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output.c (24123B)


      1 /* SCTP kernel implementation
      2  * (C) Copyright IBM Corp. 2001, 2004
      3  * Copyright (c) 1999-2000 Cisco, Inc.
      4  * Copyright (c) 1999-2001 Motorola, Inc.
      5  *
      6  * This file is part of the SCTP kernel implementation
      7  *
      8  * These functions handle output processing.
      9  *
     10  * This SCTP implementation is free software;
     11  * you can redistribute it and/or modify it under the terms of
     12  * the GNU General Public License as published by
     13  * the Free Software Foundation; either version 2, or (at your option)
     14  * any later version.
     15  *
     16  * This SCTP implementation is distributed in the hope that it
     17  * will be useful, but WITHOUT ANY WARRANTY; without even the implied
     18  *                 ************************
     19  * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
     20  * See the GNU General Public License for more details.
     21  *
     22  * You should have received a copy of the GNU General Public License
     23  * along with GNU CC; see the file COPYING.  If not, see
     24  * <http://www.gnu.org/licenses/>.
     25  *
     26  * Please send any bug reports or fixes you make to the
     27  * email address(es):
     28  *    lksctp developers <linux-sctp@vger.kernel.org>
     29  *
     30  * Written or modified by:
     31  *    La Monte H.P. Yarroll <piggy@acm.org>
     32  *    Karl Knutson          <karl@athena.chicago.il.us>
     33  *    Jon Grimm             <jgrimm@austin.ibm.com>
     34  *    Sridhar Samudrala     <sri@us.ibm.com>
     35  */
     36 
     37 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
     38 
     39 #include <linux/types.h>
     40 #include <linux/kernel.h>
     41 #include <linux/wait.h>
     42 #include <linux/time.h>
     43 #include <linux/ip.h>
     44 #include <linux/ipv6.h>
     45 #include <linux/init.h>
     46 #include <linux/slab.h>
     47 #include <net/inet_ecn.h>
     48 #include <net/ip.h>
     49 #include <net/icmp.h>
     50 #include <net/net_namespace.h>
     51 
     52 #include <linux/socket.h> /* for sa_family_t */
     53 #include <net/sock.h>
     54 
     55 #include <net/sctp/sctp.h>
     56 #include <net/sctp/sm.h>
     57 #include <net/sctp/checksum.h>
     58 
     59 /* Forward declarations for private helpers. */
     60 static enum sctp_xmit __sctp_packet_append_chunk(struct sctp_packet *packet,
     61 						 struct sctp_chunk *chunk);
     62 static enum sctp_xmit sctp_packet_can_append_data(struct sctp_packet *packet,
     63 						  struct sctp_chunk *chunk);
     64 static void sctp_packet_append_data(struct sctp_packet *packet,
     65 				    struct sctp_chunk *chunk);
     66 static enum sctp_xmit sctp_packet_will_fit(struct sctp_packet *packet,
     67 					   struct sctp_chunk *chunk,
     68 					   u16 chunk_len);
     69 
     70 static void sctp_packet_reset(struct sctp_packet *packet)
     71 {
     72 	/* sctp_packet_transmit() relies on this to reset size to the
     73 	 * current overhead after sending packets.
     74 	 */
     75 	packet->size = packet->overhead;
     76 
     77 	packet->has_cookie_echo = 0;
     78 	packet->has_sack = 0;
     79 	packet->has_data = 0;
     80 	packet->has_auth = 0;
     81 	packet->ipfragok = 0;
     82 	packet->auth = NULL;
     83 }
     84 
     85 /* Config a packet.
     86  * This appears to be a followup set of initializations.
