doc: OpenVSwitch firewall internal design, improvements (+ newline fix)
* explain 'ingress' and 'egress' * reword a few explanations * provide table numbers as well as table names * capitalize protocol names: IP, ARP, TPC, etc. * reword explanations for tables acting as integration points with L2 other extensions * nits This change also includes a newline removal in the related portion of the code; this newline separates constants that are in fact related, and its removal had been agreed upon to be handle as a follow-up change to I60d299275effd9ef35c8007773d3c9fcabfa50fa. Change-Id: Ied215b8942bfffa1f2af2f569d0e4a110a64a364
This commit is contained in:
Thomas Morin
Thomas Morin
parent
eaff4be1c1
commit
fdaf24bead
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@ -30,10 +30,45 @@ Class ``SGPortMap`` was created to keep state consistent, and maps from ports
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to security groups and vice-versa. Every port and security group is represented
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by its own object encapsulating the necessary information.
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Note: Open vSwitch firewall driver uses register 5 for marking flow
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related to port and register 6 which defines network and is used for conntrack
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zones.
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.. note::
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Open vSwitch firewall driver uses ``register 5`` for identifying the port
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related to the flow and ``register 6`` which identifies the network, used
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in particular for conntrack zones.
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Ingress/Egress Terminology
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--------------------------
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In this document, the terms ``ingress`` and ``egress`` are relative to
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a VM instance connected to OVS (or a netns connected to OVS):
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* ``ingress`` applies to traffic that will ultimately go into a VM (or into
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a netns), assuming it is not dropped
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* ``egress`` applies to traffic coming from a VM (or from a netns)
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::
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. .
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_______|\ _______|\
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\ ingress \ \ ingress \
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/_______ / /_______ /
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|/ .-----------------. |/
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' | | '
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| |-----------( netns interface )
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( non-VM, non-netns )---| OVS |
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( interface: phy, patch ) | |------------( VM interface )
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. | | .
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/|________ '-----------------' /|________
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/ egress / / egress /
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\ ________\ \ ________\
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\| \|
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' '
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Note that these terms are used differently in OVS code and documentation, where
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they are relative to the OVS bridge, with ``ingress`` applying to traffic as
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it comes into the OVS bridge, and ``egress`` applying to traffic as it leaves
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the OVS bridge.
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Firewall API calls
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------------------
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@ -139,39 +174,39 @@ Rules example with explanation:
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-------------------------------
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The following example presents two ports on the same host. They have different
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security groups and there is icmp traffic allowed from first security group to
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security groups and there is ICMP traffic allowed from first security group to
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the second security group. Ports have following attributes:
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::
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Port 1
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- plugged to the port 1 in OVS bridge
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- ip address: 192.168.0.1
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- mac address: fa:16:3e:a4:22:10
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- security group 1: can send icmp packets out
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- IP address: 192.168.0.1
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- MAC address: fa:16:3e:a4:22:10
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- security group 1: can send ICMP packets out
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- allowed address pair: 10.0.0.1/32, fa:16:3e:8c:84:13
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Port 2
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- plugged to the port 2 in OVS bridge
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- ip address: 192.168.0.2
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- mac address: fa:16:3e:24:57:c7
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- IP address: 192.168.0.2
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- MAC address: fa:16:3e:24:57:c7
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- security group 2:
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- can receive icmp packets from security group 1
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- can receive tcp packets from security group 1
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- can receive tcp packets to port 80 from security group 2
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- can receive ip packets from security group 3
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- can receive ICMP packets from security group 1
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- can receive TCP packets from security group 1
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- can receive TCP packets to port 80 from security group 2
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- can receive IP packets from security group 3
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- allowed address pair: 10.1.0.0/24, fa:16:3e:8c:84:14
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``table 0`` contains a low priority rule to continue packets processing in
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``table 60`` aka TRANSIENT table. ``table 0`` is left for use to other
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|table_0| contains a low priority rule to continue packets processing in
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|table_60| aka TRANSIENT table. |table_0| is left for use to other
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features that take precedence over firewall, e.g. DVR. The only requirement is
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that after feature is done with its processing, it needs to pass packets for
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processing to the TRANSIENT table. This TRANSIENT table distinguishes the
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traffic to ingress or egress and loads to ``register 5`` value identifying port
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traffic.
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Egress flow is determined by switch port number and ingress flow is determined
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by destination mac address. ``register 6`` contains port tag to isolate
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connections into separate conntrack zones.
