[Qemu-devel] [PULL 03/13] qemu-char: Fix missed data on unix socket

[Paolo Bonzini <pbonzini@redhat.com>]

From: Nils Carlson <pyssling@ludd.ltu.se>

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 <pyssling@ludd.ltu.se>
Message-Id: <1437338396-22336-1-git-send-email-pyssling@ludd.ltu.se>
[Do not handle EINTR; use socket_error(). - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 qemu-char.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/qemu-char.c b/qemu-char.c
index 3200200..d956f8d 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 {
@@ -2856,12 +2857,6 @@ 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;
     }
@@ -2869,7 +2864,9 @@ 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 &&
+         socket_error() != EAGAIN && socket_error() != EWOULDBLOCK)) {
         /* connection closed */
         tcp_chr_disconnect(chr);
     } else if (size > 0) {
-- 
2.4.3