qga: Better mapping of SEEK_* in guest-file-seek

Exposing OS-specific SEEK_ constants in our qapi was a mistake
(if the host has SEEK_CUR as 1, but the guest has it as 2, then
the semantics are unclear what should happen); if we had a time
machine, we would instead expose only a symbolic enum.  It's too
late to change the fact that we have an integer in qapi, but we
can at least document what mapping we want to enforce for all
qga clients (and luckily, it happens to be the mapping that both
Linux and Windows use); then fix the code to match that mapping.
It also helps us filter out unsupported SEEK_DATA and SEEK_HOLE.

In the future, we may wish to move our QGA_SEEK_* constants into
qga/qapi-schema.json, along with updating the schema to take an
alternate type (either the integer, or the string value of the
enum name) - but that's too much risk during hard freeze.

Signed-off-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index cf1d7ec8c0c2c5890b478c359254bfe3bd72ba6c..c2ff97021ff55c31a6f38f31bf6465f736a4999f 100644 (file)
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -553,17 +553,34 @@ GuestFileWrite *qmp_guest_file_write(int64_t handle, const char *buf_b64,
 }
 
 struct GuestFileSeek *qmp_guest_file_seek(int64_t handle, int64_t offset,
-                                          int64_t whence, Error **errp)
+                                          int64_t whence_code, Error **errp)
 {
     GuestFileHandle *gfh = guest_file_handle_find(handle, errp);
     GuestFileSeek *seek_data = NULL;
     FILE *fh;
     int ret;
+    int whence;
 
     if (!gfh) {
         return NULL;
     }
 
+    /* We stupidly exposed 'whence':'int' in our qapi */
+    switch (whence_code) {
+    case QGA_SEEK_SET:
+        whence = SEEK_SET;
+        break;
+    case QGA_SEEK_CUR:
+        whence = SEEK_CUR;
+        break;
+    case QGA_SEEK_END:
+        whence = SEEK_END;
+        break;
+    default:
+        error_setg(errp, "invalid whence code %"PRId64, whence_code);
+        return NULL;
+    }
+
     fh = gfh->fh;
     ret = fseek(fh, offset, whence);
     if (ret == -1) {

diff --git a/qga/commands-win32.c b/qga/commands-win32.c
index 41f6dd9feda1cd07fbf46c75f0ee550d4c5aa445..0654fe4fe70c7c3e971a7de2f2f72edd9bb67e83 100644 (file)
--- a/qga/commands-win32.c
+++ b/qga/commands-win32.c
@@ -382,7 +382,7 @@ done:
 }
 
 GuestFileSeek *qmp_guest_file_seek(int64_t handle, int64_t offset,
-                                   int64_t whence, Error **errp)
+                                   int64_t whence_code, Error **errp)
 {
     GuestFileHandle *gfh;
     GuestFileSeek *seek_data;
@@ -390,11 +390,29 @@ GuestFileSeek *qmp_guest_file_seek(int64_t handle, int64_t offset,
     LARGE_INTEGER new_pos, off_pos;
     off_pos.QuadPart = offset;
     BOOL res;
+    int whence;
+
     gfh = guest_file_handle_find(handle, errp);
     if (!gfh) {
         return NULL;
     }
 
+    /* We stupidly exposed 'whence':'int' in our qapi */
+    switch (whence_code) {
+    case QGA_SEEK_SET:
+        whence = SEEK_SET;
+        break;
+    case QGA_SEEK_CUR:
+        whence = SEEK_CUR;
+        break;
+    case QGA_SEEK_END:
+        whence = SEEK_END;
+        break;
+    default:
+        error_setg(errp, "invalid whence code %"PRId64, whence_code);
+        return NULL;
+    }
+
     fh = gfh->fh;
     res = SetFilePointerEx(fh, off_pos, &new_pos, whence);
     if (!res) {

diff --git a/qga/guest-agent-core.h b/qga/guest-agent-core.h
index e92c6abafbf5d806c03cdbe220b4b3191373c0c4..238dc6b08df793c3a71cc78308805beb96714157 100644 (file)
--- a/qga/guest-agent-core.h
+++ b/qga/guest-agent-core.h
@@ -15,6 +15,13 @@
 
 #define QGA_READ_COUNT_DEFAULT 4096
 
+/* Mapping of whence codes used by guest-file-seek. */
+enum {
+    QGA_SEEK_SET = 0,
+    QGA_SEEK_CUR = 1,
+    QGA_SEEK_END = 2,
+};
+
 typedef struct GAState GAState;
 typedef struct GACommandState GACommandState;
 extern GAState *ga_state;

diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
index 78362e071d18de1f04f3b5730d8a32dcb46ee74c..01c9ee48d86a35dd4db1c557d6896160d118d910 100644 (file)
--- a/qga/qapi-schema.json
+++ b/qga/qapi-schema.json
@@ -318,13 +318,13 @@
 #
 # Seek to a position in the file, as with fseek(), and return the
 # current file position afterward. Also encapsulates ftell()'s
-# functionality, just Set offset=0, whence=SEEK_CUR.
+# functionality, with offset=0 and whence=1.
 #
 # @handle: filehandle returned by guest-file-open
 #
 # @offset: bytes to skip over in the file stream
 #
-# @whence: SEEK_SET, SEEK_CUR, or SEEK_END, as with fseek()
+# @whence: 0 for SEEK_SET, 1 for SEEK_CUR, or 2 for SEEK_END
 #
 # Returns: @GuestFileSeek on success.
 #

diff --git a/tests/test-qga.c b/tests/test-qga.c
index 3b99d9d5ca3b3c0655226e06a626d5989aeca90a..e6a84d17f0626e0521ce5e252be0c393fb438dfb 100644 (file)
--- a/tests/test-qga.c
+++ b/tests/test-qga.c
@@ -13,6 +13,7 @@
 
 #include "libqtest.h"
 #include "config-host.h"
+#include "qga/guest-agent-core.h"
 
 typedef struct {
     char *test_dir;
@@ -457,7 +458,7 @@ static void test_qga_file_ops(gconstpointer fix)
     cmd = g_strdup_printf("{'execute': 'guest-file-seek',"
                           " 'arguments': { 'handle': %" PRId64 ", "
                           " 'offset': %d, 'whence': %d } }",
-                          id, 6, SEEK_SET);
+                          id, 6, QGA_SEEK_SET);
     ret = qmp_fd(fixture->fd, cmd);
     qmp_assert_no_error(ret);
     val = qdict_get_qdict(ret, "return");
@@ -550,7 +551,7 @@ static void test_qga_file_write_read(gconstpointer fix)
     cmd = g_strdup_printf("{'execute': 'guest-file-seek',"
                           " 'arguments': { 'handle': %" PRId64 ", "
                           " 'offset': %d, 'whence': %d } }",
-                          id, 0, SEEK_SET);
+                          id, 0, QGA_SEEK_SET);
     ret = qmp_fd(fixture->fd, cmd);
     qmp_assert_no_error(ret);
     val = qdict_get_qdict(ret, "return");