WSL2-Linux-Kernel/net/sctp/ulpevent.c

// SPDX-License-Identifier: GPL-2.0-or-later
/* 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).
 *
 * 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>
 *    La Monte H.P. Yarroll <piggy@acm.org>
 *    Ardelle Fan	    <ardelle.fan@intel.com>
 *    Sridhar Samudrala     <sri@us.ibm.com>
 */

#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.  */
static void sctp_ulpevent_init(struct sctp_ulpevent *event,
			       __u16 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.  */
static struct sctp_ulpevent *sctp_ulpevent_new(int size, __u16 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 sctp_chunk *chunk = event->chunk;
	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);
	if (chunk && chunk->head_skb && !chunk->head_skb->sk)
		chunk->head_skb->sk = 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 = 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(struct sctp_chunkhdr));
	} else {
		event = sctp_ulpevent_new(sizeof(struct sctp_assoc_change),
				  MSG_NOTIFICATION, gfp);
		if (!event)
			goto fail;

		skb = sctp_event2skb(event);
		sac = 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.
 */
static 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 = 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_to_user(
					sctp_sk(asoc->base.sk),
					(union sctp_addr *)&spc->spc_aaddr);

	return event;

fail:
	return NULL;
}

void sctp_ulpevent_nofity_peer_addr_change(struct sctp_transport *transport,
					   int state, int error)
{
	struct sctp_association *asoc = transport->asoc;
	struct sockaddr_storage addr;
	struct sctp_ulpevent *event;

	memset(&addr, 0, sizeof(struct sockaddr_storage));
	memcpy(&addr, &transport->ipaddr, transport->af_specific->sockaddr_len);

	event = sctp_ulpevent_make_peer_addr_change(asoc, &addr, 0, state,
						    error, GFP_ATOMIC);
	if (event)
		asoc->stream.si->enqueue_event(&asoc->ulpq, event);
}

/* 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_remote_error *sre;
	struct sctp_ulpevent *event;
	struct sctp_errhdr *ch;
	struct sk_buff *skb;
	__be16 cause;
	int elen;

	ch = (struct sctp_errhdr *)(chunk->skb->data);
	cause = ch->cause;
	elen = SCTP_PAD4(ntohs(ch->length)) - sizeof(*ch);

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

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

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

	/* RFC6458, Section 6.1.3. SCTP_REMOTE_ERROR */
	memset(sre, 0, sizeof(*sre));
	sre->sre_type = SCTP_REMOTE_ERROR;
	sre->sre_flags = 0;
	sre->sre_length = skb->len;
	sre->sre_error = cause;
	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, sctp_datachk_len(&asoc->stream));
	len -= sctp_datachk_len(&asoc->stream);

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

	ssf = 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
	 * reassemble 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;
}

struct sctp_ulpevent *sctp_ulpevent_make_send_failed_event(
	const struct sctp_association *asoc, struct sctp_chunk *chunk,
	__u16 flags, __u32 error, gfp_t gfp)
{
	struct sctp_send_failed_event *ssf;
	struct sctp_ulpevent *event;
	struct sk_buff *skb;
	int len;

	skb = skb_copy_expand(chunk->skb, sizeof(*ssf), 0, gfp);
	if (!skb)
		return NULL;

	len = ntohs(chunk->chunk_hdr->length);
	len -= sctp_datachk_len(&asoc->stream);

	skb_pull(skb, sctp_datachk_len(&asoc->stream));
	event = sctp_skb2event(skb);
	sctp_ulpevent_init(event, MSG_NOTIFICATION, skb->truesize);

	ssf = skb_push(skb, sizeof(*ssf));
	ssf->ssf_type = SCTP_SEND_FAILED_EVENT;
	ssf->ssf_flags = flags;
	ssf->ssf_length = sizeof(*ssf) + len;
	skb_trim(skb, ssf->ssf_length);
	ssf->ssf_error = error;

	ssf->ssfe_info.snd_sid = chunk->sinfo.sinfo_stream;
	ssf->ssfe_info.snd_ppid = chunk->sinfo.sinfo_ppid;
	ssf->ssfe_info.snd_context = chunk->sinfo.sinfo_context;
	ssf->ssfe_info.snd_assoc_id = chunk->sinfo.sinfo_assoc_id;
	ssf->ssfe_info.snd_flags = chunk->chunk_hdr->flags;

	sctp_ulpevent_set_owner(event, asoc);
	ssf->ssf_assoc_id = sctp_assoc2id(asoc);

	return event;
}

/* 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 = 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 = 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 = chunk->skb;
	struct sock *sk = asoc->base.sk;
	size_t padding, datalen;
	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(&sk->sk_rmem_alloc);

	datalen = ntohs(chunk->chunk_hdr->length);

	if (rx_count >= sk->sk_rcvbuf || !sk_rmem_schedule(sk, skb, datalen))
		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),
			     chunk->transport))
		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.
	 */
	padding = SCTP_PAD4(datalen) - datalen;

