[libvirt] [PATCH] nwfilter: intantiate filters on loading driver
Before using filters binding filters instantiation was done by hypervisors drivers initialization code (qemu was the only such hypervisor). Now qemu reconnection done supposes it should be done by nwfilter driver probably. Let's add this missing step. Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy@virtuozzo.com> --- src/nwfilter/nwfilter_driver.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/src/nwfilter/nwfilter_driver.c b/src/nwfilter/nwfilter_driver.c index 1ee5162..1ab906f 100644 --- a/src/nwfilter/nwfilter_driver.c +++ b/src/nwfilter/nwfilter_driver.c @@ -264,6 +264,9 @@ nwfilterStateInitialize(bool privileged, if (virNWFilterBindingObjListLoadAllConfigs(driver->bindings, driver->bindingDir) < 0) goto error; + if (virNWFilterBuildAll(driver, false) < 0) + goto error; + nwfilterDriverUnlock(); return 0; -- 1.8.3.1
On 10/15/18 4:26 AM, Nikolay Shirokovskiy wrote:
Before using filters binding filters instantiation was done by hypervisors drivers initialization code (qemu was the only such hypervisor). Now qemu reconnection done supposes it should be done by nwfilter driver probably. Let's add this missing step.
Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy@virtuozzo.com> --- src/nwfilter/nwfilter_driver.c | 3 +++ 1 file changed, 3 insertions(+)
If there's research you've done where the instantiation was done before introduction of the nwfilter bindings that would be really helpful... I found that virNWFilterBuildAll was introduced in commit 3df907bfff. There were 2 callers for it: 1. virNWFilterTriggerRebuildImpl 2. nwfilterStateReload The former called as part of the virNWFilterConfLayerInit callback during nwfilterStateInitialize (about 50 lines earlier). So how does calling this now w/ @false help things during the state initialize processing? John
diff --git a/src/nwfilter/nwfilter_driver.c b/src/nwfilter/nwfilter_driver.c index 1ee5162..1ab906f 100644 --- a/src/nwfilter/nwfilter_driver.c +++ b/src/nwfilter/nwfilter_driver.c @@ -264,6 +264,9 @@ nwfilterStateInitialize(bool privileged, if (virNWFilterBindingObjListLoadAllConfigs(driver->bindings, driver->bindingDir) < 0) goto error;
+ if (virNWFilterBuildAll(driver, false) < 0) + goto error; + nwfilterDriverUnlock();
return 0;
On 29.10.2018 22:37, John Ferlan wrote:
On 10/15/18 4:26 AM, Nikolay Shirokovskiy wrote:
Before using filters binding filters instantiation was done by hypervisors drivers initialization code (qemu was the only such hypervisor). Now qemu reconnection done supposes it should be done by nwfilter driver probably. Let's add this missing step.
Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy@virtuozzo.com> --- src/nwfilter/nwfilter_driver.c | 3 +++ 1 file changed, 3 insertions(+)
If there's research you've done where the instantiation was done before introduction of the nwfilter bindings that would be really helpful...
I found that virNWFilterBuildAll was introduced in commit 3df907bfff. There were 2 callers for it:
1. virNWFilterTriggerRebuildImpl 2. nwfilterStateReload
The former called as part of the virNWFilterConfLayerInit callback during nwfilterStateInitialize (about 50 lines earlier).
Right but virNWFilterTriggerRebuildImpl is not actually called, it is set as rebuild callback. This rebuild callback can be called in virNWFilterObjTestUnassignDef and virNWFilterObjListAssignDef. The former is not called during nwfilter driver init. The latter is called as part of virNWFilterObjListLoadAllConfigs but rebuild callback is never called on this path because the list is empty (callback is called only on updates when filter with same name is already present in the list). So virNWFilterBuildAll is not called on nwfilter driver init.
So how does calling this now w/ @false help things during the state initialize processing?
Before filters bindings nwfilter driver only loads filters on it's init function. Then qemu driver for example on reconnection called: qemuProcessFiltersInstantiate virDomainConfNWFilterInstantiate nwfilterInstantiateFilter virNWFilterInstantiateFilter and filter rules gets [re]instantiated. Now virNWFilterInstantiateFilter returns without actual instantiating because virNWFilterBindingLookupByPortDev finds binding which is loaded on nwfilter driver initialization. The consequences is that if somebody cleans rules between libvirtd stop and start then rules won't get instantiated again. The fix is to [re]instantiate bindings in nwfilter driver init right after binding and filters are loaded. With @false argument virNWFilterBuildAll call virNWFilterInstantiateFilter for each binding - just what we need to. @true is used by virNWFilterObjListAssignDef/virNWFilterObjTestUnassignDef to use @newDef of object filter during instantiation etc. Nikolay
John
diff --git a/src/nwfilter/nwfilter_driver.c b/src/nwfilter/nwfilter_driver.c index 1ee5162..1ab906f 100644 --- a/src/nwfilter/nwfilter_driver.c +++ b/src/nwfilter/nwfilter_driver.c @@ -264,6 +264,9 @@ nwfilterStateInitialize(bool privileged, if (virNWFilterBindingObjListLoadAllConfigs(driver->bindings, driver->bindingDir) < 0) goto error;
+ if (virNWFilterBuildAll(driver, false) < 0) + goto error; + nwfilterDriverUnlock();
return 0;
On 10/30/18 3:24 AM, Nikolay Shirokovskiy wrote:
On 29.10.2018 22:37, John Ferlan wrote:
On 10/15/18 4:26 AM, Nikolay Shirokovskiy wrote:
Before using filters binding filters instantiation was done by hypervisors drivers initialization code (qemu was the only such hypervisor). Now qemu reconnection done supposes it should be done by nwfilter driver probably. Let's add this missing step.
Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy@virtuozzo.com> --- src/nwfilter/nwfilter_driver.c | 3 +++ 1 file changed, 3 insertions(+)
If there's research you've done where the instantiation was done before introduction of the nwfilter bindings that would be really helpful...
I found that virNWFilterBuildAll was introduced in commit 3df907bfff. There were 2 callers for it:
1. virNWFilterTriggerRebuildImpl 2. nwfilterStateReload
The former called as part of the virNWFilterConfLayerInit callback during nwfilterStateInitialize (about 50 lines earlier).
First off let me say you certainly find a lot of interesting bugs/issues that are complex and that's good. Often times I wonder how you trip across things or how to quantify what you've found. Some are simpler than others. This one on the surface would seem to be simple, but I keep wondering is there a downside. The nwfilter processing is kindly said rather strange, complex, and to a degree fragile. Thus when patches come along they are met with greater scrutiny. From just reading the commit message here I don't get a sense for the problem and why the solution fixes it. So I'm left to try and research myself and ask a lot of questions. BTW, some of the detail provided in this response is really useful as either part of a cover or after the --- in the single patch. I would think you'd "know" when you've done lots of research into a problem that providing reviews more than a mere hint would be useful! For nwfilter bindings, it's hard to imagine this is one of those - it just happened type events. There seems to be a very specific sequence that's missing from the commit description.
Right but virNWFilterTriggerRebuildImpl is not actually called, it is set as rebuild callback. This rebuild callback can be called in virNWFilterObjTestUnassignDef and virNWFilterObjListAssignDef.
Ah yes, the virNWFilterConfLayerInit sets up the context to call the virNWFilterTriggerRebuildImpl for virNWFilterObjTestUnassignDef and virNWFilterObjListAssignDef and no I see it doesn't directly call the virNWFilterBuildAll. Still, I don't see where the processing of a rebuild callback is different than prior to commit 3df907bfff - at least with respect to the two places which would call it.
The former is not called during nwfilter driver init. The latter is called as part of virNWFilterObjListLoadAllConfigs but rebuild callback is never called on this path because the list is empty
Which list? nwfilters? nwfilter-bindings?
(callback is called only on updates when filter with same name is already present in the list). So virNWFilterBuildAll is not called on nwfilter driver init.
And similar logic was run was before commit 3df907bfff? This direct correlation is the part I'm missing. What follows is my understand of the before and after - some of the before is a bit of hand waving. Perhaps Daniel can chime in and "fix up" inaccuracies. Prior to commit 3df907bfff, the virNWFilterDomainFWUpdateCB was only run when the domain was active. IOW: The domain would need to preload the bindings in "hidden" locations such that the various vnetX (or whatever target dev for the <interface>) devices would load the whichever <filterref> was assocated. When libvirtd was restarted the processing was similar and the "magic" of reinstantiation was provided through virNWFilterRegisterCallbackDriver in (for example) qemuStateInitialize. That I believe is the part you describe in your commit as "Before using filters binding filters instantiation was done by hypervisors drivers initialization code (qemu was the only such hypervisor)." - although I see LXC and UML drivers changed as well, so I could be wrong with my assumption of what you meant. After that commit, rather than requiring qemuStateInitialize to register a callback driver which somehow magically loaded the filters for running guests, the nwfilter-bindings for running guests are loaded via (for example) /var/run/libvirt/vnet0.xml file processing during virNWFilterBindingObjListLoadAllConfigs (change in the previous commit 57f5621f46). So rather than the rebuild processing magically occurring in the background by some hypervisor driver performing the rebuild callback processing. Since virRegisterStateDriver (and friends) for nwfilter are run before qemu, IIUC that means the filter bindings would be loaded already. It's all a complicated dance. So in this after model for running guests it seems to me that the exact same processing occurs. Now if someone during libvirtd's stop period does something "outside the scope" of libvirt to change things that libvirt wouldn't otherwise be notified about, then all bets are off. Similar for other pieces of the code such as CPU's, Memory, Storage, etc.; however, for those there is a query at reinitialization time that can help reconcile differences due to perhaps missed events from qemu because libvirtd wasn't processing. Not sure there's something similar to query for nwfilter and bindings, but I assume there wouldn't have been any before either.
So how does calling this now w/ @false help things during the state initialize processing?
Before filters bindings nwfilter driver only loads filters on it's init function. Then qemu driver for example on reconnection called:
qemuProcessFiltersInstantiate virDomainConfNWFilterInstantiate nwfilterInstantiateFilter virNWFilterInstantiateFilter
and filter rules gets [re]instantiated.
