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IGMP(4) 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 propa- gate multicast group membership information. Normally this protocol is not used directly, except by the kernel itself, in response to multicast mem- bership 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 communicate to upstream multicast routers that they are only interested in receiving mul- ticast streams from particular sources. SYSCTL VARIABLES net.inet.igmp.stats This opaque read-only variable exposes the stack-wide IGMPv3 proto- col 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 pro- cessing 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 De- nial-of-Service (DoS). If more than one GSR query is received within this threshold, it will be dropped, to mitigate the poten- tial 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 re- ports 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 en- abled 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 en- abled 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 behaviour 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 en- abled by default. net.inet.igmp.sendra If this variable is non-zero, then IGMP v2 and v3 reports will con- tain 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 con- tain 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. FreeBSD ports 15.quarterly March 9, 2009 IGMP(4)
NAME | SYNOPSIS | DESCRIPTION | SYSCTL VARIABLES | SEE ALSO | HISTORY
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