*nd)))
            goto out;
        if (unlikely(skb_linearize(skb))) {
            error = -ENOMEM;
            goto out;
        }

        nd = (struct nd_msg *)skb_transport_header(skb);
        key->ipv6.nd.target = nd->target;
        key_len = SW_FLOW_KEY_OFFSET(ipv6.nd);

        icmp_len -= sizeof(*nd);
        offset = 0;
        while (icmp_len >= 8) {
            struct nd_opt_hdr *nd_opt =
                 (struct nd_opt_hdr *)(nd->opt + offset);
            int opt_len = nd_opt->nd_opt_len * 8;

            if (unlikely(!opt_len || opt_len > icmp_len))
                goto invalid;

            /* Store the link layer address if the appropriate
             * option is provided.  It is considered an error if
             * the same link layer option is specified twice.
             */
            if (nd_opt->nd_opt_type == ND_OPT_SOURCE_LL_ADDR
                && opt_len == 8) {
                if (unlikely(!is_zero_ether_addr(key->ipv6.nd.sll)))
                    goto invalid;
                memcpy(key->ipv6.nd.sll,
                    &nd->opt[offset+sizeof(*nd_opt)], ETH_ALEN);
            } else if (nd_opt->nd_opt_type == ND_OPT_TARGET_LL_ADDR
                   && opt_len == 8) {
                if (unlikely(!is_zero_ether_addr(key->ipv6.nd.tll)))
                    goto invalid;
                memcpy(key->ipv6.nd.tll,
                    &nd->opt[offset+sizeof(*nd_opt)], ETH_ALEN);
            }

            icmp_len -= opt_len;
            offset += opt_len;
        }
    }

    goto out;

invalid:
    memset(&key->ipv6.nd.target, 0, sizeof(key->ipv6.nd.target));
    memset(key->ipv6.nd.sll, 0, sizeof(key->ipv6.nd.sll));
    memset(key->ipv6.nd.tll, 0, sizeof(key->ipv6.nd.tll));

out:
    *key_lenp = key_len;
    return error;
}

int ovs_flow_extract(struct sk_buff *skb, u16 in_port, struct sw_flow_key *key,
         int *key_lenp)
{
    int error = 0;
    int key_len = SW_FLOW_KEY_OFFSET(eth);
    struct ethhdr *eth;

    memset(key, 0, sizeof(*key));

    key->phy.priority = skb->priority;
    key->phy.in_port = in_port;

    skb_reset_mac_header(skb);

    /* Link layer.  We are guaranteed to have at least the 14 byte Ethernet
     * header in the linear data area.
     */
    eth = eth_hdr(skb);
    memcpy(key->eth.src, eth->h_source, ETH_ALEN);
    memcpy(key->eth.dst, eth->h_dest, ETH_ALEN);

    __skb_pull(skb, 2 * ETH_ALEN);

    if (vlan_tx_tag_present(skb))
        key->eth.tci = htons(skb->vlan_tci);
    else if (eth->h_proto == htons(ETH_P_8021Q))
        if (unlikely(parse_vlan(skb, key)))
            return -ENOMEM;

    key->eth.type = parse_ethertype(skb);
    if (unlikely(key->eth.type == htons(0)))
        return -ENOMEM;

    skb_reset_network_header(skb);
    __skb_push(skb, skb->data - skb_mac_header(skb));

    /* Network layer. */
    if (key->eth.type == htons(ETH_P_IP)) {
        struct iphdr *nh;
        __be16 offset;

        key_len = SW_FLOW_KEY_OFFSET(ipv4.addr);

        error = check_iphdr(skb);
        if (unlikely(error)) {
            if (error == -EINVAL) {
                skb->transport_header = skb->network_header;
                error = 0;
            }
            goto out;
        }

        nh = ip_hdr(skb);
        key->ipv4.addr.src = nh->saddr;
        key->ipv4.addr.dst = nh->daddr;

        key->ip.proto = nh->protocol;
        key->ip.tos = nh->tos;
        key->ip.ttl = nh->ttl;

        offset = nh->frag_off & htons(IP_OFFSET);
        if (offset) {
            key->ip.frag = OVS_FRAG_TYPE_LATER;
            goto out;
        }
        if (nh->frag_off & htons(IP_MF) ||
             skb_shinfo(skb)->gso_type & SKB_GSO_UDP)
            key->ip.frag = OVS_FRAG_TYPE_FIRST;