From commit f14c37ce4c2
Now virNWFilterInstantiateFilter returns without actual instantiating because virNWFilterBindingLookupByPortDev finds binding which is loaded on nwfilter driver initialization> The consequences is that if somebody cleans rules between libvirtd stop and start then rules won't get instantiated again.
and this is the "key point" you are trying to reconcile, true?
The fix is to [re]instantiate bindings in nwfilter driver init right after binding and filters are loaded. With @false argument virNWFilterBuildAll call virNWFilterInstantiateFilter for each binding - just what we need to. @true is used by virNWFilterObjListAssignDef/virNWFilterObjTestUnassignDef to use @newDef of object filter during instantiation etc.
Nikolay
Can you provided a concrete example showing your steps to help clear up things for me? Using just one filter is fine. What does the guest look like before whatever it is you do is done? What steps do you take? Then what does it look like afterwards? What would you expect? If you did the same/similar steps prior to the referenced commits what was the result? As an "aside", it's been noted somewhere admins should not be messing with nwfilter bindings. If someone "cleans rules" during a period when libvirtd is stopped, then what is "expected" to happen afterwards. Tks John
John
diff --git a/src/nwfilter/nwfilter_driver.c b/src/nwfilter/nwfilter_driver.c index 1ee5162..1ab906f 100644 --- a/src/nwfilter/nwfilter_driver.c +++ b/src/nwfilter/nwfilter_driver.c @@ -264,6 +264,9 @@ nwfilterStateInitialize(bool privileged, if (virNWFilterBindingObjListLoadAllConfigs(driver->bindings, driver->bindingDir) < 0) goto error;
+ if (virNWFilterBuildAll(driver, false) < 0) + goto error; + nwfilterDriverUnlock();
return 0;
On 31.10.2018 16:14, John Ferlan wrote:
On 10/30/18 3:24 AM, Nikolay Shirokovskiy wrote:
On 29.10.2018 22:37, John Ferlan wrote:
On 10/15/18 4:26 AM, Nikolay Shirokovskiy wrote:
Before using filters binding filters instantiation was done by hypervisors drivers initialization code (qemu was the only such hypervisor). Now qemu reconnection done supposes it should be done by nwfilter driver probably. Let's add this missing step.
Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy@virtuozzo.com> --- src/nwfilter/nwfilter_driver.c | 3 +++ 1 file changed, 3 insertions(+)
If there's research you've done where the instantiation was done before introduction of the nwfilter bindings that would be really helpful...
I found that virNWFilterBuildAll was introduced in commit 3df907bfff. There were 2 callers for it:
1. virNWFilterTriggerRebuildImpl 2. nwfilterStateReload
The former called as part of the virNWFilterConfLayerInit callback during nwfilterStateInitialize (about 50 lines earlier).
First off let me say you certainly find a lot of interesting bugs/issues that are complex and that's good. Often times I wonder how you trip across things or how to quantify what you've found. Some are simpler than others. This one on the surface would seem to be simple, but I keep wondering is there a downside.
The issue is related to my recent posts: [1] [RFC] Faster libvirtd restart with nwfilter rules https://www.redhat.com/archives/libvir-list/2018-September/msg01206.html which continues here: https://www.redhat.com/archives/libvir-list/2018-October/msg00657.html In short if there is lots of VMs with filters then libvirtd restart takes a lot of time during which libvirtd is unresponsive. By the way the issue is found in libvirt versions 3.9.0 and ealier (don't know of newer versions, Virtuozzo is based on 3.9.0 now, just like Centos7 :) ) And attempts to fix it: [2] [PATCH RFC 0/4] nwfilter: don't reinstantiate filters if they are not changed https://www.redhat.com/archives/libvir-list/2018-October/msg00904.html [3] [PATCH v2 0/2] nwfilter: don't reinstantiate rules if there is no need to https://www.redhat.com/archives/libvir-list/2018-October/msg01317.html And the reason I started v2 is Laine mentioned that it is important to reinstantiate rules on restart (v1 do not care if somebody messed tables). And I discovered that upstream version stops reinstantiating rules at all after introducing filters bindings. And this functionality is old: commit cf6f8b9a9720fe5323a84e690de9fbf8ba41f6ac Author: Stefan Berger <stefanb@us.ibm.com> Date: Mon Aug 16 12:59:54 2010 -0400 nwfilter: extend nwfilter reload support
The nwfilter processing is kindly said rather strange, complex, and to a degree fragile. Thus when patches come along they are met with greater scrutiny. From just reading the commit message here I don't get a sense for the problem and why the solution fixes it. So I'm left to try and research myself and ask a lot of questions.
BTW, some of the detail provided in this response is really useful as either part of a cover or after the --- in the single patch. I would think you'd "know" when you've done lots of research into a problem that providing reviews more than a mere hint would be useful! For nwfilter bindings, it's hard to imagine this is one of those - it just happened type events. There seems to be a very specific sequence that's missing from the commit description.
Right but virNWFilterTriggerRebuildImpl is not actually called, it is set as rebuild callback. This rebuild callback can be called in virNWFilterObjTestUnassignDef and virNWFilterObjListAssignDef.
Ah yes, the virNWFilterConfLayerInit sets up the context to call the virNWFilterTriggerRebuildImpl for virNWFilterObjTestUnassignDef and virNWFilterObjListAssignDef and no I see it doesn't directly call the virNWFilterBuildAll.
Still, I don't see where the processing of a rebuild callback is different than prior to commit 3df907bfff - at least with respect to the two places which would call it.
Right processing did not changed, I just wanted to show that virNWFilterBuildAll is not called now and before on nwfilter init. By the way 3df907bfff introduced virNWFilterBuildAll but not its functionality.
The former is not called during nwfilter driver init. The latter is called as part of virNWFilterObjListLoadAllConfigs but rebuild callback is never called on this path because the list is empty
Which list? nwfilters? nwfilter-bindings?
nwfilters. And again by the way this is a bit vague statement. The matter is not list is not empty but we won't find same name in it when virNWFilterObjListAssignDef is called during driver init (which is said in below paragraph part in other words too)
(callback is called only on updates when filter with same name is already present in the list). So virNWFilterBuildAll is not called on nwfilter driver init.
And similar logic was run was before commit 3df907bfff? This direct
Yes
correlation is the part I'm missing. What follows is my understand of the before and after - some of the before is a bit of hand waving. Perhaps Daniel can chime in and "fix up" inaccuracies.
Prior to commit 3df907bfff, the virNWFilterDomainFWUpdateCB was only run when the domain was active. IOW: The domain would need to preload the bindings in "hidden" locations such that the various vnetX (or whatever target dev for the <interface>) devices would load the whichever <filterref> was assocated. When libvirtd was restarted the processing was similar and the "magic" of reinstantiation was provided through virNWFilterRegisterCallbackDriver in (for example) qemuStateInitialize. That I believe is the part you describe in your commit as "Before using filters binding filters instantiation was done by hypervisors drivers initialization code (qemu was the only such hypervisor)." - although I see LXC and UML drivers changed as well, so I could be wrong with my assumption of what you meant.
Not quite correct. virNWFilterRegisterCallbackDriver is used when filter definition is updated and we need to reinstantiate filter for every active domain that uses it. But libvirtd restart is different, in this case reinstantiation occured only in qemu driver in reconnection process, the driver of reinstantiation was hypervisor.
After that commit, rather than requiring qemuStateInitialize to register a callback driver which somehow magically loaded the filters for running guests, the nwfilter-bindings for running guests are loaded via (for example) /var/run/libvirt/vnet0.xml file processing during virNWFilterBindingObjListLoadAllConfigs (change in the previous commit 57f5621f46). So rather than the rebuild processing magically occurring in the background by some hypervisor driver performing the rebuild callback processing. Since virRegisterStateDriver (and friends) for nwfilter are run before qemu, IIUC that means the filter bindings would be loaded already. It's all a complicated dance.
Yes loaded, but not reinstatiated.
So in this after model for running guests it seems to me that the exact same processing occurs. Now if someone during libvirtd's stop period does something "outside the scope" of libvirt to change things that libvirt wouldn't otherwise be notified about, then all bets are off. Similar for other pieces of the code such as CPU's, Memory, Storage, etc.; however, for those there is a query at reinitialization time that can help reconcile differences due to perhaps missed events from qemu because libvirtd wasn't processing. Not sure there's something similar to query for nwfilter and bindings, but I assume there wouldn't have been any before either.
So how does calling this now w/ @false help things during the state initialize processing?
Before filters bindings nwfilter driver only loads filters on it's init function. Then qemu driver for example on reconnection called:
qemuProcessFiltersInstantiate virDomainConfNWFilterInstantiate nwfilterInstantiateFilter virNWFilterInstantiateFilter
and filter rules gets [re]instantiated.
From commit f14c37ce4c2
Now virNWFilterInstantiateFilter returns without actual instantiating because virNWFilterBindingLookupByPortDev finds binding which is loaded on nwfilter driver initialization> The consequences is that if somebody cleans rules between libvirtd stop and start then rules won't get instantiated again.
and this is the "key point" you are trying to reconcile, true?
Exactly
The fix is to [re]instantiate bindings in nwfilter driver init right after binding and filters are loaded. With @false argument virNWFilterBuildAll call virNWFilterInstantiateFilter for each binding - just what we need to. @true is used by virNWFilterObjListAssignDef/virNWFilterObjTestUnassignDef to use @newDef of object filter during instantiation etc.
Nikolay
Can you provided a concrete example showing your steps to help clear up things for me? Using just one filter is fine. What does the guest look like before whatever it is you do is done? What steps do you take? Then what does it look like afterwards? What would you expect? If you did the same/similar steps prior to the referenced commits what was the result?
If you mean a more concrete usecase when such a clearing of firewall tables occurs when libvirtd is stopped - I don't have one. I just restore old functionality and also motivated by Laine comment to my first patch series. Or may be I don't understand you. Thanx for a review. Nikolay
As an "aside", it's been noted somewhere admins should not be messing with nwfilter bindings. If someone "cleans rules" during a period when libvirtd is stopped, then what is "expected" to happen afterwards.
