datapath: Merge "struct dp_port" into "struct vport".

[mirror_ovs.git] / datapath / tunnel.c

/*
 * Copyright (c) 2010 Nicira Networks.
 * Distributed under the terms of the GNU GPL version 2.
 *
 * Significant portions of this file may be copied from parts of the Linux
 * kernel, by Linus Torvalds and others.
 */

#include <linux/if_arp.h>
#include <linux/if_ether.h>
#include <linux/ip.h>
#include <linux/if_vlan.h>
#include <linux/in.h>
#include <linux/in_route.h>
#include <linux/jhash.h>
#include <linux/kernel.h>
#include <linux/version.h>
#include <linux/workqueue.h>

#include <net/dsfield.h>
#include <net/dst.h>
#include <net/icmp.h>
#include <net/inet_ecn.h>
#include <net/ip.h>
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
#include <net/ipv6.h>
#endif
#include <net/route.h>
#include <net/xfrm.h>

#include "actions.h"
#include "datapath.h"
#include "table.h"
#include "tunnel.h"
#include "vport.h"
#include "vport-generic.h"
#include "vport-internal_dev.h"

#ifdef NEED_CACHE_TIMEOUT
/*
 * On kernels where we can't quickly detect changes in the rest of the system
 * we use an expiration time to invalidate the cache.  A shorter expiration
 * reduces the length of time that we may potentially blackhole packets while
 * a longer time increases performance by reducing the frequency that the
 * cache needs to be rebuilt.  A variety of factors may cause the cache to be
 * invalidated before the expiration time but this is the maximum.  The time
 * is expressed in jiffies.
 */
#define MAX_CACHE_EXP HZ
#endif

/*
 * Interval to check for and remove caches that are no longer valid.  Caches
 * are checked for validity before they are used for packet encapsulation and
 * old caches are removed at that time.  However, if no packets are sent through
 * the tunnel then the cache will never be destroyed.  Since it holds
 * references to a number of system objects, the cache will continue to use
 * system resources by not allowing those objects to be destroyed.  The cache
 * cleaner is periodically run to free invalid caches.  It does not
 * significantly affect system performance.  A lower interval will release
 * resources faster but will itself consume resources by requiring more frequent
 * checks.  A longer interval may result in messages being printed to the kernel
 * message buffer about unreleased resources.  The interval is expressed in
 * jiffies.
 */
#define CACHE_CLEANER_INTERVAL (5 * HZ)

#define CACHE_DATA_ALIGN 16

/* Protected by RCU. */
static struct tbl *port_table __read_mostly;

static void cache_cleaner(struct work_struct *work);
DECLARE_DELAYED_WORK(cache_cleaner_wq, cache_cleaner);

/*
 * These are just used as an optimization: they don't require any kind of
 * synchronization because we could have just as easily read the value before
 * the port change happened.
 */
static unsigned int key_local_remote_ports __read_mostly;
static unsigned int key_remote_ports __read_mostly;
static unsigned int local_remote_ports __read_mostly;
static unsigned int remote_ports __read_mostly;

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,36)
#define rt_dst(rt) (rt->dst)
#else
#define rt_dst(rt) (rt->u.dst)
#endif

static inline struct vport *tnl_vport_to_vport(const struct tnl_vport *tnl_vport)
{
        return vport_from_priv(tnl_vport);
}

static inline struct tnl_vport *tnl_vport_table_cast(const struct tbl_node *node)
{
        return container_of(node, struct tnl_vport, tbl_node);
}

static inline void schedule_cache_cleaner(void)
{
        schedule_delayed_work(&cache_cleaner_wq, CACHE_CLEANER_INTERVAL);
}

static void free_cache(struct tnl_cache *cache)
{
        if (!cache)
                return;

        flow_put(cache->flow);
        ip_rt_put(cache->rt);
        kfree(cache);
}

static void free_config_rcu(struct rcu_head *rcu)
{
        struct tnl_mutable_config *c = container_of(rcu, struct tnl_mutable_config, rcu);
        kfree(c);
}

static void free_cache_rcu(struct rcu_head *rcu)
{
        struct tnl_cache *c = container_of(rcu, struct tnl_cache, rcu);
        free_cache(c);
}

static void assign_config_rcu(struct vport *vport,
                              struct tnl_mutable_config *new_config)
{
        struct tnl_vport *tnl_vport = tnl_vport_priv(vport);
        struct tnl_mutable_config *old_config;

        old_config = tnl_vport->mutable;
        rcu_assign_pointer(tnl_vport->mutable, new_config);
        call_rcu(&old_config->rcu, free_config_rcu);
}

static void assign_cache_rcu(struct vport *vport, struct tnl_cache *new_cache)
{
        struct tnl_vport *tnl_vport = tnl_vport_priv(vport);
        struct tnl_cache *old_cache;

        old_cache = tnl_vport->cache;
        rcu_assign_pointer(tnl_vport->cache, new_cache);

        if (old_cache)
                call_rcu(&old_cache->rcu, free_cache_rcu);
}

static unsigned int *find_port_pool(const struct tnl_mutable_config *mutable)
{
        if (mutable->port_config.flags & TNL_F_IN_KEY_MATCH) {
                if (mutable->port_config.saddr)
                        return &local_remote_ports;
                else
                        return &remote_ports;
        } else {
                if (mutable->port_config.saddr)
                        return &key_local_remote_ports;
                else
                        return &key_remote_ports;
        }
}

struct port_lookup_key {
        u32 tunnel_type;
        __be32 saddr;
        __be32 daddr;
        __be32 key;
        const struct tnl_mutable_config *mutable;
};

