[PATCH 5/6] virprocess: Passthru error from virProcessRunInForkHelper

[Michal Privoznik <mprivozn@xxxxxxxxxx>]

When running a function in a forked child, so far the only thing
we could report is exit status of the child and the error
message. However, it may be beneficial to the caller to know the
actual error that happened in the child.

Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
---
 build-aux/syntax-check.mk |  2 +-
 src/util/virprocess.c     | 51 ++++++++++++++++++++++++++++++++++++---
 tests/commandtest.c       | 43 +++++++++++++++++++++++++++++++++
 3 files changed, 91 insertions(+), 5 deletions(-)

diff --git a/build-aux/syntax-check.mk b/build-aux/syntax-check.mk
index 3020921be8..2a38c03ba9 100644
--- a/build-aux/syntax-check.mk
+++ b/build-aux/syntax-check.mk
@@ -1987,7 +1987,7 @@ exclude_file_name_regexp--sc_flags_usage = \
 exclude_file_name_regexp--sc_libvirt_unmarked_diagnostics = \
   ^(src/rpc/gendispatch\.pl$$|tests/)
 
-exclude_file_name_regexp--sc_po_check = ^(docs/|src/rpc/gendispatch\.pl$$)
+exclude_file_name_regexp--sc_po_check = ^(docs/|src/rpc/gendispatch\.pl$$|tests/commandtest.c$$)
 
 exclude_file_name_regexp--sc_prohibit_VIR_ERR_NO_MEMORY = \
   ^(build-aux/syntax-check\.mk|include/libvirt/virterror\.h|src/remote/remote_daemon_dispatch\.c|src/util/virerror\.c|docs/internals/oomtesting\.html\.in)$$
diff --git a/src/util/virprocess.c b/src/util/virprocess.c
index 24135070b7..e8674402f9 100644
--- a/src/util/virprocess.c
+++ b/src/util/virprocess.c
@@ -1126,6 +1126,23 @@ virProcessRunInMountNamespace(pid_t pid G_GNUC_UNUSED,
 
 
 #ifndef WIN32
+typedef struct {
+    int code;
+    int domain;
+    char message[VIR_ERROR_MAX_LENGTH];
+    virErrorLevel level;
+    char str1[VIR_ERROR_MAX_LENGTH];
+    char str2[VIR_ERROR_MAX_LENGTH];
+    /* str3 doesn't seem to be used. Ignore it. */
+    int int1;
+    int int2;
+} errorData;
+
+typedef union {
+    errorData data;
+    char bindata[sizeof(errorData)];
+} errorDataBin;
+
 static int
 virProcessRunInForkHelper(int errfd,
                           pid_t ppid,
@@ -1134,9 +1151,19 @@ virProcessRunInForkHelper(int errfd,
 {
     if (cb(ppid, opaque) < 0) {
         virErrorPtr err = virGetLastError();
+        errorDataBin bin = { 0 };
+
         if (err) {
-            size_t len = strlen(err->message) + 1;
-            ignore_value(safewrite(errfd, err->message, len));
+            bin.data.code = err->code;
+            bin.data.domain = err->domain;
+            ignore_value(virStrcpy(bin.data.message, err->message, sizeof(bin.data.message)));
+            bin.data.level = err->level;
+            ignore_value(virStrcpy(bin.data.str1, err->str1, sizeof(bin.data.str1)));
+            ignore_value(virStrcpy(bin.data.str2, err->str2, sizeof(bin.data.str2)));
+            bin.data.int1 = err->int1;
+            bin.data.int2 = err->int2;
+
+            ignore_value(safewrite(errfd, bin.bindata, sizeof(bin)));
         }
 
         return -1;
@@ -1188,16 +1215,32 @@ virProcessRunInFork(virProcessForkCallback cb,
     } else {
         int status;
         g_autofree char *buf = NULL;
+        errorDataBin bin;
+        int nread;
 
         VIR_FORCE_CLOSE(errfd[1]);
-        ignore_value(virFileReadHeaderFD(errfd[0], 1024, &buf));
+        nread = virFileReadHeaderFD(errfd[0], sizeof(bin), &buf);
         ret = virProcessWait(child, &status, false);
         if (ret == 0) {
             ret = status == EXIT_CANCELED ? -1 : status;
             if (ret) {
                 virReportError(VIR_ERR_INTERNAL_ERROR,
                                _("child reported (status=%d): %s"),
-                               status, NULLSTR(buf));
+                               status, NULLSTR(bin.data.message));
+
+                if (nread == sizeof(bin)) {
+                    memcpy(bin.bindata, buf, sizeof(bin));
+                    virRaiseErrorFull(__FILE__, __FUNCTION__, __LINE__,
+                                      bin.data.domain,
+                                      bin.data.code,
+                                      bin.data.level,
+                                      bin.data.str1,
+                                      bin.data.str2,
+                                      NULL,
+                                      bin.data.int1,
+                                      bin.data.int2,
+                                      "%s", bin.data.message);
+                }
             }
         }
     }
diff --git a/tests/commandtest.c b/tests/commandtest.c
index a64aa9ad33..f4a2c67c05 100644
--- a/tests/commandtest.c
+++ b/tests/commandtest.c
@@ -1257,6 +1257,48 @@ static int test27(const void *unused G_GNUC_UNUSED)
 }
 
 
+static int
+test28Callback(pid_t pid G_GNUC_UNUSED,
+               void *opaque G_GNUC_UNUSED)
+{
+    virReportSystemError(ENODATA, "%s", "some error message");
+    return -1;
+}
+
+
+static int
+test28(const void *unused G_GNUC_UNUSED)
+{
+    /* Not strictly a virCommand test, but this is the easiest place
+     * to test this lower-level interface. */
+    virErrorPtr err;
+
+    if (virProcessRunInFork(test28Callback, NULL) != -1) {
+        fprintf(stderr, "virProcessRunInFork did not fail\n");
+        return -1;
+    }
+
+    if (!(err = virGetLastError())) {
+        fprintf(stderr, "Expected error but got nothing\n");
+        return -1;
+    }
+
+    if (!(err->code == VIR_ERR_SYSTEM_ERROR &&
+          err->domain == 0 &&
+          STREQ(err->message, "some error message: No data available") &&
+          err->level == VIR_ERR_ERROR &&
+          STREQ(err->str1, "%s") &&
+          STREQ(err->str2, "some error message: No data available") &&
+          err->int1 == ENODATA &&
+          err->int2 == -1)) {
+        fprintf(stderr, "Unexpected error object\n");
+        return -1;
+    }
+
+    return 0;
+}
+
+
 static int
 mymain(void)
 {
@@ -1354,6 +1396,7 @@ mymain(void)
     DO_TEST(test25);
     DO_TEST(test26);
     DO_TEST(test27);
+    DO_TEST(test28);
 
     return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
 }
-- 
2.24.1