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[libvirt] [PATCH v2] 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".

The format of each lease is:
<expiry-time (epoch time)> <mac> <iaid> <ip-address> <hostname> <clientid>

Example of custom leases file content:
1385245780 52:54:00:2f:ba:76 * 192.168.150.153 * *
1385245781 52:54:00:2f:ba:76 3127926 2001:db8:ca2:2:1::6c * 00:04:76:00:cf:ae:b3:0b:fc:cd:0e:22:2e:97:76:65:74:ec
1385245964 52:54:00:44:7c:d7 * 192.168.150.219 iiit-ad885e4aa1 01:52:54:00:44:7c:d7
1385245964 52:54:00:44:7c:d7 * 192.168.150.219 * 01:52:54:00:44:7c:d7
1385246016 52:54:00:5d:99:92 * 192.168.150.212 iiit-ad885e4aa1 01:52:54:00:5d:99:92
1385246041 52:54:00:3b:16:e0 * 192.168.150.207 * *
1385246081 52:54:00:db:dd:98 * 192.168.150.234 * *
1385246088 52:54:00:db:dd:98 14409112 2001:db8:ca2:2:1::6d * 00:04:76:00:cf:ae:b3:0b:fc:cd:0e:22:2e:97:76:65:74:ec

---
 As danpb suggested, I have split the previous patch into helper program & API
 Refer: https://www.redhat.com/archives/libvir-list/2013-December/msg00694.html
 Once this get ACKed, I'll send in the patches for the Leases API v6

 src/Makefile.am             |  20 ++++
 src/network/bridge_driver.c |   4 +
 src/util/leaseshelper.c     | 225 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 249 insertions(+)
 create mode 100644 src/util/leaseshelper.c

diff --git a/src/Makefile.am b/src/Makefile.am
index 57e163f..6e5b03c 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -838,6 +838,9 @@ 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	\
@@ -2408,6 +2411,23 @@ libvirt_iohelper_CFLAGS = \
 		$(NULL)
 endif WITH_LIBVIRTD
 
+if WITH_LIBVIRTD
+libexec_PROGRAMS += libvirt_leaseshelper
+libvirt_leaseshelper_SOURCES = $(UTIL_LEASES_HELPER_SOURCES)
+libvirt_leaseshelper_LDFLAGS = \
+               $(NULL)
+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
 if WITH_LIBVIRTD
 libexec_PROGRAMS += libvirt_parthelper
diff --git a/src/network/bridge_driver.c b/src/network/bridge_driver.c
index 95e4b65..2278dba 100644
--- a/src/network/bridge_driver.c
+++ b/src/network/bridge_driver.c
@@ -1063,6 +1063,10 @@ networkBuildDhcpDaemonCommandLine(virNetworkObjPtr network,
 
