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Date: Wed, 09 Oct 2013 11:01:31 -0400 From: Vlad Yasevich <vyasevic@...hat.com> To: Toshiaki Makita <makita.toshiaki@....ntt.co.jp> CC: Toshiaki Makita <toshiaki.makita1@...il.com>, David Miller <davem@...emloft.net>, netdev@...r.kernel.org, Fernando Luis Vazquez Cao <fernando_b1@....ntt.co.jp>, Patrick McHardy <kaber@...sh.net> Subject: Re: [PATCH net 0/4] bridge: Fix problems around the PVID On 10/01/2013 07:56 AM, Toshiaki Makita wrote: > On Mon, 2013-09-30 at 12:01 -0400, Vlad Yasevich wrote: >> On 09/30/2013 07:46 AM, Toshiaki Makita wrote: >>> On Fri, 2013-09-27 at 14:10 -0400, Vlad Yasevich wrote: >>>> On 09/27/2013 01:11 PM, Toshiaki Makita wrote: >>>>> On Thu, 2013-09-26 at 10:22 -0400, Vlad Yasevich wrote: >>>>>> On 09/26/2013 06:38 AM, Toshiaki Makita wrote: >>>>>>> On Tue, 2013-09-24 at 13:55 -0400, Vlad Yasevich wrote: >>>>>>>> On 09/24/2013 01:30 PM, Toshiaki Makita wrote: >>>>>>>>> On Tue, 2013-09-24 at 09:35 -0400, Vlad Yasevich wrote: >>>>>>>>>> On 09/24/2013 07:45 AM, Toshiaki Makita wrote: >>>>>>>>>>> On Mon, 2013-09-23 at 10:41 -0400, Vlad Yasevich >>>>>>>>>>> wrote: >>>>>>>>>>>> On 09/17/2013 04:12 AM, Toshiaki Makita wrote: >>>>>>>>>>>>> On Mon, 2013-09-16 at 13:49 -0400, Vlad Yasevich >>>>>>>>>>>>> wrote: >>>>>>>>>>>>>> On 09/13/2013 08:06 AM, Toshiaki Makita wrote: >>>>>>>>>>>>>>> On Thu, 2013-09-12 at 16:00 -0400, David >>>>>>>>>>>>>>> Miller wrote: >>>>>>>>>>>>>>>> From: Toshiaki Makita >>>>>>>>>>>>>>>> <makita.toshiaki@....ntt.co.jp> Date: Tue, >>>>>>>>>>>>>>>> 10 Sep 2013 19:27:54 +0900 >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> There seem to be some undesirable >>>>>>>>>>>>>>>>> behaviors related with PVID. 1. It has no >>>>>>>>>>>>>>>>> effect assigning PVID to a port. PVID >>>>>>>>>>>>>>>>> cannot be applied to any frame regardless >>>>>>>>>>>>>>>>> of whether we set it or not. 2. FDB >>>>>>>>>>>>>>>>> entries learned via frames applied PVID >>>>>>>>>>>>>>>>> are registered with VID 0 rather than VID >>>>>>>>>>>>>>>>> value of PVID. 3. We can set 0 or 4095 as >>>>>>>>>>>>>>>>> a PVID that are not allowed in IEEE >>>>>>>>>>>>>>>>> 802.1Q. This leads interoperational >>>>>>>>>>>>>>>>> problems such as sending frames with VID >>>>>>>>>>>>>>>>> 4095, which is not allowed in IEEE >>>>>>>>>>>>>>>>> 802.1Q, and treating frames with VID 0 as >>>>>>>>>>>>>>>>> they belong to VLAN 0, which is expected >>>>>>>>>>>>>>>>> to be handled as they have no VID >>>>>>>>>>>>>>>>> according to IEEE 802.1Q. >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> Note: 2nd and 3rd problems are potential >>>>>>>>>>>>>>>>> and not exposed unless 1st problem is >>>>>>>>>>>>>>>>> fixed, because we cannot activate PVID >>>>>>>>>>>>>>>>> due to it. >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> Please work out the issues in patch #2 with >>>>>>>>>>>>>>>> Vlad and resubmit this series. >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> Thank you. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> I'm hovering between whether we should fix >>>>>>>>>>>>>>> the issue by changing vlan 0 interface >>>>>>>>>>>>>>> behavior in 8021q module or enabling a bridge >>>>>>>>>>>>>>> port to sending priority-tagged frames, or >>>>>>>>>>>>>>> another better way. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> If you could comment it, I'd appreciate it >>>>>>>>>>>>>>> :) >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> BTW, I think what is discussed in patch #2 is >>>>>>>>>>>>>>> another problem about handling priority-tags, >>>>>>>>>>>>>>> and it exists without this patch set >>>>>>>>>>>>>>> applied. It looks like that we should prepare >>>>>>>>>>>>>>> another patch set than this to fix that >>>>>>>>>>>>>>> problem. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Should I include patches that fix the >>>>>>>>>>>>>>> priority-tags problem in this patch set and >>>>>>>>>>>>>>> resubmit them all together? >>>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> I am thinking that we might need to do it in >>>>>>>>>>>>>> bridge and it looks like the simplest way to do >>>>>>>>>>>>>> it is to have default priority regeneration >>>>>>>>>>>>>> table (table 6-5 from 802.1Q doc). >>>>>>>>>>>>>> >>>>>>>>>>>>>> That way I think we would conform to the spec. >>>>>>>>>>>>>> >>>>>>>>>>>>>> -vlad >>>>>>>>>>>>> >>>>>>>>>>>>> Unfortunately I don't think the default priority >>>>>>>>>>>>> regeneration table resolves the problem because >>>>>>>>>>>>> IEEE 802.1Q says that a VLAN-aware bridge can >>>>>>>>>>>>> transmit untagged or VLAN-tagged frames only (the >>>>>>>>>>>>> end of section 7.5 and 8.1.7). >>>>>>>>>>>>> >>>>>>>>>>>>> No mechanism to send priority-tagged frames is >>>>>>>>>>>>> found as far as I can see the standard. I think >>>>>>>>>>>>> the regenerated priority is used for outgoing >>>>>>>>>>>>> PCP field only if egress policy is not untagged >>>>>>>>>>>>> (i.e. transmitting as VLAN-tagged), and unused if >>>>>>>>>>>>> untagged (Section 6.9.2 3rd/4th Paragraph). >>>>>>>>>>>>> >>>>>>>>>>>>> If we want to transmit priority-tagged frames >>>>>>>>>>>>> from a bridge port, I think we need to implement >>>>>>>>>>>>> a new (optional) feature that is above the >>>>>>>>>>>>> standard, as I stated previously. >>>>>>>>>>>>> >>>>>>>>>>>>> How do you feel about adding a per-port policy >>>>>>>>>>>>> that enables a bridge to send priority-tagged >>>>>>>>>>>>> frames instead of untagged frames when egress >>>>>>>>>>>>> policy for the port is untagged? With this >>>>>>>>>>>>> change, we can transmit frames for a given vlan >>>>>>>>>>>>> as either all untagged, all priority-tagged or >>>>>>>>>>>>> all VLAN-tagged. >>>>>>>>>>>> >>>>>>>>>>>> That would work. What I am thinking is that we do >>>>>>>>>>>> it by special casing the vid 0 egress policy >>>>>>>>>>>> specification. Let it be untagged by default and >>>>>>>>>>>> if it is tagged, then we preserve the priority >>>>>>>>>>>> field and forward it on. >>>>>>>>>>>> >>>>>>>>>>>> This keeps the API stable and doesn't require >>>>>>>>>>>> user/admin from knowing exactly what happens. >>>>>>>>>>>> Default operation conforms to the spec and allows >>>>>>>>>>>> simple change to make it backward-compatible. >>>>>>>>>>>> >>>>>>>>>>>> What do you think. I've done a simple prototype of >>>>>>>>>>>> this an it seems to work with the VMs I am testing >>>>>>>>>>>> with. >>>>>>>>>>> >>>>>>>>>>> Are you saying that - by default, set the 0th bit of >>>>>>>>>>> untagged_bitmap; and - if we unset the 0th bit and >>>>>>>>>>> set the "vid"th bit, we transmit frames classified as >>>>>>>>>>> belonging to VLAN "vid" as priority-tagged? >>>>>>>>>>> >>>>>>>>>>> If so, though it's attractive to keep current API, >>>>>>>>>>> I'm worried about if it could be a bit confusing and >>>>>>>>>>> not intuitive for kernel/iproute2 developers that VID >>>>>>>>>>> 0 has a special meaning only in the egress policy. >>>>>>>>>>> Wouldn't it be better to adding a new member to >>>>>>>>>>> struct net_port_vlans instead of using VID 0 of >>>>>>>>>>> untagged_bitmap? >>>>>>>>>>> >>>>>>>>>>> Or are you saying that we use a new flag in struct >>>>>>>>>>> net_port_vlans but use the BRIDGE_VLAN_INFO_UNTAGGED >>>>>>>>>>> bit with VID 0 in netlink to set the flag? >>>>>>>>>>> >>>>>>>>>>> Even in that case, I'm afraid that it might be >>>>>>>>>>> confusing for developers for the same reason. We are >>>>>>>>>>> going to prohibit to specify VID with 0 (and 4095) in >>>>>>>>>>> adding/deleting a FDB entry or a vlan filtering >>>>>>>>>>> entry, but it would allow us to use VID 0 only when a >>>>>>>>>>> vlan filtering entry is configured. I am thinking a >>>>>>>>>>> new nlattr is a straightforward approach to >>>>>>>>>>> configure it. >>>>>>>>>> >>>>>>>>>> By making this an explicit attribute it makes vid 0 a >>>>>>>>>> special case for any automatic