[ovs-dev] [patch v1 4/4] conntrack: Change established state to match kernel.

Aaron Conole aconole at redhat.com
Mon Nov 20 17:43:15 UTC 2017


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.

>     >  };
>     >  
>     >  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;
>     > +    }
>     > +}
>     > +
>     >  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()
>     _______________________________________________
>     dev mailing list
>     dev at openvswitch.org
>     https://urldefense.proofpoint.com/v2/url?u=https-3A__mail.openvswitch.org_mailman_listinfo_ovs-2Ddev&d=DwICAg&c=uilaK90D4TOVoH58JNXRgQ&r=BVhFA09CGX7JQ5Ih-uZnsw&m=87H5HK6RLf5U06uQVBVU0PtlxYH_raGxgr49EgY0iZY&s=1bVHxIV3LB7P0GL5vtjPjaUgbYy31jQ2M5zPZxZQSZI&e=
>     


More information about the dev mailing list