Bug 711275

---Problem Description---
In the Bridge configuration :

   <interface type='bridge'>
      <mac address='de:ad:be:ef:43:42'/>
      <source bridge='virbr0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
    </interface>

packets are dropped in the rx ring buffer when transferring large files from host-guest and vice-versa (No packets are dropped in tx ring buffer)

 
---uname output---
Linux localhost.localdomain 2.6.9-89.EL #1 Mon Apr 20 10:23:08 EDT 2009 i686 i686 i386 GNU/Linux
 
Machine Type = x3650 
 
---Steps to Reproduce---
 create 5GB files on guest and host : 
dd if=/dev/zero of=5GBGBfile.guest bs=1024k count=5000 on guest 
dd if=/dev/zero of=5GBGBfile.host bs=1024k count=5000 on host

start copying the files : 

5GBGBfile.guest file - from guest to host 
5GBGBfile.host file - from host to guest 

using scp utility 

run the following one-liner on the guest 
while true ; do date >> rxtx.log  ; ifconfig eth0 | egrep "RX bytes|RX packets|TX packets"  >> rxtx.log  ; sleep 1 ; done 

this will continuously monitor the RX/TX ring buffers and  write the information to rxtx.log file - during the analysis of the log file it is observed that approx 2000 packets are dropped by rx ring buffer.
 
Log file 
---------
file contains the ifconfig eth0 output when the file transfer is going on


General information :
--------------------------
Kernel version: Linux mx3650a.in.ibm.com 2.6.32-128.el6.x86_64 #1 SMP Mon Mar 28 21:55:33 EDT 2011 x86_64 x86_64 x86_64 GNU/Linux

Qemu version: 
root@mx3650a ping_test_data]# rpm -qa | grep kvm
qemu-kvm-0.12.1.2-2.153.el6.x86_64
qemu-kvm-tools-0.12.1.2-2.153.el6.x86_64
[root@mx3650a ping_test_data]# rpm -qa|grep qemu
qemu-kvm-0.12.1.2-2.153.el6.x86_64
gpxe-roms-qemu-0.9.7-6.7.el6.noarch
qemu-img-0.12.1.2-2.153.el6.x86_64
qemu-kvm-tools-0.12.1.2-2.153.el6.x86_64

Guest OS: 64 bit

Guest OS Image storage type: local file

Host Machine Type: x3650

Target Machine Type (for migration): -NA-

Test Type: manual 

Qemu Command Line: 
 /usr/libexec/qemu-kvm -S -M rhel6.1.0 -enable-kvm -m 1024 -smp 4,sockets=4,cores=1,threads=1 -name vm00-RHEL48-SMP -uuid e9e158b9-0b9b-79e4-53e6-8229b72a28ad -nodefconfig -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/vm00-RHEL48-SMP.monitor,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc -boot c -drive file=/home/storage/onnm/vm00-RHEL48-SMP.img,if=none,id=drive-ide0-0-0,format=raw,cache=none,aio=threads -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 -drive if=none,media=cdrom,id=drive-ide0-1-0,readonly=on,format=raw -device ide-drive,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0 -netdev tap,fd=32,id=hostnet0 -device rtl8139,netdev=hostnet0,id=net0,mac=de:ad:be:ef:48:46,bus=pci.0,addr=0x3 -chardev pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 -usb -vnc 0.0.0.0:54,password -vga cirrus -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x4

Using libvirt or not?
Using libvirt , but not relevant to this test

============ Networking details ====================

Device details :
Adapter : Qemu Emulated Realtek-8139 
device script :
 <interface type='bridge'>
      <mac address='de:ad:be:ef:48:46'/>
      <source bridge='virbr0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
    </interface>

Default network :
Network Script :
<network>
  <name>default</name>
  <uuid>32612766-4b8e-4cd1-8eb9-5f9350a1b094</uuid>
  <forward mode='nat'/>
  <bridge name='virbr0' stp='on' delay='0' />
  <mac address='52:54:00:30:7B:9A'/>
  <ip address='192.168.122.1' netmask='255.255.255.0'>
    <dhcp>
      <range start='192.168.122.2' end='192.168.122.254' />
    </dhcp>
  </ip>
</network>



============= Actual test ========================
** Note : 
As far as "Data Transmission Receving test" 
(http://fedoraproject.org/wiki/QA:Testcase_Virtualization_Data_Transmission_Receving)
is concerned - I have already PASSed it. 

