slirp: switch to GPollFD

Slirp uses rfds/wfds/xfds more extensively than other QEMU components.

The rarely-used out-of-band TCP data feature is used.  That means we
need the full table of select(2) to g_poll(3) events:

  rfds -> G_IO_IN | G_IO_HUP | G_IO_ERR
  wfds -> G_IO_OUT | G_IO_ERR
  xfds -> G_IO_PRI

I came up with this table by looking at Linux fs/select.c which maps
select(2) to poll(2) internally.

Another detail to watch out for are the global variables that reference
rfds/wfds/xfds during slirp_select_poll().  sofcantrcvmore() and
sofcantsendmore() use these globals to clear fd_set bits.  When
sofcantrcvmore() is called, the wfds bit is cleared so that the write
handler will no longer be run for this iteration of the event loop.

This actually seems buggy to me since TCP connections can be half-closed
and we'd still want to handle data in half-duplex fashion.  I think the
real intention is to avoid running the read/write handler when the
socket has been fully closed.  This is indicated with the SS_NOFDREF
state bit so we now check for it before invoking the TCP write handler.
Note that UDP/ICMP code paths don't care because they are
connectionless.

Note that slirp/ has a lot of tabs and sometimes mixed tabs with spaces.
I followed the style of the surrounding code.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Message-id: 1361356113-11049-6-git-send-email-stefanha@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 2 insertions, 4 deletions

diff --git a/slirp/libslirp.h b/slirp/libslirp.h
index 49609c2ad7..ceabff81b2 100644
--- a/slirp/libslirp.h
+++ b/slirp/libslirp.h
@@ -17,11 +17,9 @@ Slirp *slirp_init(int restricted, struct in_addr vnetwork,
 void slirp_cleanup(Slirp *slirp);
 
 void slirp_update_timeout(uint32_t *timeout);
-void slirp_select_fill(int *pnfds,
-                       fd_set *readfds, fd_set *writefds, fd_set *xfds);
+void slirp_pollfds_fill(GArray *pollfds);
 
-void slirp_select_poll(fd_set *readfds, fd_set *writefds, fd_set *xfds,
-                       int select_error);
+void slirp_pollfds_poll(GArray *pollfds, int select_error);
 
 void slirp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len);