RE: Hyper-V networking: problem after upgrade to 10.2

[Dexuan Cui]

Thanks for the confirmation, Jac.

I might be wrong with 10.1 - it may not have the issue.
In 10.2 we made a lot of changes and I think the race condition was introduced.

To test the 2 patches, you can do something like

cd /usr/src
(supposing the 10.2 kernel code is in the sys/ sub-directory)
wget 
https://github.com/freebsd/freebsd/commit/850d0994e48b0ef68d33875e26326d44931fcf1e.patch
patch -sp1 < 850d0994e48b0ef68d33875e26326d44931fcf1e.patch
wget 
https://github.com/freebsd/freebsd/commit/1e469c559048fe6ec3641da3bb21ab87215c6506.patch
patch -sp1 < 1e469c559048fe6ec3641da3bb21ab87215c6506.patch
make buildkernel KERNCONF=GENERIC -j8
make installkernel
reboot

You may get a small issue when applying the second patch as I did:
1 out of 8 hunks failed--saving rejects to 
sys/dev/hyperv/vmbus/hv_channel_mgmt.c.rej
You can fix this by checking the .patch/.c files and manually editing the .c 
file.

Thanks,
-- Dexuan

From: Jac Backus [mailto:j.bac...@bugworks.com]
Sent: Wednesday, February 3, 2016 16:10
To: Dexuan Cui ; Sephe Qiao (Wicresoft) 
; Kylie Liang ; 
'freebsd-virtualization@freebsd.org' ; BSD 
Integration Components for Hyper-V 
Subject: RE: Hyper-V networking: problem after upgrade to 10.2

Good day Dexuan,

I think it is.
I should like to test. Are there some instructions for patching the 10.2 kernel 
source?
You mention 10.1 too, but I never had the problem with 10.1.

Thanks very for your kind help!

With kind regards,

Jac

Van: Dexuan Cui [mailto:de...@microsoft.com]
Verzonden: woensdag 3 februari 2016 1:50
Aan: Jac Backus; Sephe Qiao (Wicresoft); Kylie Liang; 
'freebsd-virtualization@freebsd.org'; BSD Integration Components for Hyper-V
Onderwerp: RE: Hyper-V networking: problem after upgrade to 10.2

Jac, really great news!

So, can I think the whole issue in your side is caused by Bug 205156?
The fix to the bug has been in the 10/stable branch and should be in the coming 
10.3.
For 10.1 and 10.2 , I'm afraid you'll have to manually apply the patches and 
build a new kernel.

BTW, the bug is actually a race condition when the netvsc driver registers 
multiple NIC devices, so sometimes we can easily repro the issue and sometimes 
we can't.

Thanks,
-- Dexuan

From: Jac Backus [mailto:j.bac...@bugworks.com]
Sent: Wednesday, February 3, 2016 2:28
To: Dexuan Cui >; Sephe Qiao 
(Wicresoft) >; Kylie 
Liang >; 
'freebsd-virtualization@freebsd.org' 
>;
 BSD Integration Components for Hyper-V 
>
Subject: RE: Hyper-V networking: problem after upgrade to 10.2

Dexuan, you are briljant!
That is the problem: Hn0 has the mac address of hn1, hn1 of hn2 and hn2 of hn0. 
So they have shifted one position to the left.

With kind regards,

Jac

Van: Dexuan Cui [mailto:de...@microsoft.com]
Verzonden: maandag 1 februari 2016 10:41
Aan: Jac Backus; Sephe Qiao (Wicresoft); Kylie Liang; 
'freebsd-virtualization@freebsd.org'; BSD Integration Components for Hyper-V
Onderwerp: RE: Hyper-V networking: problem after upgrade to 10.2

Hmm, it's really strange... what's the difference between your existing 10.1 VM 
and a fresh 10.1 VM... :(

BTW,  please check if you are seeing this bug (it looks in your side the 
network can stop working after a VM reboot):
Bug 205156 - [Hyper-V] NICs' (hn0, hn1) MAC addresses can appear in an 
uncertain way across reboot 
(https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=205156)?

