![Vlad Yasevich](/assets/img/avatar_default.png)
SCTP will delay the last part of a large write due to NAGLE, if that part is smaller then MTU. Since we are doing large writes, we might as well send the last portion now instead of waiting untill the next large write happens. The small portion will be sent as is regardless, so it's better to not delay it. This is a result of much discussions with Wei Yongjun <yjwei@cn.fujitsu.com> and Doug Graham <dgraham@nortel.com>. Many thanks go out to them. Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
349 lines
9.2 KiB
C
349 lines
9.2 KiB
C
/* SCTP kernel implementation
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* (C) Copyright IBM Corp. 2003, 2004
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*
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* This file is part of the SCTP kernel implementation
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*
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* This file contains the code relating the chunk abstraction.
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*
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* This SCTP implementation is free software;
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* you can redistribute it and/or modify it under the terms of
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* the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This SCTP implementation is distributed in the hope that it
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* will be useful, but WITHOUT ANY WARRANTY; without even the implied
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* ************************
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* warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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* See the GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GNU CC; see the file COPYING. If not, write to
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* the Free Software Foundation, 59 Temple Place - Suite 330,
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* Boston, MA 02111-1307, USA.
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*
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* Please send any bug reports or fixes you make to the
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* email address(es):
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* lksctp developers <lksctp-developers@lists.sourceforge.net>
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*
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* Or submit a bug report through the following website:
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* http://www.sf.net/projects/lksctp
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*
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* Written or modified by:
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* Jon Grimm <jgrimm@us.ibm.com>
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* Sridhar Samudrala <sri@us.ibm.com>
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*
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* Any bugs reported given to us we will try to fix... any fixes shared will
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* be incorporated into the next SCTP release.
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*/
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/net.h>
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#include <linux/inet.h>
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#include <linux/skbuff.h>
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#include <net/sock.h>
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#include <net/sctp/sctp.h>
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#include <net/sctp/sm.h>
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/* This file is mostly in anticipation of future work, but initially
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* populate with fragment tracking for an outbound message.
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*/
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/* Initialize datamsg from memory. */
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static void sctp_datamsg_init(struct sctp_datamsg *msg)
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{
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atomic_set(&msg->refcnt, 1);
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msg->send_failed = 0;
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msg->send_error = 0;
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msg->can_abandon = 0;
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msg->expires_at = 0;
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INIT_LIST_HEAD(&msg->chunks);
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msg->msg_size = 0;
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}
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/* Allocate and initialize datamsg. */
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SCTP_STATIC struct sctp_datamsg *sctp_datamsg_new(gfp_t gfp)
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{
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struct sctp_datamsg *msg;
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msg = kmalloc(sizeof(struct sctp_datamsg), gfp);
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if (msg) {
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sctp_datamsg_init(msg);
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SCTP_DBG_OBJCNT_INC(datamsg);
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}
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return msg;
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}
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void sctp_datamsg_free(struct sctp_datamsg *msg)
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{
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struct sctp_chunk *chunk;
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/* This doesn't have to be a _safe vairant because
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* sctp_chunk_free() only drops the refs.
