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cmd/natc: error and log when IP range is exhausted

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natc itself can't immediately fix the problem, but it can more correctly
error that return bad addresses.

Updates tailscale/corp#26968

Signed-off-by: James Tucker <james@tailscale.com>
This commit is contained in:
James Tucker 2025-03-07 14:27:13 -07:00 committed by James Tucker
parent b9f4c5d246
commit 69b27d2fcf
1 changed files with 15 additions and 7 deletions
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22
cmd/natc/natc.go
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@ -41,6 +41,8 @@
"tailscale.com/wgengine/netstack"
)
var ErrNoIPsAvailable = errors.New("no IPs available")
func main() {
hostinfo.SetApp("natc")
if !envknob.UseWIPCode() {
@ -277,14 +279,14 @@ func (c *connector) handleDNS(pc net.PacketConn, buf []byte, remoteAddr *net.UDP
defer cancel()
who, err := c.lc.WhoIs(ctx, remoteAddr.String())
if err != nil {
log.Printf("HandleDNS: WhoIs failed: %v\n", err)
log.Printf("HandleDNS(remote=%s): WhoIs failed: %v\n", remoteAddr.String(), err)
return
}
var msg dnsmessage.Message
err = msg.Unpack(buf)
if err != nil {
log.Printf("HandleDNS: dnsmessage unpack failed: %v\n ", err)
log.Printf("HandleDNS(remote=%s): dnsmessage unpack failed: %v\n", remoteAddr.String(), err)
return
}
@ -297,19 +299,19 @@ func (c *connector) handleDNS(pc net.PacketConn, buf []byte, remoteAddr *net.UDP
case dnsmessage.TypeAAAA, dnsmessage.TypeA:
dstAddrs, err := lookupDestinationIP(q.Name.String())
if err != nil {
log.Printf("HandleDNS: lookup destination failed: %v\n ", err)
log.Printf("HandleDNS(remote=%s): lookup destination failed: %v\n", remoteAddr.String(), err)
return
}
if c.ignoreDestination(dstAddrs) {
bs, err := dnsResponse(&msg, dstAddrs)
// TODO (fran): treat as SERVFAIL
if err != nil {
log.Printf("HandleDNS: generate ignore response failed: %v\n", err)
log.Printf("HandleDNS(remote=%s): generate ignore response failed: %v\n", remoteAddr.String(), err)
return
}
_, err = pc.WriteTo(bs, remoteAddr)
if err != nil {
log.Printf("HandleDNS: write failed: %v\n", err)
log.Printf("HandleDNS(remote=%s): write failed: %v\n", remoteAddr.String(), err)
}
return
}
@ -322,7 +324,7 @@ func (c *connector) handleDNS(pc net.PacketConn, buf []byte, remoteAddr *net.UDP
resp, err := c.generateDNSResponse(&msg, who.Node.ID)
// TODO (fran): treat as SERVFAIL
if err != nil {
log.Printf("HandleDNS: connector handling failed: %v\n", err)
log.Printf("HandleDNS(remote=%s): connector handling failed: %v\n", remoteAddr.String(), err)
return
}
// TODO (fran): treat as NXDOMAIN
@ -332,7 +334,7 @@ func (c *connector) handleDNS(pc net.PacketConn, buf []byte, remoteAddr *net.UDP
// This connector handled the DNS request
_, err = pc.WriteTo(resp, remoteAddr)
if err != nil {
log.Printf("HandleDNS: write failed: %v\n", err)
log.Printf("HandleDNS(remote=%s): write failed: %v\n", remoteAddr.String(), err)
}
}
@ -529,6 +531,9 @@ func (ps *perPeerState) ipForDomain(domain string) ([]netip.Addr, error) {
return addrs, nil
}
addrs := ps.assignAddrsLocked(domain)
if addrs == nil {
return nil, ErrNoIPsAvailable
}
return addrs, nil
}
@ -575,6 +580,9 @@ func (ps *perPeerState) assignAddrsLocked(domain string) []netip.Addr {
ps.addrToDomain = &bart.Table[string]{}
}
v4 := ps.unusedIPv4Locked()
if !v4.IsValid() {
return nil
}
as16 := ps.c.v6ULA.Addr().As16()
as4 := v4.As4()
copy(as16[12:], as4[:])