/* * CDDL HEADER START * * The contents of this file are subject to the terms of the * Common Development and Distribution License (the "License"). * You may not use this file except in compliance with the License. * * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE * or http://www.opensolaris.org/os/licensing. * See the License for the specific language governing permissions * and limitations under the License. * * When distributing Covered Code, include this CDDL HEADER in each * file and include the License file at usr/src/OPENSOLARIS.LICENSE. * If applicable, add the following below this CDDL HEADER, with the * fields enclosed by brackets "[]" replaced with your own identifying * information: Portions Copyright [yyyy] [name of copyright owner] * * CDDL HEADER END */ /* * Copyright 2008 Sun Microsystems, Inc. All rights reserved. * Use is subject to license terms. */ #pragma ident "%Z%%M% %I% %E% SMI" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * This file implements TCP fusion - a protocol-less data path for TCP * loopback connections. The fusion of two local TCP endpoints occurs * at connection establishment time. Various conditions (see details * in tcp_fuse()) need to be met for fusion to be successful. If it * fails, we fall back to the regular TCP data path; if it succeeds, * both endpoints proceed to use tcp_fuse_output() as the transmit path. * tcp_fuse_output() enqueues application data directly onto the peer's * receive queue; no protocol processing is involved. After enqueueing * the data, the sender can either push (putnext) data up the receiver's * read queue; or the sender can simply return and let the receiver * retrieve the enqueued data via the synchronous streams entry point * tcp_fuse_rrw(). The latter path is taken if synchronous streams is * enabled (the default). It is disabled if sockfs no longer resides * directly on top of tcp module due to a module insertion or removal. * It also needs to be temporarily disabled when sending urgent data * because the tcp_fuse_rrw() path bypasses the M_PROTO processing done * by strsock_proto() hook. * * Sychronization is handled by squeue and the mutex tcp_non_sq_lock. * One of the requirements for fusion to succeed is that both endpoints * need to be using the same squeue. This ensures that neither side * can disappear while the other side is still sending data. By itself, * squeue is not sufficient for guaranteeing safety when synchronous * streams is enabled. The reason is that tcp_fuse_rrw() doesn't enter * the squeue and its access to tcp_rcv_list and other fusion-related * fields needs to be sychronized with the sender. tcp_non_sq_lock is * used for this purpose. When there is urgent data, the sender needs * to push the data up the receiver's streams read queue. In order to * avoid holding the tcp_non_sq_lock across putnext(), the sender sets * the peer tcp's tcp_fuse_syncstr_plugged bit and releases tcp_non_sq_lock * (see macro TCP_FUSE_SYNCSTR_PLUG_DRAIN()). If tcp_fuse_rrw() enters * after this point, it will see that synchronous streams is plugged and * will wait on tcp_fuse_plugcv. After the sender has finished pushing up * all urgent data, it will clear the tcp_fuse_syncstr_plugged bit using * TCP_FUSE_SYNCSTR_UNPLUG_DRAIN(). This will cause any threads waiting * on tcp_fuse_plugcv to return EBUSY, and in turn cause strget() to call * getq_noenab() to dequeue data from the stream head instead. Once the * data on the stream head has been consumed, tcp_fuse_rrw() may again * be used to process tcp_rcv_list. However, if TCP_FUSE_SYNCSTR_STOP() * has been called, all future calls to tcp_fuse_rrw() will return EBUSY, * effectively disabling synchronous streams. * * The following note applies only to the synchronous streams mode. * * Flow control is done by checking the size of receive buffer and * the number of data blocks, both set to different limits. This is * different than regular streams flow control where cumulative size * check dominates block count check -- streams queue high water mark * typically represents bytes. Each enqueue triggers notifications * to the receiving process; a build up of data blocks indicates a * slow receiver and the sender should be blocked or informed at the * earliest moment instead of further wasting system resources. In * effect, this is equivalent to limiting the number of outstanding * segments in flight. */ /* * Setting this to false means we disable fusion altogether and * loopback connections would go through the protocol paths. */ boolean_t do_tcp_fusion = B_TRUE; /* * Enabling this flag allows sockfs to retrieve data directly * from a fused tcp endpoint using synchronous streams interface. */ boolean_t do_tcp_direct_sockfs = B_TRUE; /* * This is the minimum amount of outstanding writes allowed on * a synchronous streams-enabled receiving endpoint before the * sender gets flow-controlled. Setting this value to 0 means * that the data block limit is equivalent to the byte count * limit, which essentially disables the check. */ #define TCP_FUSION_RCV_UNREAD_MIN 8 uint_t tcp_fusion_rcv_unread_min = TCP_FUSION_RCV_UNREAD_MIN; static void tcp_fuse_syncstr_enable(tcp_t *); static void