util: capabilities detection for dnsmasq

In order to optionally take advantage of new features in dnsmasq when
the host's version of dnsmasq supports them, but still be able to run
on hosts that don't support the new features, we need to be able to
detect the version of dnsmasq running on the host, and possibly
determine from the help output what options are in this dnsmasq.

This patch implements a greatly simplified version of the capabilities
code we already have for qemu. A dnsmasqCaps device can be created and
populated either from running a program on disk, reading a file with
the concatenated output of "dnsmasq --version; dnsmasq --help", or
examining a buffer in memory that contains the concatenated output of
those two commands. Simple functions to retrieve capabilities flags,
the version number, and the path of the binary are also included.

bridge_driver.c creates a single dnsmasqCaps object at driver startup,
and disposes of it at driver shutdown. Any time it must be used, the
dnsmasqCapsRefresh method is called - it checks the mtime of the
binary, and re-runs the checks if the binary has changed.

networkxml2argvtest.c creates 2 "artificial" dnsmasqCaps objects at
startup - one "restricted" (doesn't support --bind-dynamic) and one
"full" (does support --bind-dynamic). Some of the test cases use one
and some the other, to make sure both code pathes are tested.

(cherry picked from commit 719c2c76)

Conflicts:
  src/network/bridge_driver.c
  * some new functions are missing in the backport, so they don't need
    to be modified.
  * Use dnsmasqCapsFree() instead of virObjectUnref()
  src/util/dnsmasq.c
  * eliminate use of virObject, since this version of libvirt
    doesn't yet have it
  * use networkReportError() instead of virReportError()
  * virBitmapAlloc() instead of virBitmapNew()
  src/util/dnsmasq.h
  * don't #include virobject.h
  * add prototype for dnsmasqCapsFree()
  src/libvirt_private.syms
  * export dnsmasqCapsFree

src/libvirt_private.syms

@@ -210,6 +210,14 @@ virUnrefStream;
 # dnsmasq.h
 dnsmasqAddDhcpHost;
 dnsmasqAddHost;
+dnsmasqCapsFree;
+dnsmasqCapsGet;
+dnsmasqCapsGetBinaryPath;
+dnsmasqCapsGetVersion;
+dnsmasqCapsNewFromBuffer;
+dnsmasqCapsNewFromFile;
+dnsmasqCapsNewFromBinary;
+dnsmasqCapsRefresh;
 dnsmasqContextFree;
 dnsmasqContextNew;
 dnsmasqDelete;

src/network/bridge_driver.c

@@ -85,6 +85,7 @@ struct network_driver {
     char *networkConfigDir;
     char *networkAutostartDir;
     char *logDir;
+    dnsmasqCapsPtr dnsmasqCaps;
 };
 
 
@@ -219,7 +220,8 @@ networkFindActiveConfigs(struct network_driver *driver) {
                 char *radvdpidbase;
 
                 ignore_value(virPidFileReadIfAlive(NETWORK_PID_DIR, obj->def->name,
-                                                   &obj->dnsmasqPid, DNSMASQ));
+                                                   &obj->dnsmasqPid,
+                                                   dnsmasqCapsGetBinaryPath(driver->dnsmasqCaps)));
 
                 if (!(radvdpidbase = networkRadvdPidfileBasename(obj->def->name))) {
                     virReportOOMError();
@@ -314,6 +316,8 @@ networkStartup(int privileged) {
         goto out_of_memory;
     }
 
+    /* if this fails now, it will be retried later with dnsmasqCapsRefresh() */
+    driverState->dnsmasqCaps = dnsmasqCapsNewFromBinary(DNSMASQ);
 
     if (virNetworkLoadAllConfigs(&driverState->networks,
                                  driverState->networkConfigDir,
@@ -411,6 +415,8 @@ networkShutdown(void) {
     if (driverState->iptables)
         iptablesContextFree(driverState->iptables);
 
+    dnsmasqCapsFree(driverState->dnsmasqCaps);
+
     networkDriverUnlock(driverState);
     virMutexDestroy(&driverState->lock);
 