But I am concerned about the packt loss because of this 
(http://en.wikipedia.org/wiki/Packet_loss), so here are the detailed steps :

(1) create a 2.5GB File on host:
    dd if=/dev/zero of=2.5GGFile.host bs=1024k count=2500
(2) take it chksum :
    cksum 2.5GBFile.host > cksum.host
(3) Repeate the steps (1) & (2) on guest : 
    dd if=/dev/zero of=2.5GGFile.guest bs=1024k count=2500
    cksum 2.5GBFile.guest > cksum.guest
(4) Copy the cksum.host file to guest 
    So, now the there are 3 files on guest:
    	[root@localhost files]# ls -l # on guest 
	total 2562512
	-rw-r--r--  1 root root 2621440000 Apr 13 12:42 2.5GBFile.guest
	-rw-r--r--  1 root root         38 Apr 14 05:16 cksum.guest
	-rw-r--r--  1 root root         37 Apr 14 05:19 cksum.host
	[root@localhost files]# cat cksum.*
	2930258761 2621440000 2.5GBFile.guest 
	2930258761 2621440000 2.5GBFile.host
(5) Copy the cksum.guest file to host 
    So, now the there are 3 files on host:
    	[root@mx3650a files]# ls -l
	total 2560012
	-rw-r--r--. 1 root root 2621440000 Apr 13 18:12 2.5GBFile.host
	-rw-r--r--. 1 root root         38 Apr 14 10:52 cksum.guest
	-rw-r--r--. 1 root root         37 Apr 14 10:42 cksum.host
	[root@mx3650a files]# cat cksum.*
	2930258761 2621440000 2.5GBFile.guest
	2930258761 2621440000 2.5GBFile.host
(6) reboot the guest 
(7) Check for the state of the network interface on _guest_:
    [root@localhost ~]# ifconfig eth0 
eth0      Link encap:Ethernet  HWaddr DE:AD:BE:EF:48:46  
          inet addr:192.168.122.164  Bcast:192.168.122.255  Mask:255.255.255.0
          inet6 addr: fe80::dcad:beff:feef:4846/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:68 errors:0 dropped:0 overruns:0 frame:0 <---no packets dropped !!
          TX packets:65 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:6982 (6.8 KiB)  TX bytes:8811 (8.6 KiB)
          Interrupt:10 
(8) Check for the state of the network interface on _host_:
[root@mx3650a files]# ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 00:1A:64:63:94:D4  
          inet addr:9.126.89.21  Bcast:9.126.89.255  Mask:255.255.255.0
          inet6 addr: fe80::21a:64ff:fe63:94d4/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:3229397 errors:0 dropped:0 overruns:0 frame:0 <---no packets dropped !!
          TX packets:1775444 errors:19283 dropped:0 overruns:0 carrier:19283
          collisions:203734 txqueuelen:1000 
          RX bytes:2978279305 (2.7 GiB)  TX bytes:868705632 (828.4 MiB)
          Interrupt:16 Memory:ce000000-ce012800
(9) Start transfering 2.5 GB Files from host-to-guest and guest-to-host simultaneously:
    From host give these two commands from different terminals :
    [root@mx3650a files]# scp root.122.164:/root/files/2.5GBFile.guest . 
    [root@mx3650a files]# scp 2.5GBFile.host  root.122.164:/root/files/

    and wait for the transfer to complete !!

After transfer is complete on both sides .....

(10) Check for the state of the network interface on _host_:
[root@mx3650a files]# ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 00:1A:64:63:94:D4  
          inet addr:9.126.89.21  Bcast:9.126.89.255  Mask:255.255.255.0
          inet6 addr: fe80::21a:64ff:fe63:94d4/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:3243345 errors:0 dropped:0 overruns:0 frame:0 <---no packets dropped !!
          TX packets:1790267 errors:19954 dropped:0 overruns:0 carrier:19954
          collisions:204442 txqueuelen:1000 
          RX bytes:2979433111 (2.7 GiB)  TX bytes:883134757 (842.2 MiB)
          Interrupt:16 Memory:ce000000-ce012800 

(11) Check for the state of the network interface on _guest_:
[root@localhost files]# ifconfig eth0 
eth0      Link encap:Ethernet  HWaddr DE:AD:BE:EF:48:46  
          inet addr:192.168.122.164  Bcast:192.168.122.255  Mask:255.255.255.0
          inet6 addr: fe80::dcad:beff:feef:4846/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:2739049 errors:0 dropped:1675 overruns:0 frame:0 <--- PACKETS DROPPED !!
          TX packets:2010431 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:2772622210 (2.5 GiB)  TX bytes:2760062357 (2.5 GiB)
          Interrupt:10 

(12) Cksum for guest file :
[root@localhost files]# cksum 2.5GBFile.guest > cksum.guest.latest
[root@localhost files]# diff cksum.guest cksum.guest.latest

seems to be OK !

(13) cksum for host file :
 [root@localhost files]# cksum 2.5GBFile.host > cksum.host.latest
[root@localhost files]# diff cksum.host.latest cksum.host

seems to be OK !

But then , is packet loss here insignificant ??

** Note ** 

With virtio adapter - file transfer is clean with 0 packet loss, 
both with vhost=on|off