tool that would >>>>>>>>>> provision such filtering. Seeing vid 0 would mean that >>>>>>>>>> these tools would have to know that this would have to >>>>>>>>>> be translated to a different attribute instead of >>>>>>>>>> setting the policy values. >>>>>>>>> >>>>>>>>> Yes, I agree with you that we can do it by the way you >>>>>>>>> explained. What I don't understand is the advantage of >>>>>>>>> using vid 0 over another way such as adding a new >>>>>>>>> nlattr. I think we can indicate transmitting >>>>>>>>> priority-tags explicitly by such a nlattr. Using vid 0 >>>>>>>>> seems to be easier to implement than a new nlattr, but, >>>>>>>>> for me, it looks less intuitive and more difficult to >>>>>>>>> maintain because we have to care about vid 0 instead of >>>>>>>>> simply ignoring it. >>>>>>>>> >>>>>>>> >>>>>>>> The point I am trying to make is that regardless of the >>>>>>>> approach someone has to know what to do when enabling >>>>>>>> priority tagged frames. You proposal would require the >>>>>>>> administrator or config tool to have that knowledge. >>>>>>>> Example is: Admin does: bridge vlan set priority on dev >>>>>>>> eth0 Automated app: if (vid == 0) /* Turn on priority >>>>>>>> tagged frame support */ >>>>>>>> >>>>>>>> My proposal would require the bridge filtering >>>>>>>> implementation to have it. user tool: bridge vlan add vid 0 >>>>>>>> tagged Automated app: No special case. >>>>>>>> >>>>>>>> IMO its better to have 1 piece code handling the special >>>>>>>> case then putting it multiple places. >>>>>>> >>>>>>> Thank you for the detailed explanation. Now I understand your >>>>>>> intention. >>>>>>> >>>>>>> I have one question about your proposal. I guess the way to >>>>>>> enable priority-tagged is something like bridge vlan add vid >>>>>>> 10 dev eth0 bridge vlan add vid 10 dev vnet0 pvid untagged >>>>>>> bridge vlan add vid 0 dev vnet0 tagged where vnet0 has sub >>>>>>> interface vnet0.0. >>>>>>> >>>>>>> Here the admin have to know the egress policy is applied to a >>>>>>> frame twice in a certain order when it is transmitted from >>>>>>> the port vnet0 attached, that is, first, a frame with vid 10 >>>>>>> get untagged, and then, an untagged frame get >>>>>>> priority-tagged. >>>>>>> >>>>>>> This behavior looks difficult to know without previous >>>>>>> knowledge. Any good idea to avoid such a need for the admin's >>>>>>> additional knowledge? >>>>>> >>>>>> To me, the fact that there is vnet0.0 (or typically, there is >>>>>> eth0.0 in the guest or on the remote host) already tells the >>>>>> admin vlan 0 has to be tagged. The fact that we codify this in >>>>>> the policy makes it explicit. >>>>> >>>>> My worry is that the admin might not be able to guess how to use >>>>> bridge commands to enable priority-tag without any additional >>>>> hint in "man bridge", "bridge vlan help", etc. I actually >>>>> couldn't hit upon such a usage before seeing example commands you >>>>> gave, because I had never think the egress policy could be >>>>> applied twice. >>>>> >>>>>> >>>>>> However, I can see strong argument to be made for an addition >>>>>> egress policy attribute that could be for instance: >>>>>> >>>>>> bridge vlan add vid 10 dev eth0 pvid bridge vlan add vid 10 dev >>>>>> vnet0 pvid untagged prio_tag >>>>>> >>>>>> But this has the same connotations as wrt to egress policy. >>>>>> The 2 policies are applied: (1) untag the frame. (2) add >>>>>> priority_tag. >>>>>> >>>>>> (2) only happens if initial fame received on eth0 was priority >>>>>> tagged. >>>>> >>>>> If we do so, we will not be able to communicate using vlan 0 >>>>> interface under a certain circumstance. Eth0 can be receive mixed >>>>> untagged and priority-tagged frames according to the network >>>>> element it is connected to: for example, Open vSwitch can send >>>>> such two kinds of frames from the same port even if original >>>>> incoming frames belong to the same vlan. >>>> >>>> Which