Re: [PATCH 1/3] ipv6: Select fragment id during UFO/GSO segmentation if not set.
On Mi, 2015-01-28 at 15:43 +0200, Michael S. Tsirkin wrote:
On Wed, Jan 28, 2015 at 11:34:02AM +0100, Hannes Frederic Sowa wrote:
Hi,
On Mi, 2015-01-28 at 11:46 +0200, Michael S. Tsirkin wrote:
On Wed, Jan 28, 2015 at 09:25:08AM +0100, Hannes Frederic Sowa wrote:
Hello,
On Di, 2015-01-27 at 18:08 +0200, Michael S. Tsirkin wrote:
On Tue, Jan 27, 2015 at 05:02:31PM +0100, Hannes Frederic Sowa wrote:
On Di, 2015-01-27 at 09:26 -0500, Vlad Yasevich wrote:
On 01/27/2015 08:47 AM, Hannes Frederic Sowa wrote:
On Di, 2015-01-27 at 10:42 +0200, Michael S. Tsirkin wrote:
On Tue, Jan 27, 2015 at 02:47:54AM +, Ben Hutchings wrote:
On Mon, 2015-01-26 at 09:37 -0500, Vladislav Yasevich wrote:
If the IPv6 fragment id has not been set and we perform
fragmentation due to UFO, select a new fragment id.
When we store the fragment id into skb_shinfo, set the bit
in the skb so we can re-use the selected id.
This preserves the behavior of UFO packets generated on the
host and solves the issue of id generation for packet sockets
and tap/macvtap devices.
This patch moves ipv6_select_ident() back in to the header
file.
It also provides the helper function that sets skb_shinfo()
fragd have to patch both kernels *in your case*.
If it's all done by host, then it's in a single place, on host.
id and sets the bit.
It also makes sure that we select the fragment id when doing
just gso validation, since it's possible for the packet to
come from an untrusted source (VM) and be forwarded through
a UFO enabled device which will expect the fragment id.
CC: Eric Dumazet eduma...@google.com
Signed-off-by: Vladislav Yasevich vyase...@redhat.com
---
include/linux/skbuff.h | 3 ++-
include/net/ipv6.h | 2 ++
net/ipv6/ip6_output.c | 4 ++--
net/ipv6/output_core.c | 9 -
net/ipv6/udp_offload.c | 10 +-
5 files changed, 23 insertions(+), 5 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 85ab7d7..3ad5203 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -605,7 +605,8 @@ struct sk_buff {
__u8ipvs_property:1;
__u8inner_protocol_type:1;
__u8remcsum_offload:1;
-/* 3 or 5 bit hole */
+__u8ufo_fragid_set:1;
[...]
Doesn't the flag belong in struct skb_shared_info, rather
than struct
sk_buff? Otherwise this looks fine.
Ben.
Hmm we seem to be out of tx flags.
Maybe ip6_frag_id == 0 should mean not set.
Maybe that is the best idea. Definitely the ufo_fragid_set bit
should
move into the skb_shared_info area.
That's what I originally wanted to do, but had to move and grow
txflags thus
skb_shinfo ended up growing. I wanted to avoid that, so stole an
skb flag.
I considered treating fragid == 0 as unset, but a 0 fragid is
perfectly valid
from the protocol perspective and could actually be generated by
the id generator
functions. This may cause us to call the id generation multiple
times.
Are there plans in the long run to let virtio_net transmit auxiliary
data to the other end so we can clean all of this this up one day?
I don't like the whole situation: looking into the virtio_net
headers
just adding a field for ipv6 fragmentation ids to those small
structs
seems bloated, not doing it feels incorrect. :/
Thoughts?
Bye,
Hannes
I'm not sure - what will be achieved by generating the IDs guest side
as
opposed to host side? It's certainly harder to get hold of entropy
guest-side.
It is not only about entropy but about uniqueness. Also fragmentation
ids should not be discoverable,
I belive predictable is the language used by the IETF draft.
so there are several aspects:
I see fragmentation id generation still as security critical:
When Eric patched the frag id generator in 04ca6973f7c1a0d (ip: make IP
identifiers less predictable) I could patch my kernels and use the
patch regardless of the machine being virtualized or not. It was not
dependent on the hypervisor.
