appc,feature/conn25,net: Add DNS response interception for conn25

The new version of app connector (conn25) needs to read DNS responses for domains it is interested in and store and swap out IP addresses. Add a hook to dns manager to enable this. Give the conn25 updated netmaps so that it knows when to assign connecting addresses and from what pool. Assign an address when we see a DNS response for a domain we are interested in, but don't do anything with the address yet. Updates tailscale/corp#34252 Signed-off-by: Fran Bull <fran@tailscale.com>
2026-01-28 14:07:08 -08:00
parent cae54e2046
commit 3b737edbf1
11 changed files with 1000 additions and 292 deletions
@@ -0,0 +1,60 @@
+// Copyright (c) Tailscale Inc & contributors
+// SPDX-License-Identifier: BSD-3-Clause
+
+package conn25
+
+import (
+	"errors"
+	"net/netip"
+	"testing"
+
+	"go4.org/netipx"
+	"tailscale.com/util/must"
+)
+
+func TestNext(t *testing.T) {
+	a := ippool{}
+	_, err := a.next()
+	if !errors.Is(err, errPoolExhausted) {
+		t.Fatalf("expected errPoolExhausted, got %v", err)
+	}
+
+	var isb netipx.IPSetBuilder
+	ipset := must.Get(isb.IPSet())
+	b := newIPPool(ipset)
+	_, err = b.next()
+	if !errors.Is(err, errPoolExhausted) {
+		t.Fatalf("expected errPoolExhausted, got %v", err)
+	}
+
+	isb.AddRange(netipx.IPRangeFrom(netip.MustParseAddr("192.168.0.0"), netip.MustParseAddr("192.168.0.2")))
+	isb.AddRange(netipx.IPRangeFrom(netip.MustParseAddr("200.0.0.0"), netip.MustParseAddr("200.0.0.0")))
+	isb.AddRange(netipx.IPRangeFrom(netip.MustParseAddr("201.0.0.0"), netip.MustParseAddr("201.0.0.1")))
+	ipset = must.Get(isb.IPSet())
+	c := newIPPool(ipset)
+	expected := []string{
+		"192.168.0.0",
+		"192.168.0.1",
+		"192.168.0.2",
+		"200.0.0.0",
+		"201.0.0.0",
+		"201.0.0.1",
+	}
+	for i, want := range expected {
+		addr, err := c.next()
+		if err != nil {
+			t.Fatal(err)
+		}
+		if addr != netip.MustParseAddr(want) {
+			t.Fatalf("next call %d want: %s, got: %v", i, want, addr)
+		}
+	}
+	_, err = c.next()
+	if !errors.Is(err, errPoolExhausted) {
+		t.Fatalf("expected errPoolExhausted, got %v", err)
+	}
+	_, err = c.next()
+	if !errors.Is(err, errPoolExhausted) {
+		t.Fatalf("expected errPoolExhausted, got %v", err)
+	}
+}