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26 .\" $FreeBSD: /repoman/r/ncvs/src/share/man/man4/multicast.4,v 1.1 2003/10/17 15:12:01 bmah Exp $
27 .\" $DragonFly: src/share/man/man4/multicast.4,v 1.3 2006/03/26 22:56:57 swildner Exp $
38 .Cd "options MROUTING"
43 .In netinet/ip_mroute.h
44 .In netinet6/ip6_mroute.h
46 .Fn getsockopt "int s" IPPROTO_IP MRT_INIT "void *optval" "socklen_t *optlen"
48 .Fn setsockopt "int s" IPPROTO_IP MRT_INIT "const void *optval" "socklen_t optlen"
50 .Fn getsockopt "int s" IPPROTO_IPV6 MRT6_INIT "void *optval" "socklen_t *optlen"
52 .Fn setsockopt "int s" IPPROTO_IPV6 MRT6_INIT "const void *optval" "socklen_t optlen"
54 .Tn "Multicast routing"
55 is used to efficiently propagate data
56 packets to a set of multicast listeners in multipoint networks.
57 If unicast is used to replicate the data to all listeners,
58 then some of the network links may carry multiple copies of the same
60 With multicast routing, the overhead is reduced to one copy
61 (at most) per network link.
63 All multicast-capable routers must run a common multicast routing
65 The Distance Vector Multicast Routing Protocol (DVMRP)
66 was the first developed multicast routing protocol.
67 Later, other protocols such as Multicast Extensions to OSPF (MOSPF),
68 Core Based Trees (CBT),
69 Protocol Independent Multicast - Sparse Mode (PIM-SM),
70 and Protocol Independent Multicast - Dense Mode (PIM-DM)
71 were developed as well.
73 To start multicast routing,
74 the user must enable multicast forwarding in the kernel
77 about the kernel configuration options),
78 and must run a multicast routing capable user-level process.
79 From developer's point of view,
80 the programming guide described in the
81 .Sx "Programming Guide"
82 section should be used to control the multicast forwarding in the kernel.
85 This section provides information about the basic multicast routing API.
87 .Dq advanced multicast API
89 .Sx "Advanced Multicast API Programming Guide"
92 First, a multicast routing socket must be open.
93 That socket would be used
94 to control the multicast forwarding in the kernel.
95 Note that most operations below require certain privilege
96 (i.e., root privilege):
101 mrouter_s4 = socket(AF_INET, SOCK_RAW, IPPROTO_IGMP);
106 mrouter_s6 = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);
109 Note that if the router needs to open an IGMP or ICMPv6 socket
110 (in case of IPv4 and IPv6 respectively)
111 for sending or receiving of IGMP or MLD multicast group membership messages,
112 then the same mrouter_s4 or mrouter_s6 sockets should be used
113 for sending and receiving respectively IGMP or MLD messages.
114 In case of BSD-derived kernel, it may be possible to open separate sockets
115 for IGMP or MLD messages only.
116 However, some other kernels (e.g., Linux) require that the multicast
117 routing socket must be used for sending and receiving of IGMP or MLD
119 Therefore, for portability reason the multicast
120 routing socket should be reused for IGMP and MLD messages as well.
122 After the multicast routing socket is open, it can be used to enable
123 or disable multicast forwarding in the kernel:
126 int v = 1; /* 1 to enable, or 0 to disable */
127 setsockopt(mrouter_s4, IPPROTO_IP, MRT_INIT, (void *)&v, sizeof(v));
132 int v = 1; /* 1 to enable, or 0 to disable */
133 setsockopt(mrouter_s6, IPPROTO_IPV6, MRT6_INIT, (void *)&v, sizeof(v));
135 /* If necessary, filter all ICMPv6 messages */
136 struct icmp6_filter filter;
137 ICMP6_FILTER_SETBLOCKALL(&filter);
138 setsockopt(mrouter_s6, IPPROTO_ICMPV6, ICMP6_FILTER, (void *)&filter,
142 After multicast forwarding is enabled, the multicast routing socket
143 can be used to enable PIM processing in the kernel if we are running PIM-SM or
148 For each network interface (e.g., physical or a virtual tunnel)
149 that would be used for multicast forwarding, a corresponding
150 multicast interface must be added to the kernel:
154 memset(&vc, 0, sizeof(vc));
155 /* Assign all vifctl fields as appropriate */
156 vc.vifc_vifi = vif_index;
157 vc.vifc_flags = vif_flags;
158 vc.vifc_threshold = min_ttl_threshold;
159 vc.vifc_rate_limit = max_rate_limit;
160 memcpy(&vc.vifc_lcl_addr, &vif_local_address, sizeof(vc.vifc_lcl_addr));
161 if (vc.vifc_flags & VIFF_TUNNEL)
162 memcpy(&vc.vifc_rmt_addr, &vif_remote_address,
163 sizeof(vc.vifc_rmt_addr));
164 setsockopt(mrouter_s4, IPPROTO_IP, MRT_ADD_VIF, (void *)&vc,
170 must be unique per vif.