Thanks,
-- Dexuan

From: Jac Backus [mailto:j.bac...@bugworks.com]
Sent: Monday, February 1, 2016 17:17
To: Dexuan Cui >; Sephe Qiao 
(Wicresoft) >; Kylie 
Liang >; 
'freebsd-virtualization@freebsd.org' 
>;
 BSD Integration Components for Hyper-V 
>
Subject: RE: Hyper-V networking: problem after upgrade to 10.2

Good day Dexuan,

I did. Unfortunately, no difference.
And at the moment the server is running on the 10.2 kernel:

uname -a
FreeBSD roadrunner.acme.inc 10.2-RELEASE-p9 FreeBSD 10.2-RELEASE-p9 #0: Thu Jan 
14 01:32:46 UTC 2016 

RE: Hyper-V networking: problem after upgrade to 10.2

[Jac Backus]

Good day Dexuan,

I think it is.
I should like to test. Are there some instructions for patching the 10.2 kernel 
source?
You mention 10.1 too, but I never had the problem with 10.1.

Thanks very for your kind help!

With kind regards,

Jac

Van: Dexuan Cui [mailto:de...@microsoft.com]
Verzonden: woensdag 3 februari 2016 1:50
Aan: Jac Backus; Sephe Qiao (Wicresoft); Kylie Liang; 
'freebsd-virtualization@freebsd.org'; BSD Integration Components for Hyper-V
Onderwerp: RE: Hyper-V networking: problem after upgrade to 10.2

Jac, really great news!

So, can I think the whole issue in your side is caused by Bug 205156?
The fix to the bug has been in the 10/stable branch and should be in the coming 
10.3.
For 10.1 and 10.2 , I'm afraid you'll have to manually apply the patches and 
build a new kernel.

BTW, the bug is actually a race condition when the netvsc driver registers 
multiple NIC devices, so sometimes we can easily repro the issue and sometimes 
we can't.

Thanks,
-- Dexuan

From: Jac Backus [mailto:j.bac...@bugworks.com]
Sent: Wednesday, February 3, 2016 2:28
To: Dexuan Cui >; Sephe Qiao 
(Wicresoft) >; Kylie 
Liang >; 
'freebsd-virtualization@freebsd.org' 
>;
 BSD Integration Components for Hyper-V 
>
Subject: RE: Hyper-V networking: problem after upgrade to 10.2

Dexuan, you are briljant!
That is the problem: Hn0 has the mac address of hn1, hn1 of hn2 and hn2 of hn0. 
So they have shifted one position to the left.

With kind regards,

Jac

Van: Dexuan Cui [mailto:de...@microsoft.com]
Verzonden: maandag 1 februari 2016 10:41
Aan: Jac Backus; Sephe Qiao (Wicresoft); Kylie Liang; 
'freebsd-virtualization@freebsd.org'; BSD Integration Components for Hyper-V
Onderwerp: RE: Hyper-V networking: problem after upgrade to 10.2

Hmm, it's really strange... what's the difference between your existing 10.1 VM 
and a fresh 10.1 VM... :(

BTW,  please check if you are seeing this bug (it looks in your side the 
network can stop working after a VM reboot):
Bug 205156 - [Hyper-V] NICs' (hn0, hn1) MAC addresses can appear in an 
uncertain way across reboot 
(https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=205156)?

Thanks,
-- Dexuan

From: Jac Backus [mailto:j.bac...@bugworks.com]
Sent: Monday, February 1, 2016 17:17
To: Dexuan Cui >; Sephe Qiao 
(Wicresoft) >; Kylie 
Liang >; 
'freebsd-virtualization@freebsd.org' 
>;
 BSD Integration Components for Hyper-V 
>
Subject: RE: Hyper-V networking: problem after upgrade to 10.2

Good day Dexuan,

I did. Unfortunately, no difference.
And at the moment the server is running on the 10.2 kernel:

uname -a
FreeBSD roadrunner.acme.inc 10.2-RELEASE-p9 FreeBSD 10.2-RELEASE-p9 #0: Thu Jan 
14 01:32:46 UTC 2016 
r...@amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC
  amd64

But there is a big chance, that after a reboot, the network is gone again.
I will see if, when it works, it keeps working. I suppose it does.

With kind regards,

Jac

Van: Dexuan Cui [mailto:de...@microsoft.com]
Verzonden: maandag 1 februari 2016 3:07
Aan: Jac Backus; Sephe Qiao (Wicresoft); Kylie Liang; 
'freebsd-virtualization@freebsd.org'; BSD Integration Components for Hyper-V
Onderwerp: RE: Hyper-V networking: problem after upgrade to 10.2

Hi Jac,
Good to know this!
It looks to me something in the VM or in the host might be causing the issue???

Can you please do another quick test: shut down the "buggy" VM and remove it in 
Hyper-V Manager (this will keep the .vhdx image) and then re-create the VM with 
the .vhdx image?