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that after such a feature is done with its processing, it needs to pass packets
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for processing to the TRANSIENT table. This TRANSIENT table distinguishes the
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ingress traffic from the egress traffic and loads into ``register 5`` a value
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identifying the port (for egress traffic based on the switch port number, and
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for ingress traffic based on the network id and destination MAC address);
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``register 6`` contains a value identifying the network (which is also the
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OVSDB port tag) to isolate connections into separate conntrack zones.
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::
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@ -183,16 +218,17 @@ connections into separate conntrack zones.
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table=60, priority=90,dl_vlan=0x284,dl_dst=fa:16:3e:8c:84:14 actions=load:0x2->NXM_NX_REG5[],load:0x284->NXM_NX_REG6[],resubmit(,81)
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table=60, priority=0 actions=NORMAL
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Following ``table 71`` implements arp spoofing protection, ip spoofing
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protection, allows traffic for obtaining ip addresses (dhcp, dhcpv6, slaac,
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ndp) for egress traffic and allows arp replies. Also identifies not tracked
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connections which are processed later with information obtained from
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The following table, |table_71| implements ARP spoofing protection, IP spoofing
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protection, allows traffic related to IP address allocations (dhcp, dhcpv6,
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slaac, ndp) for egress traffic, and allows ARP replies. Also identifies not
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tracked connections which are processed later with information obtained from
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conntrack. Notice the ``zone=NXM_NX_REG6[0..15]`` in ``actions`` when obtaining
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information from conntrack. It says every port has its own conntrack zone
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defined by value in ``register 6``. It's there to avoid accepting established
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traffic that belongs to different port with same conntrack parameters.
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defined by the value in ``register 6`` (OVSDB port tag identifying the network).
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It's there to avoid accepting established traffic that belongs to different
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port with same conntrack parameters.
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The very first rule in ``table 71`` is a rule removing conntrack information
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The very first rule in |table_71| is a rule removing conntrack information
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for a use-case where Neutron logical port is placed directly to the hypervisor.
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In such case kernel does conntrack lookup before packet reaches Open vSwitch
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bridge. Tracked packets are sent back for processing by the same table after
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@ -218,7 +254,7 @@ solicitation and neighbour advertisement.
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table=71, priority=95,icmp6,reg5=0x2,in_port=2,icmp_type=135 actions=resubmit(,94)
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table=71, priority=95,icmp6,reg5=0x2,in_port=2,icmp_type=136 actions=resubmit(,94)
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Following rules implement arp spoofing protection
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Following rules implement ARP spoofing protection
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::
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@ -241,7 +277,7 @@ instances.
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table=71, priority=70,udp,reg5=0x2,in_port=2,tp_src=67,tp_dst=68 actions=resubmit(,93)
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table=71, priority=70,udp6,reg5=0x2,in_port=2,tp_src=547,tp_dst=546 actions=resubmit(,93)
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Flowing rules obtain conntrack information for valid ip and mac address
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Flowing rules obtain conntrack information for valid IP and MAC address
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combinations. All other packets are dropped.
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::
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@ -257,14 +293,14 @@ combinations. All other packets are dropped.
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table=71, priority=0 actions=drop
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``table 72`` accepts only established or related connections, and implements
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rules defined by the security group. As this egress connection might also be an
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|table_72| accepts only established or related connections, and implements
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rules defined by security groups. As this egress connection might also be an
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ingress connection for some other port, it's not switched yet but eventually
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processed by ingress pipeline.
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processed by the ingress pipeline.
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All established or new connections defined by security group rule are
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All established or new connections defined by security group rules are
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``accepted``, which will be explained later. All invalid packets are dropped.
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In case below we allow all icmp egress traffic.
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In the case below we allow all ICMP egress traffic.
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::
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@ -273,10 +309,10 @@ In case below we allow all icmp egress traffic.
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table=72, priority=50,ct_state=+inv+trk actions=resubmit(,93)
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Important on the flows below is the ``ct_mark=0x1``. Such value have flows that
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were marked as not existing anymore by rule introduced later. Those are
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typically connections that were allowed by some security group rule and the
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rule was removed.
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Important on the flows below is the ``ct_mark=0x1``. Flows that
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were marked as not existing anymore by rule introduced later will value this
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value. Those are typically connections that were allowed by some security group
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rule and the rule was removed.
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::
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@ -293,7 +329,7 @@ allowed.
