11:10 a.m.
Since fc19a0059 (network: backend functions for updating network dns
host/srv/txt, 2012-11-12), the matching logic for various network
components has been:
1) for HOST records, it's considered a match if the IP address or any
of the hostnames of an existing record matches.
2) for SRV records, it's a match if all of
domain+service+protocol+target *which have been specified* are
matched.
3) for TXT records, there is only a single field to match - name
(value can be the same for multiple records, and isn't considered a
search term), so by definition there can be no ambiguous matches.
But HOST records can have the same hostname for multiple records
(similar to TXT records with the same value). The value that needs to
be distinct for HOST records is the IP address. This commit updates
the matching logic to only consider the IP address. Compared to the
previous HOST logic:
1. You can now delete entries from an existing network like:
<dns>
<host ip="192.168.1.1">
<hostname>example</hostname>
</host>
<host ip="192.168.1.2">
<hostname>example</hostname>
</host>
</dns>
with input like:
<host ip="192.168.1.1">
</host>
or:
<host ip="192.168.1.1">
<hostname>example</hostname>
</host>
Previously, only the former would work (the latter used to raise
"multiple matching DNS HOST records were found in network").
2. You can no longer remove entries by hostname alone. Previously,
you may have been able to remove an entry from an existing network
like:
<dns>
<host ip="192.168.1.1">
<hostname>example-1</hostname>
</host>
<host ip="192.168.1.2">
<hostname>example-2</hostname>
</host>
</dns>
with input like:
<host name="example">
<hostname>example-1</hostname>
</host>
using the 'name' property to get through the partialOkay check in
virNetworkDHCPHostDefParseXML. Now that input will raise "Missing
IP address in network '%s' DNS HOST record".
3. You can now add multiple entries with a common hostname (as long as
they have distinct IP addresses). Previously, adding:
<host ip="192.168.1.1">
<hostname>example</hostname>
</host>
to an existing:
<host ip="192.168.1.2">
<hostname>example</hostname>
</host>
would have raised "there is already at least one DNS HOST record
with a matching field in network".
---
I'm actually not clear on whether the 'ip' attribute is required to be
unique or not. If not, maybe the logic should be:
* Deletes with just an IP remove all <host> entries that match that
IP.
* Deletes with just a hostname remove all <hostname> entries that
match that hostname.
* Deletes with an IP and a hostname remove matching <hostname> entries
from <host> entries which match the IP.
* If <hostname> removal completely empties a <host>, the <host> is
also removed.
Thoughts?
src/conf/network_conf.c | 31 ++++++++++---------------------
1 file changed, 10 insertions(+), 21 deletions(-)
diff --git a/src/conf/network_conf.c b/src/conf/network_conf.c
index 39a13b4..8ed62ac 100644
--- a/src/conf/network_conf.c
+++ b/src/conf/network_conf.c
@@ -587,14 +587,14 @@ virNetworkDNSHostDefParseXML(const char *networkName,
xmlNodePtr cur;
char *ip;
- if (!(ip = virXMLPropString(node, "ip")) && !partialOkay) {
+ if (!(ip = virXMLPropString(node, "ip"))) {
virReportError(VIR_ERR_XML_DETAIL,
_("Missing IP address in network '%s' DNS HOST
record"),
networkName);
goto error;
}
- if (ip && (virSocketAddrParse(&def->ip, ip, AF_UNSPEC) < 0)) {
+ if (virSocketAddrParse(&def->ip, ip, AF_UNSPEC) < 0) {
virReportError(VIR_ERR_XML_DETAIL,
_("Invalid IP address in network '%s' DNS HOST
record"),
networkName);
@@ -603,6 +603,13 @@ virNetworkDNSHostDefParseXML(const char *networkName,
}
VIR_FREE(ip);
+ if (!VIR_SOCKET_ADDR_VALID(&def->ip)) {
+ virReportError(VIR_ERR_XML_DETAIL,
+ _("Invalid IP address in network '%s' DNS HOST
record"),
+ networkName);
+ goto error;
+ }
+
cur = node->children;
while (cur != NULL) {
if (cur->type == XML_ELEMENT_NODE &&
@@ -631,13 +638,6 @@ virNetworkDNSHostDefParseXML(const char *networkName,
goto error;
}
- if (!VIR_SOCKET_ADDR_VALID(&def->ip) && def->nnames == 0) {
- virReportError(VIR_ERR_XML_DETAIL,
- _("Missing ip and hostname in network '%s' DNS HOST
record"),
- networkName);
- goto error;
- }
-
return 0;
error:
@@ -3334,18 +3334,7 @@ virNetworkDefUpdateDNSHost(virNetworkDefPtr def,
goto cleanup;
for (i = 0; i < dns->nhosts; i++) {
- bool foundThisTime = false;
-
- if (virSocketAddrEqual(&host.ip, &dns->hosts[i].ip))
- foundThisTime = true;
-
- for (j = 0; j < host.nnames && !foundThisTime; j++) {
- for (k = 0; k < dns->hosts[i].nnames && !foundThisTime; k++) {
- if (STREQ(host.names[j], dns->hosts[i].names[k]))
- foundThisTime = true;
- }
- }
- if (foundThisTime) {
+ if virSocketAddrEqual(&host.ip, &dns->hosts[i].ip) {
foundCt++;
foundIdx = i;
}
--
1.8.3.1
11:13 a.m.