/*
 * Modifies 'target' to store the rcu_dereferenced pointer that was used to do
 * the comparision.
 */
static int port_cmp(const struct tbl_node *node, void *target)
{
        const struct tnl_vport *tnl_vport = tnl_vport_table_cast(node);
        struct port_lookup_key *lookup = target;

        lookup->mutable = rcu_dereference(tnl_vport->mutable);

        return (lookup->mutable->tunnel_type == lookup->tunnel_type &&
                lookup->mutable->port_config.daddr == lookup->daddr &&
                lookup->mutable->port_config.in_key == lookup->key &&
                lookup->mutable->port_config.saddr == lookup->saddr);
}

static u32 port_hash(struct port_lookup_key *k)
{
        return jhash_3words(k->key, k->saddr, k->daddr, k->tunnel_type);
}

static u32 mutable_hash(const struct tnl_mutable_config *mutable)
{
        struct port_lookup_key lookup;

        lookup.saddr = mutable->port_config.saddr;
        lookup.daddr = mutable->port_config.daddr;
        lookup.key = mutable->port_config.in_key;
        lookup.tunnel_type = mutable->tunnel_type;

        return port_hash(&lookup);
}

static void check_table_empty(void)
{
        if (tbl_count(port_table) == 0) {
                struct tbl *old_table = port_table;

                cancel_delayed_work_sync(&cache_cleaner_wq);
                rcu_assign_pointer(port_table, NULL);
                tbl_deferred_destroy(old_table, NULL);
        }
}

static int add_port(struct vport *vport)
{
        struct tnl_vport *tnl_vport = tnl_vport_priv(vport);
        int err;

        if (!port_table) {
                struct tbl *new_table;

                new_table = tbl_create(0);
                if (!new_table)
                        return -ENOMEM;

                rcu_assign_pointer(port_table, new_table);
                schedule_cache_cleaner();

        } else if (tbl_count(port_table) > tbl_n_buckets(port_table)) {
                struct tbl *old_table = port_table;
                struct tbl *new_table;

                new_table = tbl_expand(old_table);
                if (IS_ERR(new_table))
                        return PTR_ERR(new_table);

                rcu_assign_pointer(port_table, new_table);
                tbl_deferred_destroy(old_table, NULL);
        }

        err = tbl_insert(port_table, &tnl_vport->tbl_node, mutable_hash(tnl_vport->mutable));
        if (err) {
                check_table_empty();
                return err;
        }

        (*find_port_pool(tnl_vport->mutable))++;

        return 0;
}

static int move_port(struct vport *vport, struct tnl_mutable_config *new_mutable)
{
        int err;
        struct tnl_vport *tnl_vport = tnl_vport_priv(vport);
        u32 hash;

        hash = mutable_hash(new_mutable);
        if (hash == tnl_vport->tbl_node.hash)
                goto table_updated;

        /*
         * Ideally we should make this move atomic to avoid having gaps in
         * finding tunnels or the possibility of failure.  However, if we do
         * find a tunnel it will always be consistent.
         */
        err = tbl_remove(port_table, &tnl_vport->tbl_node);
        if (err)
                return err;

        err = tbl_insert(port_table, &tnl_vport->tbl_node, hash);
        if (err) {
                check_table_empty();
                return err;
        }

table_updated:
        assign_config_rcu(vport, new_mutable);

        return 0;
}

static int del_port(struct vport *vport)
{
        struct tnl_vport *tnl_vport = tnl_vport_priv(vport);
        int err;

        err = tbl_remove(port_table, &tnl_vport->tbl_node);
        if (err)
                return err;

        check_table_empty();
        (*find_port_pool(tnl_vport->mutable))--;

        return 0;
}

struct vport *tnl_find_port(__be32 saddr, __be32 daddr, __be32 key,
                            int tunnel_type,
                            const struct tnl_mutable_config **mutable)
{
        struct port_lookup_key lookup;
        struct tbl *table = rcu_dereference(port_table);
        struct tbl_node *tbl_node;

        if (unlikely(!table))
                return NULL;

        lookup.saddr = saddr;
        lookup.daddr = daddr;

        if (tunnel_type & TNL_T_KEY_EXACT) {
                lookup.key = key;
                lookup.tunnel_type = tunnel_type & ~TNL_T_KEY_MATCH;

                if (key_local_remote_ports) {
                        tbl_node = tbl_lookup(table, &lookup, port_hash(&lookup), port_cmp);
                        if (tbl_node)
                                goto found;
                }

                if (key_remote_ports) {
                        lookup.saddr = 0;

                        tbl_node = tbl_lookup(table, &lookup, port_hash(&lookup), port_cmp);
                        if (tbl_node)
                                goto found;

                        lookup.saddr = saddr;
                }
        }

        if (tunnel_type & TNL_T_KEY_MATCH) {
                lookup.key = 0;
                lookup.tunnel_type = tunnel_type & ~TNL_T_KEY_EXACT;

                if (local_remote_ports) {
                        tbl_node = tbl_lookup(table, &lookup, port_hash(&lookup), port_cmp);
                        if (tbl_node)
                                goto found;
                }

                if (remote_ports) {
                        lookup.saddr = 0;

                        tbl_node = tbl_lookup(table, &lookup, port_hash(&lookup), port_cmp);
                        if (tbl_node)
                                goto found;
                }
        }

        return NULL;

found:
        *mutable = lookup.mutable;
        return tnl_vport_to_vport(tnl_vport_table_cast(tbl_node));
}

static inline void ecn_decapsulate(struct sk_buff *skb)
{
        u8 tos = ip_hdr(skb)->tos;

        if (INET_ECN_is_ce(tos)) {
                __be16 protocol = skb->protocol;
                unsigned int nw_header = skb_network_offset(skb);

                if (skb->protocol == htons(ETH_P_8021Q)) {
                        if (unlikely(!pskb_may_pull(skb, VLAN_ETH_HLEN)))
                                return;

                        protocol = vlan_eth_hdr(skb)->h_vlan_encapsulated_proto;
                        nw_header += VLAN_HLEN;
                }

                if (protocol == htons(ETH_P_IP)) {
                        if (unlikely(!pskb_may_pull(skb, nw_header
                            + sizeof(struct iphdr))))
                                return;

                        IP_ECN_set_ce((struct iphdr *)(skb->data + nw_header));
                }
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
                else if (protocol == htons(ETH_P_IPV6)) {
                        if (unlikely(!pskb_may_pull(skb, nw_header
                            + sizeof(struct ipv6hdr))))
                                return;

                        IP6_ECN_set_ce((struct ipv6hdr *)(skb->data + nw_header));
                }
#endif
        }
}

