Improve captive portal handling

resolver/resolver-env.go

@@ -0,0 +1,95 @@
+package resolver
+
+import (
+	"context"
+	"fmt"
+	"net"
+
+	"github.com/miekg/dns"
+	"github.com/safing/portbase/log"
+	"github.com/safing/portmaster/netenv"
+	"github.com/safing/portmaster/network/netutils"
+)
+
+var (
+	envResolver = &Resolver{
+		Server:        ServerSourceEnv,
+		ServerType:    ServerTypeEnv,
+		ServerIPScope: netutils.SiteLocal,
+		Source:        ServerSourceEnv,
+		Conn:          &envResolverConn{},
+	}
+)
+
+type envResolverConn struct{}
+
+func (er *envResolverConn) Query(ctx context.Context, q *Query) (*RRCache, error) {
+	// prepping
+	portal := netenv.GetCaptivePortal()
+
+	// check for matching name
+	switch q.FQDN {
+	case netenv.SpecialCaptivePortalDomain:
+		if portal.IP != nil {
+			rr, err := portal.IPasRR()
+			if err != nil {
+				log.Warningf("nameserver: failed to create captive portal response to %s: %s", q.FQDN, err)
+				return nil, ErrNotFound
+			}
+			return er.makeRRCache(q, []dns.RR{rr}), nil
+		}
+		return nil, ErrNotFound
+
+	case "router.local.":
+		routers := netenv.Gateways()
+		if len(routers) == 0 {
+			return nil, ErrNotFound
+		}
+		records, err := ipsToRRs(q.FQDN, routers)
+		if err != nil {
+			log.Warningf("nameserver: failed to create gateway response to %s: %s", q.FQDN, err)
+			return nil, ErrNotFound
+		}
+		return er.makeRRCache(q, records), nil
+	}
+
+	// no match
+	return nil, ErrContinue // continue with next resolver
+}
+
+func (er *envResolverConn) makeRRCache(q *Query, answers []dns.RR) *RRCache {
+	q.NoCaching = true // disable caching, as the env always has the data available and more up to date.
+	return &RRCache{
+		Domain:      q.FQDN,
+		Question:    q.QType,
+		Answer:      answers,
+		Server:      envResolver.Server,
+		ServerScope: envResolver.ServerIPScope,
+	}
+}
+
+func (er *envResolverConn) ReportFailure() {}
+
+func (er *envResolverConn) IsFailing() bool {
+	return false
+}
+
+func ipsToRRs(domain string, ips []net.IP) ([]dns.RR, error) {
+	var records []dns.RR
+	var rr dns.RR
+	var err error
+
+	for _, ip := range ips {
+		if ip.To4() != nil {
+			rr, err = dns.NewRR(domain + " 17 IN A " + ip.String())
+		} else {
+			rr, err = dns.NewRR(domain + " 17 IN AAAA " + ip.String())
+		}
+		if err != nil {
+			return nil, fmt.Errorf("failed to create record for %s: %w", ip, err)
+		}
+		records = append(records, rr)
+	}
+
+	return records, nil
+}