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*/
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list_for_each_entry(chunk, &msg->chunks, frag_list)
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sctp_chunk_free(chunk);
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sctp_datamsg_put(msg);
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}
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/* Final destructruction of datamsg memory. */
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static void sctp_datamsg_destroy(struct sctp_datamsg *msg)
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{
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struct list_head *pos, *temp;
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struct sctp_chunk *chunk;
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struct sctp_sock *sp;
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struct sctp_ulpevent *ev;
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struct sctp_association *asoc = NULL;
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int error = 0, notify;
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/* If we failed, we may need to notify. */
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notify = msg->send_failed ? -1 : 0;
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/* Release all references. */
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list_for_each_safe(pos, temp, &msg->chunks) {
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list_del_init(pos);
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chunk = list_entry(pos, struct sctp_chunk, frag_list);
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/* Check whether we _really_ need to notify. */
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if (notify < 0) {
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asoc = chunk->asoc;
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if (msg->send_error)
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error = msg->send_error;
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else
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error = asoc->outqueue.error;
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sp = sctp_sk(asoc->base.sk);
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notify = sctp_ulpevent_type_enabled(SCTP_SEND_FAILED,
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&sp->subscribe);
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}
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/* Generate a SEND FAILED event only if enabled. */
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if (notify > 0) {
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int sent;
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if (chunk->has_tsn)
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sent = SCTP_DATA_SENT;
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else
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sent = SCTP_DATA_UNSENT;
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ev = sctp_ulpevent_make_send_failed(asoc, chunk, sent,
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error, GFP_ATOMIC);
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if (ev)
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sctp_ulpq_tail_event(&asoc->ulpq, ev);
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}
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sctp_chunk_put(chunk);
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}
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SCTP_DBG_OBJCNT_DEC(datamsg);
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kfree(msg);
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}
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/* Hold a reference. */
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static void sctp_datamsg_hold(struct sctp_datamsg *msg)
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{
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atomic_inc(&msg->refcnt);
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}
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/* Release a reference. */
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void sctp_datamsg_put(struct sctp_datamsg *msg)
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{
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if (atomic_dec_and_test(&msg->refcnt))
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sctp_datamsg_destroy(msg);
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}
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/* Assign a chunk to this datamsg. */
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static void sctp_datamsg_assign(struct sctp_datamsg *msg, struct sctp_chunk *chunk)
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{
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sctp_datamsg_hold(msg);
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chunk->msg = msg;
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msg->msg_size += chunk->skb->len;
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}
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/* A data chunk can have a maximum payload of (2^16 - 20). Break
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* down any such message into smaller chunks. Opportunistically, fragment
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* the chunks down to the current MTU constraints. We may get refragmented
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* later if the PMTU changes, but it is _much better_ to fragment immediately
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* with a reasonable guess than always doing our fragmentation on the
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* soft-interrupt.
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*/
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struct sctp_datamsg *sctp_datamsg_from_user(struct sctp_association *asoc,
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struct sctp_sndrcvinfo *sinfo,
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struct msghdr *msgh, int msg_len)
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{
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int max, whole, i, offset, over, err;
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int len, first_len;
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int max_data;
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struct sctp_chunk *chunk;
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struct sctp_datamsg *msg;
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struct list_head *pos, *temp;
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__u8 frag;
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msg = sctp_datamsg_new(GFP_KERNEL);
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if (!msg)
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return NULL;
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/* Note: Calculate this outside of the loop, so that all fragments
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* have the same expiration.
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*/
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if (sinfo->sinfo_timetolive) {
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/* sinfo_timetolive is in milliseconds */
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msg->expires_at = jiffies +
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msecs_to_jiffies(sinfo->sinfo_timetolive);
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msg->can_abandon = 1;
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SCTP_DEBUG_PRINTK("%s: msg:%p expires_at: %ld jiffies:%ld\n",
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__func__, msg, msg->expires_at, jiffies);
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}
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/* This is the biggest possible DATA chunk that can fit into
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* the packet
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*/
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max_data = asoc->pathmtu -
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sctp_sk(asoc->base.sk)->pf->af->net_header_len -
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sizeof(struct sctphdr) - sizeof(struct sctp_data_chunk);
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max = asoc->frag_point;
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/* If the the peer requested that we authenticate DATA chunks
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* we need to accound for bundling of the AUTH chunks along with
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* DATA.
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*/
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if (sctp_auth_send_cid(SCTP_CID_DATA, asoc)) {
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struct sctp_hmac *hmac_desc = sctp_auth_asoc_get_hmac(asoc);
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if (hmac_desc)
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max_data -= WORD_ROUND(sizeof(sctp_auth_chunk_t) +
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hmac_desc->hmac_len);
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}
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/* Now, check if we need to reduce our max */
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if (max > max_data)
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max = max_data;
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whole = 0;
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first_len = max;
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/* Check to see if we have a pending SACK and try to let it be bundled
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* with this message. Do this if we don't have any data queued already.
