Re: [Qemu-devel] 0.15.0-rc2 (any version past 0.14.1) having issues with SLIRP on Windows XP host

[Anthony Liguori <anthony@codemonkey.ws>]

On 08/05/2011 10:25 PM, TeLeMan wrote:
> On Sat, Aug 6, 2011 at 04:46, Blue Swirl<blauwirbel@gmail.com>  wrote:
>> On Fri, Aug 5, 2011 at 8:09 PM, Kenneth Salerno
>> <kennethsalerno@yahoo.com>  wrote:
>>> Hi,
>>>
>>> I'm not sure if any defaults (build or runtime) have changed since 0.14.1, but I can no longer get the following to work anymore for QEMU versions 0.15.0-rc2 or recent development builds:
>>>
>>>   -device e1000,netdev=mynet0 -netdev type=user,id=mynet0 ...
>>>
>>> Works great in 0.14.1 however.
>>>
>>>  From the QEMU console, "info networking" shows the NIC e1000 and the VLAN correctly setup, the guest (RHEL 6.1 x86_64) has its NIC recognized and networking setup, just can't seem to communicate with the gateway (10.0.2.2). The only difference I see in the console is cosmetic (restricted=off rather than restricted=n).
>>>
>>> Host OS: Windows XP
>>> Build env: i686-pc-mingw32-gcc 4.5.2, binutils 2.21.53.20110731 i386pe
>>> Runtime env: Cygwin 1.7.9 2011-03-29, SDL 1.2.14, mingw32-glib 2.28.1-1,
>>>              mingw32-gettext 0.18.1-2
>>> Guest OS: RHEL 6.1
>>>
>>> Is it just me?
>>
>> No, this is fallout from glib use:
>> http://lists.nongnu.org/archive/html/qemu-devel/2011-08/msg00134.html
>>
>> The fix is to rewrite structures without using GCC bit fields.
>
> -mms-bitfields affects all byte-alignments in a structure. For example,
> struct s
> {
>     uint8_t a;
>     uint32_t b;
> } __attribute__((packed));
>
> sizeof(s) is 5 without -mms-bitfields but sizeof(s) is 8 with -mms-bitfields.

If you can identify the offending structs, you can do:

#pragma pack(push,1)

struct s
{
     uint8_t a;
     uint32_t b;
} __attribute__((packed));

#pragma pack(pop)

Regards,

Anthony Liguori