     87  */
     88 void sctp_packet_config(struct sctp_packet *packet, __u32 vtag,
     89 			int ecn_capable)
     90 {
     91 	struct sctp_transport *tp = packet->transport;
     92 	struct sctp_association *asoc = tp->asoc;
     93 	struct sctp_sock *sp = NULL;
     94 	struct sock *sk;
     95 
     96 	pr_debug("%s: packet:%p vtag:0x%x\n", __func__, packet, vtag);
     97 	packet->vtag = vtag;
     98 
     99 	/* do the following jobs only once for a flush schedule */
    100 	if (!sctp_packet_empty(packet))
    101 		return;
    102 
    103 	/* set packet max_size with pathmtu, then calculate overhead */
    104 	packet->max_size = tp->pathmtu;
    105 
    106 	if (asoc) {
    107 		sk = asoc->base.sk;
    108 		sp = sctp_sk(sk);
    109 	}
    110 	packet->overhead = sctp_mtu_payload(sp, 0, 0);
    111 	packet->size = packet->overhead;
    112 
    113 	if (!asoc)
    114 		return;
    115 
    116 	/* update dst or transport pathmtu if in need */
    117 	if (!sctp_transport_dst_check(tp)) {
    118 		sctp_transport_route(tp, NULL, sp);
    119 		if (asoc->param_flags & SPP_PMTUD_ENABLE)
    120 			sctp_assoc_sync_pmtu(asoc);
    121 	} else if (!sctp_transport_pmtu_check(tp)) {
    122 		if (asoc->param_flags & SPP_PMTUD_ENABLE)
    123 			sctp_assoc_sync_pmtu(asoc);
    124 	}
    125 
    126 	if (asoc->pmtu_pending) {
    127 		if (asoc->param_flags & SPP_PMTUD_ENABLE)
    128 			sctp_assoc_sync_pmtu(asoc);
    129 		asoc->pmtu_pending = 0;
    130 	}
    131 
    132 	/* If there a is a prepend chunk stick it on the list before
    133 	 * any other chunks get appended.
    134 	 */
    135 	if (ecn_capable) {
    136 		struct sctp_chunk *chunk = sctp_get_ecne_prepend(asoc);
    137 
    138 		if (chunk)
    139 			sctp_packet_append_chunk(packet, chunk);
    140 	}
    141 
    142 	if (!tp->dst)
    143 		return;
    144 
    145 	/* set packet max_size with gso_max_size if gso is enabled*/
    146 	rcu_read_lock();
    147 	if (__sk_dst_get(sk) != tp->dst) {
    148 		dst_hold(tp->dst);
    149 		sk_setup_caps(sk, tp->dst);
    150 	}
    151 	packet->max_size = sk_can_gso(sk) ? tp->dst->dev->gso_max_size
    152 					  : asoc->pathmtu;
    153 	rcu_read_unlock();
    154 }
    155 
    156 /* Initialize the packet structure. */
    157 void sctp_packet_init(struct sctp_packet *packet,
    158 		      struct sctp_transport *transport,
    159 		      __u16 sport, __u16 dport)
    160 {
    161 	pr_debug("%s: packet:%p transport:%p\n", __func__, packet, transport);
    162 
    163 	packet->transport = transport;
    164 	packet->source_port = sport;
    165 	packet->destination_port = dport;
    166 	INIT_LIST_HEAD(&packet->chunk_list);
    167 	/* The overhead will be calculated by sctp_packet_config() */
    168 	packet->overhead = 0;
    169 	sctp_packet_reset(packet);
    170 	packet->vtag = 0;
    171 }
    172 
    173 /* Free a packet.  */
    174 void sctp_packet_free(struct sctp_packet *packet)
    175 {
    176 	struct sctp_chunk *chunk, *tmp;
    177 
    178 	pr_debug("%s: packet:%p\n", __func__, packet);
    179 
    180 	list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
    181 		list_del_init(&chunk->list);
    182 		sctp_chunk_free(chunk);
    183 	}
    184 }
    185 
    186 /* This routine tries to append the chunk to the offered packet. If adding
    187  * the chunk causes the packet to exceed the path MTU and COOKIE_ECHO chunk
    188  * is not present in the packet, it transmits the input packet.
    189  * Data can be bundled with a packet containing a COOKIE_ECHO chunk as long
    190  * as it can fit in the packet, but any more data that does not fit in this
    191  * packet can be sent only after receiving the COOKIE_ACK.
    192  */
    193 enum sctp_xmit sctp_packet_transmit_chunk(struct sctp_packet *packet,
    194 					  struct sctp_chunk *chunk,
    195 					  int one_packet, gfp_t gfp)
    196 {
    197 	enum sctp_xmit retval;
    198 
    199 	pr_debug("%s: packet:%p size:%zu chunk:%p size:%d\n", __func__,
    200 		 packet, packet->size, chunk, chunk->skb ? chunk->skb->len : -1);
    201 
    202 	switch ((retval = (sctp_packet_append_chunk(packet, chunk)))) {
    203 	case SCTP_XMIT_PMTU_FULL:
    204 		if (!packet->has_cookie_echo) {
    205 			int error = 0;
    206 
    207 			error = sctp_packet_transmit(packet, gfp);
    208 			if (error < 0)
    209 				chunk->skb->sk->sk_err = -error;
    210 
    211 			/* If we have an empty packet, then we can NOT ever
    212 			 * return PMTU_FULL.
