No subject
Thu May 31 05:53:22 UTC 2012
=A0 =A0 Are you doing any port mirroring here to capture packets on PC2?. H=
ow are you sending packets from PC1 (running linux bridge?)?
=0A=0A
I am attaching wireshark capture for Dlink and Netgear STP packets.
=A0=A0 Can you send out complete packet capture from start of your test to =
the end to analyze
=A0=A0=20
=0A=A0=A0=A0 Thanks
=A0=A0=A0 Sasi
=0APlease let me know if any one has any idea or comment on=0A this.
Thanks,
Sujata
=A0=0A
--- On Thu, 6/14/12, Sasikanth babu <sasikanth.v19 at gmail.com> wrote:
=0A
From: Sasikanth babu <sasikanth.v19 at gmail.com>
Subject: Re: [Bridge] Query on Sapnning tree implementation from standard p=
oint of view
=0ATo: "Sujata Verma" <sujataverma3 at yahoo.com>
Cc: bridge at lists.linux-foundation.org
=0ADate: Thursday, June 14, 2012, 6:09 PM
On Thu, Jun 14, 2012 at 5:53 PM, Sujata Verma <sujataverma3 at yahoo.com> wrot=
e:
=0A=0AHi ,
I am going through spanning tree protocol and was testing it on Linux. My o=
bservation is there is no validation of timers for configuration BPDU.=A0 L=
ets say Root bridge received another BPDU from new bridge with invalid time=
r values but less priority, the existing bridge is becoming non-root bridge=
and is advertising the invalid timer values.=20
=0A=0A
As i have gone through 802.1D-1998 standard, i understand that 2004 is curr=
ent one but i was looking into STP not RSTP, i preferred to read this stand=
ard. I find these lines:
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
=0A=0A9.3.3 Validation of received BPDUs
A Bridge Protocol Entity shall process a received BPDU as specified in 8.7 =
if and only if the BPDU contains at least four octets and the Protocol Iden=
tifier has the value specified for BPDUs (9.3.2), and
=0A=0Aa) The BPDU Type=0A denotes a Configuration BPDU and the BPDU contain=
s at least 35 octets, and the
value of the BPDUs Message Age parameter is less than that of its Max Age p=
arameter; or
b) The BPDU Type denotes a Topology Change Notification BPDU.
=0A=0AIn case a), any octets that are present beyond Octet 35 are ignored, =
as far as processing according to this
standard is concerned. Similarly, in case b), any octets beyond Octet 4 are=
ignored.
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
=0A=0A
Does this implies that any value timer values present within octet 35 is va=
lid value and there is no validation done. Even if range for hello timer, m=
ax age and forward delay is defined and is limited. Is it an issue or fine =
within the standard?
=0A=0A
=A0 Not all STP implementation do BPDU validations i.e validates all BPDU p=
arameters present within 35 octet. The validation checks for invalid values=
present in the bpdu,=20
=0A=0A=A0 if the BPDU validation fails it drops the BPDU. The have seen thi=
s validations in proprietary software.
=A0=20
=0A=0APlease help me understand this issue and thanks for any comments.