Tks
John
John
diff --git a/src/nwfilter/nwfilter_driver.c b/src/nwfilter/nwfilter_driver.c index 1ee5162..1ab906f 100644 --- a/src/nwfilter/nwfilter_driver.c +++ b/src/nwfilter/nwfilter_driver.c @@ -264,6 +264,9 @@ nwfilterStateInitialize(bool privileged, if (virNWFilterBindingObjListLoadAllConfigs(driver->bindings, driver->bindingDir) < 0) goto error;
+ if (virNWFilterBuildAll(driver, false) < 0) + goto error; + nwfilterDriverUnlock();
return 0;
On 10/31/18 10:41 AM, Nikolay Shirokovskiy wrote:
On 31.10.2018 16:14, John Ferlan wrote:
On 10/30/18 3:24 AM, Nikolay Shirokovskiy wrote:
On 29.10.2018 22:37, John Ferlan wrote:
On 10/15/18 4:26 AM, Nikolay Shirokovskiy wrote:
Before using filters binding filters instantiation was done by hypervisors drivers initialization code (qemu was the only such hypervisor). Now qemu reconnection done supposes it should be done by nwfilter driver probably. Let's add this missing step.
Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy@virtuozzo.com> --- src/nwfilter/nwfilter_driver.c | 3 +++ 1 file changed, 3 insertions(+)
If there's research you've done where the instantiation was done before introduction of the nwfilter bindings that would be really helpful...
I found that virNWFilterBuildAll was introduced in commit 3df907bfff. There were 2 callers for it:
1. virNWFilterTriggerRebuildImpl 2. nwfilterStateReload
The former called as part of the virNWFilterConfLayerInit callback during nwfilterStateInitialize (about 50 lines earlier).
First off let me say you certainly find a lot of interesting bugs/issues that are complex and that's good. Often times I wonder how you trip across things or how to quantify what you've found. Some are simpler than others. This one on the surface would seem to be simple, but I keep wondering is there a downside.
The issue is related to my recent posts:
[1] [RFC] Faster libvirtd restart with nwfilter rules https://www.redhat.com/archives/libvir-list/2018-September/msg01206.html which continues here: https://www.redhat.com/archives/libvir-list/2018-October/msg00657.html
In short if there is lots of VMs with filters then libvirtd restart takes a lot of time during which libvirtd is unresponsive. By the way the issue is found in libvirt versions 3.9.0 and ealier (don't know of newer versions, Virtuozzo is based on 3.9.0 now, just like Centos7 :) )
So many different issues - trying to focus on just the one for this particular patch.
And attempts to fix it:
[2] [PATCH RFC 0/4] nwfilter: don't reinstantiate filters if they are not changed https://www.redhat.com/archives/libvir-list/2018-October/msg00904.html
[3] [PATCH v2 0/2] nwfilter: don't reinstantiate rules if there is no need to https://www.redhat.com/archives/libvir-list/2018-October/msg01317.html
And the reason I started v2 is Laine mentioned that it is important to reinstantiate rules on restart (v1 do not care if somebody messed tables).
I've seen the patches and even read some briefly, but still need to take this particular patch as separate from those.
And I discovered that upstream version stops reinstantiating rules at all after introducing filters bindings. And this functionality is old:
So the key is "when" did that happen? That is can you pinpoint or bisect a time in history where the filters were instantiated? And by instantiated what exactly (call) are you referencing?
commit cf6f8b9a9720fe5323a84e690de9fbf8ba41f6ac Author: Stefan Berger <stefanb@us.ibm.com> Date: Mon Aug 16 12:59:54 2010 -0400
nwfilter: extend nwfilter reload support
Yes, nwfilter is old, brittle, and in need of attention. Not sure anyone really wants to take on the task though! I just realized I never got the common object code implemented there. Mostly because of lock issues. Suffice to say there's more "interesting" changes in the nwfilter space being discussed internally.
The nwfilter processing is kindly said rather strange, complex, and to a degree fragile. Thus when patches come along they are met with greater scrutiny. From just reading the commit message here I don't get a sense for the problem and why the solution fixes it. So I'm left to try and research myself and ask a lot of questions.
BTW, some of the detail provided in this response is really useful as either part of a cover or after the --- in the single patch. I would think you'd "know" when you've done lots of research into a problem that providing reviews more than a mere hint would be useful! For nwfilter bindings, it's hard to imagine this is one of those - it just happened type events. There seems to be a very specific sequence that's missing from the commit description.
Right but virNWFilterTriggerRebuildImpl is not actually called, it is set as rebuild callback. This rebuild callback can be called in virNWFilterObjTestUnassignDef and virNWFilterObjListAssignDef.
Ah yes, the virNWFilterConfLayerInit sets up the context to call the virNWFilterTriggerRebuildImpl for virNWFilterObjTestUnassignDef and virNWFilterObjListAssignDef and no I see it doesn't directly call the virNWFilterBuildAll.
Still, I don't see where the processing of a rebuild callback is different than prior to commit 3df907bfff - at least with respect to the two places which would call it.
Right processing did not changed, I just wanted to show that virNWFilterBuildAll is not called now and before on nwfilter init. By the way 3df907bfff introduced virNWFilterBuildAll but not its functionality.
So prior to that commit made during v4.5.0 development, were the filters instantiated? If so, then what changed caused them to no longer be?
The former is not called during nwfilter driver init. The latter is called as part of virNWFilterObjListLoadAllConfigs but rebuild callback is never called on this path because the list is empty
Which list? nwfilters? nwfilter-bindings?
nwfilters. And again by the way this is a bit vague statement. The matter is not list is not empty but we won't find same name in it when virNWFilterObjListAssignDef is called during driver init (which is said in below paragraph part in other words too)
If I restart libvirtd I see the same nwfilter list being generated. If I have a domain running I see the filter binding for that domain. What's missing? When a domain isn't started, it finds the nwfilter and "loads" it into nwfilter binding. That rule is applied somewhere, right? That rule remains in effect for the domain regardless of how many libvirtd restarts there are doesn't it? It seems as if you're saying we need to reapply the filter on libvirtd restart.
(callback is called only on updates when filter with same name is already present in the list). So virNWFilterBuildAll is not called on nwfilter driver init.
And similar logic was run was before commit 3df907bfff? This direct
Yes
correlation is the part I'm missing. What follows is my understand of the before and after - some of the before is a bit of hand waving. Perhaps Daniel can chime in and "fix up" inaccuracies.
Prior to commit 3df907bfff, the virNWFilterDomainFWUpdateCB was only run when the domain was active. IOW: The domain would need to preload the bindings in "hidden" locations such that the various vnetX (or whatever target dev for the <interface>) devices would load the whichever <filterref> was assocated. When libvirtd was restarted the processing was similar and the "magic" of reinstantiation was provided through virNWFilterRegisterCallbackDriver in (for example) qemuStateInitialize. That I believe is the part you describe in your commit as "Before using filters binding filters instantiation was done by hypervisors drivers initialization code (qemu was the only such hypervisor)." - although I see LXC and UML drivers changed as well, so I could be wrong with my assumption of what you meant.
Not quite correct. virNWFilterRegisterCallbackDriver is used when filter definition is updated and we need to reinstantiate filter for every active domain that uses it. But libvirtd restart is different, in this case reinstantiation occured only in qemu driver in reconnection process, the driver of reinstantiation was hypervisor.
After that commit, rather than requiring qemuStateInitialize to register a callback driver which somehow magically loaded the filters for running guests, the nwfilter-bindings for running guests are loaded via (for example) /var/run/libvirt/vnet0.xml file processing during virNWFilterBindingObjListLoadAllConfigs (change in the previous commit 57f5621f46). So rather than the rebuild processing magically occurring in the background by some hypervisor driver performing the rebuild callback processing. Since virRegisterStateDriver (and friends) for nwfilter are run before qemu, IIUC that means the filter bindings would be loaded already. It's all a complicated dance.
Yes loaded, but not reinstatiated.
What call is being done in the normal path that isn't being done in this libvirtd restart path? Whatever the STEP_APPLY_CURRENT does? Or the virNWFilterInstantiateFilter from nwfilterBindingCreateXML? If the latter, then rather than using BuildAll, why not InstantiateFilter from virNWFilterBindingObjListLoadStatus? I keep coming back to once things are instantiated from the initial libvirtd start why is it that the libvirtd restart processing needs to do make the same call?
So in this after model for running guests it seems to me that the exact same processing occurs. Now if someone during libvirtd's stop period does something "outside the scope" of libvirt to change things that libvirt wouldn't otherwise be notified about, then all bets are off. Similar for other pieces of the code such as CPU's, Memory, Storage, etc.; however, for those there is a query at reinitialization time that can help reconcile differences due to perhaps missed events from qemu because libvirtd wasn't processing. Not sure there's something similar to query for nwfilter and bindings, but I assume there wouldn't have been any before either.
So how does calling this now w/ @false help things during the state initialize processing?
Before filters bindings nwfilter driver only loads filters on it's init function. Then qemu driver for example on reconnection called:
qemuProcessFiltersInstantiate virDomainConfNWFilterInstantiate nwfilterInstantiateFilter virNWFilterInstantiateFilter
and filter rules gets [re]instantiated.
From commit f14c37ce4c2
Now virNWFilterInstantiateFilter returns without actual instantiating because virNWFilterBindingLookupByPortDev finds binding which is loaded on nwfilter driver initialization> The consequences is that if somebody cleans rules between libvirtd stop and start then rules won't get instantiated again.
and this is the "key point" you are trying to reconcile, true?
Exactly
The fix is to [re]instantiate bindings in nwfilter driver init right after binding and filters are loaded. With @false argument virNWFilterBuildAll call virNWFilterInstantiateFilter for each binding - just what we need to. @true is used by virNWFilterObjListAssignDef/virNWFilterObjTestUnassignDef to use @newDef of object filter during instantiation etc.
Nikolay
Can you provided a concrete example showing your steps to help clear up things for me? Using just one filter is fine. What does the guest look like before whatever it is you do is done? What steps do you take? Then what does it look like afterwards? What would you expect? If you did the same/similar steps prior to the referenced commits what was the result?
If you mean a more concrete usecase when such a clearing of firewall tables occurs when libvirtd is stopped - I don't have one. I just restore old functionality and also motivated by Laine comment to my first patch series. Or may be I don't understand you.
