Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 841 insertions, 0 deletions

diff --git a/net/sctp/output.c b/net/sctp/output.c
new file mode 100644
index 000000000..1441eaf46
--- /dev/null
+++ b/net/sctp/output.c
@@ -0,0 +1,841 @@
+// 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.
+ *
+ * This file is part of the SCTP kernel implementation
+ *
+ * These functions handle output processing.
+ *
+ * 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:
+ *    La Monte H.P. Yarroll <piggy@acm.org>
+ *    Karl Knutson          <karl@athena.chicago.il.us>
+ *    Jon Grimm             <jgrimm@austin.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/wait.h>
+#include <linux/time.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <net/inet_ecn.h>
+#include <net/ip.h>
+#include <net/icmp.h>
+#include <net/net_namespace.h>
+
+#include <linux/socket.h> /* for sa_family_t */
+#include <net/sock.h>
+
+#include <net/sctp/sctp.h>
+#include <net/sctp/sm.h>
+#include <net/sctp/checksum.h>
+
+/* Forward declarations for private helpers. */
+static enum sctp_xmit __sctp_packet_append_chunk(struct sctp_packet *packet,
+						 struct sctp_chunk *chunk);
+static enum sctp_xmit sctp_packet_can_append_data(struct sctp_packet *packet,
+						  struct sctp_chunk *chunk);
+static void sctp_packet_append_data(struct sctp_packet *packet,
+				    struct sctp_chunk *chunk);
+static enum sctp_xmit sctp_packet_will_fit(struct sctp_packet *packet,
+					   struct sctp_chunk *chunk,
+					   u16 chunk_len);
+
+static void sctp_packet_reset(struct sctp_packet *packet)
+{
+	/* sctp_packet_transmit() relies on this to reset size to the
+	 * current overhead after sending packets.
+	 */
+	packet->size = packet->overhead;
+
+	packet->has_cookie_echo = 0;
+	packet->has_sack = 0;
+	packet->has_data = 0;
+	packet->has_auth = 0;
+	packet->ipfragok = 0;
+	packet->auth = NULL;
+}
+
+/* Config a packet.
+ * This appears to be a followup set of initializations.
+ */
+void sctp_packet_config(struct sctp_packet *packet, __u32 vtag,
+			int ecn_capable)
+{
+	struct sctp_transport *tp = packet->transport;
+	struct sctp_association *asoc = tp->asoc;
+	struct sctp_sock *sp = NULL;
+	struct sock *sk;
+
+	pr_debug("%s: packet:%p vtag:0x%x\n", __func__, packet, vtag);
+	packet->vtag = vtag;
+
+	/* do the following jobs only once for a flush schedule */
+	if (!sctp_packet_empty(packet))
+		return;
+
+	/* set packet max_size with pathmtu, then calculate overhead */
+	packet->max_size = tp->pathmtu;
+
+	if (asoc) {
+		sk = asoc->base.sk;
+		sp = sctp_sk(sk);
+	}
+	packet->overhead = sctp_mtu_payload(sp, 0, 0);
+	packet->size = packet->overhead;
+
+	if (!asoc)
+		return;
+
+	/* update dst or transport pathmtu if in need */
+	if (!sctp_transport_dst_check(tp)) {
+		sctp_transport_route(tp, NULL, sp);
+		if (asoc->param_flags & SPP_PMTUD_ENABLE)
+			sctp_assoc_sync_pmtu(asoc);
+	} else if (!sctp_transport_pmtu_check(tp)) {
+		if (asoc->param_flags & SPP_PMTUD_ENABLE)
+			sctp_assoc_sync_pmtu(asoc);
+	}
+
+	if (asoc->pmtu_pending) {
+		if (asoc->param_flags & SPP_PMTUD_ENABLE)
+			sctp_assoc_sync_pmtu(asoc);
+		asoc->pmtu_pending = 0;
+	}
+
+	/* If there a is a prepend chunk stick it on the list before
+	 * any other chunks get appended.
