/* 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_chunk *chunk = NULL;
pr_debug("%s: packet:%p vtag:0x%x\n", __func__, packet, vtag);
packet->vtag = vtag;
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;
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)
{
sctp_xmit_t retval;
int error = 0;
pr_debug("%s: packet:%p chunk:%p\n", __func__, 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.
*/
if (!one_packet)
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 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 = WORD_ROUND(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;
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)
{
struct sctp_transport *tp = packet->transport;
struct sctp_association *asoc = tp->asoc;
struct sctphdr *sh;
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;
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 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.
*/
sctp_packet_set_owner_w(nskb, 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)
goto no_route;
skb_dst_set(nskb, dst);
/* Build the SCTP header. */
sh = (struct sctphdr *)skb_push(nskb, sizeof(struct sctphdr));
skb_reset_transport_header(nskb);
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;
/**
* 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.]
*/
pr_debug("***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)) {
/* 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 = WORD_ROUND(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.
*/
if (!sctp_chunk_is_data(chunk))
sctp_chunk_free(chunk);
}
/* 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_ATOMIC);
/* 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 (!sctp_checksum_disable) {
if (!(dst->dev->features & NETIF_F_SCTP_CSUM) ||
(dst_xfrm(dst) != NULL) || packet->ipfragok) {
sh->checksum = sctp_compute_cksum(nskb, 0);
} else {
/* no need to seed pseudo checksum for SCTP */
nskb->ip_summed = CHECKSUM_PARTIAL;
nskb->csum_start = skb_transport_header(nskb) - nskb->head;
nskb->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(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->stats.opackets++;
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", nskb->len);
nskb->local_df = packet->ipfragok;
tp->af_specific->sctp_xmit(nskb, tp);
out:
sctp_packet_reset(packet);
return err;
no_route:
kfree_skb(nskb);
IP_INC_STATS_BH(sock_net(asoc->base.sk), 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 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)
{
sctp_xmit_t retval = SCTP_XMIT_OK;
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) {
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;
}
}
/* 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)
if (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 (!sctp_sk(asoc->base.sk)->nodelay && sctp_packet_empty(packet) &&
inflight && sctp_state(asoc, ESTABLISHED)) {
unsigned int max = transport->pathmtu - packet->overhead;
unsigned int len = chunk->skb->len + 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.
* Don't delay large message writes that may have been
* fragmeneted into small peices.
*/
if ((len < max) && chunk->msg->can_delay) {
retval = SCTP_XMIT_NAGLE_DELAY;
goto finish;
}
}
finish:
return retval;
}
/* 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;
size_t pmtu;
int too_big;
sctp_xmit_t retval = SCTP_XMIT_OK;
psize = packet->size;
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) {
/* It's OK to fragmet 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 chunk we are adding is a control chunk
* 3. The packet doesn't have any data in it yet and data
* requires authentication.
*/
if (sctp_packet_empty(packet) || !sctp_chunk_is_data(chunk) ||
(!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;
} else {
retval = SCTP_XMIT_PMTU_FULL;
}
}
return retval;
}