// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      IPV6 GSO/GRO offload support
 *      Linux INET6 implementation
 */

#include <linux/kernel.h>
#include <linux/socket.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/printk.h>

#include <net/protocol.h>
#include <net/ipv6.h>
#include <net/inet_common.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <net/gro.h>
#include <net/gso.h>

#include "ip6_offload.h"
#include "tcpv6_offload.c"

static int ipv6_gro_pull_exthdrs(struct sk_buff *skb, int off, int proto)
{
        const struct net_offload *ops = NULL;
        struct ipv6_opt_hdr *opth;

        for (;;) {
                int len;

                ops = rcu_dereference(inet6_offloads[proto]);

                if (unlikely(!ops))
                        break;

                if (!(ops->flags & INET6_PROTO_GSO_EXTHDR))
                        break;

                opth = skb_gro_header(skb, off + sizeof(*opth), off);
                if (unlikely(!opth))
                        break;

                len = ipv6_optlen(opth);

                opth = skb_gro_header(skb, off + len, off);
                if (unlikely(!opth))
                        break;
                proto = opth->nexthdr;

                off += len;
        }

        skb_gro_pull(skb, off - skb_gro_receive_network_offset(skb));
        return proto;
}

static int ipv6_gso_pull_exthdrs(struct sk_buff *skb, int proto)
{
        const struct net_offload *ops = NULL;

        for (;;) {
                struct ipv6_opt_hdr *opth;
                int len;

                ops = rcu_dereference(inet6_offloads[proto]);

                if (unlikely(!ops))
                        break;

                if (!(ops->flags & INET6_PROTO_GSO_EXTHDR))
                        break;

                if (unlikely(!pskb_may_pull(skb, 8)))
                        break;

                opth = (void *)skb->data;
                len = ipv6_optlen(opth);

                if (unlikely(!pskb_may_pull(skb, len)))
                        break;

                opth = (void *)skb->data;
                proto = opth->nexthdr;
                __skb_pull(skb, len);
        }

        return proto;
}

static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
        netdev_features_t features)
{
        struct sk_buff *segs = ERR_PTR(-EINVAL);
        struct ipv6hdr *ipv6h;
        const struct net_offload *ops;
        int proto;
        struct frag_hdr *fptr;
        unsigned int payload_len;
        u8 *prevhdr;
        int offset = 0;
        bool encap, udpfrag;
        int nhoff;
        bool gso_partial;

        skb_reset_network_header(skb);
        nhoff = skb_network_header(skb) - skb_mac_header(skb);
        if (unlikely(!pskb_may_pull(skb, sizeof(*ipv6h))))
                goto out;

        encap = SKB_GSO_CB(skb)->encap_level > 0;
        if (encap)
                features &= skb->dev->hw_enc_features;
        SKB_GSO_CB(skb)->encap_level += sizeof(*ipv6h);

        ipv6h = ipv6_hdr(skb);
        __skb_pull(skb, sizeof(*ipv6h));
        segs = ERR_PTR(-EPROTONOSUPPORT);

        proto = ipv6_gso_pull_exthdrs(skb, ipv6h->nexthdr);

        if (skb->encapsulation &&
            skb_shinfo(skb)->gso_type & (SKB_GSO_IPXIP4 | SKB_GSO_IPXIP6))
                udpfrag = proto == IPPROTO_UDP && encap &&
                          (skb_shinfo(skb)->gso_type & SKB_GSO_UDP);
        else
                udpfrag = proto == IPPROTO_UDP && !skb->encapsulation &&
                          (skb_shinfo(skb)->gso_type & SKB_GSO_UDP);

        ops = rcu_dereference(inet6_offloads[proto]);
        if (likely(ops && ops->callbacks.gso_segment)) {
                if (!skb_reset_transport_header_careful(skb))
                        goto out;

                segs = ops->callbacks.gso_segment(skb, features);
                if (!segs)
                        skb->network_header = skb_mac_header(skb) + nhoff - skb->head;
        }

        if (IS_ERR_OR_NULL(segs))
                goto out;

        gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);

        for (skb = segs; skb; skb = skb->next) {
                ipv6h = (struct ipv6hdr *)(skb_mac_header(skb) + nhoff);
                if (gso_partial && skb_is_gso(skb))
                        payload_len = skb_shinfo(skb)->gso_size +
                                      SKB_GSO_CB(skb)->data_offset +
                                      skb->head - (unsigned char *)(ipv6h + 1);
                else
                        payload_len = skb->len - nhoff - sizeof(*ipv6h);
                ipv6h->payload_len = htons(payload_len);
                skb->network_header = (u8 *)ipv6h - skb->head;
                skb_reset_mac_len(skb);

                if (udpfrag) {
                        int err = ip6_find_1stfragopt(skb, &prevhdr);
                        if (err < 0) {
                                kfree_skb_list(segs);
                                return ERR_PTR(err);
                        }
                        fptr = (struct frag_hdr *)((u8 *)ipv6h + err);
                        fptr->frag_off = htons(offset);
                        if (skb->next)
                                fptr->frag_off |= htons(IP6_MF);
                        offset += (ntohs(ipv6h->payload_len) -
                                   sizeof(struct frag_hdr));
                }
                if (encap)
                        skb_reset_inner_headers(skb);
        }

