IGMP header

The macro IGMP_HDR builds an IGMP header, as defined in [RFC2236]. The macro IGMP_PCK prepends an IPv4 header to the IGMP header.

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The default value for $igmp_type (0x11) is the type code for an IGMP membership query message.

Note that $igmp_group is of type ``IPv4 address''.

Example:

#define MC_ALL_ROUTERS 224.0.0.2

send IGMP_PCK($igmp_type=IGMP_V1_MEMBERSHIP_REPORT
  $igmp_group=MC_ALL_ROUTERS)