New subject: [libvirt] [PATCH] virNetworkDefUpdateDNSHost: Only require IP to match
On Tue, Nov 06, 2018 at 09:10:39AM -0800, W. Trevor King wrote:
This commit update the matching logic to only consider the IP
address.
Oops, I should have updated the subject to:
virNetworkDefUpdateDNSHost: Only require IP to match
Cheers,
Trevor
--
This email may be signed or encrypted with GnuPG (http://www.gnupg.org).
For more information, see http://en.wikipedia.org/wiki/Pretty_Good_Privacy
3:25 p.m.
New subject: [libvirt] [PATCH] virNetworkDefUpdateDNSHost: Only require IP to match
I've filed [1] to track this in Bugzilla.
Cheers,
Trevor
[1]: https://bugzilla.redhat.com/show_bug.cgi?id=1647211
--
This email may be signed or encrypted with GnuPG (http://www.gnupg.org).
For more information, see http://en.wikipedia.org/wiki/Pretty_Good_Privacy
10:17 a.m.
On 11/6/18 12:10 PM, W. Trevor King wrote:
Since fc19a0059 (network: backend functions for updating network dns
host/srv/txt, 2012-11-12), the matching logic for various network
components has been:
1) for HOST records, it's considered a match if the IP address or any
of the hostnames of an existing record matches.
2) for SRV records, it's a match if all of
domain+service+protocol+target *which have been specified* are
matched.
3) for TXT records, there is only a single field to match - name
(value can be the same for multiple records, and isn't considered a
search term), so by definition there can be no ambiguous matches.
But HOST records can have the same hostname for multiple records
(similar to TXT records with the same value). The value that needs to
be distinct for HOST records is the IP address.
You're going to force me to go dig out the decades-old DNS RFCs, aren't
you? :-P (Seriously, I think we need to go back to the original source
and make sure we're interpreting it correctly before making any changes.
I can't do that right now without losing a ton of context on other
issues in my brain though...)
(but in the meantime, if something was working before (e.g. removing an
entry by hostname alone) then that needs to continue working, otherwise
some application depending on that behavior will now be broken, and
we've made promises about that not happening with libvirt.
This commit updates
the matching logic to only consider the IP address. Compared to the
previous HOST logic:
1. You can now delete entries from an existing network like:
<dns>
<host ip="192.168.1.1">
<hostname>example</hostname>
</host>
<host ip="192.168.1.2">
<hostname>example</hostname>
</host>
</dns>
with input like:
<host ip="192.168.1.1">
</host>
or:
<host ip="192.168.1.1">
<hostname>example</hostname>
</host>
Previously, only the former would work (the latter used to raise
"multiple matching DNS HOST records were found in network").
Without thinking too much about it, that (the "multiple matching ...."
error) sounds like a bug that can/should be fixed - since both hostname
and ip find only a single record, there shouldn't be an error.
2. You can no longer remove entries by hostname alone. Previously,
you may have been able to remove an entry from an existing network
like:
<dns>
<host ip="192.168.1.1">
<hostname>example-1</hostname>
</host>
<host ip="192.168.1.2">
<hostname>example-2</hostname>
</host>
</dns>
with input like:
<host name="example">
<hostname>example-1</hostname>
</host>
using the 'name' property to get through the partialOkay check in
virNetworkDHCPHostDefParseXML. Now that input will raise "Missing
IP address in network '%s' DNS HOST record".