        /* Transport layer. */
        if (key->ip.proto == IPPROTO_TCP) {
            key_len = SW_FLOW_KEY_OFFSET(ipv4.tp);
            if (tcphdr_ok(skb)) {
                struct tcphdr *tcp = tcp_hdr(skb);
                key->ipv4.tp.src = tcp->source;
                key->ipv4.tp.dst = tcp->dest;
            }
        } else if (key->ip.proto == IPPROTO_UDP) {
            key_len = SW_FLOW_KEY_OFFSET(ipv4.tp);
            if (udphdr_ok(skb)) {
                struct udphdr *udp = udp_hdr(skb);
                key->ipv4.tp.src = udp->source;
                key->ipv4.tp.dst = udp->dest;
            }
        } else if (key->ip.proto == IPPROTO_ICMP) {
            key_len = SW_FLOW_KEY_OFFSET(ipv4.tp);
            if (icmphdr_ok(skb)) {
                struct icmphdr *icmp = icmp_hdr(skb);
                /* The ICMP type and code fields use the 16-bit
                 * transport port fields, so we need to store
                 * them in 16-bit network byte order. */
                key->ipv4.tp.src = htons(icmp->type);
                key->ipv4.tp.dst = htons(icmp->code);
            }
        }

    } else if (key->eth.type == htons(ETH_P_ARP) && arphdr_ok(skb)) {
        struct arp_eth_header *arp;

        arp = (struct arp_eth_header *)skb_network_header(skb);

        if (arp->ar_hrd == htons(ARPHRD_ETHER)
                && arp->ar_pro == htons(ETH_P_IP)
                && arp->ar_hln == ETH_ALEN
                && arp->ar_pln == 4) {

            /* We only match on the lower 8 bits of the opcode. */
            if (ntohs(arp->ar_op) <= 0xff)
                key->ip.proto = ntohs(arp->ar_op);
            memcpy(&key->ipv4.addr.src, arp->ar_sip, sizeof(key->ipv4.addr.src));
            memcpy(&key->ipv4.addr.dst, arp->ar_tip, sizeof(key->ipv4.addr.dst));
            memcpy(key->ipv4.arp.sha, arp->ar_sha, ETH_ALEN);
            memcpy(key->ipv4.arp.tha, arp->ar_tha, ETH_ALEN);
            key_len = SW_FLOW_KEY_OFFSET(ipv4.arp);
        }
    } else if (key->eth.type == htons(ETH_P_IPV6)) {
        int nh_len;             /* IPv6 Header + Extensions */

        nh_len = parse_ipv6hdr(skb, key, &key_len);
        if (unlikely(nh_len < 0)) {
            if (nh_len == -EINVAL)
                skb->transport_header = skb->network_header;
            else
                error = nh_len;
            goto out;
        }

        if (key->ip.frag == OVS_FRAG_TYPE_LATER)
            goto out;
        if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP)
            key->ip.frag = OVS_FRAG_TYPE_FIRST;

        /* Transport layer. */
        if (key->ip.proto == NEXTHDR_TCP) {
            key_len = SW_FLOW_KEY_OFFSET(ipv6.tp);
            if (tcphdr_ok(skb)) {
                struct tcphdr *tcp = tcp_hdr(skb);
                key->ipv6.tp.src = tcp->source;
                key->ipv6.tp.dst = tcp->dest;
            }
        } else if (key->ip.proto == NEXTHDR_UDP) {
            key_len = SW_FLOW_KEY_OFFSET(ipv6.tp);
            if (udphdr_ok(skb)) {
                struct udphdr *udp = udp_hdr(skb);
                key->ipv6.tp.src = udp->source;
                key->ipv6.tp.dst = udp->dest;
            }
        } else if (key->ip.proto == NEXTHDR_ICMP) {
            key_len = SW_FLOW_KEY_OFFSET(ipv6.tp);
            if (icmp6hdr_ok(skb)) {
                error = parse_icmpv6(skb, key, &key_len, nh_len);
                if (error < 0)
                    goto out;
            }
        }
    }

