/* SCTP kernel reference 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 reference Implementation
*
* These functions handle output processing.
*
* The SCTP reference 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.
*
* The SCTP reference 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, write to
* the Free Software Foundation, 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*
* Please send any bug reports or fixes you make to the
* email address(es):
* lksctp developers <lksctp-developers@lists.sourceforge.net>
*
* Or submit a bug report through the following website:
* http://www.sf.net/projects/lksctp
*
* 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>
*
* Any bugs reported given to us we will try to fix... any fixes shared will
* be incorporated into the next SCTP release.
*/
#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 <net/inet_ecn.h>
#include <net/icmp.h>
#ifndef TEST_FRAME
#include <net/tcp.h>
#endif /* TEST_FRAME (not defined) */
#include <linux/socket.h> /* for sa_family_t */
#include <net/sock.h>
#include <net/sctp/sctp.h>
#include <net/sctp/sm.h>
/* Forward declarations for private helpers. */
static sctp_xmit_t sctp_packet_append_data(struct sctp_packet *packet,
struct sctp_chunk *chunk);
/* 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_chunk *chunk = NULL;
SCTP_DEBUG_PRINTK("%s: packet:%p vtag:0x%x\n", __FUNCTION__,
packet, vtag);
packet->vtag = vtag;
packet->has_cookie_echo = 0;
packet->has_sack = 0;
packet->ipfragok = 0;
if (ecn_capable && sctp_packet_empty(packet)) {
chunk = sctp_get_ecne_prepend(packet->transport->asoc);
/* If there a is a prepend chunk stick it on the list before
* any other chunks get appended.
*/
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;
SCTP_DEBUG_PRINTK("%s: packet:%p transport:%p\n", __FUNCTION__,
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;
packet->size = overhead;
packet->vtag = 0;
packet->has_cookie_echo = 0;
packet->has_sack = 0;
packet->ipfragok = 0;
packet->malloced = 0;
return packet;
}
/* Free a packet. */
void sctp_packet_free(struct sctp_packet *packet)
{
struct sctp_chunk *chunk, *tmp;
SCTP_DEBUG_PRINTK("%s: packet:%p\n", __FUNCTION__, packet);
list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
list_del_init(&chunk->list);
sctp_chunk_free(chunk);
}
if (packet->malloced)
kfree(packet);
}
/* 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)
{
sctp_xmit_t retval;
int error = 0;
SCTP_DEBUG_PRINTK("%s: packet:%p chunk:%p\n", __FUNCTION__,
packet, chunk);
switch ((retval = (sctp_packet_append_chunk(packet, chunk)))) {
case SCTP_XMIT_PMTU_FULL:
if (!packet->has_cookie_echo) {
error = sctp_packet_transmit(packet);
if (error < 0)
chunk->skb->sk->sk_err = -error;
/* If we have an empty packet, then we can NOT ever
* return PMTU_FULL.
*/
retval = sctp_packet_append_chunk(packet, chunk);
}
break;
case SCTP_XMIT_RWND_FULL:
case SCTP_XMIT_OK:
case SCTP_XMIT_NAGLE_DELAY:
break;
};
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;
asoc = pkt->transport->asoc;
if (asoc->a_rwnd > asoc->rwnd) {
struct sctp_chunk *sack;
asoc->a_rwnd = asoc->rwnd;
sack = sctp_make_sack(asoc);
if (sack) {
struct timer_list *timer;
retval = sctp_packet_append_chunk(pkt, sack);
asoc->peer.sack_needed = 0;
timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
if (timer_pending(timer) && del_timer(timer))
sctp_association_put(asoc);
}
}
}
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;
__u16 chunk_len = WORD_ROUND(ntohs(chunk->chunk_hdr->length));
size_t psize;
size_t pmtu;
int too_big;
SCTP_DEBUG_PRINTK("%s: packet:%p chunk:%p\n", __FUNCTION__, packet,
chunk);
retval = sctp_packet_bundle_sack(packet, chunk);
psize = packet->size;
if (retval != SCTP_XMIT_OK)
goto finish;
pmtu = ((packet->transport->asoc) ?
(packet->transport->asoc->pathmtu) :
(packet->transport->pathmtu));
too_big = (psize + chunk_len > pmtu);
/* Decide if we need to fragment or resubmit later. */
if (too_big) {
/* Both control chunks and data chunks with TSNs are
* non-fragmentable.