/* Called with rcu_read_lock. */
void tnl_rcv(struct vport *vport, struct sk_buff *skb)
{
        skb->pkt_type = PACKET_HOST;
        skb->protocol = eth_type_trans(skb, skb->dev);

        skb_dst_drop(skb);
        nf_reset(skb);
        secpath_reset(skb);
        skb_reset_network_header(skb);

        ecn_decapsulate(skb);

        skb_push(skb, ETH_HLEN);
        compute_ip_summed(skb, false);

        vport_receive(vport, skb);
}

static bool check_ipv4_address(__be32 addr)
{
        if (ipv4_is_multicast(addr) || ipv4_is_lbcast(addr)
            || ipv4_is_loopback(addr) || ipv4_is_zeronet(addr))
                return false;

        return true;
}

static bool ipv4_should_icmp(struct sk_buff *skb)
{
        struct iphdr *old_iph = ip_hdr(skb);

        /* Don't respond to L2 broadcast. */
        if (is_multicast_ether_addr(eth_hdr(skb)->h_dest))
                return false;

        /* Don't respond to L3 broadcast or invalid addresses. */
        if (!check_ipv4_address(old_iph->daddr) ||
            !check_ipv4_address(old_iph->saddr))
                return false;

        /* Only respond to the first fragment. */
        if (old_iph->frag_off & htons(IP_OFFSET))
                return false;

        /* Don't respond to ICMP error messages. */
        if (old_iph->protocol == IPPROTO_ICMP) {
                u8 icmp_type, *icmp_typep;

                icmp_typep = skb_header_pointer(skb, (u8 *)old_iph +
                                                (old_iph->ihl << 2) +
                                                offsetof(struct icmphdr, type) -
                                                skb->data, sizeof(icmp_type),
                                                &icmp_type);

                if (!icmp_typep)
                        return false;

                if (*icmp_typep > NR_ICMP_TYPES
                        || (*icmp_typep <= ICMP_PARAMETERPROB
                                && *icmp_typep != ICMP_ECHOREPLY
                                && *icmp_typep != ICMP_ECHO))
                        return false;
        }

        return true;
}

static void ipv4_build_icmp(struct sk_buff *skb, struct sk_buff *nskb,
                            unsigned int mtu, unsigned int payload_length)
{
        struct iphdr *iph, *old_iph = ip_hdr(skb);
        struct icmphdr *icmph;
        u8 *payload;

        iph = (struct iphdr *)skb_put(nskb, sizeof(struct iphdr));
        icmph = (struct icmphdr *)skb_put(nskb, sizeof(struct icmphdr));
        payload = skb_put(nskb, payload_length);

        /* IP */
        iph->version            =       4;
        iph->ihl                =       sizeof(struct iphdr) >> 2;
        iph->tos                =       (old_iph->tos & IPTOS_TOS_MASK) |
                                        IPTOS_PREC_INTERNETCONTROL;
        iph->tot_len            =       htons(sizeof(struct iphdr)
                                              + sizeof(struct icmphdr)
                                              + payload_length);
        get_random_bytes(&iph->id, sizeof(iph->id));
        iph->frag_off           =       0;
        iph->ttl                =       IPDEFTTL;
        iph->protocol           =       IPPROTO_ICMP;
        iph->daddr              =       old_iph->saddr;
        iph->saddr              =       old_iph->daddr;

        ip_send_check(iph);

        /* ICMP */
        icmph->type             =       ICMP_DEST_UNREACH;
        icmph->code             =       ICMP_FRAG_NEEDED;
        icmph->un.gateway       =       htonl(mtu);
        icmph->checksum         =       0;

        nskb->csum = csum_partial((u8 *)icmph, sizeof(struct icmphdr), 0);
        nskb->csum = skb_copy_and_csum_bits(skb, (u8 *)old_iph - skb->data,
                                            payload, payload_length,
                                            nskb->csum);
        icmph->checksum = csum_fold(nskb->csum);
}

#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
static bool ipv6_should_icmp(struct sk_buff *skb)
{
        struct ipv6hdr *old_ipv6h = ipv6_hdr(skb);
        int addr_type;
        int payload_off = (u8 *)(old_ipv6h + 1) - skb->data;
        u8 nexthdr = ipv6_hdr(skb)->nexthdr;

        /* Check source address is valid. */
        addr_type = ipv6_addr_type(&old_ipv6h->saddr);
        if (addr_type & IPV6_ADDR_MULTICAST || addr_type == IPV6_ADDR_ANY)
                return false;

        /* Don't reply to unspecified addresses. */
        if (ipv6_addr_type(&old_ipv6h->daddr) == IPV6_ADDR_ANY)
                return false;

        /* Don't respond to ICMP error messages. */
        payload_off = ipv6_skip_exthdr(skb, payload_off, &nexthdr);
        if (payload_off < 0)
                return false;

        if (nexthdr == NEXTHDR_ICMP) {
                u8 icmp_type, *icmp_typep;

                icmp_typep = skb_header_pointer(skb, payload_off +
                                                offsetof(struct icmp6hdr,
                                                        icmp6_type),
                                                sizeof(icmp_type), &icmp_type);

                if (!icmp_typep || !(*icmp_typep & ICMPV6_INFOMSG_MASK))
                        return false;
        }

        return true;
}

static void ipv6_build_icmp(struct sk_buff *skb, struct sk_buff *nskb,
                            unsigned int mtu, unsigned int payload_length)
{
        struct ipv6hdr *ipv6h, *old_ipv6h = ipv6_hdr(skb);
        struct icmp6hdr *icmp6h;
        u8 *payload;

        ipv6h = (struct ipv6hdr *)skb_put(nskb, sizeof(struct ipv6hdr));
        icmp6h = (struct icmp6hdr *)skb_put(nskb, sizeof(struct icmp6hdr));
        payload = skb_put(nskb, payload_length);

        /* IPv6 */
        ipv6h->version          =       6;
        ipv6h->priority         =       0;
        memset(&ipv6h->flow_lbl, 0, sizeof(ipv6h->flow_lbl));
        ipv6h->payload_len      =       htons(sizeof(struct icmp6hdr)
                                              + payload_length);
        ipv6h->nexthdr          =       NEXTHDR_ICMP;
        ipv6h->hop_limit        =       IPV6_DEFAULT_HOPLIMIT;
        ipv6_addr_copy(&ipv6h->daddr, &old_ipv6h->saddr);
        ipv6_addr_copy(&ipv6h->saddr, &old_ipv6h->daddr);

