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

[Kenneth Salerno]

Hello,

While the patches fixed the pseudo ICMP between the guest (10.0.2.x) and the 
DHCP gateway (10.0.2.2), I have still never been able to get TCP/UDP working. I 
even tried compiling glib for MinGW32 without -mms-bitfields to force Qemu to 
build without taking this compiler flag from pkg-config, but I got the same 
results so I don't believe it's a packing issue this time. What is different 
about the way packets are constructed for ICMP versus actual TCP/UDP packets 
that leave the guest?

Here is a log I collected from the latest Git build as of 2012-02-01. The 
sequence was as follows: I ping 10.0.2.2 from 10.0.2.5, then I attempt a DNS 
lookup from nameserver 209.18.47.61:

arp_table_add...
 ip = 0x502000a
 hw addr = 52:54:00:12:34:56
arp_table_add...
 ip = 0x502000a
 hw addr = 52:54:00:12:34:56
m_get...
 m = 5bd4f0b8
ip_input...
 m = 5bd4f0b8
 m_len = 84
icmp_input...
 m = 5bd4f0b8
 m_len = 84
 icmp_type = 8
ip_output...
 so = 0
 m0 = 5bd4f0b8
if_output...
 so = 0
 ifm = 5bd4f0b8
if_start...
arp_table_search...
 ip = 0x502000a
 found hw addr = 52:54:00:12:34:56
m_free...
 m = 5bd4f0b8
m_get...
 m = 5bd4f0b8
ip_input...
 m = 5bd4f0b8
 m_len = 84
icmp_input...
 m = 5bd4f0b8
 m_len = 84
 icmp_type = 8
ip_output...
 so = 0
 m0 = 5bd4f0b8
if_output...
 so = 0
 ifm = 5bd4f0b8
if_start...
arp_table_search...
 ip = 0x502000a
 found hw addr = 52:54:00:12:34:56
m_free...
 m = 5bd4f0b8
arp_table_add...
 ip = 0x502000a
 hw addr = 52:54:00:12:34:56
m_get...
 m = 5bd4f0b8
ip_input...
 m = 5bd4f0b8
 m_len = 55
udp_input...
 m = 5bd4f0b8
 iphlen = 20
sosendto...
 so = 5bd104a0
 m = 5bd4f0b8
 sendto()ing, addr.sin_port=53, addr.sin_addr.s_addr=209.18.47.61
m_free...
 m = 0
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
m_get...
 m = 5bd4f728
ip_input...
 m = 5bd4f728
 m_len = 55
udp_input...
 m = 5bd4f728
 iphlen = 20
sosendto...
 so = 5bd104a0
 m = 5bd4f728
 sendto()ing, addr.sin_port=53, addr.sin_addr.s_addr=209.18.47.61
m_free...
 m = 5bd4f0b8
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
m_get...
 m = 5bd4f0b8
ip_input...
 m = 5bd4f0b8
 m_len = 55
udp_input...
 m = 5bd4f0b8
 iphlen = 20
sosendto...
 so = 5bd104a0
 m = 5bd4f0b8
 sendto()ing, addr.sin_port=53, addr.sin_addr.s_addr=209.18.47.61
m_free...
 m = 5bd4f728
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
ip_slowtimo...
tcp_slowtimo...
[repeated]


Another strange problem I've been having with newer builds from Git lately is I 
can only execute qemu-system-*.exe correctly from within gdb (i.e. 
"/usr/bin/gdb.exe ./i386-softmmu/qemu-system-i386.exe; gdb>run -L ./pc-bios"). 
If I run qemu-system-*.exe outside of gdb it will otherwise die complaining 
about exception code 0xc0000005 at address 0x000000007c91b21a in ntdll.dll... 
"--help" works though...


Any suggestions are appreciated. Thanks.

Ken

--- On Sat, 8/6/11, Blue Swirl <address@hidden> wrote:

> From: Blue Swirl <address@hidden>
> Subject: Re: [Qemu-devel] 0.15.0-rc2 (any version past 0.14.1) having issues 
> with SLIRP on Windows XP host
> To: "Anthony Liguori" <address@hidden>, "Jan Kiszka" <address@hidden>
> Cc: "TeLeMan" <address@hidden>, "Kenneth Salerno" <address@hidden>, 
> address@hidden
> Date: Saturday, August 6, 2011, 10:35 AM
> On Sat, Aug 6, 2011 at 1:33 PM,
> Anthony Liguori <address@hidden>
> wrote:
> > On 08/05/2011 10:25 PM, TeLeMan wrote:
> >>
> >> On Sat, Aug 6, 2011 at 04:46, Blue Swirl<address@hidden>
>  wrote:
> >>>
> >>> On Fri, Aug 5, 2011 at 8:09 PM, Kenneth
> Salerno
> >>> <address@hidden>
>  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)
> 
> I grepped the tree for ((packed)). The only two places where
> bit
> fields are used with packed structs are in SLIRP:
> 
> struct ip {
> #ifdef HOST_WORDS_BIGENDIAN
>     u_int ip_v:4,   
>         /* version */
>        
> ip_hl:4;        /* header
> length */
> #else
>     u_int ip_hl:4,   
>     /* header length */
>        
> ip_v:4;       
>     /* version */
> #endif
>     uint8_t   
>     ip_tos;   
>         /* type of service */
>     uint16_t   
> ip_len;       
>     /* total length */
>     uint16_t   
> ip_id;       
>     /* identification */
>     uint16_t   
> ip_off;       
>     /* fragment offset field */
> #define    IP_DF 0x4000   
>         /* don't fragment flag
> */
> #define    IP_MF 0x2000   
>         /* more fragments flag
> */
> #define    IP_OFFMASK
> 0x1fff        /* mask for
> fragmenting bits */
>     uint8_t ip_ttl;   
>         /* time to live */
>     uint8_t ip_p;   
>         /* protocol */
>     uint16_t   
> ip_sum;       
>     /* checksum */
>     struct    in_addr
> ip_src,ip_dst;    /* source and dest address
> */
> } __attribute__((packed));
> 
> struct    ip_timestamp {
>     uint8_t   
> ipt_code;        /* IPOPT_TS
> */
>     uint8_t   
> ipt_len;        /* size of
> structure (variable) */
>     uint8_t   
> ipt_ptr;        /* index of
> current entry */
> #ifdef HOST_WORDS_BIGENDIAN
>     u_int   
> ipt_oflw:4,        /* overflow
> counter */
>        
> ipt_flg:4;        /* flags,
> see below */
> #else
>     u_int   
> ipt_flg:4,        /* flags,
> see below */
>        
> ipt_oflw:4;        /* overflow
> counter */
> #endif
>     union ipt_timestamp {
>        
> n_long    ipt_time[1];
>        
> struct    ipt_ta {
>            
> struct in_addr ipt_addr;
>            
> n_long ipt_time;
>         } ipt_ta[1];
>     } ipt_timestamp;
> } __attribute__((packed));
> 
> I'd avoid the bit fields altogether in both cases, then also
> the
> #ifdeffery could be removed.
>