+	 */
+	if (ecn_capable) {
+		struct sctp_chunk *chunk = sctp_get_ecne_prepend(asoc);
+
+		if (chunk)
+			sctp_packet_append_chunk(packet, chunk);
+	}
+
+	if (!tp->dst)
+		return;
+
+	/* set packet max_size with gso_max_size if gso is enabled*/
+	rcu_read_lock();
+	if (__sk_dst_get(sk) != tp->dst) {
+		dst_hold(tp->dst);
+		sk_setup_caps(sk, tp->dst);
+	}
+	packet->max_size = sk_can_gso(sk) ? tp->dst->dev->gso_max_size
+					  : asoc->pathmtu;
+	rcu_read_unlock();
+}
+
+/* Initialize the packet structure. */
+void sctp_packet_init(struct sctp_packet *packet,
+		      struct sctp_transport *transport,
+		      __u16 sport, __u16 dport)
+{
+	pr_debug("%s: packet:%p transport:%p\n", __func__, packet, transport);
+
+	packet->transport = transport;
+	packet->source_port = sport;
+	packet->destination_port = dport;
+	INIT_LIST_HEAD(&packet->chunk_list);
+	/* The overhead will be calculated by sctp_packet_config() */
+	packet->overhead = 0;
+	sctp_packet_reset(packet);
+	packet->vtag = 0;
+}
+
+/* Free a packet.  */
+void sctp_packet_free(struct sctp_packet *packet)
+{
+	struct sctp_chunk *chunk, *tmp;
+
+	pr_debug("%s: packet:%p\n", __func__, packet);
+
+	list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
+		list_del_init(&chunk->list);
+		sctp_chunk_free(chunk);
+	}
+}
+
+/* This routine tries to append the chunk to the offered packet. If adding
+ * the chunk causes the packet to exceed the path MTU and COOKIE_ECHO chunk
+ * is not present in the packet, it transmits the input packet.
+ * Data can be bundled with a packet containing a COOKIE_ECHO chunk as long
+ * as it can fit in the packet, but any more data that does not fit in this
+ * packet can be sent only after receiving the COOKIE_ACK.
+ */
+enum sctp_xmit sctp_packet_transmit_chunk(struct sctp_packet *packet,
+					  struct sctp_chunk *chunk,
+					  int one_packet, gfp_t gfp)
+{
+	enum sctp_xmit retval;
+
+	pr_debug("%s: packet:%p size:%zu chunk:%p size:%d\n", __func__,
+		 packet, packet->size, chunk, chunk->skb ? chunk->skb->len : -1);
+
+	switch ((retval = (sctp_packet_append_chunk(packet, chunk)))) {
+	case SCTP_XMIT_PMTU_FULL:
+		if (!packet->has_cookie_echo) {
+			int error = 0;
+
+			error = sctp_packet_transmit(packet, gfp);
+			if (error < 0)
+				chunk->skb->sk->sk_err = -error;
+
+			/* If we have an empty packet, then we can NOT ever
+			 * return PMTU_FULL.
+			 */
+			if (!one_packet)
+				retval = sctp_packet_append_chunk(packet,
+								  chunk);
+		}
+		break;
+
+	case SCTP_XMIT_RWND_FULL:
+	case SCTP_XMIT_OK:
+	case SCTP_XMIT_DELAY:
+		break;
+	}
+
+	return retval;
+}
+
+/* Try to bundle an auth chunk into the packet. */
+static enum sctp_xmit sctp_packet_bundle_auth(struct sctp_packet *pkt,
+					      struct sctp_chunk *chunk)
+{
+	struct sctp_association *asoc = pkt->transport->asoc;
+	enum sctp_xmit retval = SCTP_XMIT_OK;
+	struct sctp_chunk *auth;
+
+	/* if we don't have an association, we can't do authentication */
+	if (!asoc)
+		return retval;
+
+	/* See if this is an auth chunk we are bundling or if
+	 * auth is already bundled.
+	 */
+	if (chunk->chunk_hdr->type == SCTP_CID_AUTH || pkt->has_auth)
+		return retval;
+
+	/* if the peer did not request this chunk to be authenticated,
+	 * don't do it
+	 */
+	if (!chunk->auth)
+		return retval;
+
+	auth = sctp_make_auth(asoc, chunk->shkey->key_id);
+	if (!auth)
+		return retval;
+
+	auth->shkey = chunk->shkey;
+	sctp_auth_shkey_hold(auth->shkey);
+
+	retval = __sctp_packet_append_chunk(pkt, auth);
+
+	if (retval != SCTP_XMIT_OK)
+		sctp_chunk_free(auth);
+
+	return retval;
+}
+
+/* Try to bundle a SACK with the packet. */
+static enum sctp_xmit sctp_packet_bundle_sack(struct sctp_packet *pkt,
+					      struct sctp_chunk *chunk)
+{
+	enum sctp_xmit retval = SCTP_XMIT_OK;
+
+	/* If sending DATA and haven't aleady bundled a SACK, try to
+	 * bundle one in to the packet.
