writeback: split writeback_inodes_wb

[linux-2.6/next.git] / net / sctp / ulpevent.c

/* SCTP kernel implementation
 * (C) Copyright IBM Corp. 2001, 2004
 * Copyright (c) 1999-2000 Cisco, Inc.
 * Copyright (c) 1999-2001 Motorola, Inc.
 * Copyright (c) 2001 Intel Corp.
 * Copyright (c) 2001 Nokia, Inc.
 * Copyright (c) 2001 La Monte H.P. Yarroll
 *
 * These functions manipulate an sctp event.   The struct ulpevent is used
 * to carry notifications and data to the ULP (sockets).
 *
 * This SCTP implementation 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, or (at your option)
 * any later version.
 *
 * This SCTP implementation is distributed in the hope that it
 * will be useful, but WITHOUT ANY WARRANTY; without even the implied
 *                 ************************
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with GNU CC; see the file COPYING.  If not, write to
 * the Free Software Foundation, 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * Please send any bug reports or fixes you make to the
 * email address(es):
 *    lksctp developers <lksctp-developers@lists.sourceforge.net>
 *
 * Or submit a bug report through the following website:
 *    http://www.sf.net/projects/lksctp
 *
 * Written or modified by:
 *    Jon Grimm             <jgrimm@us.ibm.com>
 *    La Monte H.P. Yarroll <piggy@acm.org>
 *    Ardelle Fan           <ardelle.fan@intel.com>
 *    Sridhar Samudrala     <sri@us.ibm.com>
 *
 * Any bugs reported given to us we will try to fix... any fixes shared will
 * be incorporated into the next SCTP release.
 */

#include <linux/slab.h>
#include <linux/types.h>
#include <linux/skbuff.h>
#include <net/sctp/structs.h>
#include <net/sctp/sctp.h>
#include <net/sctp/sm.h>

static void sctp_ulpevent_receive_data(struct sctp_ulpevent *event,
                                       struct sctp_association *asoc);
static void sctp_ulpevent_release_data(struct sctp_ulpevent *event);
static void sctp_ulpevent_release_frag_data(struct sctp_ulpevent *event);


/* Initialize an ULP event from an given skb.  */
SCTP_STATIC void sctp_ulpevent_init(struct sctp_ulpevent *event,
                                    int msg_flags,
                                    unsigned int len)
{
        memset(event, 0, sizeof(struct sctp_ulpevent));
        event->msg_flags = msg_flags;
        event->rmem_len = len;
}

/* Create a new sctp_ulpevent.  */
SCTP_STATIC struct sctp_ulpevent *sctp_ulpevent_new(int size, int msg_flags,
                                                    gfp_t gfp)
{
        struct sctp_ulpevent *event;
        struct sk_buff *skb;

        skb = alloc_skb(size, gfp);
        if (!skb)
                goto fail;

        event = sctp_skb2event(skb);
        sctp_ulpevent_init(event, msg_flags, skb->truesize);

        return event;

fail:
        return NULL;
}

/* Is this a MSG_NOTIFICATION?  */
int sctp_ulpevent_is_notification(const struct sctp_ulpevent *event)
{
        return MSG_NOTIFICATION == (event->msg_flags & MSG_NOTIFICATION);
}

/* Hold the association in case the msg_name needs read out of
 * the association.
 */
static inline void sctp_ulpevent_set_owner(struct sctp_ulpevent *event,
                                           const struct sctp_association *asoc)
{
        struct sk_buff *skb;

        /* Cast away the const, as we are just wanting to
         * bump the reference count.
         */
        sctp_association_hold((struct sctp_association *)asoc);
        skb = sctp_event2skb(event);
        event->asoc = (struct sctp_association *)asoc;
        atomic_add(event->rmem_len, &event->asoc->rmem_alloc);
        sctp_skb_set_owner_r(skb, asoc->base.sk);
}

/* A simple destructor to give up the reference to the association. */
static inline void sctp_ulpevent_release_owner(struct sctp_ulpevent *event)
{
        struct sctp_association *asoc = event->asoc;

        atomic_sub(event->rmem_len, &asoc->rmem_alloc);
        sctp_association_put(asoc);
}

/* Create and initialize an SCTP_ASSOC_CHANGE event.
 *
 * 5.3.1.1 SCTP_ASSOC_CHANGE
 *
 * Communication notifications inform the ULP that an SCTP association
 * has either begun or ended. The identifier for a new association is
 * provided by this notification.
 *
 * Note: There is no field checking here.  If a field is unused it will be
 * zero'd out.
 */
struct sctp_ulpevent  *sctp_ulpevent_make_assoc_change(
        const struct sctp_association *asoc,
        __u16 flags, __u16 state, __u16 error, __u16 outbound,
        __u16 inbound, struct sctp_chunk *chunk, gfp_t gfp)
{
        struct sctp_ulpevent *event;
        struct sctp_assoc_change *sac;
        struct sk_buff *skb;

