linux/net/sctp/output.c
Xin Long ecc515d723 sctp: fix the panic caused by route update
Commit 7303a14750 ("sctp: identify chunks that need to be fragmented
at IP level") made the chunk be fragmented at IP level in the next round
if it's size exceed PMTU.

But there still is another case, PMTU can be updated if transport's dst
expires and transport's pmtu_pending is set in sctp_packet_transmit. If
the new PMTU is less than the chunk, the same issue with that commit can
be triggered.

So we should drop this packet and let it retransmit in another round
where it would be fragmented at IP level.

This patch is to fix it by checking the chunk size after PMTU may be
updated and dropping this packet if it's size exceed PMTU.

Fixes: 90017accff ("sctp: Add GSO support")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Neil Horman <nhorman@txudriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-10-26 17:32:19 -04:00

956 lines
27 KiB
C

/* 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.
*
* 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:
* 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 sctp_xmit_t __sctp_packet_append_chunk(struct sctp_packet *packet,
struct sctp_chunk *chunk);
static sctp_xmit_t 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 sctp_xmit_t sctp_packet_will_fit(struct sctp_packet *packet,
struct sctp_chunk *chunk,
u16 chunk_len);
static void sctp_packet_reset(struct sctp_packet *packet)
{
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.
*/
struct sctp_packet *sctp_packet_config(struct sctp_packet *packet,
__u32 vtag, int ecn_capable)
{
struct sctp_transport *tp = packet->transport;
struct sctp_association *asoc = tp->asoc;
pr_debug("%s: packet:%p vtag:0x%x\n", __func__, packet, vtag);
packet->vtag = vtag;
if (asoc && tp->dst) {
struct sock *sk = asoc->base.sk;
rcu_read_lock();
if (__sk_dst_get(sk) != tp->dst) {
dst_hold(tp->dst);
sk_setup_caps(sk, tp->dst);
}
if (sk_can_gso(sk)) {
struct net_device *dev = tp->dst->dev;
packet->max_size = dev->gso_max_size;
} else {
packet->max_size = asoc->pathmtu;
}
rcu_read_unlock();
} else {
packet->max_size = tp->pathmtu;
}
if (ecn_capable && sctp_packet_empty(packet)) {
struct sctp_chunk *chunk;
/* If there a is a prepend chunk stick it on the list before
* any other chunks get appended.
*/
chunk = sctp_get_ecne_prepend(asoc);
if (chunk)
sctp_packet_append_chunk(packet, chunk);
}
return packet;
}
/* Initialize the packet structure. */
struct sctp_packet *sctp_packet_init(struct sctp_packet *packet,
struct sctp_transport *transport,
__u16 sport, __u16 dport)
{
struct sctp_association *asoc = transport->asoc;
size_t overhead;
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);
if (asoc) {
struct sctp_sock *sp = sctp_sk(asoc->base.sk);
overhead = sp->pf->af->net_header_len;
} else {
overhead = sizeof(struct ipv6hdr);
}
overhead += sizeof(struct sctphdr);
packet->overhead = overhead;
sctp_packet_reset(packet);
packet->vtag = 0;
return packet;
}
/* 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.
*/
sctp_xmit_t sctp_packet_transmit_chunk(struct sctp_packet *packet,
struct sctp_chunk *chunk,
int one_packet, gfp_t gfp)
{
sctp_xmit_t 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 sctp_xmit_t sctp_packet_bundle_auth(struct sctp_packet *pkt,
struct sctp_chunk *chunk)
{
struct sctp_association *asoc = pkt->transport->asoc;
struct sctp_chunk *auth;
sctp_xmit_t retval = SCTP_XMIT_OK;
/* 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);
if (!auth)
return retval;
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 sctp_xmit_t sctp_packet_bundle_sack(struct sctp_packet *pkt,
struct sctp_chunk *chunk)
{
sctp_xmit_t 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;
}
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 sctp_xmit_t __sctp_packet_append_chunk(struct sctp_packet *packet,
struct sctp_chunk *chunk)
{
sctp_xmit_t retval = SCTP_XMIT_OK;
__u16 chunk_len = SCTP_PAD4(ntohs(chunk->chunk_hdr->length));
/* 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:
/* 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.
