virsh: Increase device-detach intelligence

Up to now users have to give a full XML description on input when
device-detaching. If they omitted something it lead to unclear
error messages (like generated MAC wasn't found, etc.).
With this patch users can specify only those information which
specify one device sufficiently precise. Remaining information is
completed from domain.

tools/virsh.c

@@ -60,6 +60,7 @@
 #include "command.h"
 #include "virkeycode.h"
 #include "virnetdevbandwidth.h"
+#include "util/bitmap.h"
 
 static char *progname;
 
@@ -11502,6 +11503,246 @@ cmdAttachDevice(vshControl *ctl, const vshCmd *cmd)
     return true;
 }
 
+/**
+ * Check if n1 is superset of n2, meaning n1 contains all elements and
+ * attributes as n2 at least. Including children.
+ * @n1 first node
+ * @n2 second node
+ * returns true in case n1 covers n2, false otherwise.
+ */
+static bool
+vshNodeIsSuperset(xmlNodePtr n1, xmlNodePtr n2)
+{
+    xmlNodePtr child1, child2;
+    xmlAttrPtr attr;
+    char *prop1, *prop2;
+    bool found;
+    bool visited;
+    bool ret = false;
+    unsigned long n1_child_size, n2_child_size, n1_iter;
+    virBitmapPtr bitmap;
+
+    if (!n1 && !n2)
+        return true;
+
+    if (!n1 || !n2)
+        return false;
+
+    if (!xmlStrEqual(n1->name, n2->name))
+        return false;
+
+    /* Iterate over n2 attributes and check if n1 contains them*/
+    attr = n2->properties;
+    while (attr) {
+        if (attr->type == XML_ATTRIBUTE_NODE) {
+            prop1 = virXMLPropString(n1, (const char *) attr->name);
+            prop2 = virXMLPropString(n2, (const char *) attr->name);
+            if (STRNEQ_NULLABLE(prop1, prop2)) {
+                xmlFree(prop1);
+                xmlFree(prop2);
+                return false;
+            }
+            xmlFree(prop1);
+            xmlFree(prop2);
+        }
+        attr = attr->next;
+    }
+
+    n1_child_size = xmlChildElementCount(n1);
+    n2_child_size = xmlChildElementCount(n2);
+    if (n1_child_size < n2_child_size)
+        return false;
+
+    if (!(bitmap = virBitmapAlloc(n1_child_size))) {
+        virReportOOMError();
+        return false;
+    }
+
+    child2 = n2->children;
+    while (child2) {
+        if (child2->type != XML_ELEMENT_NODE) {
+            child2 = child2->next;
+            continue;
+        }
+
+        child1 = n1->children;
+        n1_iter = 0;
+        found = false;
+        while (child1) {
+            if (child1->type != XML_ELEMENT_NODE) {
+                child1 = child1->next;
+                continue;
+            }
+
+            if (virBitmapGetBit(bitmap, n1_iter, &visited) < 0) {
+                vshError(NULL, "%s", _("Bad child elements counting."));
+                goto cleanup;
+            }
+
+            if (visited) {
+                child1 = child1->next;
+                n1_iter++;
+                continue;
+            }
+
+            if (xmlStrEqual(child1->name, child2->name)) {
+                found = true;
+                if (virBitmapSetBit(bitmap, n1_iter) < 0) {
+                    vshError(NULL, "%s", _("Bad child elements counting."));
+                    goto cleanup;
+                }
+
+                if (!vshNodeIsSuperset(child1, child2))
+                    goto cleanup;
+
+                break;
+            }
+
+            child1 = child1->next;
+            n1_iter++;
+        }
+
+        if (!found)
+            goto cleanup;
+
+        child2 = child2->next;
+    }
+
+    ret = true;
+
+cleanup:
+    virBitmapFree(bitmap);
+    return ret;
+}
+
+/**
+ * vshCompleteXMLFromDomain:
+ * @ctl vshControl for error messages printing
+ * @dom domain
+ * @oldXML device XML before
+ * @newXML and after completion
+ *
+ * For given domain and (probably incomplete) device XML specification try to
+ * find such device in domain and complete missing parts. This is however
+ * possible only when given device XML is sufficiently precise so it addresses
+ * only one device.
+ *
+ * Returns -2 when no such device exists in domain, -3 when given XML selects many
+ *          (is too ambiguous), 0 in case of success. Otherwise returns -1. @newXML
+ *          is touched only in case of success.
+ */
+static int
+vshCompleteXMLFromDomain(vshControl *ctl, virDomainPtr dom, char *oldXML,
+                         char **newXML)
+{
+    int funcRet = -1;
+    char *domXML = NULL;
+    xmlDocPtr domDoc = NULL, devDoc = NULL;
+    xmlNodePtr node = NULL;
+    xmlXPathContextPtr domCtxt = NULL, devCtxt = NULL;
+    xmlNodePtr *devices = NULL;
+    xmlSaveCtxtPtr sctxt = NULL;
+    int devices_size;
+    char *xpath = NULL;
+    xmlBufferPtr buf = NULL;
+    int i = 0;
+    int indx = -1;
+
+    if (!(domXML = virDomainGetXMLDesc(dom, 0))) {
+        vshError(ctl, _("couldn't get XML description of domain %s"),
+                 virDomainGetName(dom));
+        goto cleanup;
+    }
+
+    domDoc = virXMLParseStringCtxt(domXML, _("(domain_definition)"), &domCtxt);
+    if (!domDoc) {
+        vshError(ctl, _("Failed to parse domain definition xml"));
+        goto cleanup;
+    }
+
+    devDoc = virXMLParseStringCtxt(oldXML, _("(device_definition)"), &devCtxt);
+    if (!devDoc) {
+        vshError(ctl, _("Failed to parse device definition xml"));
+        goto cleanup;
+    }
+
+    node = xmlDocGetRootElement(devDoc);
+
+    buf = xmlBufferCreate();
+    if (!buf) {
+        vshError(ctl, "%s", _("out of memory"));
+        goto cleanup;
+    }
+
+    /* Get all possible devices */
+    virAsprintf(&xpath, "/domain/devices/%s", node->name);
+    if (!xpath) {
+        virReportOOMError();
+        goto cleanup;
+    }
+    devices_size = virXPathNodeSet(xpath, domCtxt, &devices);
+
+    if (devices_size < 0) {
+        /* error */
+        vshError(ctl, "%s", _("error when selecting nodes"));
+        goto cleanup;
+    } else if (devices_size == 0) {
+        /* no such device */
+        funcRet = -2;
+        goto cleanup;
+    }
+
+    /* and refine */
+    for (i = 0; i < devices_size; i++) {
+        if (vshNodeIsSuperset(devices[i], node)) {
+            if (indx >= 0) {
+                funcRet = -3; /* ambiguous */
+                goto cleanup;
+            }
+            indx = i;
+        }
+    }
+
+    if (indx < 0) {
+        funcRet = -2; /* no such device */
+        goto cleanup;
+    }
+
+    vshDebug(ctl, VSH_ERR_DEBUG, "Found device at pos %d\n", indx);
+
+    if (newXML) {
+        sctxt = xmlSaveToBuffer(buf, NULL, 0);
+        if (!sctxt) {
+            vshError(ctl, "%s", _("failed to create document saving context"));
+            goto cleanup;
+        }
+
+        xmlSaveTree(sctxt, devices[indx]);
+        xmlSaveClose(sctxt);
+        *newXML = (char *) xmlBufferContent(buf);
+        if (!*newXML) {
+            virReportOOMError();
+            goto cleanup;
+        }
+        buf->content = NULL;
+    }
+
+    vshDebug(ctl, VSH_ERR_DEBUG, "Old xml:\n%s\nNew xml:\n%s\n", oldXML,
+             newXML ? NULLSTR(*newXML) : "(null)");
+
+    funcRet = 0;
+
+cleanup:
+    xmlBufferFree(buf);
+    VIR_FREE(devices);
+    xmlXPathFreeContext(devCtxt);
+    xmlXPathFreeContext(domCtxt);
+    xmlFreeDoc(devDoc);
+    xmlFreeDoc(domDoc);
+    VIR_FREE(domXML);
+    VIR_FREE(xpath);
+    return funcRet;
+}
 
