[Qemu-devel] [PATCH v4] qemu-char: Fix missed data on unix socket

[pyssling]

From: Nils Carlson <address@hidden>

Commit 812c1057 introduced HUP detection on unix and tcp sockets prior
to a read in tcp_chr_read. This unfortunately broke CloudStack 4.2
which relied on the old behaviour where data on a socket was readable
even if a HUP was present.

A working solution is to properly check the return values from recv,
handling a closed socket once there is no more data to read.

Also enable polling for G_IO_NVAL to ensure the callback is called
for all possible events as these should now be possible to handle
with the improved error detection.

Signed-off-by: Nils Carlson <address@hidden>
---
 qemu-char.c |   15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/qemu-char.c b/qemu-char.c
index 617e034..3cbfe3e 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -807,7 +807,8 @@ static gboolean io_watch_poll_prepare(GSource *source, gint 
*timeout_)
     }
 
     if (now_active) {
-        iwp->src = g_io_create_watch(iwp->channel, G_IO_IN | G_IO_ERR | 
G_IO_HUP);
+        iwp->src = g_io_create_watch(iwp->channel,
+                                     G_IO_IN | G_IO_ERR | G_IO_HUP | 
G_IO_NVAL);
         g_source_set_callback(iwp->src, iwp->fd_read, iwp->opaque, NULL);
         g_source_attach(iwp->src, NULL);
     } else {
@@ -2847,12 +2848,6 @@ static gboolean tcp_chr_read(GIOChannel *chan, 
GIOCondition cond, void *opaque)
     uint8_t buf[READ_BUF_LEN];
     int len, size;
 
-    if (cond & G_IO_HUP) {
-        /* connection closed */
-        tcp_chr_disconnect(chr);
-        return TRUE;
-    }
-
     if (!s->connected || s->max_size <= 0) {
         return TRUE;
     }
@@ -2860,7 +2855,11 @@ static gboolean tcp_chr_read(GIOChannel *chan, 
GIOCondition cond, void *opaque)
     if (len > s->max_size)
         len = s->max_size;
     size = tcp_chr_recv(chr, (void *)buf, len);
-    if (size == 0) {
+    if (size == 0 ||
+        (size < 0 &&
+         !(errno == EAGAIN ||
+           errno == EWOULDBLOCK ||
+           errno == EINTR))) {
         /* connection closed */
         tcp_chr_disconnect(chr);
     } else if (size > 0) {
-- 
1.7.10.4