updated error handling for query

Signed-off-by: Dhruv-J <[email protected]>

pkg/agent/apiserver/handlers/fqdncache/handler.go

@@ -18,6 +18,7 @@ import (
 	"encoding/json"
 	"net/http"
 	"net/url"
+	"regexp"
 
 	"k8s.io/klog/v2"
 
@@ -27,7 +28,7 @@ import (
 
 func HandleFunc(npq querier.AgentNetworkPolicyInfoQuerier) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		fqdnFilter := newFilterFromURLQuery(r.URL.Query())
+		fqdnFilter := newFilterFromURLQuery(w, r.URL.Query())
 		dnsEntryCache := npq.GetFQDNCache(fqdnFilter)
 		resp := make([]agentapi.FQDNCacheResponse, 0, len(dnsEntryCache))
 		for _, entry := range dnsEntryCache {
@@ -44,9 +45,14 @@ func HandleFunc(npq querier.AgentNetworkPolicyInfoQuerier) http.HandlerFunc {
 	}
 }
 
-func newFilterFromURLQuery(query url.Values) *querier.FQDNCacheFilter {
+func newFilterFromURLQuery(w http.ResponseWriter, query url.Values) *querier.FQDNCacheFilter {
 	if len(query) == 0 {
 		return nil
 	}
+	_, err := regexp.Compile(query.Get("domain"))
+	if err != nil {
+		http.Error(w, "Regex formatted incorrectly to parse: "+err.Error(), http.StatusPreconditionFailed)
+		klog.ErrorS(err, "Regex formatted incorrectly to parse")
+	}
 	return &querier.FQDNCacheFilter{Domain: query.Get("domain")}
 }

pkg/agent/apiserver/handlers/fqdncache/handler_test.go

@@ -19,6 +19,7 @@ import (
 	"net"
 	"net/http"
 	"net/http/httptest"
+	"net/url"
 	"testing"
 	"time"
 
@@ -28,6 +29,7 @@ import (
 
 	"antrea.io/antrea/pkg/agent/apis"
 	"antrea.io/antrea/pkg/agent/types"
+	"antrea.io/antrea/pkg/querier"
 	queriertest "antrea.io/antrea/pkg/querier/testing"
 )
 
@@ -108,3 +110,49 @@ func TestFqdnCacheQuery(t *testing.T) {
 		})
 	}
 }
+
+func TestNewFilterFromURLQuery(t *testing.T) {
+	tests := []struct {
+		name           string
+		queryParams    url.Values
+		expectedFilter *querier.FQDNCacheFilter
+		expectedStatus int
+	}{
+		{
+			name:           "Empty query",
+			queryParams:    url.Values{},
+			expectedFilter: nil,
+			expectedStatus: http.StatusOK, // No HTTP error
+		},
+		{
+			name: "Valid regex domain",
+			queryParams: url.Values{
+				"domain": {"^example\\.com$"},
+			},
+			expectedFilter: &querier.FQDNCacheFilter{Domain: "^example\\.com$"},
+			expectedStatus: http.StatusOK, // No HTTP error
+		},
+		{
+			name: "Invalid regex domain",
+			queryParams: url.Values{
+				"domain": {"[invalid("},
+			},
+			expectedFilter: &querier.FQDNCacheFilter{Domain: "[invalid("}, // Should still return filter, despite error
+			expectedStatus: http.StatusPreconditionFailed,                 // HTTP error expected
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			recorder := httptest.NewRecorder()
+			result := newFilterFromURLQuery(recorder, tt.queryParams)
+
+			assert.Equal(t, tt.expectedFilter, result)
+			assert.Equal(t, tt.expectedStatus, recorder.Code)
+
+			if tt.expectedStatus != http.StatusOK {
+				require.Contains(t, recorder.Body.String(), "Regex formatted incorrectly to parse")
+			}
+		})
+	}
+}

pkg/agent/controller/networkpolicy/networkpolicy_controller.go

@@ -543,15 +543,10 @@ func NewNetworkPolicyController(antreaClientGetter client.AntreaClientProvider,
 func (c *Controller) GetFQDNCache(fqdnFilter *querier.FQDNCacheFilter) []types.DnsCacheEntry {
 	cacheEntryList := []types.DnsCacheEntry{}
 	var pattern *regexp.Regexp
-	var err error
 	if fqdnFilter != nil {
 		// have to convert human readable regex, i.e. *.example.com into regex that can be used
 		regexPattern := "^" + strings.ReplaceAll(regexp.QuoteMeta(fqdnFilter.Domain), `\*`, ".*") + "$"
-		pattern, err = regexp.Compile(regexPattern)
-		if err != nil {
-			// this pattern will match no strings if there is an error with the regex formatting or usage with the user specified --domain flag
-			pattern = regexp.MustCompile(`a\A`)
-		}
+		pattern, _ = regexp.Compile(regexPattern)
 	}
 	for fqdn, dnsMeta := range c.fqdnController.dnsEntryCache {
 		for _, ipWithExpiration := range dnsMeta.responseIPs {