out:
    *key_lenp = key_len;
    return error;
}

u32 ovs_flow_hash(const struct sw_flow_key *key, int key_len)
{
    return jhash2((u32 *)key, DIV_ROUND_UP(key_len, sizeof(u32)), 0);
}

struct sw_flow *ovs_flow_tbl_lookup(struct flow_table *table,
                struct sw_flow_key *key, int key_len)
{
    struct sw_flow *flow;
    struct hlist_node *n;
    struct hlist_head *head;
    u32 hash;

    hash = ovs_flow_hash(key, key_len);

    head = find_bucket(table, hash);
    hlist_for_each_entry_rcu(flow, n, head, hash_node[table->node_ver]) {

        if (flow->hash == hash &&
            !memcmp(&flow->key, key, key_len)) {
            return flow;
        }
    }
    return NULL;
}

void ovs_flow_tbl_insert(struct flow_table *table, struct sw_flow *flow)
{
    struct hlist_head *head;

    head = find_bucket(table, flow->hash);
    hlist_add_head_rcu(&flow->hash_node[table->node_ver], head);
    table->count++;
}

void ovs_flow_tbl_remove(struct flow_table *table, struct sw_flow *flow)
{
    hlist_del_rcu(&flow->hash_node[table->node_ver]);
    table->count--;
    BUG_ON(table->count < 0);
}

/* The size of the argument for each %OVS_KEY_ATTR_* Netlink attribute.  */
const int ovs_key_lens[OVS_KEY_ATTR_MAX + 1] = {
    [OVS_KEY_ATTR_ENCAP] = -1,
    [OVS_KEY_ATTR_PRIORITY] = sizeof(u32),
    [OVS_KEY_ATTR_IN_PORT] = sizeof(u32),
    [OVS_KEY_ATTR_ETHERNET] = sizeof(struct ovs_key_ethernet),
    [OVS_KEY_ATTR_VLAN] = sizeof(__be16),
    [OVS_KEY_ATTR_ETHERTYPE] = sizeof(__be16),
    [OVS_KEY_ATTR_IPV4] = sizeof(struct ovs_key_ipv4),
    [OVS_KEY_ATTR_IPV6] = sizeof(struct ovs_key_ipv6),
    [OVS_KEY_ATTR_TCP] = sizeof(struct ovs_key_tcp),
    [OVS_KEY_ATTR_UDP] = sizeof(struct ovs_key_udp),
    [OVS_KEY_ATTR_ICMP] = sizeof(struct ovs_key_icmp),
    [OVS_KEY_ATTR_ICMPV6] = sizeof(struct ovs_key_icmpv6),
    [OVS_KEY_ATTR_ARP] = sizeof(struct ovs_key_arp),
    [OVS_KEY_ATTR_ND] = sizeof(struct ovs_key_nd),
};

static int ipv4_flow_from_nlattrs(struct sw_flow_key *swkey, int *key_len,
                  const struct nlattr *a[], u32 *attrs)
{
    const struct ovs_key_icmp *icmp_key;
    const struct ovs_key_tcp *tcp_key;
    const struct ovs_key_udp *udp_key;

    switch (swkey->ip.proto) {
    case IPPROTO_TCP:
        if (!(*attrs & (1 << OVS_KEY_ATTR_TCP)))
            return -EINVAL;
        *attrs &= ~(1 << OVS_KEY_ATTR_TCP);

        *key_len = SW_FLOW_KEY_OFFSET(ipv4.tp);
        tcp_key = nla_data(a[OVS_KEY_ATTR_TCP]);
        swkey->ipv4.tp.src = tcp_key->tcp_src;
        swkey->ipv4.tp.dst = tcp_key->tcp_dst;
        break;

    case IPPROTO_UDP:
        if (!(*attrs & (1 << OVS_KEY_ATTR_UDP)))
            return -EINVAL;
        *attrs &= ~(1 << OVS_KEY_ATTR_UDP);

        *key_len = SW_FLOW_KEY_OFFSET(ipv4.tp);
        udp_key = nla_data(a[OVS_KEY_ATTR_UDP]);
        swkey->ipv4.tp.src = udp_key->udp_src;
        swkey->ipv4.tp.dst = udp_key->udp_dst;
        break;

    case IPPROTO_ICMP:
        if (!(*attrs & (1 << OVS_KEY_ATTR_ICMP)))
            return -EINVAL;
        *attrs &= ~(1 << OVS_KEY_ATTR_ICMP);