        /* ICMPv6 */
        icmp6h->icmp6_type      =       ICMPV6_PKT_TOOBIG;
        icmp6h->icmp6_code      =       0;
        icmp6h->icmp6_cksum     =       0;
        icmp6h->icmp6_mtu       =       htonl(mtu);

        nskb->csum = csum_partial((u8 *)icmp6h, sizeof(struct icmp6hdr), 0);
        nskb->csum = skb_copy_and_csum_bits(skb, (u8 *)old_ipv6h - skb->data,
                                            payload, payload_length,
                                            nskb->csum);
        icmp6h->icmp6_cksum = csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
                                                sizeof(struct icmp6hdr)
                                                + payload_length,
                                                ipv6h->nexthdr, nskb->csum);
}
#endif /* IPv6 */

bool tnl_frag_needed(struct vport *vport, const struct tnl_mutable_config *mutable,
                     struct sk_buff *skb, unsigned int mtu, __be32 flow_key)
{
        unsigned int eth_hdr_len = ETH_HLEN;
        unsigned int total_length = 0, header_length = 0, payload_length;
        struct ethhdr *eh, *old_eh = eth_hdr(skb);
        struct sk_buff *nskb;

        /* Sanity check */
        if (skb->protocol == htons(ETH_P_IP)) {
                if (mtu < IP_MIN_MTU)
                        return false;

                if (!ipv4_should_icmp(skb))
                        return true;
        }
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
        else if (skb->protocol == htons(ETH_P_IPV6)) {
                if (mtu < IPV6_MIN_MTU)
                        return false;

                /*
                 * In theory we should do PMTUD on IPv6 multicast messages but
                 * we don't have an address to send from so just fragment.
                 */
                if (ipv6_addr_type(&ipv6_hdr(skb)->daddr) & IPV6_ADDR_MULTICAST)
                        return false;

                if (!ipv6_should_icmp(skb))
                        return true;
        }
#endif
        else
                return false;

        /* Allocate */
        if (old_eh->h_proto == htons(ETH_P_8021Q))
                eth_hdr_len = VLAN_ETH_HLEN;

        payload_length = skb->len - eth_hdr_len;
        if (skb->protocol == htons(ETH_P_IP)) {
                header_length = sizeof(struct iphdr) + sizeof(struct icmphdr);
                total_length = min_t(unsigned int, header_length +
                                                   payload_length, 576);
        }
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
        else {
                header_length = sizeof(struct ipv6hdr) +
                                sizeof(struct icmp6hdr);
                total_length = min_t(unsigned int, header_length +
                                                  payload_length, IPV6_MIN_MTU);
        }
#endif

        total_length = min(total_length, mutable->mtu);
        payload_length = total_length - header_length;

        nskb = dev_alloc_skb(NET_IP_ALIGN + eth_hdr_len + header_length +
                             payload_length);
        if (!nskb)
                return false;

        skb_reserve(nskb, NET_IP_ALIGN);

        /* Ethernet / VLAN */
        eh = (struct ethhdr *)skb_put(nskb, eth_hdr_len);
        memcpy(eh->h_dest, old_eh->h_source, ETH_ALEN);
        memcpy(eh->h_source, mutable->eth_addr, ETH_ALEN);
        nskb->protocol = eh->h_proto = old_eh->h_proto;
        if (old_eh->h_proto == htons(ETH_P_8021Q)) {
                struct vlan_ethhdr *vh = (struct vlan_ethhdr *)eh;

                vh->h_vlan_TCI = vlan_eth_hdr(skb)->h_vlan_TCI;
                vh->h_vlan_encapsulated_proto = skb->protocol;
        }
        skb_reset_mac_header(nskb);

        /* Protocol */
        if (skb->protocol == htons(ETH_P_IP))
                ipv4_build_icmp(skb, nskb, mtu, payload_length);
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
        else
                ipv6_build_icmp(skb, nskb, mtu, payload_length);
#endif

        /*
         * Assume that flow based keys are symmetric with respect to input
         * and output and use the key that we were going to put on the
         * outgoing packet for the fake received packet.  If the keys are
         * not symmetric then PMTUD needs to be disabled since we won't have
         * any way of synthesizing packets.
         */
        if ((mutable->port_config.flags & (TNL_F_IN_KEY_MATCH | TNL_F_OUT_KEY_ACTION)) ==
            (TNL_F_IN_KEY_MATCH | TNL_F_OUT_KEY_ACTION))
                OVS_CB(nskb)->tun_id = flow_key;

        compute_ip_summed(nskb, false);
        vport_receive(vport, nskb);

        return true;
}

static bool check_mtu(struct sk_buff *skb,
                      struct vport *vport,
                      const struct tnl_mutable_config *mutable,
                      const struct rtable *rt, __be16 *frag_offp)
{
        int mtu;
        __be16 frag_off;

        frag_off = (mutable->port_config.flags & TNL_F_PMTUD) ? htons(IP_DF) : 0;
        if (frag_off)
                mtu = dst_mtu(&rt_dst(rt))
                        - ETH_HLEN
                        - mutable->tunnel_hlen
                        - (eth_hdr(skb)->h_proto == htons(ETH_P_8021Q) ? VLAN_HLEN : 0);
        else
                mtu = mutable->mtu;

        if (skb->protocol == htons(ETH_P_IP)) {
                struct iphdr *old_iph = ip_hdr(skb);

                frag_off |= old_iph->frag_off & htons(IP_DF);
                mtu = max(mtu, IP_MIN_MTU);

                if ((old_iph->frag_off & htons(IP_DF)) &&
                    mtu < ntohs(old_iph->tot_len)) {
                        if (tnl_frag_needed(vport, mutable, skb, mtu, OVS_CB(skb)->tun_id))
                                goto drop;
                }
        }
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
        else if (skb->protocol == htons(ETH_P_IPV6)) {
                unsigned int packet_length = skb->len - ETH_HLEN
                        - (eth_hdr(skb)->h_proto == htons(ETH_P_8021Q) ? VLAN_HLEN : 0);

                mtu = max(mtu, IPV6_MIN_MTU);

                /* IPv6 requires PMTUD if the packet is above the minimum MTU. */
                if (packet_length > IPV6_MIN_MTU)
                        frag_off = htons(IP_DF);

                if (mtu < packet_length) {
                        if (tnl_frag_needed(vport, mutable, skb, mtu, OVS_CB(skb)->tun_id))
                                goto drop;
                }
        }
#endif