+	 */
+	if (sctp_chunk_is_data(chunk) && !pkt->has_sack &&
+	    !pkt->has_cookie_echo) {
+		struct sctp_association *asoc;
+		struct timer_list *timer;
+		asoc = pkt->transport->asoc;
+		timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
+
+		/* If the SACK timer is running, we have a pending SACK */
+		if (timer_pending(timer)) {
+			struct sctp_chunk *sack;
+
+			if (pkt->transport->sack_generation !=
+			    pkt->transport->asoc->peer.sack_generation)
+				return retval;
+
+			asoc->a_rwnd = asoc->rwnd;
+			sack = sctp_make_sack(asoc);
+			if (sack) {
+				retval = __sctp_packet_append_chunk(pkt, sack);
+				if (retval != SCTP_XMIT_OK) {
+					sctp_chunk_free(sack);
+					goto out;
+				}
+				SCTP_INC_STATS(asoc->base.net,
+					       SCTP_MIB_OUTCTRLCHUNKS);
+				asoc->stats.octrlchunks++;
+				asoc->peer.sack_needed = 0;
+				if (del_timer(timer))
+					sctp_association_put(asoc);
+			}
+		}
+	}
+out:
+	return retval;
+}
+
+
+/* Append a chunk to the offered packet reporting back any inability to do
+ * so.
+ */
+static enum sctp_xmit __sctp_packet_append_chunk(struct sctp_packet *packet,
+						 struct sctp_chunk *chunk)
+{
+	__u16 chunk_len = SCTP_PAD4(ntohs(chunk->chunk_hdr->length));
+	enum sctp_xmit retval = SCTP_XMIT_OK;
+
+	/* Check to see if this chunk will fit into the packet */
+	retval = sctp_packet_will_fit(packet, chunk, chunk_len);
+	if (retval != SCTP_XMIT_OK)
+		goto finish;
+
+	/* We believe that this chunk is OK to add to the packet */
+	switch (chunk->chunk_hdr->type) {
+	case SCTP_CID_DATA:
+	case SCTP_CID_I_DATA:
+		/* Account for the data being in the packet */
+		sctp_packet_append_data(packet, chunk);
+		/* Disallow SACK bundling after DATA. */
+		packet->has_sack = 1;
+		/* Disallow AUTH bundling after DATA */
+		packet->has_auth = 1;
+		/* Let it be knows that packet has DATA in it */
+		packet->has_data = 1;
+		/* timestamp the chunk for rtx purposes */
+		chunk->sent_at = jiffies;
+		/* Mainly used for prsctp RTX policy */
+		chunk->sent_count++;
+		break;
+	case SCTP_CID_COOKIE_ECHO:
+		packet->has_cookie_echo = 1;
+		break;
+
+	case SCTP_CID_SACK:
+		packet->has_sack = 1;
+		if (chunk->asoc)
+			chunk->asoc->stats.osacks++;
+		break;
+
+	case SCTP_CID_AUTH:
+		packet->has_auth = 1;
+		packet->auth = chunk;
+		break;
+	}
+
+	/* It is OK to send this chunk.  */
+	list_add_tail(&chunk->list, &packet->chunk_list);
+	packet->size += chunk_len;
+	chunk->transport = packet->transport;
+finish:
+	return retval;
+}
+
+/* Append a chunk to the offered packet reporting back any inability to do
+ * so.
+ */
+enum sctp_xmit sctp_packet_append_chunk(struct sctp_packet *packet,
+					struct sctp_chunk *chunk)
+{
+	enum sctp_xmit retval = SCTP_XMIT_OK;
+
+	pr_debug("%s: packet:%p chunk:%p\n", __func__, packet, chunk);
+
+	/* Data chunks are special.  Before seeing what else we can
+	 * bundle into this packet, check to see if we are allowed to
+	 * send this DATA.
