[PATCH 23/28] libxl: dm user: Move user choice earlier, and fill in config

[Ian Jackson <ian.jackson@eu.citrix.com>]

Move the dm user defaulting from libxl__build_device_model_args_new
earlier in domain create.  We now do it just after the dm support
check has finished.

Convey the result to the dm args constructor in the b_info, ie in the
supplied config.  So, the application's supplied config is filled in
with the chosen user, as for other defaults.

Also:
 - slightly improve one of the warning messages
 - change the moved code to use `rc' (following CODING_STYLE)
   rather than `ret'
 - change the moved code to use `domid' rather than `guest_domid'
   like most of the rest of domain create
 - change the name of the (static) user selection function.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
CC: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---
v6: New patch
---
 tools/libxl/libxl_create.c |   84 ++++++++++++++++++++++++++++++++++++++++++++
 tools/libxl/libxl_dm.c     |   62 ++------------------------------
 2 files changed, 86 insertions(+), 60 deletions(-)

diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
index b41c6bd..be9bb7b 100644
--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -20,6 +20,8 @@
 #include "libxl_internal.h"
 #include "libxl_arch.h"
 
+#include <pwd.h>
+
 #include <xc_dom.h>
 #include <xenguest.h>
 #include <xen/hvm/hvm_info_table.h>
@@ -388,6 +390,83 @@ int libxl__domain_build_info_setdefault(libxl__gc *gc,
     return 0;
 }
 
+/* return 1 if the user was found, 0 if it was not, -1 on error */
+static int dm_runas_helper(libxl__gc *gc, const char *username)
+{
+    struct passwd pwd, *user = NULL;
+    char *buf = NULL;
+    long buf_size;
+    int ret;
+
+    buf_size = sysconf(_SC_GETPW_R_SIZE_MAX);
+    if (buf_size < 0) {
+        LOGE(ERROR, "sysconf(_SC_GETPW_R_SIZE_MAX) returned error %ld",
+                buf_size);
+        return ERROR_FAIL;
+    }
+
+    while (1) {
+        buf = libxl__realloc(gc, buf, buf_size);
+        ret = getpwnam_r(username, &pwd, buf, buf_size, &user);
+        if (ret == ERANGE) {
+            buf_size += 128;
+            continue;
+        }
+        if (ret != 0)
+            return ERROR_FAIL;
+        if (user != NULL)
+            return 1;
+        return 0;
+    }
+}
+
+static int domcreate_setdefault_dm_user(libxl__gc *gc,
+                                        libxl__domain_create_state *dcs)
+{
+    /* convenience aliases */
+    libxl_domain_config *const d_config = dcs->guest_config;
+    libxl_domain_build_info *const b_info = &d_config->b_info;
+    const uint32_t domid = dcs->guest_domid;
+
+    int rc;
+    const char *user;
+
+    if (b_info->device_model_user)
+        /* already set, good-oh */
+        return 0;
+
+    if (!(b_info->type == LIBXL_DOMAIN_TYPE_HVM &&
+          !libxl_defbool_val(b_info->device_model_stubdomain)))
+        /* we're not going to run it anyway */
+        return 0;
+
+    user = GCSPRINTF("%s%d", LIBXL_QEMU_USER_BASE, domid);
+
+    rc = dm_runas_helper(gc, user);
+    if (rc < 0) goto error;
+    if (rc > 0) goto found;
+
+    user = LIBXL_QEMU_USER_SHARED;
+    rc = dm_runas_helper(gc, user);
+    if (rc < 0) goto error;
+    if (rc > 0) {
+        LOG(WARN, "Could not find user %s%d, falling back to %s",
+            LIBXL_QEMU_USER_BASE, domid, LIBXL_QEMU_USER_SHARED);
+        goto found;
+    }
+
+    LOG(WARN, "Could not find user %s%d or %s, starting QEMU as root",
+        LIBXL_QEMU_USER_BASE, domid, LIBXL_QEMU_USER_SHARED);
+    user = "root";
+
+ found:
+    b_info->device_model_user = libxl__strdup(NOGC, user);
+    return 0;
+
+ error:
+    return rc;
+}
+
 static void init_console_info(libxl__gc *gc,
                              libxl__device_console *console,
                              int dev_num)
@@ -970,6 +1049,11 @@ static void domcreate_dm_support_checked(libxl__egc *egc,
 
     if (rc) goto out;
 
