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weave/plugin
levaliciousandClaude Opus 5.5 305ac4f3d3
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lb: EgressService - a LoadBalancer Service's pods leave from its address
EgressService (reweave.levk.dev/v1alpha1, named after a LoadBalancer
Service of class reweave.levk.dev/node-address) makes every pod the
Service selects (by pod IP, never readiness) leave the cluster from the
Service's address, or not at all. spec.emit is explicit: Holder (the only
mode so far) tunnels members' packets to the node holding the address,
which emits them.

The holder (S1's: the one node with the address on an interface) is the
status' sole writer: host, address, and a 512-port block per node in
61000-65535 (above the default ephemeral range), stable across churn.
A member's node SNATs it to address:its-block before it leaves, so the
holder forwards it unchanged and routes replies back by port alone: ip
rules (to address, ipproto tcp/udp, dport block) ahead of the local
table, which moves from 0 to 100, since the address is local on the
holder. Members' packets travel both ways in reweave-eg, an ipip tunnel
between weave bridges (NPC drops new routed packets into weave), with
accept_local and loose rp_filter on that device only.

Members' new connections are classed at the tail of nat PREROUTING,
after kube-proxy's DNAT has ended the nat walk for Services: the pod
network, multicast and the nodes' addresses are not outside. Marked
packets follow a per-member rule to the holder's table (or to an
unreachable one), are SNATed into the tunnel, and a FORWARD guard drops
anything else a member sends outside (other protocols, other ways out).
The tunnel is accepted only from the nodes' bridges, a holder accepts
from it only the blocks' ports, and TCP MSS is clamped into it.

Fail closed throughout: until the holder has published the status,
without a block, with no single holder, or for a pod two EgressServices
select, a member's outside traffic is dropped. The CNI plugin asks
weave-npc to admit every pod (unix socket /run/weave-npc/egress.sock,
conflist "egressAdmission": true, now rewritten when it differs) after
IPAM and before the pod has an interface, so a member's first packet
already leaves from the address; no answer, no pod. weave-npc applies
nothing about egress from caches that are not synced (unless the API is
absent): a restart never strips members' rules.

reweave/test/egress/run.sh checks the design's assertions against a
live cluster; both end-to-end scripts now re-evaluate each check on
every retry (it was expanded once, before the loop).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UHXzGrsxfkGk8LmwrBbHNZ
2026-10-13 14:39:44 -04:00
..
2020-07-31 09:03:27 +00:00

Weave network driver extension for Docker and Kubernetes

This directory implements both a Docker plugin to integrate Weave Net with Docker, and a Container Network Interface (CNI) plugin, to integrate Weave Net with Kubernetes.

The Docker plugin runs automatically when you weave launch, provided your Docker daemon is version 1.9 or newer.

More detail on the Docker plugin here.

More detail on the CNI plugin here.