igmp(4) [freebsd man page]
IGMP(4) BSD Kernel Interfaces Manual IGMP(4) NAME
igmp -- Internet Group Management Protocol SYNOPSIS
#include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <netinet/in_systm.h> #include <netinet/ip.h> #include <netinet/igmp.h> int socket(AF_INET, SOCK_RAW, IPPROTO_IGMP); DESCRIPTION
IGMP is a control plane protocol used by IPv4 hosts and routers to propagate multicast group membership information. Normally this protocol is not used directly, except by the kernel itself, in response to multicast membership requests by user applications. Routing protocols may open a raw socket to directly interact with igmp. As of FreeBSD 8.0, IGMP version 3 is implemented. This adds support for Source-Specific Multicast (SSM), whereby applications may communi- cate to upstream multicast routers that they are only interested in receiving multicast streams from particular sources. SYSCTL VARIABLES
net.inet.igmp.stats This opaque read-only variable exposes the stack-wide IGMPv3 protocol statistics to netstat(1). net.inet.igmp.ifinfo This opaque read-only variable exposes the per-link IGMPv3 status to ifmcstat(8). net.inet.igmp.gsrdelay This variable specifies the time threshold, in seconds, for processing Group-and-Source Specific Queries (GSR). As GSR query pro- cessing requires maintaining state on the host, it may cause memory to be allocated, and is therefore a potential attack point for Denial-of-Service (DoS). If more than one GSR query is received within this threshold, it will be dropped, to mitigate the potential for DoS. net.inet.igmp.default_version This variable controls the default version of IGMP to be used on all links. This sysctl is normally set to 3 by default. net.inet.igmp.legacysupp If this variable is non-zero, then IGMP v1 and v2 membership reports received on a link will be allowed to suppress the IGMP v3 state-change reports which would otherwise be issued by this host. This sysctl is normally enabled by default. net.inet.igmp.v2enable If this variable is non-zero, then IGMP v2 membership queries will be processed by this host, and backwards compatibility will be enabled until the v2 'Old Querier Present' timer expires. This sysctl is normally enabled by default. net.inet.igmp.v1enable If this variable is non-zero, then IGMP v1 membership queries will be processed by this host, and backwards compatibility will be enabled until the v1 'Old Querier Present' timer expires. This sysctl is normally enabled by default. net.inet.igmp.sendlocal If this variable is non-zero, then IGMP state-changes for groups in the 224.0.0.0/24 link-scope prefix will be issued. This behav- iour is recommended if deploying FreeBSD in a network environment with layer 2 devices which snoop IGMP traffic to mitigate multicast propagation throughout the network. This sysctl is normally enabled by default. net.inet.igmp.sendra If this variable is non-zero, then IGMP v2 and v3 reports will contain the IP Router Alert option. This sysctl is normally enabled by default. net.inet.igmp.recvifkludge If this variable is non-zero, then received IGMP reports which contain 0.0.0.0 as their source will be rewritten to contain the sub- net address. This is useful when there are hosts on-link which have not yet been configured with a primary IPv4 address. This sysctl is normally enabled by default. SEE ALSO
netstat(1), sourcefilter(3), inet(4), multicast(4), ifmcstat(8) HISTORY
The igmp manual page re-appeared in FreeBSD 8.0. BSD
March 9, 2009 BSD
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SOURCEFILTER(3) BSD Library Functions Manual SOURCEFILTER(3) NAME
sourcefilter -- advanced multicast group membership API SYNOPSIS
#include <sys/socket.h> #include <netinet/in.h> int getipv4sourcefilter(int s, struct in_addr interface, struct in_addr group, uint32_t *fmode, uint32_t *numsrc, struct in_addr *slist); int getsourcefilter(int s, uint32_t interface, struct sockaddr *group, socklen_t grouplen, uint32_t *fmode, uint32_t *numsrc, struct sockaddr_storage *slist); int setipv4sourcefilter(int s, struct in_addr interface, struct in_addr group, uint32_t fmode, uint32_t numsrc, struct in_addr *slist); int setsourcefilter(int s, uint32_t interface, struct sockaddr *group, socklen_t grouplen, uint32_t fmode, uint32_t numsrc, struct sockaddr_storage *slist); DESCRIPTION
The sourcefilter functions implement the advanced, full-state multicast API defined in RFC 3678. An application may use these functions to atomically set and retrieve the multicast source address filters associated with a socket s and a multicast group. The functions getipv4sourcefilter() and getsourcefilter() allow an application to discover the filter mode, and source filter entries, for an existing group membership. The kernel will always return the number of source filter entries on the socket for that group in *numsrc. If the *numsrc argument is non- zero, the kernel will attempt to return up to *numsrc filter entries in the array pointed to by slist. The *numsrc argument may be set to 0, in which case the slist argument will be ignored. For the setipv4sourcefilter() and setsourcefilter() functions, the fmode argument may be used to place the socket into inclusive or exclusive group membership modes, by using the MCAST_INCLUDE or MCAST_EXCLUDE constants respectively. The numsrc argument specifies the number of source entries in the slist array. If the numsrc argument has a value of 0, all source filters will be removed from the socket. Removing all source filters from a membership which is in the MCAST_INCLUDE filter mode will cause the group to be left on that socket. The protocol-independent function setsourcefilter() allows an application to join a multicast group on an interface which may not have an assigned protocol address, by passing its index for the interface argument. Any changes made by these functions will be communicated to IGMPv3 and/or MLDv2 routers on the local network as appropriate. If no IGMPv3 or MLDv2 routers are present, changes in the source filter lists made by these functions will not cause state changes to be transmitted, with the exception of any change which causes a group to be joined or left. The kernel will continue to maintain the source filter state regard- less of the IGMP or MLD version in use on the link. IMPLEMENTATION NOTES
The IPv4 specific versions of these functions are implemented in terms of the protocol-independent functions. Application writers are encouraged to use the protocol-independent functions for efficiency, and forwards compatibility with IPv6 networks. For the protocol-independent functions getsourcefilter() and setsourcefilter(), the grouplen argument specifies the size of the structure pointed to by group. This is required in order to differentiate between different address families. Currently FreeBSD does not support source address selection for the IPv4 protocol family, therefore the use of multicast APIs with an unnum- bered IPv4 interface is not recommended. In all cases, the first assigned IPv4 address on the interface will be used as the source address of IGMP control traffic. If this address is removed or changed, the results are undefined. RETURN VALUES
The getsourcefilter(), getipv4sourcefilter(), setsourcefilter(), and setipv4sourcefilter() functions return the value 0 if successful; other- wise the value -1 is returned and the global variable errno is set to indicate the error. ERRORS
The sourcefilter functions may fail because of: [EADDRNOTAVAIL] The network interface which the interface argument refers to was not configured in the system, or the system is not a mem- ber of the group. [EAFNOSUPPORT] The group and/or one or more of the slist arguments were of an address family unsupported by the system, or the address family of the group and slist arguments were not identical. [EINVAL] The group argument does not contain a multicast address. The fmode argument is invalid; it must be set to either MCAST_INCLUDE or MCAST_EXCLUDE. The numsrc or slist arguments do not specify a source list. [ENOMEM] Insufficient memory was available to carry out the requested operation. SEE ALSO
ip(4), ip6(4), multicast(4), ifmcstat(8) D. Thaler, B. Fenner, and B. Quinn, Socket Interface Extensions for Multicast Source Filters, RFC 3678, Jan 2004. HISTORY
The sourcefilter functions first appeared in FreeBSD 7.0. AUTHORS
Bruce M. Simpson <bms@FreeBSD.org> BSD
February 13, 2009 BSD