priority would you assign to the frame that was received >>>> untagged? >>> >>> Untagged frame's priority is by default 0, so I think 0 is likely. >>> >>> 802.1Q 6.9.1 i) The received priority value and the drop_eligible >>> parameter value are the values in the M_UNITDATA.indication. >>> >>> M_UNITDATA is passed from ISS. >>> >>> 802.1Q 6.7.1 The priority parameter provided in a data indication >>> primitive shall take the value of the Default User Priority parameter >>> for the Port through which the MAC frame was received. The default >>> value of this parameter is 0, it may be set by management in which >>> case the capability to set it to any of the values 0 through 7 shall >>> be provided. >>> >>>> >>>>> In this situation, we can only receive frames that is >>>>> priority-tagged when received on eth0. >>>> >>>> Not sure I understand. Let's look at this config: bridge vlan add >>>> vid 10 dev eth0 pvid bridge vlan add vid 10 dev vnet0 pvid untagged >>>> prio_tag >>>> >>>> Here, eth0 is allowed to receive vid 10 tagged, untagged, and >>>> prio_tagged (if we look at the patch 2 from this set). Now, frame >>>> is forwarded to vnet0. 1) if the frame had vid 10 in the tag or was >>>> untagged, it should probably be sent untagged. 2) if the frame had >>>> a priority tag, it should probably be sent as such. >>>> >>>> Now, I think a case could be made that if the frame had any >>>> priority markings in the vlan header, we should try to preserve >>>> those markings if prio_tag is turned on. We can assume value of 0 >>>> means not set. >>> >>> If we don't insert prio_tag when PCP is 0, we might receive mixed >>> priority-tagged and untagged frames on eth0. >> >> Right, and that's what you were trying to handle in your patch: >> >>> + /* PVID is set on this port. Any untagged or priority-tagged + >>> * ingress frame is considered to belong to this vlan. */ >> >> So, in this case we are prepared to handle the "mixed" scenario on ingress. >> >>> Even if we are sending frames from eth0.0 with some priority other >>> than 0, we could receive frames with priority 0 or untagged on the >>> other side of the bridge. >>> For example, if we receive untagged arp reply on the bridge port, we >>> migit not be able to communicate with such an end station, because >>> untagged reply will not be passed to eth0.0. >> >> So the ARP request was sent tagged, but the reply came back untagged? > > Yes, it can happen. > These are problematic cases. > > Example 1: > prio_tagged prio_tagged > +------------+ ---> +------------+ ---> +----------+ > |guest eth0.0|------|host1 Bridge|------|host2 eth0| > +------------+ <--- +------------+ <--- +----------+ > untagged untagged > > Note: Host2 eth0, which is an interface on Linux, can receive > priority-tagged frames if it doesn't have vlan 0 interface (eth0.0). Hmm.. Just to see if this works, I ran the this scenario with a dumb switch in the middle, and it did not work as you noted. I then realized that one of the kernels was rather old and after updating it, behaved differently. The communication still didn't work, but host2 behaved properly. >> >> How does that work when the end station is attached directly to the >> HW switch instead of a linux bridge? >> >> The station configures eth0.0 and sends priority-tagged traffic to >> the HW switch. If the HW switch sends back untagged traffic, then >> the untagged traffic will never reach eth0.0. > > Currently we cannot communicate using eth0.0 via directly connected > 802.1Q conformed switch, because we never receive priority-tagged frames > from the switch. > It is not a problem of Linux bridge and is why I wondered whether it > should be fixed by bridge or vlan 0 interface. > >> >>> >>>> >>>>> IMO, if prio_tag is configured, the bridge should send any >>>>> untagged frame as priority-tagged regardless of whatever it is on >>>>> eth0. >>>> >>>> Which priority would you use, 0? You