Regards,
Sujata
=0A=0A
_______________________________________________
=0ABridge mailing list
=0ABridge at lists.linux-foundation.org
=0Ahttps://lists.linuxfoundation.org/mailman/listinfo/bridge
=0A
_______________________________________________
=0ABridge mailing list
=0ABridge at lists.linux-foundation.org
=0Ahttps://lists.linuxfoundation.org/mailman/listinfo/bridge
=0A
--1521818054-454116840-1340012128=:42375
Content-Type: text/html; charset=iso-8859-1
Content-Transfer-Encoding: quoted-printable
<table cellspacing=3D"0" cellpadding=3D"0" border=3D"0" ><tr><td valign=3D"=
top" style=3D"font: inherit;">Ok. <br><br> I don't think STP std has =
mentioned this propagation, As far as I know=0A this prorogation is wrong. =
I think this must be a bug in Netgear =0Aswitch.<br><br>>>> My set=
up is <br><br> PC1( Windows PC) ----Switch------PC2=
( Windows PC)<br><br>Using Colasoft builder tool, i captured one STP packe=
t modified the bridge priority such that it becomes root bridge , put all i=
nvalid values for timers as 255 and sent to the switch. My switch is linux =
PC, netgear switch and dlink switch for comparison purposes. <br><br>As swi=
tch receives the better BID packet it stop advertising it self as bridge an=
d take values of timers from root bridge which is 255 for bridge, hello and=
forward delay in my case.<br><br>So the switch receives this packet and up=
dates its cost, root information and sends out on another port on which PC2=
is connected and where i am seeing it on wireshark with all timer values a=
s received from root bridge. This is all fine, the only problem is, its not=
validating the timer values which seems a bug to me , as the timer values =
are defined within the limit in
standard.<br><br>If Netgear is doing validation of the hello timer and is =
putting the maximum allowed value seems fine to me and not a bug. But still=
, i think forward delay and max age should also be validated before accepti=
ng new BPDU as root bridge.<br><br>As in linux/dlink it is not doing any va=
lidation and sending bpdu with 255 values, which is not correct as it=
could lead to delay of convergence time in case of root failure.<br><br>In=
netgear switch the command display before and after are as follows:<br><br=
>=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D<br>(FSM726V3) #show spa=
nning-tree<br><br>Bridge Priority................................ 32768<br>=
Bridge Identifier.............................. 80:00:00:26:F2:AF:93:A5<br>=
Time Since Topology Change..................... 0 day 0 hr 42 min 14 sec<br=
>Topology Change Count.......................... 1<br>Topology Change in pr=
ogress.................... FALSE<br>Designated
Root................................ 80:00:00:26:F2:AF:93:A5<br>Root Path =
Cost................................. 0<br>Root Port Identifier............=
............... 00:00<br>Bridge Max Age................................. 20=
<br>Bridge Max Hops................................ 20<br>Bridge Tx Hold Co=
unt........................... 6<br>Bridge Forwarding Delay................=
........ 15<br>Hello Time..................................... 2<br>Bridge =
Hold Time............................... 6<br>CST Regional Root............=
.................. 80:00:00:26:F2:AF:93:A5<br>Regional Root Path Cost......=
.................. 0<br>--More-- or (q)uit<br><br><br><br>  =
; Associated FIDs &nbs=
p; Associated VLANs<br> --------------- =
----------------<br>=
1 &=
nbsp; 1<b=
r> 100 &nb=
sp; =
100<br> 200 &nb=
sp; =
200<br><br>(FSM726V3) #show span=
ning-tree summary<br><br>Spanning Tree Adminmode........... Enabled<br>Span=
ning Tree Version............. IEEE 802.1d<br>BPDU Guard Mode..............=
..... Disabled<br>BPDU Filter Mode.................. Disabled<br>Configurat=
ion Name................ 00-26-F2-AF-93-A5<br>Configuration Revision Level.=
..... 0<br>Configuration Digest Key.......... 0xac36177f50283cd4b83821d8ab2=
6de62<br>Configuration Format Selector..... 0<br>No MST instances to
display.<br><br>=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D<br>After sendi=
ng the invalid timer packet:<br><br>(FSM726V3) #<br>(FSM726V3) #<br>(FSM726=
V3) #show spanning-tree summary<br><br>Spanning Tree Adminmode........... E=
nabled<br>Spanning Tree Version............. IEEE 802.1d<br>BPDU Guard Mode=
................... Disabled<br>BPDU Filter Mode.................. Disabled=
<br>Configuration Name................ 00-26-F2-AF-93-A5<br>Configuration R=
evision Level...... 0<br>Configuration Digest Key.......... 0xac36177f50283=
cd4b83821d8ab26de62<br>Configuration Format Selector..... 0<br>No MST insta=
nces to display.<br><br>(FSM726V3) #show spanning-tree<br><br>Bridge Priori=
ty................................ 32768<br>Bridge Identifier..............=
................ 80:00:00:26:F2:AF:93:A5<br>Time Since Topology Change.....=
................ 0 day 0 hr 0 min 12 sec<br>Topology Change Count..........=
................ 2<br>Topology Change in progress....................