        /* If the lower layer passed in the chunk, it will be
         * an ABORT, so we need to include it in the sac_info.
         */
        if (chunk) {
                /* Copy the chunk data to a new skb and reserve enough
                 * head room to use as notification.
                 */
                skb = skb_copy_expand(chunk->skb,
                                      sizeof(struct sctp_assoc_change), 0, gfp);

                if (!skb)
                        goto fail;

                /* Embed the event fields inside the cloned skb.  */
                event = sctp_skb2event(skb);
                sctp_ulpevent_init(event, MSG_NOTIFICATION, skb->truesize);

                /* Include the notification structure */
                sac = (struct sctp_assoc_change *)
                        skb_push(skb, sizeof(struct sctp_assoc_change));

                /* Trim the buffer to the right length.  */
                skb_trim(skb, sizeof(struct sctp_assoc_change) +
                         ntohs(chunk->chunk_hdr->length) -
                         sizeof(sctp_chunkhdr_t));
        } else {
                event = sctp_ulpevent_new(sizeof(struct sctp_assoc_change),
                                  MSG_NOTIFICATION, gfp);
                if (!event)
                        goto fail;

                skb = sctp_event2skb(event);
                sac = (struct sctp_assoc_change *) skb_put(skb,
                                        sizeof(struct sctp_assoc_change));
        }

        /* Socket Extensions for SCTP
         * 5.3.1.1 SCTP_ASSOC_CHANGE
         *
         * sac_type:
         * It should be SCTP_ASSOC_CHANGE.
         */
        sac->sac_type = SCTP_ASSOC_CHANGE;

        /* Socket Extensions for SCTP
         * 5.3.1.1 SCTP_ASSOC_CHANGE
         *
         * sac_state: 32 bits (signed integer)
         * This field holds one of a number of values that communicate the
         * event that happened to the association.
         */
        sac->sac_state = state;

        /* Socket Extensions for SCTP
         * 5.3.1.1 SCTP_ASSOC_CHANGE
         *
         * sac_flags: 16 bits (unsigned integer)
         * Currently unused.
         */
        sac->sac_flags = 0;

        /* Socket Extensions for SCTP
         * 5.3.1.1 SCTP_ASSOC_CHANGE
         *
         * sac_length: sizeof (__u32)
         * This field is the total length of the notification data, including
         * the notification header.
         */
        sac->sac_length = skb->len;

        /* Socket Extensions for SCTP
         * 5.3.1.1 SCTP_ASSOC_CHANGE
         *
         * sac_error:  32 bits (signed integer)
         *
         * If the state was reached due to a error condition (e.g.
         * COMMUNICATION_LOST) any relevant error information is available in
         * this field. This corresponds to the protocol error codes defined in
         * [SCTP].
         */
        sac->sac_error = error;

        /* Socket Extensions for SCTP
         * 5.3.1.1 SCTP_ASSOC_CHANGE
         *
         * sac_outbound_streams:  16 bits (unsigned integer)
         * sac_inbound_streams:  16 bits (unsigned integer)
         *
         * The maximum number of streams allowed in each direction are
         * available in sac_outbound_streams and sac_inbound streams.
         */
        sac->sac_outbound_streams = outbound;
        sac->sac_inbound_streams = inbound;

        /* Socket Extensions for SCTP
         * 5.3.1.1 SCTP_ASSOC_CHANGE
         *
         * sac_assoc_id: sizeof (sctp_assoc_t)
         *
         * The association id field, holds the identifier for the association.
         * All notifications for a given association have the same association
         * identifier.  For TCP style socket, this field is ignored.
         */
        sctp_ulpevent_set_owner(event, asoc);
        sac->sac_assoc_id = sctp_assoc2id(asoc);

        return event;

fail:
        return NULL;
}

/* Create and initialize an SCTP_PEER_ADDR_CHANGE event.
 *
 * Socket Extensions for SCTP - draft-01
 * 5.3.1.2 SCTP_PEER_ADDR_CHANGE
 *
 * When a destination address on a multi-homed peer encounters a change
 * an interface details event is sent.
 */
struct sctp_ulpevent *sctp_ulpevent_make_peer_addr_change(
        const struct sctp_association *asoc,
        const struct sockaddr_storage *aaddr,
        int flags, int state, int error, gfp_t gfp)
{
        struct sctp_ulpevent *event;
        struct sctp_paddr_change  *spc;
        struct sk_buff *skb;

        event = sctp_ulpevent_new(sizeof(struct sctp_paddr_change),
                                  MSG_NOTIFICATION, gfp);
        if (!event)
                goto fail;

        skb = sctp_event2skb(event);
        spc = (struct sctp_paddr_change *)
                skb_put(skb, sizeof(struct sctp_paddr_change));