+	 */
+	if (sctp_chunk_is_data(chunk)) {
+		retval = sctp_packet_can_append_data(packet, chunk);
+		if (retval != SCTP_XMIT_OK)
+			goto finish;
+	}
+
+	/* Try to bundle AUTH chunk */
+	retval = sctp_packet_bundle_auth(packet, chunk);
+	if (retval != SCTP_XMIT_OK)
+		goto finish;
+
+	/* Try to bundle SACK chunk */
+	retval = sctp_packet_bundle_sack(packet, chunk);
+	if (retval != SCTP_XMIT_OK)
+		goto finish;
+
+	retval = __sctp_packet_append_chunk(packet, chunk);
+
+finish:
+	return retval;
+}
+
+static void sctp_packet_gso_append(struct sk_buff *head, struct sk_buff *skb)
+{
+	if (SCTP_OUTPUT_CB(head)->last == head)
+		skb_shinfo(head)->frag_list = skb;
+	else
+		SCTP_OUTPUT_CB(head)->last->next = skb;
+	SCTP_OUTPUT_CB(head)->last = skb;
+
+	head->truesize += skb->truesize;
+	head->data_len += skb->len;
+	head->len += skb->len;
+	refcount_add(skb->truesize, &head->sk->sk_wmem_alloc);
+
+	__skb_header_release(skb);
+}
+
+static int sctp_packet_pack(struct sctp_packet *packet,
+			    struct sk_buff *head, int gso, gfp_t gfp)
+{
+	struct sctp_transport *tp = packet->transport;
+	struct sctp_auth_chunk *auth = NULL;
+	struct sctp_chunk *chunk, *tmp;
+	int pkt_count = 0, pkt_size;
+	struct sock *sk = head->sk;
+	struct sk_buff *nskb;
+	int auth_len = 0;
+
+	if (gso) {
+		skb_shinfo(head)->gso_type = sk->sk_gso_type;
+		SCTP_OUTPUT_CB(head)->last = head;
+	} else {
+		nskb = head;
+		pkt_size = packet->size;
+		goto merge;
+	}
+
+	do {
+		/* calculate the pkt_size and alloc nskb */
+		pkt_size = packet->overhead;
+		list_for_each_entry_safe(chunk, tmp, &packet->chunk_list,
+					 list) {
+			int padded = SCTP_PAD4(chunk->skb->len);
+
+			if (chunk == packet->auth)
+				auth_len = padded;
+			else if (auth_len + padded + packet->overhead >
+				 tp->pathmtu)
+				return 0;
+			else if (pkt_size + padded > tp->pathmtu)
+				break;
+			pkt_size += padded;
+		}
+		nskb = alloc_skb(pkt_size + MAX_HEADER, gfp);
+		if (!nskb)
+			return 0;
+		skb_reserve(nskb, packet->overhead + MAX_HEADER);
+
+merge:
+		/* merge chunks into nskb and append nskb into head list */
+		pkt_size -= packet->overhead;
+		list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
+			int padding;
+
+			list_del_init(&chunk->list);
+			if (sctp_chunk_is_data(chunk)) {
+				if (!sctp_chunk_retransmitted(chunk) &&
+				    !tp->rto_pending) {
+					chunk->rtt_in_progress = 1;
+					tp->rto_pending = 1;
+				}
+			}
+
+			padding = SCTP_PAD4(chunk->skb->len) - chunk->skb->len;
+			if (padding)
+				skb_put_zero(chunk->skb, padding);
+
+			if (chunk == packet->auth)
+				auth = (struct sctp_auth_chunk *)
+							skb_tail_pointer(nskb);
+
+			skb_put_data(nskb, chunk->skb->data, chunk->skb->len);
+
+			pr_debug("*** Chunk:%p[%s] %s 0x%x, length:%d, chunk->skb->len:%d, rtt_in_progress:%d\n",
+				 chunk,
+				 sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)),
+				 chunk->has_tsn ? "TSN" : "No TSN",
+				 chunk->has_tsn ? ntohl(chunk->subh.data_hdr->tsn) : 0,
+				 ntohs(chunk->chunk_hdr->length), chunk->skb->len,
+				 chunk->rtt_in_progress);
+
+			pkt_size -= SCTP_PAD4(chunk->skb->len);
+
+			if (!sctp_chunk_is_data(chunk) && chunk != packet->auth)
+				sctp_chunk_free(chunk);
+
+			if (!pkt_size)
+				break;
+		}
+
+		if (auth) {
+			sctp_auth_calculate_hmac(tp->asoc, nskb, auth,
+						 packet->auth->shkey, gfp);
+			/* free auth if no more chunks, or add it back */