@@ -454,7 +460,8 @@ networkBuildDnsmasqArgv(virNetworkObjPtr network,
                         virNetworkIpDefPtr ipdef,
                         const char *pidfile,
                         virCommandPtr cmd,
-                        dnsmasqContext *dctx)
+                        dnsmasqContext *dctx,
+                        dnsmasqCapsPtr caps ATTRIBUTE_UNUSED)
 {
     int r, ret = -1;
     int nbleases = 0;
@@ -679,7 +686,8 @@ cleanup:
 
 int
 networkBuildDhcpDaemonCommandLine(virNetworkObjPtr network, virCommandPtr *cmdout,
-                                  char *pidfile, dnsmasqContext *dctx)
+                                  char *pidfile, dnsmasqContext *dctx,
+                                  dnsmasqCapsPtr caps)
 {
     virCommandPtr cmd = NULL;
     int ret = -1, ii;
@@ -707,8 +715,8 @@ networkBuildDhcpDaemonCommandLine(virNetworkObjPtr network, virCommandPtr *cmdou
     if (!virNetworkDefGetIpByIndex(network->def, AF_UNSPEC, 0))
         return 0;
 
-    cmd = virCommandNew(DNSMASQ);
-    if (networkBuildDnsmasqArgv(network, ipdef, pidfile, cmd, dctx) < 0) {
+    cmd = virCommandNew(dnsmasqCapsGetBinaryPath(caps));
+    if (networkBuildDnsmasqArgv(network, ipdef, pidfile, cmd, dctx, caps) < 0) {
         goto cleanup;
     }
 
@@ -722,7 +730,8 @@ cleanup:
 }
 
 static int
-networkStartDhcpDaemon(virNetworkObjPtr network)
+networkStartDhcpDaemon(struct network_driver *driver,
+                       virNetworkObjPtr network)
 {
     virCommandPtr cmd = NULL;
     char *pidfile = NULL;
@@ -758,7 +767,10 @@ networkStartDhcpDaemon(virNetworkObjPtr network)
     if (dctx == NULL)
         goto cleanup;
 
-    ret = networkBuildDhcpDaemonCommandLine(network, &cmd, pidfile, dctx);
+    dnsmasqCapsRefresh(&driver->dnsmasqCaps, false);
+
+    ret = networkBuildDhcpDaemonCommandLine(network, &cmd, pidfile,
+                                            dctx, driver->dnsmasqCaps);
     if (ret < 0)
         goto cleanup;
 
@@ -1824,7 +1836,8 @@ networkStartNetworkVirtual(struct network_driver *driver,
 
 
     /* start dnsmasq if there are any IP addresses (v4 or v6) */
-    if ((v4present || v6present) && networkStartDhcpDaemon(network) < 0)
+    if ((v4present || v6present) &&
+        networkStartDhcpDaemon(driver, network) < 0)
         goto err3;
 
     /* start radvd if there are any ipv6 addresses */

src/network/bridge_driver.h

 /*
  * network_driver.h: core driver methods for managing networks
  *
- * Copyright (C) 2006, 2007, 2011 Red Hat, Inc.
+ * Copyright (C) 2006-2012 Red Hat, Inc.
  * Copyright (C) 2006 Daniel P. Berrange
  *
  * This library is free software; you can redistribute it and/or
@@ -48,7 +48,8 @@ int networkGetNetworkAddress(const char *netname, char **netaddr)
 
 int networkBuildDhcpDaemonCommandLine(virNetworkObjPtr network,
                                       virCommandPtr *cmdout, char *pidfile,
-                                      dnsmasqContext *dctx)
+                                      dnsmasqContext *dctx,
+                                      dnsmasqCapsPtr caps)
     ;
 # else
 /* Define no-op replacements that don't drag in any link dependencies.  */
@@ -56,7 +57,7 @@ int networkBuildDhcpDaemonCommandLine(virNetworkObjPtr network,
 #  define networkNotifyActualDevice(iface) 0
 #  define networkReleaseActualDevice(iface) 0
 #  define networkGetNetworkAddress(netname, netaddr) (-2)
-#  define networkBuildDhcpDaemonCommandLine(network, cmdout, pidfile, dctx) 0
+#  define networkBuildDhcpDaemonCommandLine(network, cmdout, pidfile, dctx, caps) 0
 # endif
 