*/
if (sctp_packet_empty(packet) || !sctp_chunk_is_data(chunk)) {
/* We no longer do re-fragmentation.
* Just fragment at the IP layer, if we
* actually hit this condition
*/
packet->ipfragok = 1;
goto append;
} else {
retval = SCTP_XMIT_PMTU_FULL;
goto finish;
}
}
append:
/* We believe that this chunk is OK to add to the packet (as
* long as we have the cwnd for it).
*/
/* DATA is a special case since we must examine both rwnd and cwnd
* before we send DATA.
*/
if (sctp_chunk_is_data(chunk)) {
retval = sctp_packet_append_data(packet, chunk);
/* Disallow SACK bundling after DATA. */
packet->has_sack = 1;
if (SCTP_XMIT_OK != retval)
goto finish;
} else if (SCTP_CID_COOKIE_ECHO == chunk->chunk_hdr->type)
packet->has_cookie_echo = 1;
else if (SCTP_CID_SACK == chunk->chunk_hdr->type)
packet->has_sack = 1;
/* 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;
}
/* 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)
{
struct sctp_transport *tp = packet->transport;
struct sctp_association *asoc = tp->asoc;
struct sctphdr *sh;
__u32 crc32 = 0;
struct sk_buff *nskb;
struct sctp_chunk *chunk, *tmp;
struct sock *sk;
int err = 0;
int padding; /* How much padding do we need? */
__u8 has_data = 0;
struct dst_entry *dst = tp->dst;
SCTP_DEBUG_PRINTK("%s: packet:%p\n", __FUNCTION__, 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 new skb. */
nskb = alloc_skb(packet->size + LL_MAX_HEADER, GFP_ATOMIC);
if (!nskb)
goto nomem;
/* Make sure the outbound skb has enough header room reserved. */
skb_reserve(nskb, packet->overhead + LL_MAX_HEADER);
/* Set the owning socket so that we know where to get the
* destination IP address.
*/
skb_set_owner_w(nskb, sk);
/* The 'obsolete' field of dst is set to 2 when a dst is freed. */
if (!dst || (dst->obsolete > 1)) {
dst_release(dst);
sctp_transport_route(tp, NULL, sctp_sk(sk));
if (asoc && (asoc->param_flags & SPP_PMTUD_ENABLE)) {
sctp_assoc_sync_pmtu(asoc);
}
}
nskb->dst = dst_clone(tp->dst);
if (!nskb->dst)
goto no_route;
dst = nskb->dst;
/* Build the SCTP header. */
sh = (struct sctphdr *)skb_push(nskb, sizeof(struct sctphdr));
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;
/* 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 (!(dst->dev->features & NETIF_F_NO_CSUM))
crc32 = sctp_start_cksum((__u8 *)sh, sizeof(struct sctphdr));
/**
* 6.10 Bundling
*
* An endpoint bundles chunks by simply including multiple
* chunks in one outbound SCTP packet. ...
*/
/**
* 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 WORD_ROUND() below.]
*/
SCTP_DEBUG_PRINTK("***sctp_transmit_packet***\n");
list_for_each_entry_safe(chunk, tmp, &packet->chunk_list, list) {
list_del_init(&chunk->list);
if (sctp_chunk_is_data(chunk)) {
if (!chunk->has_tsn) {
sctp_chunk_assign_ssn(chunk);
sctp_chunk_assign_tsn(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 (!tp->rto_pending) {
chunk->rtt_in_progress = 1;
tp->rto_pending = 1;
}
} else
chunk->resent = 1;
chunk->sent_at = jiffies;
has_data = 1;
}
padding = WORD_ROUND(chunk->skb->len) - chunk->skb->len;
if (padding)
memset(skb_put(chunk->skb, padding), 0, padding);
if (dst->dev->features & NETIF_F_NO_CSUM)
memcpy(skb_put(nskb, chunk->skb->len),
chunk->skb->data, chunk->skb->len);
else
crc32 = sctp_update_copy_cksum(skb_put(nskb,
chunk->skb->len),
chunk->skb->data,
chunk->skb->len, crc32);
SCTP_DEBUG_PRINTK("%s %p[%s] %s 0x%x, %s %d, %s %d, %s %d\n",
"*** Chunk", 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,
"length", ntohs(chunk->chunk_hdr->length),
"chunk->skb->len", chunk->skb->len,
"rtt_in_progress", 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.