+			if (list_empty(&packet->chunk_list))
+				sctp_chunk_free(packet->auth);
+			else
+				list_add(&packet->auth->list,
+					 &packet->chunk_list);
+		}
+
+		if (gso)
+			sctp_packet_gso_append(head, nskb);
+
+		pkt_count++;
+	} while (!list_empty(&packet->chunk_list));
+
+	if (gso) {
+		memset(head->cb, 0, max(sizeof(struct inet_skb_parm),
+					sizeof(struct inet6_skb_parm)));
+		skb_shinfo(head)->gso_segs = pkt_count;
+		skb_shinfo(head)->gso_size = GSO_BY_FRAGS;
+		rcu_read_lock();
+		if (skb_dst(head) != tp->dst) {
+			dst_hold(tp->dst);
+			sk_setup_caps(sk, tp->dst);
+		}
+		rcu_read_unlock();
+		goto chksum;
+	}
+
+	if (sctp_checksum_disable)
+		return 1;
+
+	if (!(skb_dst(head)->dev->features & NETIF_F_SCTP_CRC) ||
+	    dst_xfrm(skb_dst(head)) || packet->ipfragok) {
+		struct sctphdr *sh =
+			(struct sctphdr *)skb_transport_header(head);
+
+		sh->checksum = sctp_compute_cksum(head, 0);
+	} else {
+chksum:
+		head->ip_summed = CHECKSUM_PARTIAL;
+		head->csum_not_inet = 1;
+		head->csum_start = skb_transport_header(head) - head->head;
+		head->csum_offset = offsetof(struct sctphdr, checksum);
+	}
+
+	return pkt_count;
+}
+
+/* All packets are sent to the network through this function from
+ * sctp_outq_tail().
+ *
+ * The return value is always 0 for now.
+ */
+int sctp_packet_transmit(struct sctp_packet *packet, gfp_t gfp)
+{
+	struct sctp_transport *tp = packet->transport;
+	struct sctp_association *asoc = tp->asoc;
+	struct sctp_chunk *chunk, *tmp;
+	int pkt_count, gso = 0;
+	struct dst_entry *dst;
+	struct sk_buff *head;
+	struct sctphdr *sh;
+	struct sock *sk;
+
+	pr_debug("%s: packet:%p\n", __func__, packet);
+	if (list_empty(&packet->chunk_list))
+		return 0;
+	chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
+	sk = chunk->skb->sk;
+
+	/* check gso */
+	if (packet->size > tp->pathmtu && !packet->ipfragok) {
+		if (!sk_can_gso(sk)) {
+			pr_err_once("Trying to GSO but underlying device doesn't support it.");
+			goto out;
+		}
+		gso = 1;
+	}
+
+	/* alloc head skb */
+	head = alloc_skb((gso ? packet->overhead : packet->size) +
+			 MAX_HEADER, gfp);
+	if (!head)
+		goto out;
+	skb_reserve(head, packet->overhead + MAX_HEADER);
+	skb_set_owner_w(head, sk);
+
+	/* set sctp header */
+	sh = skb_push(head, sizeof(struct sctphdr));
+	skb_reset_transport_header(head);
+	sh->source = htons(packet->source_port);
+	sh->dest = htons(packet->destination_port);
+	sh->vtag = htonl(packet->vtag);
+	sh->checksum = 0;
+
+	/* drop packet if no dst */
+	dst = dst_clone(tp->dst);
+	if (!dst) {
+		IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
+		kfree_skb(head);
+		goto out;
+	}
+	skb_dst_set(head, dst);
+
+	/* pack up chunks */
+	pkt_count = sctp_packet_pack(packet, head, gso, gfp);
+	if (!pkt_count) {
+		kfree_skb(head);
+		goto out;
+	}
+	pr_debug("***sctp_transmit_packet*** skb->len:%d\n", head->len);
+
+	/* start autoclose timer */
+	if (packet->has_data && sctp_state(asoc, ESTABLISHED) &&
+	    asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]) {
+		struct timer_list *timer =
+			&asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
+		unsigned long timeout =
+			asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
+
+		if (!mod_timer(timer, jiffies + timeout))
+			sctp_association_hold(asoc);
+	}
+
+	/* sctp xmit */
+	tp->af_specific->ecn_capable(sk);