Well having a use case would certainly help. It's unclear what the libvirtd restart processing isn't doing now that it may have been doing before nwfilter bindings were added. You keep saying instantiate and I keep asking what was done before that isn't being done now. Then you're throwing in a few other patches and I'm lost. John
Thanx for a review.
Nikolay
As an "aside", it's been noted somewhere admins should not be messing with nwfilter bindings. If someone "cleans rules" during a period when libvirtd is stopped, then what is "expected" to happen afterwards.
Tks
John
John
diff --git a/src/nwfilter/nwfilter_driver.c b/src/nwfilter/nwfilter_driver.c index 1ee5162..1ab906f 100644 --- a/src/nwfilter/nwfilter_driver.c +++ b/src/nwfilter/nwfilter_driver.c @@ -264,6 +264,9 @@ nwfilterStateInitialize(bool privileged, if (virNWFilterBindingObjListLoadAllConfigs(driver->bindings, driver->bindingDir) < 0) goto error;
+ if (virNWFilterBuildAll(driver, false) < 0) + goto error; + nwfilterDriverUnlock();
return 0;
On 01.11.2018 03:48, John Ferlan wrote:
On 10/31/18 10:41 AM, Nikolay Shirokovskiy wrote:
On 31.10.2018 16:14, John Ferlan wrote:
On 10/30/18 3:24 AM, Nikolay Shirokovskiy wrote:
On 29.10.2018 22:37, John Ferlan wrote:
On 10/15/18 4:26 AM, Nikolay Shirokovskiy wrote:
Before using filters binding filters instantiation was done by hypervisors drivers initialization code (qemu was the only such hypervisor). Now qemu reconnection done supposes it should be done by nwfilter driver probably. Let's add this missing step.
Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy@virtuozzo.com> --- src/nwfilter/nwfilter_driver.c | 3 +++ 1 file changed, 3 insertions(+)
If there's research you've done where the instantiation was done before introduction of the nwfilter bindings that would be really helpful...
I found that virNWFilterBuildAll was introduced in commit 3df907bfff. There were 2 callers for it:
1. virNWFilterTriggerRebuildImpl 2. nwfilterStateReload
The former called as part of the virNWFilterConfLayerInit callback during nwfilterStateInitialize (about 50 lines earlier).
First off let me say you certainly find a lot of interesting bugs/issues that are complex and that's good. Often times I wonder how you trip across things or how to quantify what you've found. Some are simpler than others. This one on the surface would seem to be simple, but I keep wondering is there a downside.
The issue is related to my recent posts:
[1] [RFC] Faster libvirtd restart with nwfilter rules https://www.redhat.com/archives/libvir-list/2018-September/msg01206.html which continues here: https://www.redhat.com/archives/libvir-list/2018-October/msg00657.html
In short if there is lots of VMs with filters then libvirtd restart takes a lot of time during which libvirtd is unresponsive. By the way the issue is found in libvirt versions 3.9.0 and ealier (don't know of newer versions, Virtuozzo is based on 3.9.0 now, just like Centos7 :) )
So many different issues - trying to focus on just the one for this particular patch.
And attempts to fix it:
[2] [PATCH RFC 0/4] nwfilter: don't reinstantiate filters if they are not changed https://www.redhat.com/archives/libvir-list/2018-October/msg00904.html
[3] [PATCH v2 0/2] nwfilter: don't reinstantiate rules if there is no need to https://www.redhat.com/archives/libvir-list/2018-October/msg01317.html
And the reason I started v2 is Laine mentioned that it is important to reinstantiate rules on restart (v1 do not care if somebody messed tables).
I've seen the patches and even read some briefly, but still need to take this particular patch as separate from those.
And I discovered that upstream version stops reinstantiating rules at all after introducing filters bindings. And this functionality is old:
So the key is "when" did that happen? That is can you pinpoint or bisect a time in history where the filters were instantiated? And by instantiated what exactly (call) are you referencing?
The below commit is the one. It adds instantiating filters on libvirtd restart. By instantiating I mean that firewall rules correspondent to filters are actually get [re]added to iptables etc.
commit cf6f8b9a9720fe5323a84e690de9fbf8ba41f6ac Author: Stefan Berger <stefanb@us.ibm.com> Date: Mon Aug 16 12:59:54 2010 -0400
nwfilter: extend nwfilter reload support
Yes, nwfilter is old, brittle, and in need of attention. Not sure anyone really wants to take on the task though! I just realized I never got the common object code implemented there. Mostly because of lock issues. Suffice to say there's more "interesting" changes in the nwfilter space being discussed internally.
The nwfilter processing is kindly said rather strange, complex, and to a degree fragile. Thus when patches come along they are met with greater scrutiny. From just reading the commit message here I don't get a sense for the problem and why the solution fixes it. So I'm left to try and research myself and ask a lot of questions.
BTW, some of the detail provided in this response is really useful as either part of a cover or after the --- in the single patch. I would think you'd "know" when you've done lots of research into a problem that providing reviews more than a mere hint would be useful! For nwfilter bindings, it's hard to imagine this is one of those - it just happened type events. There seems to be a very specific sequence that's missing from the commit description.
Right but virNWFilterTriggerRebuildImpl is not actually called, it is set as rebuild callback. This rebuild callback can be called in virNWFilterObjTestUnassignDef and virNWFilterObjListAssignDef.
Ah yes, the virNWFilterConfLayerInit sets up the context to call the virNWFilterTriggerRebuildImpl for virNWFilterObjTestUnassignDef and virNWFilterObjListAssignDef and no I see it doesn't directly call the virNWFilterBuildAll.
Still, I don't see where the processing of a rebuild callback is different than prior to commit 3df907bfff - at least with respect to the two places which would call it.
Right processing did not changed, I just wanted to show that virNWFilterBuildAll is not called now and before on nwfilter init. By the way 3df907bfff introduced virNWFilterBuildAll but not its functionality.
So prior to that commit made during v4.5.0 development, were the filters instantiated? If so, then what changed caused them to no longer be?
Yes they were. Looks like reinstatiation was lost in commit 57f5621f464b8df5671cbe5df6bab3cf006981dd Author: Daniel P. Berrangé <berrange@redhat.com> Date: Thu Apr 26 18:34:33 2018 +0100 nwfilter: keep track of active filter bindings nwfilterInstantiateFilter is called from reconnection code. Before the patch we always instantiate rules, after we do not because we return early in nwfilterInstantiateFilter because binding already exist (it is loaded from status).
The former is not called during nwfilter driver init. The latter is called as part of virNWFilterObjListLoadAllConfigs but rebuild callback is never called on this path because the list is empty
Which list? nwfilters? nwfilter-bindings?
nwfilters. And again by the way this is a bit vague statement. The matter is not list is not empty but we won't find same name in it when virNWFilterObjListAssignDef is called during driver init (which is said in below paragraph part in other words too)
If I restart libvirtd I see the same nwfilter list being generated. If I have a domain running I see the filter binding for that domain. What's missing?
The problem is not nwfilters or nwbindings are lost on restart. The problem is only with rules in iptables etc and only if somebody cleans them up between libvirtd stop and start. Probably this branch of discussion is a bit unrelated to problem. We explore whether virNWFilterBuildAll is called on nwfilter init currently or not AFAIK. It is not, otherwise there is no need in this patch.
When a domain isn't started, it finds the nwfilter and "loads" it into nwfilter binding. That rule is applied somewhere, right? That rule remains in effect for the domain regardless of how many libvirtd restarts there are doesn't it? It seems as if you're saying we need to reapply the filter on libvirtd restart.
Yes it is a matter of reapplying but bindings not filters.
(callback is called only on updates when filter with same name is already present in the list). So virNWFilterBuildAll is not called on nwfilter driver init.
And similar logic was run was before commit 3df907bfff? This direct
Yes
correlation is the part I'm missing. What follows is my understand of the before and after - some of the before is a bit of hand waving. Perhaps Daniel can chime in and "fix up" inaccuracies.
Prior to commit 3df907bfff, the virNWFilterDomainFWUpdateCB was only run when the domain was active. IOW: The domain would need to preload the bindings in "hidden" locations such that the various vnetX (or whatever target dev for the <interface>) devices would load the whichever <filterref> was assocated. When libvirtd was restarted the processing was similar and the "magic" of reinstantiation was provided through virNWFilterRegisterCallbackDriver in (for example) qemuStateInitialize. That I believe is the part you describe in your commit as "Before using filters binding filters instantiation was done by hypervisors drivers initialization code (qemu was the only such hypervisor)." - although I see LXC and UML drivers changed as well, so I could be wrong with my assumption of what you meant.
Not quite correct. virNWFilterRegisterCallbackDriver is used when filter definition is updated and we need to reinstantiate filter for every active domain that uses it. But libvirtd restart is different, in this case reinstantiation occured only in qemu driver in reconnection process, the driver of reinstantiation was hypervisor.
After that commit, rather than requiring qemuStateInitialize to register a callback driver which somehow magically loaded the filters for running guests, the nwfilter-bindings for running guests are loaded via (for example) /var/run/libvirt/vnet0.xml file processing during virNWFilterBindingObjListLoadAllConfigs (change in the previous commit 57f5621f46). So rather than the rebuild processing magically occurring in the background by some hypervisor driver performing the rebuild callback processing. Since virRegisterStateDriver (and friends) for nwfilter are run before qemu, IIUC that means the filter bindings would be loaded already. It's all a complicated dance.
Yes loaded, but not reinstatiated.
What call is being done in the normal path that isn't being done in this libvirtd restart path? Whatever the STEP_APPLY_CURRENT does? Or the
virNWFilterInstantiateFilter (STEP_APPLY_CURRENT is same but is done for all bindings)
virNWFilterInstantiateFilter from nwfilterBindingCreateXML? If the latter, then rather than using BuildAll, why not InstantiateFilter from virNWFilterBindingObjListLoadStatus?
Possible alternative. I've just followed qemu driver init code, where status are first loaded and then reconnection is done.
I keep coming back to once things are instantiated from the initial libvirtd start why is it that the libvirtd restart processing needs to do make the same call?
For the cases rules are cleaned up between libvirtd start and stop. It is easy to do - restart firewalld.