        /* Sockets API Extensions for SCTP
         * Section 5.3.1.2 SCTP_PEER_ADDR_CHANGE
         *
         * spc_type:
         *
         *    It should be SCTP_PEER_ADDR_CHANGE.
         */
        spc->spc_type = SCTP_PEER_ADDR_CHANGE;

        /* Sockets API Extensions for SCTP
         * Section 5.3.1.2 SCTP_PEER_ADDR_CHANGE
         *
         * spc_length: sizeof (__u32)
         *
         * This field is the total length of the notification data, including
         * the notification header.
         */
        spc->spc_length = sizeof(struct sctp_paddr_change);

        /* Sockets API Extensions for SCTP
         * Section 5.3.1.2 SCTP_PEER_ADDR_CHANGE
         *
         * spc_flags: 16 bits (unsigned integer)
         * Currently unused.
         */
        spc->spc_flags = 0;

        /* Sockets API Extensions for SCTP
         * Section 5.3.1.2 SCTP_PEER_ADDR_CHANGE
         *
         * spc_state:  32 bits (signed integer)
         *
         * This field holds one of a number of values that communicate the
         * event that happened to the address.
         */
        spc->spc_state = state;

        /* Sockets API Extensions for SCTP
         * Section 5.3.1.2 SCTP_PEER_ADDR_CHANGE
         *
         * spc_error:  32 bits (signed integer)
         *
         * If the state was reached due to any error condition (e.g.
         * ADDRESS_UNREACHABLE) any relevant error information is available in
         * this field.
         */
        spc->spc_error = error;

        /* Socket Extensions for SCTP
         * 5.3.1.1 SCTP_ASSOC_CHANGE
         *
         * spc_assoc_id: sizeof (sctp_assoc_t)
         *
         * The association id field, holds the identifier for the association.
         * All notifications for a given association have the same association
         * identifier.  For TCP style socket, this field is ignored.
         */
        sctp_ulpevent_set_owner(event, asoc);
        spc->spc_assoc_id = sctp_assoc2id(asoc);

        /* Sockets API Extensions for SCTP
         * Section 5.3.1.2 SCTP_PEER_ADDR_CHANGE
         *
         * spc_aaddr: sizeof (struct sockaddr_storage)
         *
         * The affected address field, holds the remote peer's address that is
         * encountering the change of state.
         */
        memcpy(&spc->spc_aaddr, aaddr, sizeof(struct sockaddr_storage));

        /* Map ipv4 address into v4-mapped-on-v6 address.  */
        sctp_get_pf_specific(asoc->base.sk->sk_family)->addr_v4map(
                                        sctp_sk(asoc->base.sk),
                                        (union sctp_addr *)&spc->spc_aaddr);

        return event;

fail:
        return NULL;
}

/* Create and initialize an SCTP_REMOTE_ERROR notification.
 *
 * Note: This assumes that the chunk->skb->data already points to the
 * operation error payload.
 *
 * Socket Extensions for SCTP - draft-01
 * 5.3.1.3 SCTP_REMOTE_ERROR
 *
 * A remote peer may send an Operational Error message to its peer.
 * This message indicates a variety of error conditions on an
 * association. The entire error TLV as it appears on the wire is
 * included in a SCTP_REMOTE_ERROR event.  Please refer to the SCTP
 * specification [SCTP] and any extensions for a list of possible
 * error formats.
 */
struct sctp_ulpevent *sctp_ulpevent_make_remote_error(
        const struct sctp_association *asoc, struct sctp_chunk *chunk,
        __u16 flags, gfp_t gfp)
{
        struct sctp_ulpevent *event;
        struct sctp_remote_error *sre;
        struct sk_buff *skb;
        sctp_errhdr_t *ch;
        __be16 cause;
        int elen;

        ch = (sctp_errhdr_t *)(chunk->skb->data);
        cause = ch->cause;
        elen = WORD_ROUND(ntohs(ch->length)) - sizeof(sctp_errhdr_t);

        /* Pull off the ERROR header.  */
        skb_pull(chunk->skb, sizeof(sctp_errhdr_t));

        /* Copy the skb to a new skb with room for us to prepend
         * notification with.
         */
        skb = skb_copy_expand(chunk->skb, sizeof(struct sctp_remote_error),
                              0, gfp);

