feat(orchestrator): slice 13c(ii) — shared-gateway source-IP allocator

Deterministic per-bottle address assignment on the consolidated docker
gateway's shared network — the address the gateway uses as its attribution
key. Pure ipaddress logic; the docker-specific inputs (subnet CIDR, the
gateway container's own address) are gathered by the caller and passed as
`taken`, keeping it testable without docker.

- next_free_ip(cidr, taken): lowest host address not reserved (network +
  broadcast excluded by hosts(); docker's router .1 excluded here) and not
  already assigned (gateway container + live bottles from the registry).
  NoFreeAddressError when the subnet is exhausted.

pyright 0 errors; pylint 9.83/10; unit suite green (the 13 test_sidecar_init
/bin/sleep errors are pre-existing NixOS-local noise).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WBMWTEtQdJ4W5UrWuLHCck

bot_bottle/backend/docker/gateway_net.py

@@ -0,0 +1,47 @@
+"""Shared-gateway source-IP allocation for the consolidated docker backend
+(PRD 0070).
+
+In the consolidated model one gateway container serves every bottle over a
+single shared docker network, and each agent bottle attaches with a pinned,
+deterministic address that the gateway uses as its **attribution key**. This
+allocates those addresses from the network's subnet, skipping the reserved
+ones — the network address and broadcast (excluded by `hosts()`), docker's
+router `.1`, and everything already in use (`taken`: the gateway container
+plus every live bottle, which the caller reads from the registry).
+
+Pure `ipaddress` logic — the docker-specific bits (the subnet CIDR, the
+gateway container's own address) are gathered by the caller and passed in, so
+this stays testable without docker.
+"""
+
+from __future__ import annotations
+
+import ipaddress
+from collections.abc import Iterable
+
+
+class NoFreeAddressError(RuntimeError):
+    """The shared gateway network's subnet is exhausted — every host address
+    is reserved or already assigned to a bottle."""
+
+
+def next_free_ip(cidr: str, taken: Iterable[str]) -> str:
+    """The lowest host address in `cidr` not in `taken` and not docker's
+    router (`.1`). `taken` must include the gateway container's own address
+    and every live bottle's. Raises `NoFreeAddressError` if the subnet is
+    full."""
+    net = ipaddress.ip_network(cidr, strict=False)
+    reserved = {str(a) for a in taken}
+    # Docker assigns the network's first host (.1) to the bridge router; a
+    # bottle must never be handed that address.
+    reserved.add(str(net.network_address + 1))
+    for host in net.hosts():  # hosts() already excludes network + broadcast
+        candidate = str(host)
+        if candidate not in reserved:
+            return candidate
+    raise NoFreeAddressError(
+        f"no free address in {cidr} ({len(reserved)} reserved/assigned)"
+    )
+
+
+__all__ = ["next_free_ip", "NoFreeAddressError"]

bot_bottle/git_gate.py

@@ -46,6 +46,7 @@ from .git_gate_render import (
     git_gate_known_hosts_line,
     git_gate_render_access_hook,
     git_gate_render_entrypoint,
+    git_gate_render_provision,
     git_gate_render_gitconfig,
     git_gate_render_hook,
     git_gate_upstreams_for_bottle,
@@ -155,6 +156,7 @@ __all__ = [
     "git_gate_render_gitconfig",
     "git_gate_known_hosts_line",
     "git_gate_render_entrypoint",
+    "git_gate_render_provision",
     "git_gate_render_hook",
     "git_gate_render_access_hook",
     "provision_git_gate_dynamic_keys",

bot_bottle/git_gate_render.py

@@ -9,6 +9,7 @@ own; `git_gate` re-exports these names for API stability."""
 
 from __future__ import annotations
 
+import re
 import shlex
 from dataclasses import dataclass
 from pathlib import Path
@@ -125,22 +126,18 @@ def git_gate_known_hosts_line(host: str, port: str, key: str) -> str:
     return f"{target} {key}\n"
 
