Make the internal DNS resolver for Windows containers forward requests
to upsteam DNS servers when it cannot respond itself, rather than
returning SERVFAIL.
Windows containers are normally configured with the internal resolver
first for service discovery (container name lookup), then external
resolvers from '--dns' or the host's networking configuration.
When a tool like ping gets a SERVFAIL from the internal resolver, it
tries the other nameservers. But, nslookup does not, and with this
change it does not need to.
The internal resolver learns external server addresses from the
container's HNSEndpoint configuration, so it will use the same DNS
servers as processes in the container.
The internal resolver for Windows containers listens on the network's
gateway address, and each container may have a different set of external
DNS servers. So, the resolver uses the source address of the DNS request
to select external resolvers.
On Windows, daemon.json feature option 'windows-no-dns-proxy' can be used
to prevent the internal resolver from forwarding requests (restoring the
old behaviour).
Signed-off-by: Rob Murray <rob.murray@docker.com>
Commit cbc2a71c2 makes `connect` syscall fail fast when a container is
only attached to an internal network. Thanks to that, if such a
container tries to resolve an "external" domain, the embedded resolver
returns an error immediately instead of waiting for a timeout.
This commit makes sure the embedded resolver doesn't even try to forward
to upstream servers.
Co-authored-by: Albin Kerouanton <albinker@gmail.com>
Signed-off-by: Rob Murray <rob.murray@docker.com>
I noticed that this log didn't use structured logs;
[resolver] failed to query DNS server: 10.115.11.146:53, query: ;google.com.\tIN\t A" error="read udp 172.19.0.2:46361->10.115.11.146:53: i/o timeout
[resolver] failed to query DNS server: 10.44.139.225:53, query: ;google.com.\tIN\t A" error="read udp 172.19.0.2:53991->10.44.139.225:53: i/o timeout
But other logs did;
DEBU[2024-02-20T15:48:51.026704088Z] [resolver] forwarding query client-addr="udp:172.19.0.2:39661" dns-server="udp:192.168.65.7:53" question=";google.com.\tIN\t A"
DEBU[2024-02-20T15:48:51.028331088Z] [resolver] forwarding query client-addr="udp:172.19.0.2:35163" dns-server="udp:192.168.65.7:53" question=";google.com.\tIN\t AAAA"
DEBU[2024-02-20T15:48:51.057329755Z] [resolver] received AAAA record "2a00:1450:400e:801::200e" for "google.com." from udp:192.168.65.7
DEBU[2024-02-20T15:48:51.057666880Z] [resolver] received A record "142.251.36.14" for "google.com." from udp:192.168.65.7
As we're already constructing a logger with these fields, we may as well use it.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
If the resolver's DNSBackend returns a name that cannot be marshaled
into a well-formed DNS message, the resolver will only discover this
when it attempts to write the reply message and it fails with an error.
No reply message is sent, leaving the client to wait out its timeout and
the user in the dark about what went wrong.
When writing the intended reply message fails, retry once with a
ServFail response to inform the client and user that the DNS query was
not resolved due to a problem with to the resolver, not the network.
Signed-off-by: Cory Snider <csnider@mirantis.com>
The github.com/containerd/containerd/log package was moved to a separate
module, which will also be used by upcoming (patch) releases of containerd.
This patch moves our own uses of the package to use the new module.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This change creates a few OTEL spans and plumb context through the DNS
resolver and DNS backends (ie. Sandbox and Network). This should help
better understand how much lock contention impacts performance, and
help debug issues related to DNS queries (we basically have no
visibility into what's happening here right now).
Signed-off-by: Albin Kerouanton <albinker@gmail.com>
Slightly refactor Resolver.dialExtDNS:
- use net.JoinHostPort to properly format IPv6 addresses
- define a const for the default port, and avoid int -> string
conversion if no custom port is defined
- slightly simplify logic if the HostLoopback is used (at the cost of
duplicating one line); in that case we don't need to define the closure
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This function was added in 36fd9d02be
(libnetwork: ce6c6e8c35),
because there were multiple places where a DNS response was created,
which had to use the same options. However, new "common" options were
added since, and having it in a function separate from the other (also
common) options was just hiding logic, so let's remove it.
What the above probably _should_ have done was to create a common utility
to create a DNS response (as all other options are shared as well). This
was actually done in 0c22e1bd07 (libnetwork:
be3531759b),
which added a `createRespMsg` utility, but missed that it could be used
for both cases.
This patch:
- removes the setCommonFlags function
- uses createRespMsg instead to share common options
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Swapping out the global logger on the fly is causing tests to flake out
by logging to a test's log output after the test function has returned.
Refactor Resolver to use a dependency-injected logger and the resolver
unit tests to inject a private logger instance into the Resolver under
test.
Signed-off-by: Cory Snider <csnider@mirantis.com>
Our resolver is just a forwarder for external DNS so it should act like
it. Unless it's a server failure or refusal, take the response at face
value and forward it along to the client. RFC 8020 is only applicable to
caching recursive name servers and our resolver is neither caching nor
recursive.
