91 lines
3.7 KiB
Go
91 lines
3.7 KiB
Go
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package networking
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import (
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"context"
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"fmt"
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"os/exec"
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"time"
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"nadir/internal/oscmd"
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)
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// backend is the write-side abstraction. Each host network manager (nmcli,
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// networkd, ifupdown) implements this. Reads go through `ip -j` and
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// /etc/resolv.conf regardless - they are backend-agnostic (see read.go).
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//
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// When detect() finds no backend, Module.be is nil and all write endpoints
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// return 501 Not Implemented. Reads still work.
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// Methods that shell out take a context so a request that is cancelled (client
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// disconnect, timeout) kills the slow command (e.g. `nmcli con up` waiting on
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// DHCP). The timer-driven auto-revert, which must finish even with no client,
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// passes context.Background().
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type backend interface {
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// Name returns the backend identifier ("nmcli", "networkd", "ifupdown").
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Name() string
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// Snapshot captures the current IPv4 configuration of iface so it can be
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// restored on rollback. The returned IfaceConfig is backend-specific:
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// nmcli reads from NM's connection, networkd/ifupdown read their config
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// files, falling back to live `ip` output when no managed file exists
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// (in which case Method is "dhcp" - safest revert assumption).
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Snapshot(ctx context.Context, iface string) (IfaceConfig, error)
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// Apply replaces the interface's IPv4 configuration with cfg. It is the
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// caller's responsibility to have taken a Snapshot first (the rollback
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// mechanism does this). Apply must be idempotent: calling it with the
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// same cfg twice should leave the system in the same state.
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Apply(ctx context.Context, iface string, cfg IfaceConfig) error
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// SetLinkUp brings the interface up.
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SetLinkUp(ctx context.Context, iface string) error
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// SetLinkDown takes the interface down.
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SetLinkDown(ctx context.Context, iface string) error
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}
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// detect probes the host for a supported network manager, in priority order:
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//
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// 1. nmcli (NetworkManager) - the majority of desktop and modern server installs
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// 2. networkctl (systemd-networkd) - common on minimal/container hosts
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// 3. ifup/ifdown (ifupdown) - classic Debian/Ubuntu servers
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//
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// Returns nil when none is found. The order matters: some distros ship both NM
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// and networkd; NM wins because it's the active manager in that case.
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func detect() backend {
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if _, err := exec.LookPath("nmcli"); err == nil {
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if _, err := oscmd.Run("nmcli", "general", "status"); err == nil {
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return &nmcliBackend{}
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}
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}
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if _, err := exec.LookPath("networkctl"); err == nil {
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if _, err := oscmd.Run("systemctl", "is-active", "--quiet", "systemd-networkd"); err == nil {
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return &networkdBackend{}
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}
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}
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if _, err := exec.LookPath("ifup"); err == nil {
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if _, err := exec.LookPath("ifdown"); err == nil {
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return &ifupdownBackend{}
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}
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}
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return nil
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}
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// pendingChange tracks a single in-flight change that has been applied but not
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// yet confirmed. revert undoes it (re-apply the prior config, or bring a
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// downed link back up). If the timer fires before confirmation, revert runs -
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// protecting against lock-yourself-out mistakes.
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//
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// ponytail: one slot for the whole module, not per-interface. An admin makes one
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// change at a time; a concurrent change to another iface is rejected with a 409
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// that says so. Key it by iface (a map) if multi-interface concurrency is ever
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// needed.
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type pendingChange struct {
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Iface string // interface that was changed
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revert func() error // undoes the change, for rollback
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Timer *time.Timer // fires the auto-revert
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Deadline time.Time // when the timer will fire (for the status endpoint)
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}
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// errNoBackend is the 501 returned when no write backend was detected.
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var errNoBackend = fmt.Errorf("no supported network backend detected (tried nmcli, networkctl, ifup/ifdown)")
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