tcp_fuse_syncstr_disable(tcp_t *); static void strrput_sig(queue_t *, boolean_t); /* * Return true if this connection needs some IP functionality */ static boolean_t tcp_loopback_needs_ip(tcp_t *tcp, netstack_t *ns) { ipsec_stack_t *ipss = ns->netstack_ipsec; /* * If ire is not cached, do not use fusion */ if (tcp->tcp_connp->conn_ire_cache == NULL) { /* * There is no need to hold conn_lock here because when called * from tcp_fuse() there can be no window where conn_ire_cache * can change. This is not true whe called from * tcp_fuse_output(). conn_ire_cache can become null just * after the check, but it's ok if a few packets are delivered * in the fused state. */ return (B_TRUE); } if (tcp->tcp_ipversion == IPV4_VERSION) { if (tcp->tcp_ip_hdr_len != IP_SIMPLE_HDR_LENGTH) return (B_TRUE); if (CONN_OUTBOUND_POLICY_PRESENT(tcp->tcp_connp, ipss)) return (B_TRUE); if (CONN_INBOUND_POLICY_PRESENT(tcp->tcp_connp, ipss)) return (B_TRUE); } else { if (tcp->tcp_ip_hdr_len != IPV6_HDR_LEN) return (B_TRUE); if (CONN_OUTBOUND_POLICY_PRESENT_V6(tcp->tcp_connp, ipss)) return (B_TRUE); if (CONN_INBOUND_POLICY_PRESENT_V6(tcp->tcp_connp, ipss)) return (B_TRUE); } if (!CONN_IS_LSO_MD_FASTPATH(tcp->tcp_connp)) return (B_TRUE); return (B_FALSE); } /* * This routine gets called by the eager tcp upon changing state from * SYN_RCVD to ESTABLISHED. It fuses a direct path between itself * and the active connect tcp such that the regular tcp processings * may be bypassed under allowable circumstances. Because the fusion * requires both endpoints to be in the same squeue, it does not work * for simultaneous active connects because there is no easy way to * switch from one squeue to another once the connection is created. * This is different from the eager tcp case where we assign it the * same squeue as the one given to the active connect tcp during open. */ void tcp_fuse(tcp_t *tcp, uchar_t *iphdr, tcph_t *tcph) { conn_t *peer_connp, *connp = tcp->tcp_connp; tcp_t *peer_tcp; tcp_stack_t *tcps = tcp->tcp_tcps; netstack_t *ns; ip_stack_t *ipst = tcps->tcps_netstack->netstack_ip; ASSERT(!tcp->tcp_fused); ASSERT(tcp->tcp_loopback); ASSERT(tcp->tcp_loopback_peer == NULL); /* * We need to inherit q_hiwat of the listener tcp, but we can't * really use tcp_listener since we get here after sending up * T_CONN_IND and tcp_wput_accept() may be called independently, * at which point tcp_listener is cleared; this is why we use * tcp_saved_listener. The listener itself is guaranteed to be * around until tcp_accept_finish() is called on this eager -- * this won't happen until we're done since we're inside the * eager's perimeter now. */ ASSERT(tcp->tcp_saved_listener != NULL); /* * Lookup peer endpoint; search for the remote endpoint having * the reversed address-port quadruplet in ESTABLISHED state, * which is guaranteed to be unique in the system. Zone check * is applied accordingly for loopback address, but not for * local address since we want fusion to happen across Zones. */ if (tcp->tcp_ipversion == IPV4_VERSION) { peer_connp = ipcl_conn_tcp_lookup_reversed_ipv4(connp, (ipha_t *)iphdr, tcph, ipst); } else { peer_connp = ipcl_conn_tcp_lookup_reversed_ipv6(connp, (ip6_t *)iphdr, tcph, ipst); } /* * We can only proceed if peer exists, resides in the same squeue * as our conn and is not raw-socket. The squeue assignment of * this eager tcp was done earlier at the time of SYN processing * in ip_fanout_tcp{_v6}. Note that similar squeues by itself * doesn't guarantee a safe condition to fuse, hence we perform * additional tests below. */ ASSERT(peer_connp == NULL || peer_connp != connp); if (peer_connp == NULL || peer_connp->conn_sqp != connp->conn_sqp || !IPCL_IS_TCP(peer_connp)) { if (peer_connp != NULL) { TCP_STAT(tcps, tcp_fusion_unqualified); CONN_DEC_REF(peer_connp); } return; } peer_tcp = peer_connp->conn_tcp; /* active connect tcp */ ASSERT(peer_tcp != NULL && peer_tcp != tcp && !peer_tcp->tcp_fused); ASSERT(peer_tcp->tcp_loopback && peer_tcp->tcp_loopback_peer == NULL); ASSERT(peer_connp->conn_sqp == connp->conn_sqp); /* * Fuse the endpoints; we perform further checks against both * tcp endpoints to ensure that a fusion is allowed to happen. * In particular we bail out for non-simple TCP/IP or if IPsec/ * IPQoS policy/kernel SSL exists. */ ns = tcps->tcps_netstack; ipst = ns->netstack_ip; if (!tcp->tcp_unfusable && !peer_tcp->tcp_unfusable && !tcp_loopback_needs_ip(tcp, ns) && !tcp_loopback_needs_ip(peer_tcp, ns) && tcp->tcp_kssl_ent == NULL && !IPP_ENABLED(IPP_LOCAL_OUT|IPP_LOCAL_IN, ipst)) { mblk_t *mp; struct stroptions *stropt; queue_t *peer_rq = peer_tcp->tcp_rq; ASSERT(!TCP_IS_DETACHED(peer_tcp) && peer_rq != NULL); ASSERT(tcp->tcp_fused_sigurg_mp == NULL); ASSERT(peer_tcp->tcp_fused_sigurg_mp == NULL); ASSERT(tcp->tcp_kssl_ctx == NULL); /* * We need to drain data on both endpoints during unfuse. * If we need to send up SIGURG at the time of draining, * we want to be sure that an mblk is readily available. * This is why we pre-allocate the M_PCSIG mblks for both * endpoints which will only be used during/after unfuse. */ if ((mp = allocb(1, BPRI_HI)) == NULL) goto failed; tcp->tcp_fused_sigurg_mp = mp; if ((mp = allocb(1, BPRI_HI)) == NULL) goto