[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

[libvirt] [PATCH V14 2/5] nwfilter: add DHCP snooping



This patch adds DHCP snooping support to libvirt. The learning method for
IP addresses is specified by setting the "CTRL_IP_LEARNING" variable to one of
"any" [default] (existing IP learning code), "none" (static only addresses)
or "dhcp" (DHCP snooping).

Active leases are saved in a lease file and reloaded on restart or HUP.

The following interface XML activates and uses the DHCP snooping:

    <interface type='bridge'>
      <source bridge='virbr0'/>
      <filterref filter='clean-traffic'>
        <parameter name='CTRL_IP_LEARNING' value='dhcp'/>
      </filterref>
    </interface>

All filters containing the variable 'IP' are automatically adjusted when
the VM receives an IP address via DHCP. However, multiple IP addresses per
interface are silently ignored in this patch, thus only supporting one IP
address per interface. Multiple IP address support is added in a later
patch in this series.

Signed-off-by: David L Stevens <dlstevens us ibm com>
Signed-off-by: Stefan Berger <stefanb linux vnet ibm com>

---

Changes since v12:
- use pcap_create to open pcap to be able to set smaller buffer
  than the 2 MB default buffer used by pcap which leads to processing
  of huge backlog of messages if flooding occurrs
- use virAtomicInc/Dec
- use indep. rate controllers, one per direction to tune out of
  flooding in each direction individually (even if flooding was to
  occur, libvirt doesn't use much CPU [0.3%])

Changes since v11:
- renamed ip_learning variable to CTRL_IP_LEARNING
- using virSocketAddr rather than uint32_t for IPv4 addresses
- don't submit packets to the worker thread that are below
  a reasonable size of a DHCP packet

Changes since v10:
- using 2 pcap captures now, one for incoming and one for outgoing traffic
  to prevent libvirt from picking up spoofed DHCP packets and adding bogus
  leases
- more cleanups on variable names

Changes since v9:
- introduced usage of thread pool for having a worker that evaluates the
  received DHCP packets and have it instantiate the new filters; it does
  more time consuming work while the 'normal' thread tries to maximies
  its time in libpcap packet capture function
- added rate limitation for evaluation of DCHP packets to prevent
  flooding the worker thread
- thread startup synchronization to avoid missing packets on a PXE-booting
  VM that may send DHCP packets early
- more work on documentation
- introducing #defines for reserved variable names

Changes since v8:
- naming consistency
- memory leaks
- if-before-free not being necessary
- separate shutdown function (for avoiding a valgrind reporting memory leak)
- a compilation error ("%d", strlen())
- pass NULL for a pointer rather than 0
- use common exits where possible
- make 'make syntax-check' pass
- due to a locking bug resulting in a deadlock reworked the locking and
  introduced a reference counter for the SnoopReq that must be held while
  the 'req' variable is accessed; it resulred in finer grained locking with
  the virNWFilterSnoopLock()
- improved on the documentation

Changes since v7:
- renamed functions as suggested
- collected local state into "virNWFilterSnoopState" struct
- cleaned up include file list
- misc code cleanups per review comments

---
 docs/formatnwfilter.html.in            |  143 +-
 po/POTFILES.in                         |    1 
 src/Makefile.am                        |    2 
 src/conf/nwfilter_params.h             |    5 
 src/nwfilter/nwfilter_dhcpsnoop.c      | 2166 +++++++++++++++++++++++++++++++++
 src/nwfilter/nwfilter_dhcpsnoop.h      |   39 
 src/nwfilter/nwfilter_driver.c         |    6 
 src/nwfilter/nwfilter_gentech_driver.c |   63 
 8 files changed, 2380 insertions(+), 45 deletions(-)
 create mode 100644 src/nwfilter/nwfilter_dhcpsnoop.c
 create mode 100644 src/nwfilter/nwfilter_dhcpsnoop.h

Index: libvirt-acl/docs/formatnwfilter.html.in
===================================================================
--- libvirt-acl.orig/docs/formatnwfilter.html.in
+++ libvirt-acl/docs/formatnwfilter.html.in
@@ -371,6 +371,118 @@
       Further, the notation of $VARIABLE is short-hand for $VARIABLE[ 0]  The
       former notation always assumes the iterator with Id '0'.
     <p>
+
+    <h3><a name="nwfelemsRulesAdvIPAddrDetection">Automatic IP address detection</a></h3>
+    <p>
+       The detection of IP addresses used on a virtual machine's interface
+       is automatically activated if the variable <code>IP</code> is referenced
+       but not value has been assigned to it.
+       <span class="since">Since 0.9.12</span>
+       the variable <code>CTRL_IP_LEARNING</code> can be used to specify
+       the IP address learning method to use. Valid values are <code>any</code>,
+       <code>dhcp</code>, or <code>none</code>.
+       <br/><br/>
+       The value <code>any</code> means that libvirt may use any packet to
+       determine the address in use by a virtual machine, which is the default
+       behavior if the variable <code>CTRL_IP_LEARNING</code> is not set. This method
+       will only detect a single IP address on an interface.
+       Once a VM's IP address has been detected, its IP network traffic
+       will be locked to that address, if for example IP address spoofing
+       is prevented by one of its filters. In that case the user of the VM
+       will not be able to change the IP address on the interface inside
+       the VM, which would be considered IP address spoofing.
+       When a VM is migrated to another host or resumed after a suspend operation,
+       the first packet sent by the VM will again determine the IP address it can
+       use on a particular interface.
+       <br/><br>
+       A value of <code>dhcp</code> specifies that libvirt should only honor DHCP
+       server-assigned addresses with valid leases. This method supports the detection
+       and usage of multiple IP address per interface.
+       When a VM is resumed after a suspend operation, still valid IP address leases
+       are applied to its filters. Otherwise the VM is expected to again use DHCP to obtain new
+       IP addresses. The migration of a VM to another physical host requires that
+       the VM again runs the DHCP protocol.
+       <br/><br/>
+       Use of <code>CTRL_IP_LEARNING=dhcp</code> (DHCP snooping) provides additional
+       anti-spoofing security, especially when combined with a filter allowing
+       only trusted DHCP servers to assign addresses. To enable this, set the
+       variable <code>DHCPSERVER</code> to the IP address of a valid DHCP server
+       and provide filters that use this variable to filter incoming DHCP responses.
+       <br/><br/>
+       When DHCP snooping is enabled and the DHCP lease expires,
+       the VM will no longer be able to use the IP address until it acquires a
+       new, valid lease from a DHCP server. If the VM is migrated, it must get
+       a new valid DHCP lease to use an IP address (e.g., by
+       bringing the VM interface down and up again).
+       <br/><br/>
+       Note that automatic DHCP detection listens to the DHCP traffic
+       the VM exchanges with the DHCP server of the infrastructure. To avoid
+       denial-of-service attacks on libvirt, the evaluation of those packets
+       is rate-limited, meaning that a VM sending an excessive number of DHCP
+       packets per second on an interface will not have all of those packets
+       evaluated and thus filters may not get adapted. Normal DHCP client
+       behavior is assumed to send a low number of DHCP packets per second.
+       Further, it is important to setup appropriate filters on all VMs in
+       the infrastructure to avoid them  being able to send DHCP
+       packets. Therefore VMs must either be prevented from sending UDP and TCP
+       traffic from port 67 to port 68 or the <code>DHCPSERVER</code>
+       variable should be used on all VMs to restrict DHCP server messages to
+       only be allowed to originate from trusted DHCP servers. At the same
+       time anti-spoofing prevention must be enabled on all VMs in the subnet.
+       <br/><br/>
+       If <code>CTRL_IP_LEARNING</code> is set to <code>none</code>, libvirt does not do
+       IP address learning and referencing <code>IP</code> without assigning it an
+       explicit value is an error.
+       <br/><br/>
+       The following XML provides an example for the activation of IP address learning
+       using the DHCP snooping method:
+    </p>
+<pre>
+    &lt;interface type='bridge'&gt;
+      &lt;source bridge='virbr0'/&gt;
+      &lt;filterref filter='clean-traffic'&gt;
+        &lt;parameter name='CTRL_IP_LEARNING' value='dhcp'/&gt;
+      &lt;/filterref&gt;
+    &lt;/interface&gt;
+</pre>
+
+    <h3><a name="nwfelemsReservedVars">Reserved Variables</a></h3>
+    <p>
+      The following table lists reserved variables in use by libvirt.
+    </p>
+      <table class="top_table">
+       <tr>
+         <th> Variable Name </th>
+         <th> Semantics </th>
+       </tr>
+       <tr>
+         <td> MAC </td>
+         <td> The MAC address of the interface </td>
+       </tr>
+       <tr>
+         <td> IP </td>
+         <td> The list of IP addresses in use by an interface </td>
+       </tr>
+       <tr>
+         <td> IPV6 </td>
+         <td> Not currently implemented:
+              the list of IPV6 addresses in use by an interface </td>
+       </tr>
+       <tr>
+         <td> DHCPSERVER </td>
+         <td> The list of IP addresses of trusted DHCP servers</td>
+       </tr>
+       <tr>
+         <td> DHCPSERVERV6 </td>
+         <td> Not currently implemented:
+              The list of IPv6 addresses of trusted DHCP servers</td>
+       </tr>
+       <tr>
+         <td> CTRL_IP_LEARNING </td>
+         <td> The choice of the IP address detection mode </td>
+       </tr>
+      </table>
+
     <h2><a name="nwfelems">Element and attribute overview</a></h2>
 
     <p>
@@ -1694,6 +1806,7 @@
      The following sections discuss advanced filter configuration
      topics.
     </p>
+
     <h4><a name="nwfelemsRulesAdvTracking">Connection tracking</a></h4>
     <p>
      The network filtering subsystem (on Linux) makes use of the connection
@@ -2226,36 +2339,6 @@
      filtering subsystem.
     </p>
 
