Add support for Kubernetes Gateway API RequestHeaderModifier filter

Co-authored-by: Baptiste Mayelle <baptiste.mayelle@traefik.io>

pkg/middlewares/headermodifier/request_header_modifier.go

@@ -0,0 +1,56 @@
+package headermodifier
+
+import (
+	"context"
+	"net/http"
+
+	"github.com/traefik/traefik/v3/pkg/config/dynamic"
+	"github.com/traefik/traefik/v3/pkg/middlewares"
+	"go.opentelemetry.io/otel/trace"
+)
+
+const typeName = "RequestHeaderModifier"
+
+// requestHeaderModifier is a middleware used to modify the headers of an HTTP request.
+type requestHeaderModifier struct {
+	next http.Handler
+	name string
+
+	set    map[string]string
+	add    map[string]string
+	remove []string
+}
+
+// NewRequestHeaderModifier creates a new request header modifier middleware.
+func NewRequestHeaderModifier(ctx context.Context, next http.Handler, config dynamic.RequestHeaderModifier, name string) (http.Handler, error) {
+	logger := middlewares.GetLogger(ctx, name, typeName)
+	logger.Debug().Msg("Creating middleware")
+
+	return &requestHeaderModifier{
+		next:   next,
+		name:   name,
+		set:    config.Set,
+		add:    config.Add,
+		remove: config.Remove,
+	}, nil
+}
+
+func (r *requestHeaderModifier) GetTracingInformation() (string, string, trace.SpanKind) {
+	return r.name, typeName, trace.SpanKindUnspecified
+}
+
+func (r *requestHeaderModifier) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
+	for headerName, headerValue := range r.set {
+		req.Header.Set(headerName, headerValue)
+	}
+
+	for headerName, headerValue := range r.add {
+		req.Header.Add(headerName, headerValue)
+	}
+
+	for _, headerName := range r.remove {
+		req.Header.Del(headerName)
+	}
+
+	r.next.ServeHTTP(rw, req)
+}

pkg/middlewares/headermodifier/request_header_modifier_test.go

@@ -0,0 +1,121 @@
+package headermodifier
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/traefik/traefik/v3/pkg/config/dynamic"
+	"github.com/traefik/traefik/v3/pkg/testhelpers"
+)
+
+func TestRequestHeaderModifier(t *testing.T) {
+	testCases := []struct {
+		desc            string
+		config          dynamic.RequestHeaderModifier
+		requestHeaders  http.Header
+		expectedHeaders http.Header
+	}{
+		{
+			desc:            "no config",
+			config:          dynamic.RequestHeaderModifier{},
+			expectedHeaders: map[string][]string{},
+		},
+		{
+			desc: "set header",
+			config: dynamic.RequestHeaderModifier{
+				Set: map[string]string{"Foo": "Bar"},
+			},
+			expectedHeaders: map[string][]string{"Foo": {"Bar"}},
+		},
+		{
+			desc: "set header with existing headers",
+			config: dynamic.RequestHeaderModifier{
+				Set: map[string]string{"Foo": "Bar"},
+			},
+			requestHeaders:  map[string][]string{"Foo": {"Baz"}, "Bar": {"Foo"}},
+			expectedHeaders: map[string][]string{"Foo": {"Bar"}, "Bar": {"Foo"}},
+		},
+		{
+			desc: "set multiple headers with existing headers",
+			config: dynamic.RequestHeaderModifier{
+				Set: map[string]string{"Foo": "Bar", "Bar": "Foo"},
+			},
+			requestHeaders:  map[string][]string{"Foo": {"Baz"}, "Bar": {"Foobar"}},
+			expectedHeaders: map[string][]string{"Foo": {"Bar"}, "Bar": {"Foo"}},
+		},
+		{
+			desc: "add header",
+			config: dynamic.RequestHeaderModifier{
+				Add: map[string]string{"Foo": "Bar"},
+			},
+			expectedHeaders: map[string][]string{"Foo": {"Bar"}},
+		},
+		{
+			desc: "add header with existing headers",
+			config: dynamic.RequestHeaderModifier{
+				Add: map[string]string{"Foo": "Bar"},
+			},
+			requestHeaders:  map[string][]string{"Foo": {"Baz"}, "Bar": {"Foo"}},
+			expectedHeaders: map[string][]string{"Foo": {"Baz", "Bar"}, "Bar": {"Foo"}},
+		},
+		{
+			desc: "add multiple headers with existing headers",
+			config: dynamic.RequestHeaderModifier{
+				Add: map[string]string{"Foo": "Bar", "Bar": "Foo"},
+			},
+			requestHeaders:  map[string][]string{"Foo": {"Baz"}, "Bar": {"Foobar"}},
+			expectedHeaders: map[string][]string{"Foo": {"Baz", "Bar"}, "Bar": {"Foobar", "Foo"}},
+		},
+		{
+			desc: "remove header",
+			config: dynamic.RequestHeaderModifier{
+				Remove: []string{"Foo"},
+			},
+			expectedHeaders: map[string][]string{},
+		},
+		{
+			desc: "remove header with existing headers",
+			config: dynamic.RequestHeaderModifier{
+				Remove: []string{"Foo"},
+			},
+			requestHeaders:  map[string][]string{"Foo": {"Baz"}, "Bar": {"Foo"}},
+			expectedHeaders: map[string][]string{"Bar": {"Foo"}},
+		},
+		{
+			desc: "remove multiple headers with existing headers",
+			config: dynamic.RequestHeaderModifier{
+				Remove: []string{"Foo", "Bar"},
+			},
+			requestHeaders:  map[string][]string{"Foo": {"Bar"}, "Bar": {"Foo"}, "Baz": {"Bar"}},
+			expectedHeaders: map[string][]string{"Baz": {"Bar"}},
+		},
+	}
+
+	for _, test := range testCases {
+		t.Run(test.desc, func(t *testing.T) {
+			t.Parallel()
+
+			var gotHeaders http.Header
+			next := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				gotHeaders = r.Header
+			})
+
+			handler, err := NewRequestHeaderModifier(context.Background(), next, test.config, "foo-request-header-modifier")
+			require.NoError(t, err)
+
+			req := testhelpers.MustNewRequest(http.MethodGet, "http://localhost", nil)
+			if test.requestHeaders != nil {
+				req.Header = test.requestHeaders
+			}
+
+			resp := httptest.NewRecorder()
+			handler.ServeHTTP(resp, req)
+
+			assert.Equal(t, test.expectedHeaders, gotHeaders)
+		})
+	}
+}