log real ip of requests from ssh (#21216)

Partially fix #21213.

This PR will get client IP address from SSH_CONNECTION env which should
be the first field of that. And deliver it to the internal API so Gitea
routers could record the real IP from SSH requests.

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: zeripath <art27@cantab.net>

modules/private/internal.go

 	"fmt"
 	"net"
 	"net/http"
+	"os"
+	"strings"
 
 	"code.gitea.io/gitea/modules/httplib"
 	"code.gitea.io/gitea/modules/json"
 	"code.gitea.io/gitea/modules/setting"
 )
 
-func newRequest(ctx context.Context, url, method string) *httplib.Request {
+func newRequest(ctx context.Context, url, method, sourceIP string) *httplib.Request {
 	if setting.InternalToken == "" {
 		log.Fatal(`The INTERNAL_TOKEN setting is missing from the configuration file: %q.
 Ensure you are running in the correct environment or set the correct configuration file with -c.`, setting.CustomConf)
 	}
 	return httplib.NewRequest(url, method).
 		SetContext(ctx).
+		Header("X-Real-IP", sourceIP).
 		Header("Authorization", fmt.Sprintf("Bearer %s", setting.InternalToken))
 }
 
 	return &res
 }
 
+func getClientIP() string {
+	sshConnEnv := strings.TrimSpace(os.Getenv("SSH_CONNECTION"))
+	if len(sshConnEnv) == 0 {
+		return "127.0.0.1"
+	}
+	return strings.Fields(sshConnEnv)[0]
+}
+
 func newInternalRequest(ctx context.Context, url, method string) *httplib.Request {
-	req := newRequest(ctx, url, method).SetTLSClientConfig(&tls.Config{
+	req := newRequest(ctx, url, method, getClientIP()).SetTLSClientConfig(&tls.Config{
 		InsecureSkipVerify: true,
 		ServerName:         setting.Domain,
 	})

routers/private/internal.go

 	"code.gitea.io/gitea/modules/web"
 
 	"gitea.com/go-chi/binding"
+	chi_middleware "github.com/go-chi/chi/v5/middleware"
 )
 
 // CheckInternalToken check internal token is set
 	r := web.NewRoute()
 	r.Use(context.PrivateContexter())
 	r.Use(CheckInternalToken)
+	// Log the real ip address of the request from SSH is really helpful for diagnosing sometimes.
+	// Since internal API will be sent only from Gitea sub commands and it's under control (checked by InternalToken), we can trust the headers.
+	r.Use(chi_middleware.RealIP)
 
 	r.Post("/ssh/authorized_keys", AuthorizedPublicKeyByContent)
 	r.Post("/ssh/{id}/update/{repoid}", UpdatePublicKeyInRepo)