-    <h3><a name="nwflimitsIP">IP Address Detection</a></h3>
-     <p>
-       In case a network filter references the variable
-       <i>IP</i> and no variable was defined in any higher layer
-       references to the filter, IP address detection will automatically
-       be started when the filter is to be instantiated (VM start, interface
-       hotplug event). Only IPv4
-       addresses can be detected and only a single IP address
-       legitimately in use by a VM on a single interface will be detected.
-       In case a VM was to use multiple IP address on a single interface
-       (IP aliasing),
-       the IP addresses would have to be provided explicitly either
-       in the network filter itself or as variables used in attributes'
-       values. These
-       variables must then be defined in a higher level reference to the filter
-       and each assigned the value of the IP address that the VM is expected
-       to be using.
-       Different IP addresses in use by multiple interfaces of a VM
-       (one IP address each) will be independently detected.
-       <br/><br/>
-       Once a VM's IP address has been detected, its IP network traffic
-       may be locked to that address, if for example IP address spoofing
-       is prevented by one of its filters. In that case the user of the VM
-       will not be able to change the IP address on the interface inside
-       the VM, which would be considered IP address spoofing.
-       <br/><br/>
-       In case a VM is resumed after suspension or migrated, IP address
-       detection will be restarted.
-     </p>
-
     <h3><a name="nwflimitsmigr">VM Migration</a></h3>
      <p>
       VM migration is only supported if the whole filter tree
Index: libvirt-acl/src/Makefile.am
===================================================================
--- libvirt-acl.orig/src/Makefile.am
+++ libvirt-acl/src/Makefile.am
@@ -511,6 +511,8 @@ NWFILTER_DRIVER_SOURCES =					\
 		nwfilter/nwfilter_driver.h nwfilter/nwfilter_driver.c	\
 		nwfilter/nwfilter_gentech_driver.c			\
 		nwfilter/nwfilter_gentech_driver.h			\
+		nwfilter/nwfilter_dhcpsnoop.c				\
+		nwfilter/nwfilter_dhcpsnoop.h				\
 		nwfilter/nwfilter_ebiptables_driver.c			\
 		nwfilter/nwfilter_ebiptables_driver.h			\
 		nwfilter/nwfilter_learnipaddr.c				\
Index: libvirt-acl/src/nwfilter/nwfilter_dhcpsnoop.c
===================================================================
--- /dev/null
+++ libvirt-acl/src/nwfilter/nwfilter_dhcpsnoop.c
@@ -0,0 +1,2166 @@
+/*
+ * nwfilter_dhcpsnoop.c: support for DHCP snooping used by a VM
+ *                       on an interface
+ *
+ * Copyright (C) 2011,2012 IBM Corp.
+ *
+ * Authors:
+ *    David L Stevens <dlstevens us ibm com>
+ *    Stefan Berger <stefanb linux vnet ibm com>
+ *
+ * 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307  USA
+ *
+ * Based in part on work by Stefan Berger <stefanb us ibm com>
+ */
+
+/*
+ * Note about testing:
+ *   On the host run in a shell:
+ *      while :; do kill -SIGHUP `pidof libvirtd` ; echo "HUP $RANDOM"; sleep 20; done
+ *
+ *   Inside a couple of VMs that for example use the 'clean-traffic' filter:
+ *      while :; do kill -SIGTERM `pidof dhclient`; dhclient eth0 ; ifconfig eth0; done
+ *
+ *   On the host check the lease file and that it's periodically shortened:
+ *      cat /var/run/libvirt/network/nwfilter.leases ; date +%s
+ *
+ *   On the host also check that the ebtables rules 'look' ok:
+ *      ebtables -t nat -L
+ */
+#include <config.h>
+
+#ifdef HAVE_LIBPCAP
+# include <pcap.h>
+#endif
+
+#include <fcntl.h>
+
+#include <arpa/inet.h>
+#include <netinet/ip.h>
+#include <netinet/udp.h>
+#include <net/if.h>
+
+#include "memory.h"
+#include "logging.h"
+#include "datatypes.h"
+#include "virterror_internal.h"
+#include "conf/domain_conf.h"
+#include "nwfilter_gentech_driver.h"
+#include "nwfilter_dhcpsnoop.h"
+#include "virnetdev.h"
+#include "virfile.h"
+#include "viratomic.h"
+#include "threadpool.h"
+#include "configmake.h"
+#include "virtime.h"
+
+#define VIR_FROM_THIS VIR_FROM_NWFILTER
+
+#ifdef HAVE_LIBPCAP
+
+# define LEASEFILE LOCALSTATEDIR "/run/libvirt/network/nwfilter.leases"
+# define TMPLEASEFILE LOCALSTATEDIR "/run/libvirt/network/nwfilter.ltmp"
+
+struct virNWFilterSnoopState {
+    /* lease file */
+    int                  leaseFD;
+    virAtomicInt         nLeases; /* number of active leases */
+    virAtomicInt         wLeases; /* number of written leases */
+    virAtomicInt         nThreads; /* number of running threads */
+    /* thread management */
+    virHashTablePtr      snoopReqs;
+    virHashTablePtr      ifnameToKey;
+    virMutex             snoopLock;  /* protects SnoopReqs and IfNameToKey */
+    virHashTablePtr      active;
+    virMutex             activeLock; /* protects Active */
+};
+
+# define virNWFilterSnoopLock() \
+    do { \
+        virMutexLock(&virNWFilterSnoopState.snoopLock); \
+    } while (0);
+# define virNWFilterSnoopUnlock() \
+    do { \
+        virMutexUnlock(&virNWFilterSnoopState.snoopLock); \
+    } while (0);
+# define virNWFilterSnoopActiveLock() \
+    do { \
+        virMutexLock(&virNWFilterSnoopState.activeLock); \
+    } while (0);
+# define virNWFilterSnoopActiveUnlock() \
+    do { \
+        virMutexUnlock(&virNWFilterSnoopState.activeLock); \
+    } while (0);
+
+# define VIR_IFKEY_LEN   ((VIR_UUID_STRING_BUFLEN) + (VIR_MAC_STRING_BUFLEN))
+
+typedef struct _virNWFilterSnoopReq virNWFilterSnoopReq;
+typedef virNWFilterSnoopReq *virNWFilterSnoopReqPtr;
+
+typedef struct _virNWFilterSnoopIPLease virNWFilterSnoopIPLease;
+typedef virNWFilterSnoopIPLease *virNWFilterSnoopIPLeasePtr;
+
+typedef enum {
+    THREAD_STATUS_NONE,
+    THREAD_STATUS_OK,
+    THREAD_STATUS_FAIL,
+} virNWFilterSnoopThreadStatus;
+
+struct _virNWFilterSnoopReq {
+    /*
+     * reference counter: while the req is on the
+     * publicSnoopReqs hash, the refctr may only
+     * be modified with the SnoopLock held
+     */
+    virAtomicInt                         refctr;
+
+    virNWFilterTechDriverPtr             techdriver;
+    char                                *ifname;
+    int                                  ifindex;
+    const char                          *linkdev;
+    enum virDomainNetType                nettype;
+    char                                 ifkey[VIR_IFKEY_LEN];
+    virMacAddr                           macaddr;
+    const char                          *filtername;
+    virNWFilterHashTablePtr              vars;
+    virNWFilterDriverStatePtr            driver;
+    /* start and end of lease list, ordered by lease time */
+    virNWFilterSnoopIPLeasePtr           start;
+    virNWFilterSnoopIPLeasePtr           end;
+    char                                *threadkey;
+
+    virNWFilterSnoopThreadStatus         threadStatus;
+    virCond                              threadStatusCond;
+
+    int                                  jobCompletionStatus;
+    /* the number of submitted jobs in the worker's queue */
+    /*
+     * protect those members that can change while the
+     * req is on the public SnoopReq hash and
+     * at least one reference is held:
+     * - ifname
+     * - threadkey
+     * - start
+     * - end
+     * - a lease while it is on the list
+     * - threadStatus
+     * (for refctr, see above)
+     */
+    virMutex                             lock;
+};
+
+/*
+ * Note about lock-order:
+ * 1st: virNWFilterSnoopLock()
+ * 2nd: virNWFilterSnoopReqLock(req)
+ *
+ * Rationale: Former protects the SnoopReqs hash, latter its contents
+ */
+
+struct _virNWFilterSnoopIPLease {
+    virSocketAddr              ipAddress;
+    virSocketAddr              ipServer;
+    virNWFilterSnoopReqPtr     snoopReq;
+    unsigned int               timeout;
+    /* timer list */
+    virNWFilterSnoopIPLeasePtr prev;
+    virNWFilterSnoopIPLeasePtr next;
+};
+
+typedef struct _virNWFilterSnoopEthHdr virNWFilterSnoopEthHdr;
+typedef virNWFilterSnoopEthHdr *virNWFilterSnoopEthHdrPtr;
+
+struct _virNWFilterSnoopEthHdr {
+    virMacAddr eh_dst;
+    virMacAddr eh_src;
+    uint16_t eh_type;
+    uint8_t eh_data[];
+} ATTRIBUTE_PACKED;
+
+typedef struct _virNWFilterSnoopDHCPHdr virNWFilterSnoopDHCPHdr;
+typedef virNWFilterSnoopDHCPHdr *virNWFilterSnoopDHCPHdrPtr;
+
+struct _virNWFilterSnoopDHCPHdr {
+    uint8_t   d_op;
+    uint8_t   d_htype;
+    uint8_t   d_hlen;
+    uint8_t   d_hops;
+    uint32_t  d_xid;
+    uint16_t  d_secs;
+    uint16_t  d_flags;
+    uint32_t  d_ciaddr;
+    uint32_t  d_yiaddr;
+    uint32_t  d_siaddr;
+    uint32_t  d_giaddr;
+    uint8_t   d_chaddr[16];
+    char      d_sname[64];
+    char      d_file[128];
+    uint8_t   d_opts[];
+} ATTRIBUTE_PACKED;
+
+/* DHCP options */
+
+# define DHCPO_PAD         0
+# define DHCPO_LEASE      51     /* lease time in secs */
+# define DHCPO_MTYPE      53     /* message type */
+# define DHCPO_END       255     /* end of options */
+
+/* DHCP message types */
+# define DHCPDECLINE     4
+# define DHCPACK         5
+# define DHCPRELEASE     7
+
+# define MIN_VALID_DHCP_PKT_SIZE \
+    (offsetof(virNWFilterSnoopEthHdr, eh_data) + \
+     sizeof(struct udphdr) + \
+     offsetof(virNWFilterSnoopDHCPHdr, d_opts))
+
+# define PCAP_PBUFSIZE              576 /* >= IP/TCP/DHCP headers */
+# define PCAP_READ_MAXERRS          25 /* retries on failing device */
+# define PCAP_FLOOD_TIMEOUT_MS      10 /* ms */
+
+typedef struct _virNWFilterDHCPDecodeJob virNWFilterDHCPDecodeJob;
+typedef virNWFilterDHCPDecodeJob *virNWFilterDHCPDecodeJobPtr;
+
+struct _virNWFilterDHCPDecodeJob {
+    unsigned char packet[PCAP_PBUFSIZE];
+    int caplen;
+    bool fromVM;
+    virAtomicIntPtr qCtr;
+};
+
+# define DHCP_PKT_RATE          10 /* pkts/sec */
+# define DHCP_PKT_BURST         50 /* pkts/sec */
+# define DHCP_BURST_INTERVAL_S  10 /* sec */
+
+# define PCAP_BUFFERSIZE        (DHCP_PKT_BURST * PCAP_PBUFSIZE / 2)
+
+# define MAX_QUEUED_JOBS        (DHCP_PKT_BURST + 2 * DHCP_PKT_RATE)
+
+typedef struct _virNWFilterSnoopRateLimitConf virNWFilterSnoopRateLimitConf;
+typedef virNWFilterSnoopRateLimitConf *virNWFilterSnoopRateLimitConfPtr;
+
+struct _virNWFilterSnoopRateLimitConf {
+    time_t prev;
+    unsigned int pkt_ctr;
+    time_t burst;
+    const unsigned int rate;
+    const unsigned int burstRate;
+    const unsigned int burstInterval;
+};
+
+typedef struct _virNWFilterSnoopPcapConf virNWFilterSnoopPcapConf;
+typedef virNWFilterSnoopPcapConf *virNWFilterSnoopPcapConfPtr;
+
+struct _virNWFilterSnoopPcapConf {
+    pcap_t *handle;
+    const pcap_direction_t dir;
+    const char *filter;
+    virNWFilterSnoopRateLimitConf rateLimit; /* indep. rate limiters */
+    virAtomicInt qCtr; /* number of jobs in the worker's queue */
+    const unsigned int maxQSize;
+    unsigned long long penaltyTimeoutAbs;
+};
+
+/* local function prototypes */
+static int virNWFilterSnoopReqLeaseDel(virNWFilterSnoopReqPtr req,
+                                       virSocketAddrPtr ipaddr,
+                                       bool update_leasefile);
+
+static void virNWFilterSnoopReqLock(virNWFilterSnoopReqPtr req);
+static void virNWFilterSnoopReqUnlock(virNWFilterSnoopReqPtr req);
+
+static void virNWFilterSnoopLeaseFileLoad(void);