And now it's even easier - just patch the hypervisor, and all VMs
automatically benefit.
Sometimes the hypervisor is not under my control. You would need to
patch both kernels in your case - non gso frames would still get the
fragmentation id generated in the host
Re: [PATCH 1/3] ipv6: Select fragment id during UFO/GSO segmentation if not set.
Hello,
On Di, 2015-01-27 at 18:08 +0200, Michael S. Tsirkin wrote:
On Tue, Jan 27, 2015 at 05:02:31PM +0100, Hannes Frederic Sowa wrote:
On Di, 2015-01-27 at 09:26 -0500, Vlad Yasevich wrote:
On 01/27/2015 08:47 AM, Hannes Frederic Sowa wrote:
On Di, 2015-01-27 at 10:42 +0200, Michael S. Tsirkin wrote:
On Tue, Jan 27, 2015 at 02:47:54AM +, Ben Hutchings wrote:
On Mon, 2015-01-26 at 09:37 -0500, Vladislav Yasevich wrote:
If the IPv6 fragment id has not been set and we perform
fragmentation due to UFO, select a new fragment id.
When we store the fragment id into skb_shinfo, set the bit
in the skb so we can re-use the selected id.
This preserves the behavior of UFO packets generated on the
host and solves the issue of id generation for packet sockets
and tap/macvtap devices.
This patch moves ipv6_select_ident() back in to the header file.
It also provides the helper function that sets skb_shinfo() frag
id and sets the bit.
It also makes sure that we select the fragment id when doing
just gso validation, since it's possible for the packet to
come from an untrusted source (VM) and be forwarded through
a UFO enabled device which will expect the fragment id.
CC: Eric Dumazet eduma...@google.com
Signed-off-by: Vladislav Yasevich vyase...@redhat.com
---
include/linux/skbuff.h | 3 ++-
include/net/ipv6.h | 2 ++
net/ipv6/ip6_output.c | 4 ++--
net/ipv6/output_core.c | 9 -
net/ipv6/udp_offload.c | 10 +-
5 files changed, 23 insertions(+), 5 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 85ab7d7..3ad5203 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -605,7 +605,8 @@ struct sk_buff {
__u8ipvs_property:1;
__u8inner_protocol_type:1;
__u8remcsum_offload:1;
-/* 3 or 5 bit hole */
+__u8ufo_fragid_set:1;
[...]
Doesn't the flag belong in struct skb_shared_info, rather than struct
sk_buff? Otherwise this looks fine.
Ben.
Hmm we seem to be out of tx flags.
Maybe ip6_frag_id == 0 should mean not set.
Maybe that is the best idea. Definitely the ufo_fragid_set bit should
move into the skb_shared_info area.
That's what I originally wanted to do, but had to move and grow txflags
thus
skb_shinfo ended up growing. I wanted to avoid that, so stole an skb
flag.
I considered treating fragid == 0 as unset, but a 0 fragid is perfectly
valid
from the protocol perspective and could actually be generated by the id
generator
functions. This may cause us to call the id generation multiple times.
Are there plans in the long run to let virtio_net transmit auxiliary
data to the other end so we can clean all of this this up one day?
I don't like the whole situation: looking into the virtio_net headers
just adding a field for ipv6 fragmentation ids to those small structs
seems bloated, not doing it feels incorrect. :/
Thoughts?
Bye,
Hannes
I'm not sure - what will be achieved by generating the IDs guest side as
opposed to host side? It's certainly harder to get hold of entropy
guest-side.
It is not only about entropy but about uniqueness. Also fragmentation
ids should not be discoverable, so there are several aspects:
I see fragmentation id generation still as security critical:
When Eric patched the frag id generator in 04ca6973f7c1a0d (ip: make IP
identifiers less predictable) I could patch my kernels and use the
patch regardless of the machine being virtualized or not. It was not
dependent on the hypervisor. I think that is the same reasoning why we
don't support TOE.
If we use one generator in the hypervisor in an openstack alike setting,
the host deals with quite a lot of overlay networks. A lot of default
configurations use the same addresses internally, so on the hypervisor
the frag id generators would interfere by design.