    213 			 */
    214 			if (!one_packet)
    215 				retval = sctp_packet_append_chunk(packet,
    216 								  chunk);
    217 		}
    218 		break;
    219 
    220 	case SCTP_XMIT_RWND_FULL:
    221 	case SCTP_XMIT_OK:
    222 	case SCTP_XMIT_DELAY:
    223 		break;
    224 	}
    225 
    226 	return retval;
    227 }
    228 
    229 /* Try to bundle an auth chunk into the packet. */
    230 static enum sctp_xmit sctp_packet_bundle_auth(struct sctp_packet *pkt,
    231 					      struct sctp_chunk *chunk)
    232 {
    233 	struct sctp_association *asoc = pkt->transport->asoc;
    234 	enum sctp_xmit retval = SCTP_XMIT_OK;
    235 	struct sctp_chunk *auth;
    236 
    237 	/* if we don't have an association, we can't do authentication */
    238 	if (!asoc)
    239 		return retval;
    240 
    241 	/* See if this is an auth chunk we are bundling or if
    242 	 * auth is already bundled.
    243 	 */
    244 	if (chunk->chunk_hdr->type == SCTP_CID_AUTH || pkt->has_auth)
    245 		return retval;
    246 
    247 	/* if the peer did not request this chunk to be authenticated,
    248 	 * don't do it
    249 	 */
    250 	if (!chunk->auth)
    251 		return retval;
    252 
    253 	auth = sctp_make_auth(asoc, chunk->shkey->key_id);
    254 	if (!auth)
    255 		return retval;
    256 
    257 	auth->shkey = chunk->shkey;
    258 	sctp_auth_shkey_hold(auth->shkey);
    259 
    260 	retval = __sctp_packet_append_chunk(pkt, auth);
    261 
    262 	if (retval != SCTP_XMIT_OK)
    263 		sctp_chunk_free(auth);
    264 
    265 	return retval;
    266 }
    267 
    268 /* Try to bundle a SACK with the packet. */
    269 static enum sctp_xmit sctp_packet_bundle_sack(struct sctp_packet *pkt,
    270 					      struct sctp_chunk *chunk)
    271 {
    272 	enum sctp_xmit retval = SCTP_XMIT_OK;
    273 
    274 	/* If sending DATA and haven't aleady bundled a SACK, try to
    275 	 * bundle one in to the packet.
    276 	 */
    277 	if (sctp_chunk_is_data(chunk) && !pkt->has_sack &&
    278 	    !pkt->has_cookie_echo) {
    279 		struct sctp_association *asoc;
    280 		struct timer_list *timer;
    281 		asoc = pkt->transport->asoc;
    282 		timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
    283 
    284 		/* If the SACK timer is running, we have a pending SACK */
    285 		if (timer_pending(timer)) {
    286 			struct sctp_chunk *sack;
    287 
    288 			if (pkt->transport->sack_generation !=
    289 			    pkt->transport->asoc->peer.sack_generation)
    290 				return retval;
    291 
    292 			asoc->a_rwnd = asoc->rwnd;
    293 			sack = sctp_make_sack(asoc);
    294 			if (sack) {
    295 				retval = __sctp_packet_append_chunk(pkt, sack);
    296 				if (retval != SCTP_XMIT_OK) {
    297 					sctp_chunk_free(sack);
    298 					goto out;
    299 				}
    300 				asoc->peer.sack_needed = 0;
    301 				if (del_timer(timer))
    302 					sctp_association_put(asoc);
    303 			}
    304 		}
    305 	}
    306 out:
    307 	return retval;
    308 }
    309 
    310 
    311 /* Append a chunk to the offered packet reporting back any inability to do
    312  * so.