+    /* config defaults which depend on dm support etc. */
+
+    rc = domcreate_setdefault_dm_user(gc, dcs);
+    if (rc) goto out;
+
     dcs->bl.ao = ao;
     libxl_device_disk *bootdisk =
         d_config->num_disks > 0 ? &d_config->disks[0] : NULL;
diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index 8232981..5e1a6cf 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -21,8 +21,6 @@
 
 #include <xc_dom.h>
 #include <xen/hvm/e820.h>
-#include <sys/types.h>
-#include <pwd.h>
 
 static const char *libxl_tapif_script(libxl__gc *gc)
 {
@@ -728,36 +726,6 @@ libxl__detect_gfx_passthru_kind(libxl__gc *gc,
     return LIBXL_GFX_PASSTHRU_KIND_DEFAULT;
 }
 
-/* return 1 if the user was found, 0 if it was not, -1 on error */
-static int libxl__dm_runas_helper(libxl__gc *gc, const char *username)
-{
-    struct passwd pwd, *user = NULL;
-    char *buf = NULL;
-    long buf_size;
-    int ret;
-
-    buf_size = sysconf(_SC_GETPW_R_SIZE_MAX);
-    if (buf_size < 0) {
-        LOGE(ERROR, "sysconf(_SC_GETPW_R_SIZE_MAX) returned error %ld",
-                buf_size);
-        return ERROR_FAIL;
-    }
-
-    while (1) {
-        buf = libxl__realloc(gc, buf, buf_size);
-        ret = getpwnam_r(username, &pwd, buf, buf_size, &user);
-        if (ret == ERANGE) {
-            buf_size += 128;
-            continue;
-        }
-        if (ret != 0)
-            return ERROR_FAIL;
-        if (user != NULL)
-            return 1;
-        return 0;
-    }
-}
-
 static int libxl__build_device_model_args_new(libxl__gc *gc,
                                         const char *dm, int guest_domid,
                                         int emuid,
@@ -777,10 +745,9 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
     const char *keymap = dm_keymap(guest_config);
     char *machinearg;
     flexarray_t *dm_args, *dm_envs;
-    int i, connection, devid, ret;
+    int i, connection, devid;
     uint64_t ram_size;
     const char *path, *chardev;
-    char *user = NULL;
 
     dm_args = flexarray_make(gc, 16, 1);
     dm_envs = flexarray_make(gc, 16, 1);
@@ -1263,33 +1230,8 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
             break;
         }
 
-        if (b_info->device_model_user) {
-            user = b_info->device_model_user;
-            goto end_search;
-        }
-
-        user = GCSPRINTF("%s%d", LIBXL_QEMU_USER_BASE, guest_domid);
-        ret = libxl__dm_runas_helper(gc, user);
-        if (ret < 0)
-            return ret;
-        if (ret > 0)
-            goto end_search;
-
-        user = LIBXL_QEMU_USER_SHARED;
-        ret = libxl__dm_runas_helper(gc, user);
-        if (ret < 0)
-            return ret;
-        if (ret > 0) {
-            LOG(WARN, "Could not find user %s%d, falling back to %s",
-                    LIBXL_QEMU_USER_BASE, guest_domid, LIBXL_QEMU_USER_SHARED);
-            goto end_search;
-        }
-
-        user = NULL;
-        LOG(WARN, "Could not find user %s, starting QEMU as root",
-            LIBXL_QEMU_USER_SHARED);
+        char *const user = b_info->device_model_user;
 
-end_search:
         if (user != NULL && strcmp(user, "root")) {
             flexarray_append(dm_args, "-runas");
             flexarray_append(dm_args, user);
-- 
1.7.10.4