So in this after model for running guests it seems to me that the exact same processing occurs. Now if someone during libvirtd's stop period does something "outside the scope" of libvirt to change things that libvirt wouldn't otherwise be notified about, then all bets are off. Similar for other pieces of the code such as CPU's, Memory, Storage, etc.; however, for those there is a query at reinitialization time that can help reconcile differences due to perhaps missed events from qemu because libvirtd wasn't processing. Not sure there's something similar to query for nwfilter and bindings, but I assume there wouldn't have been any before either.
So how does calling this now w/ @false help things during the state initialize processing?
Before filters bindings nwfilter driver only loads filters on it's init function. Then qemu driver for example on reconnection called:
qemuProcessFiltersInstantiate virDomainConfNWFilterInstantiate nwfilterInstantiateFilter virNWFilterInstantiateFilter
and filter rules gets [re]instantiated.
From commit f14c37ce4c2
Now virNWFilterInstantiateFilter returns without actual instantiating because virNWFilterBindingLookupByPortDev finds binding which is loaded on nwfilter driver initialization> The consequences is that if somebody cleans rules between libvirtd stop and start then rules won't get instantiated again.
and this is the "key point" you are trying to reconcile, true?
Exactly
The fix is to [re]instantiate bindings in nwfilter driver init right after binding and filters are loaded. With @false argument virNWFilterBuildAll call virNWFilterInstantiateFilter for each binding - just what we need to. @true is used by virNWFilterObjListAssignDef/virNWFilterObjTestUnassignDef to use @newDef of object filter during instantiation etc.
Nikolay
Can you provided a concrete example showing your steps to help clear up things for me? Using just one filter is fine. What does the guest look like before whatever it is you do is done? What steps do you take? Then what does it look like afterwards? What would you expect? If you did the same/similar steps prior to the referenced commits what was the result?
If you mean a more concrete usecase when such a clearing of firewall tables occurs when libvirtd is stopped - I don't have one. I just restore old functionality and also motivated by Laine comment to my first patch series. Or may be I don't understand you.
Well having a use case would certainly help. It's unclear what the libvirtd restart processing isn't doing now that it may have been doing before nwfilter bindings were added. You keep saying instantiate and I keep asking what was done before that isn't being done now. Then you're throwing in a few other patches and I'm lost.
Well now we can pinpoint the commit - it is 57f5621f464 as described before. Sorry for lacking a clearer explanation. Nikolay
John
Thanx for a review.
Nikolay
As an "aside", it's been noted somewhere admins should not be messing with nwfilter bindings. If someone "cleans rules" during a period when libvirtd is stopped, then what is "expected" to happen afterwards.
Tks
John
John
diff --git a/src/nwfilter/nwfilter_driver.c b/src/nwfilter/nwfilter_driver.c index 1ee5162..1ab906f 100644 --- a/src/nwfilter/nwfilter_driver.c +++ b/src/nwfilter/nwfilter_driver.c @@ -264,6 +264,9 @@ nwfilterStateInitialize(bool privileged, if (virNWFilterBindingObjListLoadAllConfigs(driver->bindings, driver->bindingDir) < 0) goto error;
+ if (virNWFilterBuildAll(driver, false) < 0) + goto error; + nwfilterDriverUnlock();
return 0;
On 11/1/18 3:26 AM, Nikolay Shirokovskiy wrote:
On 01.11.2018 03:48, John Ferlan wrote:
On 10/31/18 10:41 AM, Nikolay Shirokovskiy wrote:
On 31.10.2018 16:14, John Ferlan wrote:
On 10/30/18 3:24 AM, Nikolay Shirokovskiy wrote:
On 29.10.2018 22:37, John Ferlan wrote:
On 10/15/18 4:26 AM, Nikolay Shirokovskiy wrote: > Before using filters binding filters instantiation was done by hypervisors > drivers initialization code (qemu was the only such hypervisor). Now qemu > reconnection done supposes it should be done by nwfilter driver probably. > Let's add this missing step. > > Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy@virtuozzo.com> > --- > src/nwfilter/nwfilter_driver.c | 3 +++ > 1 file changed, 3 insertions(+) >
If there's research you've done where the instantiation was done before introduction of the nwfilter bindings that would be really helpful...
I found that virNWFilterBuildAll was introduced in commit 3df907bfff. There were 2 callers for it:
1. virNWFilterTriggerRebuildImpl 2. nwfilterStateReload
The former called as part of the virNWFilterConfLayerInit callback during nwfilterStateInitialize (about 50 lines earlier).
First off let me say you certainly find a lot of interesting bugs/issues that are complex and that's good. Often times I wonder how you trip across things or how to quantify what you've found. Some are simpler than others. This one on the surface would seem to be simple, but I keep wondering is there a downside.
The issue is related to my recent posts:
[1] [RFC] Faster libvirtd restart with nwfilter rules https://www.redhat.com/archives/libvir-list/2018-September/msg01206.html which continues here: https://www.redhat.com/archives/libvir-list/2018-October/msg00657.html
In short if there is lots of VMs with filters then libvirtd restart takes a lot of time during which libvirtd is unresponsive. By the way the issue is found in libvirt versions 3.9.0 and ealier (don't know of newer versions, Virtuozzo is based on 3.9.0 now, just like Centos7 :) )
So many different issues - trying to focus on just the one for this particular patch.
And attempts to fix it:
[2] [PATCH RFC 0/4] nwfilter: don't reinstantiate filters if they are not changed https://www.redhat.com/archives/libvir-list/2018-October/msg00904.html
[3] [PATCH v2 0/2] nwfilter: don't reinstantiate rules if there is no need to https://www.redhat.com/archives/libvir-list/2018-October/msg01317.html
And the reason I started v2 is Laine mentioned that it is important to reinstantiate rules on restart (v1 do not care if somebody messed tables).
I've seen the patches and even read some briefly, but still need to take this particular patch as separate from those.
And I discovered that upstream version stops reinstantiating rules at all after introducing filters bindings. And this functionality is old:
So the key is "when" did that happen? That is can you pinpoint or bisect a time in history where the filters were instantiated? And by instantiated what exactly (call) are you referencing?
The below commit is the one. It adds instantiating filters on libvirtd restart. By instantiating I mean that firewall rules correspondent to filters are actually get [re]added to iptables etc.
commit cf6f8b9a9720fe5323a84e690de9fbf8ba41f6ac Author: Stefan Berger <stefanb@us.ibm.com> Date: Mon Aug 16 12:59:54 2010 -0400
nwfilter: extend nwfilter reload support
Yes, nwfilter is old, brittle, and in need of attention. Not sure anyone really wants to take on the task though! I just realized I never got the common object code implemented there. Mostly because of lock issues. Suffice to say there's more "interesting" changes in the nwfilter space being discussed internally.
The nwfilter processing is kindly said rather strange, complex, and to a degree fragile. Thus when patches come along they are met with greater scrutiny. From just reading the commit message here I don't get a sense for the problem and why the solution fixes it. So I'm left to try and research myself and ask a lot of questions.
BTW, some of the detail provided in this response is really useful as either part of a cover or after the --- in the single patch. I would think you'd "know" when you've done lots of research into a problem that providing reviews more than a mere hint would be useful! For nwfilter bindings, it's hard to imagine this is one of those - it just happened type events. There seems to be a very specific sequence that's missing from the commit description.
Right but virNWFilterTriggerRebuildImpl is not actually called, it is set as rebuild callback. This rebuild callback can be called in virNWFilterObjTestUnassignDef and virNWFilterObjListAssignDef.
Ah yes, the virNWFilterConfLayerInit sets up the context to call the virNWFilterTriggerRebuildImpl for virNWFilterObjTestUnassignDef and virNWFilterObjListAssignDef and no I see it doesn't directly call the virNWFilterBuildAll.
Still, I don't see where the processing of a rebuild callback is different than prior to commit 3df907bfff - at least with respect to the two places which would call it.
Right processing did not changed, I just wanted to show that virNWFilterBuildAll is not called now and before on nwfilter init. By the way 3df907bfff introduced virNWFilterBuildAll but not its functionality.
So prior to that commit made during v4.5.0 development, were the filters instantiated? If so, then what changed caused them to no longer be?
Yes they were.
Looks like reinstatiation was lost in
commit 57f5621f464b8df5671cbe5df6bab3cf006981dd Author: Daniel P. Berrangé <berrange@redhat.com> Date: Thu Apr 26 18:34:33 2018 +0100
nwfilter: keep track of active filter bindings
nwfilterInstantiateFilter is called from reconnection code. Before the patch we always instantiate rules, after we do not because we return early in nwfilterInstantiateFilter because binding already exist (it is loaded from status).
OK, well that's kind of the start of it, but perhaps f14c37ce4 is also to blame since that's where nwfilterInstantiateFilter is removed to be replaced by virDomainConfNWFilterInstantiate. Although I suppose it can be argued that the former should have been: if (!(obj = *FindByPortDev(...))) { ... code to get @def and @obj... } ret = virNWFilterInstantiateFilter(driver, def); ... Since calling virNWFilterInstantiateFilter during virNWFilterBindingObjListLoadStatus as I suggested below [1] isn't feasible nor does there seem to be some other means to replicate that virNWFilterInstantiateFilter called in nwfilterBindingCreateXML after adding the @def to the bindings other than via the virNWFilterBuildAll, then OK - I'm "convinced" now this is the right fix. Still probably need to adjust the commit message, how about: nwfilter: Instantiate active filter bindings during driver init Commit 57f5621f modified nwfilterInstantiateFilter to detect when a filter binding was already present before attempting to add the new binding and instantiate it. When combined with the new virNWFilterBindingObjListLoadAllConfigs logic, which searches for and loads bindings from active domains, but does not instantiate the binding as the nwfilterBindingCreateXML would do once the filter binding was added to the list of all bindings left the possibility that once the code was active the instantiation would not occur when libvirtd was restarted. Subsequent commit f14c37ce4c replaced the nwfilterInstantiateFilter with virDomainConfNWFilterInstantiate which uses @ignoreExists to detect presence of the filter and still did not restore the filter instantiation call when making the new nwfilter bindings logic active. Thus in order to instantiate any active domain filter, we will call virNWFilterBuildAll with @false to indicate the need to go through all the active bindings calling virNWFilterInstantiateFilter to instantiate the filter bindings. Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy@virtuozzo.com> ? ... Thanks for the persistence - John
The former is not called during nwfilter driver init. The latter is called as part of virNWFilterObjListLoadAllConfigs but rebuild callback is never called on this path because the list is empty
Which list? nwfilters? nwfilter-bindings?
nwfilters. And again by the way this is a bit vague statement. The matter is not list is not empty but we won't find same name in it when virNWFilterObjListAssignDef is called during driver init (which is said in below paragraph part in other words too)
If I restart libvirtd I see the same nwfilter list being generated. If I have a domain running I see the filter binding for that domain. What's missing?