I could come up with an attack scenario for DNS servers (again :) ):
You are sitting next to a DNS server on the same hypervisor and can send
packets without source validation (because that is handled later on in
case of openvswitch when the packet is put into the corresponding
overlay network). You emit a gso packet with the same source and
destination addresses as the DNS server would do and would get an
fragmentation id which is linearly (+ time delta) incremented depending
on the source and destination address. With such a leak you could start
trying attack and spoof DNS responses (fragmentation attacks etc.).
See also details on such kind of attacks in the description of commit
04ca6973f7c1a0d.
AFAIK IETF tried with IPv6 to push fragmentation id generation to the
end hosts, that's also the reason for the introduction of atomic
fragments
Re: [PATCH 1/3] ipv6: Select fragment id during UFO/GSO segmentation if not set.
Hi,
On Mi, 2015-01-28 at 11:46 +0200, Michael S. Tsirkin wrote:
On Wed, Jan 28, 2015 at 09:25:08AM +0100, Hannes Frederic Sowa wrote:
Hello,
On Di, 2015-01-27 at 18:08 +0200, Michael S. Tsirkin wrote:
On Tue, Jan 27, 2015 at 05:02:31PM +0100, Hannes Frederic Sowa wrote:
On Di, 2015-01-27 at 09:26 -0500, Vlad Yasevich wrote:
On 01/27/2015 08:47 AM, Hannes Frederic Sowa wrote:
On Di, 2015-01-27 at 10:42 +0200, Michael S. Tsirkin wrote:
On Tue, Jan 27, 2015 at 02:47:54AM +, Ben Hutchings wrote:
On Mon, 2015-01-26 at 09:37 -0500, Vladislav Yasevich wrote:
If the IPv6 fragment id has not been set and we perform
fragmentation due to UFO, select a new fragment id.
When we store the fragment id into skb_shinfo, set the bit
in the skb so we can re-use the selected id.
This preserves the behavior of UFO packets generated on the
host and solves the issue of id generation for packet sockets
and tap/macvtap devices.
This patch moves ipv6_select_ident() back in to the header file.
It also provides the helper function that sets skb_shinfo() frag
id and sets the bit.
It also makes sure that we select the fragment id when doing
just gso validation, since it's possible for the packet to
come from an untrusted source (VM) and be forwarded through
a UFO enabled device which will expect the fragment id.
CC: Eric Dumazet eduma...@google.com
Signed-off-by: Vladislav Yasevich vyase...@redhat.com
---
include/linux/skbuff.h | 3 ++-
include/net/ipv6.h | 2 ++
net/ipv6/ip6_output.c | 4 ++--
net/ipv6/output_core.c | 9 -
net/ipv6/udp_offload.c | 10 +-
5 files changed, 23 insertions(+), 5 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 85ab7d7..3ad5203 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -605,7 +605,8 @@ struct sk_buff {
__u8ipvs_property:1;
__u8inner_protocol_type:1;
__u8remcsum_offload:1;
-/* 3 or 5 bit hole */
+__u8ufo_fragid_set:1;
[...]
Doesn't the flag belong in struct skb_shared_info, rather than
struct
sk_buff? Otherwise this looks fine.
Ben.
Hmm we seem to be out of tx flags.
Maybe ip6_frag_id == 0 should mean not set.
Maybe that is the best idea. Definitely the ufo_fragid_set bit
should
move into the skb_shared_info area.
That's what I originally wanted to do, but had to move and grow
txflags thus
skb_shinfo ended up growing. I wanted to avoid that, so stole an skb
flag.
I considered treating fragid == 0 as unset, but a 0 fragid is
perfectly valid
from the protocol perspective and could actually be generated by the
id generator
functions. This may cause us to call the id generation multiple
times.
Are there plans in the long run to let virtio_net transmit auxiliary
data to the other end so we can clean all of this this up one day?
I don't like the whole situation: looking into the virtio_net headers
just adding a field for ipv6 fragmentation ids to those small structs
seems bloated, not doing it feels incorrect. :/
Thoughts?
Bye,
Hannes
I'm not sure - what will be achieved by generating the IDs guest side as
opposed to host side? It's certainly harder to get hold of entropy
guest-side.
It is not only about entropy but about uniqueness. Also fragmentation
ids should not be discoverable,
I belive predictable is the language used by the IETF draft.
so there are several aspects:
I see fragmentation id generation still as security critical:
When Eric patched the frag id generator in 04ca6973f7c1a0d (ip: make IP
identifiers less predictable) I could patch my kernels and use the
patch regardless of the machine being virtualized or not. It was not
dependent on the hypervisor.
