dumpcap: Make capture child logging work

Distinguish log messages from SP_ERROR_MSG; log messages don't
necessarily represent a failure, and they have a level. This
doesn't affect logging while capturing much, as SP_ERROR_MSGs
are just printed to the console, but it makes it possible to log
while retrieving interface information or the stats, where SP_ERROR_MSG
indicates that the command failed.

capture/capture_sync.c

@@ -218,6 +218,23 @@ sync_pipe_add_arg(char **args, int *argc, const char *arg)
     return args;
 }
 
+/* Take a buffer from an SP_LOG_MSG from dumpcap and send it to our
+ * current logger. Keep this in sync with the format used in
+ * dumpcap_log_writer. (We might want to do more proper serialization
+ * of more than just the log level.)
+ */
+static void
+sync_pipe_handle_log_msg(const char *buffer) {
+    const char *log_msg = NULL;
+    const char* end;
+    uint32_t level = 0;
+
+    if (ws_strtou32(buffer, &end, &level) && end[0] == ':') {
+        log_msg = end + 1;
+    }
+    ws_log(LOG_DOMAIN_CAPCHILD, level, "%s", log_msg);
+}
+
 /* Initialize an argument list and add dumpcap to it. */
 static char **
 init_pipe_args(int *argc) {
@@ -1140,6 +1157,13 @@ sync_pipe_run_command_actual(char **argv, char **data, char **primary_msg,
         *data = NULL;
         break;
 
+    case SP_LOG_MSG:
+        /*
+         * Log from dumpcap; pass to our log
+         */
+        sync_pipe_handle_log_msg(buffer);
+        break;
+
     case SP_SUCCESS:
         /* read the output from the command */
         data_buf = g_string_new("");
@@ -1566,6 +1590,13 @@ sync_interface_stats_open(int *data_read_fd, ws_process_id *fork_child, char **d
             }
             return ret;
 
+        case SP_LOG_MSG:
+            /*
+             * Log from dumpcap; pass to our log
+             */
+            sync_pipe_handle_log_msg(buffer);
+            break;
+
         case SP_IFACE_LIST:
             /*
              * Dumpcap giving us the interface list
@@ -1910,6 +1941,12 @@ sync_pipe_input_cb(GIOChannel *pipe_io, capture_session *cap_session)
         /* the capture child will close the sync_pipe, nothing to do for now */
         /* (an error message doesn't mean we have to stop capturing) */
         break;
+    case SP_LOG_MSG:
+        /*
+         * Log from dumpcap; pass to our log
+         */
+        sync_pipe_handle_log_msg(buffer);
+        break;
     case SP_BAD_FILTER: {
         const char *message=NULL;
         uint32_t indx = 0;

dumpcap.c

@@ -5980,18 +5980,36 @@ dumpcap_log_writer(const char *domain, enum ws_log_level level,
                                     const char *user_format, va_list user_ap,
                                     void *user_data _U_)
 {
-    /* DEBUG & INFO msgs (if we're debugging today)                 */
-#if defined(DEBUG_DUMPCAP) || defined(DEBUG_CHILD_DUMPCAP)
-    if (level <= LOG_LEVEL_INFO && ws_log_msg_is_active(domain, level)) {
-#ifdef DEBUG_DUMPCAP
+    if (ws_log_msg_is_active(domain, level)) {
+        /* log messages go to stderr or    */
+        /* to parent especially formatted if dumpcap running as child. */
 #ifdef DEBUG_CHILD_DUMPCAP
         va_list user_ap_copy;
         va_copy(user_ap_copy, user_ap);
 #endif
         if (capture_child) {
-            gchar *msg = ws_strdup_vprintf(user_format, user_ap);
-            sync_pipe_write_errmsgs_to_parent(sync_pipe_fd, msg, "");
-            g_free(msg);
+            /* Format the log mesage as the numeric level, followed
+             * by a colon and then a string matching the standard log
+             * string. In the future perhaps we serialize file, line,
+             * and func (which can be NULL) instead.
+             */
+            GString *msg = g_string_new(NULL);
+            g_string_append_printf(msg, "%u:", level);
+            if (file != NULL) {
+                g_string_append_printf(msg, "%s", file);
+                if (line >= 0) {
+                    g_string_append_printf(msg, ":%ld", line);
+                }
+            }
+            g_string_append(msg, " --");
+            if (func != NULL) {
+                g_string_append_printf(msg, " %s():", func);
+            }
+            g_string_append_c(msg, ' ');
+            g_string_append_vprintf(msg, user_format, user_ap);
+
+            sync_pipe_write_string_msg(sync_pipe_fd, SP_LOG_MSG, msg->str);
+            g_string_free(msg, TRUE);
         } else {
             ws_log_console_writer(domain, level, file, line, func, mft, user_format, user_ap);
         }
@@ -5999,21 +6017,6 @@ dumpcap_log_writer(const char *domain, enum ws_log_level level,
         ws_log_file_writer(debug_log, domain, level, file, line, func, mft, user_format, user_ap_copy);
         va_end(user_ap_copy);
 #endif
-#elif defined(DEBUG_CHILD_DUMPCAP)
-        ws_log_file_writer(debug_log, domain, level, file, line, func, mft, user_format, user_ap);
-#endif
-        return;
-    }
-#endif
-
-    /* ERROR, CRITICAL, WARNING, MESSAGE messages goto stderr or    */
-    /*  to parent especially formatted if dumpcap running as child. */
-    if (capture_child) {
-        gchar *msg = ws_strdup_vprintf(user_format, user_ap);
-        sync_pipe_write_errmsgs_to_parent(sync_pipe_fd, msg, "");
-        g_free(msg);
-    } else if(ws_log_msg_is_active(domain, level)) {
-        ws_log_console_writer(domain, level, file, line, func, mft, user_format, user_ap);
     }
 }
 

sync_pipe.h

@@ -42,6 +42,7 @@
 #define SP_EXEC_FAILED  'X'     /* errno value for the exec failing */
 #define SP_FILE         'F'     /* the name of the recently opened file */
 #define SP_ERROR_MSG    'E'     /* error message */
+#define SP_LOG_MSG      'L'     /* log message */
 #define SP_BAD_FILTER   'B'     /* error message for bad capture filter */
 #define SP_PACKET_COUNT 'P'     /* count of packets captured since last message */
 #define SP_DROPS        'D'     /* count of packets dropped in capture */