Thanks,
-- Dexuan

From: Jac Backus [mailto:j.bac...@bugworks.com]
Sent: Sunday, January 31, 2016 23:21
To: Dexuan Cui >; Sephe Qiao 
(Wicresoft) >; Kylie 
Liang >; 
'freebsd-virtualization@freebsd.org' 
>;
 BSD Integration Components for Hyper-V 
>
Subject: RE: Hyper-V networking: problem after upgrade 

[Differential] [Accepted] D5175: hyperv/hn: Add an option to always do transmission scheduling

[adrian (Adrian Chadd)]

adrian accepted this revision.
adrian added a comment.
This revision has a positive review.


  Fine by me!

REVISION DETAIL
  https://reviews.freebsd.org/D5175

EMAIL PREFERENCES
  https://reviews.freebsd.org/settings/panel/emailpreferences/

To: sepherosa_gmail.com, delphij, royger, decui_microsoft.com, 
honzhan_microsoft.com, howard0su_gmail.com, adrian, network
Cc: freebsd-virtualization-list, freebsd-net-list
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To unsubscribe, send any mail to 
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[Differential] [Accepted] D5175: hyperv/hn: Add an option to always do transmission scheduling

[honzhan_microsoft.com (hongjiangzhang)]

honzhan_microsoft.com accepted this revision.
honzhan_microsoft.com added a comment.


  Looks ok to me.

REVISION DETAIL
  https://reviews.freebsd.org/D5175

EMAIL PREFERENCES
  https://reviews.freebsd.org/settings/panel/emailpreferences/

To: sepherosa_gmail.com, delphij, royger, decui_microsoft.com, 
howard0su_gmail.com, adrian, network, honzhan_microsoft.com
Cc: freebsd-virtualization-list, freebsd-net-list
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RE: Hyper-V networking: problem after upgrade to 10.2

[Dexuan Cui]

Or, you can just use the 10/stable branch, which has included the fixes for 
this issue:

git clone 
g...@github.com:freebsd/freebsd.git
cd freebsd
git checkout -b local/stable/10 origin/stable/10
make buildkernel KERNCONF=GENERIC -j8
make installkernel
reboot

Thanks,
-- Dexuan

From: Dexuan Cui
Sent: Wednesday, February 3, 2016 17:05
To: Jac Backus ; Sephe Qiao (Wicresoft) 
; Kylie Liang ; 
'freebsd-virtualization@freebsd.org' ; BSD 
Integration Components for Hyper-V 
Subject: RE: Hyper-V networking: problem after upgrade to 10.2

Thanks for the confirmation, Jac.

I might be wrong with 10.1 - it may not have the issue.
In 10.2 we made a lot of changes and I think the race condition was introduced.

To test the 2 patches, you can do something like

cd /usr/src
(supposing the 10.2 kernel code is in the sys/ sub-directory)
wget 
https://github.com/freebsd/freebsd/commit/850d0994e48b0ef68d33875e26326d44931fcf1e.patch
patch -sp1 < 850d0994e48b0ef68d33875e26326d44931fcf1e.patch
wget 
https://github.com/freebsd/freebsd/commit/1e469c559048fe6ec3641da3bb21ab87215c6506.patch
patch -sp1 < 1e469c559048fe6ec3641da3bb21ab87215c6506.patch
make buildkernel KERNCONF=GENERIC -j8
make installkernel
reboot

You may get a small issue when applying the second patch as I did:
1 out of 8 hunks failed--saving rejects to 
sys/dev/hyperv/vmbus/hv_channel_mgmt.c.rej
You can fix this by checking the .patch/.c files and manually editing the .c 
file.

Thanks,
-- Dexuan

From: Jac Backus [mailto:j.bac...@bugworks.com]
Sent: Wednesday, February 3, 2016 16:10
To: Dexuan Cui >; Sephe Qiao 
(Wicresoft) >; Kylie 
Liang >; 
'freebsd-virtualization@freebsd.org' 
>;
 BSD Integration Components for Hyper-V 
>
Subject: RE: Hyper-V networking: problem after upgrade to 10.2

Good day Dexuan,

I think it is.
I should like to test. Are there some instructions for patching the 10.2 kernel 
source?
You mention 10.1 too, but I never had the problem with 10.1.

Thanks very for your kind help!