*/
sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet,
struct sctp_chunk *chunk)
{
sctp_xmit_t 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_release_owner(struct sk_buff *skb)
{
sk_free(skb->sk);
}
static void sctp_packet_set_owner_w(struct sk_buff *skb, struct sock *sk)
{
skb_orphan(skb);
skb->sk = sk;
skb->destructor = sctp_packet_release_owner;
/*
* The data chunks have already been accounted for in sctp_sendmsg(),
* therefore only reserve a single byte to keep socket around until
* the packet has been transmitted.
*/
atomic_inc(&sk->sk_wmem_alloc);
}
/* All packets are sent to the network through this function from
* sctp_outq_tail().
*
* The return value is a normal kernel error return value.
*/
int sctp_packet_transmit(struct sctp_packet *packet, gfp_t gfp)
{
struct sctp_transport *tp = packet->transport;
struct sctp_association *asoc = tp->asoc;
struct sctphdr *sh;
struct sk_buff *nskb = NULL, *head = NULL;
struct sctp_chunk *chunk, *tmp;
struct sock *sk;
int err = 0;
int padding; /* How much padding do we need? */
int pkt_size;
__u8 has_data = 0;
int gso = 0;
int pktcount = 0;
int auth_len = 0;
struct dst_entry *dst;
unsigned char *auth = NULL; /* pointer to auth in skb data */
pr_debug("%s: packet:%p\n", __func__, packet);
/* Do NOT generate a chunkless packet. */
if (list_empty(&packet->chunk_list))
return err;
/* Set up convenience variables... */
chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
sk = chunk->skb->sk;
/* Allocate the head skb, or main one if not in GSO */
if (packet->size > tp->pathmtu && !packet->ipfragok) {
if (sk_can_gso(sk)) {
gso = 1;
pkt_size = packet->overhead;
} else {
/* If this happens, we trash this packet and try
* to build a new one, hopefully correct this
* time. Application may notice this error.
*/
pr_err_once("Trying to GSO but underlying device doesn't support it.");
goto err;
}
} else {
pkt_size = packet->size;
}
head = alloc_skb(pkt_size + MAX_HEADER, gfp);
if (!head)
goto err;
if (gso) {
NAPI_GRO_CB(head)->last = head;
skb_shinfo(head)->gso_type = sk->sk_gso_type;
}
/* Make sure the outbound skb has enough header room reserved. */
skb_reserve(head, packet->overhead + MAX_HEADER);
/* Set the owning socket so that we know where to get the
* destination IP address.
*/
sctp_packet_set_owner_w(head, sk);
if (!sctp_transport_dst_check(tp)) {
sctp_transport_route(tp, NULL, sctp_sk(sk));
if (asoc && (asoc->param_flags & SPP_PMTUD_ENABLE)) {
sctp_assoc_sync_pmtu(sk, asoc);
}
}
dst = dst_clone(tp->dst);
if (!dst) {
if (asoc)
IP_INC_STATS(sock_net(asoc->base.sk),
IPSTATS_MIB_OUTNOROUTES);
goto nodst;
}
skb_dst_set(head, dst);
/* Build the SCTP header. */
sh = (struct sctphdr *)skb_push(head, sizeof(struct sctphdr));
skb_reset_transport_header(head);
sh->source = htons(packet->source_port);
sh->dest = htons(packet->destination_port);
/* From 6.8 Adler-32 Checksum Calculation:
* After the packet is constructed (containing the SCTP common
* header and one or more control or DATA chunks), the
* transmitter shall:
*
* 1) Fill in the proper Verification Tag in the SCTP common
* header and initialize the checksum field to 0's.