175 flags as defined in <netinet/ip_mroute.h>.
177 .Dq min_ttl_threshold
178 contains the minimum TTL a multicast data packet must have to be
179 forwarded on that vif.
180 Typically, it would have value of 1.
183 contains the maximum rate (in bits/s) of the multicast data packets forwarded
185 Value of 0 means no limit.
187 .Dq vif_local_address
188 contains the local IP address of the corresponding local interface.
190 .Dq vif_remote_address
191 contains the remote IP address in case of DVMRP multicast tunnels.
196 memset(&mc, 0, sizeof(mc));
197 /* Assign all mif6ctl fields as appropriate */
198 mc.mif6c_mifi = mif_index;
199 mc.mif6c_flags = mif_flags;
200 mc.mif6c_pifi = pif_index;
201 setsockopt(mrouter_s6, IPPROTO_IPV6, MRT6_ADD_MIF, (void *)&mc,
207 must be unique per vif.
212 flags as defined in <netinet6/ip6_mroute.h>.
215 is the physical interface index of the corresponding local interface.
217 A multicast interface is deleted by:
220 vifi_t vifi = vif_index;
221 setsockopt(mrouter_s4, IPPROTO_IP, MRT_DEL_VIF, (void *)&vifi,
227 mifi_t mifi = mif_index;
228 setsockopt(mrouter_s6, IPPROTO_IPV6, MRT6_DEL_MIF, (void *)&mifi,
232 After the multicast forwarding is enabled, and the multicast virtual
234 added, the kernel may deliver upcall messages (also called signals
235 later in this text) on the multicast routing socket that was open
240 The IPv4 upcalls have
242 header (see <netinet/ip_mroute.h>) with field
245 Note that this header follows the structure of
247 with the protocol field
250 The IPv6 upcalls have
252 header (see <netinet6/ip6_mroute.h>) with field
255 Note that this header follows the structure of
257 with the next header field
261 The upcall header contains field
265 with the type of the upcall
269 for IPv4 and IPv6 respectively.
270 The values of the rest of the upcall header fields
271 and the body of the upcall message depend on the particular upcall type.
273 If the upcall message type is
276 .Dq MRT6MSG_NOCACHE ,
277 this is an indication that a multicast packet has reached the multicast
278 router, but the router has no forwarding state for that packet.
279 Typically, the upcall would be a signal for the multicast routing
280 user-level process to install the appropriate Multicast Forwarding
281 Cache (MFC) entry in the kernel.
283 A MFC entry is added by:
287 memset(&mc, 0, sizeof(mc));
288 memcpy(&mc.mfcc_origin, &source_addr, sizeof(mc.mfcc_origin));
289 memcpy(&mc.mfcc_mcastgrp, &group_addr, sizeof(mc.mfcc_mcastgrp));
290 mc.mfcc_parent = iif_index;
291 for (i = 0; i < maxvifs; i++)
292 mc.mfcc_ttls[i] = oifs_ttl[i];
293 setsockopt(mrouter_s4, IPPROTO_IP, MRT_ADD_MFC,
294 (void *)&mc, sizeof(mc));
300 memset(&mc, 0, sizeof(mc));
301 memcpy(&mc.mf6cc_origin, &source_addr, sizeof(mc.mf6cc_origin));
302 memcpy(&mc.mf6cc_mcastgrp, &group_addr, sizeof(mf6cc_mcastgrp));
303 mc.mf6cc_parent = iif_index;
304 for (i = 0; i < maxvifs; i++)
306 IF_SET(i, &mc.mf6cc_ifset);
307 setsockopt(mrouter_s4, IPPROTO_IPV6, MRT6_ADD_MFC,
308 (void *)&mc, sizeof(mc));
315 are the source and group address of the multicast packet (as set
316 in the upcall message).
