/*
 *      IPV6 GSO/GRO offload support
 *      Linux INET6 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.
 *
 *      UDPv6 GSO support
 */
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <net/protocol.h>
#include <net/ipv6.h>
#include <net/udp.h>
#include <net/ip6_checksum.h>
#include "ip6_offload.h"

static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
                                         netdev_features_t features)
{
        struct sk_buff *segs = ERR_PTR(-EINVAL);
        unsigned int mss;
        unsigned int unfrag_ip6hlen, unfrag_len;
        struct frag_hdr *fptr;
        u8 *packet_start, *prevhdr;
        u8 nexthdr;
        u8 frag_hdr_sz = sizeof(struct frag_hdr);
        __wsum csum;
        int tnl_hlen;
        int err;

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

        if (skb->encapsulation && skb_shinfo(skb)->gso_type &
            (SKB_GSO_UDP_TUNNEL|SKB_GSO_UDP_TUNNEL_CSUM))
                segs = skb_udp_tunnel_segment(skb, features, true);
        else {
                const struct ipv6hdr *ipv6h;
                struct udphdr *uh;

                if (!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP))
                        goto out;

                if (!pskb_may_pull(skb, sizeof(struct udphdr)))
                        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.
                 */

                uh = udp_hdr(skb);
                ipv6h = ipv6_hdr(skb);

                uh->check = 0;
                csum = skb_checksum(skb, 0, skb->len, 0);
                uh->check = udp_v6_check(skb->len, &ipv6h->saddr,
                                          &ipv6h->daddr, csum);
                if (uh->check == 0)
                        uh->check = CSUM_MANGLED_0;

                skb->ip_summed = CHECKSUM_UNNECESSARY;

                /* If there is no outer header we can fake a checksum offload
                 * due to the fact that we have already done the checksum in
                 * software prior to segmenting the frame.
                 */
                if (!skb->encap_hdr_csum)
                        features |= NETIF_F_HW_CSUM;

                /* Check if there is enough headroom to insert fragment header. */
                tnl_hlen = skb_tnl_header_len(skb);
                if (skb->mac_header < (tnl_hlen + frag_hdr_sz)) {
                        if (gso_pskb_expand_head(skb, tnl_hlen + frag_hdr_sz))
                                goto out;
                }

                /* Find the unfragmentable header and shift it left by frag_hdr_sz
                 * bytes to insert fragment header.
                 */
                err = ip6_find_1stfragopt(skb, &prevhdr);
                if (err < 0)
                        return ERR_PTR(err);
                unfrag_ip6hlen = err;
                nexthdr = *prevhdr;
                *prevhdr = NEXTHDR_FRAGMENT;
                unfrag_len = (skb_network_header(skb) - skb_mac_header(skb)) +
                             unfrag_ip6hlen + tnl_hlen;
                packet_start = (u8 *) skb->head + SKB_GSO_CB(skb)->mac_offset;
                memmove(packet_start-frag_hdr_sz, packet_start, unfrag_len);

                SKB_GSO_CB(skb)->mac_offset -= frag_hdr_sz;
                skb->mac_header -= frag_hdr_sz;
                skb->network_header -= frag_hdr_sz;

                fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen);
                fptr->nexthdr = nexthdr;
                fptr->reserved = 0;
                fptr->identification = ipv6_proxy_select_ident(dev_net(skb->dev), skb);

                /* Fragment the skb. ipv6 header and the remaining fields of the
                 * fragment header are updated in ipv6_gso_segment()
                 */
                segs = skb_segment(skb, features);
        }

out:
        return segs;
}

static struct sk_buff **udp6_gro_receive(struct sk_buff **head,
                                         struct sk_buff *skb)
{
        struct udphdr *uh = udp_gro_udphdr(skb);

        if (unlikely(!uh))
                goto flush;

        /* Don't bother verifying checksum if we're going to flush anyway. */
        if (NAPI_GRO_CB(skb)->flush)
                goto skip;

        if (skb_gro_checksum_validate_zero_check(skb, IPPROTO_UDP, uh->check,
                                                 ip6_gro_compute_pseudo))
                goto flush;
        else if (uh->check)
                skb_gro_checksum_try_convert(skb, IPPROTO_UDP, uh->check,
                                             ip6_gro_compute_pseudo);

skip:
        NAPI_GRO_CB(skb)->is_ipv6 = 1;
        return udp_gro_receive(head, skb, uh, udp6_lib_lookup_skb);

flush:
        NAPI_GRO_CB(skb)->flush = 1;
        return NULL;
}

static int udp6_gro_complete(struct sk_buff *skb, int nhoff)
{
        const struct ipv6hdr *ipv6h = ipv6_hdr(skb);
        struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);

        if (uh->check) {
                skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL_CSUM;
                uh->check = ~udp_v6_check(skb->len - nhoff, &ipv6h->saddr,
                                          &ipv6h->daddr, 0);
        } else {
                skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL;
        }

        return udp_gro_complete(skb, nhoff, udp6_lib_lookup_skb);
}

static const struct net_offload udpv6_offload = {
        .callbacks = {
                .gso_segment    =       udp6_ufo_fragment,
                .gro_receive    =       udp6_gro_receive,
                .gro_complete   =       udp6_gro_complete,
        },
};

int udpv6_offload_init(void)
{
        return inet6_add_offload(&udpv6_offload, IPPROTO_UDP);
}

int udpv6_offload_exit(void)
{
        return inet6_del_offload(&udpv6_offload, IPPROTO_UDP);
}