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[libvirt] [PATCH v3] Add helper program to create custom leases



Introduce helper program to catch events from dnsmasq and maintain a custom
lease file per network. It supports dhcpv4 and dhcpv6. The file is saved as
"<interface-name>.status".

Each lease contains the following info:
<expiry-time (epoch time)> <mac> <iaid> <ip-address> <hostname> <clientid>

Example of custom leases file content:
[
    {
        "iaid": "1221229",
        "ip-address": "2001:db8:ca2:2:1::95",
        "mac-address": "52:54:00:12:a2:6d",
        "hostname": "Fedora20",
        "client-id": "00:04:1a:c1:d9:6b:5a:0a:e2:bc:f8:4b:1e:37:2e:38:22:55",
        "expiry-time": 1393244216
    },
    {
        "ip-address": "192.168.150.208",
        "mac-address": "52:54:00:11:56:b3",
        "hostname": "Wani-PC",
        "client-id": "01:52:54:00:11:56:b3",
        "expiry-time": 1393244248
    }
]

src/Makefile.am:
   * Add options to compile the helper program

src/network/bridge_driver.c:
   * Introduce networkDnsmasqLeaseFileNameCustom()
   * Invoke helper program along with dnsmasq
   * Delete the .status file when corresponding n/w is destroyed.

src/util/leaseshelper.c
   * Helper program to create the custom lease file

---
 v3:
 * Improved file handling, removed redundant copying, introduced --help and --version

 v2:
 * Changed format to JSON
 * Refer: https://www.redhat.com/archives/libvir-list/2014-January/msg01234.html

 v1:
 * Refer: https://www.redhat.com/archives/libvir-list/2014-January/msg00626.html

 src/Makefile.am             |   16 +++
 src/network/bridge_driver.c |   19 +++
 src/util/leaseshelper.c     |  303 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 338 insertions(+), 0 deletions(-)
 create mode 100644 src/util/leaseshelper.c

diff --git a/src/Makefile.am b/src/Makefile.am
index 6d21e5d..b8e1993 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -849,6 +849,9 @@ STORAGE_HELPER_DISK_SOURCES =					\
 UTIL_IO_HELPER_SOURCES =					\
 		util/iohelper.c
 
+UTIL_LEASES_HELPER_SOURCES =					\
+		util/leaseshelper.c
+
 # Network filters
 NWFILTER_DRIVER_SOURCES =						\
 		nwfilter/nwfilter_driver.h nwfilter/nwfilter_driver.c	\
@@ -2444,6 +2447,19 @@ libvirt_iohelper_CFLAGS = \
 		$(AM_CFLAGS) \
 		$(PIE_CFLAGS) \
 		$(NULL)
+
+libexec_PROGRAMS += libvirt_leaseshelper
+libvirt_leaseshelper_SOURCES = $(UTIL_LEASES_HELPER_SOURCES)
+libvirt_leaseshelper_LDADD =           \
+               libvirt_util.la         \
+               ../gnulib/lib/libgnu.la
+if WITH_DTRACE_PROBES
+libvirt_leaseshelper_LDADD += libvirt_probes.lo
+endif WITH_DTRACE_PROBES
+
+libvirt_leaseshelper_CFLAGS = \
+               $(PIE_CFLAGS) \
+               $(NULL)
 endif WITH_LIBVIRTD
 
 if WITH_STORAGE_DISK
diff --git a/src/network/bridge_driver.c b/src/network/bridge_driver.c
index a6c719d..9fb750f 100644
--- a/src/network/bridge_driver.c
+++ b/src/network/bridge_driver.c
@@ -205,6 +205,16 @@ networkDnsmasqLeaseFileNameFunc networkDnsmasqLeaseFileName =
     networkDnsmasqLeaseFileNameDefault;
 