out:
        return segs;
}

/* Return the total length of all the extension hdrs, following the same
 * logic in ipv6_gso_pull_exthdrs() when parsing ext-hdrs.
 */
static int ipv6_exthdrs_len(struct ipv6hdr *iph,
                            const struct net_offload **opps)
{
        struct ipv6_opt_hdr *opth = (void *)iph;
        int len = 0, proto, optlen = sizeof(*iph);

        proto = iph->nexthdr;
        for (;;) {
                *opps = rcu_dereference(inet6_offloads[proto]);
                if (unlikely(!(*opps)))
                        break;
                if (!((*opps)->flags & INET6_PROTO_GSO_EXTHDR))
                        break;

                opth = (void *)opth + optlen;
                optlen = ipv6_optlen(opth);
                len += optlen;
                proto = opth->nexthdr;
        }
        return len;
}

INDIRECT_CALLABLE_SCOPE struct sk_buff *ipv6_gro_receive(struct list_head *head,
                                                         struct sk_buff *skb)
{
        const struct net_offload *ops;
        struct sk_buff *pp = NULL;
        struct sk_buff *p;
        struct ipv6hdr *iph;
        unsigned int nlen;
        unsigned int hlen;
        unsigned int off;
        u16 flush = 1;
        int proto;

        off = skb_gro_offset(skb);
        hlen = off + sizeof(*iph);
        iph = skb_gro_header(skb, hlen, off);
        if (unlikely(!iph))
                goto out;

        NAPI_GRO_CB(skb)->network_offsets[NAPI_GRO_CB(skb)->encap_mark] = off;

        flush += ntohs(iph->payload_len) != skb->len - hlen;

        proto = iph->nexthdr;
        ops = rcu_dereference(inet6_offloads[proto]);
        if (!ops || !ops->callbacks.gro_receive) {
                proto = ipv6_gro_pull_exthdrs(skb, hlen, proto);

                ops = rcu_dereference(inet6_offloads[proto]);
                if (!ops || !ops->callbacks.gro_receive)
                        goto out;

                iph = skb_gro_network_header(skb);
        } else {
                skb_gro_pull(skb, sizeof(*iph));
        }

        skb_set_transport_header(skb, skb_gro_offset(skb));

        NAPI_GRO_CB(skb)->proto = proto;

        flush--;
        nlen = skb_gro_offset(skb) - off;

        list_for_each_entry(p, head, list) {
                const struct ipv6hdr *iph2;
                __be32 first_word; /* <Version:4><Traffic_Class:8><Flow_Label:20> */

                if (!NAPI_GRO_CB(p)->same_flow)
                        continue;

                iph2 = (struct ipv6hdr *)(p->data + off);
                first_word = *(__be32 *)iph ^ *(__be32 *)iph2;

                /* All fields must match except length and Traffic Class.
                 * XXX skbs on the gro_list have all been parsed and pulled
                 * already so we don't need to compare nlen
                 * (nlen != (sizeof(*iph2) + ipv6_exthdrs_len(iph2, &ops)))
                 * memcmp() alone below is sufficient, right?
                 */
                 if ((first_word & htonl(0xF00FFFFF)) ||
                     !ipv6_addr_equal(&iph->saddr, &iph2->saddr) ||
                     !ipv6_addr_equal(&iph->daddr, &iph2->daddr) ||
                     iph->nexthdr != iph2->nexthdr) {
not_same_flow:
                        NAPI_GRO_CB(p)->same_flow = 0;
                        continue;
                }
                if (unlikely(nlen > sizeof(struct ipv6hdr))) {
                        if (memcmp(iph + 1, iph2 + 1,
                                   nlen - sizeof(struct ipv6hdr)))
                                goto not_same_flow;
                }
        }

        NAPI_GRO_CB(skb)->flush |= flush;

        skb_gro_postpull_rcsum(skb, iph, nlen);

        if (unlikely(gro_recursion_inc_test(skb))) {
                flush = 1;
                goto out;
        }

        if (likely(proto == IPPROTO_TCP))
                pp = tcp6_gro_receive(head, skb);
#if IS_BUILTIN(CONFIG_IPV6)
        else if (likely(proto == IPPROTO_UDP))
                pp = udp6_gro_receive(head, skb);
#endif
        else
                pp = ops->callbacks.gro_receive(head, skb);
out:
        skb_gro_flush_final(skb, pp, flush);

        return pp;
}

static struct sk_buff *sit_ip6ip6_gro_receive(struct list_head *head,
                                              struct sk_buff *skb)
{
        /* Common GRO receive for SIT and IP6IP6 */

        if (NAPI_GRO_CB(skb)->encap_mark) {
                NAPI_GRO_CB(skb)->flush = 1;
                return NULL;
        }

