Otherwise, the same ipBlock ipset can be used among different namespaces which
results in panic as refcounting of ipsets happens only per namespace, so
npc will try to create the same ipset twice.
Egress does not work in the legacy netpol mode, so in the legacy case
we don't have to create the egress traffic steering rules. Otherwise,
some traffic will be blocked.
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.
We need two rules:
* `-A INPUT -i weave -j WEAVE-NPC-EGRESS`: applies to packets destined
to a local node.
* `-A FORWARD -i weave -j WEAVE-NPC-EGRESS`: the rest. It can match
an ingress packet.
dstSelector becomes ambiguous once we introduce the egress.
So, from now on, we call selector a target selector if it selects
pods to which a netpol applies (aka NetworkPolicySpec.podSelector).
This ensures two rules with the same rulespec but of different
policyType will end up having different keys.
Sharing the same key would prevent from provisioning the rules.
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).
Martynas Pumputis