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* To check that, look at out_qlen and retransmit list.
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* NOTE: we will not reduce to account for SACK, if the message would
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* not have been fragmented.
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*/
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if (timer_pending(&asoc->timers[SCTP_EVENT_TIMEOUT_SACK]) &&
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asoc->outqueue.out_qlen == 0 &&
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list_empty(&asoc->outqueue.retransmit) &&
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msg_len > max)
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max_data -= WORD_ROUND(sizeof(sctp_sack_chunk_t));
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/* Encourage Cookie-ECHO bundling. */
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if (asoc->state < SCTP_STATE_COOKIE_ECHOED)
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max_data -= SCTP_ARBITRARY_COOKIE_ECHO_LEN;
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/* Now that we adjusted completely, reset first_len */
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if (first_len > max_data)
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first_len = max_data;
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/* Account for a different sized first fragment */
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if (msg_len >= first_len) {
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msg_len -= first_len;
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whole = 1;
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}
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/* How many full sized? How many bytes leftover? */
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whole += msg_len / max;
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over = msg_len % max;
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offset = 0;
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if ((whole > 1) || (whole && over))
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SCTP_INC_STATS_USER(SCTP_MIB_FRAGUSRMSGS);
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/* Create chunks for all the full sized DATA chunks. */
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for (i=0, len=first_len; i < whole; i++) {
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frag = SCTP_DATA_MIDDLE_FRAG;
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if (0 == i)
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frag |= SCTP_DATA_FIRST_FRAG;
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if ((i == (whole - 1)) && !over)
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frag |= SCTP_DATA_LAST_FRAG;
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chunk = sctp_make_datafrag_empty(asoc, sinfo, len, frag, 0);
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if (!chunk)
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goto errout;
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err = sctp_user_addto_chunk(chunk, offset, len, msgh->msg_iov);
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if (err < 0)
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goto errout;
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offset += len;
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/* Put the chunk->skb back into the form expected by send. */
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__skb_pull(chunk->skb, (__u8 *)chunk->chunk_hdr
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- (__u8 *)chunk->skb->data);
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sctp_datamsg_assign(msg, chunk);
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list_add_tail(&chunk->frag_list, &msg->chunks);
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/* The first chunk, the first chunk was likely short
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* to allow bundling, so reset to full size.
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*/
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if (0 == i)
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len = max;
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}
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/* .. now the leftover bytes. */
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if (over) {
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if (!whole)
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frag = SCTP_DATA_NOT_FRAG;
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else
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frag = SCTP_DATA_LAST_FRAG;
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chunk = sctp_make_datafrag_empty(asoc, sinfo, over, frag, 0);
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if (!chunk)
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goto errout;
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err = sctp_user_addto_chunk(chunk, offset, over,msgh->msg_iov);
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/* Put the chunk->skb back into the form expected by send. */
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__skb_pull(chunk->skb, (__u8 *)chunk->chunk_hdr
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- (__u8 *)chunk->skb->data);
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if (err < 0)
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goto errout;
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sctp_datamsg_assign(msg, chunk);
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list_add_tail(&chunk->frag_list, &msg->chunks);
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}
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return msg;
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errout:
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list_for_each_safe(pos, temp, &msg->chunks) {
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list_del_init(pos);
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chunk = list_entry(pos, struct sctp_chunk, frag_list);
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sctp_chunk_free(chunk);
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}
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sctp_datamsg_put(msg);
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return NULL;
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}
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/* Check whether this message has expired. */
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int sctp_chunk_abandoned(struct sctp_chunk *chunk)
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{
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struct sctp_datamsg *msg = chunk->msg;
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if (!msg->can_abandon)
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return 0;
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if (time_after(jiffies, msg->expires_at))
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return 1;
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return 0;
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}
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/* This chunk (and consequently entire message) has failed in its sending. */
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void sctp_chunk_fail(struct sctp_chunk *chunk, int error)
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{
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chunk->msg->send_failed = 1;
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chunk->msg->send_error = error;
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}
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