And now it's even easier - just patch the hypervisor, and all VMs
automatically benefit.
Sometimes the hypervisor is not under my control. You would need to
patch both kernels in your case - non gso frames would still get the
fragmentation id generated in the host kernel.
I think that is the same reasoning why we
don't support TOE.
If we use one generator in the hypervisor in an openstack alike setting,
the host deals with quite a lot of overlay networks. A lot of default
configurations use the same addresses internally, so on the hypervisor
the frag id generators would interfere by design.
I could come up with an attack scenario for DNS servers (again :) ):
You are sitting next to a DNS server on the same
Re: [PATCH 1/3] ipv6: Select fragment id during UFO/GSO segmentation if not set.
On Mi, 2015-01-28 at 18:48 +0200, Michael S. Tsirkin wrote:
On Wed, Jan 28, 2015 at 05:15:49PM +0100, Hannes Frederic Sowa wrote:
Hi,
On Mi, 2015-01-28 at 18:00 +0200, Michael S. Tsirkin wrote:
On Wed, Jan 28, 2015 at 11:34:02AM +0100, Hannes Frederic Sowa wrote:
Hi,
On Mi, 2015-01-28 at 11:46 +0200, Michael S. Tsirkin wrote:
On Wed, Jan 28, 2015 at 09:25:08AM +0100, Hannes Frederic Sowa wrote:
Hello,
On Di, 2015-01-27 at 18:08 +0200, Michael S. Tsirkin wrote:
On Tue, Jan 27, 2015 at 05:02:31PM +0100, Hannes Frederic Sowa
wrote:
On Di, 2015-01-27 at 09:26 -0500, Vlad Yasevich wrote:
On 01/27/2015 08:47 AM, Hannes Frederic Sowa wrote:
On Di, 2015-01-27 at 10:42 +0200, Michael S. Tsirkin wrote:
On Tue, Jan 27, 2015 at 02:47:54AM +, Ben Hutchings
wrote:
On Mon, 2015-01-26 at 09:37 -0500, Vladislav Yasevich
wrote:
If the IPv6 fragment id has not been set and we perform
fragmentation due to UFO, select a new fragment id.
When we store the fragment id into skb_shinfo, set the
bit
in the skb so we can re-use the selected id.
This preserves the behavior of UFO packets generated on
the
host and solves the issue of id generation for packet
sockets
and tap/macvtap devices.
This patch moves ipv6_select_ident() back in to the
header file.
It also provides the helper function that sets
skb_shinfo() frag
id and sets the bit.
It also makes sure that we select the fragment id when
doing
just gso validation, since it's possible for the packet
to
come from an untrusted source (VM) and be forwarded
through
a UFO enabled device which will expect the fragment id.
CC: Eric Dumazet eduma...@google.com
Signed-off-by: Vladislav Yasevich vyase...@redhat.com
---
include/linux/skbuff.h | 3 ++-
include/net/ipv6.h | 2 ++
net/ipv6/ip6_output.c | 4 ++--
net/ipv6/output_core.c | 9 -
net/ipv6/udp_offload.c | 10 +-
5 files changed, 23 insertions(+), 5 deletions(-)
diff --git a/include/linux/skbuff.h
b/include/linux/skbuff.h
index 85ab7d7..3ad5203 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -605,7 +605,8 @@ struct sk_buff {
__u8ipvs_property:1;
__u8inner_protocol_type:1;
__u8remcsum_offload:1;
-/* 3 or 5 bit hole */
+__u8ufo_fragid_set:1;
[...]
Doesn't the flag belong in struct skb_shared_info, rather
than struct
sk_buff? Otherwise this looks fine.
Ben.
Hmm we seem to be out of tx flags.
Maybe ip6_frag_id == 0 should mean not set.
Maybe that is the best idea. Definitely the ufo_fragid_set
bit should
move into the skb_shared_info area.
That's what I originally wanted to do, but had to move and
grow txflags thus
skb_shinfo ended up growing. I wanted to avoid that, so
stole an skb flag.
