session_groups
RB_FOREACH(sg, session_groups, &session_groups) {
struct session_groups session_groups = RB_INITIALIZER(&session_groups);
RB_FOREACH(sg, session_groups, &session_groups) {
RB_GENERATE(session_groups, session_group, entry, session_group_cmp);
return (RB_FIND(session_groups, &session_groups, &sg));
RB_INSERT(session_groups, &session_groups, sg);
RB_REMOVE(session_groups, &session_groups, sg);
RB_HEAD(session_groups, session_group);
extern struct session_groups session_groups;