+static void virNWFilterSnoopLeaseFileSave(virNWFilterSnoopIPLeasePtr ipl);
+
+/* local variables */
+static struct virNWFilterSnoopState virNWFilterSnoopState = {
+    .leaseFD = -1,
+};
+
+static const unsigned char dhcp_magic[4] = { 99, 130, 83, 99 };
+
+
+static char *
+virNWFilterSnoopActivate(virNWFilterSnoopReqPtr req)
+{
+    char *key;
+
+    if (virAsprintf(&key, "%p-%d", req, req->ifindex) < 0) {
+        virReportOOMError();
+        return NULL;
+    }
+
+    virNWFilterSnoopActiveLock();
+
+    if (virHashAddEntry(virNWFilterSnoopState.active, key, (void *)0x1) < 0) {
+        VIR_FREE(key);
+    }
+
+    virNWFilterSnoopActiveUnlock();
+
+    return key;
+}
+
+static void
+virNWFilterSnoopCancel(char **threadKey)
+{
+    if (*threadKey == NULL)
+        return;
+
+    virNWFilterSnoopActiveLock();
+
+    (void) virHashRemoveEntry(virNWFilterSnoopState.active, *threadKey);
+    VIR_FREE(*threadKey);
+
+    virNWFilterSnoopActiveUnlock();
+}
+
+static bool
+virNWFilterSnoopIsActive(char *threadKey)
+{
+    void *entry;
+
+    if (threadKey == NULL)
+        return 0;
+
+    virNWFilterSnoopActiveLock();
+
+    entry = virHashLookup(virNWFilterSnoopState.active, threadKey);
+
+    virNWFilterSnoopActiveUnlock();
+
+    return entry != NULL;
+}
+
+/*
+ * virNWFilterSnoopListAdd - add an IP lease to a list
+ */
+static void
+virNWFilterSnoopListAdd(virNWFilterSnoopIPLeasePtr plnew,
+                        virNWFilterSnoopIPLeasePtr *start,
+                        virNWFilterSnoopIPLeasePtr *end)
+{
+    virNWFilterSnoopIPLeasePtr pl;
+
+    plnew->next = plnew->prev = NULL;
+
+    if (!*start) {
+        *start = *end = plnew;
+        return;
+    }
+
+    for (pl = *end; pl && plnew->timeout < pl->timeout;
+         pl = pl->prev)
+        /* empty */ ;
+
+    if (!pl) {
+        plnew->next = *start;
+        *start = plnew;
+    } else {
+        plnew->next = pl->next;
+        pl->next = plnew;
+    }
+
+    plnew->prev = pl;
+
+    if (plnew->next)
+        plnew->next->prev = plnew;
+    else
+        *end = plnew;
+}
+
+/*
+ * virNWFilterSnoopListDel - remove an IP lease from a list
+ */
+static void
+virNWFilterSnoopListDel(virNWFilterSnoopIPLeasePtr ipl,
+                        virNWFilterSnoopIPLeasePtr *start,
+                        virNWFilterSnoopIPLeasePtr *end)
+{
+    if (ipl->prev)
+        ipl->prev->next = ipl->next;
+    else
+        *start = ipl->next;
+
+    if (ipl->next)
+        ipl->next->prev = ipl->prev;
+    else
+        *end = ipl->prev;
+
+    ipl->next = ipl->prev = NULL;
+}
+
+/*
+ * virNWFilterSnoopLeaseTimerAdd - add an IP lease to the timer list
+ */
+static void
+virNWFilterSnoopIPLeaseTimerAdd(virNWFilterSnoopIPLeasePtr plnew)
+{
+    virNWFilterSnoopReqPtr req = plnew->snoopReq;
+
+    /* protect req->start / req->end */
+    virNWFilterSnoopReqLock(req);
+
+    virNWFilterSnoopListAdd(plnew, &req->start, &req->end);
+
+    virNWFilterSnoopReqUnlock(req);
+}
+
+/*
+ * virNWFilterSnoopLeaseTimerDel - remove an IP lease from the timer list
+ */
+static void
+virNWFilterSnoopIPLeaseTimerDel(virNWFilterSnoopIPLeasePtr ipl)
+{
+    virNWFilterSnoopReqPtr req = ipl->snoopReq;
+
+    /* protect req->start / req->end */
+    virNWFilterSnoopReqLock(req);
+
+    virNWFilterSnoopListDel(ipl, &req->start, &req->end);
+
+    virNWFilterSnoopReqUnlock(req);
+
+    ipl->timeout = 0;
+}
+
+/*
+ * virNWFilterSnoopInstallRule - install rule for a lease
+ *
+ * @instantiate: when calling this function in a loop, indicate
+ *               the last call with 'true' here so that the
+ *               rules all get instantiated
+ *               Always calling this with 'true' is fine, but less
+ *               efficient.
+ */
+static int
+virNWFilterSnoopIPLeaseInstallRule(virNWFilterSnoopIPLeasePtr ipl,
+                                   bool instantiate)
+{
+    char *ipaddr;
+    int rc = -1;
+    virNWFilterVarValuePtr ipVar;
+    virNWFilterSnoopReqPtr req;
+
+    ipaddr = virSocketAddrFormat(&ipl->ipAddress);
+    if (!ipaddr)
+        return -1;
+
+    ipVar = virNWFilterVarValueCreateSimple(ipaddr);
+    if (!ipVar)
+        goto cleanup;
+
+    ipaddr = NULL; /* belongs to ipVar now */
+
+    req = ipl->snoopReq;
+
+    /* protect req->ifname and req->vars */
+    virNWFilterSnoopReqLock(req);
+
+    if (virNWFilterHashTablePut(req->vars, NWFILTER_VARNAME_IP,
+                                ipVar, 1) < 0) {
+        virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                               _("Could not add variable \""
+                                 NWFILTER_VARNAME_IP "\" to hashmap"));
+        virNWFilterVarValueFree(ipVar);
+        goto exit_snooprequnlock;
+    }
+
+    if (!instantiate) {
+        rc = 0;
+        goto exit_snooprequnlock;
+    }
+
+    /* instantiate the filters */
+
+    if (req->ifname)
+        rc = virNWFilterInstantiateFilterLate(NULL,
+                                              req->ifname,
+                                              req->ifindex,
+                                              req->linkdev,
+                                              req->nettype,
+                                              req->macaddr,
+                                              req->filtername,
+                                              req->vars,
+                                              req->driver);
+
+exit_snooprequnlock:
+    virNWFilterSnoopReqUnlock(req);
+
+cleanup:
+    VIR_FREE(ipaddr);
+
+    return rc;
+}
+
+/*
+ * virNWFilterSnoopIPLeaseUpdate - update the timeout on an IP lease
+ */
+static void
+virNWFilterSnoopIPLeaseUpdate(virNWFilterSnoopIPLeasePtr ipl, time_t timeout)
+{
+    if (timeout < ipl->timeout)
+        return;  /* no take-backs */
+
+    virNWFilterSnoopIPLeaseTimerDel(ipl);
+    ipl->timeout = timeout;
+    virNWFilterSnoopIPLeaseTimerAdd(ipl);
+}
+
+/*
+ * virNWFilterSnoopGetByIP - lookup IP lease by IP address
+ */
+static virNWFilterSnoopIPLeasePtr
+virNWFilterSnoopIPLeaseGetByIP(virNWFilterSnoopIPLeasePtr start,
+                               virSocketAddrPtr ipaddr)
+{
+    virNWFilterSnoopIPLeasePtr pl;
+
+    for (pl = start;
+         pl && !virSocketAddrEqual(&pl->ipAddress, ipaddr);
+         pl = pl->next)
+        /* empty */ ;
+    return pl;
+}
+
+/*
+ * virNWFilterSnoopReqLeaseTimerRun - run the IP lease timeout list
+ */
+static unsigned int
+virNWFilterSnoopReqLeaseTimerRun(virNWFilterSnoopReqPtr req)
+{
+    time_t now = time(0);
+
+    /* protect req->start */
+    virNWFilterSnoopReqLock(req);
+
+    while (req->start && req->start->timeout <= now)
+        virNWFilterSnoopReqLeaseDel(req, &req->start->ipAddress, true);
+
+    virNWFilterSnoopReqUnlock(req);
+
+    return 0;
+}
+
+/*
+ * Get a reference to the given Snoop request
+ */
+static void
+virNWFilterSnoopReqGet(virNWFilterSnoopReqPtr req)
+{
+    virAtomicIntInc(&req->refctr);
+}
+
+/*
+ * Create a new Snoop request. Initialize it with the given
+ * interface key. The caller must release the request with a call
+ * to virNWFilerSnoopReqPut(req).
+ */
+static virNWFilterSnoopReqPtr
+virNWFilterSnoopReqNew(const char *ifkey)
+{
+    virNWFilterSnoopReqPtr req;
+
+    if (ifkey == NULL || strlen(ifkey) != VIR_IFKEY_LEN - 1) {
+        virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                               _("virNWFilterSnoopReqNew called with invalid "
+                                 "key \"%s\" (%u)"),
+                               ifkey ? ifkey : "",
+                               (unsigned int)strlen(ifkey));
+        return NULL;
+    }
+
+    if (VIR_ALLOC(req) < 0) {
+        virReportOOMError();
+        return NULL;
+    }
+
+    req->threadStatus = THREAD_STATUS_NONE;
+
+    if (virAtomicIntInit(&req->refctr) < 0 ||
+        virStrcpyStatic(req->ifkey, ifkey) == NULL ||
+        virMutexInitRecursive(&req->lock) < 0)
+        goto err_free_req;
+
+    if (virCondInit(&req->threadStatusCond) < 0)
+        goto err_destroy_mutex;
+
+    virNWFilterSnoopReqGet(req);
+
+    return req;
+
+err_destroy_mutex:
+    virMutexDestroy(&req->lock);
+
+err_free_req:
+    VIR_FREE(req);
+
+    return NULL;
+}
+
+/*
+ * Free a snoop request unless it is still referenced.
+ * All its associated leases are also freed.
+ * The lease file is NOT rewritten.
+ */
+static void
+virNWFilterSnoopReqFree(virNWFilterSnoopReqPtr req)
+{
+    virNWFilterSnoopIPLeasePtr ipl;
+
+    if (!req)
+        return;
+
+    if (virAtomicIntRead(&req->refctr) != 0)
+        return;
+
+    /* free all leases */
+    for (ipl = req->start; ipl; ipl = req->start)
+        virNWFilterSnoopReqLeaseDel(req, &ipl->ipAddress, false);
+
+    /* free all req data */
+    VIR_FREE(req->ifname);
+    VIR_FREE(req->linkdev);
+    VIR_FREE(req->filtername);
+    virNWFilterHashTableFree(req->vars);
+
+    virMutexDestroy(&req->lock);
+    ignore_value(virCondDestroy(&req->threadStatusCond));
+
+    VIR_FREE(req);
+}
+
+/*
+ * Lock a Snoop request 'req'
+ */
+static void
+virNWFilterSnoopReqLock(virNWFilterSnoopReqPtr req)
+{
+    virMutexLock(&req->lock);
+}
+
+/*
+ * Unlock a Snoop request 'req'
+ */
+static void
+virNWFilterSnoopReqUnlock(virNWFilterSnoopReqPtr req)
+{
+    virMutexUnlock(&req->lock);
+}
+
+/*
+ * virNWFilterSnoopReqRelease - hash table free function to kill a request
+ */
+static void
+virNWFilterSnoopReqRelease(void *req0, const void *name ATTRIBUTE_UNUSED)
+{
+    virNWFilterSnoopReqPtr req = req0;
+
+    if (!req)
+        return;
+
+    /* protect req->threadkey */
+    virNWFilterSnoopReqLock(req);
+
+    if (req->threadkey)
+        virNWFilterSnoopCancel(&req->threadkey);
+
+    virNWFilterSnoopReqUnlock(req);
+
+    virNWFilterSnoopReqFree(req);
+}
+
+/*
+ * virNWFilterSnoopReqGetByIFKey
+ *
+ * Get a Snoop request given an interface key; caller must release
+ * the Snoop request with a call to virNWFilterSnoopReqPut()
+ */
+static virNWFilterSnoopReqPtr
+virNWFilterSnoopReqGetByIFKey(const char *ifkey)
+{
+    virNWFilterSnoopReqPtr req;
+
+    virNWFilterSnoopLock();
+
+    req = virHashLookup(virNWFilterSnoopState.snoopReqs, ifkey);
+    if (req)
+        virNWFilterSnoopReqGet(req);
+
+    virNWFilterSnoopUnlock();
+
+    return req;
+}
+
+/*
+ * Drop the reference to the Snoop request. Don't use the req
+ * after this call.
+ */
+static void
+virNWFilterSnoopReqPut(virNWFilterSnoopReqPtr req)
+{
+    if (!req)
+        return;
+
+    virNWFilterSnoopLock();
+
+    if (virAtomicIntDec(&req->refctr) == 0) {
+        /*
+         * delete the request:
+         * - if we don't find req on the global list anymore
+         *   (this happens during SIGHUP)
+         * we would keep the request:
+         * - if we still have a valid lease, keep the req for restarts
+         */
+        if (virHashLookup(virNWFilterSnoopState.snoopReqs, req->ifkey) != req) {
+            virNWFilterSnoopReqRelease(req, NULL);
+        } else if (!req->start || req->start->timeout < time(0)) {
+            (void) virHashRemoveEntry(virNWFilterSnoopState.snoopReqs,
+                                      req->ifkey);
+        }
+    }
+
+    virNWFilterSnoopUnlock();
+}
+
+/*
+ * virNWFilterSnoopReqLeaseAdd - create or update an IP lease