 
-def git_gate_render_entrypoint(upstreams: tuple[GitGateUpstream, ...]) -> str:
-    """Posix-sh entrypoint. One `init_repo` call per upstream, then
-    `exec git daemon`. The function reads
-    `/git-gate/creds/<name>-{key,known_hosts}` (bind-mounted into
-    the bundle by the renderer) and wires them into each bare repo's
-    config; the access-hook + pre-receive hook pick those paths up
-    at fetch / push time."""
-    lines = [
-        "#!/bin/sh",
-        "set -eu",
-        "",
+def _git_gate_init_repo_fn(repo_root: str, creds_dir: str) -> list[str]:
+    """The `init_repo` shell function, parameterized by the bare-repo root
+    and the per-bottle creds dir. Single source of the credential-wiring
+    logic, shared by the single-tenant daemon entrypoint (`/git`,
+    `/git-gate/creds`) and the consolidated per-bottle provisioning
+    (`/git/<bottle_id>`, `/git-gate/creds/<bottle_id>`)."""
+    return [
         "init_repo() {",
         "  name=$1",
         "  upstream_url=$2",
-        "  keyfile=/git-gate/creds/${name}-key",
-        "  hostsfile=/git-gate/creds/${name}-known_hosts",
+        f"  keyfile={creds_dir}/${{name}}-key",
+        f"  hostsfile={creds_dir}/${{name}}-known_hosts",
         "",
         # `|| true`: PRD 0018 chunk 3+ bind-mounts these RO from the
         # host, so chmod-syscalls fail with EROFS. The files already
@@ -153,14 +150,14 @@ def git_gate_render_entrypoint(upstreams: tuple[GitGateUpstream, ...]) -> str:
         "    chmod 600 \"$hostsfile\" 2>/dev/null || true",
         "  fi",
         "",
-        "  repo=/git/${name}.git",
+        f"  repo={repo_root}/${{name}}.git",
         "  if [ ! -d \"$repo\" ]; then",
         "    git init --bare \"$repo\" >/dev/null",
-        # --mirror=fetch sets remote.origin.fetch = +refs/*:refs/* so",
-        # a later `git fetch origin` mirrors the upstream's full ref",
-        # graph (heads, tags, notes) into the bare repo at canonical",
-        # paths. It does NOT set remote.origin.mirror=true, so an",
-        # explicit `git push origin <ref>:<ref>` still pushes one ref.",
+        # --mirror=fetch sets remote.origin.fetch = +refs/*:refs/* so a later
+        # `git fetch origin` mirrors the upstream's full ref graph (heads,
+        # tags, notes) into the bare repo at canonical paths. It does NOT set
+        # remote.origin.mirror=true, so an explicit `git push origin
+        # <ref>:<ref>` still pushes one ref.
         "    git -C \"$repo\" remote add --mirror=fetch origin \"$upstream_url\"",
         "  fi",
         "  git -C \"$repo\" config git-gate.identityFile \"$keyfile\"",
@@ -170,9 +167,19 @@ def git_gate_render_entrypoint(upstreams: tuple[GitGateUpstream, ...]) -> str:
         "  git -C \"$repo\" config http.receivepack true",
         "  install -m 755 /etc/git-gate/pre-receive \"$repo/hooks/pre-receive\"",
         "}",
-        "",
-        "mkdir -p /git",
     ]
+
+
+def git_gate_render_entrypoint(upstreams: tuple[GitGateUpstream, ...]) -> str:
+    """Posix-sh entrypoint. One `init_repo` call per upstream, then
+    `exec git daemon`. The function reads
+    `/git-gate/creds/<name>-{key,known_hosts}` (bind-mounted into
+    the bundle by the renderer) and wires them into each bare repo's
+    config; the access-hook + pre-receive hook pick those paths up
+    at fetch / push time."""
+    lines = ["#!/bin/sh", "set -eu", ""]
+    lines += _git_gate_init_repo_fn("/git", "/git-gate/creds")
+    lines += ["", "mkdir -p /git"]
     for u in upstreams:
         lines.append(f"init_repo {shlex.quote(u.name)} {shlex.quote(u.upstream_url)}")
     lines.extend([
@@ -190,6 +197,35 @@ def git_gate_render_entrypoint(upstreams: tuple[GitGateUpstream, ...]) -> str:
     return "\n".join(lines) + "\n"
 
 
+# A bottle id namespaces the consolidated gateway's repo + creds dirs; it is
+# embedded unquoted in the provisioning script, so restrict it to a shell- and
+# path-safe alphabet (registry ids are token_hex — this is defense in depth).
+_SAFE_BOTTLE_ID = re.compile(r"[A-Za-z0-9_-]+")
+
+
+def git_gate_render_provision(
+    bottle_id: str, upstreams: tuple[GitGateUpstream, ...],
+) -> str:
+    """Posix-sh script that provisions ONE bottle's bare repos into the
+    consolidated gateway (PRD 0070), under `/git/<bottle_id>/` with creds
+    read from `/git-gate/creds/<bottle_id>/`. Init-only — no `git daemon`,
+    since the shared gateway already serves every bottle; run inside the
+    running gateway when the bottle is registered.
+
+    Isolating each bottle's repo root and creds dir by id is what keeps one
+    bottle's push credentials out of another's repos on the shared gateway."""
+    if not _SAFE_BOTTLE_ID.fullmatch(bottle_id):
+        raise ValueError(f"git-gate: unsafe bottle id {bottle_id!r}")
+    repo_root = f"/git/{bottle_id}"
+    creds_dir = f"/git-gate/creds/{bottle_id}"
+    lines = ["#!/bin/sh", "set -eu", ""]
+    lines += _git_gate_init_repo_fn(repo_root, creds_dir)
+    lines += ["", f"mkdir -p {shlex.quote(repo_root)}"]
+    for u in upstreams:
+        lines.append(f"init_repo {shlex.quote(u.name)} {shlex.quote(u.upstream_url)}")
+    return "\n".join(lines) + "\n"
+
+
 def git_gate_render_hook() -> str:
     """The shared pre-receive hook: gitleaks-scan all incoming refs,
     then forward each accepted ref to the real upstream (`origin`)