With kind regards,

Jac

Van: Dexuan Cui [mailto:de...@microsoft.com]
Verzonden: woensdag 3 februari 2016 1:50
Aan: Jac Backus; Sephe Qiao (Wicresoft); Kylie Liang; 
'freebsd-virtualization@freebsd.org'; BSD Integration Components for Hyper-V
Onderwerp: RE: Hyper-V networking: problem after upgrade to 10.2

Jac, really great news!

So, can I think the whole issue in your side is caused by Bug 205156?
The fix to the bug has been in the 10/stable branch and should be in the coming 
10.3.
For 10.1 and 10.2 , I'm afraid you'll have to manually apply the patches and 
build a new kernel.

BTW, the bug is actually a race condition when the netvsc driver registers 
multiple NIC devices, so sometimes we can easily repro the issue and sometimes 
we can't.

Thanks,
-- Dexuan

From: Jac Backus [mailto:j.bac...@bugworks.com]
Sent: Wednesday, February 3, 2016 2:28
To: Dexuan Cui >; Sephe Qiao 
(Wicresoft) >; Kylie 
Liang >; 
'freebsd-virtualization@freebsd.org' 
>;
 BSD Integration Components for Hyper-V 
>
Subject: RE: Hyper-V networking: problem after upgrade to 10.2

Dexuan, you are briljant!
That is the problem: Hn0 has the mac address of hn1, hn1 of hn2 and hn2 of hn0. 
So they have shifted one position to the left.

With kind regards,

Jac

Van: Dexuan Cui [mailto:de...@microsoft.com]
Verzonden: maandag 1 februari 2016 10:41
Aan: Jac Backus; Sephe Qiao (Wicresoft); Kylie Liang; 
'freebsd-virtualization@freebsd.org'; BSD Integration Components for Hyper-V
Onderwerp: RE: Hyper-V networking: problem after upgrade to 10.2

Hmm, it's really strange... what's the difference between your existing 10.1 VM 
and a fresh 10.1 VM... :(

BTW,  please check if you are seeing this bug (it looks in your side the 
network can stop working after a VM reboot):
Bug 205156 - [Hyper-V] NICs' (hn0, hn1) MAC addresses can appear in an 
uncertain way across reboot 
(https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=205156)?

Thanks,
-- Dexuan

From: Jac Backus [mailto:j.bac...@bugworks.com]
Sent: 

[Differential] [Request, 19 lines] D5175: hyperv/hn: Add an option to always do transmission scheduling

[sepherosa_gmail.com (Sepherosa Ziehau)]

sepherosa_gmail.com created this revision.
sepherosa_gmail.com added reviewers: network, adrian, delphij, royger, 
decui_microsoft.com, honzhan_microsoft.com, howard0su_gmail.com.
sepherosa_gmail.com added subscribers: freebsd-net-list, 
freebsd-virtualization-list.

REVISION SUMMARY
  It is off by default.  This eases more experiment on hn(4).

REVISION DETAIL
  https://reviews.freebsd.org/D5175

AFFECTED FILES
  sys/dev/hyperv/netvsc/hv_net_vsc.h
  sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c

CHANGE DETAILS
  diff --git a/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c 
b/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c
  --- a/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c
  +++ b/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c
  @@ -534,6 +534,10 @@
SYSCTL_ADD_INT(ctx, child, OID_AUTO, "direct_tx_size",
CTLFLAG_RW, >hn_direct_tx_size, 0,
"Size of the packet for direct transmission");
  + SYSCTL_ADD_INT(ctx, child, OID_AUTO, "sched_tx",
  + CTLFLAG_RW, >hn_sched_tx, 0,
  + "Always schedule transmission "
  + "instead of doing direct transmission");
   
if (unit == 0) {
struct sysctl_ctx_list *dc_ctx;
  @@ -1602,26 +1606,31 @@
   static void
   hn_start(struct ifnet *ifp)
   {
  - hn_softc_t *sc;
  + struct hn_softc *sc = ifp->if_softc;
  +
  + if (sc->hn_sched_tx)
  + goto do_sched;
   
  - sc = ifp->if_softc;
if (NV_TRYLOCK(sc)) {
int sched;
   
sched = hn_start_locked(ifp, sc->hn_direct_tx_size);
NV_UNLOCK(sc);
if (!sched)
return;
}
  +do_sched:
taskqueue_enqueue_fast(sc->hn_tx_taskq, >hn_start_task);
   }
   
   static void
   hn_start_txeof(struct ifnet *ifp)
   {
  - hn_softc_t *sc;
  + struct hn_softc *sc = ifp->if_softc;
  +
  + if (sc->hn_sched_tx)
  + goto do_sched;
   