+ */
+static int
+virNWFilterSnoopReqLeaseAdd(virNWFilterSnoopReqPtr req,
+                            virNWFilterSnoopIPLeasePtr plnew,
+                            bool update_leasefile)
+{
+    virNWFilterSnoopIPLeasePtr pl;
+
+    plnew->snoopReq = req;
+
+    /* protect req->start and the lease */
+    virNWFilterSnoopReqLock(req);
+
+    pl = virNWFilterSnoopIPLeaseGetByIP(req->start, &plnew->ipAddress);
+
+    if (pl) {
+        virNWFilterSnoopIPLeaseUpdate(pl, plnew->timeout);
+
+        virNWFilterSnoopReqUnlock(req);
+
+        goto exit;
+    }
+
+    virNWFilterSnoopReqUnlock(req);
+
+    /* support for multiple addresses requires the ability to add filters
+     * to existing chains, or to instantiate address lists via
+     * virNWFilterInstantiateFilterLate(). Until one of those capabilities
+     * is added, don't allow a new address when one is already assigned to
+     * this interface.
+     */
+    if (req->start)
+        return 0;    /* silently ignore multiple addresses */
+
+    if (VIR_ALLOC(pl) < 0) {
+        virReportOOMError();
+        return -1;
+    }
+    *pl = *plnew;
+
+    /* protect req->threadkey */
+    virNWFilterSnoopReqLock(req);
+
+    if (req->threadkey && virNWFilterSnoopIPLeaseInstallRule(pl, true) < 0) {
+        virNWFilterSnoopReqUnlock(req);
+        VIR_FREE(pl);
+        return -1;
+    }
+
+    virNWFilterSnoopReqUnlock(req);
+
+    /* put the lease on the req's list */
+    virNWFilterSnoopIPLeaseTimerAdd(pl);
+
+    virAtomicIntInc(&virNWFilterSnoopState.nLeases);
+
+exit:
+    if (update_leasefile)
+        virNWFilterSnoopLeaseFileSave(pl);
+
+    return 0;
+}
+
+/*
+ * Restore a Snoop request -- walk its list of leases
+ * and re-build the filtering rules with them
+ */
+static int
+virNWFilterSnoopReqRestore(virNWFilterSnoopReqPtr req)
+{
+    int ret = 0;
+    virNWFilterSnoopIPLeasePtr ipl;
+
+    /* protect req->start */
+    virNWFilterSnoopReqLock(req);
+
+    for (ipl = req->start; ipl; ipl = ipl->next) {
+        /* instantiate the rules at the last lease */
+        bool is_last = (ipl->next == NULL);
+        if (virNWFilterSnoopIPLeaseInstallRule(ipl, is_last) < 0) {
+            ret = -1;
+            break;
+        }
+    }
+
+    virNWFilterSnoopReqUnlock(req);
+
+    return ret;
+}
+
+/*
+ * virNWFilterSnoopReqLeaseDel - delete an IP lease
+ *
+ * @update_leasefile: set to 'true' if the lease expired or the lease
+ *                    was returned to the DHCP server and therefore
+ *                    this has to be noted in the lease file.
+ *                    set to 'false' for any other reason such as for
+ *                    example when calling only to free the lease's
+ *                    memory or when calling this function while reading
+ *                    leases from the file.
+ *
+ * Returns 0 on success, -1 if the instantiation of the rules failed
+ */
+static int
+virNWFilterSnoopReqLeaseDel(virNWFilterSnoopReqPtr req,
+                            virSocketAddrPtr ipaddr, bool update_leasefile)
+{
+    int ret = 0;
+    virNWFilterSnoopIPLeasePtr ipl;
+
+    /* protect req->start & req->ifname */
+    virNWFilterSnoopReqLock(req);
+
+    ipl = virNWFilterSnoopIPLeaseGetByIP(req->start, ipaddr);
+    if (ipl == NULL)
+        goto lease_not_found;
+
+    virNWFilterSnoopIPLeaseTimerDel(ipl);
+
+    if (update_leasefile) {
+        const virNWFilterVarValuePtr dhcpsrvrs =
+            virHashLookup(req->vars->hashTable, NWFILTER_VARNAME_DHCPSERVER);
+
+        virNWFilterSnoopLeaseFileSave(ipl);
+
+        /*
+         * for multiple address support, this needs to remove those rules
+         * referencing "IP" with ipl's ip value.
+         */
+        if (req->techdriver &&
+            req->techdriver->applyDHCPOnlyRules(req->ifname, req->macaddr,
+                                                dhcpsrvrs, false) < 0) {
+            virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                                   _("virNWFilterSnoopListDel failed"));
+            ret = -1;
+        }
+
+    }
+    VIR_FREE(ipl);
+
+    virAtomicIntDec(&virNWFilterSnoopState.nLeases);
+
+lease_not_found:
+    virNWFilterSnoopReqUnlock(req);
+
+    return ret;
+}
+
+static int
+virNWFilterSnoopDHCPGetOpt(virNWFilterSnoopDHCPHdrPtr pd, int len,
+                           int *pmtype, int *pleasetime)
+{
+    int oind, olen;
+    int oend;
+    uint32_t nwint;
+
+    olen = len - sizeof(*pd);
+    oind = 0;
+
+    if (olen < 4)               /* bad magic */
+        return -1;
+
+    if (memcmp(dhcp_magic, pd->d_opts, sizeof(dhcp_magic)) != 0)
+        return -1;              /* bad magic */
+
+    oind += sizeof(dhcp_magic);
+
+    oend = 0;
+
+    *pmtype = *pleasetime = 0;
+
+    while (oind < olen) {
+        switch (pd->d_opts[oind]) {
+        case DHCPO_LEASE:
+            if (olen - oind < 6)
+                goto malformed;
+            if (*pleasetime)
+                return -1;  /* duplicate lease time */
+            memcpy(&nwint, (char *)pd->d_opts + oind + 2, sizeof(nwint));
+            *pleasetime = ntohl(nwint);
+            break;
+        case DHCPO_MTYPE:
+            if (olen - oind < 3)
+                goto malformed;
+            if (*pmtype)
+                return -1;  /* duplicate message type */
+            *pmtype = pd->d_opts[oind + 2];
+            break;
+        case DHCPO_PAD:
+            oind++;
+            continue;
+        case DHCPO_END:
+            oend = 1;
+            break;
+        default:
+            if (olen - oind < 2)
+                goto malformed;
+        }
+        if (oend)
+            break;
+        oind += pd->d_opts[oind + 1] + 2;
+    }
+    return 0;
+malformed:
+    VIR_WARN("got lost in the options!");
+    return -1;
+}
+
+/*
+ * Decode the DHCP options
+ *
+ * Returns 0 in case of full success.
+ * Returns -2 in case of some error with the packet.
+ * Returns -1 in case of error with the installation of rules
+ */
+static int
+virNWFilterSnoopDHCPDecode(virNWFilterSnoopReqPtr req,
+                           virNWFilterSnoopEthHdrPtr pep,
+                           int len, bool fromVM)
+{
+    struct iphdr *pip;
+    struct udphdr *pup;
+    virNWFilterSnoopDHCPHdrPtr pd;
+    virNWFilterSnoopIPLease ipl;
+    int mtype, leasetime;
+    uint32_t nwint;
+
+    /* go through the protocol headers */
+    switch (ntohs(pep->eh_type)) {
+    case ETHERTYPE_IP:
+        pip = (struct iphdr *) pep->eh_data;
+        len -= offsetof(virNWFilterSnoopEthHdr, eh_data);
+        break;
+    default:
+        return -2;
+    }
+
+    if (len < 0)
+        return -2;
+
+    pup = (struct udphdr *) ((char *) pip + (pip->ihl << 2));
+    len -= pip->ihl << 2;
+    if (len < 0)
+        return -2;
+
+    pd = (virNWFilterSnoopDHCPHdrPtr) ((char *) pup + sizeof(*pup));
+    len -= sizeof(*pup);
+    if (len < 0)
+        return -2;                 /* invalid packet length */
+
+    if (virNWFilterSnoopDHCPGetOpt(pd, len, &mtype, &leasetime) < 0)
+        return -2;
+
+    memset(&ipl, 0, sizeof(ipl));
+
+    memcpy(&nwint, &pd->d_yiaddr, sizeof(nwint));
+    virSocketAddrSetIPv4Addr(&ipl.ipAddress, ntohl(nwint));
+
+    memcpy(&nwint, &pd->d_siaddr, sizeof(nwint));
+    virSocketAddrSetIPv4Addr(&ipl.ipServer, ntohl(nwint));
+
+    if (leasetime == ~0)
+        ipl.timeout = ~0;
+    else
+        ipl.timeout = time(0) + leasetime;
+
+    ipl.snoopReq = req;
+
+    /* check that the type of message comes from the right direction */
+    switch (mtype) {
+    case DHCPACK:
+    case DHCPDECLINE:
+        if (fromVM)
+            return -2;
+        break;
+    case DHCPRELEASE:
+        if (!fromVM)
+            return -2;
+        break;
+    default:
+        break;
+    }
+
+    switch (mtype) {
+    case DHCPACK:
+        if (virNWFilterSnoopReqLeaseAdd(req, &ipl, true) < 0)
+            return -1;
+        break;
+    case DHCPDECLINE:
+    case DHCPRELEASE:
+        if (virNWFilterSnoopReqLeaseDel(req, &ipl.ipAddress, true) < 0)
+            return -1;
+        break;
+    default:
+        return -2;
+    }
+
+    return 0;
+}
+
+static pcap_t *
+virNWFilterSnoopDHCPOpen(const char *ifname, virMacAddr *mac,
+                         const char *filter, pcap_direction_t dir)
+{
+    pcap_t *handle = NULL;
+    struct bpf_program fp;
+    char pcap_errbuf[PCAP_ERRBUF_SIZE];
+    char *ext_filter = NULL;
+    char macaddr[VIR_MAC_STRING_BUFLEN];
+    const char *ext;
+
+    virMacAddrFormat((unsigned char *)mac, macaddr);
+
+    if (dir == PCAP_D_IN /* from VM */) {
+        /*
+         * don't want to hear about another VM's DHCP requests
+         *
+         * extend the filter with the macaddr of the VM; filter the
+         * more unlikely parameters first, then go for the MAC
+         */
+        ext = "and ether src";
+    } else {
+        ext = "and ether dst";
+    }
+
+    if (virAsprintf(&ext_filter, "%s %s %s", filter, ext, macaddr) < 0) {
+        virReportOOMError();
+        return NULL;
+    }
+
+    handle = pcap_create(ifname, pcap_errbuf);
+
+    if (handle == NULL) {
+        virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                               _("pcap_create failed"));
+        goto cleanup_nohandle;
+    }
+
+    if (pcap_set_snaplen(handle, PCAP_PBUFSIZE) < 0 ||
+        pcap_set_buffer_size(handle, PCAP_BUFFERSIZE) < 0 ||
+        pcap_activate(handle) < 0) {
+        virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                               _("setup of pcap handle failed"));
+        goto cleanup;
+    }
+
+    if (pcap_compile(handle, &fp, ext_filter, 1, PCAP_NETMASK_UNKNOWN) != 0) {
+        virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                               _("pcap_compile: %s"), pcap_geterr(handle));
+        goto cleanup;
+    }
+
+    if (pcap_setfilter(handle, &fp) != 0) {
+        virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                               _("pcap_setfilter: %s"), pcap_geterr(handle));
+        goto cleanup_freecode;
+    }
+
+    if (pcap_setdirection(handle, dir) < 0) {
+        virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                               _("pcap_setdirection: %s"),
+                               pcap_geterr(handle));
+        goto cleanup_freecode;
+    }
+
+    pcap_freecode(&fp);
+    VIR_FREE(ext_filter);
+
+    return handle;
+
+cleanup_freecode:
+    pcap_freecode(&fp);
+cleanup:
+    pcap_close(handle);
+cleanup_nohandle:
+    VIR_FREE(ext_filter);
+
+    return NULL;
+}
+
+/*
+ * Worker function to decode the DHCP message and with that
+ * also do the time-consuming work of instantiating the filters
+ */
+static void virNWFilterDHCPDecodeWorker(void *jobdata, void *opaque)
+{
+    virNWFilterSnoopReqPtr req = opaque;
+    virNWFilterDHCPDecodeJobPtr job = jobdata;
+    virNWFilterSnoopEthHdrPtr packet = (virNWFilterSnoopEthHdrPtr)job->packet;
+
+    if (virNWFilterSnoopDHCPDecode(req, packet,
+                                   job->caplen, job->fromVM) == -1) {
+        req->jobCompletionStatus = -1;
+
+        virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                               _("Instantiation of rules failed on "
