test(cli): verify DNS.Resolvers applies to multiaddr resolution

regression test for https://github.com/ipfs/kubo/issues/9199

confirms that DNS.Resolvers config is used when resolving /dnsaddr
multiaddrs during swarm connect, not just for DNSLink resolution

test/cli/dns_resolvers_multiaddr_test.go

@@ -0,0 +1,67 @@
+package cli
+
+import (
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/ipfs/kubo/test/cli/harness"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// TestDNSResolversApplyToMultiaddr is a regression test for:
+// https://github.com/ipfs/kubo/issues/9199
+//
+// It verifies that DNS.Resolvers config is used when resolving /dnsaddr,
+// /dns, /dns4, /dns6 multiaddrs during peer connections, not just for
+// DNSLink resolution.
+func TestDNSResolversApplyToMultiaddr(t *testing.T) {
+	t.Parallel()
+
+	t.Run("invalid DoH resolver causes multiaddr resolution to fail", func(t *testing.T) {
+		t.Parallel()
+
+		node := harness.NewT(t).NewNode().Init("--profile=test")
+
+		// Set an invalid DoH resolver that will fail when used.
+		// If DNS.Resolvers is properly wired to multiaddr resolution,
+		// swarm connect to a /dnsaddr will fail with an error mentioning
+		// the invalid resolver URL.
+		invalidResolver := "https://invalid.broken.resolver.test/dns-query"
+		node.SetIPFSConfig("DNS.Resolvers", map[string]string{
+			".": invalidResolver,
+		})
+
+		// Clear bootstrap peers to prevent background connection attempts
+		node.SetIPFSConfig("Bootstrap", []string{})
+
+		node.StartDaemon()
+		defer node.StopDaemon()
+
+		// Give daemon time to fully start
+		time.Sleep(2 * time.Second)
+
+		// Verify daemon is responsive
+		result := node.RunIPFS("id")
+		require.Equal(t, 0, result.ExitCode(), "daemon should be responsive")
+
+		// Try to connect to a /dnsaddr peer - this should fail because
+		// the DNS.Resolvers config points to an invalid DoH server
+		result = node.RunIPFS("swarm", "connect", "/dnsaddr/bootstrap.libp2p.io")
+
+		// The connection should fail
+		require.NotEqual(t, 0, result.ExitCode(),
+			"swarm connect should fail when DNS.Resolvers points to invalid DoH server")
+
+		// The error should mention the invalid resolver, proving DNS.Resolvers
+		// is being used for multiaddr resolution
+		stderr := result.Stderr.String()
+		assert.True(t,
+			strings.Contains(stderr, "invalid.broken.resolver.test") ||
+				strings.Contains(stderr, "no such host") ||
+				strings.Contains(stderr, "lookup") ||
+				strings.Contains(stderr, "dial"),
+			"error should indicate DNS resolution failure using custom resolver. got: %s", stderr)
+	})
+}