        NAPI_GRO_CB(skb)->encap_mark = 1;

        return ipv6_gro_receive(head, skb);
}

static struct sk_buff *ip4ip6_gro_receive(struct list_head *head,
                                          struct sk_buff *skb)
{
        /* Common GRO receive for SIT and IP6IP6 */

        if (NAPI_GRO_CB(skb)->encap_mark) {
                NAPI_GRO_CB(skb)->flush = 1;
                return NULL;
        }

        NAPI_GRO_CB(skb)->encap_mark = 1;

        return inet_gro_receive(head, skb);
}

INDIRECT_CALLABLE_SCOPE int ipv6_gro_complete(struct sk_buff *skb, int nhoff)
{
        const struct net_offload *ops;
        struct ipv6hdr *iph;
        int err = -ENOSYS;

        if (skb->encapsulation) {
                skb_set_inner_protocol(skb, cpu_to_be16(ETH_P_IPV6));
                skb_set_inner_network_header(skb, nhoff);
        }

        iph = (struct ipv6hdr *)(skb->data + nhoff);
        ipv6_set_payload_len(iph, skb->len - nhoff - sizeof(*iph));

        nhoff += sizeof(*iph) + ipv6_exthdrs_len(iph, &ops);

        if (likely(ops == &net_hotdata.tcpv6_offload))
                return tcp6_gro_complete(skb, nhoff);
#if IS_BUILTIN(CONFIG_IPV6)
        if (ops == &net_hotdata.udpv6_offload)
                return udp6_gro_complete(skb, nhoff);
#endif

        if (WARN_ON(!ops || !ops->callbacks.gro_complete))
                goto out;

        err = ops->callbacks.gro_complete(skb, nhoff);

out:
        return err;
}

static int sit_gro_complete(struct sk_buff *skb, int nhoff)
{
        skb->encapsulation = 1;
        skb_shinfo(skb)->gso_type |= SKB_GSO_IPXIP4;
        return ipv6_gro_complete(skb, nhoff);
}

static int ip6ip6_gro_complete(struct sk_buff *skb, int nhoff)
{
        skb->encapsulation = 1;
        skb_shinfo(skb)->gso_type |= SKB_GSO_IPXIP6;
        return ipv6_gro_complete(skb, nhoff);
}

static int ip4ip6_gro_complete(struct sk_buff *skb, int nhoff)
{
        skb->encapsulation = 1;
        skb_shinfo(skb)->gso_type |= SKB_GSO_IPXIP6;
        return inet_gro_complete(skb, nhoff);
}


static struct sk_buff *sit_gso_segment(struct sk_buff *skb,
                                       netdev_features_t features)
{
        if (!(skb_shinfo(skb)->gso_type & SKB_GSO_IPXIP4))
                return ERR_PTR(-EINVAL);

        return ipv6_gso_segment(skb, features);
}

static struct sk_buff *ip4ip6_gso_segment(struct sk_buff *skb,
                                          netdev_features_t features)
{
        if (!(skb_shinfo(skb)->gso_type & SKB_GSO_IPXIP6))
                return ERR_PTR(-EINVAL);

        return inet_gso_segment(skb, features);
}

static struct sk_buff *ip6ip6_gso_segment(struct sk_buff *skb,
                                          netdev_features_t features)
{
        if (!(skb_shinfo(skb)->gso_type & SKB_GSO_IPXIP6))
                return ERR_PTR(-EINVAL);

        return ipv6_gso_segment(skb, features);
}

static const struct net_offload sit_offload = {
        .callbacks = {
                .gso_segment    = sit_gso_segment,
                .gro_receive    = sit_ip6ip6_gro_receive,
                .gro_complete   = sit_gro_complete,
        },
};

static const struct net_offload ip4ip6_offload = {
        .callbacks = {
                .gso_segment    = ip4ip6_gso_segment,
                .gro_receive    = ip4ip6_gro_receive,
                .gro_complete   = ip4ip6_gro_complete,
        },
};

static const struct net_offload ip6ip6_offload = {
        .callbacks = {
                .gso_segment    = ip6ip6_gso_segment,
                .gro_receive    = sit_ip6ip6_gro_receive,
                .gro_complete   = ip6ip6_gro_complete,
        },
};
static int __init ipv6_offload_init(void)
{

        if (tcpv6_offload_init() < 0)
                pr_crit("%s: Cannot add TCP protocol offload\n", __func__);
        if (ipv6_exthdrs_offload_init() < 0)
                pr_crit("%s: Cannot add EXTHDRS protocol offload\n", __func__);

        net_hotdata.ipv6_packet_offload = (struct packet_offload) {
                .type = cpu_to_be16(ETH_P_IPV6),
                .callbacks = {
                        .gso_segment = ipv6_gso_segment,
                        .gro_receive = ipv6_gro_receive,
                        .gro_complete = ipv6_gro_complete,
                },
        };
        dev_add_offload(&net_hotdata.ipv6_packet_offload);

        inet_add_offload(&sit_offload, IPPROTO_IPV6);
        inet6_add_offload(&ip6ip6_offload, IPPROTO_IPV6);
        inet6_add_offload(&ip4ip6_offload, IPPROTO_IPIP);

        return 0;
}

fs_initcall(ipv6_offload_init);