banger/internal/daemon/nat.go
Thales Maciel 362009d747
daemon split (1/5): extract *HostNetwork service
First phase of splitting the daemon god-struct into focused services
with explicit ownership.

HostNetwork now owns everything host-networking: the TAP interface
pool (initializeTapPool / ensureTapPool / acquireTap / releaseTap /
createTap), bridge + socket dir setup, firecracker process primitives
(find/resolve/kill/wait/ensureSocketAccess/sendCtrlAltDel), DM
snapshot lifecycle, NAT rule enforcement, guest DNS server lifecycle
+ routing setup, and the vsock-agent readiness probe. That's 7 files
whose receivers flipped from *Daemon to *HostNetwork, plus a new
host_network.go that declares the struct, its hostNetworkDeps, and
the factored firecracker + DNS helpers that used to live in vm.go.

Daemon gives up the tapPool and vmDNS fields entirely; they're now
HostNetwork's business. Construction goes through newHostNetwork in
Daemon.Open with an explicit dependency bag (runner, logger, config,
layout, closing). A lazy-init hostNet() helper on Daemon supports
test literals that don't wire net explicitly — production always
populates it eagerly.

Signature tightenings where the old receiver reached into VM-service
state:
 - ensureNAT(ctx, vm, enable) → ensureNAT(ctx, guestIP, tap, enable).
   Callers resolve tap from the handle cache themselves.
 - initializeTapPool(ctx) → initializeTapPool(usedTaps []string).
   Daemon.Open enumerates VMs, collects taps from handles, hands the
   slice in.

rebuildDNS stays on *Daemon as the orchestrator — it filters by
vm-alive (a VMService concern handles will move to in phase 4) then
calls HostNetwork.replaceDNS with the already-filtered map.

Capability hooks continue to take *Daemon; they now use it as a
facade to reach services (d.net.ensureNAT, d.hostNet().*). Planned
CapabilityHost interface extraction is orthogonal, left for later.

Tests: dns_routing_test.go + fastpath_test.go + nat_test.go +
snapshot_test.go + open_close_test.go were touched to construct
HostNetwork literals where they exercise its methods directly, or
route through d.hostNet() where they exercise the Daemon entry
points.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2026-04-20 20:11:46 -03:00

78 lines
2.3 KiB
Go

package daemon
import (
"context"
"banger/internal/hostnat"
"banger/internal/model"
"banger/internal/system"
)
type natRule = hostnat.Rule
// ensureNAT takes tap explicitly rather than reading from a handle
// cache so HostNetwork stays decoupled from VM-service state.
// Callers (vm_lifecycle) resolve the tap device from the handle cache
// themselves and pass it in.
func (n *HostNetwork) ensureNAT(ctx context.Context, guestIP, tap string, enable bool) error {
return hostnat.Ensure(ctx, n.runner, guestIP, tap, enable)
}
func (n *HostNetwork) validateNATPrereqs(ctx context.Context) (string, error) {
checks := system.NewPreflight()
checks.RequireCommand("ip", toolHint("ip"))
n.addNATPrereqs(ctx, checks)
if err := checks.Err("nat preflight failed"); err != nil {
return "", err
}
return n.defaultUplink(ctx)
}
func (n *HostNetwork) addNATPrereqs(ctx context.Context, checks *system.Preflight) {
checks.RequireCommand("iptables", toolHint("iptables"))
checks.RequireCommand("sysctl", toolHint("sysctl"))
runner := n.runner
if runner == nil {
runner = system.NewRunner()
}
out, err := runner.Run(ctx, "ip", "route", "show", "default")
if err != nil {
checks.Addf("failed to inspect the default route for NAT: %v", err)
return
}
if _, err := parseDefaultUplink(string(out)); err != nil {
checks.Addf("failed to detect the uplink interface for NAT: %v", err)
}
}
func (n *HostNetwork) defaultUplink(ctx context.Context) (string, error) {
return hostnat.DefaultUplink(ctx, n.runner)
}
func parseDefaultUplink(output string) (string, error) {
return hostnat.ParseDefaultUplink(output)
}
// natRulesForVM builds the iptables rule set for vm + tap + uplink.
// tap is passed explicitly (rather than read from a handle cache)
// because natRulesForVM has no Daemon receiver — it's usable from
// test helpers that build rule expectations without a daemon.
func natRulesForVM(vm model.VMRecord, tap, uplink string) ([]natRule, error) {
return hostnat.Rules(vm.Runtime.GuestIP, tap, uplink)
}
func natRuleArgs(action string, rule natRule) []string {
return hostnat.RuleArgs(action, rule)
}
func natAddPlan(rules []natRule) [][]string {
return hostnat.AddPlan(rules)
}
func natRemovePlan(rules []natRule) [][]string {
return hostnat.RemovePlan(rules)
}
func natRuleKey(rule natRule) string {
return hostnat.RuleKey(rule)
}