// SPDX-License-Identifier: GPL-2.0-or-later
/* SCTP kernel implementation
 * (C) Copyright IBM Corp. 2003, 2004
 *
 * This file is part of the SCTP kernel implementation
 *
 * This file contains the code relating the chunk abstraction.
 *
 * Please send any bug reports or fixes you make to the
 * email address(es):
 *    lksctp developers <linux-sctp@vger.kernel.org>
 *
 * Written or modified by:
 *    Jon Grimm             <jgrimm@us.ibm.com>
 *    Sridhar Samudrala     <sri@us.ibm.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/net.h>
#include <linux/inet.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <net/sctp/sctp.h>
#include <net/sctp/sm.h>

/* This file is mostly in anticipation of future work, but initially
 * populate with fragment tracking for an outbound message.
 */

/* Initialize datamsg from memory. */
static void sctp_datamsg_init(struct sctp_datamsg *msg)
{
        refcount_set(&msg->refcnt, 1);
        msg->send_failed = 0;
        msg->send_error = 0;
        msg->can_delay = 1;
        msg->abandoned = 0;
        msg->expires_at = 0;
        INIT_LIST_HEAD(&msg->chunks);
}

/* Allocate and initialize datamsg. */
static struct sctp_datamsg *sctp_datamsg_new(gfp_t gfp)
{
        struct sctp_datamsg *msg;
        msg = kmalloc_obj(struct sctp_datamsg, gfp);
        if (msg) {
                sctp_datamsg_init(msg);
                SCTP_DBG_OBJCNT_INC(datamsg);
        }
        return msg;
}

void sctp_datamsg_free(struct sctp_datamsg *msg)
{
        struct sctp_chunk *chunk;

        /* This doesn't have to be a _safe vairant because
         * sctp_chunk_free() only drops the refs.
         */
        list_for_each_entry(chunk, &msg->chunks, frag_list)
                sctp_chunk_free(chunk);

        sctp_datamsg_put(msg);
}

/* Final destructruction of datamsg memory. */
static void sctp_datamsg_destroy(struct sctp_datamsg *msg)
{
        struct sctp_association *asoc = NULL;
        struct list_head *pos, *temp;
        struct sctp_chunk *chunk;
        struct sctp_ulpevent *ev;
        int error, sent;

        /* Release all references. */
        list_for_each_safe(pos, temp, &msg->chunks) {
                list_del_init(pos);
                chunk = list_entry(pos, struct sctp_chunk, frag_list);

                if (!msg->send_failed) {
                        sctp_chunk_put(chunk);
                        continue;
                }

                asoc = chunk->asoc;
                error = msg->send_error ?: asoc->outqueue.error;
                sent = chunk->has_tsn ? SCTP_DATA_SENT : SCTP_DATA_UNSENT;

                if (sctp_ulpevent_type_enabled(asoc->subscribe,
                                               SCTP_SEND_FAILED)) {
                        ev = sctp_ulpevent_make_send_failed(asoc, chunk, sent,
                                                            error, GFP_ATOMIC);
                        if (ev)
                                asoc->stream.si->enqueue_event(&asoc->ulpq, ev);
                }

                if (sctp_ulpevent_type_enabled(asoc->subscribe,
                                               SCTP_SEND_FAILED_EVENT)) {
                        ev = sctp_ulpevent_make_send_failed_event(asoc, chunk,
                                                                  sent, error,
                                                                  GFP_ATOMIC);
                        if (ev)
                                asoc->stream.si->enqueue_event(&asoc->ulpq, ev);
                }

                sctp_chunk_put(chunk);
        }

        SCTP_DBG_OBJCNT_DEC(datamsg);
        kfree(msg);
}

/* Hold a reference. */
static void sctp_datamsg_hold(struct sctp_datamsg *msg)
{
        refcount_inc(&msg->refcnt);
}

/* Release a reference. */
void sctp_datamsg_put(struct sctp_datamsg *msg)
{
        if (refcount_dec_and_test(&msg->refcnt))
                sctp_datamsg_destroy(msg);
}

/* Assign a chunk to this datamsg. */
static void sctp_datamsg_assign(struct sctp_datamsg *msg, struct sctp_chunk *chunk)
{
        sctp_datamsg_hold(msg);
        chunk->msg = msg;
}