319 is the virtual interface index of the multicast interface the multicast
320 packets for this specific source and group address should be received on.
323 array contains the minimum TTL (per interface) a multicast packet
324 should have to be forwarded on an outgoing interface.
325 If the TTL value is zero, the corresponding interface is not included
326 in the set of outgoing interfaces.
327 Note that in case of IPv6 only the set of outgoing interfaces can
330 A MFC entry is deleted by:
334 memset(&mc, 0, sizeof(mc));
335 memcpy(&mc.mfcc_origin, &source_addr, sizeof(mc.mfcc_origin));
336 memcpy(&mc.mfcc_mcastgrp, &group_addr, sizeof(mc.mfcc_mcastgrp));
337 setsockopt(mrouter_s4, IPPROTO_IP, MRT_DEL_MFC,
338 (void *)&mc, sizeof(mc));
344 memset(&mc, 0, sizeof(mc));
345 memcpy(&mc.mf6cc_origin, &source_addr, sizeof(mc.mf6cc_origin));
346 memcpy(&mc.mf6cc_mcastgrp, &group_addr, sizeof(mf6cc_mcastgrp));
347 setsockopt(mrouter_s4, IPPROTO_IPV6, MRT6_DEL_MFC,
348 (void *)&mc, sizeof(mc));
351 The following method can be used to get various statistics per
352 installed MFC entry in the kernel (e.g., the number of forwarded
353 packets per source and group address):
356 struct sioc_sg_req sgreq;
357 memset(&sgreq, 0, sizeof(sgreq));
358 memcpy(&sgreq.src, &source_addr, sizeof(sgreq.src));
359 memcpy(&sgreq.grp, &group_addr, sizeof(sgreq.grp));
360 ioctl(mrouter_s4, SIOCGETSGCNT, &sgreq);
365 struct sioc_sg_req6 sgreq;
366 memset(&sgreq, 0, sizeof(sgreq));
367 memcpy(&sgreq.src, &source_addr, sizeof(sgreq.src));
368 memcpy(&sgreq.grp, &group_addr, sizeof(sgreq.grp));
369 ioctl(mrouter_s6, SIOCGETSGCNT_IN6, &sgreq);
372 The following method can be used to get various statistics per
373 multicast virtual interface in the kernel (e.g., the number of forwarded
374 packets per interface):
377 struct sioc_vif_req vreq;
378 memset(&vreq, 0, sizeof(vreq));
379 vreq.vifi = vif_index;
380 ioctl(mrouter_s4, SIOCGETVIFCNT, &vreq);
385 struct sioc_mif_req6 mreq;
386 memset(&mreq, 0, sizeof(mreq));
387 mreq.mifi = vif_index;
388 ioctl(mrouter_s6, SIOCGETMIFCNT_IN6, &mreq);
390 .Ss Advanced Multicast API Programming Guide
391 If we want to add new features in the kernel, it becomes difficult
392 to preserve backward compatibility (binary and API),
393 and at the same time to allow user-level processes to take advantage of
394 the new features (if the kernel supports them).
396 One of the mechanisms that allows us to preserve the backward
397 compatibility is a sort of negotiation
398 between the user-level process and the kernel:
401 The user-level process tries to enable in the kernel the set of new
402 features (and the corresponding API) it would like to use.
404 The kernel returns the (sub)set of features it knows about
405 and is willing to be enabled.
407 The user-level process uses only that set of features
408 the kernel has agreed on.
412 To support backward compatibility, if the user-level process doesn't
413 ask for any new features, the kernel defaults to the basic
414 multicast API (see the
415 .Sx "Programming Guide"
417 .\" XXX: edit as appropriate after the advanced multicast API is
418 .\" supported under IPv6
419 Currently, the advanced multicast API exists only for IPv4;
420 in the future there will be IPv6 support as well.