failed; peer_tcp->tcp_fused_sigurg_mp = mp; /* Allocate M_SETOPTS mblk */ if ((mp = allocb(sizeof (*stropt), BPRI_HI)) == NULL) goto failed; /* If peer sodirect enabled then disable */ ASSERT(tcp->tcp_sodirect == NULL); if (peer_tcp->tcp_sodirect != NULL) { mutex_enter(peer_tcp->tcp_sodirect->sod_lock); SOD_DISABLE(peer_tcp->tcp_sodirect); mutex_exit(peer_tcp->tcp_sodirect->sod_lock); peer_tcp->tcp_sodirect = NULL; } /* Fuse both endpoints */ peer_tcp->tcp_loopback_peer = tcp; tcp->tcp_loopback_peer = peer_tcp; peer_tcp->tcp_fused = tcp->tcp_fused = B_TRUE; /* * We never use regular tcp paths in fusion and should * therefore clear tcp_unsent on both endpoints. Having * them set to non-zero values means asking for trouble * especially after unfuse, where we may end up sending * through regular tcp paths which expect xmit_list and * friends to be correctly setup. */ peer_tcp->tcp_unsent = tcp->tcp_unsent = 0; tcp_timers_stop(tcp); tcp_timers_stop(peer_tcp); /* * At this point we are a detached eager tcp and therefore * don't have a queue assigned to us until accept happens. * In the mean time the peer endpoint may immediately send * us data as soon as fusion is finished, and we need to be * able to flow control it in case it sends down huge amount * of data while we're still detached. To prevent that we * inherit the listener's q_hiwat value; this is temporary * since we'll repeat the process in tcp_accept_finish(). */ (void) tcp_fuse_set_rcv_hiwat(tcp, tcp->tcp_saved_listener->tcp_rq->q_hiwat); /* * Set the stream head's write offset value to zero since we * won't be needing any room for TCP/IP headers; tell it to * not break up the writes (this would reduce the amount of * work done by kmem); and configure our receive buffer. * Note that we can only do this for the active connect tcp * since our eager is still detached; it will be dealt with * later in tcp_accept_finish(). */ DB_TYPE(mp) = M_SETOPTS; mp->b_wptr += sizeof (*stropt); stropt = (struct stroptions *)mp->b_rptr; stropt->so_flags = SO_MAXBLK | SO_WROFF | SO_HIWAT; stropt->so_maxblk = tcp_maxpsz_set(peer_tcp, B_FALSE); stropt->so_wroff = 0; /* * Record the stream head's high water mark for * peer endpoint; this is used for flow-control * purposes in tcp_fuse_output(). */ stropt->so_hiwat = tcp_fuse_set_rcv_hiwat(peer_tcp, peer_rq->q_hiwat); /* Send the options up */ putnext(peer_rq, mp); } else { TCP_STAT(tcps, tcp_fusion_unqualified); } CONN_DEC_REF(peer_connp); return; failed: if (tcp->tcp_fused_sigurg_mp != NULL) { freeb(tcp->tcp_fused_sigurg_mp); tcp->tcp_fused_sigurg_mp = NULL; } if (peer_tcp->tcp_fused_sigurg_mp != NULL) { freeb(peer_tcp->tcp_fused_sigurg_mp); peer_tcp->tcp_fused_sigurg_mp = NULL; } CONN_DEC_REF(peer_connp); } /* * Unfuse a previously-fused pair of tcp loopback endpoints. */ void tcp_unfuse(tcp_t *tcp) { tcp_t *peer_tcp = tcp->tcp_loopback_peer; ASSERT(tcp->tcp_fused && peer_tcp != NULL); ASSERT(peer_tcp->tcp_fused && peer_tcp->tcp_loopback_peer == tcp); ASSERT(tcp->tcp_connp->conn_sqp == peer_tcp->tcp_connp->conn_sqp); ASSERT(tcp->tcp_unsent == 0 && peer_tcp->tcp_unsent == 0); ASSERT(tcp->tcp_fused_sigurg_mp != NULL); ASSERT(peer_tcp->tcp_fused_sigurg_mp != NULL); /* * We disable synchronous streams, drain any queued data and * clear tcp_direct_sockfs. The synchronous streams entry * points will become no-ops after this point. */ tcp_fuse_disable_pair(tcp, B_TRUE); /* * Update th_seq and th_ack in the header template */ U32_TO_ABE32(tcp->tcp_snxt, tcp->tcp_tcph->th_seq); U32_TO_ABE32(tcp->tcp_rnxt, tcp->tcp_tcph->th_ack); U32_TO_ABE32(peer_tcp->tcp_snxt, peer_tcp->tcp_tcph->th_seq); U32_TO_ABE32(peer_tcp->tcp_rnxt, peer_tcp->tcp_tcph->th_ack); /* Unfuse the endpoints */ peer_tcp->tcp_fused = tcp->tcp_fused = B_FALSE; peer_tcp->tcp_loopback_peer = tcp->tcp_loopback_peer = NULL; } /* * Fusion output routine for urgent data. This routine is called by * tcp_fuse_output() for handling non-M_DATA mblks. */ void tcp_fuse_output_urg(tcp_t *tcp, mblk_t *mp) { mblk_t *mp1; struct T_exdata_ind *tei; tcp_t *peer_tcp = tcp->tcp_loopback_peer; mblk_t *head, *prev_head = NULL; tcp_stack_t *tcps = tcp->tcp_tcps; ASSERT(tcp->tcp_fused); ASSERT(peer_tcp != NULL && peer_tcp->tcp_loopback_peer == tcp); ASSERT(DB_TYPE(mp) == M_PROTO || DB_TYPE(mp) == M_PCPROTO); ASSERT(mp->b_cont != NULL && DB_TYPE(mp->b_cont) == M_DATA); ASSERT(MBLKL(mp) >= sizeof (*tei) && MBLKL(mp->b_cont) > 0); /* * Urgent data arrives in the form of T_EXDATA_REQ from above. * Each occurence denotes a new urgent pointer. For each new * urgent pointer we signal (SIGURG) the receiving app to indicate * that it needs to go into urgent mode. This is similar to the * urgent data handling in the regular tcp. We don't need to keep * track of where the urgent pointer is, because each T_EXDATA_REQ * "advances" the urgent pointer for us. * * The actual urgent data carried by T_EXDATA_REQ is then prepended * by a T_EXDATA_IND before being enqueued behind any existing data * destined for the receiving app. There is only a single urgent * pointer (out-of-band mark) for a given tcp. If the new urgent * data arrives before the receiving app reads some existing urgent * data, the previous marker is