/* A data chunk can have a maximum payload of (2^16 - 20).  Break
 * down any such message into smaller chunks.  Opportunistically, fragment
 * the chunks down to the current MTU constraints.  We may get refragmented
 * later if the PMTU changes, but it is _much better_ to fragment immediately
 * with a reasonable guess than always doing our fragmentation on the
 * soft-interrupt.
 */
struct sctp_datamsg *sctp_datamsg_from_user(struct sctp_association *asoc,
                                            struct sctp_sndrcvinfo *sinfo,
                                            struct iov_iter *from)
{
        size_t len, first_len, max_data, remaining;
        size_t msg_len = iov_iter_count(from);
        struct sctp_shared_key *shkey = NULL;
        struct list_head *pos, *temp;
        struct sctp_chunk *chunk;
        struct sctp_datamsg *msg;
        int err;

        msg = sctp_datamsg_new(GFP_KERNEL);
        if (!msg)
                return ERR_PTR(-ENOMEM);

        /* Note: Calculate this outside of the loop, so that all fragments
         * have the same expiration.
         */
        if (asoc->peer.prsctp_capable && sinfo->sinfo_timetolive &&
            (SCTP_PR_TTL_ENABLED(sinfo->sinfo_flags) ||
             !SCTP_PR_POLICY(sinfo->sinfo_flags)))
                msg->expires_at = jiffies +
                                  msecs_to_jiffies(sinfo->sinfo_timetolive);

        /* This is the biggest possible DATA chunk that can fit into
         * the packet
         */
        max_data = asoc->frag_point;
        if (unlikely(!max_data)) {
                max_data = sctp_min_frag_point(sctp_sk(asoc->base.sk),
                                               sctp_datachk_len(&asoc->stream));
                pr_warn_ratelimited("%s: asoc:%p frag_point is zero, forcing max_data to default minimum (%zu)",
                                    __func__, asoc, max_data);
        }

        /* If the peer requested that we authenticate DATA chunks
         * we need to account for bundling of the AUTH chunks along with
         * DATA.
         */
        if (sctp_auth_send_cid(SCTP_CID_DATA, asoc)) {
                const struct sctp_hmac *hmac_desc =
                        sctp_auth_asoc_get_hmac(asoc);

                if (hmac_desc)
                        max_data -= SCTP_PAD4(sizeof(struct sctp_auth_chunk) +
                                              hmac_desc->hmac_len);

                if (sinfo->sinfo_tsn &&
                    sinfo->sinfo_ssn != asoc->active_key_id) {
                        shkey = sctp_auth_get_shkey(asoc, sinfo->sinfo_ssn);
                        if (!shkey) {
                                err = -EINVAL;
                                goto errout;
                        }
                } else {
                        shkey = asoc->shkey;
                }
        }

        /* Set first_len and then account for possible bundles on first frag */
        first_len = max_data;

        /* Check to see if we have a pending SACK and try to let it be bundled
         * with this message.  Do this if we don't have any data queued already.
         * To check that, look at out_qlen and retransmit list.
         * NOTE: we will not reduce to account for SACK, if the message would
         * not have been fragmented.
         */
        if (timer_pending(&asoc->timers[SCTP_EVENT_TIMEOUT_SACK]) &&
            asoc->outqueue.out_qlen == 0 &&
            list_empty(&asoc->outqueue.retransmit) &&
            msg_len > max_data)
                first_len -= SCTP_PAD4(sizeof(struct sctp_sack_chunk));

        /* Encourage Cookie-ECHO bundling. */
        if (asoc->state < SCTP_STATE_COOKIE_ECHOED)
                first_len -= SCTP_ARBITRARY_COOKIE_ECHO_LEN;

        /* Account for a different sized first fragment */
        if (msg_len >= first_len) {
                msg->can_delay = 0;
                if (msg_len > first_len)
                        SCTP_INC_STATS(asoc->base.net,
                                       SCTP_MIB_FRAGUSRMSGS);
        } else {
                /* Which may be the only one... */
                first_len = msg_len;
        }

