struct imp { /* 1822 long leader */ unchar i_nff; /* new format flag */ unchar i_dnet; /* dest network (unused) */ unchar i_lflgs; /* leader flags */ unchar i_type; /* message type */ unchar i_htype; /* handling type */ unchar i_host; /* host number */ union { /* (to define the imp field) */ n_short i_iw; struct { unchar i_i1; unchar i_i2; } i_ib; #define i_imp I_un.i_iw /* imp field */ #define i_impno I_un.i_ib.i_i2 /* imp number */ #define i_lh I_un.i_ib.i_i1 /* logical host */ } I_un; unchar i_link; /* link number */ unchar i_stype; /* message subtype */ n_short i_mlen; /* message length */ }; /* ifcb flag definitions */ #define IMPTRYING 3 /* # of noops from imp to ignore */ #define IMPENDMSG 4 /* end of message flag */ #define IMPSETTING 8 /* i/f in process of initializing */ #define MTU 1019 /* maximum imp message size (bytes) */ #define IMPWHYDOWN 3 /* host going down subtype mask */