#define group_ptr(p, l) ((igmp_membership_group_v3_t *)((u8*)(p) + (l)))
#define group_cptr(p, l) ((const igmp_membership_group_v3_t *)((u8*)(p) + (l)))
#define group_ptr(p, l) ((igmp_membership_group_v3_t *)((u8*)(p) + (l)))
#define group_cptr(p, l) ((const igmp_membership_group_v3_t *)((u8*)(p) + (l)))