*/
sh->vtag = htonl(packet->vtag);
sh->checksum = 0;
pr_debug("***sctp_transmit_packet***\n");
do {
/* Set up convenience variables... */
chunk = list_entry(packet->chunk_list.next, struct sctp_chunk, list);
pktcount++;
/* Calculate packet size, so it fits in PMTU. Leave
* other chunks for the next packets.
*/
if (gso) {
pkt_size = packet->overhead;
list_for_each_entry(chunk, &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)
goto nomem;
else if (pkt_size + padded > tp->pathmtu)
break;
pkt_size += padded;
}
/* Allocate a new skb. */
nskb = alloc_skb(pkt_size + MAX_HEADER, gfp);
if (!nskb)
goto nomem;
/* Make sure the outbound skb has enough header
* room reserved.
*/
skb_reserve(nskb, packet->overhead + MAX_HEADER);
} else {
nskb = head;
}
/**
* 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.
*
* [This whole comment explains SCTP_PAD4() below.]
*/
pkt_size -= packet->overhead;
list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
list_del_init(&chunk->list);
if (sctp_chunk_is_data(chunk)) {
/* 6.3.1 C4) When data is in flight and when allowed
* by rule C5, a new RTT measurement MUST be made each
* round trip. Furthermore, new RTT measurements
* SHOULD be made no more than once per round-trip
* for a given destination transport address.
*/
if (!chunk->resent && !tp->rto_pending) {
chunk->rtt_in_progress = 1;
tp->rto_pending = 1;
}
has_data = 1;
}
padding = SCTP_PAD4(chunk->skb->len) - chunk->skb->len;
if (padding)
memset(skb_put(chunk->skb, padding), 0, padding);
/* if this is the auth chunk that we are adding,
* store pointer where it will be added and put
* the auth into the packet.
*/
if (chunk == packet->auth)
auth = skb_tail_pointer(nskb);
memcpy(skb_put(nskb, chunk->skb->len),
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);
/* If this is a control chunk, this is our last
* reference. Free data chunks after they've been
* acknowledged or have failed.
* Re-queue auth chunks if needed.
*/
pkt_size -= SCTP_PAD4(chunk->skb->len);
if (!sctp_chunk_is_data(chunk) && chunk != packet->auth)
sctp_chunk_free(chunk);
if (!pkt_size)
break;
}
/* SCTP-AUTH, Section 6.2
* The sender MUST calculate the MAC as described in RFC2104 [2]
* using the hash function H as described by the MAC Identifier and
* the shared association key K based on the endpoint pair shared key
* described by the shared key identifier. The 'data' used for the
* computation of the AUTH-chunk is given by the AUTH chunk with its
* HMAC field set to zero (as shown in Figure 6) followed by all
* chunks that are placed after the AUTH chunk in the SCTP packet.
*/
if (auth)
sctp_auth_calculate_hmac(asoc, nskb,
(struct sctp_auth_chunk *)auth,
gfp);
if (packet->auth) {
if (!list_empty(&packet->chunk_list)) {
/* We will generate more packets, so re-queue
* auth chunk.
*/
list_add(&packet->auth->list,
&packet->chunk_list);
} else {
sctp_chunk_free(packet->auth);
packet->auth = NULL;
}
}
if (!gso)
break;
if (skb_gro_receive(&head, nskb)) {
kfree_skb(nskb);
goto nomem;
}
nskb = NULL;
if (WARN_ON_ONCE(skb_shinfo(head)->gso_segs >=
sk->sk_gso_max_segs))
goto nomem;
} while (!list_empty(&packet->chunk_list));
/* 2) Calculate the Adler-32 checksum of the whole packet,
* including the SCTP common header and all the
* chunks.
*
* Note: Adler-32 is no longer applicable, as has been replaced
* by CRC32-C as described in <draft-ietf-tsvwg-sctpcsum-02.txt>.
*
* If it's a GSO packet, it's postponed to sctp_skb_segment.