422 Below is a summary of the expandable API solution.
423 Note that all new options and structures are defined
424 in <netinet/ip_mroute.h> and <netinet6/ip6_mroute.h>,
425 unless stated otherwise.
427 The user-level process uses new get/setsockopt() options to
428 perform the API features negotiation with the kernel.
429 This negotiation must be performed right after the multicast routing
431 The set of desired/allowed features is stored in a bitset
432 (currently, in uint32_t; i.e., maximum of 32 new features).
433 The new get/setsockopt() options are
440 getsockopt(sock, IPPROTO_IP, MRT_API_SUPPORT, (void *)&v, sizeof(v));
445 the pre-defined bits that the kernel API supports.
446 The eight least significant bits in uint32_t are same as the
451 as part of the new definition of
453 (see below about those flags), which leaves 24 flags for other new features.
454 The value returned by getsockopt(MRT_API_SUPPORT) is read-only; in other
455 words, setsockopt(MRT_API_SUPPORT) would fail.
457 To modify the API, and to set some specific feature in the kernel, then:
459 uint32_t v = MRT_MFC_FLAGS_DISABLE_WRONGVIF;
460 if (setsockopt(sock, IPPROTO_IP, MRT_API_CONFIG, (void *)&v, sizeof(v))
464 if (v & MRT_MFC_FLAGS_DISABLE_WRONGVIF)
465 return (OK); /* Success */
470 In other words, when setsockopt(MRT_API_CONFIG) is called, the
471 argument to it specifies the desired set of features to
472 be enabled in the API and the kernel.
475 is the actual (sub)set of features that were enabled in the kernel.
476 To obtain later the same set of features that were enabled, then:
478 getsockopt(sock, IPPROTO_IP, MRT_API_CONFIG, (void *)&v, sizeof(v));
481 The set of enabled features is global.
482 In other words, setsockopt(MRT_API_CONFIG)
483 should be called right after setsockopt(MRT_INIT).
485 Currently, the following set of new features is defined:
487 #define MRT_MFC_FLAGS_DISABLE_WRONGVIF (1 << 0) /* disable WRONGVIF signals */
488 #define MRT_MFC_FLAGS_BORDER_VIF (1 << 1) /* border vif */
489 #define MRT_MFC_RP (1 << 8) /* enable RP address */
490 #define MRT_MFC_BW_UPCALL (1 << 9) /* enable bw upcalls */
493 .\" In the future there might be:
495 .\" #define MRT_MFC_GROUP_SPECIFIC (1 << 10) /* allow (*,G) MFC entries */
498 .\" to allow (*,G) MFC entries (i.e., group-specific entries) in the kernel.
499 .\" For now this is left-out until it is clear whether
500 .\" (*,G) MFC support is the preferred solution instead of something more generic
501 .\" solution for example.
503 .\" 2. The newly defined struct mfcctl2.
506 The advanced multicast API uses a newly defined
508 instead of the traditional
518 * The new argument structure for MRT_ADD_MFC and MRT_DEL_MFC overlays
519 * and extends the old struct mfcctl.
522 /* the mfcctl fields */
523 struct in_addr mfcc_origin; /* ip origin of mcasts */
524 struct in_addr mfcc_mcastgrp; /* multicast group associated*/
525 vifi_t mfcc_parent; /* incoming vif */
526 u_char mfcc_ttls[MAXVIFS];/* forwarding ttls on vifs */
528 /* extension fields */
529 uint8_t mfcc_flags[MAXVIFS];/* the MRT_MFC_FLAGS_* flags*/
530 struct in_addr mfcc_rp; /* the RP address */
535 .Dq mfcc_flags[MAXVIFS]
538 Note that for compatibility reasons they are added at the end.
541 .Dq mfcc_flags[MAXVIFS]
542 field is used to set various flags per
543 interface per (S,G) entry.
544 Currently, the defined flags are:
546 #define MRT_MFC_FLAGS_DISABLE_WRONGVIF (1 << 0) /* disable WRONGVIF signals */
547 #define MRT_MFC_FLAGS_BORDER_VIF (1 << 1) /* border vif */
551 .Dq MRT_MFC_FLAGS_DISABLE_WRONGVIF
552 flag is used to explicitly disable the
554 kernel signal at the (S,G) granularity if a multicast data packet
555 arrives on the wrong interface.