        *key_len = SW_FLOW_KEY_OFFSET(ipv4.tp);
        icmp_key = nla_data(a[OVS_KEY_ATTR_ICMP]);
        swkey->ipv4.tp.src = htons(icmp_key->icmp_type);
        swkey->ipv4.tp.dst = htons(icmp_key->icmp_code);
        break;
    }

    return 0;
}

static int ipv6_flow_from_nlattrs(struct sw_flow_key *swkey, int *key_len,
                  const struct nlattr *a[], u32 *attrs)
{
    const struct ovs_key_icmpv6 *icmpv6_key;
    const struct ovs_key_tcp *tcp_key;
    const struct ovs_key_udp *udp_key;

    switch (swkey->ip.proto) {
    case IPPROTO_TCP:
        if (!(*attrs & (1 << OVS_KEY_ATTR_TCP)))
            return -EINVAL;
        *attrs &= ~(1 << OVS_KEY_ATTR_TCP);

        *key_len = SW_FLOW_KEY_OFFSET(ipv6.tp);
        tcp_key = nla_data(a[OVS_KEY_ATTR_TCP]);
        swkey->ipv6.tp.src = tcp_key->tcp_src;
        swkey->ipv6.tp.dst = tcp_key->tcp_dst;
        break;

    case IPPROTO_UDP:
        if (!(*attrs & (1 << OVS_KEY_ATTR_UDP)))
            return -EINVAL;
        *attrs &= ~(1 << OVS_KEY_ATTR_UDP);

        *key_len = SW_FLOW_KEY_OFFSET(ipv6.tp);
        udp_key = nla_data(a[OVS_KEY_ATTR_UDP]);
        swkey->ipv6.tp.src = udp_key->udp_src;
        swkey->ipv6.tp.dst = udp_key->udp_dst;
        break;

    case IPPROTO_ICMPV6:
        if (!(*attrs & (1 << OVS_KEY_ATTR_ICMPV6)))
            return -EINVAL;
        *attrs &= ~(1 << OVS_KEY_ATTR_ICMPV6);

        *key_len = SW_FLOW_KEY_OFFSET(ipv6.tp);
        icmpv6_key = nla_data(a[OVS_KEY_ATTR_ICMPV6]);
        swkey->ipv6.tp.src = htons(icmpv6_key->icmpv6_type);
        swkey->ipv6.tp.dst = htons(icmpv6_key->icmpv6_code);

        if (swkey->ipv6.tp.src == htons(NDISC_NEIGHBOUR_SOLICITATION) ||
            swkey->ipv6.tp.src == htons(NDISC_NEIGHBOUR_ADVERTISEMENT)) {
            const struct ovs_key_nd *nd_key;

            if (!(*attrs & (1 << OVS_KEY_ATTR_ND)))
                return -EINVAL;
            *attrs &= ~(1 << OVS_KEY_ATTR_ND);

            *key_len = SW_FLOW_KEY_OFFSET(ipv6.nd);
            nd_key = nla_data(a[OVS_KEY_ATTR_ND]);
            memcpy(&swkey->ipv6.nd.target, nd_key->nd_target,
                   sizeof(swkey->ipv6.nd.target));
            memcpy(swkey->ipv6.nd.sll, nd_key->nd_sll, ETH_ALEN);
            memcpy(swkey->ipv6.nd.tll, nd_key->nd_tll, ETH_ALEN);
        }
        break;
    }

    return 0;
}

static int parse_flow_nlattrs(const struct nlattr *attr,
                  const struct nlattr *a[], u32 *attrsp)
{
    const struct nlattr *nla;
    u32 attrs;
    int rem;

    attrs = 0;
    nla_for_each_nested(nla, attr, rem) {
        u16 type = nla_type(nla);
        int expected_len;

        if (type > OVS_KEY_ATTR_MAX || attrs & (1 << type))
            return -EINVAL;

        expected_len = ovs_key_lens[type];
        if (nla_len(nla) != expected_len && expected_len != -1)
            return -EINVAL;

        attrs |= 1 << type;
        a[type] = nla;
    }
    if (rem)
        return -EINVAL;