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table=72, priority=50,ct_state=-new-est+rel-inv,ct_zone=644,ct_mark=0,reg5=0x1 actions=resubmit(,94)
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table=72, priority=50,ct_state=-new-est+rel-inv,ct_zone=644,ct_mark=0,reg5=0x2 actions=resubmit(,94)
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In the following flows are marked established connections that weren't matched
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In the following, flows are marked established connections that weren't matched
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in the previous flows, which means they don't have accepting security group
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rule anymore.
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@ -305,10 +341,10 @@ rule anymore.
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table=72, priority=40,ct_state=+est,reg5=0x2 actions=ct(commit,zone=NXM_NX_REG6[0..15],exec(load:0x1->NXM_NX_CT_MARK[]))
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table=72, priority=0 actions=drop
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In following ``table 73`` are all detected ingress connections sent to ingress
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In following |table_73| are all detected ingress connections sent to ingress
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pipeline. Since the connection was already accepted by egress pipeline, all
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remaining egress connections are sent to normal flood'n'learn switching
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(table 94).
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in |table_94|.
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::
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@ -322,8 +358,8 @@ remaining egress connections are sent to normal flood'n'learn switching
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table=73, priority=80,reg5=0x2 actions=resubmit(,94)
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table=73, priority=0 actions=drop
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``table 81`` is similar to ``table 71``, allows basic ingress traffic for
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obtaining ip address and arp queries. Note that vlan tag must be removed by
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|table_81| is similar to |table_71|, allows basic ingress traffic for
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obtaining IP address and ARP queries. Note that vlan tag must be removed by
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adding ``strip_vlan`` to actions list, prior to injecting packet directly to
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port. Not tracked packets are sent to obtain conntrack information.
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@ -353,11 +389,11 @@ port. Not tracked packets are sent to obtain conntrack information.
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table=81, priority=80,ct_state=+trk,reg5=0x2 actions=resubmit(,82)
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table=81, priority=0 actions=drop
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Similarly to ``table 72``, ``table 82`` accepts established and related
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connections. In this case we allow all icmp traffic coming from
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Similarly to |table_72|, |table_82| accepts established and related
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connections. In this case we allow all ICMP traffic coming from
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``security group 1`` which is in this case only ``port 1``.
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The first four flows match on the ip addresses, and the
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next two flows match on the icmp protocol.
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The first four flows match on the IP addresses, and the
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next two flows match on the ICMP protocol.
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These six flows define conjunction flows, and the next two define actions for
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them.
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@ -404,15 +440,15 @@ the security group 2. These flows are from the following security group rules,
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::
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- can receive tcp packets from security group 1
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- can receive tcp packets to port 80 from security group 2
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- can receive TCP packets from security group 1
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- can receive TCP packets to port 80 from security group 2
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and these rules have been processed by ``merge_port_ranges`` into:
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::
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- can receive tcp packets to port != 80 from security group 1
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- can receive tcp packets to port 80 from security group 1 or 2
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- can receive TCP packets to port != 80 from security group 1
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- can receive TCP packets to port 80 from security group 1 or 2
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before translating to flows so that there is only one matching flow
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even when the TCP destination port is 80.
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@ -429,10 +465,10 @@ flows, but the corresponding security group rules have different
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remote group IDs. Unlike the above TCP example, there's no convenient
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way of expressing ``protocol != TCP`` or ``icmp_code != 1``. So the
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OVS firewall uses a different priority than the previous TCP flows so
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as not to mix up them.
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as not to mix them up.
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The mechanism for dropping connections that are not allowed anymore is the
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same as in ``table 72``.
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same as in |table_72|.
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::
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@ -449,40 +485,53 @@ same as in ``table 72``.
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table=82, priority=0 actions=drop
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Note: Conntrack zones on a single node are now based on network to which port is
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plugged in. That makes a difference between traffic on hypervisor only and
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east-west traffic. For example, if port has a VIP that was migrated to a port on
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different node, then new port won't contain conntrack information about previous
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traffic that happened with VIP.
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.. note::
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Using OpenFlow in conjunction with OVS firewall
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-----------------------------------------------
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Conntrack zones on a single node are now based on the network to which
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a port is plugged in. That makes a difference between traffic on hypervisor
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only and east-west traffic. For example, if a port has a VIP that was
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migrated to a port on a different node, then the new port won't contain
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conntrack information about previous traffic that happened with VIP.
