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

Re: [libvirt] [PATCH v3] leaseshelper: improvements to support all events



On Thu, Sep 11, 2014 at 8:38 PM, Peter Krempa <pkrempa redhat com> wrote:
> On 08/04/14 09:59, Nehal J Wani wrote:
>> This patch enables the helper program to detect event(s) triggered when there
>> is a change in lease length or expiry and client-id. This transfers complete
>> control of leases database to libvirt and obsoletes use of the lease database
>> file (<network-name>.leases). That file will not be created, read, or written.
>> This is achieved by adding the option --leasefile-ro to dnsmasq and passing a
>> custom env var to leaseshelper, which helps us map events related to leases
>> with their corresponding network bridges, no matter what the event be.
>>
>> Also, this requires the addition of a new non-lease entry in our custom lease
>> database: "server-duid". It is required to identify a DHCPv6 server.
>>
>> Now that dnsmasq doesn't maintain its own leases database, it relies on our
>> helper program to tell it about previous leases and server duid. Thus, this
>> patch makes our leases program honor an extra action: "init", in which it sends
>> the known info in a particular format to dnsmasq by printing it to stdout.
>>
>> ---
>>
>>  This is compatible with libvirt 1.2.6 as only additions have been
>>  introduced, and the old leases file (*.status) will still be supported.
>>
>>  v3: * Add server-duid as an entry in the lease object for every ipv6 lease.
>>      * Remove unnecessary variables and double copies.
>>      * Take value from DNSMASQ_OLD_HOSTNAME if hostname is not known.
>>
>>  v2: http://www.redhat.com/archives/libvir-list/2014-July/msg01109.html
>>
>>  v1: https://www.redhat.com/archives/libvir-list/2014-July/msg00568.html
>>
>>  src/network/bridge_driver.c |   3 +
>>  src/network/leaseshelper.c  | 132 +++++++++++++++++++++++++++++++++++---------
>>  2 files changed, 109 insertions(+), 26 deletions(-)
>>
>
>> diff --git a/src/network/leaseshelper.c b/src/network/leaseshelper.c
>> index c8543a2..e984cbb 100644
>> --- a/src/network/leaseshelper.c
>> +++ b/src/network/leaseshelper.c
>
>
>> @@ -260,11 +275,13 @@ main(int argc, char **argv)
>>                      goto cleanup;
>>                  if (clientid && virJSONValueObjectAppendString(lease_new, "client-id", clientid) < 0)
>>                      goto cleanup;
>> +                if (server_duid && virJSONValueObjectAppendString(lease_new, "server-duid", server_duid) < 0)
>> +                    goto cleanup;
>>                  if (expirytime && virJSONValueObjectAppendNumberLong(lease_new, "expiry-time", expirytime) < 0)
>>                      goto cleanup;
>>              }
>>          }
>> -    } else {
>> +    } else if (action != VIR_LEASE_ACTION_INIT) {
>>          fprintf(stderr, _("Unsupported action: %s\n"),
>>                  virLeaseActionTypeToString(action));
>>          exit(EXIT_FAILURE);
>> @@ -294,7 +311,7 @@ main(int argc, char **argv)
>>              i = 0;
>>              while (i < virJSONValueArraySize(leases_array)) {
>>                  const char *ip_tmp = NULL;
>> -                long long expirytime_tmp = -1;
>> +                const char *server_duid_tmp = NULL;
>>
>>                  if (!(lease_tmp = virJSONValueArrayGet(leases_array, i))) {
>>                      virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>> @@ -303,14 +320,13 @@ main(int argc, char **argv)
>>                  }
>>
>>                  if (!(ip_tmp = virJSONValueObjectGetString(lease_tmp, "ip-address")) ||
>> -                    (virJSONValueObjectGetNumberLong(lease_tmp, "expiry-time", &expirytime_tmp) < 0)) {
>> +                    (virJSONValueObjectGetNumberLong(lease_tmp, "expiry-time", &expirytime) < 0)) {
>>                      virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>>                                     _("failed to parse json"));
>>                      goto cleanup;
>>                  }
>> -
>>                  /* Check whether lease has expired or not */
>> -                if (expirytime_tmp < currtime) {
>> +                if (expirytime < currtime) {
>>                      i++;
>>                      continue;
>>                  }
>> @@ -321,6 +337,30 @@ main(int argc, char **argv)
>>                      continue;
>>                  }
>>
>> +                /* Store pointers to ipv4 and ipv6 leases */
>> +                if (strchr(ip_tmp, ':')) {
>> +                    /* This is an ipv6 lease */
>
> Is there a need to separate them? Can't we just flush them out from the
> json array in the order they are stored?
>
>> +                    ignore_value(VIR_APPEND_ELEMENT_COPY(leases_ipv6, count_ipv6, lease_tmp));
>
> It would save us the need to copy the leases separately even if dnsmasq
> isn't initializing.

I am only copying the pointer to the lease and not the lease itself.

>
> Also you should probably check the return value, otherwise you will drop
> leases silently on OOM.

Agreed.

>
>> +                    if ((server_duid_tmp
>> +                         = virJSONValueObjectGetString(lease_tmp, "server-duid"))) {
>> +                        if (!server_duid) {
>> +                            /* Control reaches here when the 'action' is not for an
>> +                             * ipv6 lease or, for some weird reason the env var
>> +                             * DNSMASQ_SERVER_DUID wasn't set*/
>> +                            server_duid = server_duid_tmp;
>> +                        }
>> +                    } else {
>> +                        /* Inject server-duid into those ipv6 leases which
>> +                         * didn't have it previously, for example, those
>> +                         * created by leaseshelper from libvirt 1.2.6 */
>> +                        if (virJSONValueObjectAppendString(lease_tmp, "server-duid", server_duid) < 0)
>> +                            goto cleanup;
>
> This part is required all the time as our format wasn't complete.

