[Qemu-devel] Commit 812c1057f, Handle G_IO_HUP in tcp_chr_read for tcp chardev, broke CloudStack

[Nils Carlson]

Hi,

The commit 812c1057f, Handle G_IO_HUP in tcp_chr_read for tcp chardev, 
broke CloudStack. CloudStack was relying on fire-and-forget style 
messaging across a unix socket to the VM. Because the host "fires" the 
message and then closes the socket a HUP is present on the line when the 
VM starts reading the socket. Commit 812c1057f ensured that the socket was 
checked for a HUP prior to calling recv, causing recv never to be called 
by the VM and no data to be read.

I've posted a patch, attached here, which moves the HUP detection to after 
all data has been read, but only for Linux as I suspect windows requires 
HUPs to be detected prior to reading data.

Could you comment on the validity of this assumption? I would be really 
happy to have this issue solved as it stops us from upgrading to later 
versions of qemu.

Amit also has concerns regarding the return values from the tcp_chr_read 
function, which seem a bit odd as they are all TRUE, even for failure 
paths.

All feedback very much appreciated.

Best Regards,
Nils Carlson

qemu-char:_Fix_missed_data_on_unix_socket.patch
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