    *attrsp = attrs;
    return 0;
}

int ovs_flow_from_nlattrs(struct sw_flow_key *swkey, int *key_lenp,
              const struct nlattr *attr)
{
    const struct nlattr *a[OVS_KEY_ATTR_MAX + 1];
    const struct ovs_key_ethernet *eth_key;
    int key_len;
    u32 attrs;
    int err;

    memset(swkey, 0, sizeof(struct sw_flow_key));
    key_len = SW_FLOW_KEY_OFFSET(eth);

    err = parse_flow_nlattrs(attr, a, &attrs);
    if (err)
        return err;

    /* Metadata attributes. */
    if (attrs & (1 << OVS_KEY_ATTR_PRIORITY)) {
        swkey->phy.priority = nla_get_u32(a[OVS_KEY_ATTR_PRIORITY]);
        attrs &= ~(1 << OVS_KEY_ATTR_PRIORITY);
    }
    if (attrs & (1 << OVS_KEY_ATTR_IN_PORT)) {
        u32 in_port = nla_get_u32(a[OVS_KEY_ATTR_IN_PORT]);
        if (in_port >= DP_MAX_PORTS)
            return -EINVAL;
        swkey->phy.in_port = in_port;
        attrs &= ~(1 << OVS_KEY_ATTR_IN_PORT);
    } else {
        swkey->phy.in_port = DP_MAX_PORTS;
    }

    /* Data attributes. */
    if (!(attrs & (1 << OVS_KEY_ATTR_ETHERNET)))
        return -EINVAL;
    attrs &= ~(1 << OVS_KEY_ATTR_ETHERNET);

    eth_key = nla_data(a[OVS_KEY_ATTR_ETHERNET]);
    memcpy(swkey->eth.src, eth_key->eth_src, ETH_ALEN);
    memcpy(swkey->eth.dst, eth_key->eth_dst, ETH_ALEN);

    if (attrs & (1u << OVS_KEY_ATTR_ETHERTYPE) &&
        nla_get_be16(a[OVS_KEY_ATTR_ETHERTYPE]) == htons(ETH_P_8021Q)) {
        const struct nlattr *encap;
        __be16 tci;

        if (attrs != ((1 << OVS_KEY_ATTR_VLAN) |
                  (1 << OVS_KEY_ATTR_ETHERTYPE) |
                  (1 << OVS_KEY_ATTR_ENCAP)))
            return -EINVAL;

        encap = a[OVS_KEY_ATTR_ENCAP];
        tci = nla_get_be16(a[OVS_KEY_ATTR_VLAN]);
        if (tci & htons(VLAN_TAG_PRESENT)) {
            swkey->eth.tci = tci;

            err = parse_flow_nlattrs(encap, a, &attrs);
            if (err)
                return err;
        } else if (!tci) {
            /* Corner case for truncated 802.1Q header. */
            if (nla_len(encap))
                return -EINVAL;

            swkey->eth.type = htons(ETH_P_8021Q);
            *key_lenp = key_len;
            return 0;
        } else {
            return -EINVAL;
        }
    }

    if (attrs & (1 << OVS_KEY_ATTR_ETHERTYPE)) {
        swkey->eth.type = nla_get_be16(a[OVS_KEY_ATTR_ETHERTYPE]);
        if (ntohs(swkey->eth.type) < 1536)
            return -EINVAL;
        attrs &= ~(1 << OVS_KEY_ATTR_ETHERTYPE);
    } else {
        swkey->eth.type = htons(ETH_P_802_2);
    }

    if (swkey->eth.type == htons(ETH_P_IP)) {
        const struct ovs_key_ipv4 *ipv4_key;

        if (!(attrs & (1 << OVS_KEY_ATTR_IPV4)))
            return -EINVAL;
        attrs &= ~(1 << OVS_KEY_ATTR_IPV4);

