rpc/log: return first error always

Use shared first error buffer to return correct
first error in rpc.

Fixes: #338

Signed-off-by: Ivan Pravdin <ipravdin.official@gmail.com>

criu/cr-service.c

@@ -895,6 +895,11 @@ static int check(int sk, CriuOpts *req)
 
 	resp.type = CRIU_REQ_TYPE__CHECK;
 
+	if (log_keep_err()) {
+		pr_perror("Can't tune log");
+		goto out;
+	}
+
 	pid = fork();
 	if (pid < 0) {
 		pr_perror("Can't fork");
@@ -919,6 +924,7 @@ static int check(int sk, CriuOpts *req)
 
 	resp.success = true;
 out:
+	set_resp_err(&resp);
 	return send_criu_msg(sk, &resp);
 }
 
@@ -927,6 +933,11 @@ static int pre_dump_using_req(int sk, CriuOpts *req, bool single)
 	int pid, status;
 	bool success = false;
 
+	if (log_keep_err()) {
+		pr_perror("Can't tune log");
+		goto out;
+	}
+
 	pid = fork();
 	if (pid < 0) {
 		pr_perror("Can't fork");
@@ -1005,6 +1016,11 @@ static int start_page_server_req(int sk, CriuOpts *req, bool daemon_mode)
 	CriuPageServerInfo ps = CRIU_PAGE_SERVER_INFO__INIT;
 	struct ps_info info;
 
+	if (log_keep_err()) {
+		pr_perror("Can't tune log");
+		goto out;
+	}
+
 	if (pipe(start_pipe)) {
 		pr_perror("No start pipe");
 		goto out;
@@ -1078,6 +1094,7 @@ static int start_page_server_req(int sk, CriuOpts *req, bool daemon_mode)
 out:
 	resp.type = CRIU_REQ_TYPE__PAGE_SERVER;
 	resp.success = success;
+	set_resp_err(&resp);
 	return send_criu_msg(sk, &resp);
 }
 
@@ -1252,6 +1269,11 @@ static int handle_cpuinfo(int sk, CriuReq *msg)
 	bool success = false;
 	int pid, status;
 
+	if (log_keep_err()) {
+		pr_perror("Can't tune log");
+		goto out;
+	}
+
 	pid = fork();
 	if (pid < 0) {
 		pr_perror("Can't fork");
@@ -1301,7 +1323,7 @@ static int handle_cpuinfo(int sk, CriuReq *msg)
 out:
 	resp.type = msg->type;
 	resp.success = success;
-
+	set_resp_err(&resp);
 	return send_criu_msg(sk, &resp);
 }
 

criu/log.c

@@ -10,6 +10,7 @@
 #include <sys/time.h>
 #include <sys/resource.h>
 #include <sys/utsname.h>
+#include <sys/mman.h>
 
 #include <fcntl.h>
 
@@ -114,6 +115,9 @@ static struct str_and_lock *first_err;
 
 int log_keep_err(void)
 {
+	if (first_err)
+		return 0;
+
 	first_err = shmalloc(sizeof(struct str_and_lock));
 	if (first_err == NULL)
 		return -1;

test/others/rpc/errno.py

@@ -40,7 +40,7 @@ class test:
         resp.ParseFromString(self.s.recv(self._MAX_MSG_SIZE))
         return resp
 
-    def check_resp(self, resp, typ, err):
+    def check_resp(self, resp, typ, err, errmsg = None):
         if resp.type != typ:
             raise Exception('Unexpected response type ' + str(resp.type))
 
@@ -49,6 +49,9 @@ class test:
 
         if err and resp.cr_errno != err:
             raise Exception('Unexpected cr_errno ' + str(resp.cr_errno))
+        
+        if errmsg and errmsg not in resp.cr_errmsg:
+            raise Exception('Unexpected cr_msg \'' + str(resp.cr_errmsg) + '\'')
 
     def no_process(self):
         print('Try to dump unexisting process')
@@ -131,12 +134,29 @@ class test:
         self.check_resp(resp, rpc.EMPTY, None)
 
         print('Success')
+        
+    def child_first_err(self):
+        print('Receive correct first error message')
+
+        req = self.get_base_req()
+        req.type = rpc.CHECK
+        
+        # mntns_compat_mode options is only allowed on restore
+        req.opts.mntns_compat_mode = True
+
+        self.send_req(req)
+        resp = self.recv_resp()
+
+        self.check_resp(resp, rpc.CHECK, None, "Option --mntns-compat-mode is only valid on restore\n")
+
+        print('Success')
 
     def run(self):
         self.no_process()
         self.process_exists()
         self.bad_options()
         self.bad_request()
+        self.child_first_err()
 
 
 t = test()