[ovs-dev] [patch v1 4/4] conntrack: Change established state to match kernel.
Darrell Ball
dball at vmware.com
Mon Nov 20 18:09:02 UTC 2017
On 11/20/17, 10:02 AM, "Aaron Conole" <aconole at redhat.com> wrote:
Darrell Ball <dball at vmware.com> writes:
> On 11/20/17, 9:43 AM, "Aaron Conole" <aconole at redhat.com> wrote:
>
> Darrell Ball <dball at vmware.com> writes:
>
> > On 11/20/17, 7:46 AM, "ovs-dev-bounces at openvswitch.org on behalf of
> > Aaron Conole" <ovs-dev-bounces at openvswitch.org on behalf of
> > aconole at redhat.com> wrote:
> >
> > Darrell Ball <dlu998 at gmail.com> writes:
> >
> > > Presently, the userpace connection tracker 'established' packet
> > > state diverges from the kernel and this patch brings them in line.
> > > The behavior is now that 'established' is only possible after a
> > > reply packet is seen.
> > > The previous behavior is hard to notice when rules are written to
> > > commit a connection in the trusted direction, which is recommended.
> > >
> > > A test is added to verify this.
> > >
> > > The documentation is updated to describe the new behavior of
> > > 'established' and also clarify 'new'.
> > >
> > > Signed-off-by: Darrell Ball <dlu998 at gmail.com>
> > > ---
> > > lib/conntrack-private.h | 1 +
> > > lib/conntrack.c | 21 ++++++++++++++++-----
> > > lib/meta-flow.xml | 10 +++++++---
> > > tests/system-traffic.at | 35 +++++++++++++++++++++++++++++++++++
> > > 4 files changed, 59 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/lib/conntrack-private.h b/lib/conntrack-private.h
> > > index ac0198f..1f6a107 100644
> > > --- a/lib/conntrack-private.h
> > > +++ b/lib/conntrack-private.h
> > > @@ -107,6 +107,7 @@ struct conn {
> > > uint8_t seq_skew_dir;
> > > /* True if alg data connection. */
> > > uint8_t alg_related;
> > > + uint8_t reply_seen;
> >
> > Curious - do you envision using this in the future in other areas of the
> > code? Just wondering why add it to the conn struct now.
> >
> > It is needed for this change; specifically, this check
> >> + if ((*conn)->reply_seen) {
> > The flag is added to keep context across different packets. For
> > example, a packet in
> > the forward direction needs to know that a reply packet has been seen
> > for that connection.
> >
> > I have patch to convert flags to a bitarray but that is for later and
> > there are other considerations,
> > so I deferred it.
>
> I'm still confused, though. In the code, it looks that having ctx->reply
> will be good enough to set state to established. This field is only
> set in that condition. That's why I ask. I don't understand if there's
> a plan to use this field in the future.
>
> Reply is per packet and not saved across packets.
>
See comment at the block in question.
>
> > > };
> > >
> > > enum ct_update_res {
> > > diff --git a/lib/conntrack.c b/lib/conntrack.c
> > > index dea2fed..323114a 100644
> > > --- a/lib/conntrack.c
> > > +++ b/lib/conntrack.c
> > > @@ -928,6 +928,21 @@ nat_res_exhaustion:
> > > return NULL;
> > > }
> > >
> > > +/* This function is called with the bucket lock held. */
> > > +static void
> > > +conn_handle_reply(struct dp_packet *pkt, const struct conn_lookup_ctx *ctx,
> > > + struct conn **conn)
> > > +{
> > > + if (ctx->reply) {
> > > + pkt->md.ct_state |= CS_REPLY_DIR;
> > > + (*conn)->reply_seen = true;
> > > + }
> > > + if ((*conn)->reply_seen) {
> > > + pkt->md.ct_state |= CS_ESTABLISHED;
> > > + pkt->md.ct_state &= ~CS_NEW;
> > > + }
> > > +}
This code doesn't care across packets. It simply always sets
CS_ESTABLISHED and CS_REPLY_DIR when ctx->reply is true.
Did I misunderstand something?
There are Two separate ‘if’ conditions, (
The second ‘if’ condition gets executed whether the present packet is a reply or not.
Think about it.