	/* 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));

	/* And hold the chunk as we need it for getting the IP headers
	 * later in recvmsg
	 */
	sctp_chunk_hold(chunk);
	event->chunk = chunk;

	sctp_ulpevent_receive_data(event, asoc);

	event->stream = ntohs(chunk->subh.data_hdr->stream);
	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;

	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, __u32 sid, __u32 seq,
					__u32 flags, 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 = 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 = flags;
	pd->pdapi_stream = sid;
	pd->pdapi_seq = seq;

	/* 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 = skb_put(skb, sizeof(struct sctp_authkey_event));

	ak->auth_type = SCTP_AUTHENTICATION_EVENT;
	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;
}

/*
 * Socket Extensions for SCTP
 * 6.3.10. SCTP_SENDER_DRY_EVENT
 */
struct sctp_ulpevent *sctp_ulpevent_make_sender_dry_event(
	const struct sctp_association *asoc, gfp_t gfp)
{
	struct sctp_ulpevent *event;
	struct sctp_sender_dry_event *sdry;
	struct sk_buff *skb;

	event = sctp_ulpevent_new(sizeof(struct sctp_sender_dry_event),
				  MSG_NOTIFICATION, gfp);
	if (!event)
		return NULL;

	skb = sctp_event2skb(event);
	sdry = skb_put(skb, sizeof(struct sctp_sender_dry_event));

	sdry->sender_dry_type = SCTP_SENDER_DRY_EVENT;
	sdry->sender_dry_flags = 0;
	sdry->sender_dry_length = sizeof(struct sctp_sender_dry_event);
	sctp_ulpevent_set_owner(event, asoc);
	sdry->sender_dry_assoc_id = sctp_assoc2id(asoc);

	return event;
}

struct sctp_ulpevent *sctp_ulpevent_make_stream_reset_event(
	const struct sctp_association *asoc, __u16 flags, __u16 stream_num,
	__be16 *stream_list, gfp_t gfp)
{
	struct sctp_stream_reset_event *sreset;
	struct sctp_ulpevent *event;
	struct sk_buff *skb;
	int length, i;

	length = sizeof(struct sctp_stream_reset_event) + 2 * stream_num;
	event = sctp_ulpevent_new(length, MSG_NOTIFICATION, gfp);
	if (!event)
		return NULL;

	skb = sctp_event2skb(event);
	sreset = skb_put(skb, length);

	sreset->strreset_type = SCTP_STREAM_RESET_EVENT;
	sreset->strreset_flags = flags;
	sreset->strreset_length = length;
	sctp_ulpevent_set_owner(event, asoc);
	sreset->strreset_assoc_id = sctp_assoc2id(asoc);

	for (i = 0; i < stream_num; i++)
		sreset->strreset_stream_list[i] = ntohs(stream_list[i]);

	return event;
}

struct sctp_ulpevent *sctp_ulpevent_make_assoc_reset_event(
	const struct sctp_association *asoc, __u16 flags, __u32 local_tsn,
	__u32 remote_tsn, gfp_t gfp)
{
	struct sctp_assoc_reset_event *areset;
	struct sctp_ulpevent *event;
	struct sk_buff *skb;

	event = sctp_ulpevent_new(sizeof(struct sctp_assoc_reset_event),
				  MSG_NOTIFICATION, gfp);
	if (!event)
		return NULL;

	skb = sctp_event2skb(event);
	areset = skb_put(skb, sizeof(struct sctp_assoc_reset_event));

	areset->assocreset_type = SCTP_ASSOC_RESET_EVENT;
	areset->assocreset_flags = flags;
	areset->assocreset_length = sizeof(struct sctp_assoc_reset_event);
	sctp_ulpevent_set_owner(event, asoc);
	areset->assocreset_assoc_id = sctp_assoc2id(asoc);
	areset->assocreset_local_tsn = local_tsn;
	areset->assocreset_remote_tsn = remote_tsn;

	return event;
}

struct sctp_ulpevent *sctp_ulpevent_make_stream_change_event(
	const struct sctp_association *asoc, __u16 flags,
	__u32 strchange_instrms, __u32 strchange_outstrms, gfp_t gfp)
{
	struct sctp_stream_change_event *schange;
	struct sctp_ulpevent *event;
	struct sk_buff *skb;