  - sc = ifp->if_softc;
if (NV_TRYLOCK(sc)) {
int sched;
   
  @@ -1633,6 +1642,7 @@
>hn_start_task);
}
} else {
  +do_sched:
/*
 * Release the OACTIVE earlier, with the hope, that
 * others could catch up.  The task will clear the
  diff --git a/sys/dev/hyperv/netvsc/hv_net_vsc.h 
b/sys/dev/hyperv/netvsc/hv_net_vsc.h
  --- a/sys/dev/hyperv/netvsc/hv_net_vsc.h
  +++ b/sys/dev/hyperv/netvsc/hv_net_vsc.h
  @@ -1023,6 +1023,7 @@
int hn_txdesc_avail;
int hn_txeof;
   
  + int hn_sched_tx;
int hn_direct_tx_size;
struct taskqueue *hn_tx_taskq;
struct task hn_start_task;

EMAIL PREFERENCES
  https://reviews.freebsd.org/settings/panel/emailpreferences/

To: sepherosa_gmail.com, network, adrian, delphij, royger, decui_microsoft.com, 
honzhan_microsoft.com, howard0su_gmail.com
Cc: freebsd-virtualization-list, freebsd-net-list
diff --git a/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c b/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c
--- a/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c
+++ b/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c
@@ -534,6 +534,10 @@
 	SYSCTL_ADD_INT(ctx, child, OID_AUTO, "direct_tx_size",
 	CTLFLAG_RW, >hn_direct_tx_size, 0,
 	"Size of the packet for direct transmission");
+	SYSCTL_ADD_INT(ctx, child, OID_AUTO, "sched_tx",
+	CTLFLAG_RW, >hn_sched_tx, 0,
+	"Always schedule transmission "
+	"instead of doing direct transmission");
 
 	if (unit == 0) {
 		struct sysctl_ctx_list *dc_ctx;
@@ -1602,26 +1606,31 @@
 static void
 hn_start(struct ifnet *ifp)
 {
-	hn_softc_t *sc;
+	struct hn_softc *sc = ifp->if_softc;
+
+	if (sc->hn_sched_tx)
+		goto do_sched;
 
-	sc = ifp->if_softc;
 	if (NV_TRYLOCK(sc)) {
 		int sched;
 
 		sched = hn_start_locked(ifp, sc->hn_direct_tx_size);
 		NV_UNLOCK(sc);
 		if (!sched)
 			return;
 	}
+do_sched:
 	taskqueue_enqueue_fast(sc->hn_tx_taskq, >hn_start_task);
 }
 
 static void
 hn_start_txeof(struct ifnet *ifp)
 {
-	hn_softc_t *sc;
+	struct hn_softc *sc = ifp->if_softc;
+
+	if (sc->hn_sched_tx)
+		goto do_sched;
 
-	sc = ifp->if_softc;
 	if (NV_TRYLOCK(sc)) {
 		int sched;
 
@@ -1633,6 +1642,7 @@
 			>hn_start_task);
 		}
 	} else {
+do_sched:
 		/*
 		 * Release the OACTIVE earlier, with the hope, that
 		 * others could catch up.  The task will clear the
diff --git a/sys/dev/hyperv/netvsc/hv_net_vsc.h b/sys/dev/hyperv/netvsc/hv_net_vsc.h
--- a/sys/dev/hyperv/netvsc/hv_net_vsc.h
+++ b/sys/dev/hyperv/netvsc/hv_net_vsc.h
@@ -1023,6 +1023,7 @@
 	int		hn_txdesc_avail;
 	int		hn_txeof;
 
+	int		hn_sched_tx;
 	int		hn_direct_tx_size;
 	struct taskqueue *hn_tx_taskq;
 	struct task	hn_start_task;

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RE: Hyper-V networking: problem after upgrade to 10.2

[Jac Backus]

Hello Dexuan,

The first patch gives no messages.
When trying the second:

112 # patch -sp1 < 1e469c559048fe6ec3641da3bb21ab87215c6506.patch
1 out of 7 hunks failed--saving rejects to 
sys/dev/hyperv/vmbus/hv_channel_mgmt.c.rej

Attached you find the patched file (as a session log).