 static char *
+networkDnsmasqLeaseFileNameCustom(const char *bridge)
+{
+    char *leasefile;
+
+    ignore_value(virAsprintf(&leasefile, "%s/%s.status",
+                             driverState->dnsmasqStateDir, bridge));
+    return leasefile;
+}
+
+static char *
 networkDnsmasqConfigFileName(const char *netname)
 {
     char *conffile;
@@ -240,6 +250,7 @@ networkRemoveInactive(virNetworkDriverStatePtr driver,
                       virNetworkObjPtr net)
 {
     char *leasefile = NULL;
+    char *customleasefile = NULL;
     char *radvdconfigfile = NULL;
     char *configfile = NULL;
     char *radvdpidbase = NULL;
@@ -258,6 +269,9 @@ networkRemoveInactive(virNetworkDriverStatePtr driver,
     if (!(leasefile = networkDnsmasqLeaseFileName(def->name)))
         goto cleanup;
 
+    if (!(customleasefile = networkDnsmasqLeaseFileNameCustom(def->bridge)))
+        goto cleanup;
+
     if (!(radvdconfigfile = networkRadvdConfigFileName(def->name)))
         goto cleanup;
 
@@ -274,6 +288,7 @@ networkRemoveInactive(virNetworkDriverStatePtr driver,
     /* dnsmasq */
     dnsmasqDelete(dctx);
     unlink(leasefile);
+    unlink(customleasefile);
     unlink(configfile);
 
     /* radvd */
@@ -1117,6 +1132,10 @@ networkBuildDhcpDaemonCommandLine(virNetworkObjPtr network,
 