"server-duid" should be a part of every ipv6 lease. It doesn't make
sense to add it to an ipv4 lease. Hence the above hunk is required
only when we find an ipv6 lease without server-duid.

>
>> +                    }
>> +                } else {
>> +                    /* This is an ipv4 lease */
>> +                    ignore_value(VIR_APPEND_ELEMENT_COPY(leases_ipv4, count_ipv4, lease_tmp));
>
> Again, do we need to sort them explicitly?

I am not sorting anything!

>
>> +                }
>> +
>>                  /* Move old lease to new array */
>>                  if (virJSONValueArrayAppend(leases_array_new, lease_tmp) < 0) {
>>                      virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>> @@ -333,31 +373,71 @@ main(int argc, char **argv)
>>          }
>>      }
>>
>> -    if (add) {
>> +    switch ((enum virLeaseActionFlags) action) {
>> +    case VIR_LEASE_ACTION_INIT:
>> +        /* Man page of dnsmasq says: the script (helper program, in our case)
>> +         * should write the saved state of the lease database, in dnsmasq
>> +         * leasefile format, to stdout and exit with zero exit code, when
>> +         * called with argument init. Format:
>> +         * $expirytime $mac $ip $hostname $clientid # For all ipv4 leases
>> +         * duid $server-duid # If DHCPv6 is present
>> +         * $expirytime $iaid $ip $hostname $clientduid # For all ipv6 leases */
>
> Here you could just go through the json array and format each lease.

I considered that, but then since the requirement of DNSMASQ is to
print ipv4 leases first and then ipv6 leases, I would have to iterate
over the JSON array twice! (Writing to the file would be a third
iteration). I thought the extra space wouldn't matter as long as we
are not increasing the runtime. Also, I am only copying the pointer to
the leases in the JSON array, and not the complete lease itself. Do
you still think this is a bad idea?

>
>> +        for (i = 0; i < count_ipv4; i++) {
>> +            lease_tmp = leases_ipv4[i];
>> +            virJSONValueObjectGetNumberLong(lease_tmp, "expiry-time", &expirytime);
>> +            printf("%lld %s %s %s %s\n",
>> +                   expirytime,
>> +                   virJSONValueObjectGetString(lease_tmp, "mac-address"),
>> +                   virJSONValueObjectGetString(lease_tmp, "ip-address"),
>> +                   EMPTY_STR(virJSONValueObjectGetString(lease_tmp, "hostname")),
>> +                   EMPTY_STR(virJSONValueObjectGetString(lease_tmp, "client-id")));
>> +        }
>> +        if (server_duid) {
>> +            printf("duid %s\n", server_duid);
>> +            for (i = 0; i < count_ipv6; i++) {
>> +                lease_tmp = leases_ipv6[i];
>> +                virJSONValueObjectGetNumberLong(lease_tmp, "expiry-time", &expirytime);
>> +                printf("%lld %s %s %s %s\n",
>> +                       expirytime,
>> +                       virJSONValueObjectGetString(lease_tmp, "iaid"),
>> +                       virJSONValueObjectGetString(lease_tmp, "ip-address"),
>> +                       EMPTY_STR(virJSONValueObjectGetString(lease_tmp, "hostname")),
>> +                       EMPTY_STR(virJSONValueObjectGetString(lease_tmp, "client-id")));
>> +            }
>> +        }
>> +        break;
>> +
>> +    case VIR_LEASE_ACTION_OLD:
>> +    case VIR_LEASE_ACTION_ADD:
>>          if (virJSONValueArrayAppend(leases_array_new, lease_new) < 0) {
>>              virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>>                             _("failed to create json"));
>>              goto cleanup;
>>          }
>>          lease_new = NULL;
>> -    }
>>
>> -    if (!(leases_str = virJSONValueToString(leases_array_new, true))) {
>> -        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>> -                       _("empty json array"));
>> -        goto cleanup;
>> -    }
>> +    default:
>> +        if (!(leases_str = virJSONValueToString(leases_array_new, true))) {
>> +            virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>> +                           _("empty json array"));
>> +            goto cleanup;
>> +        }
>>
>> -    /* Write to file */
>> -    if (virFileRewrite(custom_lease_file, 0644,
>> -                       customLeaseRewriteFile, &leases_str) < 0)
>> -        goto cleanup;
>> +        /* Write to file */
>> +        if (virFileRewrite(custom_lease_file, 0644,
>> +                           customLeaseRewriteFile, &leases_str) < 0)
>> +            goto cleanup;
>> +    }
>>
>>      rv = EXIT_SUCCESS;
>>
>>   cleanup:
>>      if (pid_file_fd != -1)
>>          virPidFileReleasePath(pid_file, pid_file_fd);
>> +    for (i = 0; i < count_ipv4; i++)
>> +        VIR_FREE(leases_ipv4);
>> +    for (i = 0; i < count_ipv6; i++)
>> +        VIR_FREE(leases_ipv6);
>>
>>      VIR_FREE(pid_file);
>>      VIR_FREE(exptime);
>>
>
> Otherwise looks good.
>
> Peter
>

Thanks for reviewing the patch. If we decide to remove the 'pointer
copy' stuff, then I'll send v4. If not, then I'll handle the OOM cases
and then send v4.

-- 
Nehal J Wani


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