+                                 "interface '%s'"), req->ifname);
+    }
+    virAtomicIntDec(job->qCtr);
+    VIR_FREE(job);
+}
+
+/*
+ * Submit a job to the worker thread doing the time-consuming work...
+ */
+static int
+virNWFilterSnoopDHCPDecodeJobSubmit(virThreadPoolPtr pool,
+                                    virNWFilterSnoopEthHdrPtr pep,
+                                    int len, pcap_direction_t dir,
+                                    virAtomicIntPtr qCtr)
+{
+    virNWFilterDHCPDecodeJobPtr job;
+    int ret;
+
+    if (len <= MIN_VALID_DHCP_PKT_SIZE || len > sizeof(job->packet))
+        return 0;
+
+    if (VIR_ALLOC(job) < 0) {
+        virReportOOMError();
+        return -1;
+    }
+
+    memcpy(job->packet, pep, len);
+    job->caplen = len;
+    job->fromVM = (dir == PCAP_D_IN);
+    job->qCtr = qCtr;
+
+    ret = virThreadPoolSendJob(pool, 0, job);
+
+    if (ret == 0)
+        virAtomicIntInc(qCtr);
+    else
+        VIR_FREE(job);
+
+    return ret;
+}
+
+/*
+ * virNWFilterSnoopRateLimit -- limit the rate of jobs submitted to the
+ *                              worker thread
+ *
+ * Help defend the worker thread from being flooded with likely bogus packets
+ * sent by the VM.
+ *
+ * rl: The state of the rate limiter
+ *
+ * Returns the delta of packets compared to the rate, i.e. if the rate
+ * is 4 (pkts/s) and we now have received 5 within a second, it would
+ * return 1. If the number of packets is below the rate, it returns 0.
+ */
+static unsigned int
+virNWFilterSnoopRateLimit(virNWFilterSnoopRateLimitConfPtr rl)
+{
+    time_t now = time(0);
+    int diff;
+# define IN_BURST(n,b) ((n)-(b) <= 1) /* bursts span 2 discreet seconds */
+
+    if (rl->prev != now && !IN_BURST(now, rl->burst)) {
+        rl->prev = now;
+        rl->pkt_ctr = 1;
+    } else {
+        rl->pkt_ctr++;
+        if (rl->pkt_ctr >= rl->rate) {
+            if (IN_BURST(now, rl->burst)) {
+                /* in a burst */
+                diff = rl->pkt_ctr - rl->burstRate;
+                if (diff > 0)
+                    return diff;
+                return 0;
+            }
+            if (rl->prev - rl->burst > rl->burstInterval) {
+                /* this second will start a new burst */
+                rl->burst = rl->prev;
+                return 0;
+            }
+            /* previous burst is too close */
+            return rl->pkt_ctr - rl->rate;
+        }
+    }
+
+    return 0;
+}
+
+/*
+ * virNWFilterSnoopRatePenalty
+ *
+ * @pc: pointer to the virNWFilterSnoopPcapConf
+ * @diff: the amount of pkts beyond the rate, i.e., if the rate is 10
+ *        and 13 pkts have been received now in one seconds, then
+ *        this should be 3.
+ *
+ * Adjusts the timeout the virNWFilterSnooPcapConf will be penalized for
+ * sending too many packets.
+ */
+static void
+virNWFilterSnoopRatePenalty(virNWFilterSnoopPcapConfPtr pc,
+                            unsigned int diff, unsigned int limit)
+{
+    if (diff > limit) {
+        unsigned long long now;
+
+        if (virTimeMillisNowRaw(&now) < 0) {
+            usleep(PCAP_FLOOD_TIMEOUT_MS); /* 1 ms */
+            pc->penaltyTimeoutAbs = 0;
+        } else {
+            /* don't listen to the fd for 1 ms */
+            pc->penaltyTimeoutAbs = now + PCAP_FLOOD_TIMEOUT_MS;
+        }
+    }
+}
+
+static int
+virNWFilterSnoopAdjustPoll(virNWFilterSnoopPcapConfPtr pc,
+                           size_t nPc, struct pollfd *pfd,
+                           int *pollTo)
+{
+    int ret = 0;
+    size_t i;
+    int tmp;
+    unsigned long long now = 0;
+
+    *pollTo = -1;
+
+    for (i = 0; i < nPc; i++) {
+        if (pc[i].penaltyTimeoutAbs != 0) {
+            if (now == 0) {
+                if (virTimeMillisNow(&now) < 0) {
+                    ret = -1;
+                    break;
+                }
+            }
+
+            if (now < pc[i].penaltyTimeoutAbs) {
+                /* don't listen to incoming data  on the fd for some time */
+                pfd[i].events &= ~POLLIN;
+                /*
+                 * calc the max. time to spend in poll() until adjustments
+                 * to the pollfd array are needed again.
+                 */
+                tmp = pc[i].penaltyTimeoutAbs - now;
+                if (*pollTo == -1 || tmp < *pollTo)
+                    *pollTo = tmp;
+            } else {
+                /* listen again to the fd */
+                pfd[i].events |= POLLIN;
+
+                pc[i].penaltyTimeoutAbs = 0;
+            }
+        }
+    }
+
+    return ret;
+}
+
+/*
+ * The DHCP snooping thread. It spends most of its time in the pcap
+ * library and if it gets suitable packets, it submits them to the worker
+ * thread for processing.
+ */
+static void
+virNWFilterDHCPSnoopThread(void *req0)
+{
+    virNWFilterSnoopReqPtr req = req0;
+    struct pcap_pkthdr *hdr;
+    virNWFilterSnoopEthHdrPtr packet;
+    int ifindex = 0;
+    int errcount = 0;
+    int tmp = -1, i, rv, n, pollTo;
+    char *threadkey = NULL;
+    virThreadPoolPtr worker = NULL;
+    time_t last_displayed = 0, last_displayed_queue = 0;
+    virNWFilterSnoopPcapConf pcapConf[] = {
+        {
+            .dir = PCAP_D_IN, /* from VM */
+            .filter = "dst port 67 and src port 68",
+            .rateLimit = {
+                .prev = time(0),
+                .rate = DHCP_PKT_RATE,
+                .burstRate = DHCP_PKT_BURST,
+                .burstInterval = DHCP_BURST_INTERVAL_S,
+            },
+            .maxQSize = MAX_QUEUED_JOBS,
+        }, {
+            .dir = PCAP_D_OUT, /* to VM */
+            .filter = "src port 67 and dst port 68",
+            .rateLimit = {
+                .prev = time(0),
+                .rate = DHCP_PKT_RATE,
+                .burstRate = DHCP_PKT_BURST,
+                .burstInterval = DHCP_BURST_INTERVAL_S,
+            },
+            .maxQSize = MAX_QUEUED_JOBS,
+        },
+    };
+    struct pollfd fds[] = {
+        {
+            /* get a POLLERR if interface goes down or disappears */
+            .events = POLLIN | POLLERR,
+        }, {
+            .events = POLLIN | POLLERR,
+        },
+    };
+    bool error = false;
+
+    /* whoever started us increased the reference counter for the req for us */
+
+    /* protect req->ifname & req->threadkey */
+    virNWFilterSnoopReqLock(req);
+
+    if (req->ifname && req->threadkey) {
+        for (i = 0; i < ARRAY_CARDINALITY(pcapConf); i++) {
+            pcapConf[i].handle =
+                virNWFilterSnoopDHCPOpen(req->ifname, &req->macaddr,
+                                         pcapConf[i].filter,
+                                         pcapConf[i].dir);
+            if (!pcapConf[i].handle ||
+                virAtomicIntInit(&pcapConf[i].qCtr) < 0) {
+                error = true;
+                break;
+            }
+            fds[i].fd = pcap_fileno(pcapConf[i].handle);
+        }
+        tmp = virNetDevGetIndex(req->ifname, &ifindex);
+        threadkey = strdup(req->threadkey);
+        worker = virThreadPoolNew(1, 1, 0,
+                                  virNWFilterDHCPDecodeWorker,
+                                  req);
+    }
+
+    /* let creator know how well we initialized */
+    if (error == true || !threadkey || tmp < 0 || !worker ||
+        ifindex != req->ifindex)
+        req->threadStatus = THREAD_STATUS_FAIL;
+    else
+        req->threadStatus = THREAD_STATUS_OK;
+
+    virCondSignal(&req->threadStatusCond);
+
+    virNWFilterSnoopReqUnlock(req);
+
+    if (req->threadStatus != THREAD_STATUS_OK)
+        goto exit;
+
+    while (!error) {
+        if (virNWFilterSnoopAdjustPoll(pcapConf,
+                                       ARRAY_CARDINALITY(pcapConf),
+                                       fds, &pollTo) < 0) {
+            break;
+        }
+
+        n = poll(fds, ARRAY_CARDINALITY(fds), pollTo);
+
+        if (n < 0) {
+            if (errno != EAGAIN && errno != EINTR)
+                error = true;
+        }
+
+        virNWFilterSnoopReqLeaseTimerRun(req);
+
+        /*
+         * Check whether we were cancelled or whether
+         * a previously submitted job failed.
+         */
+        if (!virNWFilterSnoopIsActive(threadkey) ||
+            req->jobCompletionStatus != 0)
+            goto exit;
+
+        for (i = 0; n > 0 && i < ARRAY_CARDINALITY(fds); i++) {
+            if (!fds[i].revents)
+                continue;
+
+            fds[i].revents = 0;
+            n--;
+
+            rv = pcap_next_ex(pcapConf[i].handle, &hdr,
+                              (const u_char **)&packet);
+
+            if (rv < 0) {
+                /* error reading from socket */
+                tmp = -1;
+
+                /* protect req->ifname */
+                virNWFilterSnoopReqLock(req);
+
+                if (req->ifname)
+                    tmp = virNetDevValidateConfig(req->ifname, NULL, ifindex);
+
+                virNWFilterSnoopReqUnlock(req);
+
+                if (tmp <= 0) {
+                    error = true;
+                    break;
+                }
+
+                if (++errcount > PCAP_READ_MAXERRS) {
+                    pcap_close(pcapConf[i].handle);
+                    pcapConf[i].handle = NULL;
+
+                    /* protect req->ifname */
+                    virNWFilterSnoopReqLock(req);
+
+                    virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                                           _("interface '%s' failing; "
+                                             "reopening"),
+                                           req->ifname);
+                    if (req->ifname)
+                        pcapConf[i].handle =
+                            virNWFilterSnoopDHCPOpen(req->ifname, &req->macaddr,
+                                                     pcapConf[i].filter,
+                                                     pcapConf[i].dir);
+
+                    virNWFilterSnoopReqUnlock(req);
+
+                    if (!pcapConf[i].handle) {
+                        error = true;
+                        break;
+                    }
+                }
+                continue;
+            }
+
+            errcount = 0;
+
+            if (rv) {
+                unsigned int diff;
+
+                /* submit packet to worker thread */
+                if (virAtomicIntRead(&pcapConf[i].qCtr) >
+                    pcapConf[i].maxQSize) {
+                    if (last_displayed_queue - time(0) > 10) {
+                        last_displayed_queue = time(0);
+                        VIR_WARN("Worker thread for interface '%s' has a "
+                                 "job queue that is too long\n",
+                                 req->ifname);
+                    }
+                    continue;
+                }
+
+                diff = virNWFilterSnoopRateLimit(&pcapConf[i].rateLimit);
+                if (diff > 0) {
+                    virNWFilterSnoopRatePenalty(&pcapConf[i], diff,
+                                                DHCP_PKT_RATE);
+                    /* rate-limited warnings */
+                    if (time(0) - last_displayed > 10) {
+                         last_displayed = time(0);