    313  */
    314 static enum sctp_xmit __sctp_packet_append_chunk(struct sctp_packet *packet,
    315 						 struct sctp_chunk *chunk)
    316 {
    317 	__u16 chunk_len = SCTP_PAD4(ntohs(chunk->chunk_hdr->length));
    318 	enum sctp_xmit retval = SCTP_XMIT_OK;
    319 
    320 	/* Check to see if this chunk will fit into the packet */
    321 	retval = sctp_packet_will_fit(packet, chunk, chunk_len);
    322 	if (retval != SCTP_XMIT_OK)
    323 		goto finish;
    324 
    325 	/* We believe that this chunk is OK to add to the packet */
    326 	switch (chunk->chunk_hdr->type) {
    327 	case SCTP_CID_DATA:
    328 	case SCTP_CID_I_DATA:
    329 		/* Account for the data being in the packet */
    330 		sctp_packet_append_data(packet, chunk);
    331 		/* Disallow SACK bundling after DATA. */
    332 		packet->has_sack = 1;
    333 		/* Disallow AUTH bundling after DATA */
    334 		packet->has_auth = 1;
    335 		/* Let it be knows that packet has DATA in it */
    336 		packet->has_data = 1;
    337 		/* timestamp the chunk for rtx purposes */
    338 		chunk->sent_at = jiffies;
    339 		/* Mainly used for prsctp RTX policy */
    340 		chunk->sent_count++;
    341 		break;
    342 	case SCTP_CID_COOKIE_ECHO:
    343 		packet->has_cookie_echo = 1;
    344 		break;
    345 
    346 	case SCTP_CID_SACK:
    347 		packet->has_sack = 1;
    348 		if (chunk->asoc)
    349 			chunk->asoc->stats.osacks++;
    350 		break;
    351 
    352 	case SCTP_CID_AUTH:
    353 		packet->has_auth = 1;
    354 		packet->auth = chunk;
    355 		break;
    356 	}
    357 
    358 	/* It is OK to send this chunk.  */
    359 	list_add_tail(&chunk->list, &packet->chunk_list);
    360 	packet->size += chunk_len;
    361 	chunk->transport = packet->transport;
    362 finish:
    363 	return retval;
    364 }
    365 
    366 /* Append a chunk to the offered packet reporting back any inability to do
    367  * so.
    368  */
    369 enum sctp_xmit sctp_packet_append_chunk(struct sctp_packet *packet,
    370 					struct sctp_chunk *chunk)
    371 {
    372 	enum sctp_xmit retval = SCTP_XMIT_OK;
    373 
    374 	pr_debug("%s: packet:%p chunk:%p\n", __func__, packet, chunk);
    375 
    376 	/* Data chunks are special.  Before seeing what else we can
    377 	 * bundle into this packet, check to see if we are allowed to
    378 	 * send this DATA.
    379 	 */
    380 	if (sctp_chunk_is_data(chunk)) {
    381 		retval = sctp_packet_can_append_data(packet, chunk);
    382 		if (retval != SCTP_XMIT_OK)
    383 			goto finish;
    384 	}
    385 
    386 	/* Try to bundle AUTH chunk */
    387 	retval = sctp_packet_bundle_auth(packet, chunk);
    388 	if (retval != SCTP_XMIT_OK)
    389 		goto finish;
    390 
    391 	/* Try to bundle SACK chunk */
    392 	retval = sctp_packet_bundle_sack(packet, chunk);
    393 	if (retval != SCTP_XMIT_OK)
    394 		goto finish;
    395 
    396 	retval = __sctp_packet_append_chunk(packet, chunk);
    397 
    398 finish:
    399 	return retval;
    400 }
    401 
    402 static void sctp_packet_gso_append(struct sk_buff *head, struct sk_buff *skb)
    403 {
    404 	if (SCTP_OUTPUT_CB(head)->last == head)
    405 		skb_shinfo(head)->frag_list = skb;
    406 	else
    407 		SCTP_OUTPUT_CB(head)->last->next = skb;
    408 	SCTP_OUTPUT_CB(head)->last = skb;
    409 
    410 	head->truesize += skb->truesize;
    411 	head->data_len += skb->len;
    412 	head->len += skb->len;
    413 	refcount_add(skb->truesize, &head->sk->sk_wmem_alloc);
    414 
    415 	__skb_header_release(skb);
    416 }
    417 
    418 static int sctp_packet_pack(struct sctp_packet *packet,
    419 			    struct sk_buff *head, int gso, gfp_t gfp)
    420 {
    421 	struct sctp_transport *tp = packet->transport;
    422 	struct sctp_auth_chunk *auth = NULL;
    423 	struct sctp_chunk *chunk, *tmp;
    424 	int pkt_count = 0, pkt_size;
    425 	struct sock *sk = head->sk;
    426 	struct sk_buff *nskb;
    427 	int auth_len = 0;
    428 
    429 	if (gso) {
    430 		skb_shinfo(head)->gso_type = sk->sk_gso_type;
    431 		SCTP_OUTPUT_CB(head)->last = head;
