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cmd/natc: fix ip allocation runtime

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Avoid the unbounded runtime during random allocation, if random
allocation fails after a first pass at random through the provided
ranges, pick the next free address by walking through the allocated set.

The new ipx utilities provide a bitset based allocation pool, good for
small to moderate ranges of IPv4 addresses as used in natc.

Updates #15367

Signed-off-by: James Tucker <james@tailscale.com>
This commit is contained in:
James Tucker
2025-03-25 12:59:07 -07:00
committed by James Tucker
parent fb47824d74
commit 95034e15a7
4 changed files with 325 additions and 97 deletions
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33
cmd/natc/natc_test.go
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@@ -43,17 +43,6 @@ func TestULA(t *testing.T) {
}
}
func TestRandV4(t *testing.T) {
pfx := netip.MustParsePrefix("100.64.1.0/24")
for i := 0; i < 512; i++ {
ip := randV4(pfx)
if !pfx.Contains(ip) {
t.Errorf("randV4(%s) = %s; not contained in prefix", pfx, ip)
}
}
}
func TestDNSResponse(t *testing.T) {
tests := []struct {
name string
@@ -227,11 +216,9 @@ func TestDNSResponse(t *testing.T) {
func TestPerPeerState(t *testing.T) {
c := &connector{
v4Ranges: []netip.Prefix{netip.MustParsePrefix("100.64.1.0/24")},
v6ULA: netip.MustParsePrefix("fd7a:115c:a1e0:a99c:0001::/80"),
dnsAddr: netip.MustParseAddr("100.64.1.0"),
numV4DNSAddrs: (1<<(32-24) - 1),
v6ULA: netip.MustParsePrefix("fd7a:115c:a1e0:a99c:0001::/80"),
}
c.setPrefixes([]netip.Prefix{netip.MustParsePrefix("100.64.1.0/24")})
ps := &perPeerState{c: c}
@@ -255,8 +242,8 @@ func TestPerPeerState(t *testing.T) {
t.Errorf("Second address is not IPv6: %s", v6)
}
if !c.v4Ranges[0].Contains(v4) {
t.Errorf("IPv4 address %s not in range %s", v4, c.v4Ranges[0])
if !c.ipset.Contains(v4) {
t.Errorf("IPv4 address %s not in range %s", v4, c.ipset)
}
domain, ok := ps.domainForIP(v4)
@@ -331,11 +318,9 @@ func TestIgnoreDestination(t *testing.T) {
func TestConnectorGenerateDNSResponse(t *testing.T) {
c := &connector{
v4Ranges: []netip.Prefix{netip.MustParsePrefix("100.64.1.0/24")},
v6ULA: netip.MustParsePrefix("fd7a:115c:a1e0:a99c:0001::/80"),
dnsAddr: netip.MustParseAddr("100.64.1.0"),
numV4DNSAddrs: (1<<(32-24) - 1),
v6ULA: netip.MustParsePrefix("fd7a:115c:a1e0:a99c:0001::/80"),
}
c.setPrefixes([]netip.Prefix{netip.MustParsePrefix("100.64.1.0/24")})
req := &dnsmessage.Message{
Header: dnsmessage.Header{ID: 1234},
@@ -371,11 +356,9 @@ func TestConnectorGenerateDNSResponse(t *testing.T) {
func TestIPPoolExhaustion(t *testing.T) {
smallPrefix := netip.MustParsePrefix("100.64.1.0/30") // Only 4 IPs: .0, .1, .2, .3
c := &connector{
v6ULA: netip.MustParsePrefix("fd7a:115c:a1e0:a99c:0001::/80"),
v4Ranges: []netip.Prefix{smallPrefix},
dnsAddr: netip.MustParseAddr("100.64.1.0"),
numV4DNSAddrs: 3,
v6ULA: netip.MustParsePrefix("fd7a:115c:a1e0:a99c:0001::/80"),
}
c.setPrefixes([]netip.Prefix{smallPrefix})
ps := &perPeerState{c: c}