I considered treating fragid == 0 as unset, but a 0 fragid is
perfectly valid
from the protocol perspective and could actually be generated
by the id generator
functions. This may cause us to call the id generation
multiple times.
Are there plans in the long run to let virtio_net transmit
auxiliary
data to the other end so we can clean all of this this up one
day?
I don't like the whole situation: looking into the virtio_net
headers
just adding a field for ipv6 fragmentation ids to those small
structs
seems bloated, not doing it feels incorrect. :/
Thoughts?
Bye,
Hannes
I'm not sure - what will be achieved by generating the IDs guest
side as
opposed to host side? It's certainly harder to get hold of
entropy
guest-side.
It is not only about entropy but about uniqueness. Also
fragmentation
ids should not be discoverable,
I belive predictable is the language used by the IETF draft.
so there are several aspects:
I see fragmentation id generation still as security critical:
When Eric patched the frag id generator in 04ca6973f7c1a0d (ip:
make IP
identifiers less predictable) I could
Re: [PATCH 1/3] ipv6: Select fragment id during UFO/GSO segmentation if not set.
Hi,
On Mi, 2015-01-28 at 09:16 -0500, Vlad Yasevich wrote:
On 01/28/2015 05:34 AM, Hannes Frederic Sowa wrote:
Hi,
On Mi, 2015-01-28 at 11:46 +0200, Michael S. Tsirkin wrote:
On Wed, Jan 28, 2015 at 09:25:08AM +0100, Hannes Frederic Sowa wrote:
Hello,
On Di, 2015-01-27 at 18:08 +0200, Michael S. Tsirkin wrote:
On Tue, Jan 27, 2015 at 05:02:31PM +0100, Hannes Frederic Sowa wrote:
On Di, 2015-01-27 at 09:26 -0500, Vlad Yasevich wrote:
On 01/27/2015 08:47 AM, Hannes Frederic Sowa wrote:
On Di, 2015-01-27 at 10:42 +0200, Michael S. Tsirkin wrote:
On Tue, Jan 27, 2015 at 02:47:54AM +, Ben Hutchings wrote:
On Mon, 2015-01-26 at 09:37 -0500, Vladislav Yasevich wrote:
If the IPv6 fragment id has not been set and we perform
fragmentation due to UFO, select a new fragment id.
When we store the fragment id into skb_shinfo, set the bit
in the skb so we can re-use the selected id.
This preserves the behavior of UFO packets generated on the
host and solves the issue of id generation for packet sockets
and tap/macvtap devices.
This patch moves ipv6_select_ident() back in to the header file.
It also provides the helper function that sets skb_shinfo() frag
id and sets the bit.
It also makes sure that we select the fragment id when doing
just gso validation, since it's possible for the packet to
come from an untrusted source (VM) and be forwarded through
a UFO enabled device which will expect the fragment id.
CC: Eric Dumazet eduma...@google.com
Signed-off-by: Vladislav Yasevich vyase...@redhat.com
---
include/linux/skbuff.h | 3 ++-
include/net/ipv6.h | 2 ++
net/ipv6/ip6_output.c | 4 ++--
net/ipv6/output_core.c | 9 -
net/ipv6/udp_offload.c | 10 +-
5 files changed, 23 insertions(+), 5 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 85ab7d7..3ad5203 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -605,7 +605,8 @@ struct sk_buff {
__u8ipvs_property:1;
__u8inner_protocol_type:1;
__u8remcsum_offload:1;
- /* 3 or 5 bit hole */
+ __u8ufo_fragid_set:1;
[...]
Doesn't the flag belong in struct skb_shared_info, rather than
struct
sk_buff? Otherwise this looks fine.
Ben.
Hmm we seem to be out of tx flags.
Maybe ip6_frag_id == 0 should mean not set.
Maybe that is the best idea. Definitely the ufo_fragid_set bit should
move into the skb_shared_info area.
That's what I originally wanted to do, but had to move and grow
txflags thus
skb_shinfo ended up growing. I wanted to avoid that, so stole an skb
flag.
I considered treating fragid == 0 as unset, but a 0 fragid is
perfectly valid
from the protocol perspective and could actually be generated by the
id generator
functions. This may cause us to call the id generation multiple times.
Are there plans in the long run to let virtio_net transmit auxiliary
data to the other end so we can clean all of this this up one day?
