// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * sctp_offload - GRO/GSO Offloading for SCTP
 *
 * Copyright (C) 2015, Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/kprobes.h>
#include <linux/socket.h>
#include <linux/sctp.h>
#include <linux/proc_fs.h>
#include <linux/vmalloc.h>
#include <linux/module.h>
#include <linux/kfifo.h>
#include <linux/time.h>
#include <net/net_namespace.h>

#include <linux/skbuff.h>
#include <net/sctp/sctp.h>
#include <net/sctp/checksum.h>
#include <net/protocol.h>
#include <net/gso.h>

static __le32 sctp_gso_make_checksum(struct sk_buff *skb)
{
        skb->ip_summed = CHECKSUM_NONE;
        skb->csum_not_inet = 0;
        /* csum and csum_start in GSO CB may be needed to do the UDP
         * checksum when it's a UDP tunneling packet.
         */
        SKB_GSO_CB(skb)->csum = (__force __wsum)~0;
        SKB_GSO_CB(skb)->csum_start = skb_headroom(skb) + skb->len;
        return sctp_compute_cksum(skb, skb_transport_offset(skb));
}

static struct sk_buff *sctp_gso_segment(struct sk_buff *skb,
                                        netdev_features_t features)
{
        struct sk_buff *segs = ERR_PTR(-EINVAL);
        struct sctphdr *sh;

        if (!skb_is_gso_sctp(skb))
                goto out;

        sh = sctp_hdr(skb);
        if (!pskb_may_pull(skb, sizeof(*sh)))
                goto out;

        __skb_pull(skb, sizeof(*sh));

        if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
                /* Packet is from an untrusted source, reset gso_segs. */
                struct skb_shared_info *pinfo = skb_shinfo(skb);
                struct sk_buff *frag_iter;

                pinfo->gso_segs = 0;
                if (skb->len != skb->data_len) {
                        /* Means we have chunks in here too */
                        pinfo->gso_segs++;
                }

                skb_walk_frags(skb, frag_iter)
                        pinfo->gso_segs++;

                segs = NULL;
                goto out;
        }

        segs = skb_segment(skb, (features | NETIF_F_HW_CSUM) & ~NETIF_F_SG);
        if (IS_ERR(segs))
                goto out;

        /* All that is left is update SCTP CRC if necessary */
        if (!(features & NETIF_F_SCTP_CRC)) {
                for (skb = segs; skb; skb = skb->next) {
                        if (skb->ip_summed == CHECKSUM_PARTIAL) {
                                sh = sctp_hdr(skb);
                                sh->checksum = sctp_gso_make_checksum(skb);
                        }
                }
        }

out:
        return segs;
}

static const struct net_offload sctp_offload = {
        .callbacks = {
                .gso_segment = sctp_gso_segment,
        },
};

static const struct net_offload sctp6_offload = {
        .callbacks = {
                .gso_segment = sctp_gso_segment,
        },
};

int __init sctp_offload_init(void)
{
        int ret;

        ret = inet_add_offload(&sctp_offload, IPPROTO_SCTP);
        if (ret)
                goto out;

        ret = inet6_add_offload(&sctp6_offload, IPPROTO_SCTP);
        if (ret)
                goto ipv4;

        return ret;

ipv4:
        inet_del_offload(&sctp_offload, IPPROTO_SCTP);
out:
        return ret;
}