Fix poll() on half-closed sockets, while retaining POLLHUP for fifos.

This reverts part of r196460, so that sockets only return POLLHUP if both
directions are closed/error. Fifos get POLLHUP by closing the unused
direction immediately after creating the sockets.

The tools/regression/poll/*poll.c tests now pass except for two other things:
- if POLLHUP is returned, POLLIN is always returned as well instead of only
  when there is data left in the buffer to be read
- fifo old/new reader distinction does not work the way POSIX specs it

Reviewed by:	kib, bde

1 files changed, 7 insertions, 5 deletions

diff --git a/sys/kern/uipc_socket.c b/sys/kern/uipc_socket.c
index c60b8d1..2f4dd92 100644
--- a/sys/kern/uipc_socket.c
+++ b/sys/kern/uipc_socket.c
@@ -2898,11 +2898,13 @@ sopoll_generic(struct socket *so, int events, struct ucred *active_cred,
 		if (so->so_oobmark || (so->so_rcv.sb_state & SBS_RCVATMARK))
 			revents |= events & (POLLPRI | POLLRDBAND);
 
-	if ((events & POLLINIGNEOF) == 0)
-		if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
-			revents |= POLLHUP;
-	if (so->so_snd.sb_state & SBS_CANTSENDMORE)
-		revents |= POLLHUP;
+	if ((events & POLLINIGNEOF) == 0) {
+		if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
+			revents |= events & (POLLIN | POLLRDNORM);
+			if (so->so_snd.sb_state & SBS_CANTSENDMORE)
+				revents |= POLLHUP;
+		}
+	}
 
 	if (revents == 0) {
 		if (events & (POLLIN | POLLPRI | POLLRDNORM | POLLRDBAND)) {