        *frag_offp = frag_off;
        return true;

drop:
        *frag_offp = 0;
        return false;
}

static void create_tunnel_header(const struct vport *vport,
                                 const struct tnl_mutable_config *mutable,
                                 const struct rtable *rt, void *header)
{
        struct tnl_vport *tnl_vport = tnl_vport_priv(vport);
        struct iphdr *iph = header;

        iph->version    = 4;
        iph->ihl        = sizeof(struct iphdr) >> 2;
        iph->frag_off   = htons(IP_DF);
        iph->protocol   = tnl_vport->tnl_ops->ipproto;
        iph->tos        = mutable->port_config.tos;
        iph->daddr      = rt->rt_dst;
        iph->saddr      = rt->rt_src;
        iph->ttl        = mutable->port_config.ttl;
        if (!iph->ttl)
                iph->ttl = dst_metric(&rt_dst(rt), RTAX_HOPLIMIT);

        tnl_vport->tnl_ops->build_header(vport, mutable, iph + 1);
}

static inline void *get_cached_header(const struct tnl_cache *cache)
{
        return (void *)cache + ALIGN(sizeof(struct tnl_cache), CACHE_DATA_ALIGN);
}

static inline bool check_cache_valid(const struct tnl_cache *cache,
                                     const struct tnl_mutable_config *mutable)
{
        return cache &&
#ifdef NEED_CACHE_TIMEOUT
                time_before(jiffies, cache->expiration) &&
#endif
#ifdef HAVE_RT_GENID
                atomic_read(&init_net.ipv4.rt_genid) == cache->rt->rt_genid &&
#endif
#ifdef HAVE_HH_SEQ
                rt_dst(cache->rt).hh->hh_lock.sequence == cache->hh_seq &&
#endif
                mutable->seq == cache->mutable_seq &&
                (!is_internal_dev(rt_dst(cache->rt).dev) ||
                (cache->flow && !cache->flow->dead));
}

static int cache_cleaner_cb(struct tbl_node *tbl_node, void *aux)
{
        struct tnl_vport *tnl_vport = tnl_vport_table_cast(tbl_node);
        const struct tnl_mutable_config *mutable = rcu_dereference(tnl_vport->mutable);
        const struct tnl_cache *cache = rcu_dereference(tnl_vport->cache);

        if (cache && !check_cache_valid(cache, mutable) &&
            spin_trylock_bh(&tnl_vport->cache_lock)) {
                assign_cache_rcu(tnl_vport_to_vport(tnl_vport), NULL);
                spin_unlock_bh(&tnl_vport->cache_lock);
        }

        return 0;
}

static void cache_cleaner(struct work_struct *work)
{
        schedule_cache_cleaner();

        rcu_read_lock();
        tbl_foreach(port_table, cache_cleaner_cb, NULL);
        rcu_read_unlock();
}

static inline void create_eth_hdr(struct tnl_cache *cache,
                                  const struct rtable *rt)
{
        void *cache_data = get_cached_header(cache);
        int hh_len = rt_dst(rt).hh->hh_len;
        int hh_off = HH_DATA_ALIGN(rt_dst(rt).hh->hh_len) - hh_len;

#ifdef HAVE_HH_SEQ
        unsigned hh_seq;

        do {
                hh_seq = read_seqbegin(&rt_dst(rt).hh->hh_lock);
                memcpy(cache_data, (void *)rt_dst(rt).hh->hh_data + hh_off, hh_len);
        } while (read_seqretry(&rt_dst(rt).hh->hh_lock, hh_seq));

        cache->hh_seq = hh_seq;
#else
        read_lock_bh(&rt_dst(rt).hh->hh_lock);
        memcpy(cache_data, (void *)rt_dst(rt).hh->hh_data + hh_off, hh_len);
        read_unlock_bh(&rt_dst(rt).hh->hh_lock);
#endif
}

static struct tnl_cache *build_cache(struct vport *vport,
                                     const struct tnl_mutable_config *mutable,
                                     struct rtable *rt)
{
        struct tnl_vport *tnl_vport = tnl_vport_priv(vport);
        struct tnl_cache *cache;
        void *cache_data;
        int cache_len;

        if (!(mutable->port_config.flags & TNL_F_HDR_CACHE))
                return NULL;

        /*
         * If there is no entry in the ARP cache or if this device does not
         * support hard header caching just fall back to the IP stack.
         */
        if (!rt_dst(rt).hh)
                return NULL;

        /*
         * If lock is contended fall back to directly building the header.
         * We're not going to help performance by sitting here spinning.
         */
        if (!spin_trylock_bh(&tnl_vport->cache_lock))
                return NULL;

        cache = tnl_vport->cache;
        if (check_cache_valid(cache, mutable))
                goto unlock;
        else
                cache = NULL;

        cache_len = rt_dst(rt).hh->hh_len + mutable->tunnel_hlen;

        cache = kzalloc(ALIGN(sizeof(struct tnl_cache), CACHE_DATA_ALIGN) +
                        cache_len, GFP_ATOMIC);
        if (!cache)
                goto unlock;

        cache->len = cache_len;

        create_eth_hdr(cache, rt);
        cache_data = get_cached_header(cache) + rt_dst(rt).hh->hh_len;

        create_tunnel_header(vport, mutable, rt, cache_data);

        cache->mutable_seq = mutable->seq;
        cache->rt = rt;
#ifdef NEED_CACHE_TIMEOUT
        cache->expiration = jiffies + tnl_vport->cache_exp_interval;
#endif

        if (is_internal_dev(rt_dst(rt).dev)) {
                struct odp_flow_key flow_key;
                struct tbl_node *flow_node;
                struct vport *vport;
                struct sk_buff *skb;
                bool is_frag;
                int err;

                vport = internal_dev_get_vport(rt_dst(rt).dev);
                if (!vport)
                        goto done;

                skb = alloc_skb(cache->len, GFP_ATOMIC);
                if (!skb)
                        goto done;

