/*
 *      IPV4 GSO/GRO offload support
 *      Linux INET implementation
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 *
 *      UDPv4 GSO support
 */

#include <linux/skbuff.h>
#include <net/udp.h>
#include <net/protocol.h>

static DEFINE_SPINLOCK(udp_offload_lock);
static struct udp_offload_priv __rcu *udp_offload_base __read_mostly;

#define udp_deref_protected(X) rcu_dereference_protected(X, lockdep_is_held(&udp_offload_lock))

struct udp_offload_priv {
        struct udp_offload      *offload;
        struct rcu_head         rcu;
        struct udp_offload_priv __rcu *next;
};

static int udp4_ufo_send_check(struct sk_buff *skb)
{
        if (!pskb_may_pull(skb, sizeof(struct udphdr)))
                return -EINVAL;

        if (likely(!skb->encapsulation)) {
                const struct iphdr *iph;
                struct udphdr *uh;

                iph = ip_hdr(skb);
                uh = udp_hdr(skb);

                uh->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, skb->len,
                                IPPROTO_UDP, 0);
                skb->csum_start = skb_transport_header(skb) - skb->head;
                skb->csum_offset = offsetof(struct udphdr, check);
                skb->ip_summed = CHECKSUM_PARTIAL;
        }

        return 0;
}

static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
                                         netdev_features_t features)
{
        struct sk_buff *segs = ERR_PTR(-EINVAL);
        unsigned int mss;
        int offset;
        __wsum csum;

        if (skb->encapsulation &&
            skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL) {
                segs = skb_udp_tunnel_segment(skb, features);
                goto out;
        }

        mss = skb_shinfo(skb)->gso_size;
        if (unlikely(skb->len <= mss))
                goto out;

        if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
                /* Packet is from an untrusted source, reset gso_segs. */
                int type = skb_shinfo(skb)->gso_type;

                if (unlikely(type & ~(SKB_GSO_UDP | SKB_GSO_DODGY |
                                      SKB_GSO_UDP_TUNNEL |
                                      SKB_GSO_IPIP |
                                      SKB_GSO_GRE | SKB_GSO_MPLS) ||
                             !(type & (SKB_GSO_UDP))))
                        goto out;

                skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);

                segs = NULL;
                goto out;
        }

        /* Do software UFO. Complete and fill in the UDP checksum as
         * HW cannot do checksum of UDP packets sent as multiple
         * IP fragments.
         */
        offset = skb_checksum_start_offset(skb);
        csum = skb_checksum(skb, offset, skb->len - offset, 0);
        offset += skb->csum_offset;
        *(__sum16 *)(skb->data + offset) = csum_fold(csum);
        skb->ip_summed = CHECKSUM_NONE;

        /* Fragment the skb. IP headers of the fragments are updated in
         * inet_gso_segment()
         */
        segs = skb_segment(skb, features);
out:
        return segs;
}

int udp_add_offload(struct udp_offload *uo)
{
        struct udp_offload_priv *new_offload = kzalloc(sizeof(*new_offload), GFP_ATOMIC);

        if (!new_offload)
                return -ENOMEM;

        new_offload->offload = uo;

        spin_lock(&udp_offload_lock);
        new_offload->next = udp_offload_base;
        rcu_assign_pointer(udp_offload_base, new_offload);
        spin_unlock(&udp_offload_lock);

        return 0;
}
EXPORT_SYMBOL(udp_add_offload);

static void udp_offload_free_routine(struct rcu_head *head)
{
        struct udp_offload_priv *ou_priv = container_of(head, struct udp_offload_priv, rcu);
        kfree(ou_priv);
}

void udp_del_offload(struct udp_offload *uo)
{
        struct udp_offload_priv __rcu **head = &udp_offload_base;
        struct udp_offload_priv *uo_priv;

        spin_lock(&udp_offload_lock);

        uo_priv = udp_deref_protected(*head);
        for (; uo_priv != NULL;
             uo_priv = udp_deref_protected(*head)) {
                if (uo_priv->offload == uo) {
                        rcu_assign_pointer(*head,
                                           udp_deref_protected(uo_priv->next));
                        goto unlock;
                }
                head = &uo_priv->next;
        }
        pr_warn("udp_del_offload: didn't find offload for port %d\n", ntohs(uo->port));
unlock:
        spin_unlock(&udp_offload_lock);
        if (uo_priv != NULL)
                call_rcu(&uo_priv->rcu, udp_offload_free_routine);
}
EXPORT_SYMBOL(udp_del_offload);

static struct sk_buff **udp_gro_receive(struct sk_buff **head, struct sk_buff *skb)
{
        struct udp_offload_priv *uo_priv;
        struct sk_buff *p, **pp = NULL;
        struct udphdr *uh, *uh2;
        unsigned int hlen, off;
        int flush = 1;

        if (NAPI_GRO_CB(skb)->udp_mark ||
            (!skb->encapsulation && skb->ip_summed != CHECKSUM_COMPLETE))
                goto out;

        /* mark that this skb passed once through the udp gro layer */
        NAPI_GRO_CB(skb)->udp_mark = 1;

        off  = skb_gro_offset(skb);
        hlen = off + sizeof(*uh);
        uh   = skb_gro_header_fast(skb, off);
        if (skb_gro_header_hard(skb, hlen)) {
                uh = skb_gro_header_slow(skb, hlen, off);
                if (unlikely(!uh))
                        goto out;
        }

        rcu_read_lock();
        uo_priv = rcu_dereference(udp_offload_base);
        for (; uo_priv != NULL; uo_priv = rcu_dereference(uo_priv->next)) {
                if (uo_priv->offload->port == uh->dest &&
                    uo_priv->offload->callbacks.gro_receive)
                        goto unflush;
        }
        goto out_unlock;

unflush:
        flush = 0;

        for (p = *head; p; p = p->next) {
                if (!NAPI_GRO_CB(p)->same_flow)
                        continue;

                uh2 = (struct udphdr   *)(p->data + off);
                if ((*(u32 *)&uh->source != *(u32 *)&uh2->source)) {
                        NAPI_GRO_CB(p)->same_flow = 0;
                        continue;
                }
        }

        skb_gro_pull(skb, sizeof(struct udphdr)); /* pull encapsulating udp header */
        pp = uo_priv->offload->callbacks.gro_receive(head, skb);

out_unlock:
        rcu_read_unlock();
out:
        NAPI_GRO_CB(skb)->flush |= flush;
        return pp;
}

static int udp_gro_complete(struct sk_buff *skb, int nhoff)
{
        struct udp_offload_priv *uo_priv;
        __be16 newlen = htons(skb->len - nhoff);
        struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);
        int err = -ENOSYS;

        uh->len = newlen;

        rcu_read_lock();

        uo_priv = rcu_dereference(udp_offload_base);
        for (; uo_priv != NULL; uo_priv = rcu_dereference(uo_priv->next)) {
                if (uo_priv->offload->port == uh->dest &&
                    uo_priv->offload->callbacks.gro_complete)
                        break;
        }

        if (uo_priv != NULL)
                err = uo_priv->offload->callbacks.gro_complete(skb, nhoff + sizeof(struct udphdr));

        rcu_read_unlock();
        return err;
}

static const struct net_offload udpv4_offload = {
        .callbacks = {
                .gso_send_check = udp4_ufo_send_check,
                .gso_segment = udp4_ufo_fragment,
                .gro_receive  = udp_gro_receive,
                .gro_complete = udp_gro_complete,
        },
};

int __init udpv4_offload_init(void)
{
        return inet_add_offload(&udpv4_offload, IPPROTO_UDP);
}