        /* Pull off the rest of the cause TLV from the chunk.  */
        skb_pull(chunk->skb, elen);
        if (!skb)
                goto fail;

        /* Embed the event fields inside the cloned skb.  */
        event = sctp_skb2event(skb);
        sctp_ulpevent_init(event, MSG_NOTIFICATION, skb->truesize);

        sre = (struct sctp_remote_error *)
                skb_push(skb, sizeof(struct sctp_remote_error));

        /* Trim the buffer to the right length.  */
        skb_trim(skb, sizeof(struct sctp_remote_error) + elen);

        /* Socket Extensions for SCTP
         * 5.3.1.3 SCTP_REMOTE_ERROR
         *
         * sre_type:
         *   It should be SCTP_REMOTE_ERROR.
         */
        sre->sre_type = SCTP_REMOTE_ERROR;

        /*
         * Socket Extensions for SCTP
         * 5.3.1.3 SCTP_REMOTE_ERROR
         *
         * sre_flags: 16 bits (unsigned integer)
         *   Currently unused.
         */
        sre->sre_flags = 0;

        /* Socket Extensions for SCTP
         * 5.3.1.3 SCTP_REMOTE_ERROR
         *
         * sre_length: sizeof (__u32)
         *
         * This field is the total length of the notification data,
         * including the notification header.
         */
        sre->sre_length = skb->len;

        /* Socket Extensions for SCTP
         * 5.3.1.3 SCTP_REMOTE_ERROR
         *
         * sre_error: 16 bits (unsigned integer)
         * This value represents one of the Operational Error causes defined in
         * the SCTP specification, in network byte order.
         */
        sre->sre_error = cause;

        /* Socket Extensions for SCTP
         * 5.3.1.3 SCTP_REMOTE_ERROR
         *
         * sre_assoc_id: sizeof (sctp_assoc_t)
         *
         * The association id field, holds the identifier for the association.
         * All notifications for a given association have the same association
         * identifier.  For TCP style socket, this field is ignored.
         */
        sctp_ulpevent_set_owner(event, asoc);
        sre->sre_assoc_id = sctp_assoc2id(asoc);

        return event;

fail:
        return NULL;
}

/* Create and initialize a SCTP_SEND_FAILED notification.
 *
 * Socket Extensions for SCTP - draft-01
 * 5.3.1.4 SCTP_SEND_FAILED
 */
struct sctp_ulpevent *sctp_ulpevent_make_send_failed(
        const struct sctp_association *asoc, struct sctp_chunk *chunk,
        __u16 flags, __u32 error, gfp_t gfp)
{
        struct sctp_ulpevent *event;
        struct sctp_send_failed *ssf;
        struct sk_buff *skb;

        /* Pull off any padding. */
        int len = ntohs(chunk->chunk_hdr->length);

        /* Make skb with more room so we can prepend notification.  */
        skb = skb_copy_expand(chunk->skb,
                              sizeof(struct sctp_send_failed), /* headroom */
                              0,                               /* tailroom */
                              gfp);
        if (!skb)
                goto fail;

        /* Pull off the common chunk header and DATA header.  */
        skb_pull(skb, sizeof(struct sctp_data_chunk));
        len -= sizeof(struct sctp_data_chunk);

        /* Embed the event fields inside the cloned skb.  */
        event = sctp_skb2event(skb);
        sctp_ulpevent_init(event, MSG_NOTIFICATION, skb->truesize);

        ssf = (struct sctp_send_failed *)
                skb_push(skb, sizeof(struct sctp_send_failed));

        /* Socket Extensions for SCTP
         * 5.3.1.4 SCTP_SEND_FAILED
         *
         * ssf_type:
         * It should be SCTP_SEND_FAILED.
         */
        ssf->ssf_type = SCTP_SEND_FAILED;

        /* Socket Extensions for SCTP
         * 5.3.1.4 SCTP_SEND_FAILED
         *
         * ssf_flags: 16 bits (unsigned integer)
         * The flag value will take one of the following values
         *
         * SCTP_DATA_UNSENT - Indicates that the data was never put on
         *                    the wire.
         *
         * SCTP_DATA_SENT   - Indicates that the data was put on the wire.
         *                    Note that this does not necessarily mean that the
         *                    data was (or was not) successfully delivered.
         */
        ssf->ssf_flags = flags;

        /* Socket Extensions for SCTP
         * 5.3.1.4 SCTP_SEND_FAILED
         *
         * ssf_length: sizeof (__u32)
         * This field is the total length of the notification data, including
         * the notification header.
         */
        ssf->ssf_length = sizeof(struct sctp_send_failed) + len;
        skb_trim(skb, ssf->ssf_length);