    432 	} else {
    433 		nskb = head;
    434 		pkt_size = packet->size;
    435 		goto merge;
    436 	}
    437 
    438 	do {
    439 		/* calculate the pkt_size and alloc nskb */
    440 		pkt_size = packet->overhead;
    441 		list_for_each_entry_safe(chunk, tmp, &packet->chunk_list,
    442 					 list) {
    443 			int padded = SCTP_PAD4(chunk->skb->len);
    444 
    445 			if (chunk == packet->auth)
    446 				auth_len = padded;
    447 			else if (auth_len + padded + packet->overhead >
    448 				 tp->pathmtu)
    449 				return 0;
    450 			else if (pkt_size + padded > tp->pathmtu)
    451 				break;
    452 			pkt_size += padded;
    453 		}
    454 		nskb = alloc_skb(pkt_size + MAX_HEADER, gfp);
    455 		if (!nskb)
    456 			return 0;
    457 		skb_reserve(nskb, packet->overhead + MAX_HEADER);
    458 
    459 merge:
    460 		/* merge chunks into nskb and append nskb into head list */
    461 		pkt_size -= packet->overhead;
    462 		list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
    463 			int padding;
    464 
    465 			list_del_init(&chunk->list);
    466 			if (sctp_chunk_is_data(chunk)) {
    467 				if (!sctp_chunk_retransmitted(chunk) &&
    468 				    !tp->rto_pending) {
    469 					chunk->rtt_in_progress = 1;
    470 					tp->rto_pending = 1;
    471 				}
    472 			}
    473 
    474 			padding = SCTP_PAD4(chunk->skb->len) - chunk->skb->len;
    475 			if (padding)
    476 				skb_put_zero(chunk->skb, padding);
    477 
    478 			if (chunk == packet->auth)
    479 				auth = (struct sctp_auth_chunk *)
    480 							skb_tail_pointer(nskb);
    481 
    482 			skb_put_data(nskb, chunk->skb->data, chunk->skb->len);
    483 
    484 			pr_debug("*** Chunk:%p[%s] %s 0x%x, length:%d, chunk->skb->len:%d, rtt_in_progress:%d\n",
    485 				 chunk,
    486 				 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)),
    487 				 chunk->has_tsn ? "TSN" : "No TSN",
    488 				 chunk->has_tsn ? ntohl(chunk->subh.data_hdr->tsn) : 0,
    489 				 ntohs(chunk->chunk_hdr->length), chunk->skb->len,
    490 				 chunk->rtt_in_progress);
    491 
    492 			pkt_size -= SCTP_PAD4(chunk->skb->len);
    493 
    494 			if (!sctp_chunk_is_data(chunk) && chunk != packet->auth)
    495 				sctp_chunk_free(chunk);
    496 
    497 			if (!pkt_size)
    498 				break;
    499 		}
    500 
    501 		if (auth) {
    502 			sctp_auth_calculate_hmac(tp->asoc, nskb, auth,
    503 						 packet->auth->shkey, gfp);
    504 			/* free auth if no more chunks, or add it back */
    505 			if (list_empty(&packet->chunk_list))
    506 				sctp_chunk_free(packet->auth);
    507 			else
    508 				list_add(&packet->auth->list,
    509 					 &packet->chunk_list);
    510 		}
    511 
    512 		if (gso)
    513 			sctp_packet_gso_append(head, nskb);
    514 
    515 		pkt_count++;
    516 	} while (!list_empty(&packet->chunk_list));
    517 
    518 	if (gso) {
    519 		memset(head->cb, 0, max(sizeof(struct inet_skb_parm),
    520 					sizeof(struct inet6_skb_parm)));
    521 		skb_shinfo(head)->gso_segs = pkt_count;
    522 		skb_shinfo(head)->gso_size = GSO_BY_FRAGS;
    523 		rcu_read_lock();
    524 		if (skb_dst(head) != tp->dst) {
    525 			dst_hold(tp->dst);
    526 			sk_setup_caps(sk, tp->dst);
    527 		}
    528 		rcu_read_unlock();
    529 		goto chksum;
    530 	}
    531 
    532 	if (sctp_checksum_disable)
    533 		return 1;
    534 
    535 	if (!(skb_dst(head)->dev->features & NETIF_F_SCTP_CRC) ||
    536 	    dst_xfrm(skb_dst(head)) || packet->ipfragok) {
    537 		struct sctphdr *sh =
    538 			(struct sctphdr *)skb_transport_header(head);
    539 
    540 		sh->checksum = sctp_compute_cksum(head, 0);
    541 	} else {
    542 chksum:
    543 		head->ip_summed = CHECKSUM_PARTIAL;
    544 		head->csum_not_inet = 1;
    545 		head->csum_start = skb_transport_header(head) - head->head;
    546 		head->csum_offset = offsetof(struct sctphdr, checksum);
    547 	}
    548 
    549 	return pkt_count;
    550 }
    551 
    552 /* All packets are sent to the network through this function from
    553  * sctp_outq_tail().