 typedef char *(*networkDnsmasqLeaseFileNameFunc)(const char *netname);

src/util/dnsmasq.c

 /*
- * Copyright (C) 2007-2011 Red Hat, Inc.
+ * Copyright (C) 2007-2012 Red Hat, Inc.
  * Copyright (C) 2010 Satoru SATOH <satoru.satoh@gmail.com>
  *
  * This library is free software; you can redistribute it and/or
@@ -39,14 +39,20 @@
 
 #include "internal.h"
 #include "datatypes.h"
+#include "bitmap.h"
 #include "dnsmasq.h"
 #include "util.h"
+#include "command.h"
 #include "memory.h"
 #include "virterror_internal.h"
 #include "logging.h"
 #include "virfile.h"
 
 #define VIR_FROM_THIS VIR_FROM_NETWORK
+#define networkReportError(code, ...)                                   \
+    virReportErrorHelper(VIR_FROM_NETWORK, code, __FILE__,              \
+                         __FUNCTION__, __LINE__, __VA_ARGS__)
+
 #define DNSMASQ_HOSTSFILE_SUFFIX "hostsfile"
 #define DNSMASQ_ADDNHOSTSFILE_SUFFIX "addnhosts"
 
@@ -581,3 +587,259 @@ dnsmasqReload(pid_t pid ATTRIBUTE_UNUSED)
 