556 Usually, this signal is used to
557 complete the shortest-path switch in case of PIM-SM multicast routing,
558 or to trigger a PIM assert message.
559 However, it should not be delivered for interfaces that are not in
560 the outgoing interface set, and that are not expecting to
561 become an incoming interface.
563 .Dq MRT_MFC_FLAGS_DISABLE_WRONGVIF
564 flag is set for some of the
565 interfaces, then a data packet that arrives on that interface for
566 that MFC entry will NOT trigger a WRONGVIF signal.
567 If that flag is not set, then a signal is triggered (the default action).
570 .Dq MRT_MFC_FLAGS_BORDER_VIF
571 flag is used to specify whether the Border-bit in PIM
572 Register messages should be set (in case when the Register encapsulation
573 is performed inside the kernel).
574 If it is set for the special PIM Register kernel virtual interface
577 the Border-bit in the Register messages sent to the RP will be set.
579 The remaining six bits are reserved for future usage.
583 field is used to specify the RP address (in case of PIM-SM multicast routing)
585 group G if we want to perform kernel-level PIM Register encapsulation.
588 field is used only if the
590 advanced API flag/capability has been successfully set by
591 setsockopt(MRT_API_CONFIG).
594 .\" 3. Kernel-level PIM Register encapsulation
598 flag was successfully set by
599 setsockopt(MRT_API_CONFIG), then the kernel will attempt to perform
600 the PIM Register encapsulation itself instead of sending the
601 multicast data packets to user level (inside IGMPMSG_WHOLEPKT
602 upcalls) for user-level encapsulation.
603 The RP address would be taken from the
610 flag was successfully set, if the
615 kernel will still deliver an IGMPMSG_WHOLEPKT upcall with the
616 multicast data packet to the user-level process.
618 In addition, if the multicast data packet is too large to fit within
619 a single IP packet after the PIM Register encapsulation (e.g., if
620 its size was on the order of 65500 bytes), the data packet will be
621 fragmented, and then each of the fragments will be encapsulated
623 Note that typically a multicast data packet can be that
624 large only if it was originated locally from the same hosts that
625 performs the encapsulation; otherwise the transmission of the
626 multicast data packet over Ethernet for example would have
627 fragmented it into much smaller pieces.
629 .\" Note that if this code is ported to IPv6, we may need the kernel to
630 .\" perform MTU discovery to the RP, and keep those discoveries inside
631 .\" the kernel so the encapsulating router may send back ICMP
632 .\" Fragmentation Required if the size of the multicast data packet is
633 .\" too large (see "Encapsulating data packets in the Register Tunnel"
634 .\" in Section 4.4.1 in the PIM-SM spec
635 .\" draft-ietf-pim-sm-v2-new-05.{txt,ps}).
636 .\" For IPv4 we may be able to get away without it, but for IPv6 we need
639 .\" 4. Mechanism for "multicast bandwidth monitoring and upcalls".
642 Typically, a multicast routing user-level process would need to know the
643 forwarding bandwidth for some data flow.
644 For example, the multicast routing process may want to timeout idle MFC
645 entries, or in case of PIM-SM it can initiate (S,G) shortest-path switch if
646 the bandwidth rate is above a threshold for example.
648 The original solution for measuring the bandwidth of a dataflow was
649 that a user-level process would periodically
650 query the kernel about the number of forwarded packets/bytes per
651 (S,G), and then based on those numbers it would estimate whether a source
652 has been idle, or whether the source's transmission bandwidth is above a
654 That solution is far from being scalable, hence the need for a new
655 mechanism for bandwidth monitoring.
657 Below is a description of the bandwidth monitoring mechanism.
660 If the bandwidth of a data flow satisfies some pre-defined filter,
661 the kernel delivers an upcall on the multicast routing socket
662 to the multicast routing process that has installed that filter.
664 The bandwidth-upcall filters are installed per (S,G). There can be
665 more than one filter per (S,G).
667 Instead of supporting all possible comparison operations
668 (i.e., < <= == != > >= ), there is support only for the
669 <= and >= operations,
670 because this makes the kernel-level implementation simpler,
671 and because practically we need only those two.
672 Further, the missing operations can be simulated by secondary
673 user-level filtering of those <= and >= filters.