*/
if (!sctp_checksum_disable || gso) {
if (!gso && (!(dst->dev->features & NETIF_F_SCTP_CRC) ||
dst_xfrm(dst) || packet->ipfragok)) {
sh->checksum = sctp_compute_cksum(head, 0);
} else {
/* no need to seed pseudo checksum for SCTP */
head->ip_summed = CHECKSUM_PARTIAL;
head->csum_start = skb_transport_header(head) - head->head;
head->csum_offset = offsetof(struct sctphdr, checksum);
}
}
/* IP layer ECN support
* From RFC 2481
* "The ECN-Capable Transport (ECT) bit would be set by the
* data sender to indicate that the end-points of the
* transport protocol are ECN-capable."
*
* Now setting the ECT bit all the time, as it should not cause
* any problems protocol-wise even if our peer ignores it.
*
* Note: The works for IPv6 layer checks this bit too later
* in transmission. See IP6_ECN_flow_xmit().
*/
tp->af_specific->ecn_capable(sk);
/* Set up the IP options. */
/* BUG: not implemented
* For v4 this all lives somewhere in sk->sk_opt...
*/
/* Dump that on IP! */
if (asoc) {
asoc->stats.opackets += pktcount;
if (asoc->peer.last_sent_to != tp)
/* Considering the multiple CPU scenario, this is a
* "correcter" place for last_sent_to. --xguo
*/
asoc->peer.last_sent_to = tp;
}
if (has_data) {
struct timer_list *timer;
unsigned long timeout;
/* Restart the AUTOCLOSE timer when sending data. */
if (sctp_state(asoc, ESTABLISHED) &&
asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE]) {
timer = &asoc->timers[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
timeout = asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE];
if (!mod_timer(timer, jiffies + timeout))
sctp_association_hold(asoc);
}
}
pr_debug("***sctp_transmit_packet*** skb->len:%d\n", head->len);
if (gso) {
/* Cleanup our debris for IP stacks */
memset(head->cb, 0, max(sizeof(struct inet_skb_parm),
sizeof(struct inet6_skb_parm)));
skb_shinfo(head)->gso_segs = pktcount;
skb_shinfo(head)->gso_size = GSO_BY_FRAGS;
/* We have to refresh this in case we are xmiting to
* more than one transport at a time
*/
rcu_read_lock();
if (__sk_dst_get(sk) != tp->dst) {
dst_hold(tp->dst);
sk_setup_caps(sk, tp->dst);
}
rcu_read_unlock();
}
head->ignore_df = packet->ipfragok;
tp->af_specific->sctp_xmit(head, tp);
goto out;
nomem:
if (packet->auth && list_empty(&packet->auth->list))
sctp_chunk_free(packet->auth);
nodst:
/* FIXME: Returning the 'err' will effect all the associations
* associated with a socket, although only one of the paths of the
* association is unreachable.
* The real failure of a transport or association can be passed on
* to the user via notifications. So setting this error may not be
* required.
*/
/* err = -EHOSTUNREACH; */
kfree_skb(head);
err:
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);
}
out:
sctp_packet_reset(packet);
return err;
}
/********************************************************************
* 2nd Level Abstractions
********************************************************************/
/* This private function check to see if a chunk can be added */
static sctp_xmit_t 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)
/* Nagle disabled */
return SCTP_XMIT_OK;
if (!sctp_packet_empty(packet))
/* Append to packet */
return SCTP_XMIT_OK;
if (inflight == 0)
/* Nothing unacked */
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 - sizeof(sctp_data_chunk_t) - 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;
/* Has been accepted for transmission. */
if (!asoc->peer.prsctp_capable)
chunk->msg->can_abandon = 0;
sctp_chunk_assign_tsn(chunk);
sctp_chunk_assign_ssn(chunk);
}
static sctp_xmit_t sctp_packet_will_fit(struct sctp_packet *packet,
struct sctp_chunk *chunk,
u16 chunk_len)
{
size_t psize, pmtu, maxsize;
sctp_xmit_t retval = SCTP_XMIT_OK;
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;
}