        /* Socket Extensions for SCTP
         * 5.3.1.4 SCTP_SEND_FAILED
         *
         * ssf_error: 16 bits (unsigned integer)
         * This value represents the reason why the send failed, and if set,
         * will be a SCTP protocol error code as defined in [SCTP] section
         * 3.3.10.
         */
        ssf->ssf_error = error;

        /* Socket Extensions for SCTP
         * 5.3.1.4 SCTP_SEND_FAILED
         *
         * ssf_info: sizeof (struct sctp_sndrcvinfo)
         * The original send information associated with the undelivered
         * message.
         */
        memcpy(&ssf->ssf_info, &chunk->sinfo, sizeof(struct sctp_sndrcvinfo));

        /* Per TSVWG discussion with Randy. Allow the application to
         * ressemble a fragmented message.
         */
        ssf->ssf_info.sinfo_flags = chunk->chunk_hdr->flags;

        /* Socket Extensions for SCTP
         * 5.3.1.4 SCTP_SEND_FAILED
         *
         * ssf_assoc_id: sizeof (sctp_assoc_t)
         * The association id field, sf_assoc_id, holds the identifier for the
         * association.  All notifications for a given association have the
         * same association identifier.  For TCP style socket, this field is
         * ignored.
         */
        sctp_ulpevent_set_owner(event, asoc);
        ssf->ssf_assoc_id = sctp_assoc2id(asoc);
        return event;

fail:
        return NULL;
}

/* Create and initialize a SCTP_SHUTDOWN_EVENT notification.
 *
 * Socket Extensions for SCTP - draft-01
 * 5.3.1.5 SCTP_SHUTDOWN_EVENT
 */
struct sctp_ulpevent *sctp_ulpevent_make_shutdown_event(
        const struct sctp_association *asoc,
        __u16 flags, gfp_t gfp)
{
        struct sctp_ulpevent *event;
        struct sctp_shutdown_event *sse;
        struct sk_buff *skb;

        event = sctp_ulpevent_new(sizeof(struct sctp_shutdown_event),
                                  MSG_NOTIFICATION, gfp);
        if (!event)
                goto fail;

        skb = sctp_event2skb(event);
        sse = (struct sctp_shutdown_event *)
                skb_put(skb, sizeof(struct sctp_shutdown_event));

        /* Socket Extensions for SCTP
         * 5.3.1.5 SCTP_SHUTDOWN_EVENT
         *
         * sse_type
         * It should be SCTP_SHUTDOWN_EVENT
         */
        sse->sse_type = SCTP_SHUTDOWN_EVENT;

        /* Socket Extensions for SCTP
         * 5.3.1.5 SCTP_SHUTDOWN_EVENT
         *
         * sse_flags: 16 bits (unsigned integer)
         * Currently unused.
         */
        sse->sse_flags = 0;

        /* Socket Extensions for SCTP
         * 5.3.1.5 SCTP_SHUTDOWN_EVENT
         *
         * sse_length: sizeof (__u32)
         * This field is the total length of the notification data, including
         * the notification header.
         */
        sse->sse_length = sizeof(struct sctp_shutdown_event);

        /* Socket Extensions for SCTP
         * 5.3.1.5 SCTP_SHUTDOWN_EVENT
         *
         * sse_assoc_id: sizeof (sctp_assoc_t)
         * The association id field, holds the identifier for the association.
         * All notifications for a given association have the same association
         * identifier.  For TCP style socket, this field is ignored.
         */
        sctp_ulpevent_set_owner(event, asoc);
        sse->sse_assoc_id = sctp_assoc2id(asoc);

        return event;

fail:
        return NULL;
}

/* Create and initialize a SCTP_ADAPTATION_INDICATION notification.
 *
 * Socket Extensions for SCTP
 * 5.3.1.6 SCTP_ADAPTATION_INDICATION
 */
struct sctp_ulpevent *sctp_ulpevent_make_adaptation_indication(
        const struct sctp_association *asoc, gfp_t gfp)
{
        struct sctp_ulpevent *event;
        struct sctp_adaptation_event *sai;
        struct sk_buff *skb;

        event = sctp_ulpevent_new(sizeof(struct sctp_adaptation_event),
                                  MSG_NOTIFICATION, gfp);
        if (!event)
                goto fail;

        skb = sctp_event2skb(event);
        sai = (struct sctp_adaptation_event *)
                skb_put(skb, sizeof(struct sctp_adaptation_event));