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There are three tables where packets are sent once they get through the OVS
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firewall pipeline. The tables can be used by other mechanisms using OpenFlow
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that are supposed to work with the OVS firewall. Packets sent to ``table 91``
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are considered accepted by the egress pipeline, and will be processed so that
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they are forwarded to their destination by being submitted to a NORMAL action
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that results in Ethernet flood/learn processing. Note that ``table 91`` merely
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resubmits to ``table 94``that contains the actual NORMAL action; this allows
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to have``table 91`` be a single places where the NORMAL action can be overriden
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by other components (currently used by ``networking-bagpipe`` driver for
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``networking-bgpvpn``).
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OVS firewall integration points
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-------------------------------
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Packets sent to ``table 92`` were processed by the ingress filtering pipeline.
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As packets from the ingress filtering pipeline were injected to its
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destination, ``table 92`` receives copies of those packets and therefore
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default action is ``drop``. Finally, packets sent to ``table 93`` were filtered
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by the firewall and should be dropped. Default action is ``drop`` in this
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table.
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There are three tables where packets are sent once after going through the OVS
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firewall pipeline. The tables can be used by other mechanisms that are supposed
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to work with the OVS firewall, typically L2 agent extensions.
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In regard to the performance perspective, please note that only the first
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accepted packet of each connection session will go to ``table 91`` and
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``table 92``.
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Egress pipeline
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~~~~~~~~~~~~~~~
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Packets are sent to |table_91| and |table_94| when they are considered accepted
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by the egress pipeline, and they will be processed so that they are forwarded
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to their destination by being submitted to a NORMAL action, that results in
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Ethernet flood/learn processing.
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Two tables are used to differentiate between the first packets of a connection
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and the following packets. This was introduced for performance reasons to
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allow the logging extension to only log the first packets of a connection.
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Only the first accepted packet of each connection session will go to |table_91|
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and the following ones will go to |table_94|.
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Note that |table_91| merely resubmits to |table_94| that contains the actual
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NORMAL action; this allows to have a single place where the NORMAL action can
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be overridden by other components (currently used by ``networking-bagpipe``
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driver for ``networking-bgpvpn``).
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Ingress pipeline
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~~~~~~~~~~~~~~~~
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The first packet of each connection accepted by the ingress pipeline is sent
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to |table_92|. The default action in this table is DROP because at this point
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the packets have already been delivered to their destination port. This
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integration point is essentially provided for the logging extension.
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Packets are sent to |table_93| if processing by the ingress filtering
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concluded that they should be dropped.
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Upgrade path from iptables hybrid driver
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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----------------------------------------
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During an upgrade, the agent will need to re-plug each instance's tap device
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into the integration bridge while trying to not break existing connections. One
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@ -505,3 +554,15 @@ firewall rules and finally remove the drop rules for the instance.
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use the OVS firewall, and instances from other nodes can be live-migrated to
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it. Once the first node is evacuated, its firewall driver can be then be
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switched to the OVS driver.
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.. |table_0| replace:: ``table 0`` (LOCAL_SWITCHING)
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.. |table_60| replace:: ``table 60`` (TRANSIENT)
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.. |table_71| replace:: ``table 71`` (BASE_EGRESS)
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.. |table_72| replace:: ``table 72`` (RULES_EGRESS)
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.. |table_73| replace:: ``table 73`` (ACCEPT_OR_INGRESS)
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.. |table_81| replace:: ``table 81`` (BASE_INGRESS)
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.. |table_82| replace:: ``table 82`` (RULES_INGRESS)
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.. |table_91| replace:: ``table 91`` (ACCEPTED_EGRESS_TRAFFIC)
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.. |table_92| replace:: ``table 92`` (ACCEPTED_INGRESS_TRAFFIC)
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.. |table_93| replace:: ``table 93`` (DROPPED_TRAFFIC)
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.. |table_94| replace:: ``table 94`` (ACCEPTED_EGRESS_TRAFFIC_NORMAL)
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@ -75,7 +75,6 @@ OVS_FIREWALL_TABLES = (
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ACCEPTED_EGRESS_TRAFFIC_TABLE = 91
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ACCEPTED_INGRESS_TRAFFIC_TABLE = 92
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DROPPED_TRAFFIC_TABLE = 93
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ACCEPTED_EGRESS_TRAFFIC_NORMAL_TABLE = 94
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# --- Tunnel bridge (tun_br)
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