        key_len = SW_FLOW_KEY_OFFSET(ipv4.addr);
        ipv4_key = nla_data(a[OVS_KEY_ATTR_IPV4]);
        if (ipv4_key->ipv4_frag > OVS_FRAG_TYPE_MAX)
            return -EINVAL;
        swkey->ip.proto = ipv4_key->ipv4_proto;
        swkey->ip.tos = ipv4_key->ipv4_tos;
        swkey->ip.ttl = ipv4_key->ipv4_ttl;
        swkey->ip.frag = ipv4_key->ipv4_frag;
        swkey->ipv4.addr.src = ipv4_key->ipv4_src;
        swkey->ipv4.addr.dst = ipv4_key->ipv4_dst;

        if (swkey->ip.frag != OVS_FRAG_TYPE_LATER) {
            err = ipv4_flow_from_nlattrs(swkey, &key_len, a, &attrs);
            if (err)
                return err;
        }
    } else if (swkey->eth.type == htons(ETH_P_IPV6)) {
        const struct ovs_key_ipv6 *ipv6_key;

        if (!(attrs & (1 << OVS_KEY_ATTR_IPV6)))
            return -EINVAL;
        attrs &= ~(1 << OVS_KEY_ATTR_IPV6);

        key_len = SW_FLOW_KEY_OFFSET(ipv6.label);
        ipv6_key = nla_data(a[OVS_KEY_ATTR_IPV6]);
        if (ipv6_key->ipv6_frag > OVS_FRAG_TYPE_MAX)
            return -EINVAL;
        swkey->ipv6.label = ipv6_key->ipv6_label;
        swkey->ip.proto = ipv6_key->ipv6_proto;
        swkey->ip.tos = ipv6_key->ipv6_tclass;
        swkey->ip.ttl = ipv6_key->ipv6_hlimit;
        swkey->ip.frag = ipv6_key->ipv6_frag;
        memcpy(&swkey->ipv6.addr.src, ipv6_key->ipv6_src,
               sizeof(swkey->ipv6.addr.src));
        memcpy(&swkey->ipv6.addr.dst, ipv6_key->ipv6_dst,
               sizeof(swkey->ipv6.addr.dst));

        if (swkey->ip.frag != OVS_FRAG_TYPE_LATER) {
            err = ipv6_flow_from_nlattrs(swkey, &key_len, a, &attrs);
            if (err)
                return err;
        }
    } else if (swkey->eth.type == htons(ETH_P_ARP)) {
        const struct ovs_key_arp *arp_key;

        if (!(attrs & (1 << OVS_KEY_ATTR_ARP)))
            return -EINVAL;
        attrs &= ~(1 << OVS_KEY_ATTR_ARP);

        key_len = SW_FLOW_KEY_OFFSET(ipv4.arp);
        arp_key = nla_data(a[OVS_KEY_ATTR_ARP]);
        swkey->ipv4.addr.src = arp_key->arp_sip;
        swkey->ipv4.addr.dst = arp_key->arp_tip;
        if (arp_key->arp_op & htons(0xff00))
            return -EINVAL;
        swkey->ip.proto = ntohs(arp_key->arp_op);
        memcpy(swkey->ipv4.arp.sha, arp_key->arp_sha, ETH_ALEN);
        memcpy(swkey->ipv4.arp.tha, arp_key->arp_tha, ETH_ALEN);
    }

    if (attrs)
        return -EINVAL;
    *key_lenp = key_len;

    return 0;
}

int ovs_flow_metadata_from_nlattrs(u32 *priority, u16 *in_port,
                   const struct nlattr *attr)
{
    const struct nlattr *nla;
    int rem;

    *in_port = DP_MAX_PORTS;
    *priority = 0;

    nla_for_each_nested(nla, attr, rem) {
        int type = nla_type(nla);

        if (type <= OVS_KEY_ATTR_MAX && ovs_key_lens[type] > 0) {
            if (nla_len(nla) != ovs_key_lens[type])
                return -EINVAL;

            switch (type) {
            case OVS_KEY_ATTR_PRIORITY:
                *priority = nla_get_u32(nla);
                break;

            case OVS_KEY_ATTR_IN_PORT:
                if (nla_get_u32(nla) >= DP_MAX_PORTS)
                    return -EINVAL;
                *in_port = nla_get_u32(nla);
                break;
            }
        }
    }
    if (rem)
        return -EINVAL;
    return 0;
}

int ovs_flow_to_nlattrs(const struct sw_flow_key *swkey, struct sk_buff *skb)
{
    struct ovs_key_ethernet *eth_key;
    struct nlattr *nla, *encap;

