/* 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 * . * * Please send any bug reports or fixes you make to the * email address(es): * lksctp developers * * Written or modified by: * La Monte H.P. Yarroll * Karl Knutson * Jon Grimm * Sridhar Samudrala */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include #include #include #include #include #include #include #include #include #include #include #include #include /* for sa_family_t */ #include #include #include #include /* 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; 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 (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 (!sctp_chunk_retransmitted(chunk) && !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 . * * 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; 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; }