*/
if (!sctp_chunk_is_data(chunk))
sctp_chunk_free(chunk);
}
/* Perform final transformation on checksum. */
if (!(dst->dev->features & NETIF_F_NO_CSUM))
crc32 = sctp_end_cksum(crc32);
/* 3) Put the resultant value into the checksum field in the
* common header, and leave the rest of the bits unchanged.
*/
sh->checksum = htonl(crc32);
/* 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().
*/
INET_ECN_xmit(nskb->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->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;
tp->last_time_used = jiffies;
/* Restart the AUTOCLOSE timer when sending data. */
if (sctp_state(asoc, ESTABLISHED) && asoc->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);
}
}
SCTP_DEBUG_PRINTK("***sctp_transmit_packet*** skb len %d\n",
nskb->len);
if (tp->param_flags & SPP_PMTUD_ENABLE)
(*tp->af_specific->sctp_xmit)(nskb, tp, packet->ipfragok);
else
(*tp->af_specific->sctp_xmit)(nskb, tp, 1);
out:
packet->size = packet->overhead;
return err;
no_route:
kfree_skb(nskb);
IP_INC_STATS_BH(IPSTATS_MIB_OUTNOROUTES);
/* 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; */
err:
/* Control chunks are unreliable so just drop them. DATA chunks
* will get resent or dropped later.
*/
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);
}
goto out;
nomem:
err = -ENOMEM;
goto err;
}
/********************************************************************
* 2nd Level Abstractions
********************************************************************/
/* This private function handles the specifics of appending DATA chunks. */
static sctp_xmit_t sctp_packet_append_data(struct sctp_packet *packet,
struct sctp_chunk *chunk)
{
sctp_xmit_t retval = SCTP_XMIT_OK;
size_t datasize, rwnd, inflight;
struct sctp_transport *transport = packet->transport;
__u32 max_burst_bytes;
struct sctp_association *asoc = transport->asoc;
struct sctp_sock *sp = sctp_sk(asoc->base.sk);
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 = asoc->outqueue.outstanding_bytes;
datasize = sctp_data_size(chunk);
if (datasize > rwnd) {
if (inflight > 0) {
/* We have (at least) one data chunk in flight,
* so we can't fall back to rule 6.1 B).
*/
retval = SCTP_XMIT_RWND_FULL;
goto finish;
}
}
/* sctpimpguide-05 2.14.2
* D) When the time comes for the sender to
* transmit new DATA chunks, the protocol parameter Max.Burst MUST
* first be applied to limit how many new DATA chunks may be sent.
* The limit is applied by adjusting cwnd as follows:
* if ((flightsize + Max.Burst * MTU) < cwnd)
* cwnd = flightsize + Max.Burst * MTU
*/
max_burst_bytes = asoc->max_burst * asoc->pathmtu;
if ((transport->flight_size + max_burst_bytes) < transport->cwnd) {
transport->cwnd = transport->flight_size + max_burst_bytes;
SCTP_DEBUG_PRINTK("%s: cwnd limited by max_burst: "
"transport: %p, cwnd: %d, "
"ssthresh: %d, flight_size: %d, "
"pba: %d\n",
__FUNCTION__, transport,
transport->cwnd,
transport->ssthresh,
transport->flight_size,
transport->partial_bytes_acked);
}
/* 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 <= 0)
if (transport->flight_size >= transport->cwnd) {
retval = SCTP_XMIT_RWND_FULL;
goto finish;
}
/* 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 (!sp->nodelay && sctp_packet_empty(packet) &&
q->outstanding_bytes && sctp_state(asoc, ESTABLISHED)) {
unsigned len = datasize + q->out_qlen;
/* Check whether this chunk and all the rest of pending
* data will fit or delay in hopes of bundling a full
* sized packet.
*/
if (len < asoc->frag_point) {
retval = SCTP_XMIT_NAGLE_DELAY;
goto finish;
}
}
/* 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. Include sk_buff overhead
* while updating peer.rwnd so that it reduces the chances of a
* receiver running out of receive buffer space even when receive
* window is still open. This can happen when a sender is sending
* sending small messages.
*/
datasize += sizeof(struct sk_buff);
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;
finish:
return retval;
}