674 For example, to simulate !=, then we need to install filter
675 .Dq bw <= 0xffffffff ,
677 upcall is received, we need to check whether
678 .Dq measured_bw != expected_bw .
680 The bandwidth-upcall mechanism is enabled by
681 setsockopt(MRT_API_CONFIG) for the MRT_MFC_BW_UPCALL flag.
683 The bandwidth-upcall filters are added/deleted by the new
684 setsockopt(MRT_ADD_BW_UPCALL) and setsockopt(MRT_DEL_BW_UPCALL)
685 respectively (with the appropriate
690 From application point of view, a developer needs to know about
694 * Structure for installing or delivering an upcall if the
695 * measured bandwidth is above or below a threshold.
697 * User programs (e.g. daemons) may have a need to know when the
698 * bandwidth used by some data flow is above or below some threshold.
699 * This interface allows the userland to specify the threshold (in
700 * bytes and/or packets) and the measurement interval. Flows are
701 * all packet with the same source and destination IP address.
702 * At the moment the code is only used for multicast destinations
703 * but there is nothing that prevents its use for unicast.
705 * The measurement interval cannot be shorter than some Tmin (currently, 3s).
706 * The threshold is set in packets and/or bytes per_interval.
708 * Measurement works as follows:
710 * For >= measurements:
711 * The first packet marks the start of a measurement interval.
712 * During an interval we count packets and bytes, and when we
713 * pass the threshold we deliver an upcall and we are done.
714 * The first packet after the end of the interval resets the
715 * count and restarts the measurement.
717 * For <= measurement:
718 * We start a timer to fire at the end of the interval, and
719 * then for each incoming packet we count packets and bytes.
720 * When the timer fires, we compare the value with the threshold,
721 * schedule an upcall if we are below, and restart the measurement
722 * (reschedule timer and zero counters).
726 struct timeval b_time;
732 struct in_addr bu_src; /* source address */
733 struct in_addr bu_dst; /* destination address */
734 uint32_t bu_flags; /* misc flags (see below) */
735 #define BW_UPCALL_UNIT_PACKETS (1 << 0) /* threshold (in packets) */
736 #define BW_UPCALL_UNIT_BYTES (1 << 1) /* threshold (in bytes) */
737 #define BW_UPCALL_GEQ (1 << 2) /* upcall if bw >= threshold */
738 #define BW_UPCALL_LEQ (1 << 3) /* upcall if bw <= threshold */
739 #define BW_UPCALL_DELETE_ALL (1 << 4) /* delete all upcalls for s,d*/
740 struct bw_data bu_threshold; /* the bw threshold */
741 struct bw_data bu_measured; /* the measured bw */
744 /* max. number of upcalls to deliver together */
745 #define BW_UPCALLS_MAX 128
746 /* min. threshold time interval for bandwidth measurement */
747 #define BW_UPCALL_THRESHOLD_INTERVAL_MIN_SEC 3
748 #define BW_UPCALL_THRESHOLD_INTERVAL_MIN_USEC 0
753 structure is used as an argument to
754 setsockopt(MRT_ADD_BW_UPCALL) and setsockopt(MRT_DEL_BW_UPCALL).
755 Each setsockopt(MRT_ADD_BW_UPCALL) installs a filter in the kernel
756 for the source and destination address in the
759 and that filter will trigger an upcall according to the following
762 if (bw_upcall_oper IS ">=") {
763 if (((bw_upcall_unit & PACKETS == PACKETS) &&
764 (measured_packets >= threshold_packets)) ||
765 ((bw_upcall_unit & BYTES == BYTES) &&
766 (measured_bytes >= threshold_bytes)))
767 SEND_UPCALL("measured bandwidth is >= threshold");
769 if (bw_upcall_oper IS "<=" && measured_interval >= threshold_interval) {
770 if (((bw_upcall_unit & PACKETS == PACKETS) &&
771 (measured_packets <= threshold_packets)) ||
772 ((bw_upcall_unit & BYTES == BYTES) &&
773 (measured_bytes <= threshold_bytes)))
774 SEND_UPCALL("measured bandwidth is <= threshold");
780 the unit can be specified in both BYTES and PACKETS.