     return 0;
 }
+
+/*
+ * dnsmasqCapabilities functions - provide useful information about the
+ * version of dnsmasq on this machine.
+ *
+ */
+struct _dnsmasqCaps {
+    char *binaryPath;
+    bool noRefresh;
+    time_t mtime;
+    virBitmapPtr flags;
+    unsigned long version;
+};
+
+void
+dnsmasqCapsFree(dnsmasqCapsPtr caps)
+{
+    if (!caps)
+        return;
+    virBitmapFree(caps->flags);
+    VIR_FREE(caps->binaryPath);
+}
+
+static void
+dnsmasqCapsSet(dnsmasqCapsPtr caps,
+               dnsmasqCapsFlags flag)
+{
+    ignore_value(virBitmapSetBit(caps->flags, flag));
+}
+
+
+#define DNSMASQ_VERSION_STR "Dnsmasq version "
+
+static int
+dnsmasqCapsSetFromBuffer(dnsmasqCapsPtr caps, const char *buf)
+{
+    const char *p;
+
+    caps->noRefresh = true;
+
+    p = STRSKIP(buf, DNSMASQ_VERSION_STR);
+    if (!p)
+       goto fail;
+    virSkipSpaces(&p);
+    if (virParseVersionString(p, &caps->version, true) < 0)
+        goto fail;
+
+    if (strstr(buf, "--bind-dynamic"))
+        dnsmasqCapsSet(caps, DNSMASQ_CAPS_BIND_DYNAMIC);
+
+    VIR_INFO("dnsmasq version is %d.%d, --bind-dynamic is %s",
+             (int)caps->version / 1000000, (int)(caps->version % 1000000) / 1000,
+             dnsmasqCapsGet(caps, DNSMASQ_CAPS_BIND_DYNAMIC)
+             ? "present" : "NOT present");
+    return 0;
+
+fail:
+    p = strchrnul(buf, '\n');
+    networkReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("cannot parse %s version number in '%.*s'"),
+                       caps->binaryPath, (int) (p - buf), buf);
+    return -1;
+
+}
+
+static int
+dnsmasqCapsSetFromFile(dnsmasqCapsPtr caps, const char *path)
+{
+    int ret = -1;
+    char *buf = NULL;
+
+    if (virFileReadAll(path, 1024 * 1024, &buf) < 0)
+        goto cleanup;
+
+    ret = dnsmasqCapsSetFromBuffer(caps, buf);
+
+cleanup:
+    VIR_FREE(buf);
+    return ret;
+}
+
+static int
+dnsmasqCapsRefreshInternal(dnsmasqCapsPtr caps, bool force)
+{
+    int ret = -1;
+    struct stat sb;
+    virCommandPtr cmd = NULL;
+    char *help = NULL, *version = NULL, *complete = NULL;
+
+    if (!caps || caps->noRefresh)
+        return 0;
+
+    if (stat(caps->binaryPath, &sb) < 0) {
+        virReportSystemError(errno, _("Cannot check dnsmasq binary %s"),
+                             caps->binaryPath);
+        return -1;
+    }
+    if (!force && caps->mtime == sb.st_mtime) {
+        return 0;
+    }
+    caps->mtime = sb.st_mtime;
+
+    /* Make sure the binary we are about to try exec'ing exists.
+     * Technically we could catch the exec() failure, but that's
+     * in a sub-process so it's hard to feed back a useful error.
+     */
+    if (!virFileIsExecutable(caps->binaryPath)) {
+        virReportSystemError(errno, _("dnsmasq binary %s is not executable"),
+                             caps->binaryPath);
+        goto cleanup;
+    }
+
+    cmd = virCommandNewArgList(caps->binaryPath, "--version", NULL);
+    virCommandSetOutputBuffer(cmd, &version);
+    virCommandSetErrorBuffer(cmd, &version);
+    virCommandAddEnvPassCommon(cmd);
+    virCommandClearCaps(cmd);
+    if (virCommandRun(cmd, NULL) < 0) {
+        virReportSystemError(errno, _("failed to run '%s --version': %s"),
+                             caps->binaryPath, version);
+        goto cleanup;
+    }
+    virCommandFree(cmd);
+
+    cmd = virCommandNewArgList(caps->binaryPath, "--help", NULL);
+    virCommandSetOutputBuffer(cmd, &help);
+    virCommandSetErrorBuffer(cmd, &help);
+    virCommandAddEnvPassCommon(cmd);
+    virCommandClearCaps(cmd);
+    if (virCommandRun(cmd, NULL) < 0) {
+        virReportSystemError(errno, _("failed to run '%s --help': %s"),
+                             caps->binaryPath, help);
+        goto cleanup;
+    }
+
+    if (virAsprintf(&complete, "%s\n%s", version, help) < 0) {
+        virReportOOMError();
+        goto cleanup;
+    }
+
+    ret = dnsmasqCapsSetFromBuffer(caps, complete);
+
+cleanup:
+    virCommandFree(cmd);
+    VIR_FREE(help);
+    VIR_FREE(version);
+    VIR_FREE(complete);
+    return ret;
+}
+
+static dnsmasqCapsPtr
+dnsmasqCapsNewEmpty(const char *binaryPath)
+{
+    dnsmasqCapsPtr caps;
+
+    if (VIR_ALLOC(caps) < 0)
+        return NULL;
+    if (!(caps->flags = virBitmapAlloc(DNSMASQ_CAPS_LAST)))
+        goto error;
+    if (!(caps->binaryPath = strdup(binaryPath ? binaryPath : DNSMASQ)))
+        goto error;
+    return caps;
+
+error:
+    virReportOOMError();
+    dnsmasqCapsFree(caps);
+    return NULL;
+}
+
+dnsmasqCapsPtr
+dnsmasqCapsNewFromBuffer(const char *buf, const char *binaryPath)
+{
+    dnsmasqCapsPtr caps = dnsmasqCapsNewEmpty(binaryPath);
+
+    if (!caps)
+        return NULL;
+
+    if (dnsmasqCapsSetFromBuffer(caps, buf) < 0) {
+        dnsmasqCapsFree(caps);
+        return NULL;
+    }
+    return caps;
+}
+
+dnsmasqCapsPtr
+dnsmasqCapsNewFromFile(const char *dataPath, const char *binaryPath)
+{
+    dnsmasqCapsPtr caps = dnsmasqCapsNewEmpty(binaryPath);
+
+    if (!caps)
+        return NULL;
+
+    if (dnsmasqCapsSetFromFile(caps, dataPath) < 0) {
+        dnsmasqCapsFree(caps);
+        return NULL;
+    }
+    return caps;
+}
+
+dnsmasqCapsPtr
+dnsmasqCapsNewFromBinary(const char *binaryPath)
+{
+    dnsmasqCapsPtr caps = dnsmasqCapsNewEmpty(binaryPath);
+
+    if (!caps)
+        return NULL;
+
+    if (dnsmasqCapsRefreshInternal(caps, true) < 0) {
+        dnsmasqCapsFree(caps);
+        return NULL;
+    }
+    return caps;
+}
+
+/** dnsmasqCapsRefresh:
+ *
+ *   Refresh an existing caps object if the binary has changed. If
+ *   there isn't yet a caps object (if it's NULL), create a new one.
+ *
+ *   Returns 0 on success, -1 on failure
+ */
+int
+dnsmasqCapsRefresh(dnsmasqCapsPtr *caps, const char *binaryPath)
+{
+    if (!*caps) {
+        *caps = dnsmasqCapsNewFromBinary(binaryPath);
+        return *caps ? 0 : -1;
+    }
+    return dnsmasqCapsRefreshInternal(*caps, false);
+}
+
+const char *
+dnsmasqCapsGetBinaryPath(dnsmasqCapsPtr caps)
+{
+    return caps ? caps->binaryPath : DNSMASQ;
+}
+
+unsigned long
+dnsmasqCapsGetVersion(dnsmasqCapsPtr caps)
+{
+    if (caps)
+        return caps->version;
+    else
+        return 0;
+}
+
+bool
+dnsmasqCapsGet(dnsmasqCapsPtr caps, dnsmasqCapsFlags flag)
+{
+    bool b;
+
+    if (!caps || virBitmapGetBit(caps->flags, flag, &b) < 0)
+        return false;
+    else
+        return b;
+}

