linking fails with the message:
lpd.o: Undefined symbol ___ivaliduser referenced from text segment

There is a _validuser() in libc/net/rcmd.c, which seems to fit the
bill.  The follwing patch allows a clean link.

*** lpd.c       Fri May 20 13:11:47 1994
--- lpd.c-orig  Wed May 18 13:11:01 1994
***************
*** 478,484 ****
	hostf = fopen(_PATH_HOSTSEQUIV, "r");
  again:
	if (hostf) {
!               if (_validuser(hostf, f->sin_addr.s_addr,
		    DUMMY, DUMMY) == 0) {
			(void) fclose(hostf);
			return;
--- 478,484 ----
	hostf = fopen(_PATH_HOSTSEQUIV, "r");
  again:
	if (hostf) {
!               if (__ivaliduser(hostf, f->sin_addr.s_addr,
		    DUMMY, DUMMY) == 0) {
			(void) fclose(hostf);
			return;

------------------------------------------------------------------------------