        /* Create chunks for all DATA chunks. */
        for (remaining = msg_len; remaining; remaining -= len) {
                u8 frag = SCTP_DATA_MIDDLE_FRAG;

                if (remaining == msg_len) {
                        /* First frag, which may also be the last */
                        frag |= SCTP_DATA_FIRST_FRAG;
                        len = first_len;
                } else {
                        /* Middle frags */
                        len = max_data;
                }

                if (len >= remaining) {
                        /* Last frag, which may also be the first */
                        len = remaining;
                        frag |= SCTP_DATA_LAST_FRAG;

                        /* The application requests to set the I-bit of the
                         * last DATA chunk of a user message when providing
                         * the user message to the SCTP implementation.
                         */
                        if ((sinfo->sinfo_flags & SCTP_EOF) ||
                            (sinfo->sinfo_flags & SCTP_SACK_IMMEDIATELY))
                                frag |= SCTP_DATA_SACK_IMM;
                }

                chunk = asoc->stream.si->make_datafrag(asoc, sinfo, len, frag,
                                                       GFP_KERNEL);
                if (!chunk) {
                        err = -ENOMEM;
                        goto errout;
                }

                err = sctp_user_addto_chunk(chunk, len, from);
                if (err < 0)
                        goto errout_chunk_free;

                chunk->shkey = shkey;

                /* Put the chunk->skb back into the form expected by send.  */
                __skb_pull(chunk->skb, (__u8 *)chunk->chunk_hdr -
                                       chunk->skb->data);

                sctp_datamsg_assign(msg, chunk);
                list_add_tail(&chunk->frag_list, &msg->chunks);
        }

        return msg;

errout_chunk_free:
        sctp_chunk_free(chunk);

errout:
        list_for_each_safe(pos, temp, &msg->chunks) {
                list_del_init(pos);
                chunk = list_entry(pos, struct sctp_chunk, frag_list);
                sctp_chunk_free(chunk);
        }
        sctp_datamsg_put(msg);

        return ERR_PTR(err);
}

/* Check whether this message has expired. */
int sctp_chunk_abandoned(struct sctp_chunk *chunk)
{
        if (!chunk->asoc->peer.prsctp_capable)
                return 0;

        if (chunk->msg->abandoned)
                return 1;

        if (!chunk->has_tsn &&
            !(chunk->chunk_hdr->flags & SCTP_DATA_FIRST_FRAG))
                return 0;

        if (SCTP_PR_TTL_ENABLED(chunk->sinfo.sinfo_flags) &&
            time_after(jiffies, chunk->msg->expires_at)) {
                struct sctp_stream_out *streamout =
                        SCTP_SO(&chunk->asoc->stream,
                                chunk->sinfo.sinfo_stream);

                if (chunk->sent_count) {
                        chunk->asoc->abandoned_sent[SCTP_PR_INDEX(TTL)]++;
                        streamout->ext->abandoned_sent[SCTP_PR_INDEX(TTL)]++;
                } else {
                        chunk->asoc->abandoned_unsent[SCTP_PR_INDEX(TTL)]++;
                        streamout->ext->abandoned_unsent[SCTP_PR_INDEX(TTL)]++;
                }
                chunk->msg->abandoned = 1;
                return 1;
        } else if (SCTP_PR_RTX_ENABLED(chunk->sinfo.sinfo_flags) &&
                   chunk->sent_count > chunk->sinfo.sinfo_timetolive) {
                struct sctp_stream_out *streamout =
                        SCTP_SO(&chunk->asoc->stream,
                                chunk->sinfo.sinfo_stream);

                chunk->asoc->abandoned_sent[SCTP_PR_INDEX(RTX)]++;
                streamout->ext->abandoned_sent[SCTP_PR_INDEX(RTX)]++;
                chunk->msg->abandoned = 1;
                return 1;
        } else if (!SCTP_PR_POLICY(chunk->sinfo.sinfo_flags) &&
                   chunk->msg->expires_at &&
                   time_after(jiffies, chunk->msg->expires_at)) {
                chunk->msg->abandoned = 1;
                return 1;
        }
        /* PRIO policy is processed by sendmsg, not here */

        return 0;
}

/* This chunk (and consequently entire message) has failed in its sending. */
void sctp_chunk_fail(struct sctp_chunk *chunk, int error)
{
        chunk->msg->send_failed = 1;
        chunk->msg->send_error = error;
}