                __skb_put(skb, cache->len);
                memcpy(skb->data, get_cached_header(cache), cache->len);

                err = flow_extract(skb, vport->port_no, &flow_key, &is_frag);

                kfree_skb(skb);
                if (err || is_frag)
                        goto done;

                flow_node = tbl_lookup(rcu_dereference(vport->dp->table),
                                       &flow_key, flow_hash(&flow_key),
                                       flow_cmp);
                if (flow_node) {
                        struct sw_flow *flow = flow_cast(flow_node);

                        cache->flow = flow;
                        flow_hold(flow);
                }
        }

done:
        assign_cache_rcu(vport, cache);

unlock:
        spin_unlock_bh(&tnl_vport->cache_lock);

        return cache;
}

static struct rtable *find_route(struct vport *vport,
                                 const struct tnl_mutable_config *mutable,
                                 u8 tos, struct tnl_cache **cache)
{
        struct tnl_vport *tnl_vport = tnl_vport_priv(vport);
        struct tnl_cache *cur_cache = rcu_dereference(tnl_vport->cache);

        *cache = NULL;
        tos = RT_TOS(tos);

        if (likely(tos == mutable->port_config.tos &&
                   check_cache_valid(cur_cache, mutable))) {
                *cache = cur_cache;
                return cur_cache->rt;
        } else {
                struct rtable *rt;
                struct flowi fl = { .nl_u = { .ip4_u =
                                              { .daddr = mutable->port_config.daddr,
                                                .saddr = mutable->port_config.saddr,
                                                .tos = tos } },
                                    .proto = tnl_vport->tnl_ops->ipproto };

                if (unlikely(ip_route_output_key(&init_net, &rt, &fl)))
                        return NULL;

                if (likely(tos == mutable->port_config.tos))
                        *cache = build_cache(vport, mutable, rt);

                return rt;
        }
}

static struct sk_buff *check_headroom(struct sk_buff *skb, int headroom)
{
        if (skb_headroom(skb) < headroom || skb_header_cloned(skb)) {
                struct sk_buff *nskb = skb_realloc_headroom(skb, headroom + 16);
                if (unlikely(!nskb)) {
                        kfree_skb(skb);
                        return ERR_PTR(-ENOMEM);
                }

                set_skb_csum_bits(skb, nskb);

                if (skb->sk)
                        skb_set_owner_w(nskb, skb->sk);

                kfree_skb(skb);
                return nskb;
        }

        return skb;
}

static inline bool need_linearize(const struct sk_buff *skb)
{
        int i;

        if (unlikely(skb_shinfo(skb)->frag_list))
                return true;

        /*
         * Generally speaking we should linearize if there are paged frags.
         * However, if all of the refcounts are 1 we know nobody else can
         * change them from underneath us and we can skip the linearization.
         */
        for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
                if (unlikely(page_count(skb_shinfo(skb)->frags[0].page) > 1))
                        return true;

        return false;
}

static struct sk_buff *handle_offloads(struct sk_buff *skb,
                                       const struct tnl_mutable_config *mutable,
                                       const struct rtable *rt)
{
        int min_headroom;
        int err;

        forward_ip_summed(skb);

        err = vswitch_skb_checksum_setup(skb);
        if (unlikely(err))
                goto error_free;

        min_headroom = LL_RESERVED_SPACE(rt_dst(rt).dev) + rt_dst(rt).header_len
                        + mutable->tunnel_hlen;

        if (skb_is_gso(skb)) {
                struct sk_buff *nskb;

                /*
                 * If we are doing GSO on a pskb it is better to make sure that
                 * the headroom is correct now.  We will only have to copy the
                 * portion in the linear data area and GSO will preserve
                 * headroom when it creates the segments.  This is particularly
                 * beneficial on Xen where we get a lot of GSO pskbs.
                 * Conversely, we avoid copying if it is just to get our own
                 * writable clone because GSO will do the copy for us.
                 */
                if (skb_headroom(skb) < min_headroom) {
                        skb = check_headroom(skb, min_headroom);
                        if (unlikely(IS_ERR(skb))) {
                                err = PTR_ERR(skb);
                                goto error;
                        }
                }

                nskb = skb_gso_segment(skb, 0);
                kfree_skb(skb);
                if (unlikely(IS_ERR(nskb))) {
                        err = PTR_ERR(nskb);
                        goto error;
                }

                skb = nskb;
        } else {
                skb = check_headroom(skb, min_headroom);
                if (unlikely(IS_ERR(skb))) {
                        err = PTR_ERR(skb);
                        goto error;
                }

                if (skb->ip_summed == CHECKSUM_PARTIAL) {
                        /*
                         * Pages aren't locked and could change at any time.
                         * If this happens after we compute the checksum, the
                         * checksum will be wrong.  We linearize now to avoid
                         * this problem.
                         */
                        if (unlikely(need_linearize(skb))) {
                                err = __skb_linearize(skb);
                                if (unlikely(err))
                                        goto error_free;
                        }

                        err = skb_checksum_help(skb);
                        if (unlikely(err))
                                goto error_free;
                } else if (skb->ip_summed == CHECKSUM_COMPLETE)
                        skb->ip_summed = CHECKSUM_NONE;
        }

        return skb;

error_free:
        kfree_skb(skb);
error:
        return ERR_PTR(err);
}

static int send_frags(struct sk_buff *skb,
                      const struct tnl_mutable_config *mutable)
{
        int sent_len;
        int err;

        sent_len = 0;
        while (skb) {
                struct sk_buff *next = skb->next;
                int frag_len = skb->len - mutable->tunnel_hlen;

                skb->next = NULL;
                memset(IPCB(skb), 0, sizeof(*IPCB(skb)));

                err = ip_local_out(skb);
                if (likely(net_xmit_eval(err) == 0))
                        sent_len += frag_len;
                else {
                        skb = next;
                        goto free_frags;
                }

                skb = next;
        }

        return sent_len;

free_frags:
        /*
         * There's no point in continuing to send fragments once one has been
         * dropped so just free the rest.  This may help improve the congestion
         * that caused the first packet to be dropped.
         */
        tnl_free_linked_skbs(skb);
        return sent_len;
}

int tnl_send(struct vport *vport, struct sk_buff *skb)
{
        struct tnl_vport *tnl_vport = tnl_vport_priv(vport);
        const struct tnl_mutable_config *mutable = rcu_dereference(tnl_vport->mutable);

        enum vport_err_type err = VPORT_E_TX_ERROR;
        struct rtable *rt;
        struct dst_entry *unattached_dst = NULL;
        struct tnl_cache *cache;
        int sent_len = 0;
        __be16 frag_off;
        u8 ttl;
        u8 inner_tos;
        u8 tos;

