First check whether the chain exists with the required rules, and
if not - create it.
If we flush each time we start weave-npc then we create a (short)
time window during which all egress traffic is allowed.
The following rules are provisioned by weave-npc:
-A WEAVE-NPC-EGRESS -m state --state RELATED,ESTABLISHED -j RETURN
-A WEAVE-NPC-EGRESS -m set ! --match-set weave-local-pods src -j RETURN
-A WEAVE-NPC-EGRESS -d 224.0.0.0/4 -j RETURN
-A WEAVE-NPC-EGRESS -m state --state NEW -j WEAVE-NPC-EGRESS-DEFAULT
-A WEAVE-NPC-EGRESS -m state --state NEW -m mark ! --mark 0x40000/0x40000 -j WEAVE-NPC-EGRESS-CUSTOM
-A WEAVE-NPC-EGRESS -m state --state NEW -m mark ! --mark 0x40000/0x40000 -j NFLOG --nflog-group 86
-A WEAVE-NPC-EGRESS -m mark ! --mark 0x40000/0x40000 -j DROP
-A WEAVE-NPC-EGRESS-CUSTOM <rulespec> -j MARK --set-xmark 0x40000/0x40000
-A WEAVE-NPC-EGRESS-CUSTOM <rulespec> -j RETURN
-A WEAVE-NPC-EGRESS-DEFAULT <rulespec> -j MARK --set-xmark 0x40000/0x40000
-A WEAVE-NPC-EGRESS-DEFAULT <rulespec> -j RETURN
For each rule we create two (mark and return). We cannot just accept
a packet if it matches any rule, as a packet might need to traverse
the ingress npc as well which happens later in the chain (in some cases
we cannot detect whether packet is ingress or egress, so we need to
check both chains).
- Track only local changes.
- Add comment to the iptables rule which prevents SNAT'ing.
- Rename the ipset to weaver-no-masq-local to prevent NPC from destroying it.
- Fix comment about create/flush WEAVE-EXPOSE.
- Add comment about reexpose being no-op if bridge hasn't been exposed.
- Add comment that the feature is not only for Kubernetes.
- Reuse the ipset instance.
The main difference between new and legacy (pre-1.7) netpol semantics
are the following:
* The DenyDefault ingress isolation annotation is obsoleted.
* Traffic is allowed to a pod if there are no netpol selecting
the pod.
See https://kubernetes.io/docs/api-reference/v1.6/#networkpolicyspec-v1beta1-extensions
vs https://kubernetes.io/docs/api-reference/v1.7/#networkpolicyspec-v1-networking
for more details.
weave-npc can operate either in the legacy or the new mode (default). To
use the legacy, pass "--use-legacy-netpol" arg when starting the npc.
In non-legacy mode we create for each Namespace a default-allow ipset
which stores IP addrs of such Pods which are not selected by any
NetworkPolicy.The ipsets are dst's in rules of the WEAVE-NPC-DEFAULT chain.
It's sad because this changes a regular pattern into an irregular one,
which will create spurious diffs if more work is added at the end of
the function. Still, this is easier than fixing the lint runner to
ignore the report.
If it's destined for a pod on another node it will be checked again
when it reaches that other node. The previous version was rejecting
traffic coming in from outside the cluster.
Martynas Pumputis