 /*
  * "detach-device" command
@@ -11522,10 +11763,11 @@ static const vshCmdOptDef opts_detach_device[] = {
 static bool
 cmdDetachDevice(vshControl *ctl, const vshCmd *cmd)
 {
-    virDomainPtr dom;
+    virDomainPtr dom = NULL;
     const char *from = NULL;
-    char *buffer;
+    char *buffer = NULL, *new_buffer = NULL;
     int ret;
+    bool funcRet = false;
     unsigned int flags;
 
     if (!vshConnectionUsability(ctl, ctl->conn))
@@ -11534,37 +11776,50 @@ cmdDetachDevice(vshControl *ctl, const vshCmd *cmd)
     if (!(dom = vshCommandOptDomain(ctl, cmd, NULL)))
         return false;
 
-    if (vshCommandOptString(cmd, "file", &from) <= 0) {
+    if (vshCommandOptString(cmd, "file", &from) <= 0)
-        virDomainFree(dom);
+        goto cleanup;
-        return false;
-    }
 
     if (virFileReadAll(from, VIRSH_MAX_XML_FILE, &buffer) < 0) {
         virshReportError(ctl);
-        virDomainFree(dom);
+        goto cleanup;
-        return false;
+    }
+
+    ret = vshCompleteXMLFromDomain(ctl, dom, buffer, &new_buffer);
+    if (ret < 0) {
+        if (ret == -2) {
+            vshError(ctl, _("no such device in %s"), virDomainGetName(dom));
+        } else if (ret == -3) {
+            vshError(ctl, "%s", _("given XML selects too many devices. "
+                                  "Please, be more specific"));
+        } else {
+            /* vshCompleteXMLFromDomain() already printed error message,
+             * so nothing to do here. */
+        }
+        goto cleanup;
     }
 
     if (vshCommandOptBool(cmd, "persistent")) {
         flags = VIR_DOMAIN_AFFECT_CONFIG;
         if (virDomainIsActive(dom) == 1)
            flags |= VIR_DOMAIN_AFFECT_LIVE;
-        ret = virDomainDetachDeviceFlags(dom, buffer, flags);
+        ret = virDomainDetachDeviceFlags(dom, new_buffer, flags);
     } else {
-        ret = virDomainDetachDevice(dom, buffer);
+        ret = virDomainDetachDevice(dom, new_buffer);
     }
-    VIR_FREE(buffer);
 
     if (ret < 0) {
         vshError(ctl, _("Failed to detach device from %s"), from);
-        virDomainFree(dom);
+        goto cleanup;
-        return false;
-    } else {
-        vshPrint(ctl, "%s", _("Device detached successfully\n"));
     }
 
+    vshPrint(ctl, "%s", _("Device detached successfully\n"));
+    funcRet = true;
+
+cleanup:
+    VIR_FREE(new_buffer);
+    VIR_FREE(buffer);
     virDomainFree(dom);
-    return true;
+    return funcRet;
 }