        sai->sai_type = SCTP_ADAPTATION_INDICATION;
        sai->sai_flags = 0;
        sai->sai_length = sizeof(struct sctp_adaptation_event);
        sai->sai_adaptation_ind = asoc->peer.adaptation_ind;
        sctp_ulpevent_set_owner(event, asoc);
        sai->sai_assoc_id = sctp_assoc2id(asoc);

        return event;

fail:
        return NULL;
}

/* A message has been received.  Package this message as a notification
 * to pass it to the upper layers.  Go ahead and calculate the sndrcvinfo
 * even if filtered out later.
 *
 * Socket Extensions for SCTP
 * 5.2.2 SCTP Header Information Structure (SCTP_SNDRCV)
 */
struct sctp_ulpevent *sctp_ulpevent_make_rcvmsg(struct sctp_association *asoc,
                                                struct sctp_chunk *chunk,
                                                gfp_t gfp)
{
        struct sctp_ulpevent *event = NULL;
        struct sk_buff *skb;
        size_t padding, len;
        int rx_count;

        /*
         * check to see if we need to make space for this
         * new skb, expand the rcvbuffer if needed, or drop
         * the frame
         */
        if (asoc->ep->rcvbuf_policy)
                rx_count = atomic_read(&asoc->rmem_alloc);
        else
                rx_count = atomic_read(&asoc->base.sk->sk_rmem_alloc);

        if (rx_count >= asoc->base.sk->sk_rcvbuf) {

                if ((asoc->base.sk->sk_userlocks & SOCK_RCVBUF_LOCK) ||
                    (!sk_rmem_schedule(asoc->base.sk, chunk->skb->truesize)))
                        goto fail;
        }

        /* Clone the original skb, sharing the data.  */
        skb = skb_clone(chunk->skb, gfp);
        if (!skb)
                goto fail;

        /* Now that all memory allocations for this chunk succeeded, we
         * can mark it as received so the tsn_map is updated correctly.
         */
        if (sctp_tsnmap_mark(&asoc->peer.tsn_map,
                             ntohl(chunk->subh.data_hdr->tsn)))
                goto fail_mark;

        /* First calculate the padding, so we don't inadvertently
         * pass up the wrong length to the user.
         *
         * RFC 2960 - Section 3.2  Chunk Field Descriptions
         *
         * The total length of a chunk(including Type, Length and Value fields)
         * MUST be a multiple of 4 bytes.  If the length of the chunk is not a
         * multiple of 4 bytes, the sender MUST pad the chunk with all zero
         * bytes and this padding is not included in the chunk length field.
         * The sender should never pad with more than 3 bytes.  The receiver
         * MUST ignore the padding bytes.
         */
        len = ntohs(chunk->chunk_hdr->length);
        padding = WORD_ROUND(len) - len;

        /* Fixup cloned skb with just this chunks data.  */
        skb_trim(skb, chunk->chunk_end - padding - skb->data);

        /* Embed the event fields inside the cloned skb.  */
        event = sctp_skb2event(skb);

        /* Initialize event with flags 0  and correct length
         * Since this is a clone of the original skb, only account for
         * the data of this chunk as other chunks will be accounted separately.
         */
        sctp_ulpevent_init(event, 0, skb->len + sizeof(struct sk_buff));

        sctp_ulpevent_receive_data(event, asoc);

        event->stream = ntohs(chunk->subh.data_hdr->stream);
        event->ssn = ntohs(chunk->subh.data_hdr->ssn);
        event->ppid = chunk->subh.data_hdr->ppid;
        if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED) {
                event->flags |= SCTP_UNORDERED;
                event->cumtsn = sctp_tsnmap_get_ctsn(&asoc->peer.tsn_map);
        }
        event->tsn = ntohl(chunk->subh.data_hdr->tsn);
        event->msg_flags |= chunk->chunk_hdr->flags;
        event->iif = sctp_chunk_iif(chunk);

        return event;

fail_mark:
        kfree_skb(skb);
fail:
        return NULL;
}

/* Create a partial delivery related event.
 *
 * 5.3.1.7 SCTP_PARTIAL_DELIVERY_EVENT
 *
 *   When a receiver is engaged in a partial delivery of a
 *   message this notification will be used to indicate
 *   various events.
 */
struct sctp_ulpevent *sctp_ulpevent_make_pdapi(
        const struct sctp_association *asoc, __u32 indication,
        gfp_t gfp)
{
        struct sctp_ulpevent *event;
        struct sctp_pdapi_event *pd;
        struct sk_buff *skb;

        event = sctp_ulpevent_new(sizeof(struct sctp_pdapi_event),
                                  MSG_NOTIFICATION, gfp);
        if (!event)
                goto fail;

        skb = sctp_event2skb(event);
        pd = (struct sctp_pdapi_event *)
                skb_put(skb, sizeof(struct sctp_pdapi_event));