src/util/dnsmasq.h

 /*
- * Copyright (C) 2007-2010 Red Hat, Inc.
+ * Copyright (C) 2007-2012 Red Hat, Inc.
  * Copyright (C) 2010 Satoru SATOH <satoru.satoh@gmail.com>
  *
  * This library is free software; you can redistribute it and/or
@@ -65,6 +65,16 @@ typedef struct
     dnsmasqAddnHostsfile *addnhostsfile;
 } dnsmasqContext;
 
+typedef enum {
+   DNSMASQ_CAPS_BIND_DYNAMIC = 0, /* support for --bind-dynamic */
+
+   DNSMASQ_CAPS_LAST,             /* this must always be the last item */
+} dnsmasqCapsFlags;
+
+typedef struct _dnsmasqCaps dnsmasqCaps;
+typedef dnsmasqCaps *dnsmasqCapsPtr;
+
+
 dnsmasqContext * dnsmasqContextNew(const char *network_name,
                                    const char *config_dir);
 void             dnsmasqContextFree(dnsmasqContext *ctx);
@@ -79,4 +89,14 @@ int              dnsmasqSave(const dnsmasqContext *ctx);
 int              dnsmasqDelete(const dnsmasqContext *ctx);
 int              dnsmasqReload(pid_t pid);
 
+dnsmasqCapsPtr dnsmasqCapsNewFromBuffer(const char *buf,
+                                        const char *binaryPath);
+dnsmasqCapsPtr dnsmasqCapsNewFromFile(const char *dataPath,
+                                      const char *binaryPath);
+dnsmasqCapsPtr dnsmasqCapsNewFromBinary(const char *binaryPath);
+void dnsmasqCapsFree(dnsmasqCapsPtr caps);
+int dnsmasqCapsRefresh(dnsmasqCapsPtr *caps, const char *binaryPath);
+bool dnsmasqCapsGet(dnsmasqCapsPtr caps, dnsmasqCapsFlags flag);
+const char *dnsmasqCapsGetBinaryPath(dnsmasqCapsPtr caps);
+unsigned long dnsmasqCapsGetVersion(dnsmasqCapsPtr caps);
 #endif /* __DNSMASQ_H__ */

tests/networkxml2argvtest.c

@@ -46,7 +46,9 @@ static int replaceTokens(char **buf, const char *token, const char *replacement)
     return 0;
 }
 