lost. This behavior is emulated * accordingly below, by removing any existing T_EXDATA_IND messages * and essentially converting old urgent data into non-urgent. */ ASSERT(tcp->tcp_valid_bits & TCP_URG_VALID); /* Let sender get out of urgent mode */ tcp->tcp_valid_bits &= ~TCP_URG_VALID; /* * This flag indicates that a signal needs to be sent up. * This flag will only get cleared once SIGURG is delivered and * is not affected by the tcp_fused flag -- delivery will still * happen even after an endpoint is unfused, to handle the case * where the sending endpoint immediately closes/unfuses after * sending urgent data and the accept is not yet finished. */ peer_tcp->tcp_fused_sigurg = B_TRUE; /* Reuse T_EXDATA_REQ mblk for T_EXDATA_IND */ DB_TYPE(mp) = M_PROTO; tei = (struct T_exdata_ind *)mp->b_rptr; tei->PRIM_type = T_EXDATA_IND; tei->MORE_flag = 0; mp->b_wptr = (uchar_t *)&tei[1]; TCP_STAT(tcps, tcp_fusion_urg); BUMP_MIB(&tcps->tcps_mib, tcpOutUrg); head = peer_tcp->tcp_rcv_list; while (head != NULL) { /* * Remove existing T_EXDATA_IND, keep the data which follows * it and relink our list. Note that we don't modify the * tcp_rcv_last_tail since it never points to T_EXDATA_IND. */ if (DB_TYPE(head) != M_DATA) { mp1 = head; ASSERT(DB_TYPE(mp1->b_cont) == M_DATA); head = mp1->b_cont; mp1->b_cont = NULL; head->b_next = mp1->b_next; mp1->b_next = NULL; if (prev_head != NULL) prev_head->b_next = head; if (peer_tcp->tcp_rcv_list == mp1) peer_tcp->tcp_rcv_list = head; if (peer_tcp->tcp_rcv_last_head == mp1) peer_tcp->tcp_rcv_last_head = head; freeb(mp1); } prev_head = head; head = head->b_next; } } /* * Fusion output routine, called by tcp_output() and tcp_wput_proto(). * If we are modifying any member that can be changed outside the squeue, * like tcp_flow_stopped, we need to take tcp_non_sq_lock. */ boolean_t tcp_fuse_output(tcp_t *tcp, mblk_t *mp, uint32_t send_size) { tcp_t *peer_tcp = tcp->tcp_loopback_peer; uint_t max_unread; boolean_t flow_stopped, peer_data_queued = B_FALSE; boolean_t urgent = (DB_TYPE(mp) != M_DATA); mblk_t *mp1 = mp; ill_t *ilp, *olp; ipha_t *ipha; ip6_t *ip6h; tcph_t *tcph; uint_t ip_hdr_len; uint32_t seq; uint32_t recv_size = send_size; tcp_stack_t *tcps = tcp->tcp_tcps; netstack_t *ns = tcps->tcps_netstack; ip_stack_t *ipst = ns->netstack_ip; ASSERT(tcp->tcp_fused); ASSERT(peer_tcp != NULL && peer_tcp->tcp_loopback_peer == tcp); ASSERT(tcp->tcp_connp->conn_sqp == peer_tcp->tcp_connp->conn_sqp); ASSERT(DB_TYPE(mp) == M_DATA || DB_TYPE(mp) == M_PROTO || DB_TYPE(mp) == M_PCPROTO); max_unread = peer_tcp->tcp_fuse_rcv_unread_hiwater; /* If this connection requires IP, unfuse and use regular path */ if (tcp_loopback_needs_ip(tcp, ns) || tcp_loopback_needs_ip(peer_tcp, ns) || IPP_ENABLED(IPP_LOCAL_OUT|IPP_LOCAL_IN, ipst)) { TCP_STAT(tcps, tcp_fusion_aborted); goto unfuse; } if (send_size == 0) { freemsg(mp); return (B_TRUE); } /* * Handle urgent data; we either send up SIGURG to the peer now * or do it later when we drain, in case the peer is detached * or if we're short of memory for M_PCSIG mblk. */ if (urgent) { /* * We stop synchronous streams when we have urgent data * queued to prevent tcp_fuse_rrw() from pulling it. If * for some reasons the urgent data can't be delivered * below, synchronous streams will remain stopped until * someone drains the tcp_rcv_list. */ TCP_FUSE_SYNCSTR_PLUG_DRAIN(peer_tcp); tcp_fuse_output_urg(tcp, mp); mp1 = mp->b_cont; } if (tcp->tcp_ipversion == IPV4_VERSION && (HOOKS4_INTERESTED_LOOPBACK_IN(ipst) || HOOKS4_INTERESTED_LOOPBACK_OUT(ipst)) || tcp->tcp_ipversion == IPV6_VERSION && (HOOKS6_INTERESTED_LOOPBACK_IN(ipst) || HOOKS6_INTERESTED_LOOPBACK_OUT(ipst))) { /* * Build ip and tcp header to satisfy FW_HOOKS. * We only build it when any hook is present. */ if ((mp1 = tcp_xmit_mp(tcp, mp1, tcp->tcp_mss, NULL, NULL, tcp->tcp_snxt, B_TRUE, NULL, B_FALSE)) == NULL) /* If tcp_xmit_mp fails, use regular path */ goto unfuse; ASSERT(peer_tcp->tcp_connp->conn_ire_cache->ire_ipif != NULL); olp = peer_tcp->tcp_connp->conn_ire_cache->ire_ipif->ipif_ill; /* PFHooks: LOOPBACK_OUT */ if (tcp->tcp_ipversion == IPV4_VERSION) { ipha = (ipha_t *)mp1->b_rptr; DTRACE_PROBE4(ip4__loopback__out__start, ill_t *, NULL, ill_t *, olp, ipha_t *, ipha, mblk_t *, mp1); FW_HOOKS(ipst->ips_ip4_loopback_out_event, ipst->ips_ipv4firewall_loopback_out, NULL, olp, ipha, mp1, mp1, 0, ipst); DTRACE_PROBE1(ip4__loopback__out__end, mblk_t *, mp1); } else { ip6h = (ip6_t *)mp1->b_rptr; DTRACE_PROBE4(ip6__loopback__out__start, ill_t *, NULL, ill_t *, olp, ip6_t *, ip6h, mblk_t *, mp1); FW_HOOKS6(ipst->ips_ip6_loopback_out_event, ipst->ips_ipv6firewall_loopback_out, NULL, olp, ip6h, mp1, mp1, 0, ipst); DTRACE_PROBE1(ip6__loopback__out__end, mblk_t *, mp1); } if (mp1 == NULL) goto unfuse; /* PFHooks: LOOPBACK_IN */ ASSERT(tcp->tcp_connp->conn_ire_cache->ire_ipif != NULL); ilp = tcp->tcp_connp->conn_ire_cache->ire_ipif->ipif_ill; if (tcp->tcp_ipversion == IPV4_VERSION) { DTRACE_PROBE4(ip4__loopback__in__start, ill_t *, ilp, ill_t *, NULL, ipha_t *, ipha, mblk_t *, mp1); FW_HOOKS(ipst->ips_ip4_loopback_in_event, ipst->ips_ipv4firewall_loopback_in, ilp, NULL, ipha, mp1, mp1, 0, ipst); DTRACE_PROBE1(ip4__loopback__in__end, mblk_t *, mp1); if (mp1 == NULL) goto unfuse; ip_hdr_len = IPH_HDR_LENGTH(ipha); } else { DTRACE_PROBE4(ip6__loopback__in__start, ill_t *, ilp, ill_t *, NULL, ip6_t *, ip6h, mblk_t *, mp1); FW_HOOKS6(ipst->ips_ip6_loopback_in_event, ipst->ips_ipv6firewall_loopback_in, ilp, NULL, ip6h, mp1, mp1, 0, ipst); DTRACE_PROBE1(ip6__loopback__in__end, mblk_t *, mp1); if (mp1 == NULL) goto unfuse; ip_hdr_len = ip_hdr_length_v6(mp1, ip6h); } /* Data length might be changed by FW_HOOKS */ tcph = (tcph_t *)&mp1->b_rptr[ip_hdr_len]; seq = ABE32_TO_U32(tcph->th_seq); recv_size += seq - tcp->tcp_snxt; /* * The message duplicated by tcp_xmit_mp is freed. * Note: the original message passed in remains unchanged. */ freemsg(mp1); } mutex_enter(&peer_tcp->tcp_non_sq_lock); /* * Wake up and signal the peer; it is okay to do this before * enqueueing because we are holding the lock. One of the * advantages of synchronous streams is the ability for us to * find out when the application performs a read on the socket, * by way of tcp_fuse_rrw() entry point being called. Every * data that gets enqueued onto the receiver is treated as if * it has arrived at the receiving endpoint, thus generating * SIGPOLL/SIGIO for asynchronous socket just as in the strrput() * case. However, we only wake up the application when necessary, * i.e. during the first enqueue. When tcp_fuse_rrw() is called * it will send everything upstream. */ if (peer_tcp->tcp_direct_sockfs && !urgent && !TCP_IS_DETACHED(peer_tcp)) { if (peer_tcp->tcp_rcv_list == NULL) STR_WAKEUP_SET(STREAM(peer_tcp->tcp_rq)); /* Update poll events and send SIGPOLL/SIGIO if necessary */ STR_SENDSIG(STREAM(peer_tcp->tcp_rq)); } /* * Enqueue data into the peer's receive list; we may or may not * drain the contents depending on the conditions below. */ tcp_rcv_enqueue(peer_tcp, mp, recv_size); /* In case it wrapped around and also to keep it constant */ peer_tcp->tcp_rwnd += recv_size; /* * Exercise flow-control when needed; we will get back-enabled * in either tcp_accept_finish(), tcp_unfuse(), or tcp_fuse_rrw(). * If tcp_direct_sockfs is on or if the peer endpoint is detached, * we emulate streams flow control by checking the peer's queue * size and high water mark; otherwise we simply use canputnext() * to decide if we need to stop our flow. * * The outstanding unread data block check does not apply for a * detached receiver; this is to avoid unnecessary blocking of the * sender while the accept is currently in progress and is quite * similar to the regular tcp. */ if (TCP_IS_DETACHED(peer_tcp) || max_unread == 0) max_unread = UINT_MAX; /* * Since we are accessing our tcp_flow_stopped and might modify it, * we need to take tcp->tcp_non_sq_lock. The lock for the highest * address is held first. Dropping peer_tcp->tcp_non_sq_lock should * not be an issue here since we are within the squeue and the peer * won't disappear. */ if (tcp > peer_tcp) { mutex_exit(&peer_tcp->tcp_non_sq_lock); mutex_enter(&tcp->tcp_non_sq_lock); mutex_enter(&peer_tcp->tcp_non_sq_lock); } else { mutex_enter(&tcp->tcp_non_sq_lock); } flow_stopped = tcp->tcp_flow_stopped; if (((peer_tcp->tcp_direct_sockfs || TCP_IS_DETACHED(peer_tcp)) && (peer_tcp->tcp_rcv_cnt >= peer_tcp->tcp_fuse_rcv_hiwater || ++peer_tcp->tcp_fuse_rcv_unread_cnt >= max_unread)) || (!peer_tcp->tcp_direct_sockfs && !TCP_IS_DETACHED(peer_tcp) && !canputnext(peer_tcp->tcp_rq))) { peer_data_queued = B_TRUE; } if (!flow_stopped && (peer_data_queued || (TCP_UNSENT_BYTES(tcp) >= tcp->tcp_xmit_hiwater))) { tcp_setqfull(tcp); flow_stopped = B_TRUE; TCP_STAT(tcps, tcp_fusion_flowctl); DTRACE_PROBE4(tcp__fuse__output__flowctl, tcp_t *, tcp, uint_t, send_size, uint_t, peer_tcp->tcp_rcv_cnt, uint_t, peer_tcp->tcp_fuse_rcv_unread_cnt); } else if (flow_stopped && !peer_data_queued && (TCP_UNSENT_BYTES(tcp) <= tcp->tcp_xmit_lowater)) { tcp_clrqfull(tcp); flow_stopped = B_FALSE; } mutex_exit(&tcp->tcp_non_sq_lock); ipst->ips_loopback_packets++; tcp->tcp_last_sent_len = send_size; /* Need to adjust the following SNMP MIB-related variables */ tcp->tcp_snxt += send_size; tcp->tcp_suna = tcp->tcp_snxt; peer_tcp->tcp_rnxt += recv_size; peer_tcp->tcp_rack = peer_tcp->tcp_rnxt; BUMP_MIB(&tcps->tcps_mib, tcpOutDataSegs); UPDATE_MIB(&tcps->tcps_mib, tcpOutDataBytes, send_size); BUMP_MIB(&tcps->tcps_mib, tcpInSegs); BUMP_MIB(&tcps->tcps_mib, tcpInDataInorderSegs); UPDATE_MIB(&tcps->tcps_mib, tcpInDataInorderBytes, send_size); BUMP_LOCAL(tcp->tcp_obsegs); BUMP_LOCAL(peer_tcp->tcp_ibsegs); mutex_exit(&peer_tcp->tcp_non_sq_lock); DTRACE_PROBE2(tcp__fuse__output, tcp_t *, tcp, uint_t, send_size); if (!TCP_IS_DETACHED(peer_tcp)) { /* * Drain the peer's receive queue it has urgent data or if * we're not flow-controlled. There is no need for draining * normal data when tcp_direct_sockfs is on because the peer * will pull the data via tcp_fuse_rrw(). */ if (urgent || (!flow_stopped && !peer_tcp->tcp_direct_sockfs)) { ASSERT(peer_tcp->tcp_rcv_list != NULL); /* * For TLI-based streams, a thread in tcp_accept_swap() * can race with us. That thread will ensure that the * correct peer_tcp->tcp_rq is globally visible before * peer_tcp->tcp_detached is visible as clear, but we * must