    if (swkey->phy.priority &&
        nla_put_u32(skb, OVS_KEY_ATTR_PRIORITY, swkey->phy.priority))
        goto nla_put_failure;

    if (swkey->phy.in_port != DP_MAX_PORTS &&
        nla_put_u32(skb, OVS_KEY_ATTR_IN_PORT, swkey->phy.in_port))
        goto nla_put_failure;

    nla = nla_reserve(skb, OVS_KEY_ATTR_ETHERNET, sizeof(*eth_key));
    if (!nla)
        goto nla_put_failure;
    eth_key = nla_data(nla);
    memcpy(eth_key->eth_src, swkey->eth.src, ETH_ALEN);
    memcpy(eth_key->eth_dst, swkey->eth.dst, ETH_ALEN);

    if (swkey->eth.tci || swkey->eth.type == htons(ETH_P_8021Q)) {
        if (nla_put_be16(skb, OVS_KEY_ATTR_ETHERTYPE, htons(ETH_P_8021Q)) ||
            nla_put_be16(skb, OVS_KEY_ATTR_VLAN, swkey->eth.tci))
            goto nla_put_failure;
        encap = nla_nest_start(skb, OVS_KEY_ATTR_ENCAP);
        if (!swkey->eth.tci)
            goto unencap;
    } else {
        encap = NULL;
    }

    if (swkey->eth.type == htons(ETH_P_802_2))
        goto unencap;

    if (nla_put_be16(skb, OVS_KEY_ATTR_ETHERTYPE, swkey->eth.type))
        goto nla_put_failure;

    if (swkey->eth.type == htons(ETH_P_IP)) {
        struct ovs_key_ipv4 *ipv4_key;

        nla = nla_reserve(skb, OVS_KEY_ATTR_IPV4, sizeof(*ipv4_key));
        if (!nla)
            goto nla_put_failure;
        ipv4_key = nla_data(nla);
        ipv4_key->ipv4_src = swkey->ipv4.addr.src;
        ipv4_key->ipv4_dst = swkey->ipv4.addr.dst;
        ipv4_key->ipv4_proto = swkey->ip.proto;
        ipv4_key->ipv4_tos = swkey->ip.tos;
        ipv4_key->ipv4_ttl = swkey->ip.ttl;
        ipv4_key->ipv4_frag = swkey->ip.frag;
    } else if (swkey->eth.type == htons(ETH_P_IPV6)) {
        struct ovs_key_ipv6 *ipv6_key;

        nla = nla_reserve(skb, OVS_KEY_ATTR_IPV6, sizeof(*ipv6_key));
        if (!nla)
            goto nla_put_failure;
        ipv6_key = nla_data(nla);
        memcpy(ipv6_key->ipv6_src, &swkey->ipv6.addr.src,
                sizeof(ipv6_key->ipv6_src));
        memcpy(ipv6_key->ipv6_dst, &swkey->ipv6.addr.dst,
                sizeof(ipv6_key->ipv6_dst));
        ipv6_key->ipv6_label = swkey->ipv6.label;
        ipv6_key->ipv6_proto = swkey->ip.proto;
        ipv6_key->ipv6_tclass = swkey->ip.tos;
        ipv6_key->ipv6_hlimit = swkey->ip.ttl;
        ipv6_key->ipv6_frag = swkey->ip.frag;
    } else if (swkey->eth.type == htons(ETH_P_ARP)) {
        struct ovs_key_arp *arp_key;

        nla = nla_reserve(skb, OVS_KEY_ATTR_ARP, sizeof(*arp_key));
        if (!nla)
            goto nla_put_failure;
        arp_key = nla_data(nla);
        memset(arp_key, 0, sizeof(struct ovs_key_arp));
        arp_key->arp_sip = swkey->ipv4.addr.src;
        arp_key->arp_tip = swkey->ipv4.addr.dst;
        arp_key->arp_op = htons(swkey->ip.proto);
        memcpy(arp_key->arp_sha, swkey->ipv4.arp.sha, ETH_ALEN);
        memcpy(arp_key->arp_tha, swkey->ipv4.arp.tha, ETH_ALEN);
    }