tests/unit/test_gateway_net.py

@@ -0,0 +1,42 @@
+"""Unit: shared-gateway source-IP allocation (PRD 0070)."""
+
+from __future__ import annotations
+
+import unittest
+
+from bot_bottle.backend.docker.gateway_net import NoFreeAddressError, next_free_ip
+
+
+class TestNextFreeIp(unittest.TestCase):
+    def test_skips_router_and_returns_first_host(self) -> None:
+        # .1 is docker's router; the first assignable address is .2.
+        self.assertEqual("172.18.0.2", next_free_ip("172.18.0.0/16", []))
+
+    def test_skips_taken_addresses(self) -> None:
+        # Gateway container holds .2, a live bottle holds .3 -> next is .4.
+        self.assertEqual(
+            "172.18.0.4", next_free_ip("172.18.0.0/16", ["172.18.0.2", "172.18.0.3"]),
+        )
+
+    def test_taken_order_does_not_matter(self) -> None:
+        self.assertEqual(
+            "172.18.0.2", next_free_ip("172.18.0.0/16", ["172.18.0.3", "172.18.0.5"]),
+        )
+
+    def test_allocation_is_deterministic(self) -> None:
+        taken = ["172.18.0.2"]
+        self.assertEqual(next_free_ip("172.18.0.0/16", taken),
+                         next_free_ip("172.18.0.0/16", taken))
+
+    def test_raises_when_subnet_exhausted(self) -> None:
+        # /30: hosts are .1 (router, reserved) and .2; taking .2 leaves none.
+        with self.assertRaises(NoFreeAddressError):
+            next_free_ip("10.9.9.0/30", ["10.9.9.2"])
+
+    def test_accepts_host_bits_set_cidr(self) -> None:
+        # A container's inspected address arrives as e.g. 172.18.0.2/16.
+        self.assertEqual("172.18.0.2", next_free_ip("172.18.0.5/16", []))
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/unit/test_git_gate_provision_render.py

@@ -0,0 +1,67 @@
+"""Unit: consolidated per-bottle git-gate provisioning render (PRD 0070)."""
+
+from __future__ import annotations
+
+import unittest
+
+from bot_bottle.git_gate_render import (
+    GitGateUpstream,
+    git_gate_render_entrypoint,
+    git_gate_render_provision,
+)
+
+
+def _ups(*names: str) -> tuple[GitGateUpstream, ...]:
+    return tuple(
+        GitGateUpstream(
+            name=n,
+            upstream_url=f"ssh://git@github.com/x/{n}.git",
+            upstream_host="github.com",
+            upstream_port="22",
+            identity_file="",
+            known_host_key="",
+        )
+        for n in names
+    )
+
+
+class TestProvisionRender(unittest.TestCase):
+    def test_namespaces_repos_and_creds_by_bottle_id(self) -> None:
+        script = git_gate_render_provision("bottleab12", _ups("foo"))
+        self.assertIn("repo=/git/bottleab12/${name}.git", script)
+        self.assertIn("keyfile=/git-gate/creds/bottleab12/${name}-key", script)
+        self.assertIn("mkdir -p /git/bottleab12", script)
+
+    def test_one_init_repo_call_per_upstream(self) -> None:
+        script = git_gate_render_provision("b1", _ups("foo", "bar"))
+        calls = [l for l in script.splitlines() if l.startswith("init_repo ")]
+        self.assertEqual(2, len(calls))
+
+    def test_provision_does_not_start_the_daemon(self) -> None:
+        # The shared gateway already serves; provisioning is init-only.
+        self.assertNotIn("git daemon", git_gate_render_provision("b1", _ups("foo")))
+
+    def test_installs_pre_receive_hook(self) -> None:
+        script = git_gate_render_provision("b1", _ups("foo"))
+        self.assertIn("install -m 755 /etc/git-gate/pre-receive", script)
+
+    def test_rejects_unsafe_bottle_id(self) -> None:
+        for bad in ("../etc", "a/b", "a b", "a;rm", ""):
+            with self.assertRaises(ValueError):
+                git_gate_render_provision(bad, _ups("foo"))
+
+
+class TestEntrypointUnchanged(unittest.TestCase):
+    """The shared `_git_gate_init_repo_fn` refactor must not alter the
+    single-tenant daemon entrypoint's output."""
+
+    def test_entrypoint_still_single_tenant_flat(self) -> None:
+        script = git_gate_render_entrypoint(_ups("foo"))
+        self.assertIn("repo=/git/${name}.git", script)      # flat, not namespaced
+        self.assertIn("keyfile=/git-gate/creds/${name}-key", script)
+        self.assertIn("--base-path=/git", script)
+        self.assertIn("exec git daemon", script)
+
+
+if __name__ == "__main__":
+    unittest.main()