/* 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; skb_queue_head_init(&packet->chunks); 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; SCTP_DEBUG_PRINTK("%s: packet:%p\n", __FUNCTION__, packet); while ((chunk = (struct sctp_chunk *)__skb_dequeue(&packet->chunks)) != NULL) 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->pmtu) : (packet->transport->pmtu)); 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. */ __skb_queue_tail(&packet->chunks, (struct sk_buff *)chunk); 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; struct sk_buff *nskb; struct sctp_chunk *chunk; struct sock *sk; int err = 0; int padding; /* How much padding do we need? */ __u8 has_data = 0; struct dst_entry *dst; SCTP_DEBUG_PRINTK("%s: packet:%p\n", __FUNCTION__, packet); /* Do NOT generate a chunkless packet. */ chunk = (struct sctp_chunk *)skb_peek(&packet->chunks); if (unlikely(!chunk)) return err; /* Set up convenience variables... */ sk = chunk->skb->sk; /* Allocate the new skb. */ nskb = dev_alloc_skb(packet->size); if (!nskb) goto nomem; /* Make sure the outbound skb has enough header room reserved. */ skb_reserve(nskb, packet->overhead); /* Set the owning socket so that we know where to get the * destination IP address. */ skb_set_owner_w(nskb, sk); /* 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>. */ 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"); while ((chunk = (struct sctp_chunk *)__skb_dequeue(&packet->chunks)) != NULL) { 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); 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. */ 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); } } dst = tp->dst; /* 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)); sctp_assoc_sync_pmtu(asoc); } nskb->dst = dst_clone(tp->dst); if (!nskb->dst) goto no_route; SCTP_DEBUG_PRINTK("***sctp_transmit_packet*** skb len %d\n", nskb->len); (*tp->af_specific->sctp_xmit)(nskb, tp, packet->ipfragok); 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. */ while ((chunk = (struct sctp_chunk *)__skb_dequeue(&packet->chunks)) != NULL) { 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->pmtu; 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) 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->pmtu - packet->overhead) { 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. */ 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; }