	event = sctp_ulpevent_new(sizeof(struct sctp_stream_change_event),
				  MSG_NOTIFICATION, gfp);
	if (!event)
		return NULL;

	skb = sctp_event2skb(event);
	schange = skb_put(skb, sizeof(struct sctp_stream_change_event));

	schange->strchange_type = SCTP_STREAM_CHANGE_EVENT;
	schange->strchange_flags = flags;
	schange->strchange_length = sizeof(struct sctp_stream_change_event);
	sctp_ulpevent_set_owner(event, asoc);
	schange->strchange_assoc_id = sctp_assoc2id(asoc);
	schange->strchange_instrms = strchange_instrms;
	schange->strchange_outstrms = strchange_outstrms;

	return event;
}

/* 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;
}

/* RFC6458, Section 5.3.2. SCTP Header Information Structure
 * (SCTP_SNDRCV, DEPRECATED)
 */
void sctp_ulpevent_read_sndrcvinfo(const struct sctp_ulpevent *event,
				   struct msghdr *msghdr)
{
	struct sctp_sndrcvinfo sinfo;

	if (sctp_ulpevent_is_notification(event))
		return;

	memset(&sinfo, 0, sizeof(sinfo));
	sinfo.sinfo_stream = event->stream;
	sinfo.sinfo_ssn = event->ssn;
	sinfo.sinfo_ppid = event->ppid;
	sinfo.sinfo_flags = event->flags;
	sinfo.sinfo_tsn = event->tsn;
	sinfo.sinfo_cumtsn = event->cumtsn;
	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(sinfo), &sinfo);
}

/* RFC6458, Section 5.3.5 SCTP Receive Information Structure
 * (SCTP_SNDRCV)
 */
void sctp_ulpevent_read_rcvinfo(const struct sctp_ulpevent *event,
				struct msghdr *msghdr)
{
	struct sctp_rcvinfo rinfo;

	if (sctp_ulpevent_is_notification(event))
		return;

	memset(&rinfo, 0, sizeof(struct sctp_rcvinfo));
	rinfo.rcv_sid = event->stream;
	rinfo.rcv_ssn = event->ssn;
	rinfo.rcv_ppid = event->ppid;
	rinfo.rcv_flags = event->flags;
	rinfo.rcv_tsn = event->tsn;
	rinfo.rcv_cumtsn = event->cumtsn;
	rinfo.rcv_assoc_id = sctp_assoc2id(event->asoc);
	rinfo.rcv_context = event->asoc->default_rcv_context;

	put_cmsg(msghdr, IPPROTO_SCTP, SCTP_RCVINFO,
		 sizeof(rinfo), &rinfo);
}

/* RFC6458, Section 5.3.6. SCTP Next Receive Information Structure
 * (SCTP_NXTINFO)
 */
static void __sctp_ulpevent_read_nxtinfo(const struct sctp_ulpevent *event,
					 struct msghdr *msghdr,
					 const struct sk_buff *skb)
{
	struct sctp_nxtinfo nxtinfo;

	memset(&nxtinfo, 0, sizeof(nxtinfo));
	nxtinfo.nxt_sid = event->stream;
	nxtinfo.nxt_ppid = event->ppid;
	nxtinfo.nxt_flags = event->flags;
	if (sctp_ulpevent_is_notification(event))
		nxtinfo.nxt_flags |= SCTP_NOTIFICATION;
	nxtinfo.nxt_length = skb->len;
	nxtinfo.nxt_assoc_id = sctp_assoc2id(event->asoc);

	put_cmsg(msghdr, IPPROTO_SCTP, SCTP_NXTINFO,
		 sizeof(nxtinfo), &nxtinfo);
}

void sctp_ulpevent_read_nxtinfo(const struct sctp_ulpevent *event,
				struct msghdr *msghdr,
				struct sock *sk)
{
	struct sk_buff *skb;
	int err;

	skb = sctp_skb_recv_datagram(sk, MSG_PEEK, 1, &err);
	if (skb != NULL) {
		__sctp_ulpevent_read_nxtinfo(sctp_skb2event(skb),
					     msghdr, skb);
		/* Just release refcount here. */
		kfree_skb(skb);
	}
}

/* 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_chunk_put(event->chunk);
	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_chunk_put(event->chunk);
	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. */
unsigned int sctp_queue_purge_ulpevents(struct sk_buff_head *list)
{
	struct sk_buff *skb;
	unsigned int data_unread = 0;

	while ((skb = skb_dequeue(list)) != NULL) {
		struct sctp_ulpevent *event = sctp_skb2event(skb);

		if (!sctp_ulpevent_is_notification(event))
			data_unread += skb->len;

		sctp_ulpevent_free(event);
	}

	return data_unread;
}