        /* pdapi_type
         *   It should be SCTP_PARTIAL_DELIVERY_EVENT
         *
         * pdapi_flags: 16 bits (unsigned integer)
         *   Currently unused.
         */
        pd->pdapi_type = SCTP_PARTIAL_DELIVERY_EVENT;
        pd->pdapi_flags = 0;

        /* pdapi_length: 32 bits (unsigned integer)
         *
         * This field is the total length of the notification data, including
         * the notification header.  It will generally be sizeof (struct
         * sctp_pdapi_event).
         */
        pd->pdapi_length = sizeof(struct sctp_pdapi_event);

        /*  pdapi_indication: 32 bits (unsigned integer)
         *
         * This field holds the indication being sent to the application.
         */
        pd->pdapi_indication = indication;

        /*  pdapi_assoc_id: sizeof (sctp_assoc_t)
         *
         * The association id field, holds the identifier for the association.
         */
        sctp_ulpevent_set_owner(event, asoc);
        pd->pdapi_assoc_id = sctp_assoc2id(asoc);

        return event;
fail:
        return NULL;
}

struct sctp_ulpevent *sctp_ulpevent_make_authkey(
        const struct sctp_association *asoc, __u16 key_id,
        __u32 indication, gfp_t gfp)
{
        struct sctp_ulpevent *event;
        struct sctp_authkey_event *ak;
        struct sk_buff *skb;

        event = sctp_ulpevent_new(sizeof(struct sctp_authkey_event),
                                  MSG_NOTIFICATION, gfp);
        if (!event)
                goto fail;

        skb = sctp_event2skb(event);
        ak = (struct sctp_authkey_event *)
                skb_put(skb, sizeof(struct sctp_authkey_event));

        ak->auth_type = SCTP_AUTHENTICATION_INDICATION;
        ak->auth_flags = 0;
        ak->auth_length = sizeof(struct sctp_authkey_event);

        ak->auth_keynumber = key_id;
        ak->auth_altkeynumber = 0;
        ak->auth_indication = indication;

        /*
         * The association id field, holds the identifier for the association.
         */
        sctp_ulpevent_set_owner(event, asoc);
        ak->auth_assoc_id = sctp_assoc2id(asoc);

        return event;
fail:
        return NULL;
}


/* Return the notification type, assuming this is a notification
 * event.
 */
__u16 sctp_ulpevent_get_notification_type(const struct sctp_ulpevent *event)
{
        union sctp_notification *notification;
        struct sk_buff *skb;

        skb = sctp_event2skb(event);
        notification = (union sctp_notification *) skb->data;
        return notification->sn_header.sn_type;
}

/* Copy out the sndrcvinfo into a msghdr.  */
void sctp_ulpevent_read_sndrcvinfo(const struct sctp_ulpevent *event,
                                   struct msghdr *msghdr)
{
        struct sctp_sndrcvinfo sinfo;

        if (sctp_ulpevent_is_notification(event))
                return;

        /* Sockets API Extensions for SCTP
         * Section 5.2.2 SCTP Header Information Structure (SCTP_SNDRCV)
         *
         * sinfo_stream: 16 bits (unsigned integer)
         *
         * For recvmsg() the SCTP stack places the message's stream number in
         * this value.
        */
        sinfo.sinfo_stream = event->stream;
        /* sinfo_ssn: 16 bits (unsigned integer)
         *
         * For recvmsg() this value contains the stream sequence number that
         * the remote endpoint placed in the DATA chunk.  For fragmented
         * messages this is the same number for all deliveries of the message
         * (if more than one recvmsg() is needed to read the message).
         */
        sinfo.sinfo_ssn = event->ssn;
        /* sinfo_ppid: 32 bits (unsigned integer)
         *
         * In recvmsg() this value is
         * the same information that was passed by the upper layer in the peer
         * application.  Please note that byte order issues are NOT accounted
         * for and this information is passed opaquely by the SCTP stack from
         * one end to the other.
         */
        sinfo.sinfo_ppid = event->ppid;
        /* sinfo_flags: 16 bits (unsigned integer)
         *
         * This field may contain any of the following flags and is composed of
         * a bitwise OR of these values.
         *
         * recvmsg() flags:
         *
         * SCTP_UNORDERED - This flag is present when the message was sent
         *                 non-ordered.
         */
        sinfo.sinfo_flags = event->flags;
        /* sinfo_tsn: 32 bit (unsigned integer)
         *
         * For the receiving side, this field holds a TSN that was
         * assigned to one of the SCTP Data Chunks.
         */
        sinfo.sinfo_tsn = event->tsn;
        /* sinfo_cumtsn: 32 bit (unsigned integer)
         *
         * This field will hold the current cumulative TSN as
         * known by the underlying SCTP layer.  Note this field is
         * ignored when sending and only valid for a receive
         * operation when sinfo_flags are set to SCTP_UNORDERED.
         */
        sinfo.sinfo_cumtsn = event->cumtsn;
        /* sinfo_assoc_id: sizeof (sctp_assoc_t)
         *
         * The association handle field, sinfo_assoc_id, holds the identifier
         * for the association announced in the COMMUNICATION_UP notification.
         * All notifications for a given association have the same identifier.
         * Ignored for one-to-one style sockets.
         */
        sinfo.sinfo_assoc_id = sctp_assoc2id(event->asoc);