also ensure that the load of tcp_rq cannot be * reordered to be before the tcp_detached check. */ membar_consumer(); (void) tcp_fuse_rcv_drain(peer_tcp->tcp_rq, peer_tcp, NULL); /* * If synchronous streams was stopped above due * to the presence of urgent data, re-enable it. */ if (urgent) TCP_FUSE_SYNCSTR_UNPLUG_DRAIN(peer_tcp); } } return (B_TRUE); unfuse: tcp_unfuse(tcp); return (B_FALSE); } /* * This routine gets called to deliver data upstream on a fused or * previously fused tcp loopback endpoint; the latter happens only * when there is a pending SIGURG signal plus urgent data that can't * be sent upstream in the past. */ boolean_t tcp_fuse_rcv_drain(queue_t *q, tcp_t *tcp, mblk_t **sigurg_mpp) { mblk_t *mp; #ifdef DEBUG uint_t cnt = 0; #endif tcp_stack_t *tcps = tcp->tcp_tcps; ASSERT(tcp->tcp_loopback); ASSERT(tcp->tcp_fused || tcp->tcp_fused_sigurg); ASSERT(!tcp->tcp_fused || tcp->tcp_loopback_peer != NULL); ASSERT(sigurg_mpp != NULL || tcp->tcp_fused); /* No need for the push timer now, in case it was scheduled */ if (tcp->tcp_push_tid != 0) { (void) TCP_TIMER_CANCEL(tcp, tcp->tcp_push_tid); tcp->tcp_push_tid = 0; } /* * If there's urgent data sitting in receive list and we didn't * get a chance to send up a SIGURG signal, make sure we send * it first before draining in order to ensure that SIOCATMARK * works properly. */ if (tcp->tcp_fused_sigurg) { /* * sigurg_mpp is normally NULL, i.e. when we're still * fused and didn't get here because of tcp_unfuse(). * In this case try hard to allocate the M_PCSIG mblk. */ if (sigurg_mpp == NULL && (mp = allocb(1, BPRI_HI)) == NULL && (mp = allocb_tryhard(1)) == NULL) { /* Alloc failed; try again next time */ tcp->tcp_push_tid = TCP_TIMER(tcp, tcp_push_timer, MSEC_TO_TICK(tcps->tcps_push_timer_interval)); return (B_TRUE); } else if (sigurg_mpp != NULL) { /* * Use the supplied M_PCSIG mblk; it means we're * either unfused or in the process of unfusing, * and the drain must happen now. */ mp = *sigurg_mpp; *sigurg_mpp = NULL; } ASSERT(mp != NULL); tcp->tcp_fused_sigurg = B_FALSE; /* Send up the signal */ DB_TYPE(mp) = M_PCSIG; *mp->b_wptr++ = (uchar_t)SIGURG; putnext(q, mp); /* * Let the regular tcp_rcv_drain() path handle * draining the data if we're no longer fused. */ if (!tcp->tcp_fused) return (B_FALSE); } /* * In the synchronous streams case, we generate SIGPOLL/SIGIO for * each M_DATA that gets enqueued onto the receiver. At this point * we are about to drain any queued data via putnext(). In order * to avoid extraneous signal generation from strrput(), we set * STRGETINPROG flag at the stream head prior to the draining and * restore it afterwards. This masks out signal generation only * for M_DATA messages and does not affect urgent data. */ if (tcp->tcp_direct_sockfs) strrput_sig(q, B_FALSE); /* Drain the data */ while ((mp = tcp->tcp_rcv_list) != NULL) { tcp->tcp_rcv_list = mp->b_next; mp->b_next = NULL; #ifdef DEBUG cnt += msgdsize(mp); #endif putnext(q, mp); TCP_STAT(tcps, tcp_fusion_putnext); } if (tcp->tcp_direct_sockfs) strrput_sig(q, B_TRUE); ASSERT(cnt == tcp->tcp_rcv_cnt); tcp->tcp_rcv_last_head = NULL; tcp->tcp_rcv_last_tail = NULL; tcp->tcp_rcv_cnt = 0; tcp->tcp_fuse_rcv_unread_cnt = 0; tcp->tcp_rwnd = q->q_hiwat; return (B_TRUE); } /* * Synchronous stream entry point for sockfs to retrieve * data directly from tcp_rcv_list. * tcp_fuse_rrw() might end up modifying the peer's tcp_flow_stopped, * for which it must take the tcp_non_sq_lock of the peer as well * making any change. The order of taking the locks is based on * the TCP pointer itself. Before we get the peer we need to take * our tcp_non_sq_lock so that the peer doesn't disappear. However, * we cannot drop the lock if we have to grab the peer's lock (because * of ordering), since the peer might disappear in the interim. So, * we take our tcp_non_sq_lock, get the peer, increment the ref on the * peer's conn, drop all the locks and then take the tcp_non_sq_lock in the * desired order. Incrementing the conn ref on the peer means that the * peer won't disappear when we drop our tcp_non_sq_lock. */ int tcp_fuse_rrw(queue_t *q, struiod_t *dp) { tcp_t *tcp = Q_TO_CONN(q)->conn_tcp; mblk_t *mp; tcp_t *peer_tcp; tcp_stack_t *tcps = tcp->tcp_tcps; mutex_enter(&tcp->tcp_non_sq_lock); /* * If tcp_fuse_syncstr_plugged is set, then another thread is moving * the underlying data to the stream head. We need to wait until it's * done, then return EBUSY so that strget() will dequeue data from the * stream head to ensure data is drained in-order. */ plugged: if (tcp->tcp_fuse_syncstr_plugged) { do { cv_wait(&tcp->tcp_fuse_plugcv, &tcp->tcp_non_sq_lock); } while (tcp->tcp_fuse_syncstr_plugged); mutex_exit(&tcp->tcp_non_sq_lock); TCP_STAT(tcps, tcp_fusion_rrw_plugged); TCP_STAT(tcps, tcp_fusion_rrw_busy); return (EBUSY); } peer_tcp = tcp->tcp_loopback_peer; /* * If someone had turned off tcp_direct_sockfs or if synchronous * streams is stopped, we return EBUSY. This causes strget() to * dequeue data from the stream head instead. */ if (!tcp->tcp_direct_sockfs || tcp->tcp_fuse_syncstr_stopped) { mutex_exit(&tcp->tcp_non_sq_lock); TCP_STAT(tcps, tcp_fusion_rrw_busy); return (EBUSY); } /* * Grab lock in order. The