TRUE<br>Designated Root................................ 10:00:00:20:A1:F0:=
88:50<br>Root Path Cost................................. 200004<br>Root Por=
t Identifier........................... 80:01<br>Bridge Max Age............=
..................... 255<br>Bridge Max Hops...............................=
. 20<br>Bridge Tx Hold Count........................... 6<br>Bridge Forward=
ing Delay........................ 255<br><span style=3D"color: rgb(255, 0, =
0);">Hello Time..................................... 10</span><br>Bridge Ho=
ld Time............................... 6<br>CST Regional Root..............=
................ 80:00:00:26:F2:AF:93:A5<br>Regional Root Path Cost........=
................ 0<br>--More-- or (q)uit<br><br><br><br> &=
nbsp; Associated FIDs =
Associated VLANs<br> --------------- &n=
bsp;
----------------<br> 1 &nbs=
p; &=
nbsp; 1<br> &nbs=
p; 100 &nb=
sp; 100<b=
r> 200 &nb=
sp; =
200<br><br>(FSM726V3) #<br><br><br>=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D<br>As Cisco doesnt accept this type of BPDU it =
means that it is a bug to be fixed on Linux, as i conclude. <br><br>Please =
let me know if you think otherwise.<br><br>Regards,<br>Sujata<br><br><br><b=
r><br>--- On <b>Fri, 6/15/12, Sasikanth babu <i><sasikanth.v19 at gmail.com=
></i></b> wrote:<br><blockquote style=3D"border-left: 2px solid rgb(16,
16, 255); margin-left: 5px; padding-left: 5px;"><br>From: Sasikanth babu &=
lt;sasikanth.v19 at gmail.com><br>Subject: Re: [Bridge] Query on Sapnning t=
ree implementation from standard point of view<br>To: "Sujata Verma" <su=
jataverma3 at yahoo.com><br>Cc: bridge at lists.linux-foundation.org<br>Date: =
Friday, June 15, 2012, 7:25 PM<br><br><div id=3D"yiv115092420"><div dir=3D"=
ltr"><br><div class=3D"yiv115092420gmail_quote">On Fri, Jun 15, 2012 at 5:5=
5 PM, Sujata Verma <span dir=3D"ltr"><<a rel=3D"nofollow" ymailto=3D"mai=
lto:sujataverma3 at yahoo.com" target=3D"_blank" href=3D"/mc/compose?to=3Dsuja=
taverma3 at yahoo.com">sujataverma3 at yahoo.com</a>></span> wrote:<br><blockq=
uote class=3D"yiv115092420gmail_quote" style=3D"margin:0 0 0 .8ex;border-le=
ft:1px #ccc solid;padding-left:1ex;">=0A<table border=3D"0" cellpadding=3D"=
0" cellspacing=3D"0"><tbody><tr><td style=3D"font:inherit;" valign=3D"top">=
Thanks. I was doing the same experiment on few switches, i could get hold o=
f and this is the result:<br><br>Cisco Switch catalyst 2950 : Completely ig=
noring the packet, so validations are proper.<br>=0A<br>Netgear FSM726V3 : =
Hello timer is validated and is propagated as 10 instead of 255 ( which i s=
ent) other max age and forward delay still it accepts as 255. <br><br></td>=
</tr></tbody></table></blockquote><div> I don't think STP std h=
as mentioned this propagation, As far as I know this prorogation is wrong. =
I think this must be a bug in Netgear switch.<br>=0A<br></div><blockquote c=
lass=3D"yiv115092420gmail_quote" style=3D"margin:0pt 0pt 0pt 0.8ex;border-l=
eft:1px solid rgb(204,204,204);padding-left:1ex;"><table border=3D"0" cellp=
adding=3D"0" cellspacing=3D"0"><tbody><tr><td style=3D"font:inherit;" valig=
n=3D"top">=0ADLINK-DES-3026 : No validation done and accepts all as 255 ( m=
ax age, forward delay and hello timer)<br><br>In both Netgear and Dlink the=
message age is changed to 16, which i am not sure why it has happened ? <b=