     cmd = virCommandNew(dnsmasqCapsGetBinaryPath(caps));
     virCommandAddArgFormat(cmd, "--conf-file=%s", configfile);
+
+    /* This helper is used to create custom leases file for libvirt */
+    virCommandAddArgFormat(cmd, "--dhcp-script=%s", LIBEXECDIR "/libvirt_leaseshelper");
+
     *cmdout = cmd;
     ret = 0;
 cleanup:
diff --git a/src/util/leaseshelper.c b/src/util/leaseshelper.c
new file mode 100644
index 0000000..bd8110f
--- /dev/null
+++ b/src/util/leaseshelper.c
@@ -0,0 +1,303 @@
+/*
+ * leasehelper.c: Helper program to create custom leases file
+ *
+ * Copyright (C) 2014 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * Author: Nehal J Wani <nehaljw kkd1 gmail com>
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+
+#include "virutil.h"
+#include "virthread.h"
+#include "virfile.h"
+#include "virbuffer.h"
+#include "virstring.h"
+#include "virerror.h"
+#include "viralloc.h"
+#include "virjson.h"
+#include "configmake.h"
+
+#define VIR_FROM_THIS VIR_FROM_NETWORK
+
+/**
+ * VIR_NETWORK_DHCP_LEASE_FILE_SIZE_MAX:
+ *
+ * Macro providing the upper limit on the size of leases file
+ */
+#define VIR_NETWORK_DHCP_LEASE_FILE_SIZE_MAX (2 * 1024 * 1024)
+
+static const char *program_name;
+
+/* Display version information. */
+static void
+helperVersion(const char *argv0)
+{
+    printf("%s (%s) %s\n", argv0, PACKAGE_NAME, PACKAGE_VERSION);
+}
+
+ATTRIBUTE_NORETURN static void
+usage(int status)
+{
+    if (status) {
+        fprintf(stderr, _("%s: try --help for more details\n"), program_name);
+    } else {
+        printf(_("Usage: %s ACTION MAC|CLIENTID IP HOSTNAME\n"
+                 "   or: %s ACTION MAC|CLIENTID IP\n"),
+               program_name, program_name);
+    }
+    exit(status);
+}
+
+static int
+customLeaseRewriteFile(int fd, void *opaque)
+{
+    char **data = opaque;
+
+    if (safewrite(fd, *data, strlen(*data)) < 0)
+        return -1;
+
+    return 0;
+}
+
+int
+main(int argc, char **argv)
+{
+    char *lease_entries = NULL;
+    char *custom_lease_file = NULL;
+    const char *ip = NULL;
+    const char *mac = NULL;
+    const char *action = NULL;
+    const char *iaid = virGetEnvAllowSUID("DNSMASQ_IAID");
+    const char *clientid = virGetEnvAllowSUID("DNSMASQ_CLIENT_ID");
+    const char *interface = virGetEnvAllowSUID("DNSMASQ_INTERFACE");
+    const char *exptime = virGetEnvAllowSUID("DNSMASQ_LEASE_EXPIRES");
+    const char *hostname = virGetEnvAllowSUID("DNSMASQ_SUPPLIED_HOSTNAME");
+    const char *leases_str = NULL;
+    long long expirytime = 0;
+    size_t i = 0;
+    int rv = EXIT_FAILURE;
+    int size = 0;
+    int custom_lease_file_len = 0;
+    bool add = false;
+    bool delete = false;
+    virJSONValuePtr lease_new = NULL;
+    virJSONValuePtr lease_tmp = NULL;
+    virJSONValuePtr leases_array = NULL;
+    virJSONValuePtr leases_array_new = NULL;
+
+    virSetErrorFunc(NULL, NULL);
+    virSetErrorLogPriorityFunc(NULL);
+
+    program_name = argv[0];
+
+    if (setlocale(LC_ALL, "") == NULL ||
+        bindtextdomain(PACKAGE, LOCALEDIR) == NULL ||
+        textdomain(PACKAGE) == NULL) {
+        fprintf(stderr, _("%s: initialization failed\n"), program_name);
+        exit(EXIT_FAILURE);
+    }
+
+    if (virThreadInitialize() < 0 ||
+        virErrorInitialize() < 0) {
+        fprintf(stderr, _("%s: initialization failed\n"), program_name);
+        exit(EXIT_FAILURE);
+    }
+
+    /* Doesn't hurt to check */
+    if (argc > 1) {
+        if(STREQ(argv[1], "--help"))
+            usage(EXIT_SUCCESS);
+
+        if (STREQ(argv[1], "--version")) {
+            helperVersion(argv[0]);
+            exit(EXIT_SUCCESS);
+        }
+    }
+
+    if (argc != 4 && argc != 5) {
+        /* Refer man page of dnsmasq --dhcp-script for more details */
+        usage(EXIT_FAILURE);
+    }
+
+    /* Make sure dnsmasq knows the interface. The interface name is not known
+     * when dnsmasq (re)starts and throws 'del' events for expired leases.
+     * So, if any old lease has expired, it will be automatically removed the
+     * next time this program is invoked */
+    if (!interface)
+        goto cleanup;
+
+    ip = argv[3];
+    mac = argv[2];
+    action = argv[1];
+
+    /* In case hostname is known, it is the 5th argument */
+    if (argc == 5)
+	hostname = argv[4];
+
+    if (virAsprintf(&custom_lease_file, "%s/%s.status", LOCALSTATEDIR
+                    "/lib/libvirt/dnsmasq/", interface) < 0)
+        goto cleanup;
+
+    /* Check if it is an IPv6 lease */
+    if (virGetEnvAllowSUID("DNSMASQ_IAID")) {
+        mac = virGetEnvAllowSUID("DNSMASQ_MAC");
+        clientid=argv[2];
+    }
+
+    /* Since interfaces can be hot plugged, we need to make sure that the
+     * corresponding custom lease file exists. If not, 'touch' it */
+    if (virFileTouch(custom_lease_file, 0644) < 0)
+        goto cleanup;
+
+    /* Read entire contents */
+    if ((custom_lease_file_len = virFileReadAll(custom_lease_file,
+                                                VIR_NETWORK_DHCP_LEASE_FILE_SIZE_MAX,
+                                                &lease_entries)) < 0) {