        /* Validate the protocol headers before we try to use them. */
        if (skb->protocol == htons(ETH_P_8021Q)) {
                if (unlikely(!pskb_may_pull(skb, VLAN_ETH_HLEN)))
                        goto error_free;

                skb->protocol = vlan_eth_hdr(skb)->h_vlan_encapsulated_proto;
                skb_set_network_header(skb, VLAN_ETH_HLEN);
        }

        if (skb->protocol == htons(ETH_P_IP)) {
                if (unlikely(!pskb_may_pull(skb, skb_network_offset(skb)
                    + sizeof(struct iphdr))))
                        skb->protocol = 0;
        }
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
        else if (skb->protocol == htons(ETH_P_IPV6)) {
                if (unlikely(!pskb_may_pull(skb, skb_network_offset(skb)
                    + sizeof(struct ipv6hdr))))
                        skb->protocol = 0;
        }
#endif

        /* ToS */
        if (skb->protocol == htons(ETH_P_IP))
                inner_tos = ip_hdr(skb)->tos;
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
        else if (skb->protocol == htons(ETH_P_IPV6))
                inner_tos = ipv6_get_dsfield(ipv6_hdr(skb));
#endif
        else
                inner_tos = 0;

        if (mutable->port_config.flags & TNL_F_TOS_INHERIT)
                tos = inner_tos;
        else
                tos = mutable->port_config.tos;

        tos = INET_ECN_encapsulate(tos, inner_tos);

        /* Route lookup */
        rt = find_route(vport, mutable, tos, &cache);
        if (unlikely(!rt))
                goto error_free;
        if (unlikely(!cache))
                unattached_dst = &rt_dst(rt);

        /* Reset SKB */
        nf_reset(skb);
        secpath_reset(skb);
        skb_dst_drop(skb);

        /* Offloading */
        skb = handle_offloads(skb, mutable, rt);
        if (unlikely(IS_ERR(skb)))
                goto error;

        /* MTU */
        if (unlikely(!check_mtu(skb, vport, mutable, rt, &frag_off))) {
                err = VPORT_E_TX_DROPPED;
                goto error_free;
        }

        /*
         * If we are over the MTU, allow the IP stack to handle fragmentation.
         * Fragmentation is a slow path anyways.
         */
        if (unlikely(skb->len + mutable->tunnel_hlen > dst_mtu(&rt_dst(rt)) &&
                     cache)) {
                unattached_dst = &rt_dst(rt);
                dst_hold(unattached_dst);
                cache = NULL;
        }

        /* TTL */
        ttl = mutable->port_config.ttl;
        if (!ttl)
                ttl = dst_metric(&rt_dst(rt), RTAX_HOPLIMIT);

        if (mutable->port_config.flags & TNL_F_TTL_INHERIT) {
                if (skb->protocol == htons(ETH_P_IP))
                        ttl = ip_hdr(skb)->ttl;
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
                else if (skb->protocol == htons(ETH_P_IPV6))
                        ttl = ipv6_hdr(skb)->hop_limit;
#endif
        }

        while (skb) {
                struct iphdr *iph;
                struct sk_buff *next_skb = skb->next;
                skb->next = NULL;

                if (likely(cache)) {
                        skb_push(skb, cache->len);
                        memcpy(skb->data, get_cached_header(cache), cache->len);
                        skb_reset_mac_header(skb);
                        skb_set_network_header(skb, rt_dst(rt).hh->hh_len);

                } else {
                        skb_push(skb, mutable->tunnel_hlen);
                        create_tunnel_header(vport, mutable, rt, skb->data);
                        skb_reset_network_header(skb);

                        if (next_skb)
                                skb_dst_set(skb, dst_clone(unattached_dst));
                        else {
                                skb_dst_set(skb, unattached_dst);
                                unattached_dst = NULL;
                        }
                }
                skb_set_transport_header(skb, skb_network_offset(skb) + sizeof(struct iphdr));

                iph = ip_hdr(skb);
                iph->tos = tos;
                iph->ttl = ttl;
                iph->frag_off = frag_off;
                ip_select_ident(iph, &rt_dst(rt), NULL);

                skb = tnl_vport->tnl_ops->update_header(vport, mutable, &rt_dst(rt), skb);
                if (unlikely(!skb))
                        goto next;

                if (likely(cache)) {
                        int orig_len = skb->len - cache->len;
                        struct vport *cache_vport = internal_dev_get_vport(rt_dst(rt).dev);

                        skb->protocol = htons(ETH_P_IP);
                        iph->tot_len = htons(skb->len - skb_network_offset(skb));
                        ip_send_check(iph);

                        if (cache_vport) {
                                OVS_CB(skb)->flow = cache->flow;
                                compute_ip_summed(skb, true);
                                vport_receive(cache_vport, skb);
                                sent_len += orig_len;
                        } else {
                                int err;

                                skb->dev = rt_dst(rt).dev;
                                err = dev_queue_xmit(skb);

                                if (likely(net_xmit_eval(err) == 0))
                                        sent_len += orig_len;
                        }
                } else
                        sent_len += send_frags(skb, mutable);

next:
                skb = next_skb;
        }

        if (unlikely(sent_len == 0))
                vport_record_error(vport, VPORT_E_TX_DROPPED);

        goto out;

error_free:
        tnl_free_linked_skbs(skb);
error:
        dst_release(unattached_dst);
        vport_record_error(vport, err);
out:
        return sent_len;
}

static int set_config(const void *config, const struct tnl_ops *tnl_ops,
                      const struct vport *cur_vport,
                      struct tnl_mutable_config *mutable)
{
        const struct vport *old_vport;
        const struct tnl_mutable_config *old_mutable;

        mutable->port_config = *(struct tnl_port_config *)config;

        if (mutable->port_config.daddr == 0)
                return -EINVAL;

        if (mutable->port_config.tos != RT_TOS(mutable->port_config.tos))
                return -EINVAL;

