getsourcefilter(3N)getsourcefilter(3N)NAMEgetsourcefilter() - get IP multicast source filter state
This function retrieves the multicast source filter state for an IPv4
or IPv6 multicast group which the application has joined on a given
s Specifies the descriptor identifying the socket. The socket
address family must be or and the socket type must be
interface Holds the interface index of a local interface, or zero. If
set to zero, the system chooses a multicast group by matching
the multicast address only.
group Points to either a sockaddr_in structure (for IPv4) or a
sockaddr_in6 structure (for IPv6) that holds the IP multicast
address of the group.
grouplen Holds the size of the structure pointed to by the group argu‐
fmode Points to an integer that will contain the filter mode on a
successful return. The value of this field will be either or
which are defined in
numsrc On input, the numsrc argument holds the number of source
addresses that will fit in the slist array. On output, the
numsrc argument will hold the total number of sources in the
slist Points to buffer into which an array of sockaddr_storage
structures containing the IP addresses of included or
excluded (depending on the filter mode) sources will be writ‐
ten. The sockaddr_storage structures will contain either a
sockaddr_in structure (for IPv4 addresses) or a sockaddr_in6
structure (for IPv6 addresses, including IPv4-mapped IPv6
addresses); the address family will match that of the group
argument. If numsrc was 0 on input, a NULL pointer may be
If the application does not know the size of the source list before‐
hand, it can make a reasonable guess (for example, by setting numsrc to
0), and if upon completion, numsrc holds a larger value, the operation
can be repeated with a large enough buffer.
That is, on return, numsrc is always updated to be the total number of
sources in the filter, while slist will hold as many source addresses
as fit, up to the minimum of the array size passed in as the original
numsrc value and the total number of sources in the filter.
returns the following values:
is set to indicate the error.
If fails, is set to one of the following values:
The argument s is not a valid descriptor.
This function is not supported by the socket type.
Insufficient memory is available for internal
system data structures.
The address family of the
group argument is not supported.
The specified multicast group has not been joined.
slist is NULL when numsrc is greater than 0; or
group does not contain a multicast
address; or interface contains an invalid
interface index; or grouplen is not valid.
was developed by HP and the IETF.
SEE ALSOsocket(2), getipv4sourcefilter(3N), if_nameindex(3N), setipv4source‐
filter(3N), setsourcefilter(3N), ip(7P), ip6(7P).