I don't like the whole situation: looking into the virtio_net headers
just adding a field for ipv6 fragmentation ids to those small structs
seems bloated, not doing it feels incorrect. :/
Thoughts?
Bye,
Hannes
I'm not sure - what will be achieved by generating the IDs guest side as
opposed to host side? It's certainly harder to get hold of entropy
guest-side.
It is not only about entropy but about uniqueness. Also fragmentation
ids should not be discoverable,
I belive predictable is the language used by the IETF draft.
so there are several aspects:
I see fragmentation id generation still as security critical:
When Eric patched the frag id generator in 04ca6973f7c1a0d (ip: make IP
identifiers less predictable) I could patch my kernels and use the
patch regardless of the machine being virtualized or not. It was not
dependent on the hypervisor.
And now it's even easier - just patch the hypervisor, and all VMs
automatically benefit.
Sometimes the hypervisor is not under my control. You would need to
patch both kernels in your case - non gso frames would still get the
fragmentation id generated in the host kernel.
Why would non-gso frames need a frag id? We are talking only UDP IPv6
here, so there is no frag id generation if the packet does't need to
be fragmented.
E.g. raw sockets still can generate fragments locally. It is also a
valid setup to have multiple interfaces in one machine, one that is UFO
enabled and one that isn't. In that case, fragmentation id generation
happens on different hosts which I want to avoid.
I haven't looked closely but mismatch of MTUs on interfaces seems like
it could lead to unwanted fragmentation, e.g. see is_skb_forwardable
which is mostly always true for gso frames, so we never stop them on
bridges etc.
I think that is the same
Re: [PATCH 1/3] ipv6: Select fragment id during UFO/GSO segmentation if not set.
Hi,
On Mi, 2015-01-28 at 18:00 +0200, Michael S. Tsirkin wrote:
On Wed, Jan 28, 2015 at 11:34:02AM +0100, Hannes Frederic Sowa wrote:
Hi,
On Mi, 2015-01-28 at 11:46 +0200, Michael S. Tsirkin wrote:
On Wed, Jan 28, 2015 at 09:25:08AM +0100, Hannes Frederic Sowa wrote:
Hello,
On Di, 2015-01-27 at 18:08 +0200, Michael S. Tsirkin wrote:
On Tue, Jan 27, 2015 at 05:02:31PM +0100, Hannes Frederic Sowa wrote:
On Di, 2015-01-27 at 09:26 -0500, Vlad Yasevich wrote:
On 01/27/2015 08:47 AM, Hannes Frederic Sowa wrote:
On Di, 2015-01-27 at 10:42 +0200, Michael S. Tsirkin wrote:
On Tue, Jan 27, 2015 at 02:47:54AM +, Ben Hutchings wrote:
On Mon, 2015-01-26 at 09:37 -0500, Vladislav Yasevich wrote:
If the IPv6 fragment id has not been set and we perform
fragmentation due to UFO, select a new fragment id.
When we store the fragment id into skb_shinfo, set the bit
in the skb so we can re-use the selected id.
This preserves the behavior of UFO packets generated on the
host and solves the issue of id generation for packet sockets
and tap/macvtap devices.
This patch moves ipv6_select_ident() back in to the header
file.
It also provides the helper function that sets skb_shinfo()
frag
id and sets the bit.
It also makes sure that we select the fragment id when doing
just gso validation, since it's possible for the packet to
come from an untrusted source (VM) and be forwarded through
a UFO enabled device which will expect the fragment id.
CC: Eric Dumazet eduma...@google.com
Signed-off-by: Vladislav Yasevich vyase...@redhat.com
---
include/linux/skbuff.h | 3 ++-
include/net/ipv6.h | 2 ++
net/ipv6/ip6_output.c | 4 ++--
net/ipv6/output_core.c | 9 -
net/ipv6/udp_offload.c | 10 +-
5 files changed, 23 insertions(+), 5 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 85ab7d7..3ad5203 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -605,7 +605,8 @@ struct sk_buff {
__u8ipvs_property:1;
__u8inner_protocol_type:1;
__u8remcsum_offload:1;
-/* 3 or 5 bit hole */
+__u8ufo_fragid_set:1;
[...]
Doesn't the flag belong in struct skb_shared_info, rather
than struct
sk_buff? Otherwise this looks fine.