highest addressed tcp is locked first. * We don't do this within the tcp_rcv_list check since if we * have to drop the lock, for ordering, then the tcp_rcv_list * could change. */ if (peer_tcp > tcp) { CONN_INC_REF(peer_tcp->tcp_connp); mutex_exit(&tcp->tcp_non_sq_lock); mutex_enter(&peer_tcp->tcp_non_sq_lock); mutex_enter(&tcp->tcp_non_sq_lock); /* * This might have changed in the interim * Once read-side tcp_non_sq_lock is dropped above * anything can happen, we need to check all * known conditions again once we reaquire * read-side tcp_non_sq_lock. */ if (tcp->tcp_fuse_syncstr_plugged) { mutex_exit(&peer_tcp->tcp_non_sq_lock); CONN_DEC_REF(peer_tcp->tcp_connp); goto plugged; } if (!tcp->tcp_direct_sockfs || tcp->tcp_fuse_syncstr_stopped) { mutex_exit(&tcp->tcp_non_sq_lock); mutex_exit(&peer_tcp->tcp_non_sq_lock); CONN_DEC_REF(peer_tcp->tcp_connp); TCP_STAT(tcps, tcp_fusion_rrw_busy); return (EBUSY); } CONN_DEC_REF(peer_tcp->tcp_connp); } else { mutex_enter(&peer_tcp->tcp_non_sq_lock); } if ((mp = tcp->tcp_rcv_list) != NULL) { DTRACE_PROBE3(tcp__fuse__rrw, tcp_t *, tcp, uint32_t, tcp->tcp_rcv_cnt, ssize_t, dp->d_uio.uio_resid); tcp->tcp_rcv_list = NULL; TCP_STAT(tcps, tcp_fusion_rrw_msgcnt); /* * At this point nothing should be left in tcp_rcv_list. * The only possible case where we would have a chain of * b_next-linked messages is urgent data, but we wouldn't * be here if that's true since urgent data is delivered * via putnext() and synchronous streams is stopped until * tcp_fuse_rcv_drain() is finished. */ ASSERT(DB_TYPE(mp) == M_DATA && mp->b_next == NULL); tcp->tcp_rcv_last_head = NULL; tcp->tcp_rcv_last_tail = NULL; tcp->tcp_rcv_cnt = 0; tcp->tcp_fuse_rcv_unread_cnt = 0; if (peer_tcp->tcp_flow_stopped && (TCP_UNSENT_BYTES(peer_tcp) <= peer_tcp->tcp_xmit_lowater)) { tcp_clrqfull(peer_tcp); TCP_STAT(tcps, tcp_fusion_backenabled); } } mutex_exit(&peer_tcp->tcp_non_sq_lock); /* * Either we just dequeued everything or we get here from sockfs * and have nothing to return; in this case clear RSLEEP. */ ASSERT(tcp->tcp_rcv_last_head == NULL); ASSERT(tcp->tcp_rcv_last_tail == NULL); ASSERT(tcp->tcp_rcv_cnt == 0); ASSERT(tcp->tcp_fuse_rcv_unread_cnt == 0); STR_WAKEUP_CLEAR(STREAM(q)); mutex_exit(&tcp->tcp_non_sq_lock); dp->d_mp = mp; return (0); } /* * Synchronous stream entry point used by certain ioctls to retrieve * information about or peek into the tcp_rcv_list. */ int tcp_fuse_rinfop(queue_t *q, infod_t *dp) { tcp_t *tcp = Q_TO_CONN(q)->conn_tcp; mblk_t *mp; uint_t cmd = dp->d_cmd; int res = 0; int error = 0; struct stdata *stp = STREAM(q); mutex_enter(&tcp->tcp_non_sq_lock); /* If shutdown on read has happened, return nothing */ mutex_enter(&stp->sd_lock); if (stp->sd_flag & STREOF) { mutex_exit(&stp->sd_lock); goto done; } mutex_exit(&stp->sd_lock); /* * It is OK not to return an answer if tcp_rcv_list is * currently not accessible. */ if (!tcp->tcp_direct_sockfs || tcp->tcp_fuse_syncstr_stopped || tcp->tcp_fuse_syncstr_plugged || (mp = tcp->tcp_rcv_list) == NULL) goto done; if (cmd & INFOD_COUNT) { /* * We have at least one message and * could return only one at a time. */ dp->d_count++; res |= INFOD_COUNT; } if (cmd & INFOD_BYTES) { /* * Return size of all data messages. */ dp->d_bytes += tcp->tcp_rcv_cnt; res |= INFOD_BYTES; } if (cmd & INFOD_FIRSTBYTES) { /* * Return size of first data message. */ dp->d_bytes = msgdsize(mp); res |= INFOD_FIRSTBYTES; dp->d_cmd &= ~INFOD_FIRSTBYTES; } if (cmd & INFOD_COPYOUT) { mblk_t *mp1; int n; if (DB_TYPE(mp) == M_DATA) { mp1 = mp; } else { mp1 = mp->b_cont; ASSERT(mp1 != NULL); } /* * Return data contents of first message. */ ASSERT(DB_TYPE(mp1) == M_DATA); while (mp1 != NULL && dp->d_uiop->uio_resid > 0) { n = MIN(dp->d_uiop->uio_resid, MBLKL(mp1)); if (n != 0 && (error = uiomove((char *)mp1->b_rptr, n, UIO_READ, dp->d_uiop)) != 0) { goto done; } mp1 = mp1->b_cont; } res |= INFOD_COPYOUT; dp->d_cmd &= ~INFOD_COPYOUT; } done: mutex_exit(&tcp->tcp_non_sq_lock); dp->d_res |= res; return (error); } /* * Enable synchronous streams on a fused tcp loopback endpoint. */ static void tcp_fuse_syncstr_enable(tcp_t *tcp) { queue_t *rq = tcp->tcp_rq; struct stdata *stp = STREAM(rq); /* We can only enable synchronous streams for sockfs mode */ tcp->tcp_direct_sockfs = tcp->tcp_issocket && do_tcp_direct_sockfs; if (!tcp->tcp_direct_sockfs) return; mutex_enter(&stp->sd_lock); mutex_enter(QLOCK(rq)); /* * We replace our q_qinfo with one that has the qi_rwp entry point. * Clear SR_SIGALLDATA because we generate the equivalent signal(s) * for every enqueued data in tcp_fuse_output(). */ rq->q_qinfo = &tcp_loopback_rinit; rq->q_struiot = tcp_loopback_rinit.qi_struiot; stp->sd_struiordq = rq; stp->sd_rput_opt &= ~SR_SIGALLDATA; mutex_exit(QLOCK(rq)); mutex_exit(&stp->sd_lock); } /* * Disable synchronous streams on a fused tcp loopback endpoint. */ static void tcp_fuse_syncstr_disable(tcp_t *tcp) { queue_t *rq = tcp->tcp_rq; struct stdata *stp = STREAM(rq); if (!tcp->tcp_direct_sockfs) return; mutex_enter(&stp->sd_lock); mutex_enter(QLOCK(rq)); /* * Reset q_qinfo to point to the default tcp entry points. * Also restore SR_SIGALLDATA so that strrput() can generate * the signals again for