    554  *
    555  * The return value is always 0 for now.
    556  */
    557 int sctp_packet_transmit(struct sctp_packet *packet, gfp_t gfp)
    558 {
    559 	struct sctp_transport *tp = packet->transport;
    560 	struct sctp_association *asoc = tp->asoc;
    561 	struct sctp_chunk *chunk, *tmp;
    562 	int pkt_count, gso = 0;
    563 	struct dst_entry *dst;
    564 	struct sk_buff *head;
    565 	struct sctphdr *sh;
    566 	struct sock *sk;
    567 
    568 	pr_debug("%s: packet:%p\n", __func__, packet);
    569 	if (list_empty(&packet->chunk_list))
    570 		return 0;
    571 	chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
    572 	sk = chunk->skb->sk;
    573 
    574 	/* check gso */
    575 	if (packet->size > tp->pathmtu && !packet->ipfragok) {
    576 		if (!sk_can_gso(sk)) {
    577 			pr_err_once("Trying to GSO but underlying device doesn't support it.");
    578 			goto out;
    579 		}
    580 		gso = 1;
    581 	}
    582 
    583 	/* alloc head skb */
    584 	head = alloc_skb((gso ? packet->overhead : packet->size) +
    585 			 MAX_HEADER, gfp);
    586 	if (!head)
    587 		goto out;
    588 	skb_reserve(head, packet->overhead + MAX_HEADER);
    589 	skb_set_owner_w(head, sk);
    590 
    591 	/* set sctp header */
    592 	sh = skb_push(head, sizeof(struct sctphdr));
    593 	skb_reset_transport_header(head);
    594 	sh->source = htons(packet->source_port);
    595 	sh->dest = htons(packet->destination_port);
    596 	sh->vtag = htonl(packet->vtag);
    597 	sh->checksum = 0;
    598 
    599 	/* drop packet if no dst */
    600 	dst = dst_clone(tp->dst);
    601 	if (!dst) {
    602 		IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
    603 		kfree_skb(head);
    604 		goto out;
    605 	}
    606 	skb_dst_set(head, dst);
    607 
    608 	/* pack up chunks */
    609 	pkt_count = sctp_packet_pack(packet, head, gso, gfp);
    610 	if (!pkt_count) {
    611 		kfree_skb(head);
    612 		goto out;
    613 	}
    614 	pr_debug("***sctp_transmit_packet*** skb->len:%d\n", head->len);
    615 
    616 	/* start autoclose timer */
    617 	if (packet->has_data && sctp_state(asoc, ESTABLISHED) &&
    618 	    asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]) {
    619 		struct timer_list *timer =
    620 			&asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
    621 		unsigned long timeout =
    622 			asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
    623 
    624 		if (!mod_timer(timer, jiffies + timeout))
    625 			sctp_association_hold(asoc);
    626 	}
    627 
    628 	/* sctp xmit */
    629 	tp->af_specific->ecn_capable(sk);
    630 	if (asoc) {
    631 		asoc->stats.opackets += pkt_count;
    632 		if (asoc->peer.last_sent_to != tp)
    633 			asoc->peer.last_sent_to = tp;
    634 	}
    635 	head->ignore_df = packet->ipfragok;
    636 	if (tp->dst_pending_confirm)
    637 		skb_set_dst_pending_confirm(head, 1);
    638 	/* neighbour should be confirmed on successful transmission or
    639 	 * positive error
    640 	 */
    641 	if (tp->af_specific->sctp_xmit(head, tp) >= 0 &&
    642 	    tp->dst_pending_confirm)
    643 		tp->dst_pending_confirm = 0;
    644 
    645 out:
    646 	list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
    647 		list_del_init(&chunk->list);
    648 		if (!sctp_chunk_is_data(chunk))
    649 			sctp_chunk_free(chunk);
    650 	}
    651 	sctp_packet_reset(packet);
    652 	return 0;
    653 }
    654 
    655 /********************************************************************
    656  * 2nd Level Abstractions
    657  ********************************************************************/
    658 
    659 /* This private function check to see if a chunk can be added */
    660 static enum sctp_xmit sctp_packet_can_append_data(struct sctp_packet *packet,
    661 						  struct sctp_chunk *chunk)
    662 {
    663 	size_t datasize, rwnd, inflight, flight_size;
    664 	struct sctp_transport *transport = packet->transport;
    665 	struct sctp_association *asoc = transport->asoc;
    666 	struct sctp_outq *q = &asoc->outqueue;
    667 
    668 	/* RFC 2960 6.1  Transmission of DATA Chunks
    669 	 *
    670 	 * A) At any given time, the data sender MUST NOT transmit new data to
    671 	 * any destination transport address if its peer's rwnd indicates
    672 	 * that the peer has no buffer space (i.e. rwnd is 0, see Section
    673 	 * 6.2.1).  However, regardless of the value of rwnd (including if it
    674 	 * is 0), the data sender can always have one DATA chunk in flight to
    675 	 * the receiver if allowed by cwnd (see rule B below).  This rule
    676 	 * allows the sender to probe for a change in rwnd that the sender
    677 	 * missed due to the SACK having been lost in transit from the data
    678 	 * receiver to the data sender.