r><br>my setup is simple<br>=0A<br> PC1------Switch------PC2<br><br>F=
rom PC1 i am sending invalid timer values and observing on PC2.<br></td></t=
r></tbody></table></blockquote><div><br> Are you doing any por=
t mirroring here to capture packets on PC2?. How are you sending packets fr=
om PC1 (running linux bridge?)?<br>=0A</div><blockquote class=3D"yiv1150924=
20gmail_quote" style=3D"margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(=
204,204,204);padding-left:1ex;"><table border=3D"0" cellpadding=3D"0" cells=
pacing=3D"0"><tbody><tr><td style=3D"font:inherit;" valign=3D"top">=0A<br>I=
am attaching wireshark capture for Dlink and Netgear STP packets.<br><br><=
/td></tr></tbody></table></blockquote><div> Can you send out co=
mplete packet capture from start of your test to the end to analyze<br>&nbs=
p; <br>=0A Thanks<br> Sasi<br><br=
></div><blockquote class=3D"yiv115092420gmail_quote" style=3D"margin:0pt 0p=
t 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex;"><tabl=
e border=3D"0" cellpadding=3D"0" cellspacing=3D"0"><tbody><tr><td style=3D"=
font:inherit;" valign=3D"top">=0APlease let me know if any one has any idea=
or comment on=0A this.<br><br>Thanks,<br>Sujata<br></td></tr></tbody></tab=
le></blockquote><div> </div><blockquote class=3D"yiv115092420gmail_quo=
te" style=3D"margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204=
);padding-left:1ex;"><table border=3D"0" cellpadding=3D"0" cellspacing=3D"0=
">=0A<tbody><tr><td style=3D"font:inherit;" valign=3D"top"><br><br><br><br>=
<br>--- On <b>Thu, 6/14/12, Sasikanth babu <i><<a rel=3D"nofollow" ymail=
to=3D"mailto:sasikanth.v19 at gmail.com" target=3D"_blank" href=3D"/mc/compose=
?to=3Dsasikanth.v19 at gmail.com">sasikanth.v19 at gmail.com</a>></i></b> wrot=
e:<br>=0A<blockquote style=3D"border-left:2px solid rgb(16,16,255);margin-l=
eft:5px;padding-left:5px;"><br>From: Sasikanth babu <<a rel=3D"nofollow"=
ymailto=3D"mailto:sasikanth.v19 at gmail.com" target=3D"_blank" href=3D"/mc/c=
ompose?to=3Dsasikanth.v19 at gmail.com">sasikanth.v19 at gmail.com</a>><br>Sub=
ject: Re: [Bridge] Query on Sapnning tree implementation from standard poin=
t of view<br>=0ATo: "Sujata Verma" <<a rel=3D"nofollow" ymailto=3D"mailt=
o:sujataverma3 at yahoo.com" target=3D"_blank" href=3D"/mc/compose?to=3Dsujata=
verma3 at yahoo.com">sujataverma3 at yahoo.com</a>><br>Cc: <a rel=3D"nofollow"=
ymailto=3D"mailto:bridge at lists.linux-foundation.org" target=3D"_blank" hre=
f=3D"/mc/compose?to=3Dbridge at lists.linux-foundation.org">bridge at lists.linux=
-foundation.org</a><br>=0ADate: Thursday, June 14, 2012, 6:09 PM<div><div c=
lass=3D"yiv115092420h5"><br><br><div><div dir=3D"ltr"><br><div>On Thu, Jun =
14, 2012 at 5:53 PM, Sujata Verma <span dir=3D"ltr"><<a rel=3D"nofollow"=
target=3D"_blank" href=3D"http://mc/compose?to=3Dsujataverma3@yahoo.com">s=
ujataverma3 at yahoo.com</a>></span> wrote:<br>=0A<blockquote style=3D"marg=
in:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">=0A<table borde=
r=3D"0" cellpadding=3D"0" cellspacing=3D"0"><tbody><tr><td style=3D"font:in=
herit;" valign=3D"top">Hi ,<br><br>I am going through spanning tree protoco=
l and was testing it on Linux. My observation is there is no validation of =
timers for configuration BPDU. Lets say Root bridge received another =
