feat: connectrpc realip interceptor (#1728)

Depends On: #1715 

This is needed because we can't use the
[realip](https://github.com/grpc-ecosystem/go-grpc-middleware/tree/main/interceptors/realip)
interceptor with connectrpc.

---------

Co-authored-by: Jake Van Vorhis <[email protected]>

service/internal/server/realip/realip.go

@@ -0,0 +1,62 @@
+package realip
+
+import (
+	"context"
+	"net"
+	"net/http"
+	"net/netip"
+	"strings"
+
+	"connectrpc.com/connect"
+)
+
+const (
+	XRealIP       = "X-Real-IP"
+	XForwardedFor = "X-Forwarded-For"
+	TrueClientIP  = "True-Client-Ip"
+)
+
+type clientIP struct{}
+
+func ConnectRealIPUnaryInterceptor() connect.UnaryInterceptorFunc {
+	interceptor := func(next connect.UnaryFunc) connect.UnaryFunc {
+		return connect.UnaryFunc(func(
+			ctx context.Context,
+			req connect.AnyRequest,
+		) (connect.AnyResponse, error) {
+			ip := getIP(ctx, req.Peer(), req.Header())
+
+			ctx = context.WithValue(ctx, clientIP{}, ip)
+
+			return next(ctx, req)
+		})
+	}
+	return connect.UnaryInterceptorFunc(interceptor)
+}
+
+func getIP(_ context.Context, peer connect.Peer, headers http.Header) net.IP {
+	for _, header := range []string{XRealIP, XForwardedFor, TrueClientIP} {
+		if ip := headers.Get(header); ip != "" {
+			ips := strings.Split(ip, ",")
+			if ips[0] == "" || net.ParseIP(ips[0]) == nil {
+				continue
+			}
+			return net.ParseIP(ips[0])
+		}
+	}
+
+	ip, err := netip.ParseAddrPort(peer.Addr)
+	if err != nil {
+		return net.IP{}
+	}
+
+	return net.IP(ip.Addr().AsSlice())
+}
+
+func FromContext(ctx context.Context) net.IP {
+	ip, ok := ctx.Value(clientIP{}).(net.IP)
+	if !ok {
+		return net.IP{}
+	}
+	return ip
+}

service/internal/server/realip/realip_test.go

@@ -0,0 +1,57 @@
+package realip
+
+import (
+	"context"
+	"net/http"
+	"testing"
+
+	"connectrpc.com/connect"
+	"github.com/stretchr/testify/suite"
+)
+
+type RealIPTestSuite struct {
+	suite.Suite
+}
+
+func TestRealIPSuite(t *testing.T) {
+	suite.Run(t, new(RealIPTestSuite))
+}
+
+func (s *RealIPTestSuite) Test_getIP_from_x_real_ip_header() {
+	ip := "1.1.1.1"
+	peer := connect.Peer{}
+
+	headers := http.Header{}
+	headers.Add(XRealIP, ip)
+	foundIP := getIP(context.Background(), peer, headers)
+	s.Equal(ip, foundIP.String())
+}
+
+func (s *RealIPTestSuite) Test_getIP_from_x_forwarded_for_header() {
+	ip := "1.1.1.1"
+	peer := connect.Peer{}
+
+	headers := http.Header{}
+	headers.Add(XForwardedFor, ip)
+	foundIP := getIP(context.Background(), peer, headers)
+	s.Equal(ip, foundIP.String())
+}
+
+func (s *RealIPTestSuite) Test_getIP_from_true_client_ip_header() {
+	ip := "1.1.1.1"
+	peer := connect.Peer{}
+
+	headers := http.Header{}
+	headers.Add(TrueClientIP, ip)
+	foundIP := getIP(context.Background(), peer, headers)
+	s.Equal(ip, foundIP.String())
+}
+
+func (s *RealIPTestSuite) Test_getIP_from_peer() {
+	ip := "1.1.1.1"
+	peer := connect.Peer{Addr: ip + ":1234"}
+
+	headers := http.Header{}
+	foundIP := getIP(context.Background(), peer, headers)
+	s.Equal(ip, foundIP.String())
+}