future M_DATA messages. */ rq->q_qinfo = &tcp_rinitv4; /* No open - same as rinitv6 */ rq->q_struiot = tcp_rinitv4.qi_struiot; stp->sd_struiordq = NULL; stp->sd_rput_opt |= SR_SIGALLDATA; tcp->tcp_direct_sockfs = B_FALSE; mutex_exit(QLOCK(rq)); mutex_exit(&stp->sd_lock); } /* * Enable synchronous streams on a pair of fused tcp endpoints. */ void tcp_fuse_syncstr_enable_pair(tcp_t *tcp) { tcp_t *peer_tcp = tcp->tcp_loopback_peer; ASSERT(tcp->tcp_fused); ASSERT(peer_tcp != NULL); tcp_fuse_syncstr_enable(tcp); tcp_fuse_syncstr_enable(peer_tcp); } /* * Allow or disallow signals to be generated by strrput(). */ static void strrput_sig(queue_t *q, boolean_t on) { struct stdata *stp = STREAM(q); mutex_enter(&stp->sd_lock); if (on) stp->sd_flag &= ~STRGETINPROG; else stp->sd_flag |= STRGETINPROG; mutex_exit(&stp->sd_lock); } /* * Disable synchronous streams on a pair of fused tcp endpoints and drain * any queued data; called either during unfuse or upon transitioning from * a socket to a stream endpoint due to _SIOCSOCKFALLBACK. */ void tcp_fuse_disable_pair(tcp_t *tcp, boolean_t unfusing) { tcp_t *peer_tcp = tcp->tcp_loopback_peer; tcp_stack_t *tcps = tcp->tcp_tcps; ASSERT(tcp->tcp_fused); ASSERT(peer_tcp != NULL); /* * Force any tcp_fuse_rrw() calls to block until we've moved the data * onto the stream head. */ TCP_FUSE_SYNCSTR_PLUG_DRAIN(tcp); TCP_FUSE_SYNCSTR_PLUG_DRAIN(peer_tcp); /* * Drain any pending data; the detached check is needed because * we may be called as a result of a tcp_unfuse() triggered by * tcp_fuse_output(). Note that in case of a detached tcp, the * draining will happen later after the tcp is unfused. For non- * urgent data, this can be handled by the regular tcp_rcv_drain(). * If we have urgent data sitting in the receive list, we will * need to send up a SIGURG signal first before draining the data. * All of these will be handled by the code in tcp_fuse_rcv_drain() * when called from tcp_rcv_drain(). */ if (!TCP_IS_DETACHED(tcp)) { (void) tcp_fuse_rcv_drain(tcp->tcp_rq, tcp, (unfusing ? &tcp->tcp_fused_sigurg_mp : NULL)); } if (!TCP_IS_DETACHED(peer_tcp)) { (void) tcp_fuse_rcv_drain(peer_tcp->tcp_rq, peer_tcp, (unfusing ? &peer_tcp->tcp_fused_sigurg_mp : NULL)); } /* * Make all current and future tcp_fuse_rrw() calls fail with EBUSY. * To ensure threads don't sneak past the checks in tcp_fuse_rrw(), * a given stream must be stopped prior to being unplugged (but the * ordering of operations between the streams is unimportant). */ TCP_FUSE_SYNCSTR_STOP(tcp); TCP_FUSE_SYNCSTR_STOP(peer_tcp); TCP_FUSE_SYNCSTR_UNPLUG_DRAIN(tcp); TCP_FUSE_SYNCSTR_UNPLUG_DRAIN(peer_tcp); /* Lift up any flow-control conditions */ if (tcp->tcp_flow_stopped) { tcp_clrqfull(tcp); TCP_STAT(tcps, tcp_fusion_backenabled); } if (peer_tcp->tcp_flow_stopped) { tcp_clrqfull(peer_tcp); TCP_STAT(tcps, tcp_fusion_backenabled); } /* Disable synchronous streams */ tcp_fuse_syncstr_disable(tcp); tcp_fuse_syncstr_disable(peer_tcp); } /* * Calculate the size of receive buffer for a fused tcp endpoint. */ size_t tcp_fuse_set_rcv_hiwat(tcp_t *tcp, size_t rwnd) { tcp_stack_t *tcps = tcp->tcp_tcps; ASSERT(tcp->tcp_fused); /* Ensure that value is within the maximum upper bound */ if (rwnd > tcps->tcps_max_buf) rwnd = tcps->tcps_max_buf; /* Obey the absolute minimum tcp receive high water mark */ if (rwnd < tcps->tcps_sth_rcv_hiwat) rwnd = tcps->tcps_sth_rcv_hiwat; /* * Round up to system page size in case SO_RCVBUF is modified * after SO_SNDBUF; the latter is also similarly rounded up. */ rwnd = P2ROUNDUP_TYPED(rwnd, PAGESIZE, size_t); tcp->tcp_fuse_rcv_hiwater = rwnd; return (rwnd); } /* * Calculate the maximum outstanding unread data block for a fused tcp endpoint. */ int tcp_fuse_maxpsz_set(tcp_t *tcp) { tcp_t *peer_tcp = tcp->tcp_loopback_peer; uint_t sndbuf = tcp->tcp_xmit_hiwater; uint_t maxpsz = sndbuf; ASSERT(tcp->tcp_fused); ASSERT(peer_tcp != NULL); ASSERT(peer_tcp->tcp_fuse_rcv_hiwater != 0); /* * In the fused loopback case, we want the stream head to split * up larger writes into smaller chunks for a more accurate flow- * control accounting. Our maxpsz is half of the sender's send * buffer or the receiver's receive buffer, whichever is smaller. * We round up the buffer to system page size due to the lack of * TCP MSS concept in Fusion. */ if (maxpsz > peer_tcp->tcp_fuse_rcv_hiwater) maxpsz = peer_tcp->tcp_fuse_rcv_hiwater; maxpsz = P2ROUNDUP_TYPED(maxpsz, PAGESIZE, uint_t) >> 1; /* * Calculate the peer's limit for the number of outstanding unread * data block. This is the amount of data blocks that are allowed * to reside in the receiver's queue before the sender gets flow * controlled. It is used only in the synchronous streams mode as * a way to throttle the sender when it performs consecutive writes * faster than can be read. The value is derived from SO_SNDBUF in * order to give the sender some control; we divide it with a large * value (16KB) to produce a fairly low initial limit. */ if (tcp_fusion_rcv_unread_min == 0) { /* A value of 0 means that we disable the check */ peer_tcp->tcp_fuse_rcv_unread_hiwater = 0; } else { peer_tcp->tcp_fuse_rcv_unread_hiwater = MAX(sndbuf >> 14, tcp_fusion_rcv_unread_min); } return (maxpsz); }