With kind regards,

Jac



Van: Dexuan Cui [mailto:de...@microsoft.com]
Verzonden: woensdag 3 februari 2016 10:05
Aan: Jac Backus; Sephe Qiao (Wicresoft); Kylie Liang; 
'freebsd-virtualization@freebsd.org'; BSD Integration Components for Hyper-V
Onderwerp: RE: Hyper-V networking: problem after upgrade to 10.2

Thanks for the confirmation, Jac.

I might be wrong with 10.1 - it may not have the issue.
In 10.2 we made a lot of changes and I think the race condition was introduced.

To test the 2 patches, you can do something like

cd /usr/src
(supposing the 10.2 kernel code is in the sys/ sub-directory)
wget 
https://github.com/freebsd/freebsd/commit/850d0994e48b0ef68d33875e26326d44931fcf1e.patch
patch -sp1 < 850d0994e48b0ef68d33875e26326d44931fcf1e.patch
wget 
https://github.com/freebsd/freebsd/commit/1e469c559048fe6ec3641da3bb21ab87215c6506.patch
patch -sp1 < 1e469c559048fe6ec3641da3bb21ab87215c6506.patch
make buildkernel KERNCONF=GENERIC -j8
make installkernel
reboot

You may get a small issue when applying the second patch as I did:
1 out of 8 hunks failed--saving rejects to 
sys/dev/hyperv/vmbus/hv_channel_mgmt.c.rej
You can fix this by checking the .patch/.c files and manually editing the .c 
file.

Thanks,
-- Dexuan

From: Jac Backus [mailto:j.bac...@bugworks.com]
Sent: Wednesday, February 3, 2016 16:10
To: Dexuan Cui >; Sephe Qiao 
(Wicresoft) >; Kylie 
Liang >; 
'freebsd-virtualization@freebsd.org' 
>;
 BSD Integration Components for Hyper-V 
>
Subject: RE: Hyper-V networking: problem after upgrade to 10.2

Good day Dexuan,

I think it is.
I should like to test. Are there some instructions for patching the 10.2 kernel 
source?
You mention 10.1 too, but I never had the problem with 10.1.

Thanks very for your kind help!

With kind regards,

Jac

Van: Dexuan Cui [mailto:de...@microsoft.com]
Verzonden: woensdag 3 februari 2016 1:50
Aan: Jac Backus; Sephe Qiao (Wicresoft); Kylie Liang; 
'freebsd-virtualization@freebsd.org'; BSD Integration Components for Hyper-V
Onderwerp: RE: Hyper-V networking: problem after upgrade to 10.2

Jac, really great news!

So, can I think the whole issue in your side is caused by Bug 205156?
The fix to the bug has been in the 10/stable branch and should be in the coming 
10.3.
For 10.1 and 10.2 , I'm afraid you'll have to manually apply the patches and 
build a new kernel.

BTW, the bug is actually a race condition when the netvsc driver registers 
multiple NIC devices, so sometimes we can easily repro the issue and sometimes 
we can't.

Thanks,
-- Dexuan

From: Jac Backus [mailto:j.bac...@bugworks.com]
Sent: Wednesday, February 3, 2016 2:28
To: Dexuan Cui >; Sephe Qiao 
(Wicresoft) >; Kylie 
Liang >; 
'freebsd-virtualization@freebsd.org' 
>;
 BSD Integration Components for Hyper-V 
>
Subject: RE: Hyper-V networking: problem after upgrade to 10.2

Dexuan, you are briljant!
That is the problem: Hn0 has the mac address of hn1, hn1 of hn2 and hn2 of hn0. 
So they have shifted one position to the left.

With kind regards,

Jac

Van: Dexuan Cui [mailto:de...@microsoft.com]
Verzonden: maandag 1 februari 2016 10:41
Aan: Jac Backus; Sephe Qiao (Wicresoft); Kylie Liang; 
'freebsd-virtualization@freebsd.org'; BSD Integration Components for Hyper-V
Onderwerp: RE: Hyper-V networking: problem after upgrade to 10.2

Hmm, it's really strange... what's the difference between your existing 10.1 VM 
and a fresh 10.1 VM... :(

BTW,  please check if you are seeing this bug (it looks in your side the 
network can stop working after a VM reboot):
Bug 205156 - [Hyper-V] NICs' (hn0, hn1) MAC addresses can appear in an 
uncertain way across reboot 
(https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=205156)?

Thanks,
-- Dexuan

From: Jac Backus [mailto:j.bac...@bugworks.com]
Sent: Monday, February 1, 2016 17:17
To: Dexuan Cui >; Sephe Qiao