+        goto cleanup;
+    }
+
+    if (STREQ(action, "add") || STREQ(action, "old") || STREQ(action, "del")) {
+        if (mac || STREQ(action, "del")) {
+            /* Delete the corresponding lease */
+            delete = true;
+            if (STREQ(action, "add") || STREQ(action, "old")) {
+                add = true;
+                /* Create new lease */
+                if (!(lease_new = virJSONValueNewObject())) {
+                    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                                   _("failed to create json"));
+                    goto cleanup;
+                }
+
+                if (virStrToLong_ll(exptime, NULL, 10, &expirytime) < 0) {
+                    virReportError(VIR_ERR_INTERNAL_ERROR,
+                                   _("Unable to convert lease expiry time to long long: %s"),
+                                   exptime);
+                    goto cleanup;
+                }
+
+                if ((iaid && virJSONValueObjectAppendString(lease_new, "iaid",
+                                                            iaid) < 0) ||
+                    (ip && virJSONValueObjectAppendString(lease_new, "ip-address",
+                                                          ip) < 0) ||
+                    (mac && virJSONValueObjectAppendString(lease_new, "mac-address",
+                                                           mac) < 0) ||
+                    (hostname && virJSONValueObjectAppendString(lease_new, "hostname",
+                                                                hostname) < 0) ||
+                    (clientid && virJSONValueObjectAppendString(lease_new, "client-id",
+                                                                clientid) < 0) ||
+                    (expirytime && virJSONValueObjectAppendNumberLong(lease_new, "expiry-time",
+                                                               expirytime) < 0)) {
+                    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                                   _("failed to create json"));
+                    goto cleanup;
+                }
+            }
+        }
+    }
+    else {
+        fprintf(stderr, _("Unsupported action: %s\n"), action);
+        exit(EXIT_FAILURE);
+    }
+
+    /* Check for previous leases */
+    if (custom_lease_file_len) {
+        if (!(leases_array = virJSONValueFromString(lease_entries))) {
+            virReportError(VIR_ERR_INTERNAL_ERROR,
+                           _("invalid json in file: %s"), custom_lease_file);
+            goto cleanup;
+        }
+
+        if ((size = virJSONValueArraySize(leases_array)) < 0) {
+            virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                           _("couldn't fetch array of leases"));
+            goto cleanup;
+        }
+    }
+
+    if (!(leases_array_new = virJSONValueNewArray())) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("failed to create json"));
+        goto cleanup;
+    }
+
+    for (i = 0; i < size; i++) {
+        const char *ip_tmp = NULL;
+        long long exptime_tmp = -1;
+
+        if (!(lease_tmp = virJSONValueArrayGet(leases_array, i))) {
+            virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                           _("failed to parse json"));
+            goto cleanup;
+        }
+
+        if (!(ip_tmp = virJSONValueObjectGetString(lease_tmp, "ip-address")) ||
+            (virJSONValueObjectGetNumberLong(lease_tmp, "expiry-time", &exptime_tmp) < 0)) {
+            virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                           _("failed to parse json"));
+            goto cleanup;
+        }
+
+        /* Check whether lease has expired or not */
+        if (exptime_tmp < (long long) time(NULL))
+            continue;
+
+        /* Check whether lease has to be included or not */
+        if (delete && STREQ(ip_tmp, ip))
+            continue;
+
+	/* Add old lease to new array */
+        if (virJSONValueArrayAppend(leases_array_new, lease_tmp) < 0) {
+            virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                           _("failed to create json"));
+            goto cleanup;
+        }
+    }
+
+    if (add) {
+        if (virJSONValueArrayAppend(leases_array_new, lease_new) < 0) {
+            virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                           _("failed to create json"));
+            goto cleanup;
+        }
+    }
+
+    if (!(leases_str = virJSONValueToString(leases_array_new, true))) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("empty json array"));
+        goto cleanup;
+    }
+
+    /* Write to file */
+    if (virFileRewrite(custom_lease_file, 0644,
+                       customLeaseRewriteFile, &leases_str) < 0)
+        goto cleanup;
+
+    rv = EXIT_SUCCESS;
+
+cleanup:
+    VIR_FREE(custom_lease_file);
+    virJSONValueFree(lease_new);
+    virJSONValueFree(leases_array);
+    virJSONValueFree(leases_array_new);
+    return rv;
+}
-- 
1.7.1


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