        mutable->tunnel_hlen = tnl_ops->hdr_len(&mutable->port_config);
        if (mutable->tunnel_hlen < 0)
                return mutable->tunnel_hlen;

        mutable->tunnel_hlen += sizeof(struct iphdr);

        mutable->tunnel_type = tnl_ops->tunnel_type;
        if (mutable->port_config.flags & TNL_F_IN_KEY_MATCH) {
                mutable->tunnel_type |= TNL_T_KEY_MATCH;
                mutable->port_config.in_key = 0;
        } else
                mutable->tunnel_type |= TNL_T_KEY_EXACT;

        old_vport = tnl_find_port(mutable->port_config.saddr,
                                  mutable->port_config.daddr,
                                  mutable->port_config.in_key,
                                  mutable->tunnel_type,
                                  &old_mutable);

        if (old_vport && old_vport != cur_vport)
                return -EEXIST;

        if (mutable->port_config.flags & TNL_F_OUT_KEY_ACTION)
                mutable->port_config.out_key = 0;

        return 0;
}

struct vport *tnl_create(const struct vport_parms *parms,
                         const struct vport_ops *vport_ops,
                         const struct tnl_ops *tnl_ops)
{
        struct vport *vport;
        struct tnl_vport *tnl_vport;
        int initial_frag_id;
        int err;

        vport = vport_alloc(sizeof(struct tnl_vport), vport_ops, parms);
        if (IS_ERR(vport)) {
                err = PTR_ERR(vport);
                goto error;
        }

        tnl_vport = tnl_vport_priv(vport);

        strcpy(tnl_vport->name, parms->name);
        tnl_vport->tnl_ops = tnl_ops;

        tnl_vport->mutable = kzalloc(sizeof(struct tnl_mutable_config), GFP_KERNEL);
        if (!tnl_vport->mutable) {
                err = -ENOMEM;
                goto error_free_vport;
        }

        vport_gen_rand_ether_addr(tnl_vport->mutable->eth_addr);
        tnl_vport->mutable->mtu = ETH_DATA_LEN;

        get_random_bytes(&initial_frag_id, sizeof(int));
        atomic_set(&tnl_vport->frag_id, initial_frag_id);

        err = set_config(parms->config, tnl_ops, NULL, tnl_vport->mutable);
        if (err)
                goto error_free_mutable;

        spin_lock_init(&tnl_vport->cache_lock);

#ifdef NEED_CACHE_TIMEOUT
        tnl_vport->cache_exp_interval = MAX_CACHE_EXP -
                                        (net_random() % (MAX_CACHE_EXP / 2));
#endif

        err = add_port(vport);
        if (err)
                goto error_free_mutable;

        return vport;

error_free_mutable:
        kfree(tnl_vport->mutable);
error_free_vport:
        vport_free(vport);
error:
        return ERR_PTR(err);
}

int tnl_modify(struct vport *vport, struct odp_port *port)
{
        struct tnl_vport *tnl_vport = tnl_vport_priv(vport);
        struct tnl_mutable_config *mutable;
        int err;

        mutable = kmemdup(tnl_vport->mutable, sizeof(struct tnl_mutable_config), GFP_KERNEL);
        if (!mutable) {
                err = -ENOMEM;
                goto error;
        }

        err = set_config(port->config, tnl_vport->tnl_ops, vport, mutable);
        if (err)
                goto error_free;

        mutable->seq++;

        err = move_port(vport, mutable);
        if (err)
                goto error_free;

        return 0;

error_free:
        kfree(mutable);
error:
        return err;
}

static void free_port_rcu(struct rcu_head *rcu)
{
        struct tnl_vport *tnl_vport = container_of(rcu, struct tnl_vport, rcu);

        spin_lock_bh(&tnl_vport->cache_lock);
        free_cache(tnl_vport->cache);
        spin_unlock_bh(&tnl_vport->cache_lock);

        kfree(tnl_vport->mutable);
        vport_free(tnl_vport_to_vport(tnl_vport));
}

int tnl_destroy(struct vport *vport)
{
        struct tnl_vport *tnl_vport = tnl_vport_priv(vport);
        const struct tnl_mutable_config *old_mutable;

        if (vport == tnl_find_port(tnl_vport->mutable->port_config.saddr,
            tnl_vport->mutable->port_config.daddr,
            tnl_vport->mutable->port_config.in_key,
            tnl_vport->mutable->tunnel_type,
            &old_mutable))
                del_port(vport);

        call_rcu(&tnl_vport->rcu, free_port_rcu);

        return 0;
}

int tnl_set_mtu(struct vport *vport, int mtu)
{
        struct tnl_vport *tnl_vport = tnl_vport_priv(vport);
        struct tnl_mutable_config *mutable;

        mutable = kmemdup(tnl_vport->mutable, sizeof(struct tnl_mutable_config), GFP_KERNEL);
        if (!mutable)
                return -ENOMEM;

        mutable->mtu = mtu;
        assign_config_rcu(vport, mutable);

        return 0;
}

int tnl_set_addr(struct vport *vport, const unsigned char *addr)
{
        struct tnl_vport *tnl_vport = tnl_vport_priv(vport);
        struct tnl_mutable_config *mutable;

        mutable = kmemdup(tnl_vport->mutable, sizeof(struct tnl_mutable_config), GFP_KERNEL);
        if (!mutable)
                return -ENOMEM;

        memcpy(mutable->eth_addr, addr, ETH_ALEN);
        assign_config_rcu(vport, mutable);

        return 0;
}

const char *tnl_get_name(const struct vport *vport)
{
        const struct tnl_vport *tnl_vport = tnl_vport_priv(vport);
        return tnl_vport->name;
}

const unsigned char *tnl_get_addr(const struct vport *vport)
{
        const struct tnl_vport *tnl_vport = tnl_vport_priv(vport);
        return rcu_dereference(tnl_vport->mutable)->eth_addr;
}

int tnl_get_mtu(const struct vport *vport)
{
        const struct tnl_vport *tnl_vport = tnl_vport_priv(vport);
        return rcu_dereference(tnl_vport->mutable)->mtu;
}

void tnl_free_linked_skbs(struct sk_buff *skb)
{
        if (unlikely(!skb))
                return;

        while (skb) {
                struct sk_buff *next = skb->next;
                kfree_skb(skb);
                skb = next;
        }
}