+	if (asoc) {
+		asoc->stats.opackets += pkt_count;
+		if (asoc->peer.last_sent_to != tp)
+			asoc->peer.last_sent_to = tp;
+	}
+	head->ignore_df = packet->ipfragok;
+	if (tp->dst_pending_confirm)
+		skb_set_dst_pending_confirm(head, 1);
+	/* neighbour should be confirmed on successful transmission or
+	 * positive error
+	 */
+	if (tp->af_specific->sctp_xmit(head, tp) >= 0 &&
+	    tp->dst_pending_confirm)
+		tp->dst_pending_confirm = 0;
+
+out:
+	list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
+		list_del_init(&chunk->list);
+		if (!sctp_chunk_is_data(chunk))
+			sctp_chunk_free(chunk);
+	}
+	sctp_packet_reset(packet);
+	return 0;
+}
+
+/********************************************************************
+ * 2nd Level Abstractions
+ ********************************************************************/
+
+/* This private function check to see if a chunk can be added */
+static enum sctp_xmit sctp_packet_can_append_data(struct sctp_packet *packet,
+						  struct sctp_chunk *chunk)
+{
+	size_t datasize, rwnd, inflight, flight_size;
+	struct sctp_transport *transport = packet->transport;
+	struct sctp_association *asoc = transport->asoc;
+	struct sctp_outq *q = &asoc->outqueue;
+
+	/* RFC 2960 6.1  Transmission of DATA Chunks
+	 *
+	 * A) At any given time, the data sender MUST NOT transmit new data to
+	 * any destination transport address if its peer's rwnd indicates
+	 * that the peer has no buffer space (i.e. rwnd is 0, see Section
+	 * 6.2.1).  However, regardless of the value of rwnd (including if it
+	 * is 0), the data sender can always have one DATA chunk in flight to
+	 * the receiver if allowed by cwnd (see rule B below).  This rule
+	 * allows the sender to probe for a change in rwnd that the sender
+	 * missed due to the SACK having been lost in transit from the data
+	 * receiver to the data sender.
+	 */
+
+	rwnd = asoc->peer.rwnd;
+	inflight = q->outstanding_bytes;
+	flight_size = transport->flight_size;
+
+	datasize = sctp_data_size(chunk);
+
+	if (datasize > rwnd && inflight > 0)
+		/* We have (at least) one data chunk in flight,
+		 * so we can't fall back to rule 6.1 B).
+		 */
+		return SCTP_XMIT_RWND_FULL;
+
+	/* RFC 2960 6.1  Transmission of DATA Chunks
+	 *
+	 * B) At any given time, the sender MUST NOT transmit new data
+	 * to a given transport address if it has cwnd or more bytes
+	 * of data outstanding to that transport address.
+	 */
+	/* RFC 7.2.4 & the Implementers Guide 2.8.
+	 *
+	 * 3) ...
+	 *    When a Fast Retransmit is being performed the sender SHOULD
+	 *    ignore the value of cwnd and SHOULD NOT delay retransmission.
+	 */
+	if (chunk->fast_retransmit != SCTP_NEED_FRTX &&
+	    flight_size >= transport->cwnd)
+		return SCTP_XMIT_RWND_FULL;
+
+	/* Nagle's algorithm to solve small-packet problem:
+	 * Inhibit the sending of new chunks when new outgoing data arrives
+	 * if any previously transmitted data on the connection remains
+	 * unacknowledged.
+	 */
+
+	if ((sctp_sk(asoc->base.sk)->nodelay || inflight == 0) &&
+	    !asoc->force_delay)
+		/* Nothing unacked */
+		return SCTP_XMIT_OK;
+
+	if (!sctp_packet_empty(packet))
+		/* Append to packet */
+		return SCTP_XMIT_OK;
+
+	if (!sctp_state(asoc, ESTABLISHED))
+		return SCTP_XMIT_OK;
+
+	/* Check whether this chunk and all the rest of pending data will fit
+	 * or delay in hopes of bundling a full sized packet.