That is a change in the behavior of the API where the previous behavior
was desired (i.e. not a bug), so not acceptable.
3. You can now add multiple entries with a common hostname (as long as
they have distinct IP addresses). Previously, adding:
<host ip="192.168.1.1">
<hostname>example</hostname>
</host>
to an existing:
<host ip="192.168.1.2">
<hostname>example</hostname>
</host>
would have raised "there is already at least one DNS HOST record
with a matching field in network".
---
I'm actually not clear on whether the 'ip' attribute is required to be
unique or not.
Well, *something* needs to be unique. Either one of the fields, or the
combination of some fields. If possible, decisions about that should be
based on the RFCs, and then if the backend implementation (dnsmasq in
this case) is any different, that should be treated as a different kind
of error.
If not, maybe the logic should be:
* Deletes with just an IP remove all <host> entries that match that
IP.
* Deletes with just a hostname remove all <hostname> entries that
match that hostname.
* Deletes with an IP and a hostname remove matching <hostname> entries
from <host> entries which match the IP.
* If <hostname> removal completely empties a <host>, the <host> is
also removed.
Thoughts?
src/conf/network_conf.c | 31 ++++++++++---------------------
1 file changed, 10 insertions(+), 21 deletions(-)
diff --git a/src/conf/network_conf.c b/src/conf/network_conf.c
index 39a13b4..8ed62ac 100644
--- a/src/conf/network_conf.c
+++ b/src/conf/network_conf.c
@@ -587,14 +587,14 @@ virNetworkDNSHostDefParseXML(const char *networkName,
xmlNodePtr cur;
char *ip;
- if (!(ip = virXMLPropString(node, "ip")) && !partialOkay) {
+ if (!(ip = virXMLPropString(node, "ip"))) {
virReportError(VIR_ERR_XML_DETAIL,
_("Missing IP address in network '%s' DNS HOST
record"),
networkName);
goto error;
}
- if (ip && (virSocketAddrParse(&def->ip, ip, AF_UNSPEC) < 0)) {
+ if (virSocketAddrParse(&def->ip, ip, AF_UNSPEC) < 0) {
virReportError(VIR_ERR_XML_DETAIL,
_("Invalid IP address in network '%s' DNS HOST
record"),
networkName);
@@ -603,6 +603,13 @@ virNetworkDNSHostDefParseXML(const char *networkName,
}
VIR_FREE(ip);
+ if (!VIR_SOCKET_ADDR_VALID(&def->ip)) {
+ virReportError(VIR_ERR_XML_DETAIL,
+ _("Invalid IP address in network '%s' DNS HOST
record"),
+ networkName);
+ goto error;
+ }
+
cur = node->children;
while (cur != NULL) {
if (cur->type == XML_ELEMENT_NODE &&
@@ -631,13 +638,6 @@ virNetworkDNSHostDefParseXML(const char *networkName,
goto error;
}
- if (!VIR_SOCKET_ADDR_VALID(&def->ip) && def->nnames == 0) {
- virReportError(VIR_ERR_XML_DETAIL,
- _("Missing ip and hostname in network '%s' DNS HOST
record"),
- networkName);
- goto error;
- }
-
return 0;
error:
@@ -3334,18 +3334,7 @@ virNetworkDefUpdateDNSHost(virNetworkDefPtr def,
goto cleanup;
for (i = 0; i < dns->nhosts; i++) {
- bool foundThisTime = false;
-
- if (virSocketAddrEqual(&host.ip, &dns->hosts[i].ip))
- foundThisTime = true;
-
- for (j = 0; j < host.nnames && !foundThisTime; j++) {
- for (k = 0; k < dns->hosts[i].nnames && !foundThisTime; k++)
{
- if (STREQ(host.names[j], dns->hosts[i].names[k]))
- foundThisTime = true;
- }
- }
- if (foundThisTime) {
+ if virSocketAddrEqual(&host.ip, &dns->hosts[i].ip) {
foundCt++;
foundIdx = i;
}
10:10 p.m.
On Wed, Nov 07, 2018 at 11:17:51AM -0500, Laine Stump wrote:
On 11/6/18 12:10 PM, W. Trevor King wrote:
> But HOST records can have the same hostname for multiple records
> (similar to TXT records with the same value). The value that
> needs to be distinct for HOST records is the IP address.
You're going to force me to go dig out the decades-old DNS RFCs,
aren't you?