> > > +
> > > static bool
> > > conn_update_state(struct conntrack *ct, struct dp_packet *pkt,
> > > struct conn_lookup_ctx *ctx, struct conn **conn,
> > > @@ -950,11 +965,7 @@ conn_update_state(struct conntrack *ct, struct dp_packet *pkt,
> > >
> > > switch (res) {
> > > case CT_UPDATE_VALID:
> > > - pkt->md.ct_state |= CS_ESTABLISHED;
> > > - pkt->md.ct_state &= ~CS_NEW;
> > > - if (ctx->reply) {
> > > - pkt->md.ct_state |= CS_REPLY_DIR;
> > > - }
> > > + conn_handle_reply(pkt, ctx, conn);
> > > break;
> > > case CT_UPDATE_INVALID:
> > > pkt->md.ct_state = CS_INVALID;
> > > diff --git a/lib/meta-flow.xml b/lib/meta-flow.xml
> > > index 08ee0ec..33a2ad6 100644
> > > --- a/lib/meta-flow.xml
> > > +++ b/lib/meta-flow.xml
> > > @@ -2493,13 +2493,17 @@ actions=clone(load:0->NXM_OF_IN_PORT[],output:123)
> > > <dl>
> > > <dt><code>new</code> (0x01)</dt>
> > > <dd>
> > > - A new connection. Set to 1 if this is an uncommitted connection.
> > > + A new connection. Set to 1 if this is an uncommitted connection
> > > + or a committed connection that has not seen a reply yet.
> > > </dd>
> > >
> > > <dt><code>est</code> (0x02)</dt>
> > > <dd>
> > > - Part of an existing connection. Set to 1 if this is a committed
> > > - connection.
> > > + There are two requirements for a packet to be established, namely,
> > > + the associated connection must be committed and a reply must have
> > > + been seen. The reply packet that creates this condition will be
> > > + marked as established as well as subsequent packets in either
> > > + direction that are associated with the same conntrack entry.
> > > </dd>
> > >
> > > <dt><code>rel</code> (0x04)</dt>
> > > diff --git a/tests/system-traffic.at b/tests/system-traffic.at
> > > index fd7b612..cd55406 100644
> > > --- a/tests/system-traffic.at
> > > +++ b/tests/system-traffic.at
> > > @@ -871,6 +871,41 @@ NS_CHECK_EXEC([at_ns1], [ping -q -c 3 -i 0.3 -w 2 10.1.1.1 | FORMAT_PING], [0],
> > > OVS_TRAFFIC_VSWITCHD_STOP
> > > AT_CLEANUP
> > >
> > > +AT_SETUP([conntrack - IPv4 ping Check Est state])
> > > +CHECK_CONNTRACK()
> > > +OVS_TRAFFIC_VSWITCHD_START()
> > > +
> > > +ADD_NAMESPACES(at_ns0, at_ns1)
> > > +
> > > +ADD_VETH(p0, at_ns0, br0, "10.1.1.1/24")
> > > +ADD_VETH(p1, at_ns1, br0, "10.1.1.2/24")
> > > +
> > > +dnl Allow any traffic from ns0->ns1. Only allow nd, return traffic from ns1->ns0.
> > > +dnl Check that packet is not established before a reply.
> > > +AT_DATA([flows.txt], [dnl
> > > +priority=1,action=drop
> > > +priority=10,arp,action=normal
> > > +table=0,priority=10,in_port=2,icmp,ct_state=-trk,action=ct(table=0)
> > > +table=0,priority=10,in_port=2,icmp,ct_state=+trk+est actions=output:1
> > > +table=0,priority=10,in_port=1,icmp actions=ct(commit,table=1)
> > > +table=1,priority=10,in_port=1,icmp,ct_state=+trk+new actions=ct(table=2)
> > > +table=2,priority=10,in_port=1,icmp,ct_state=+trk+new actions=output:2
> > > +])
> > > +
> > > +AT_CHECK([ovs-ofctl --bundle add-flows br0 flows.txt])
> > > +
> > > +dnl Pings from ns0->ns1 should work fine.
> > > +NS_CHECK_EXEC([at_ns0], [ping -q -c 1 -i 0.3 -w 2 10.1.1.2 | FORMAT_PING], [0], [dnl
> > > +1 packets transmitted, 1 received, 0% packet loss, time 0ms
> > > +])
> > > +
> > > +AT_CHECK([ovs-appctl dpctl/dump-conntrack | FORMAT_CT(10.1.1.2)], [0], [dnl
> > > +icmp,orig=(src=10.1.1.1,dst=10.1.1.2,id=<cleared>,type=8,code=0),reply=(src=10.1.1.2,dst=10.1.1.1,id=<cleared>,type=0,code=0)
> > > +])
> > > +
> > > +OVS_TRAFFIC_VSWITCHD_STOP
> > > +AT_CLEANUP
> > > +
> > > AT_SETUP([conntrack - IPv6 ping])
> > > CHECK_CONNTRACK()
> > > OVS_TRAFFIC_VSWITCHD_START()
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