-static int testCompareXMLToArgvFiles(const char *inxml, const char *outargv) {
+static int
+testCompareXMLToArgvFiles(const char *inxml, const char *outargv, dnsmasqCapsPtr caps)
+{
     char *inXmlData = NULL;
     char *outArgvData = NULL;
     char *actual = NULL;
@@ -78,7 +80,7 @@ static int testCompareXMLToArgvFiles(const char *inxml, const char *outargv) {
     if (dctx == NULL)
         goto fail;
 
-    if (networkBuildDhcpDaemonCommandLine(obj, &cmd, pidfile, dctx) < 0)
+    if (networkBuildDhcpDaemonCommandLine(obj, &cmd, pidfile, dctx, caps) < 0)
         goto fail;
 
     if (!(actual = virCommandToString(cmd)))
@@ -102,21 +104,27 @@ static int testCompareXMLToArgvFiles(const char *inxml, const char *outargv) {
     return ret;
 }
 
+typedef struct {
+    const char *name;
+    dnsmasqCapsPtr caps;
+} testInfo;
+
 static int
 testCompareXMLToArgvHelper(const void *data)
 {
     int result = -1;
+    const testInfo *info = data;
     char *inxml = NULL;
     char *outxml = NULL;
 
     if (virAsprintf(&inxml, "%s/networkxml2argvdata/%s.xml",
-                    abs_srcdir, (const char*)data) < 0 ||
+                    abs_srcdir, info->name) < 0 ||
         virAsprintf(&outxml, "%s/networkxml2argvdata/%s.argv",
-                    abs_srcdir, (const char*)data) < 0) {
+                    abs_srcdir, info->name) < 0) {
         goto cleanup;
     }
 
-    result = testCompareXMLToArgvFiles(inxml, outxml);
+    result = testCompareXMLToArgvFiles(inxml, outxml, info->caps);
 
 cleanup:
     VIR_FREE(inxml);
@@ -140,23 +148,34 @@ static int
 mymain(void)
 {
     int ret = 0;
+    dnsmasqCapsPtr restricted
+        = dnsmasqCapsNewFromBuffer("Dnsmasq version 2.48", DNSMASQ);
+    dnsmasqCapsPtr full
+        = dnsmasqCapsNewFromBuffer("Dnsmasq version 2.63\n--bind-dynamic", DNSMASQ);
 
     networkDnsmasqLeaseFileName = testDnsmasqLeaseFileName;
 
-#define DO_TEST(name) \
-    if (virtTestRun("Network XML-2-Argv " name, \
-                    1, testCompareXMLToArgvHelper, (name)) < 0) \
-        ret = -1
-
-    DO_TEST("isolated-network");
-    DO_TEST("routed-network");
-    DO_TEST("nat-network");
-    DO_TEST("netboot-network");
-    DO_TEST("netboot-proxy-network");
-    DO_TEST("nat-network-dns-txt-record");
-    DO_TEST("nat-network-dns-srv-record");
-    DO_TEST("nat-network-dns-srv-record-minimal");
-    DO_TEST("nat-network-dns-hosts");
+#define DO_TEST(xname, xcaps)                                        \
+    do {                                                             \
+        static testInfo info;                                        \
+                                                                     \
+        info.name = xname;                                           \
+        info.caps = xcaps;                                           \
+        if (virtTestRun("Network XML-2-Argv " xname,                 \
+                        1, testCompareXMLToArgvHelper, &info) < 0) { \
+            ret = -1;                                                \
+        }                                                            \
+    } while (0)
+
+    DO_TEST("isolated-network", restricted);
+    DO_TEST("netboot-network", restricted);
+    DO_TEST("netboot-proxy-network", restricted);
+    DO_TEST("nat-network-dns-srv-record-minimal", restricted);
+    DO_TEST("routed-network", full);
+    DO_TEST("nat-network", full);
+    DO_TEST("nat-network-dns-txt-record", full);
+    DO_TEST("nat-network-dns-srv-record", full);
+    DO_TEST("nat-network-dns-hosts", full);
 
     return ret==0 ? EXIT_SUCCESS : EXIT_FAILURE;
 }