The problem is not nwfilters or nwbindings are lost on restart. The problem is only with rules in iptables etc and only if somebody cleans them up between libvirtd stop and start.
Probably this branch of discussion is a bit unrelated to problem. We explore whether virNWFilterBuildAll is called on nwfilter init currently or not AFAIK. It is not, otherwise there is no need in this patch.
When a domain isn't started, it finds the nwfilter and "loads" it into nwfilter binding. That rule is applied somewhere, right? That rule remains in effect for the domain regardless of how many libvirtd restarts there are doesn't it? It seems as if you're saying we need to reapply the filter on libvirtd restart.
Yes it is a matter of reapplying but bindings not filters.
(callback is called only on updates when filter with same name is already present in the list). So virNWFilterBuildAll is not called on nwfilter driver init.
And similar logic was run was before commit 3df907bfff? This direct
Yes
correlation is the part I'm missing. What follows is my understand of the before and after - some of the before is a bit of hand waving. Perhaps Daniel can chime in and "fix up" inaccuracies.
Prior to commit 3df907bfff, the virNWFilterDomainFWUpdateCB was only run when the domain was active. IOW: The domain would need to preload the bindings in "hidden" locations such that the various vnetX (or whatever target dev for the <interface>) devices would load the whichever <filterref> was assocated. When libvirtd was restarted the processing was similar and the "magic" of reinstantiation was provided through virNWFilterRegisterCallbackDriver in (for example) qemuStateInitialize. That I believe is the part you describe in your commit as "Before using filters binding filters instantiation was done by hypervisors drivers initialization code (qemu was the only such hypervisor)." - although I see LXC and UML drivers changed as well, so I could be wrong with my assumption of what you meant.
Not quite correct. virNWFilterRegisterCallbackDriver is used when filter definition is updated and we need to reinstantiate filter for every active domain that uses it. But libvirtd restart is different, in this case reinstantiation occured only in qemu driver in reconnection process, the driver of reinstantiation was hypervisor.
After that commit, rather than requiring qemuStateInitialize to register a callback driver which somehow magically loaded the filters for running guests, the nwfilter-bindings for running guests are loaded via (for example) /var/run/libvirt/vnet0.xml file processing during virNWFilterBindingObjListLoadAllConfigs (change in the previous commit 57f5621f46). So rather than the rebuild processing magically occurring in the background by some hypervisor driver performing the rebuild callback processing. Since virRegisterStateDriver (and friends) for nwfilter are run before qemu, IIUC that means the filter bindings would be loaded already. It's all a complicated dance.
Yes loaded, but not reinstatiated.
What call is being done in the normal path that isn't being done in this libvirtd restart path? Whatever the STEP_APPLY_CURRENT does? Or the
virNWFilterInstantiateFilter (STEP_APPLY_CURRENT is same but is done for all bindings)
virNWFilterInstantiateFilter from nwfilterBindingCreateXML? If the latter, then rather than using BuildAll, why not InstantiateFilter from virNWFilterBindingObjListLoadStatus?
Possible alternative. I've just followed qemu driver init code, where status are first loaded and then reconnection is done.
^^^^^^^^^ [1]
I keep coming back to once things are instantiated from the initial libvirtd start why is it that the libvirtd restart processing needs to do make the same call?
For the cases rules are cleaned up between libvirtd start and stop. It is easy to do - restart firewalld.
So in this after model for running guests it seems to me that the exact same processing occurs. Now if someone during libvirtd's stop period does something "outside the scope" of libvirt to change things that libvirt wouldn't otherwise be notified about, then all bets are off. Similar for other pieces of the code such as CPU's, Memory, Storage, etc.; however, for those there is a query at reinitialization time that can help reconcile differences due to perhaps missed events from qemu because libvirtd wasn't processing. Not sure there's something similar to query for nwfilter and bindings, but I assume there wouldn't have been any before either.
So how does calling this now w/ @false help things during the state initialize processing?
Before filters bindings nwfilter driver only loads filters on it's init function. Then qemu driver for example on reconnection called:
qemuProcessFiltersInstantiate virDomainConfNWFilterInstantiate nwfilterInstantiateFilter virNWFilterInstantiateFilter
and filter rules gets [re]instantiated.
From commit f14c37ce4c2
Now virNWFilterInstantiateFilter returns without actual instantiating because virNWFilterBindingLookupByPortDev finds binding which is loaded on nwfilter driver initialization> The consequences is that if somebody cleans rules between libvirtd stop and start then rules won't get instantiated again.
and this is the "key point" you are trying to reconcile, true?
Exactly
The fix is to [re]instantiate bindings in nwfilter driver init right after binding and filters are loaded. With @false argument virNWFilterBuildAll call virNWFilterInstantiateFilter for each binding - just what we need to. @true is used by virNWFilterObjListAssignDef/virNWFilterObjTestUnassignDef to use @newDef of object filter during instantiation etc.
Nikolay
Can you provided a concrete example showing your steps to help clear up things for me? Using just one filter is fine. What does the guest look like before whatever it is you do is done? What steps do you take? Then what does it look like afterwards? What would you expect? If you did the same/similar steps prior to the referenced commits what was the result?
If you mean a more concrete usecase when such a clearing of firewall tables occurs when libvirtd is stopped - I don't have one. I just restore old functionality and also motivated by Laine comment to my first patch series. Or may be I don't understand you.
Well having a use case would certainly help. It's unclear what the libvirtd restart processing isn't doing now that it may have been doing before nwfilter bindings were added. You keep saying instantiate and I keep asking what was done before that isn't being done now. Then you're throwing in a few other patches and I'm lost.
Well now we can pinpoint the commit - it is 57f5621f464 as described before.
Sorry for lacking a clearer explanation.
Nikolay
John
Thanx for a review.
Nikolay
As an "aside", it's been noted somewhere admins should not be messing with nwfilter bindings. If someone "cleans rules" during a period when libvirtd is stopped, then what is "expected" to happen afterwards.
Tks
John
John
> diff --git a/src/nwfilter/nwfilter_driver.c b/src/nwfilter/nwfilter_driver.c > index 1ee5162..1ab906f 100644 > --- a/src/nwfilter/nwfilter_driver.c > +++ b/src/nwfilter/nwfilter_driver.c > @@ -264,6 +264,9 @@ nwfilterStateInitialize(bool privileged, > if (virNWFilterBindingObjListLoadAllConfigs(driver->bindings, driver->bindingDir) < 0) > goto error; > > + if (virNWFilterBuildAll(driver, false) < 0) > + goto error; > + > nwfilterDriverUnlock(); > > return 0; >
On 02.11.2018 00:50, John Ferlan wrote:
On 11/1/18 3:26 AM, Nikolay Shirokovskiy wrote:
On 01.11.2018 03:48, John Ferlan wrote:
On 10/31/18 10:41 AM, Nikolay Shirokovskiy wrote:
On 31.10.2018 16:14, John Ferlan wrote:
On 10/30/18 3:24 AM, Nikolay Shirokovskiy wrote:
On 29.10.2018 22:37, John Ferlan wrote: > > > On 10/15/18 4:26 AM, Nikolay Shirokovskiy wrote: >> Before using filters binding filters instantiation was done by hypervisors >> drivers initialization code (qemu was the only such hypervisor). Now qemu >> reconnection done supposes it should be done by nwfilter driver probably. >> Let's add this missing step. >> >> Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy@virtuozzo.com> >> --- >> src/nwfilter/nwfilter_driver.c | 3 +++ >> 1 file changed, 3 insertions(+) >> > > If there's research you've done where the instantiation was done before > introduction of the nwfilter bindings that would be really helpful... > > I found that virNWFilterBuildAll was introduced in commit 3df907bfff. > There were 2 callers for it: > > 1. virNWFilterTriggerRebuildImpl > 2. nwfilterStateReload > > The former called as part of the virNWFilterConfLayerInit callback > during nwfilterStateInitialize (about 50 lines earlier).
First off let me say you certainly find a lot of interesting bugs/issues that are complex and that's good. Often times I wonder how you trip across things or how to quantify what you've found. Some are simpler than others. This one on the surface would seem to be simple, but I keep wondering is there a downside.
The issue is related to my recent posts:
[1] [RFC] Faster libvirtd restart with nwfilter rules https://www.redhat.com/archives/libvir-list/2018-September/msg01206.html which continues here: https://www.redhat.com/archives/libvir-list/2018-October/msg00657.html
In short if there is lots of VMs with filters then libvirtd restart takes a lot of time during which libvirtd is unresponsive. By the way the issue is found in libvirt versions 3.9.0 and ealier (don't know of newer versions, Virtuozzo is based on 3.9.0 now, just like Centos7 :) )
So many different issues - trying to focus on just the one for this particular patch.
And attempts to fix it:
[2] [PATCH RFC 0/4] nwfilter: don't reinstantiate filters if they are not changed https://www.redhat.com/archives/libvir-list/2018-October/msg00904.html
[3] [PATCH v2 0/2] nwfilter: don't reinstantiate rules if there is no need to https://www.redhat.com/archives/libvir-list/2018-October/msg01317.html
And the reason I started v2 is Laine mentioned that it is important to reinstantiate rules on restart (v1 do not care if somebody messed tables).
I've seen the patches and even read some briefly, but still need to take this particular patch as separate from those.
And I discovered that upstream version stops reinstantiating rules at all after introducing filters bindings. And this functionality is old:
So the key is "when" did that happen? That is can you pinpoint or bisect a time in history where the filters were instantiated? And by instantiated what exactly (call) are you referencing?