+                         VIR_WARN("Too many DHCP packets on interface '%s'",
+                                  req->ifname);
+                    }
+                    continue;
+                }
+
+                if (virNWFilterSnoopDHCPDecodeJobSubmit(worker, packet,
+                                                      hdr->caplen,
+                                                      pcapConf[i].dir,
+                                                      &pcapConf[i].qCtr) < 0) {
+                    virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                                           _("Job submission failed on "
+                                           "interface '%s'"), req->ifname);
+                    error = true;
+                    break;
+                }
+            }
+        } /* for all fds */
+    } /* while (!error) */
+
+    /* protect IfNameToKey */
+    virNWFilterSnoopLock();
+
+    /* protect req->ifname & req->threadkey */
+    virNWFilterSnoopReqLock(req);
+
+    virNWFilterSnoopCancel(&req->threadkey);
+
+    (void) virHashRemoveEntry(virNWFilterSnoopState.ifnameToKey, req->ifname);
+
+    VIR_FREE(req->ifname);
+
+    virNWFilterSnoopReqUnlock(req);
+    virNWFilterSnoopUnlock();
+
+exit:
+    virThreadPoolFree(worker);
+
+    virNWFilterSnoopReqPut(req);
+
+    VIR_FREE(threadkey);
+
+    for (i = 0; i < ARRAY_CARDINALITY(pcapConf); i++) {
+        if (pcapConf[i].handle)
+            pcap_close(pcapConf[i].handle);
+    }
+
+    virAtomicIntDec(&virNWFilterSnoopState.nThreads);
+
+    return;
+}
+
+static void
+virNWFilterSnoopIFKeyFMT(char *ifkey, const unsigned char *vmuuid,
+                         unsigned const char *macaddr)
+{
+    virUUIDFormat(vmuuid, ifkey);
+    ifkey[VIR_UUID_STRING_BUFLEN - 1] = '-';
+    virMacAddrFormat(macaddr, ifkey + VIR_UUID_STRING_BUFLEN);
+}
+
+int
+virNWFilterDHCPSnoopReq(virNWFilterTechDriverPtr techdriver,
+                        const char *ifname,
+                        const char *linkdev,
+                        enum virDomainNetType nettype,
+                        const unsigned char *vmuuid,
+                        const unsigned char *macaddr,
+                        const char *filtername,
+                        virNWFilterHashTablePtr filterparams,
+                        virNWFilterDriverStatePtr driver)
+{
+    virNWFilterSnoopReqPtr req;
+    bool isnewreq;
+    char ifkey[VIR_IFKEY_LEN];
+    int tmp;
+    virThread thread;
+    virNWFilterVarValuePtr dhcpsrvrs;
+
+    virNWFilterSnoopIFKeyFMT(ifkey, vmuuid, macaddr);
+
+    req = virNWFilterSnoopReqGetByIFKey(ifkey);
+    isnewreq = (req == NULL);
+    if (!isnewreq) {
+        if (req->threadkey) {
+            virNWFilterSnoopReqPut(req);
+            return 0;
+        }
+        /* a recycled req may still have filtername and vars */
+        VIR_FREE(req->filtername);
+        virNWFilterHashTableFree(req->vars);
+    } else {
+        req = virNWFilterSnoopReqNew(ifkey);
+        if (!req)
+            return -1;
+    }
+
+    req->driver = driver;
+    req->techdriver = techdriver;
+    tmp = virNetDevGetIndex(ifname, &req->ifindex);
+    req->linkdev = linkdev ? strdup(linkdev) : NULL;
+    req->nettype = nettype;
+    req->ifname = strdup(ifname);
+    memcpy(req->macaddr, macaddr, sizeof(req->macaddr));
+    req->filtername = strdup(filtername);
+    req->vars = virNWFilterHashTableCreate(0);
+
+    if (!req->ifname || !req->filtername || !req->vars || tmp < 0) {
+        virReportOOMError();
+        goto exit_snoopreqput;
+    }
+
+    /* check that all tools are available for applying the filters (late) */
+    if ( !techdriver->canApplyBasicRules()) {
+        virNWFilterReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                               _("IP parameter must be provided since "
+                                 "snooping the IP address does not work "
+                                 "possibly due to missing tools"));
+        goto exit_snoopreqput;
+    }
+
+    dhcpsrvrs = virHashLookup(filterparams->hashTable,
+                              NWFILTER_VARNAME_DHCPSERVER);
+
+    if (techdriver->applyDHCPOnlyRules(req->ifname, req->macaddr,
+                                       dhcpsrvrs, false) < 0) {
+        virNWFilterReportError(VIR_ERR_INTERNAL_ERROR, _("applyDHCPOnlyRules "
+                               "failed - spoofing not protected!"));
+        goto exit_snoopreqput;
+    }
+
+    if (virNWFilterHashTablePutAll(filterparams, req->vars) < 0) {
+        virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                               _("virNWFilterDHCPSnoopReq: can't copy variables"
+                                " on if %s"), ifkey);
+        goto exit_snoopreqput;
+    }
+
+    virNWFilterSnoopLock();
+
+    if (virHashAddEntry(virNWFilterSnoopState.ifnameToKey, ifname,
+                        req->ifkey) < 0) {
+        virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                               _("virNWFilterDHCPSnoopReq ifname map failed"
+                                 " on interface \"%s\" key \"%s\""), ifname,
+                               ifkey);
+        goto exit_snoopunlock;
+    }
+
+    if (isnewreq &&
+        virHashAddEntry(virNWFilterSnoopState.snoopReqs, ifkey, req) < 0) {
+        virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                               _("virNWFilterDHCPSnoopReq req add failed on"
+                               " interface \"%s\" ifkey \"%s\""), ifname,
+                               ifkey);
+        goto exit_rem_ifnametokey;
+    }
+
+    /* prevent thread from holding req */
+    virNWFilterSnoopReqLock(req);
+
+    if (virThreadCreate(&thread, false, virNWFilterDHCPSnoopThread,
+                        req) != 0) {
+        virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                               _("virNWFilterDHCPSnoopReq virThreadCreate "
+                                 "failed on interface '%s'"), ifname);
+        goto exit_snoopreq_unlock;
+    }
+
+    virAtomicIntInc(&virNWFilterSnoopState.nThreads);
+
+    req->threadkey = virNWFilterSnoopActivate(req);
+    if (!req->threadkey) {
+        virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                               _("Actication of snoop request failed on "
+                                 "interface '%s'"), req->ifname);
+        goto exit_snoopreq_unlock;
+    }
+
+    if (virNWFilterSnoopReqRestore(req) < 0) {
+        virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                               _("Restoring of leases failed on "
+                               "interface '%s'"), req->ifname);
+        goto exit_snoop_cancel;
+    }
+
+    /* sync with thread */
+    if (virCondWait(&req->threadStatusCond, &req->lock) < 0 ||
+        req->threadStatus != THREAD_STATUS_OK)
+        goto exit_snoop_cancel;
+
+    virNWFilterSnoopReqUnlock(req);
+
+    virNWFilterSnoopUnlock();
+
+    /* do not 'put' the req -- the thread will do this */
+
+    return 0;
+
+exit_snoop_cancel:
+    virNWFilterSnoopCancel(&req->threadkey);
+exit_snoopreq_unlock:
+    virNWFilterSnoopReqUnlock(req);
+exit_rem_ifnametokey:
+    virHashRemoveEntry(virNWFilterSnoopState.ifnameToKey, ifname);
+exit_snoopunlock:
+    virNWFilterSnoopUnlock();
+exit_snoopreqput:
+    virNWFilterSnoopReqPut(req);
+
+    return -1;
+}
+
+static void
+virNWFilterSnoopLeaseFileClose(void)
+{
+    VIR_FORCE_CLOSE(virNWFilterSnoopState.leaseFD);
+}
+
+static void
+virNWFilterSnoopLeaseFileOpen(void)
+{
+    virNWFilterSnoopLeaseFileClose();
+
+    virNWFilterSnoopState.leaseFD = open(LEASEFILE, O_CREAT|O_RDWR|O_APPEND,
+                                         0644);
+}
+
+/*
+ * Write a single lease to the given file.
+ *
+ */
+static int
+virNWFilterSnoopLeaseFileWrite(int lfd, const char *ifkey,
+                               virNWFilterSnoopIPLeasePtr ipl)
+{
+    char lbuf[256];
+    char *ipstr, *dhcpstr;
+    size_t len;
+    int ret = 0;
+
+    ipstr = virSocketAddrFormat(&ipl->ipAddress);
+    dhcpstr = virSocketAddrFormat(&ipl->ipServer);
+
+    if (!dhcpstr || !ipstr) {
+        ret = -1;
+        goto cleanup;
+    }
+
+    /* time intf ip dhcpserver */
+    snprintf(lbuf, sizeof(lbuf), "%u %s %s %s\n", ipl->timeout,
+             ifkey, ipstr, dhcpstr);
+
+    len = strlen(lbuf);
+
+    if (safewrite(lfd, lbuf, len) != len) {
+        virReportSystemError(errno, "%s", _("lease file write failed"));
+        ret = -1;
+        goto cleanup;
+    }
+
+    (void) fsync(lfd);
+
+cleanup:
+    VIR_FREE(dhcpstr);
+    VIR_FREE(ipstr);
+
+    return ret;
+}
+
+/*
+ * Append a single lease to the end of the lease file.
+ * To keep a limited number of dead leases, re-read the lease
+ * file if the threshold of active leases versus written ones
+ * exceeds a threshold.
+ */
+static void
+virNWFilterSnoopLeaseFileSave(virNWFilterSnoopIPLeasePtr ipl)
+{
+    virNWFilterSnoopReqPtr req = ipl->snoopReq;
+
+    virNWFilterSnoopLock();
+
+    if (virNWFilterSnoopState.leaseFD < 0)
+        virNWFilterSnoopLeaseFileOpen();
+    if (virNWFilterSnoopLeaseFileWrite(virNWFilterSnoopState.leaseFD,
+                                       req->ifkey, ipl) < 0)
+        goto err_exit;
+
+    /* keep dead leases at < ~95% of file size */
+    if (virAtomicIntInc(&virNWFilterSnoopState.wLeases) >=
+        virAtomicIntRead(&virNWFilterSnoopState.nLeases) * 20)
+        virNWFilterSnoopLeaseFileLoad();   /* load & refresh lease file */
+
+err_exit:
+    virNWFilterSnoopUnlock();
+}
+
+/*
+ * Have requests removed that have no leases.
+ * Remove all expired leases.
+ * Call this function with the SnoopLock held.
+ */
+static int
+virNWFilterSnoopPruneIter(const void *payload,
+                          const void *name ATTRIBUTE_UNUSED,
+                          const void *data ATTRIBUTE_UNUSED)
+{
+    const virNWFilterSnoopReqPtr req = (virNWFilterSnoopReqPtr)payload;
+    bool del_req;
+
+    /* clean up orphaned, expired leases */
+
+    /* protect req->threadkey */
+    virNWFilterSnoopReqLock(req);
+
+    if (!req->threadkey)
+        virNWFilterSnoopReqLeaseTimerRun(req);
+
+    /*
+     * have the entry removed if it has no leases and no one holds a ref
+     */
+    del_req = ((req->start == NULL) && (virAtomicIntRead(&req->refctr) == 0));
+
+    virNWFilterSnoopReqUnlock(req);
+
+    return del_req;
+}
+
+/*
+ * Iterator to write all leases of a single request to a file.
+ * Call this function with the SnoopLock held.
+ */
+static void
+virNWFilterSnoopSaveIter(void *payload,
+                         const void *name ATTRIBUTE_UNUSED,
+                         void *data)
+{
+    virNWFilterSnoopReqPtr req = payload;
+    int  tfd = *(int *)data;
+    virNWFilterSnoopIPLeasePtr ipl;
+
+    /* protect req->start */
+    virNWFilterSnoopReqLock(req);
+
+    for (ipl = req->start; ipl; ipl = ipl->next)
+        (void) virNWFilterSnoopLeaseFileWrite(tfd, req->ifkey, ipl);
+
+    virNWFilterSnoopReqUnlock(req);
+}
+
+/*
+ * Write all valid leases into a temporary file and then
+ * rename the file to the final file.
+ * Call this function with the SnoopLock held.
+ */
+static void
+virNWFilterSnoopLeaseFileRefresh(void)
+{