BPDU from new bridge with invalid timer values but less priority, the exist=
ing bridge is becoming non-root bridge and is advertising the invalid timer=
values. <br>=0A=0A<br>As i have gone through 802.1D-1998 standard, i under=
stand that 2004 is current one but i was looking into STP not RSTP, i prefe=
rred to read this standard. I find these lines:<br><br>=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D<br>=0A=0A9.3.3 Validation =
of received BPDUs<br><br>A Bridge Protocol Entity shall process a received =
BPDU as specified in 8.7 if and only if the BPDU contains at least four oct=
ets and the Protocol Identifier has the value specified for BPDUs (9.3.2), =
and<br>=0A=0Aa) The BPDU Type=0A denotes a Configuration BPDU and the BPDU =
contains at least 35 octets, and the<br>value of the BPDUs Message Age para=
meter is less than that of its Max Age parameter; or<br><br>b) The BPDU Typ=
e denotes a Topology Change Notification BPDU.<br>=0A=0AIn case a), any oct=
ets that are present beyond Octet 35 are ignored, as far as processing acco=
rding to this<br>standard is concerned. Similarly, in case b), any octets b=
eyond Octet 4 are ignored.<br><br>=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D<br>=0A=0A<br>Does this implies that any value timer valu=
es present within octet 35 is valid value and there is no validation done. =
Even if range for hello timer, max age and forward delay is defined and is =
limited. Is it an issue or fine within the standard?<br>=0A=0A<br></td></tr=
></tbody></table></blockquote><div> Not all STP implementation do BPD=
U validations i.e validates all BPDU parameters present within 35 octet. Th=
e validation checks for invalid values present in the bpdu, <br>=0A=0A =
; if the BPDU validation fails it drops the BPDU. The have seen this valida=
tions in proprietary software.<br> <br></div><blockquote style=3D"mar=
gin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1=
ex;">=0A=0A<table border=3D"0" cellpadding=3D"0" cellspacing=3D"0"><tbody><=
tr><td style=3D"font:inherit;" valign=3D"top">Please help me understand thi=
s issue and thanks for any comments.<br><br>Regards,<br>Sujata<br><br></td>=
</tr></tbody></table>=0A=0A<br>____________________________________________=
___<br>=0ABridge mailing list<br>=0A<a rel=3D"nofollow" target=3D"_blank" h=
ref=3D"http://mc/compose?to=3DBridge@lists.linux-foundation.org">Bridge at lis=
ts.linux-foundation.org</a><br>=0A<a rel=3D"nofollow" target=3D"_blank" hre=
f=3D"https://lists.linuxfoundation.org/mailman/listinfo/bridge">https://lis=
ts.linuxfoundation.org/mailman/listinfo/bridge</a><br></blockquote></div><b=
r></div>=0A</div></div></div></blockquote></td></tr></tbody></table><br>___=
____________________________________________<br>=0ABridge mailing list<br>=
=0A<a rel=3D"nofollow" ymailto=3D"mailto:Bridge at lists.linux-foundation.org"=
target=3D"_blank" href=3D"/mc/compose?to=3DBridge at lists.linux-foundation.o=
rg">Bridge at lists.linux-foundation.org</a><br>=0A<a rel=3D"nofollow" target=
=3D"_blank" href=3D"https://lists.linuxfoundation.org/mailman/listinfo/brid=
ge">https://lists.linuxfoundation.org/mailman/listinfo/bridge</a><br></bloc=
kquote></div><br></div>=0A</div></blockquote></td></tr></table>
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