sundry 4.2 bugs

[RWS%mit-xx at sri-unix.UUCP]

Despite claims to the contrary, the block number sign extension problem still
exists.  Berkeley put in a fix that should have worked, but a C compiler bug
apparently keeps it from working.  In /sys/sys/vm_mem.c in memall() the code
      swapdev : mount[c->c_mdev].m_dev, (daddr_t)(u_long)c->c_blkno
should be changed to
      swapdev : mount[c->c_mdev].m_dev, c->c_blkno
and in /sys/vax/vm_machdep.c in chgprot() the code
          munhash(mount[c->c_mdev].m_dev, (daddr_t)(u_long)c->c_blkno);
should be changed to
          munhash(mount[c->c_mdev].m_dev, c->c_blkno);
because the C compiler apparently incorrectly folds the (daddr_t) and (u_long)
together and sign extends anyway.  Simply taking out the (daddr_t)(u_long)
works, although lint will probably complain about it.

There is a magic number (0x3ffff8) representing USRSTACK/NBPG built in to
Fastreclaim in /sys/vax/locore.s.  However, USRSTACK depends on UPAGES,
so this magic number has UPAGES=8 built in, which is bogus.  If you change
UPAGES, your system will panic: trap.  The fix
is to change
          subl3     P_SSIZE(r5),$0x3ffff8,r0
to
          subl3     P_SSIZE(r5),$(0x400000-UPAGES),r0
and to change
          subl2     $(0x3ffff8+UPAGES),r4
to
          subl2     $0x400000,r4

UDP checksumming is turned off, and with good cause, since bad checksums
are produced on output.  In /sys/netinet/udp_usrreq.c in udp_output(),
the code
          ui->ui_ulen = htons((u_short)ui->ui_len);
should be changed to
          ui->ui_len = htons((u_short)ui->ui_len);
          ui->ui_ulen = ui->ui_len;
Then
          int       udpcksum;
can be changed to
          int       udpcksum = 1;


In /sys/netinet/tcp_input.c in tcp_intput(), the code
                    sbdrop(&so->so_snd, so->so_snd.sb_cc);
                    tp->snd_wnd -= so->so_snd.sb_cc;
should be
                    tp->snd_wnd -= so->so_snd.sb_cc;
                    sbdrop(&so->so_snd, so->so_snd.sb_cc);

In /sys/netinet/tcp_output.c in tcp_output() the code
          if (SEQ_GT(tp->snd_nxt, tp->snd_max))
                    tp->snd_max = tp->snd_nxt;
          if (SEQ_GT(tp->snd_nxt, tp->snd_max) && tp->t_rtt == 0) {
                    tp->t_rtt = 1;
                    tp->t_rtseq = tp->snd_nxt - len;
          }
should be
          if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
                    tp->snd_max = tp->snd_nxt;
                    if (tp->t_rtt == 0) {
                              tp->t_rtt = 1;
                              tp->t_rtseq = tp->snd_nxt - len;
                    }
          }

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