+    int tfd;
+
+    (void) unlink(TMPLEASEFILE);
+    /* lease file loaded, delete old one */
+    tfd = open(TMPLEASEFILE, O_CREAT|O_RDWR|O_TRUNC|O_EXCL, 0644);
+    if (tfd < 0) {
+        virReportSystemError(errno, _("open(\"%s\")"), TMPLEASEFILE);
+        return;
+    }
+
+    if (virNWFilterSnoopState.snoopReqs) {
+        /* clean up the requests */
+        virHashRemoveSet(virNWFilterSnoopState.snoopReqs,
+                         virNWFilterSnoopPruneIter, NULL);
+        /* now save them */
+        virHashForEach(virNWFilterSnoopState.snoopReqs,
+                       virNWFilterSnoopSaveIter, (void *)&tfd);
+    }
+
+    VIR_FORCE_CLOSE(tfd);
+
+    if (rename(TMPLEASEFILE, LEASEFILE) < 0) {
+        virReportSystemError(errno, _("rename(\"%s\", \"%s\")"),
+                             TMPLEASEFILE, LEASEFILE);
+        (void) unlink(TMPLEASEFILE);
+    }
+    virAtomicIntSet(&virNWFilterSnoopState.wLeases, 0);
+    virNWFilterSnoopLeaseFileOpen();
+}
+
+
+static void
+virNWFilterSnoopLeaseFileLoad(void)
+{
+    char line[256], ifkey[VIR_IFKEY_LEN];
+    char ipstr[INET_ADDRSTRLEN], srvstr[INET_ADDRSTRLEN];
+    virNWFilterSnoopIPLease ipl;
+    virNWFilterSnoopReqPtr req;
+    time_t now;
+    FILE *fp;
+    int ln = 0, tmp;
+
+    /* protect the lease file */
+    virNWFilterSnoopLock();
+
+    fp = fopen(LEASEFILE, "r");
+    time(&now);
+    while (fp && fgets(line, sizeof(line), fp)) {
+        if (line[strlen(line)-1] != '\n') {
+            virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                                   _("virNWFilterSnoopLeaseFileLoad lease file "
+                                     "line %d corrupt"), ln);
+            break;
+        }
+        ln++;
+        /* key len 55 = "VMUUID"+'-'+"MAC" */
+        if (sscanf(line, "%u %55s %16s %16s", &ipl.timeout,
+                   ifkey, ipstr, srvstr) < 4) {
+            virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                                   _("virNWFilterSnoopLeaseFileLoad lease file "
+                                     "line %d corrupt"), ln);
+            break;
+        }
+        if (ipl.timeout && ipl.timeout < now)
+            continue;
+        req = virNWFilterSnoopReqGetByIFKey(ifkey);
+        if (!req) {
+            req = virNWFilterSnoopReqNew(ifkey);
+            if (!req)
+               break;
+
+            tmp = virHashAddEntry(virNWFilterSnoopState.snoopReqs, ifkey, req);
+
+            if (tmp < 0) {
+                virNWFilterSnoopReqPut(req);
+                virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                                       _("virNWFilterSnoopLeaseFileLoad req add"
+                                         " failed on interface \"%s\""), ifkey);
+                continue;
+            }
+        }
+
+        if (virSocketAddrParseIPv4(&ipl.ipAddress, ipstr) < 0) {
+            virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                                  _("line %d corrupt ipaddr \"%s\""),
+                                  ln, ipstr);
+            virNWFilterSnoopReqPut(req);
+            continue;
+        }
+        (void) virSocketAddrParseIPv4(&ipl.ipServer, srvstr);
+        ipl.snoopReq = req;
+
+        if (ipl.timeout)
+            virNWFilterSnoopReqLeaseAdd(req, &ipl, false);
+        else
+            virNWFilterSnoopReqLeaseDel(req, &ipl.ipAddress, false);
+
+        virNWFilterSnoopReqPut(req);
+    }
+
+    VIR_FORCE_FCLOSE(fp);
+
+    virNWFilterSnoopLeaseFileRefresh();
+
+    virNWFilterSnoopUnlock();
+}
+
+/*
+ * Wait until all threads have ended.
+ */
+static void
+virNWFilterSnoopJoinThreads(void)
+{
+    while (virAtomicIntRead(&virNWFilterSnoopState.nThreads) != 0) {
+        VIR_WARN("Waiting for snooping threads to terminate: %u\n",
+                 virAtomicIntRead(&virNWFilterSnoopState.nThreads));
+        usleep(1000 * 1000);
+    }
+}
+
+/*
+ * Iterator to remove a requests, repeatedly called on one
+ * request after another.
+ * The requests' ifname is freed allowing for an association
+ * of the Snoop request's leases with the same VM under a
+ * different interface name at a later time.
+ */
+static int
+virNWFilterSnoopRemAllReqIter(const void *payload,
+                              const void *name ATTRIBUTE_UNUSED,
+                              const void *data ATTRIBUTE_UNUSED)
+{
+    const virNWFilterSnoopReqPtr req = (virNWFilterSnoopReqPtr)payload;
+
+    /* protect req->ifname */
+    virNWFilterSnoopReqLock(req);
+
+    if (req->ifname) {
+        (void) virHashRemoveEntry(virNWFilterSnoopState.ifnameToKey,
+                                  req->ifname);
+
+        VIR_FREE(req->ifname);
+    }
+
+    virNWFilterSnoopReqUnlock(req);
+
+    /* removal will call virNWFilterSnoopCancel() */
+    return 1;
+}
+
+
+/*
+ * Terminate all threads; keep the SnoopReqs hash allocated
+ */
+static void
+virNWFilterSnoopEndThreads(void)
+{
+    virNWFilterSnoopLock();
+    virHashRemoveSet(virNWFilterSnoopState.snoopReqs,
+                     virNWFilterSnoopRemAllReqIter,
+                     NULL);
+    virNWFilterSnoopUnlock();
+}
+
+int
+virNWFilterDHCPSnoopInit(void)
+{
+    if (virNWFilterSnoopState.snoopReqs)
+        return 0;
+
+    if (virMutexInitRecursive(&virNWFilterSnoopState.snoopLock) < 0 ||
+        virMutexInit(&virNWFilterSnoopState.activeLock) < 0 ||
+        virAtomicIntInit(&virNWFilterSnoopState.nLeases) < 0 ||
+        virAtomicIntInit(&virNWFilterSnoopState.wLeases) < 0 ||
+        virAtomicIntInit(&virNWFilterSnoopState.nThreads) < 0)
+        return -1;
+
+    virNWFilterSnoopState.ifnameToKey = virHashCreate(0, NULL);
+    virNWFilterSnoopState.active = virHashCreate(0, NULL);
+    virNWFilterSnoopState.snoopReqs =
+        virHashCreate(0, virNWFilterSnoopReqRelease);
+
+    if (!virNWFilterSnoopState.ifnameToKey ||
+        !virNWFilterSnoopState.snoopReqs ||
+        !virNWFilterSnoopState.active) {
+        virReportOOMError();
+        goto err_exit;
+    }
+
+    virNWFilterSnoopLeaseFileLoad();
+    virNWFilterSnoopLeaseFileOpen();
+
+    return 0;
+
+err_exit:
+    virHashFree(virNWFilterSnoopState.ifnameToKey);
+    virNWFilterSnoopState.ifnameToKey = NULL;
+
+    virHashFree(virNWFilterSnoopState.snoopReqs);
+    virNWFilterSnoopState.snoopReqs = NULL;
+
+    virHashFree(virNWFilterSnoopState.active);
+    virNWFilterSnoopState.active = NULL;
+
+    return -1;
+}
+
+void
+virNWFilterDHCPSnoopEnd(const char *ifname)
+{
+    char *ifkey = NULL;
+
+    virNWFilterSnoopLock();
+
+    if (!virNWFilterSnoopState.snoopReqs)
+        goto cleanup;
+
+    if (ifname) {
+        ifkey = (char *)virHashLookup(virNWFilterSnoopState.ifnameToKey,
+                                      ifname);
+        if (!ifkey) {
+            virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                                   _("ifname \"%s\" not in key map"), ifname);
+            goto cleanup;
+        }
+
+        (void) virHashRemoveEntry(virNWFilterSnoopState.ifnameToKey, ifname);
+    }
+
+    if (ifkey) {
+        virNWFilterSnoopReqPtr req;
+
+        req = virNWFilterSnoopReqGetByIFKey(ifkey);
+        if (!req) {
+            virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                                   _("ifkey \"%s\" has no req"), ifkey);
+            goto cleanup;
+        }
+
+        /* protect req->ifname & req->threadkey */
+        virNWFilterSnoopReqLock(req);
+
+        /* keep valid lease req; drop interface association */
+        virNWFilterSnoopCancel(&req->threadkey);
+
+        VIR_FREE(req->ifname);
+
+        virNWFilterSnoopReqUnlock(req);
+
+        virNWFilterSnoopReqPut(req);
+    } else {                      /* free all of them */
+        virNWFilterSnoopLeaseFileClose();
+
+        virHashRemoveAll(virNWFilterSnoopState.ifnameToKey);
+
+        /* tell the threads to terminate */
+        virNWFilterSnoopEndThreads();
+
+        virNWFilterSnoopLeaseFileLoad();
+    }
+
+cleanup:
+    virNWFilterSnoopUnlock();
+}
+
+void
+virNWFilterDHCPSnoopShutdown(void)
+{
+    virNWFilterSnoopEndThreads();
+    virNWFilterSnoopJoinThreads();
+
+    virNWFilterSnoopLock();
+
+    virNWFilterSnoopLeaseFileClose();
+    virHashFree(virNWFilterSnoopState.ifnameToKey);
+    virHashFree(virNWFilterSnoopState.snoopReqs);
+
+    virNWFilterSnoopUnlock();
+
+    virNWFilterSnoopActiveLock();
+    virHashFree(virNWFilterSnoopState.active);
+    virNWFilterSnoopActiveUnlock();
+}
+
+#else /* HAVE_LIBPCAP */
+
+int
+virNWFilterDHCPSnoopInit(void)
+{
+    return -1;
+}
+
+void
+virNWFilterDHCPSnoopEnd(const char *ifname ATTRIBUTE_UNUSED)
+{
+    return;
+}
+
+void
+virNWFilterDHCPSnoopShutdown(void)
+{
+    return;
+}
+
+int
+virNWFilterDHCPSnoopReq(virNWFilterTechDriverPtr techdriver ATTRIBUTE_UNUSED,
+                        const char *ifname ATTRIBUTE_UNUSED,
+                        const char *linkdev ATTRIBUTE_UNUSED,
+                        enum virDomainNetType nettype ATTRIBUTE_UNUSED,
+                        const unsigned char *vmuuid ATTRIBUTE_UNUSED,
+                        const unsigned char *macaddr ATTRIBUTE_UNUSED,
+                        const char *filtername ATTRIBUTE_UNUSED,
+                        virNWFilterHashTablePtr filterparams ATTRIBUTE_UNUSED,
+                        virNWFilterDriverStatePtr driver ATTRIBUTE_UNUSED)
+{
+    virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
+                           _("libvirt was not compiled with libpcap and \""
+                           NWFILTER_VARNAME_CTRL_IP_LEARNING
+                           "='dhcp'\" requires it."));
+    return -1;
+}
+#endif /* HAVE_LIBPCAP */
Index: libvirt-acl/src/nwfilter/nwfilter_dhcpsnoop.h
===================================================================
--- /dev/null
+++ libvirt-acl/src/nwfilter/nwfilter_dhcpsnoop.h
@@ -0,0 +1,39 @@
+/*
+ * nwfilter_dhcpsnoop.h: support DHCP snooping for a VM on an interface
+ *
+ * Copyright (C) 2010 IBM Corp.
+ * Copyright (C) 2010 David L Stevens
+ *
+ * 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307  USA
+ *
+ * Author: David L Stevens <dlstevens us ibm com>
+ */
+
+#ifndef __NWFILTER_DHCPSNOOP_H
+# define __NWFILTER_DHCPSNOOP_H
+
+int virNWFilterDHCPSnoopInit(void);
+void virNWFilterDHCPSnoopShutdown(void);
+int virNWFilterDHCPSnoopReq(virNWFilterTechDriverPtr techdriver,
+                            const char *ifname,
+                            const char *linkdev,
+                            enum virDomainNetType nettype,
+                            const unsigned char *vmuuid,
+                            const unsigned char *macaddr,
+                            const char *filtername,
+                            virNWFilterHashTablePtr filterparams,
+                            virNWFilterDriverStatePtr driver);
+void virNWFilterDHCPSnoopEnd(const char *ifname);
+#endif /* __NWFILTER_DHCPSNOOP_H */
Index: libvirt-acl/src/nwfilter/nwfilter_driver.c
===================================================================
--- libvirt-acl.orig/src/nwfilter/nwfilter_driver.c
+++ libvirt-acl/src/nwfilter/nwfilter_driver.c
@@ -39,6 +39,7 @@
 #include "nwfilter_gentech_driver.h"
 #include "configmake.h"
 