        /* context value that is set via SCTP_CONTEXT socket option. */
        sinfo.sinfo_context = event->asoc->default_rcv_context;

        /* These fields are not used while receiving. */
        sinfo.sinfo_timetolive = 0;

        put_cmsg(msghdr, IPPROTO_SCTP, SCTP_SNDRCV,
                 sizeof(struct sctp_sndrcvinfo), (void *)&sinfo);
}

/* Do accounting for bytes received and hold a reference to the association
 * for each skb.
 */
static void sctp_ulpevent_receive_data(struct sctp_ulpevent *event,
                                       struct sctp_association *asoc)
{
        struct sk_buff *skb, *frag;

        skb = sctp_event2skb(event);
        /* Set the owner and charge rwnd for bytes received.  */
        sctp_ulpevent_set_owner(event, asoc);
        sctp_assoc_rwnd_decrease(asoc, skb_headlen(skb));

        if (!skb->data_len)
                return;

        /* Note:  Not clearing the entire event struct as this is just a
         * fragment of the real event.  However, we still need to do rwnd
         * accounting.
         * In general, the skb passed from IP can have only 1 level of
         * fragments. But we allow multiple levels of fragments.
         */
        skb_walk_frags(skb, frag)
                sctp_ulpevent_receive_data(sctp_skb2event(frag), asoc);
}

/* Do accounting for bytes just read by user and release the references to
 * the association.
 */
static void sctp_ulpevent_release_data(struct sctp_ulpevent *event)
{
        struct sk_buff *skb, *frag;
        unsigned int    len;

        /* Current stack structures assume that the rcv buffer is
         * per socket.   For UDP style sockets this is not true as
         * multiple associations may be on a single UDP-style socket.
         * Use the local private area of the skb to track the owning
         * association.
         */

        skb = sctp_event2skb(event);
        len = skb->len;

        if (!skb->data_len)
                goto done;

        /* Don't forget the fragments. */
        skb_walk_frags(skb, frag) {
                /* NOTE:  skb_shinfos are recursive. Although IP returns
                 * skb's with only 1 level of fragments, SCTP reassembly can
                 * increase the levels.
                 */
                sctp_ulpevent_release_frag_data(sctp_skb2event(frag));
        }

done:
        sctp_assoc_rwnd_increase(event->asoc, len);
        sctp_ulpevent_release_owner(event);
}

static void sctp_ulpevent_release_frag_data(struct sctp_ulpevent *event)
{
        struct sk_buff *skb, *frag;

        skb = sctp_event2skb(event);

        if (!skb->data_len)
                goto done;

        /* Don't forget the fragments. */
        skb_walk_frags(skb, frag) {
                /* NOTE:  skb_shinfos are recursive. Although IP returns
                 * skb's with only 1 level of fragments, SCTP reassembly can
                 * increase the levels.
                 */
                sctp_ulpevent_release_frag_data(sctp_skb2event(frag));
        }

done:
        sctp_ulpevent_release_owner(event);
}

/* Free a ulpevent that has an owner.  It includes releasing the reference
 * to the owner, updating the rwnd in case of a DATA event and freeing the
 * skb.
 */
void sctp_ulpevent_free(struct sctp_ulpevent *event)
{
        if (sctp_ulpevent_is_notification(event))
                sctp_ulpevent_release_owner(event);
        else
                sctp_ulpevent_release_data(event);

        kfree_skb(sctp_event2skb(event));
}

/* Purge the skb lists holding ulpevents. */
void sctp_queue_purge_ulpevents(struct sk_buff_head *list)
{
        struct sk_buff *skb;
        while ((skb = skb_dequeue(list)) != NULL)
                sctp_ulpevent_free(sctp_skb2event(skb));
}