     cmd = virCommandNew(dnsmasqCapsGetBinaryPath(caps));
     virCommandAddArgFormat(cmd, "--conf-file=%s", configfile);
+
+    /* This helper is used to create cutom 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..486ebe3
--- /dev/null
+++ b/src/util/leaseshelper.c
@@ -0,0 +1,225 @@
+/*
+ * leasehelper.c: Helper program to create custom leases file
+ *
+ * Copyright (C) 2013 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 "virutil.h"
+#include "virthread.h"
+#include "virfile.h"
+#include "virbuffer.h"
+#include "virstring.h"
+#include "virerror.h"
+#include "viralloc.h"
+#include "configmake.h"
+
+#define VIR_FROM_THIS VIR_FROM_NETWORK
+
+/**
+ * VIR_NETWORK_DHCP_LEASE_FIELDS:
+ *
+ * Macro providing the maximum number of fields in an entry in
+ * the leases file
+ */
+#define VIR_NETWORK_DHCP_LEASE_FIELDS 6
+/**
+ * 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 2097152
+
+/*
+ * Use this when passing possibly-NULL strings to printf-a-likes.
+ */
+# define EMPTY_STR(s) ((s) ? (s) : "*")
+
+int
+main(int argc, char **argv) {
+
+    /* Doesn't hurt to check */
+    if (argc < 4) {
+        /* Refer man page of dnsmasq --dhcp-script for more details */
+        fprintf(stderr, "Usage: $program $action ${mac|clientid} $ip\n");
+        return -1;
+    }
+
+    const char *program_name = argv[0];
+    const char *action = argv[1];
+    const char *interface = EMPTY_STR(virGetEnvAllowSUID("DNSMASQ_INTERFACE"));
+    const char *expirytime = EMPTY_STR(virGetEnvAllowSUID("DNSMASQ_LEASE_EXPIRES"));
+    const char *mac = argv[2];
+    const char *ip = argv[3];
+    const char *iaid = EMPTY_STR(virGetEnvAllowSUID("DNSMASQ_IAID"));
+    const char *hostname = EMPTY_STR(virGetEnvAllowSUID("DNSMASQ_SUPPLIED_HOSTNAME"));
+    const char *clientid = EMPTY_STR(virGetEnvAllowSUID("DNSMASQ_CLIENT_ID"));
+    const char *leases_str = NULL;
+    char *lease_file = NULL;
+    char *lease_entries = NULL;
+    char *lease_entry = NULL;
+    char **lease_fields = NULL;
+    bool delete = false;
+    bool add = false;
+    int rv = -1;
+    int lease_file_len = 0;
+    FILE *fp = NULL;
+    long long expirytime_tmp = 0;
+    virBuffer buf_new_lease = VIR_BUFFER_INITIALIZER;
+    virBuffer buf_all_leases = VIR_BUFFER_INITIALIZER;
+
+    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);
+    }
+
+    if (virAsprintf(&lease_file, "%s/%s.status", LOCALSTATEDIR
+                    "/lib/libvirt/dnsmasq/", interface) < 0)
+        goto cleanup;
+
+    if (virGetEnvAllowSUID("DNSMASQ_IAID")) {
+        mac = EMPTY_STR(virGetEnvAllowSUID("DNSMASQ_MAC"));
+        clientid = argv[2];
+    }
+
+    /* Make sure dnsmasq knows the interface, otherwise something is wrong */
+    if (STREQ(interface, "*"))
+        goto cleanup;
+
+    /* Make sure the file exists. If not, 'touch' it */
+    if (virFileTouch(lease_file, 0644) < 0)
+        goto cleanup;
+
+    /* Read entire contents */
+    if ((lease_file_len = virFileReadAll(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")) {
+                fprintf(stderr, "add|old\n");
+                add = true;
+                /* Enter new lease */
+                virBufferAsprintf(&buf_new_lease, "%s %s %s %s %s %s\n",
+                                  expirytime, mac, iaid, ip, hostname, clientid);
+
+                if (virBufferError(&buf_new_lease)) {
+                    virBufferFreeAndReset(&buf_new_lease);
+                    virReportOOMError();
+                    goto cleanup;
+                }
+            }
+        }
+    }
+
+    lease_entry = lease_entries[0] == '\0' ? NULL : lease_entries;
+
+    while (lease_entry) {
+        int nfields = 0;
+
+        char *eol = strchr(lease_entry, '\n');
+        *eol = '\0';
+
+        /* Split the lease line */
+        if (!(lease_fields = virStringSplit(lease_entry, " ",
+                                            VIR_NETWORK_DHCP_LEASE_FIELDS)))
+            goto cleanup;
+
+        nfields = virStringListLength(lease_fields);
+
+        /* Forward lease_entry to the next lease */
+        lease_entry = strchr(lease_entry, '\0');
+        if (lease_entry - lease_entries + 1 < lease_file_len)
+            lease_entry++;
+        else
+            lease_entry = NULL;
+
+        if (nfields != VIR_NETWORK_DHCP_LEASE_FIELDS)
+            goto cleanup;
+
+        if (virStrToLong_ll(lease_fields[0], NULL, 10, &expirytime_tmp) < 0) {
+            virReportError(VIR_ERR_INTERNAL_ERROR,
+                           _("Unable to convert lease expiry time to integer: %s"),
+                           lease_fields[0]);
+            goto cleanup;
+        }
+
+        /* Check whether lease has expired or not */
+        if (expirytime_tmp < (long long) time(NULL))
+            continue;
+        else if (delete && STREQ(lease_fields[3], ip))
+            continue;
+        else {
+            virBufferAsprintf(&buf_all_leases, "%s %s %s %s %s %s\n",
+                              lease_fields[0], lease_fields[1], lease_fields[2],
+                              lease_fields[3], lease_fields[4], lease_fields[5]);
+
+            if (virBufferError(&buf_all_leases)) {
+                virBufferFreeAndReset(&buf_all_leases);
+                virReportOOMError();
+                goto cleanup;
+            }
+        }
+    }
+
+    if (add) {
+        virBufferAsprintf(&buf_all_leases, "%s", virBufferContentAndReset(&buf_new_lease));
+
+        if (virBufferError(&buf_all_leases)) {
+            virBufferFreeAndReset(&buf_all_leases);
+            virReportOOMError();
+            goto cleanup;
+        }
+    }
+
+    rv = 0;
+
+    /* Write to file */
+    leases_str = virBufferContentAndReset(&buf_all_leases);
+    if (!leases_str)
+        leases_str = "";
+
+    if (virFileWriteStr(lease_file, leases_str, 0) < 0)
+        rv = -1;
+
+cleanup:
+    VIR_FREE(lease_file);
+    VIR_FREE(lease_entries);
+    if (lease_fields)
+        virStringFreeList(lease_fields);
+    return rv;
+}
-- 
1.8.1.4


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