    679 	 */
    680 
    681 	rwnd = asoc->peer.rwnd;
    682 	inflight = q->outstanding_bytes;
    683 	flight_size = transport->flight_size;
    684 
    685 	datasize = sctp_data_size(chunk);
    686 
    687 	if (datasize > rwnd && inflight > 0)
    688 		/* We have (at least) one data chunk in flight,
    689 		 * so we can't fall back to rule 6.1 B).
    690 		 */
    691 		return SCTP_XMIT_RWND_FULL;
    692 
    693 	/* RFC 2960 6.1  Transmission of DATA Chunks
    694 	 *
    695 	 * B) At any given time, the sender MUST NOT transmit new data
    696 	 * to a given transport address if it has cwnd or more bytes
    697 	 * of data outstanding to that transport address.
    698 	 */
    699 	/* RFC 7.2.4 & the Implementers Guide 2.8.
    700 	 *
    701 	 * 3) ...
    702 	 *    When a Fast Retransmit is being performed the sender SHOULD
    703 	 *    ignore the value of cwnd and SHOULD NOT delay retransmission.
    704 	 */
    705 	if (chunk->fast_retransmit != SCTP_NEED_FRTX &&
    706 	    flight_size >= transport->cwnd)
    707 		return SCTP_XMIT_RWND_FULL;
    708 
    709 	/* Nagle's algorithm to solve small-packet problem:
    710 	 * Inhibit the sending of new chunks when new outgoing data arrives
    711 	 * if any previously transmitted data on the connection remains
    712 	 * unacknowledged.
    713 	 */
    714 
    715 	if ((sctp_sk(asoc->base.sk)->nodelay || inflight == 0) &&
    716 	    !asoc->force_delay)
    717 		/* Nothing unacked */
    718 		return SCTP_XMIT_OK;
    719 
    720 	if (!sctp_packet_empty(packet))
    721 		/* Append to packet */
    722 		return SCTP_XMIT_OK;
    723 
    724 	if (!sctp_state(asoc, ESTABLISHED))
    725 		return SCTP_XMIT_OK;
    726 
    727 	/* Check whether this chunk and all the rest of pending data will fit
    728 	 * or delay in hopes of bundling a full sized packet.