    if ((swkey->eth.type == htons(ETH_P_IP) ||
         swkey->eth.type == htons(ETH_P_IPV6)) &&
         swkey->ip.frag != OVS_FRAG_TYPE_LATER) {

        if (swkey->ip.proto == IPPROTO_TCP) {
            struct ovs_key_tcp *tcp_key;

            nla = nla_reserve(skb, OVS_KEY_ATTR_TCP, sizeof(*tcp_key));
            if (!nla)
                goto nla_put_failure;
            tcp_key = nla_data(nla);
            if (swkey->eth.type == htons(ETH_P_IP)) {
                tcp_key->tcp_src = swkey->ipv4.tp.src;
                tcp_key->tcp_dst = swkey->ipv4.tp.dst;
            } else if (swkey->eth.type == htons(ETH_P_IPV6)) {
                tcp_key->tcp_src = swkey->ipv6.tp.src;
                tcp_key->tcp_dst = swkey->ipv6.tp.dst;
            }
        } else if (swkey->ip.proto == IPPROTO_UDP) {
            struct ovs_key_udp *udp_key;

            nla = nla_reserve(skb, OVS_KEY_ATTR_UDP, sizeof(*udp_key));
            if (!nla)
                goto nla_put_failure;
            udp_key = nla_data(nla);
            if (swkey->eth.type == htons(ETH_P_IP)) {
                udp_key->udp_src = swkey->ipv4.tp.src;
                udp_key->udp_dst = swkey->ipv4.tp.dst;
            } else if (swkey->eth.type == htons(ETH_P_IPV6)) {
                udp_key->udp_src = swkey->ipv6.tp.src;
                udp_key->udp_dst = swkey->ipv6.tp.dst;
            }
        } else if (swkey->eth.type == htons(ETH_P_IP) &&
               swkey->ip.proto == IPPROTO_ICMP) {
            struct ovs_key_icmp *icmp_key;

            nla = nla_reserve(skb, OVS_KEY_ATTR_ICMP, sizeof(*icmp_key));
            if (!nla)
                goto nla_put_failure;
            icmp_key = nla_data(nla);
            icmp_key->icmp_type = ntohs(swkey->ipv4.tp.src);
            icmp_key->icmp_code = ntohs(swkey->ipv4.tp.dst);
        } else if (swkey->eth.type == htons(ETH_P_IPV6) &&
               swkey->ip.proto == IPPROTO_ICMPV6) {
            struct ovs_key_icmpv6 *icmpv6_key;

            nla = nla_reserve(skb, OVS_KEY_ATTR_ICMPV6,
                        sizeof(*icmpv6_key));
            if (!nla)
                goto nla_put_failure;
            icmpv6_key = nla_data(nla);
            icmpv6_key->icmpv6_type = ntohs(swkey->ipv6.tp.src);
            icmpv6_key->icmpv6_code = ntohs(swkey->ipv6.tp.dst);

            if (icmpv6_key->icmpv6_type == NDISC_NEIGHBOUR_SOLICITATION ||
                icmpv6_key->icmpv6_type == NDISC_NEIGHBOUR_ADVERTISEMENT) {
                struct ovs_key_nd *nd_key;

                nla = nla_reserve(skb, OVS_KEY_ATTR_ND, sizeof(*nd_key));
                if (!nla)
                    goto nla_put_failure;
                nd_key = nla_data(nla);
                memcpy(nd_key->nd_target, &swkey->ipv6.nd.target,
                            sizeof(nd_key->nd_target));
                memcpy(nd_key->nd_sll, swkey->ipv6.nd.sll, ETH_ALEN);
                memcpy(nd_key->nd_tll, swkey->ipv6.nd.tll, ETH_ALEN);
            }
        }
    }

unencap:
    if (encap)
        nla_nest_end(skb, encap);

    return 0;

nla_put_failure:
    return -EMSGSIZE;
}

/* Initializes the flow module.
 * Returns zero if successful or a negative error code. */
int ovs_flow_init(void)
{
    flow_cache = kmem_cache_create("sw_flow", sizeof(struct sw_flow), 0,
                    0, NULL);
    if (flow_cache == NULL)
        return -ENOMEM;

    return 0;
}

/* Uninitializes the flow module. */
void ovs_flow_exit(void)
{
    kmem_cache_destroy(flow_cache);
}