781 However, the GEQ and LEQ flags are mutually exclusive.
783 Basically, an upcall is delivered if the measured bandwidth is >= or
784 <= the threshold bandwidth (within the specified measurement
786 For practical reasons, the smallest value for the measurement
787 interval is 3 seconds.
788 If smaller values are allowed, then the bandwidth
789 estimation may be less accurate, or the potentially very high frequency
790 of the generated upcalls may introduce too much overhead.
791 For the >= operation, the answer may be known before the end of
792 .Dq threshold_interval ,
793 therefore the upcall may be delivered earlier.
794 For the <= operation however, we must wait
795 until the threshold interval has expired to know the answer.
799 struct bw_upcall bw_upcall;
800 /* Assign all bw_upcall fields as appropriate */
801 memset(&bw_upcall, 0, sizeof(bw_upcall));
802 memcpy(&bw_upcall.bu_src, &source, sizeof(bw_upcall.bu_src));
803 memcpy(&bw_upcall.bu_dst, &group, sizeof(bw_upcall.bu_dst));
804 bw_upcall.bu_threshold.b_data = threshold_interval;
805 bw_upcall.bu_threshold.b_packets = threshold_packets;
806 bw_upcall.bu_threshold.b_bytes = threshold_bytes;
807 if (is_threshold_in_packets)
808 bw_upcall.bu_flags |= BW_UPCALL_UNIT_PACKETS;
809 if (is_threshold_in_bytes)
810 bw_upcall.bu_flags |= BW_UPCALL_UNIT_BYTES;
813 bw_upcall.bu_flags |= BW_UPCALL_GEQ;
817 bw_upcall.bu_flags |= BW_UPCALL_LEQ;
822 setsockopt(mrouter_s4, IPPROTO_IP, MRT_ADD_BW_UPCALL,
823 (void *)&bw_upcall, sizeof(bw_upcall));
826 To delete a single filter, then use MRT_DEL_BW_UPCALL,
827 and the fields of bw_upcall must be set
828 exactly same as when MRT_ADD_BW_UPCALL was called.
830 To delete all bandwidth filters for a given (S,G), then
837 need to be set, and then just set only the
838 .Dq BW_UPCALL_DELETE_ALL
840 .Dq bw_upcall.bu_flags .
842 The bandwidth upcalls are received by aggregating them in the new upcall
845 #define IGMPMSG_BW_UPCALL 4 /* BW monitoring upcall */
848 This message is an array of
850 elements (up to BW_UPCALLS_MAX = 128).
852 delivered when there are 128 pending upcalls, or when 1 second has
853 expired since the previous upcall (whichever comes first).
858 field is filled-in to
859 indicate the particular measured values.
860 However, because of the way
861 the particular intervals are measured, the user should be careful how
862 bu_measured.b_time is used.
864 filter is installed to trigger an upcall if the number of packets
867 may have a value of zero in the upcalls after the
868 first one, because the measured interval for >= filters is
870 by the forwarded packets.
871 Hence, this upcall mechanism should not be used for measuring
872 the exact value of the bandwidth of the forwarded data.
873 To measure the exact bandwidth, the user would need to
874 get the forwarded packets statistics with the ioctl(SIOCGETSGCNT)
877 .Sx Programming Guide
880 Note that the upcalls for a filter are delivered until the specific
881 filter is deleted, but no more frequently than once per
882 .Dq bu_threshold.b_time .
883 For example, if the filter is specified to
884 deliver a signal if bw >= 1 packet, the first packet will trigger a
885 signal, but the next upcall will be triggered no earlier than
886 .Dq bu_threshold.b_time
887 after the previous upcall.
904 The original multicast code was written by David Waitzman (BBN Labs),
905 and later modified by the following individuals:
906 Steve Deering (Stanford), Mark J. Steiglitz (Stanford),
907 Van Jacobson (LBL), Ajit Thyagarajan (PARC),
909 The IPv6 multicast support was implemented by the KAME project
910 (http://www.kame.net), and was based on the IPv4 multicast code.
911 The advanced multicast API and the multicast bandwidth
912 monitoring were implemented by Pavlin Radoslavov (ICSI)
913 in collaboration with Chris Brown (NextHop).
915 This manual page was written by Pavlin Radoslavov (ICSI).