+#include "nwfilter_dhcpsnoop.h"
 #include "nwfilter_learnipaddr.h"
 
 #define VIR_FROM_THIS VIR_FROM_NWFILTER
@@ -66,6 +67,8 @@ static int
 nwfilterDriverStartup(int privileged) {
     char *base = NULL;
 
+    if (virNWFilterDHCPSnoopInit() < 0)
+        return -1;
     if (virNWFilterLearnInit() < 0)
         return -1;
 
@@ -120,6 +123,7 @@ alloc_err_exit:
 
 conf_init_err:
     virNWFilterTechDriversShutdown();
+    virNWFilterDHCPSnoopShutdown();
     virNWFilterLearnShutdown();
 
     return -1;
@@ -142,6 +146,7 @@ nwfilterDriverReload(void) {
     conn = virConnectOpen("qemu:///system");
 
     if (conn) {
+        virNWFilterDHCPSnoopEnd(NULL);
         /* shut down all threads -- they will be restarted if necessary */
         virNWFilterLearnThreadsTerminate(true);
 
@@ -196,6 +201,7 @@ nwfilterDriverShutdown(void) {
 
     virNWFilterConfLayerShutdown();
     virNWFilterTechDriversShutdown();
+    virNWFilterDHCPSnoopShutdown();
     virNWFilterLearnShutdown();
 
     nwfilterDriverLock(driverState);
Index: libvirt-acl/src/nwfilter/nwfilter_gentech_driver.c
===================================================================
--- libvirt-acl.orig/src/nwfilter/nwfilter_gentech_driver.c
+++ libvirt-acl/src/nwfilter/nwfilter_gentech_driver.c
@@ -32,6 +32,7 @@
 #include "virterror_internal.h"
 #include "nwfilter_gentech_driver.h"
 #include "nwfilter_ebiptables_driver.h"
+#include "nwfilter_dhcpsnoop.h"
 #include "nwfilter_learnipaddr.h"
 #include "virnetdev.h"
 #include "datatypes.h"
@@ -39,8 +40,10 @@
 #define VIR_FROM_THIS VIR_FROM_NWFILTER
 
 
-#define NWFILTER_STD_VAR_MAC "MAC"
-#define NWFILTER_STD_VAR_IP  "IP"
+#define NWFILTER_STD_VAR_MAC NWFILTER_VARNAME_MAC
+#define NWFILTER_STD_VAR_IP  NWFILTER_VARNAME_IP
+
+#define NWFILTER_DFLT_LEARN  "any"
 
 static int _virNWFilterTeardownFilter(const char *ifname);
 
@@ -662,6 +665,9 @@ virNWFilterInstantiate(const unsigned ch
     void **ptrs = NULL;
     int instantiate = 1;
     char *buf;
+    virNWFilterVarValuePtr lv;
+    const char *learning;
+    bool reportIP = false;
 
     virNWFilterHashTablePtr missing_vars = virNWFilterHashTableCreate(0);
     if (!missing_vars) {
@@ -678,22 +684,47 @@ virNWFilterInstantiate(const unsigned ch
     if (rc < 0)
         goto err_exit;
 
+    lv = virHashLookup(vars->hashTable, NWFILTER_VARNAME_CTRL_IP_LEARNING);
+    if (lv)
+        learning = virNWFilterVarValueGetNthValue(lv, 0);
+    else
+        learning = NULL;
+
+    if (learning == NULL)
+        learning = NWFILTER_DFLT_LEARN;
+
     if (virHashSize(missing_vars->hashTable) == 1) {
         if (virHashLookup(missing_vars->hashTable,
                           NWFILTER_STD_VAR_IP) != NULL) {
-            if (virNWFilterLookupLearnReq(ifindex) == NULL) {
-                rc = virNWFilterLearnIPAddress(techdriver,
-                                               ifname,
-                                               ifindex,
-                                               linkdev,
-                                               nettype, macaddr,
-                                               filter->name,
-                                               vars, driver,
-                                               DETECT_DHCP|DETECT_STATIC);
+            if (STRCASEEQ(learning, "none")) {        /* no learning */
+                reportIP = true;
+                goto err_unresolvable_vars;
             }
-            goto err_exit;
-        }
-        goto err_unresolvable_vars;
+            if (STRCASEEQ(learning, "dhcp")) {
+                rc = virNWFilterDHCPSnoopReq(techdriver, ifname, linkdev,
+                                             nettype, vmuuid, macaddr,
+                                             filter->name, vars, driver);
+                goto err_exit;
+            } else if (STRCASEEQ(learning, "any")) {
+                if (virNWFilterLookupLearnReq(ifindex) == NULL) {
+                    rc = virNWFilterLearnIPAddress(techdriver,
+                                                   ifname,
+                                                   ifindex,
+                                                   linkdev,
+                                                   nettype, macaddr,
+                                                   filter->name,
+                                                   vars, driver,
+                                                   DETECT_DHCP|DETECT_STATIC);
+                }
+                goto err_exit;
+            } else {
+                rc = -1;
+                virNWFilterReportError(VIR_ERR_PARSE_FAILED, _("filter '%s' "
+                                       "learning value '%s' invalid."),
+                                       filter->name, learning);
+            }
+        } else
+             goto err_unresolvable_vars;
     } else if (virHashSize(missing_vars->hashTable) > 1) {
         goto err_unresolvable_vars;
     } else if (!forceWithPendingReq &&
@@ -761,7 +792,7 @@ err_exit:
 
 err_unresolvable_vars:
 
-    buf = virNWFilterPrintVars(missing_vars->hashTable, ", ", false, false);
+    buf = virNWFilterPrintVars(missing_vars->hashTable, ", ", false, reportIP);
     if (buf) {
         virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
                    _("Cannot instantiate filter due to unresolvable "
@@ -1092,6 +1123,8 @@ _virNWFilterTeardownFilter(const char *i
         return -1;
     }
 
+    virNWFilterDHCPSnoopEnd(ifname);
+
     virNWFilterTerminateLearnReq(ifname);
 
     if (virNWFilterLockIface(ifname) < 0)
Index: libvirt-acl/src/conf/nwfilter_params.h
===================================================================
--- libvirt-acl.orig/src/conf/nwfilter_params.h
+++ libvirt-acl/src/conf/nwfilter_params.h
@@ -91,6 +91,11 @@ int virNWFilterHashTablePutAll(virNWFilt
 # define VALID_VARVALUE \
   "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_.:"
 
+# define NWFILTER_VARNAME_IP "IP"
+# define NWFILTER_VARNAME_MAC "MAC"
+# define NWFILTER_VARNAME_CTRL_IP_LEARNING "CTRL_IP_LEARNING"
+# define NWFILTER_VARNAME_DHCPSERVER "DHCPSERVER"
+
 enum virNWFilterVarAccessType {
     VIR_NWFILTER_VAR_ACCESS_ELEMENT = 0,
     VIR_NWFILTER_VAR_ACCESS_ITERATOR = 1,
Index: libvirt-acl/po/POTFILES.in
===================================================================
--- libvirt-acl.orig/po/POTFILES.in
+++ libvirt-acl/po/POTFILES.in
@@ -53,6 +53,7 @@ src/node_device/node_device_hal.c
 src/node_device/node_device_linux_sysfs.c
 src/node_device/node_device_udev.c
 src/nodeinfo.c
+src/nwfilter/nwfilter_dhcpsnoop.c
 src/nwfilter/nwfilter_driver.c
 src/nwfilter/nwfilter_ebiptables_driver.c
 src/nwfilter/nwfilter_gentech_driver.c


[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]