+	 */
+	if (chunk->skb->len + q->out_qlen > transport->pathmtu -
+	    packet->overhead - sctp_datachk_len(&chunk->asoc->stream) - 4)
+		/* Enough data queued to fill a packet */
+		return SCTP_XMIT_OK;
+
+	/* Don't delay large message writes that may have been fragmented */
+	if (!chunk->msg->can_delay)
+		return SCTP_XMIT_OK;
+
+	/* Defer until all data acked or packet full */
+	return SCTP_XMIT_DELAY;
+}
+
+/* This private function does management things when adding DATA chunk */
+static void sctp_packet_append_data(struct sctp_packet *packet,
+				struct sctp_chunk *chunk)
+{
+	struct sctp_transport *transport = packet->transport;
+	size_t datasize = sctp_data_size(chunk);
+	struct sctp_association *asoc = transport->asoc;
+	u32 rwnd = asoc->peer.rwnd;
+
+	/* Keep track of how many bytes are in flight over this transport. */
+	transport->flight_size += datasize;
+
+	/* Keep track of how many bytes are in flight to the receiver. */
+	asoc->outqueue.outstanding_bytes += datasize;
+
+	/* Update our view of the receiver's rwnd. */
+	if (datasize < rwnd)
+		rwnd -= datasize;
+	else
+		rwnd = 0;
+
+	asoc->peer.rwnd = rwnd;
+	sctp_chunk_assign_tsn(chunk);
+	asoc->stream.si->assign_number(chunk);
+}
+
+static enum sctp_xmit sctp_packet_will_fit(struct sctp_packet *packet,
+					   struct sctp_chunk *chunk,
+					   u16 chunk_len)
+{
+	enum sctp_xmit retval = SCTP_XMIT_OK;
+	size_t psize, pmtu, maxsize;
+
+	/* Don't bundle in this packet if this chunk's auth key doesn't
+	 * match other chunks already enqueued on this packet. Also,
+	 * don't bundle the chunk with auth key if other chunks in this
+	 * packet don't have auth key.
+	 */
+	if ((packet->auth && chunk->shkey != packet->auth->shkey) ||
+	    (!packet->auth && chunk->shkey &&
+	     chunk->chunk_hdr->type != SCTP_CID_AUTH))
+		return SCTP_XMIT_PMTU_FULL;
+
+	psize = packet->size;
+	if (packet->transport->asoc)
+		pmtu = packet->transport->asoc->pathmtu;
+	else
+		pmtu = packet->transport->pathmtu;
+
+	/* Decide if we need to fragment or resubmit later. */
+	if (psize + chunk_len > pmtu) {
+		/* It's OK to fragment at IP level if any one of the following
+		 * is true:
+		 *	1. The packet is empty (meaning this chunk is greater
+		 *	   the MTU)
+		 *	2. The packet doesn't have any data in it yet and data
+		 *	   requires authentication.
+		 */
+		if (sctp_packet_empty(packet) ||
+		    (!packet->has_data && chunk->auth)) {
+			/* We no longer do re-fragmentation.
+			 * Just fragment at the IP layer, if we
+			 * actually hit this condition
+			 */
+			packet->ipfragok = 1;
+			goto out;
+		}
+
+		/* Similarly, if this chunk was built before a PMTU
+		 * reduction, we have to fragment it at IP level now. So
+		 * if the packet already contains something, we need to
+		 * flush.
+		 */
+		maxsize = pmtu - packet->overhead;
+		if (packet->auth)
+			maxsize -= SCTP_PAD4(packet->auth->skb->len);
+		if (chunk_len > maxsize)
+			retval = SCTP_XMIT_PMTU_FULL;
+
+		/* It is also okay to fragment if the chunk we are
+		 * adding is a control chunk, but only if current packet
+		 * is not a GSO one otherwise it causes fragmentation of
+		 * a large frame. So in this case we allow the
+		 * fragmentation by forcing it to be in a new packet.
+		 */
+		if (!sctp_chunk_is_data(chunk) && packet->has_data)
+			retval = SCTP_XMIT_PMTU_FULL;
+
+		if (psize + chunk_len > packet->max_size)
+			/* Hit GSO/PMTU limit, gotta flush */
+			retval = SCTP_XMIT_PMTU_FULL;
+
+		if (!packet->transport->burst_limited &&
+		    psize + chunk_len > (packet->transport->cwnd >> 1))
+			/* Do not allow a single GSO packet to use more
+			 * than half of cwnd.
+			 */
+			retval = SCTP_XMIT_PMTU_FULL;
+
+		if (packet->transport->burst_limited &&
+		    psize + chunk_len > (packet->transport->burst_limited >> 1))
+			/* Do not allow a single GSO packet to use more
+			 * than half of original cwnd.
+			 */
+			retval = SCTP_XMIT_PMTU_FULL;
+		/* Otherwise it will fit in the GSO packet */
+	}
+
+out:
+	return retval;
+}