are not guaranteed to >>>> properly deliver the traffic then for a configuration such as: VM: >>>> eth0: 10.0.0.1/24 eth0.0: 10.0.1.1/24 >>> >>> I'd like to use priority 0 for untagged frames. >>> >>> I am assuming that one of our goals is at least that eth0.0 comes to >>> be able to communicate with another end station. It seems to be hard >>> to use both eth0 and eth0.0 simultaneously. >> >> I understand, but I don't agree that we should always tag. >> >> Consider config: >> >> hw switch <---> (eth0: Linux Bridge: eth1) <--- (em1.0:end station) >> >> If the end station sends priority-tagged traffic it should receive >> priority tagged traffic back. Otherwise, untagged traffic may be >> dropped by the end station. This is true whether it is connected to >> the hw switch or Linux bridge. > > Though such a behavior is generally not necessary as far as I can read > 802.1Q spec, it is essential for vlan 0 interface on Linux, I think. > My proposal aims to resolve it at least when we use Linux bridge. > > Example configuration: > bridge vlan add vid 10 dev eth1 pvid untagged > bridge vlan add vid 10 dev eth0 > bridge vlan set prio_tag on dev eth1 > > Intended behavior: > > VID10-tagged prio_tagged > +---------+ <--- +------------------------+ <--- +-----------------+ > |hw switch|------|eth0: Linux Bridge: eth1|------|em1.0:end station| > +---------+ ---> +------------------------+ ---> +-----------------+ > VID10-tagged prio_tagged > (always if egress policy untagged) Ok, I think you've convinced me that this is the right approach. The only thing that I am not crazy about is the API. I'd almost want to introduce a new flag that can be set in a 'vlan add' or 'vlan set' command that communicates a new policy. Thanks -vlad > > Thanks, > > Toshiaki Makita > >> >> -vlad >> >>> >>> Thanks, >>> >>> Toshiaki Makita >>> >>>> >>>> -vlad >>>> >>>>> >>>>>> >>>>>> I think I am ok with either approach. Explicit vid 0 policy is >>>>>> easier for automatic provisioning. The flag based one is >>>>>> easier for admin/ manual provisioning. >>>>> >>>>> Supposing we have to add something to help or man in any case, I >>>>> think flag based is better. The format below seems to suitable >>>>> for a per-port policy. bridge vlan set prio_tag on dev vnet0 >>>>> >>>>> Thanks, >>>>> >>>>> Toshiaki Makita >>>>> >>>>>> >>>>>> -vlad. >>>>>> >>>>>> -vlad >>>>>> >>>>>> >>>>>> >>>>>> >>>>>>> >>>>>>>> >>>>>>>> Thanks -vlad >>>>>>>> >>>>>>>>> Thanks, >>>>>>>>> >>>>>>>>> Toshiaki Makita >>>>>>>>> >>>>>>>>>> >>>>>>>>>> How it is implemented internally in the kernel isn't as >>>>>>>>>> big of an issue. We can do it as a separate flag or as >>>>>>>>>> part of existing policy. >>>>>>>>>> >>>>>>>>>> -vlad >>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> Thanks, >>>>>>>>>>> >>>>>>>>>>> Toshiaki Makita >>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> -vlad >>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> Thanks, >>>>>>>>>>>>> >>>>>>>>>>>>> Toshiaki Makita >>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Thanks, >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Toshiaki Makita >>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> -- To unsubscribe from this list: send the >>>>>>>>>>>>>>>> line "unsubscribe netdev" in the body of a >>>>>>>>>>>>>>>> message to majordomo@...r.kernel.org More >>>>>>>>>>>>>>>> majordomo info at >>>>>>>>>>>>>>>> http://vger.kernel.org/majordomo-info.html >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> -- To unsubscribe from this list: send the line >>>>>>>>>>>>> "unsubscribe netdev" in the body of a message to >>>>>>>>>>>>> majordomo@...r.kernel.org More majordomo info at >>>>>>>>>>>>> http://vger.kernel.org/majordomo-info.html >>>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>> >>>>>>> >>>>>> >>>>> >>>>> >>> >>> > > > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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