The below commit is the one. It adds instantiating filters on libvirtd restart. By instantiating I mean that firewall rules correspondent to filters are actually get [re]added to iptables etc.
commit cf6f8b9a9720fe5323a84e690de9fbf8ba41f6ac Author: Stefan Berger <stefanb@us.ibm.com> Date: Mon Aug 16 12:59:54 2010 -0400
nwfilter: extend nwfilter reload support
Yes, nwfilter is old, brittle, and in need of attention. Not sure anyone really wants to take on the task though! I just realized I never got the common object code implemented there. Mostly because of lock issues. Suffice to say there's more "interesting" changes in the nwfilter space being discussed internally.
The nwfilter processing is kindly said rather strange, complex, and to a degree fragile. Thus when patches come along they are met with greater scrutiny. From just reading the commit message here I don't get a sense for the problem and why the solution fixes it. So I'm left to try and research myself and ask a lot of questions.
BTW, some of the detail provided in this response is really useful as either part of a cover or after the --- in the single patch. I would think you'd "know" when you've done lots of research into a problem that providing reviews more than a mere hint would be useful! For nwfilter bindings, it's hard to imagine this is one of those - it just happened type events. There seems to be a very specific sequence that's missing from the commit description.
Right but virNWFilterTriggerRebuildImpl is not actually called, it is set as rebuild callback. This rebuild callback can be called in virNWFilterObjTestUnassignDef and virNWFilterObjListAssignDef.
Ah yes, the virNWFilterConfLayerInit sets up the context to call the virNWFilterTriggerRebuildImpl for virNWFilterObjTestUnassignDef and virNWFilterObjListAssignDef and no I see it doesn't directly call the virNWFilterBuildAll.
Still, I don't see where the processing of a rebuild callback is different than prior to commit 3df907bfff - at least with respect to the two places which would call it.
Right processing did not changed, I just wanted to show that virNWFilterBuildAll is not called now and before on nwfilter init. By the way 3df907bfff introduced virNWFilterBuildAll but not its functionality.
So prior to that commit made during v4.5.0 development, were the filters instantiated? If so, then what changed caused them to no longer be?
Yes they were.
Looks like reinstatiation was lost in
commit 57f5621f464b8df5671cbe5df6bab3cf006981dd Author: Daniel P. Berrangé <berrange@redhat.com> Date: Thu Apr 26 18:34:33 2018 +0100
nwfilter: keep track of active filter bindings
nwfilterInstantiateFilter is called from reconnection code. Before the patch we always instantiate rules, after we do not because we return early in nwfilterInstantiateFilter because binding already exist (it is loaded from status).
OK, well that's kind of the start of it, but perhaps f14c37ce4 is also to blame since that's where nwfilterInstantiateFilter is removed to be replaced by virDomainConfNWFilterInstantiate. Although I suppose it can be argued that the former should have been:
if (!(obj = *FindByPortDev(...))) { ... code to get @def and @obj... }
ret = virNWFilterInstantiateFilter(driver, def); ...
Since calling virNWFilterInstantiateFilter during virNWFilterBindingObjListLoadStatus as I suggested below [1] isn't feasible nor does there seem to be some other means to replicate that virNWFilterInstantiateFilter called in nwfilterBindingCreateXML after adding the @def to the bindings other than via the virNWFilterBuildAll, then OK - I'm "convinced" now this is the right fix.
Still probably need to adjust the commit message, how about:
nwfilter: Instantiate active filter bindings during driver init
Commit 57f5621f modified nwfilterInstantiateFilter to detect when a filter binding was already present before attempting to add the new binding and instantiate it.
Ok
When combined with the new virNWFilterBindingObjListLoadAllConfigs logic, which searches for and loads bindings from active domains, but does not instantiate the binding as the nwfilterBindingCreateXML would do once the filter binding was added to the list of all bindings left the possibility that once the code was active the instantiation would not occur when libvirtd was restarted.
This is a bit hard to follow because nwfilterBindingCreateXML introduced later then nwfilterInstantiateFilter being analyzed. And the possibility reads likes there is a race. How about: As result qemu driver reconnection code on daemon restart skips binding instantiation opposite to what it was before. And this instantiation was not moved to any other place in this patch thus we got no instantiation at all.
Subsequent commit f14c37ce4c replaced the nwfilterInstantiateFilter with virDomainConfNWFilterInstantiate which uses @ignoreExists to detect presence of the filter and still did not restore the filter instantiation call when making the new nwfilter bindings logic active.
Thus in order to instantiate any active domain filter, we will call virNWFilterBuildAll with @false to indicate the need to go through all the active bindings calling virNWFilterInstantiateFilter to instantiate the filter bindings.
Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy@virtuozzo.com>
?
Everything else is fine for me. Nikolay
...
Thanks for the persistence -
John
The former is not called during nwfilter driver init. The latter is called as part of virNWFilterObjListLoadAllConfigs but rebuild callback is never called on this path because the list is empty
Which list? nwfilters? nwfilter-bindings?
nwfilters. And again by the way this is a bit vague statement. The matter is not list is not empty but we won't find same name in it when virNWFilterObjListAssignDef is called during driver init (which is said in below paragraph part in other words too)
If I restart libvirtd I see the same nwfilter list being generated. If I have a domain running I see the filter binding for that domain. What's missing?
The problem is not nwfilters or nwbindings are lost on restart. The problem is only with rules in iptables etc and only if somebody cleans them up between libvirtd stop and start.
Probably this branch of discussion is a bit unrelated to problem. We explore whether virNWFilterBuildAll is called on nwfilter init currently or not AFAIK. It is not, otherwise there is no need in this patch.
When a domain isn't started, it finds the nwfilter and "loads" it into nwfilter binding. That rule is applied somewhere, right? That rule remains in effect for the domain regardless of how many libvirtd restarts there are doesn't it? It seems as if you're saying we need to reapply the filter on libvirtd restart.
Yes it is a matter of reapplying but bindings not filters.
(callback is called only on updates when filter with same name is already present in the list). So virNWFilterBuildAll is not called on nwfilter driver init.
And similar logic was run was before commit 3df907bfff? This direct
Yes
correlation is the part I'm missing. What follows is my understand of the before and after - some of the before is a bit of hand waving. Perhaps Daniel can chime in and "fix up" inaccuracies.
Prior to commit 3df907bfff, the virNWFilterDomainFWUpdateCB was only run when the domain was active. IOW: The domain would need to preload the bindings in "hidden" locations such that the various vnetX (or whatever target dev for the <interface>) devices would load the whichever <filterref> was assocated. When libvirtd was restarted the processing was similar and the "magic" of reinstantiation was provided through virNWFilterRegisterCallbackDriver in (for example) qemuStateInitialize. That I believe is the part you describe in your commit as "Before using filters binding filters instantiation was done by hypervisors drivers initialization code (qemu was the only such hypervisor)." - although I see LXC and UML drivers changed as well, so I could be wrong with my assumption of what you meant.
Not quite correct. virNWFilterRegisterCallbackDriver is used when filter definition is updated and we need to reinstantiate filter for every active domain that uses it. But libvirtd restart is different, in this case reinstantiation occured only in qemu driver in reconnection process, the driver of reinstantiation was hypervisor.
After that commit, rather than requiring qemuStateInitialize to register a callback driver which somehow magically loaded the filters for running guests, the nwfilter-bindings for running guests are loaded via (for example) /var/run/libvirt/vnet0.xml file processing during virNWFilterBindingObjListLoadAllConfigs (change in the previous commit 57f5621f46). So rather than the rebuild processing magically occurring in the background by some hypervisor driver performing the rebuild callback processing. Since virRegisterStateDriver (and friends) for nwfilter are run before qemu, IIUC that means the filter bindings would be loaded already. It's all a complicated dance.
Yes loaded, but not reinstatiated.
What call is being done in the normal path that isn't being done in this libvirtd restart path? Whatever the STEP_APPLY_CURRENT does? Or the
virNWFilterInstantiateFilter (STEP_APPLY_CURRENT is same but is done for all bindings)
virNWFilterInstantiateFilter from nwfilterBindingCreateXML? If the latter, then rather than using BuildAll, why not InstantiateFilter from virNWFilterBindingObjListLoadStatus?
Possible alternative. I've just followed qemu driver init code, where status are first loaded and then reconnection is done.
^^^^^^^^^ [1]
I keep coming back to once things are instantiated from the initial libvirtd start why is it that the libvirtd restart processing needs to do make the same call?
For the cases rules are cleaned up between libvirtd start and stop. It is easy to do - restart firewalld.
So in this after model for running guests it seems to me that the exact same processing occurs. Now if someone during libvirtd's stop period does something "outside the scope" of libvirt to change things that libvirt wouldn't otherwise be notified about, then all bets are off. Similar for other pieces of the code such as CPU's, Memory, Storage, etc.; however, for those there is a query at reinitialization time that can help reconcile differences due to perhaps missed events from qemu because libvirtd wasn't processing. Not sure there's something similar to query for nwfilter and bindings, but I assume there wouldn't have been any before either.
> > So how does calling this now w/ @false help things during the state > initialize processing?
Before filters bindings nwfilter driver only loads filters on it's init function. Then qemu driver for example on reconnection called:
qemuProcessFiltersInstantiate virDomainConfNWFilterInstantiate nwfilterInstantiateFilter virNWFilterInstantiateFilter
and filter rules gets [re]instantiated.
From commit f14c37ce4c2
Now virNWFilterInstantiateFilter returns without actual instantiating because virNWFilterBindingLookupByPortDev finds binding which is loaded on nwfilter driver initialization> The consequences is that if somebody cleans rules between libvirtd stop and start then rules won't get instantiated again.
and this is the "key point" you are trying to reconcile, true?
Exactly
The fix is to [re]instantiate bindings in nwfilter driver init right after binding and filters are loaded. With @false argument virNWFilterBuildAll call virNWFilterInstantiateFilter for each binding - just what we need to. @true is used by virNWFilterObjListAssignDef/virNWFilterObjTestUnassignDef to use @newDef of object filter during instantiation etc.
Nikolay
Can you provided a concrete example showing your steps to help clear up things for me? Using just one filter is fine. What does the guest look like before whatever it is you do is done? What steps do you take? Then what does it look like afterwards? What would you expect? If you did the same/similar steps prior to the referenced commits what was the result?
