flannel CNI plugin v1.9.1-flannel3 build recipe

github.com/flannel-io/cni-plugin (v1.9.1-flannel3) at b380f201008e9bed159703846cf10d3c50b4f9ce

Fetched once, with the network on, by the vendor step (Dockerfile.vendor) when the kit was made; the offline build uses the kit's vendored copies:

• git https://github.com/flannel-io/cni-plugin v1.9.1-flannel3
• https://github.com/canonical/chisel/releases/download/v1.5.1/chisel_v1.5.1_linux_amd64.tar.gz
• https://github.com/canonical/chisel-releases/archive/f2600d3aa90123db6d44bb1441a99afc8b5847d9.tar.gz

• Base imagegolang:1.26.10-bookworm@sha256:632dff7351799a5a9954a48dc06670ade72ee44e8c351cdc0e5a57af2fea21af
• Base imageubuntu:24.04@sha256:fe81560990fae86dc4743202b2cb4d3df98d0bcf949173cecef15ce1127ef852
• BuildKitmoby/buildkit:v0.31.2
  sha256:e0e67ea9c4bb07bdef683e29f70f3b623d1eb9c82274a9ec04e6bb0511449fb0
• Build methodsource-rebuild-go
• SOURCE_DATE_EPOCH1786091006 (2026-08-07T08:23:26Z)
• Target digest (linux/amd64)sha256:4511acd7413d1e6fd78d3d712921d794cb820a3b62973512532d7b64f2cc4e8a
• Target config digestsha256:72281e62a4fb98749aaac8f4525d44d61b32494f4ae1a51a9547a479fcc124d9
• Checksummed kit files1,657 (CHECKSUMS.sha256)

# GENERATED L-009 hermetic build (--network=none, SBOM+SLSA-attestation-producing).
# Pinned bases from BASE_IMAGE_DIGESTS.lock; vendored Go tree + debs from Dockerfile.vendor.
FROM golang:1.26.10-bookworm@sha256:632dff7351799a5a9954a48dc06670ade72ee44e8c351cdc0e5a57af2fea21af AS build_flannel
WORKDIR /src
COPY vendored/flannelcniplugin-src/ .
ENV CGO_ENABLED=1 GOTOOLCHAIN=local GOWORK=off GOFLAGS="-mod=vendor -buildvcs=false" GOPROXY=off SOURCE_DATE_EPOCH=1786091006
RUN go build -trimpath -tags "netgo osusergo no_stage static_build" -ldflags='-extldflags -static -w -X main.Version=v1.9.1 -X main.Commit=b380f201 -X main.Program=flannel' -o /flannel . && /flannel version > /tmp/flannel.version 2>&1; cat /tmp/flannel.version; grep -qF 'CNI Plugin flannel version v1.9.1' /tmp/flannel.version || { echo 'flannel version does not report CNI Plugin flannel version v1.9.1'; exit 1; } && \
    { readelf -lW /flannel | sed -n 's/.*Requesting program interpreter: \(.*\)]$/\1/p'; readelf -dW /flannel | sed -n 's/.*Shared library: \[\(.*\)\]$/\1/p'; } > /flannel.needs
# rs-probe: the HEALTHCHECK helper (standard library only, from the kit's rs-probe.go)
FROM golang:1.26.10-bookworm@sha256:632dff7351799a5a9954a48dc06670ade72ee44e8c351cdc0e5a57af2fea21af AS build_rs_probe
WORKDIR /probe
COPY rs-probe.go main.go
COPY rs-probe.mod go.mod
ENV CGO_ENABLED=0 GOTOOLCHAIN=local GOFLAGS="-buildvcs=false" GOPROXY=off SOURCE_DATE_EPOCH=1786091006
RUN go build -trimpath -ldflags='-s -w' -o /rs-probe .
# the chiselled rootfs (vendored/chisel, cut by Dockerfile.vendor), the service user, the binaries
FROM ubuntu:24.04@sha256:fe81560990fae86dc4743202b2cb4d3df98d0bcf949173cecef15ce1127ef852 AS rootfs
ARG SOURCE_DATE_EPOCH=1786091006
ADD vendored/chisel/rootfs.tar /rootfs/
RUN printf 'flannelcniplugin:x:999:999::/var/lib/flannelcniplugin:/bin/sh\n' >> /rootfs/etc/passwd && printf 'flannelcniplugin:x:999:\n' >> /rootfs/etc/group && \
    mkdir -p /rootfs/var/lib/flannelcniplugin && chown -R 999:999 /rootfs/var/lib/flannelcniplugin
COPY --from=build_flannel /flannel /rootfs/flannel
COPY --from=build_flannel /flannel.needs /tmp/needs/flannel
COPY --from=build_rs_probe /rs-probe /rootfs/usr/local/bin/rs-probe

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#!/usr/bin/env bash
# =============================================================================
# ReadyStack — offline reproducible rebuild.
#
# Rebuilds this product's image from THIS ARCHIVE ALONE, with no network access
# of any kind, and prints the resulting linux/amd64 image-manifest digest.
# Run ./VERIFY_OFFLINE.sh afterwards to assert it equals the published digest.
#
# Requirements: linux/amd64 Docker host, docker buildx >= 0.30, jq, tar.
# No git, no registry access, no additional tooling.
#
#   ./BUILD_OFFLINE.sh                the rebuild (OCI image + a docker-loadable copy)
#   ./BUILD_OFFLINE.sh --provenance   the same rebuild with SLSA v1 build provenance (mode=max) attached to the OCI
#                                     image, generated by BuildKit, not by any build step. Run on your own hardened,
#                                     isolated build platform and sign that provenance with a key the build cannot
#                                     reach, and the result meets SLSA Build Level 3 (see REBUILD.md). The image
#                                     digest is the same either way.
# =============================================================================
set -euo pipefail
PROVENANCE=0
for arg in "$@"; do
  case "$arg" in
    --provenance) PROVENANCE=1 ;;
    -h|--help) sed -n '2,20p' "$0"; exit 0 ;;

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