abrown38andClaude Opus 5.5
5e6c61cc8e
- interfaces.exclude in steward.yaml (names or shell patterns) leaves interfaces out of GET /interfaces, the web UI's picker and 'steward interface list'. Subnets on them are still served. - With the ping check on, active leases are pinged every minute; a client that answers gets a last-seen time (leases.last_seen, migration 4). Not answering never takes a client offline. - The activity log filters by subnet (--subnet, the Activity page, GET /events?subnet=). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
85 lines
2.1 KiB
Go
85 lines
2.1 KiB
Go
package dhcpd
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import (
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"context"
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"log/slog"
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"net"
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"net/netip"
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"os"
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"sync"
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"sync/atomic"
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"time"
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"golang.org/x/net/icmp"
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"golang.org/x/net/ipv4"
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)
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// ICMPPinger pings with an unprivileged ICMP socket (Linux "ping sockets",
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// allowed for the groups in net.ipv4.ping_group_range, which systemd opens
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// to everyone). When the socket can't be opened, the check is skipped and
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// Unavailable says why.
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type ICMPPinger struct {
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Log *slog.Logger
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seq atomic.Uint32
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once sync.Once
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// Unavailable is why pings can't be sent ("" when they can).
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Unavailable atomic.Value
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}
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// Ping reports whether a answers an echo request within timeout.
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func (p *ICMPPinger) Ping(ctx context.Context, a netip.Addr, timeout time.Duration) bool {
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conn, err := icmp.ListenPacket("udp4", "0.0.0.0")
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if err != nil {
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p.once.Do(func() {
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msg := "can't send pings, so addresses aren't checked before they are offered and clients' last-seen times aren't known: " + err.Error() + " (check net.ipv4.ping_group_range)"
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p.Unavailable.Store(msg)
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if p.Log != nil {
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p.Log.Warn(msg)
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}
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})
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return false
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}
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defer conn.Close()
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seq := int(p.seq.Add(1) & 0xffff)
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msg := icmp.Message{Type: ipv4.ICMPTypeEcho, Body: &icmp.Echo{ID: os.Getpid() & 0xffff, Seq: seq, Data: []byte("steward")}}
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b, err := msg.Marshal(nil)
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if err != nil {
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return false
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}
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dst := &net.UDPAddr{IP: a.AsSlice()}
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if _, err := conn.WriteTo(b, dst); err != nil {
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return false
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}
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deadline := time.Now().Add(timeout)
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if d, ok := ctx.Deadline(); ok && d.Before(deadline) {
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deadline = d
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}
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conn.SetReadDeadline(deadline)
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buf := make([]byte, 1500)
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for {
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n, from, err := conn.ReadFrom(buf)
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if err != nil {
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return false
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}
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ua, ok := from.(*net.UDPAddr)
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if !ok || !ua.IP.Equal(dst.IP) {
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continue
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}
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m, err := icmp.ParseMessage(1, buf[:n])
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if err != nil {
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continue
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}
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if e, ok := m.Body.(*icmp.Echo); ok && m.Type == ipv4.ICMPTypeEchoReply && e.Seq == seq {
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return true
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}
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}
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}
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// Problem says why pings can't be sent ("" when they can).
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func (p *ICMPPinger) Problem() string {
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if v, ok := p.Unavailable.Load().(string); ok {
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return v
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}
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return ""
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}
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