Ben.
Hmm we seem to be out of tx flags.
Maybe ip6_frag_id == 0 should mean not set.
Maybe that is the best idea. Definitely the ufo_fragid_set bit
should
move into the skb_shared_info area.
That's what I originally wanted to do, but had to move and grow
txflags thus
skb_shinfo ended up growing. I wanted to avoid that, so stole an
skb flag.
I considered treating fragid == 0 as unset, but a 0 fragid is
perfectly valid
from the protocol perspective and could actually be generated by
the id generator
functions. This may cause us to call the id generation multiple
times.
Are there plans in the long run to let virtio_net transmit auxiliary
data to the other end so we can clean all of this this up one day?
I don't like the whole situation: looking into the virtio_net
headers
just adding a field for ipv6 fragmentation ids to those small
structs
seems bloated, not doing it feels incorrect. :/
Thoughts?
Bye,
Hannes
I'm not sure - what will be achieved by generating the IDs guest side
as
opposed to host side? It's certainly harder to get hold of entropy
guest-side.
It is not only about entropy but about uniqueness. Also fragmentation
ids should not be discoverable,
I belive predictable is the language used by the IETF draft.
so there are several aspects:
I see fragmentation id generation still as security critical:
When Eric patched the frag id generator in 04ca6973f7c1a0d (ip: make IP
identifiers less predictable) I could patch my kernels and use the
patch regardless of the machine being virtualized or not. It was not
dependent on the hypervisor.
And now it's even easier - just patch the hypervisor, and all VMs
automatically benefit.
Sometimes the hypervisor is not under my control.
In that case doing things like extending virtio
is out of the question too, isn't it?
It needs hypervisor changes.
Sure, but I would like to have the fragmentation id generator to reside
inside the end-host kernel. Hypervisor
Re: [PATCH 1/3] ipv6: Select fragment id during UFO/GSO segmentation if not set.
On Di, 2015-01-27 at 10:42 +0200, Michael S. Tsirkin wrote:
On Tue, Jan 27, 2015 at 02:47:54AM +, Ben Hutchings wrote:
On Mon, 2015-01-26 at 09:37 -0500, Vladislav Yasevich wrote:
If the IPv6 fragment id has not been set and we perform
fragmentation due to UFO, select a new fragment id.
When we store the fragment id into skb_shinfo, set the bit
in the skb so we can re-use the selected id.
This preserves the behavior of UFO packets generated on the
host and solves the issue of id generation for packet sockets
and tap/macvtap devices.
This patch moves ipv6_select_ident() back in to the header file.
It also provides the helper function that sets skb_shinfo() frag
id and sets the bit.
It also makes sure that we select the fragment id when doing
just gso validation, since it's possible for the packet to
come from an untrusted source (VM) and be forwarded through
a UFO enabled device which will expect the fragment id.
CC: Eric Dumazet eduma...@google.com
Signed-off-by: Vladislav Yasevich vyase...@redhat.com
---
include/linux/skbuff.h | 3 ++-
include/net/ipv6.h | 2 ++
net/ipv6/ip6_output.c | 4 ++--
net/ipv6/output_core.c | 9 -
net/ipv6/udp_offload.c | 10 +-
5 files changed, 23 insertions(+), 5 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 85ab7d7..3ad5203 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -605,7 +605,8 @@ struct sk_buff {
__u8ipvs_property:1;
__u8inner_protocol_type:1;
__u8remcsum_offload:1;
- /* 3 or 5 bit hole */
+ __u8ufo_fragid_set:1;
[...]
Doesn't the flag belong in struct skb_shared_info, rather than struct
sk_buff? Otherwise this looks fine.
Ben.
Hmm we seem to be out of tx flags.
Maybe ip6_frag_id == 0 should mean not set.
Maybe that is the best idea. Definitely the ufo_fragid_set bit should
move into the skb_shared_info area.
Thanks,
Hannes
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Re: [PATCH 1/3] ipv6: Select fragment id during UFO/GSO segmentation if not set.