The relevant RFCs are probably [1,2]. But as far as they're concened
IP <-> domain-name mappings are many to many. That doesn't really
impact libvirt's <dns><host/><dns> entries. For example:
IP hostname
192.168.1.1 alice
192.168.1.1 bob
192.168.1.2 alice
could be represented with unique IPs:
<dns>
<host ip="192.168.1.1">
<hostname>alice</hostname>
<hostname>bob</hostname>
</host>
<host ip="192.168.1.2">
<hostname>alice</hostname>
</host>
</dns>
or with repeated IPs:
<dns>
<host ip="192.168.1.1">
<hostname>alice</hostname>
</host>
<host ip="192.168.1.1">
<hostname>bob</hostname>
</host>
<host ip="192.168.1.2">
<hostname>alice</hostname>
</host>
</dns>
Depending on how generous you were feeling, you could also support
overlaps:
<dns>
<host ip="192.168.1.1">
<hostname>alice</hostname>
<hostname>bob</hostname>
</host>
<host ip="192.168.1.1">
<hostname>bob</hostname>
</host>
<host ip="192.168.1.2">
<hostname>alice</hostname>
</host>
</dns>
I know libvirt supports the unique-IP form. I haven't looked to see
whether it supports the repeated IP form (with or without overlaps).
(but in the meantime, if something was working before (e.g. removing
an entry by hostname alone) then that needs to continue working,
otherwise some application depending on that behavior will now be
broken, and we've made promises about that not happening with
libvirt.
I think continuing to support the IP/hostname-union logic makes things
too complicated. Would you have to detect the "we match too many
things and would ordinarily error out" case so you could switch on the
"they must expect this to be an IP/hostname-intersection match" logic?
How would you feel about a v2 function (a la dup2), which callers
switch on with VIR_NETWORK_SECTION_DNS_HOST2 or something to opt in to
the new logic? This would also give you a way to notice the old
section variable and log deprecation notices (does the libary have
hooks for logging?) to help get the word out, and help set the stage
for possibly removing the old logic after a few years.
> 1. You can now delete entries from an existing network like:
>
> <dns>
> <host ip="192.168.1.1">
> <hostname>example</hostname>
> </host>
> <host ip="192.168.1.2">
> <hostname>example</hostname>
> </host>
> </dns>
>
> with input like:
>
> <host ip="192.168.1.1">
> </host>
>
> or:
>
> <host ip="192.168.1.1">
> <hostname>example</hostname>
> </host>
>
> Previously, only the former would work (the latter used to raise
> "multiple matching DNS HOST records were found in network").
Without thinking too much about it, that (the "multiple matching
...." error) sounds like a bug that can/should be fixed - since
both hostname and ip find only a single record, there shouldn't be
an error.
Both <hostname> elements in the original network are "example", so
they are not unique. The current logic's IP/hostname-union logic
matches both, and errors out. I don't think this is a bug we can fix
without something ugly like "if IP/hostname-union gives multiple
matches, implicitly switch to IP/hostname-intersection" or a way to
explicitly select the more-specific logic.
> 3. You can now add multiple entries with a common hostname (as
long as
> they have distinct IP addresses). Previously, adding:
>
> <host ip="192.168.1.1">
> <hostname>example</hostname>
> </host>
>
> to an existing:
>
> <host ip="192.168.1.2">
> <hostname>example</hostname>
> </host>
>
> would have raised "there is already at least one DNS HOST record
> with a matching field in network".
> ---
>
> I'm actually not clear on whether the 'ip' attribute is required
> to be unique or not.
Well, *something* needs to be unique. Either one of the fields, or
the combination of some fields. If possible, decisions about that
should be based on the RFCs, and then if the backend implementation
(dnsmasq in this case) is any different, that should be treated as a
different kind of error.
We've had no trouble creating networks where multiple IP share a
common hostname in libvirt. The only problem I'm aware of (and the
reason for this patch) is that libvirt doesn't allow you to *update*
those networks. You currently have to delete them and then re-create
them, after which you need to re-attach your domains to the new
network.
Cheers,
Trevor
[1]: https://tools.ietf.org/html/rfc1035
[2]: https://tools.ietf.org/html/rfc1794
--
This email may be signed or encrypted with GnuPG (http://www.gnupg.org).
For more information, see http://en.wikipedia.org/wiki/Pretty_Good_Privacy
2209
days inactive
2211
days old
4 comments
2 participants
participants (2)
-
Laine Stump -
W. Trevor King