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SOURCEFILTER(3)        FreeBSD Library Functions Manual        SOURCEFILTER(3)

     sourcefilter - advanced multicast group membership API

     #include <sys/socket.h>
     #include <netinet/in.h>

     getipv4sourcefilter(int s, struct in_addr interface,
         struct in_addr group, uint32_t *fmode, uint32_t *numsrc,
         struct in_addr *slist);

     getsourcefilter(int s, uint32_t interface, struct sockaddr *group,
         socklen_t grouplen, uint32_t *fmode, uint32_t *numsrc,
         struct sockaddr_storage *slist);

     setipv4sourcefilter(int s, struct in_addr interface,
         struct in_addr group, uint32_t fmode, uint32_t numsrc,
         struct in_addr *slist);

     setsourcefilter(int s, uint32_t interface, struct sockaddr *group,
         socklen_t grouplen, uint32_t fmode, uint32_t numsrc,
         struct sockaddr_storage *slist);

     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 regardless of
     the IGMP or MLD version in use on the link.

     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 argument 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 unnumbered
     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

     The getsourcefilter(), getipv4sourcefilter(), setsourcefilter(), and
     setipv4sourcefilter() functions return the value 0 if successful;
     otherwise the value -1 is returned and the global variable errno is set
     to indicate the error.

     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 member 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

     [ENOMEM]           Insufficient memory was available to carry out the
                        requested operation.

     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.

     The sourcefilter functions first appeared in FreeBSD 7.0.

     Bruce M. Simpson <>

FreeBSD 11.0-PRERELEASE        February 13, 2009       FreeBSD 11.0-PRERELEASE


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