On Di, 2015-01-27 at 09:26 -0500, Vlad Yasevich wrote:
On 01/27/2015 08:47 AM, Hannes Frederic Sowa wrote:
On Di, 2015-01-27 at 10:42 +0200, Michael S. Tsirkin wrote:
On Tue, Jan 27, 2015 at 02:47:54AM +, Ben Hutchings wrote:
On Mon, 2015-01-26 at 09:37 -0500, Vladislav Yasevich wrote:
If the IPv6 fragment id has not been set and we perform
fragmentation due to UFO, select a new fragment id.
When we store the fragment id into skb_shinfo, set the bit
in the skb so we can re-use the selected id.
This preserves the behavior of UFO packets generated on the
host and solves the issue of id generation for packet sockets
and tap/macvtap devices.
This patch moves ipv6_select_ident() back in to the header file.
It also provides the helper function that sets skb_shinfo() frag
id and sets the bit.
It also makes sure that we select the fragment id when doing
just gso validation, since it's possible for the packet to
come from an untrusted source (VM) and be forwarded through
a UFO enabled device which will expect the fragment id.
CC: Eric Dumazet eduma...@google.com
Signed-off-by: Vladislav Yasevich vyase...@redhat.com
---
include/linux/skbuff.h | 3 ++-
include/net/ipv6.h | 2 ++
net/ipv6/ip6_output.c | 4 ++--
net/ipv6/output_core.c | 9 -
net/ipv6/udp_offload.c | 10 +-
5 files changed, 23 insertions(+), 5 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 85ab7d7..3ad5203 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -605,7 +605,8 @@ struct sk_buff {
__u8ipvs_property:1;
__u8inner_protocol_type:1;
__u8remcsum_offload:1;
-/* 3 or 5 bit hole */
+__u8ufo_fragid_set:1;
[...]
Doesn't the flag belong in struct skb_shared_info, rather than struct
sk_buff? Otherwise this looks fine.
Ben.
Hmm we seem to be out of tx flags.
Maybe ip6_frag_id == 0 should mean not set.
Maybe that is the best idea. Definitely the ufo_fragid_set bit should
move into the skb_shared_info area.
That's what I originally wanted to do, but had to move and grow txflags thus
skb_shinfo ended up growing. I wanted to avoid that, so stole an skb flag.
I considered treating fragid == 0 as unset, but a 0 fragid is perfectly valid
from the protocol perspective and could actually be generated by the id
generator
functions. This may cause us to call the id generation multiple times.
Are there plans in the long run to let virtio_net transmit auxiliary
data to the other end so we can clean all of this this up one day?
I don't like the whole situation: looking into the virtio_net headers
just adding a field for ipv6 fragmentation ids to those small structs
seems bloated, not doing it feels incorrect. :/
Thoughts?
Bye,
Hannes
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Re: IPv6 UFO for VMs
On Mi, 2014-10-22 at 00:44 +0100, Ben Hutchings wrote: There are several ways that VMs can take advantage of UFO and get the host to do fragmentation for them: drivers/net/macvtap.c: gso_type = SKB_GSO_UDP; drivers/net/tun.c: skb_shinfo(skb)-gso_type = SKB_GSO_UDP; drivers/net/virtio_net.c: skb_shinfo(skb)-gso_type = SKB_GSO_UDP; Our implementation of UFO for IPv6 does: fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen); fptr-nexthdr = nexthdr; fptr-reserved = 0; fptr-identification = skb_shinfo(skb)-ip6_frag_id; which assumes ip6_frag_id has been set. That's only true if the local stack constructed the skb; otherwise it appears we get zero. This seems to be a regression as a result of: commit 916e4cf46d0204806c062c8c6c4d1f633852c5b6 Author: Hannes Frederic Sowa han...@stressinduktion.org Date: Fri Feb 21 02:55:35 2014 +0100 ipv6: reuse ip6_frag_id from ip6_ufo_append_data However, that change seems reasonable - we *shouldn't* be choosing IDs for any other stack. Any paravirt net driver that can use IPv6 UFO needs to have some way of passing a fragmentation ID to put in skb_shared_info::ip6_frag_id. Do we really gain a lot of performance by enabling UFO on those devices or would it make sense to just drop support? It only helps fragmenting large UDP packets, so I don't think it is worth it. Otherwise I agree with Ben, we need to pass a fragmentation id from the host over to the system segmenting the gso frame. Fragmentation ids must be generated by the end system. Hmm... Bye, Hannes ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