If you mean a more concrete usecase when such a clearing of firewall tables occurs when libvirtd is stopped - I don't have one. I just restore old functionality and also motivated by Laine comment to my first patch series. Or may be I don't understand you.
Well having a use case would certainly help. It's unclear what the libvirtd restart processing isn't doing now that it may have been doing before nwfilter bindings were added. You keep saying instantiate and I keep asking what was done before that isn't being done now. Then you're throwing in a few other patches and I'm lost.
Well now we can pinpoint the commit - it is 57f5621f464 as described before.
Sorry for lacking a clearer explanation.
Nikolay
John
Thanx for a review.
Nikolay
As an "aside", it's been noted somewhere admins should not be messing with nwfilter bindings. If someone "cleans rules" during a period when libvirtd is stopped, then what is "expected" to happen afterwards.
Tks
John
> > John > >> diff --git a/src/nwfilter/nwfilter_driver.c b/src/nwfilter/nwfilter_driver.c >> index 1ee5162..1ab906f 100644 >> --- a/src/nwfilter/nwfilter_driver.c >> +++ b/src/nwfilter/nwfilter_driver.c >> @@ -264,6 +264,9 @@ nwfilterStateInitialize(bool privileged, >> if (virNWFilterBindingObjListLoadAllConfigs(driver->bindings, driver->bindingDir) < 0) >> goto error; >> >> + if (virNWFilterBuildAll(driver, false) < 0) >> + goto error; >> + >> nwfilterDriverUnlock(); >> >> return 0; >>
[...]
Looks like reinstatiation was lost in
commit 57f5621f464b8df5671cbe5df6bab3cf006981dd Author: Daniel P. Berrangé <berrange@redhat.com> Date: Thu Apr 26 18:34:33 2018 +0100
nwfilter: keep track of active filter bindings
nwfilterInstantiateFilter is called from reconnection code. Before the patch we always instantiate rules, after we do not because we return early in nwfilterInstantiateFilter because binding already exist (it is loaded from status).
OK, well that's kind of the start of it, but perhaps f14c37ce4 is also to blame since that's where nwfilterInstantiateFilter is removed to be replaced by virDomainConfNWFilterInstantiate. Although I suppose it can be argued that the former should have been:
if (!(obj = *FindByPortDev(...))) { ... code to get @def and @obj... }
ret = virNWFilterInstantiateFilter(driver, def); ...
Since calling virNWFilterInstantiateFilter during virNWFilterBindingObjListLoadStatus as I suggested below [1] isn't feasible nor does there seem to be some other means to replicate that virNWFilterInstantiateFilter called in nwfilterBindingCreateXML after adding the @def to the bindings other than via the virNWFilterBuildAll, then OK - I'm "convinced" now this is the right fix.
Still probably need to adjust the commit message, how about:
nwfilter: Instantiate active filter bindings during driver init
Commit 57f5621f modified nwfilterInstantiateFilter to detect when a filter binding was already present before attempting to add the new binding and instantiate it.
Ok
When combined with the new virNWFilterBindingObjListLoadAllConfigs logic, which searches for and loads bindings from active domains, but does not instantiate the binding as the nwfilterBindingCreateXML would do once the filter binding was added to the list of all bindings left the possibility that once the code was active the instantiation would not occur when libvirtd was restarted.
This is a bit hard to follow because nwfilterBindingCreateXML introduced later then nwfilterInstantiateFilter being analyzed. And the possibility reads likes there is a race.
Yes, this was difficult to describe and why it was "pulled out" of the first paragraph. As for "timing" or "race" - that's absolutely the key point. As of this patch though the /var/run/libvirt/nwfilter-binding/*.xml files wouldn't be created via the nwfilterBindingCreateXML API since it gets introduced a few patches later. So the net effect of this patch is I believe technically nothing beyond setting ourselves up for future failure, but this is what drove later changes, so I'm fine with blaming it. As an aside, logically in the series of changes made, this patch came after c21679fa3f to introduce virNWFilterBindingObjListLoadAllConfigs. IOW: Commit 57f5621f is only being used to set everything up without creating some huge and/or hard to follow patch.
How about:
As result qemu driver reconnection code on daemon restart skips binding instantiation opposite to what it was before. And this instantiation was not moved to any other place in this patch thus we got no instantiation at all.
However, to me this is too generic especially since qemu driver logic wasn't changed in this patch. So, consider as part of the first paragraph and replacement for the above paragraph: Additionally, the change to nwfilterStateInitialize to call virNWFilterBindingObjListLoadAllConfigs (from commit c21679fa3f) to load active domain filter bindings, but not instantiate them eventually leads to a problem for the QEMU driver reconnection logic after a daemon restart where the filter bindings would no longer be instantiated. Hopefully this explanation works. When I'm debugging problems I find it easier when there's more than a simple change occurring to have someone actually list the API names so that I don't have to guess... John FWIW: I'm still at a loss to fully understand why/how a previous instantiation and set up of the filter bindings would be "lost" on this restart path. That is, at some point in time the instantiation would send magic commands to filter packets. Just because libvirtd restarts doesn't mean those are necessarily lost, are they? IOW, wouldn't this just be redoing what was already done? Not that it's a problem because we cannot be guaranteed whether the first instantiation was done when libvirtd was stopped.
Subsequent commit f14c37ce4c replaced the nwfilterInstantiateFilter with virDomainConfNWFilterInstantiate which uses @ignoreExists to detect presence of the filter and still did not restore the filter instantiation call when making the new nwfilter bindings logic active.
Thus in order to instantiate any active domain filter, we will call virNWFilterBuildAll with @false to indicate the need to go through all the active bindings calling virNWFilterInstantiateFilter to instantiate the filter bindings.
Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy@virtuozzo.com>
?
Everything else is fine for me.
Nikolay
[...]
On 02.11.2018 16:31, John Ferlan wrote:
[...]
Looks like reinstatiation was lost in
commit 57f5621f464b8df5671cbe5df6bab3cf006981dd Author: Daniel P. Berrangé <berrange@redhat.com> Date: Thu Apr 26 18:34:33 2018 +0100
nwfilter: keep track of active filter bindings
nwfilterInstantiateFilter is called from reconnection code. Before the patch we always instantiate rules, after we do not because we return early in nwfilterInstantiateFilter because binding already exist (it is loaded from status).
OK, well that's kind of the start of it, but perhaps f14c37ce4 is also to blame since that's where nwfilterInstantiateFilter is removed to be replaced by virDomainConfNWFilterInstantiate. Although I suppose it can be argued that the former should have been:
if (!(obj = *FindByPortDev(...))) { ... code to get @def and @obj... }
ret = virNWFilterInstantiateFilter(driver, def); ...
Since calling virNWFilterInstantiateFilter during virNWFilterBindingObjListLoadStatus as I suggested below [1] isn't feasible nor does there seem to be some other means to replicate that virNWFilterInstantiateFilter called in nwfilterBindingCreateXML after adding the @def to the bindings other than via the virNWFilterBuildAll, then OK - I'm "convinced" now this is the right fix.
Still probably need to adjust the commit message, how about:
nwfilter: Instantiate active filter bindings during driver init
Commit 57f5621f modified nwfilterInstantiateFilter to detect when a filter binding was already present before attempting to add the new binding and instantiate it.
Ok
When combined with the new virNWFilterBindingObjListLoadAllConfigs logic, which searches for and loads bindings from active domains, but does not instantiate the binding as the nwfilterBindingCreateXML would do once the filter binding was added to the list of all bindings left the possibility that once the code was active the instantiation would not occur when libvirtd was restarted.
This is a bit hard to follow because nwfilterBindingCreateXML introduced later then nwfilterInstantiateFilter being analyzed. And the possibility reads likes there is a race.
Yes, this was difficult to describe and why it was "pulled out" of the first paragraph. As for "timing" or "race" - that's absolutely the key point. As of this patch though the /var/run/libvirt/nwfilter-binding/*.xml files wouldn't be created via the nwfilterBindingCreateXML API since it gets introduced a few patches later. So the net effect of this patch is I believe technically nothing beyond setting ourselves up for future failure, but this is what drove later changes, so I'm fine with blaming it.
As an aside, logically in the series of changes made, this patch came after c21679fa3f to introduce virNWFilterBindingObjListLoadAllConfigs.
IOW: Commit 57f5621f is only being used to set everything up without creating some huge and/or hard to follow patch.
How about:
As result qemu driver reconnection code on daemon restart skips binding instantiation opposite to what it was before. And this instantiation was not moved to any other place in this patch thus we got no instantiation at all.
However, to me this is too generic especially since qemu driver logic wasn't changed in this patch.
So, consider as part of the first paragraph and replacement for the above paragraph:
Additionally, the change to nwfilterStateInitialize to call virNWFilterBindingObjListLoadAllConfigs (from commit c21679fa3f) to load active domain filter bindings, but not instantiate them eventually leads to a problem for the QEMU driver reconnection logic after a daemon restart where the filter bindings would no longer be instantiated.
Ok for me
Hopefully this explanation works. When I'm debugging problems I find it easier when there's more than a simple change occurring to have someone actually list the API names so that I don't have to guess...
John
FWIW: I'm still at a loss to fully understand why/how a previous instantiation and set up of the filter bindings would be "lost" on this restart path. That is, at some point in time the instantiation would send magic commands to filter packets. Just because libvirtd restarts doesn't mean those are necessarily lost, are they? IOW, wouldn't this just be redoing what was already done? Not that it's a problem because we cannot be guaranteed whether the first instantiation was done when libvirtd was stopped.>
Subsequent commit f14c37ce4c replaced the nwfilterInstantiateFilter with virDomainConfNWFilterInstantiate which uses @ignoreExists to detect presence of the filter and still did not restore the filter instantiation call when making the new nwfilter bindings logic active.
Thus in order to instantiate any active domain filter, we will call virNWFilterBuildAll with @false to indicate the need to go through all the active bindings calling virNWFilterInstantiateFilter to instantiate the filter bindings.
Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy@virtuozzo.com>
?
Everything else is fine for me.
Nikolay
[...]
participants (2)
-
John Ferlan -
Nikolay Shirokovskiy