/* 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.
   *
   * 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, see
   * <http://www.gnu.org/licenses/>.
   *
   * 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)
  {
  	atomic_set(&msg->refcnt, 1);
  	msg->send_failed = 0;
  	msg->send_error = 0;
  	msg->can_abandon = 0;
  	msg->can_delay = 1;
  	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(sizeof(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 list_head *pos, *temp;
  	struct sctp_chunk *chunk;
  	struct sctp_sock *sp;
  	struct sctp_ulpevent *ev;
  	struct sctp_association *asoc = NULL;
  	int error = 0, notify;
  
  	/* If we failed, we may need to notify. */
  	notify = msg->send_failed ? -1 : 0;
  
  	/* Release all references. */
  	list_for_each_safe(pos, temp, &msg->chunks) {
  		list_del_init(pos);
  		chunk = list_entry(pos, struct sctp_chunk, frag_list);
  		/* Check whether we _really_ need to notify. */
  		if (notify < 0) {
  			asoc = chunk->asoc;
  			if (msg->send_error)
  				error = msg->send_error;
  			else
  				error = asoc->outqueue.error;
  
  			sp = sctp_sk(asoc->base.sk);
  			notify = sctp_ulpevent_type_enabled(SCTP_SEND_FAILED,
  							    &sp->subscribe);
  		}
  
  		/* Generate a SEND FAILED event only if enabled. */
  		if (notify > 0) {
  			int sent;
  			if (chunk->has_tsn)
  				sent = SCTP_DATA_SENT;
  			else
  				sent = SCTP_DATA_UNSENT;
  
  			ev = sctp_ulpevent_make_send_failed(asoc, chunk, sent,
  							    error, GFP_ATOMIC);
  			if (ev)
  				sctp_ulpq_tail_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)
  {
  	atomic_inc(&msg->refcnt);
  }
  
  /* Release a reference. */
  void sctp_datamsg_put(struct sctp_datamsg *msg)
  {
  	if (atomic_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 msghdr *msgh, int msg_len)
  {
  	int max, whole, i, offset, over, err;
  	int len, first_len;
  	int max_data;
  	struct sctp_chunk *chunk;
  	struct sctp_datamsg *msg;
  	struct list_head *pos, *temp;
  	__u8 frag;
  
  	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 (sinfo->sinfo_timetolive) {
  		/* sinfo_timetolive is in milliseconds */
  		msg->expires_at = jiffies +
  				    msecs_to_jiffies(sinfo->sinfo_timetolive);
  		msg->can_abandon = 1;
  
  		pr_debug("%s: msg:%p expires_at:%ld jiffies:%ld
  ", __func__,
  			 msg, msg->expires_at, jiffies);
  	}
  
  	/* This is the biggest possible DATA chunk that can fit into
  	 * the packet
  	 */
  	max_data = (asoc->pathmtu -
  		sctp_sk(asoc->base.sk)->pf->af->net_header_len -
  		sizeof(struct sctphdr) - sizeof(struct sctp_data_chunk)) & ~3;
  
  	max = asoc->frag_point;
  	/* If the 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)) {
  		struct sctp_hmac *hmac_desc = sctp_auth_asoc_get_hmac(asoc);
  
  		if (hmac_desc)
  			max_data -= WORD_ROUND(sizeof(sctp_auth_chunk_t) +
  					    hmac_desc->hmac_len);
  	}
  
  	/* Now, check if we need to reduce our max */
  	if (max > max_data)
  		max = max_data;
  
  	whole = 0;
  	first_len = max;
  
  	/* 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)
  		max_data -= WORD_ROUND(sizeof(sctp_sack_chunk_t));
  
  	/* Encourage Cookie-ECHO bundling. */
  	if (asoc->state < SCTP_STATE_COOKIE_ECHOED)
  		max_data -= SCTP_ARBITRARY_COOKIE_ECHO_LEN;
  
  	/* Now that we adjusted completely, reset first_len */
  	if (first_len > max_data)
  		first_len = max_data;
  
  	/* Account for a different sized first fragment */
  	if (msg_len >= first_len) {
  		msg_len -= first_len;
  		whole = 1;
  		msg->can_delay = 0;
  	}
  
  	/* How many full sized?  How many bytes leftover? */
  	whole += msg_len / max;
  	over = msg_len % max;
  	offset = 0;
  
  	if ((whole > 1) || (whole && over))
  		SCTP_INC_STATS_USER(sock_net(asoc->base.sk), SCTP_MIB_FRAGUSRMSGS);
  
  	/* Create chunks for all the full sized DATA chunks. */
  	for (i = 0, len = first_len; i < whole; i++) {
  		frag = SCTP_DATA_MIDDLE_FRAG;
  
  		if (0 == i)
  			frag |= SCTP_DATA_FIRST_FRAG;
  
  		if ((i == (whole - 1)) && !over) {
  			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 = sctp_make_datafrag_empty(asoc, sinfo, len, frag, 0);
  
  		if (!chunk) {
  			err = -ENOMEM;
  			goto errout;
  		}
  
  		err = sctp_user_addto_chunk(chunk, offset, len, msgh->msg_iov);
  		if (err < 0)
  			goto errout_chunk_free;
  
  		offset += len;
  
  		/* Put the chunk->skb back into the form expected by send.  */
  		__skb_pull(chunk->skb, (__u8 *)chunk->chunk_hdr
  			   - (__u8 *)chunk->skb->data);
  
  		sctp_datamsg_assign(msg, chunk);
  		list_add_tail(&chunk->frag_list, &msg->chunks);
  
  		/* The first chunk, the first chunk was likely short
  		 * to allow bundling, so reset to full size.
  		 */
  		if (0 == i)
  			len = max;
  	}
  
  	/* .. now the leftover bytes. */
  	if (over) {
  		if (!whole)
  			frag = SCTP_DATA_NOT_FRAG;
  		else
  			frag = SCTP_DATA_LAST_FRAG;
  
  		if ((sinfo->sinfo_flags & SCTP_EOF) ||
  		    (sinfo->sinfo_flags & SCTP_SACK_IMMEDIATELY))
  			frag |= SCTP_DATA_SACK_IMM;
  
  		chunk = sctp_make_datafrag_empty(asoc, sinfo, over, frag, 0);
  
  		if (!chunk) {
  			err = -ENOMEM;
  			goto errout;
  		}
  
  		err = sctp_user_addto_chunk(chunk, offset, over, msgh->msg_iov);
  
  		/* Put the chunk->skb back into the form expected by send.  */
  		__skb_pull(chunk->skb, (__u8 *)chunk->chunk_hdr
  			   - (__u8 *)chunk->skb->data);
  		if (err < 0)
  			goto errout_chunk_free;
  
  		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)
  {
  	struct sctp_datamsg *msg = chunk->msg;
  
  	if (!msg->can_abandon)
  		return 0;
  
  	if (time_after(jiffies, msg->expires_at))
  		return 1;
  
  	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;
  }