    729 	 */
    730 	if (chunk->skb->len + q->out_qlen > transport->pathmtu -
    731 	    packet->overhead - sctp_datachk_len(&chunk->asoc->stream) - 4)
    732 		/* Enough data queued to fill a packet */
    733 		return SCTP_XMIT_OK;
    734 
    735 	/* Don't delay large message writes that may have been fragmented */
    736 	if (!chunk->msg->can_delay)
    737 		return SCTP_XMIT_OK;
    738 
    739 	/* Defer until all data acked or packet full */
    740 	return SCTP_XMIT_DELAY;
    741 }
    742 
    743 /* This private function does management things when adding DATA chunk */
    744 static void sctp_packet_append_data(struct sctp_packet *packet,
    745 				struct sctp_chunk *chunk)
    746 {
    747 	struct sctp_transport *transport = packet->transport;
    748 	size_t datasize = sctp_data_size(chunk);
    749 	struct sctp_association *asoc = transport->asoc;
    750 	u32 rwnd = asoc->peer.rwnd;
    751 
    752 	/* Keep track of how many bytes are in flight over this transport. */
    753 	transport->flight_size += datasize;
    754 
    755 	/* Keep track of how many bytes are in flight to the receiver. */
    756 	asoc->outqueue.outstanding_bytes += datasize;
    757 
    758 	/* Update our view of the receiver's rwnd. */
    759 	if (datasize < rwnd)
    760 		rwnd -= datasize;
    761 	else
    762 		rwnd = 0;
    763 
    764 	asoc->peer.rwnd = rwnd;
    765 	sctp_chunk_assign_tsn(chunk);
    766 	asoc->stream.si->assign_number(chunk);
    767 }
    768 
    769 static enum sctp_xmit sctp_packet_will_fit(struct sctp_packet *packet,
    770 					   struct sctp_chunk *chunk,
    771 					   u16 chunk_len)
    772 {
    773 	enum sctp_xmit retval = SCTP_XMIT_OK;
    774 	size_t psize, pmtu, maxsize;
    775 
    776 	/* Don't bundle in this packet if this chunk's auth key doesn't
    777 	 * match other chunks already enqueued on this packet. Also,
    778 	 * don't bundle the chunk with auth key if other chunks in this
    779 	 * packet don't have auth key.
    780 	 */
    781 	if ((packet->auth && chunk->shkey != packet->auth->shkey) ||
    782 	    (!packet->auth && chunk->shkey &&
    783 	     chunk->chunk_hdr->type != SCTP_CID_AUTH))
    784 		return SCTP_XMIT_PMTU_FULL;
    785 
    786 	psize = packet->size;
    787 	if (packet->transport->asoc)
    788 		pmtu = packet->transport->asoc->pathmtu;
    789 	else
    790 		pmtu = packet->transport->pathmtu;
    791 
    792 	/* Decide if we need to fragment or resubmit later. */
    793 	if (psize + chunk_len > pmtu) {
    794 		/* It's OK to fragment at IP level if any one of the following
    795 		 * is true:
    796 		 *	1. The packet is empty (meaning this chunk is greater
    797 		 *	   the MTU)
    798 		 *	2. The packet doesn't have any data in it yet and data
    799 		 *	   requires authentication.
    800 		 */
    801 		if (sctp_packet_empty(packet) ||
    802 		    (!packet->has_data && chunk->auth)) {
    803 			/* We no longer do re-fragmentation.
    804 			 * Just fragment at the IP layer, if we
    805 			 * actually hit this condition
    806 			 */
    807 			packet->ipfragok = 1;
    808 			goto out;
    809 		}
    810 
    811 		/* Similarly, if this chunk was built before a PMTU
    812 		 * reduction, we have to fragment it at IP level now. So
    813 		 * if the packet already contains something, we need to
    814 		 * flush.
    815 		 */
    816 		maxsize = pmtu - packet->overhead;
    817 		if (packet->auth)
    818 			maxsize -= SCTP_PAD4(packet->auth->skb->len);
    819 		if (chunk_len > maxsize)
    820 			retval = SCTP_XMIT_PMTU_FULL;
    821 
    822 		/* It is also okay to fragment if the chunk we are
    823 		 * adding is a control chunk, but only if current packet
    824 		 * is not a GSO one otherwise it causes fragmentation of
    825 		 * a large frame. So in this case we allow the
    826 		 * fragmentation by forcing it to be in a new packet.
    827 		 */
    828 		if (!sctp_chunk_is_data(chunk) && packet->has_data)
    829 			retval = SCTP_XMIT_PMTU_FULL;
    830 
    831 		if (psize + chunk_len > packet->max_size)
    832 			/* Hit GSO/PMTU limit, gotta flush */
    833 			retval = SCTP_XMIT_PMTU_FULL;
    834 
    835 		if (!packet->transport->burst_limited &&
    836 		    psize + chunk_len > (packet->transport->cwnd >> 1))
    837 			/* Do not allow a single GSO packet to use more
    838 			 * than half of cwnd.
    839 			 */
    840 			retval = SCTP_XMIT_PMTU_FULL;
    841 
    842 		if (packet->transport->burst_limited &&
    843 		    psize + chunk_len > (packet->transport->burst_limited >> 1))
    844 			/* Do not allow a single GSO packet to use more
    845 			 * than half of original cwnd.
    846 			 */
    847 			retval = SCTP_XMIT_PMTU_FULL;
    848 		/* Otherwise it will fit in the GSO packet */
    849 	}
    850 
    851 out:
    852 	return retval;
    853 }