Signed-off-by: Cory Snider <csnider@mirantis.com>
PTR queries with domain names unknown to us are not necessarily invalid.
Act like a well-behaved middlebox and fall back to forwarding
externally, same as we do with the other query types.
Signed-off-by: Cory Snider <csnider@mirantis.com>
...for limiting concurrent external DNS requests with
"golang.org/x/sync/semaphore".Weighted. Replace the ad-hoc rate limiter
for when the concurrency limit is hit (which contains a data-race bug)
with "golang.org/x/time/rate".Sometimes.
Immediately retrying with the next server if the concurrency limit has
been hit just further compounds the problem. Wait on the semaphore and
refuse the query if it could not be acquired in a reasonable amount of
time.
Signed-off-by: Cory Snider <csnider@mirantis.com>
It handles figuring out the UDP receive buffer size and setting IO
timeouts, which simplifies our code. It is also more robust to receiving
UDP replies to earlier queries which timed out.
Log failures to perform a client exchange at level error so they are
more visible to operators and administrators.
Signed-off-by: Cory Snider <csnider@mirantis.com>
forwardExtDNS() will now continue with the next external DNS sever if
co.ReadMsg() returns (nil, nil). Previously it would abort resolving the
query and not reply to the container client. The implementation of
ReadMsg() in the currently- vendored version of miekg/dns cannot return
(nil, nil) so the difference is immaterial in practice.
Signed-off-by: Cory Snider <csnider@mirantis.com>
(*dns.Msg).Truncate() is more intelligent and standards-compliant about
truncating DNS response messages than our hand-rolled version. Fix a
silly fencepost error the max TCP message size: the limit is
dns.MaxMsgSize (65535), full stop.
Signed-off-by: Cory Snider <csnider@mirantis.com>
The TC flag in a DNS message indicates that the sender had to
truncate it to fit within the length limit of the transmission channel.
It does NOT indicate that part of the message was lost before reaching
the recipient. Older versions of github.com/miekg/dns conflated the two
cases by returning ErrTruncated from ReadMsg() if the message was parsed
without error but had the TC flag set. The version of miekg/dns
currently vendored no longer returns an error when a well-formed DNS
message is received which has its TC flag set, but there was some
confusion on how to update libnetwork to deal with this behaviour
change. Truncated DNS replies are no longer different from any other
reply message: they are normal replies which do not need any special-
case handling to proxy back to the client.
Signed-off-by: Cory Snider <csnider@mirantis.com>
If the resolver encounters an error before it attempts to forward the
request to external DNS, do not try to log information about the
external connection, because at this point `extConn` is `nil`. This
makes sure `dockerd` won't panic and crash from a nil pointer
dereference when it sees an invalid DNS query.
fixes#44979
Signed-off-by: er0k <er0k@er0k.net>
(cherry picked from commit 6c2637be11)
Signed-off-by: Bjorn Neergaard <bneergaard@mirantis.com>
"math/rand".Seed
- Migrate to using local RNG instances.
"archive/tar".TypeRegA
- The deprecated constant tar.TypeRegA is the same value as
tar.TypeReg and so is not needed at all.
Signed-off-by: Cory Snider <csnider@mirantis.com>
libnetwork/etchosts/etchosts_test.go:167:54: empty-lines: extra empty line at the end of a block (revive)
libnetwork/osl/route_linux.go:185:74: empty-lines: extra empty line at the start of a block (revive)
libnetwork/osl/sandbox_linux_test.go:323:36: empty-lines: extra empty line at the start of a block (revive)
libnetwork/bitseq/sequence.go:412:48: empty-lines: extra empty line at the start of a block (revive)
libnetwork/datastore/datastore_test.go:67:46: empty-lines: extra empty line at the end of a block (revive)
libnetwork/datastore/mock_store.go:34:60: empty-lines: extra empty line at the end of a block (revive)
libnetwork/iptables/firewalld.go:202:44: empty-lines: extra empty line at the end of a block (revive)
libnetwork/iptables/firewalld_test.go:76:36: empty-lines: extra empty line at the end of a block (revive)
libnetwork/iptables/iptables.go:256:67: empty-lines: extra empty line at the end of a block (revive)
libnetwork/iptables/iptables.go:303:128: empty-lines: extra empty line at the start of a block (revive)
libnetwork/networkdb/cluster.go:183:72: empty-lines: extra empty line at the end of a block (revive)
libnetwork/ipams/null/null_test.go:44:38: empty-lines: extra empty line at the end of a block (revive)
libnetwork/drivers/macvlan/macvlan_store.go:45:52: empty-lines: extra empty line at the end of a block (revive)
libnetwork/ipam/allocator_test.go:1058:39: empty-lines: extra empty line at the start of a block (revive)
libnetwork/drivers/bridge/port_mapping.go:88:111: empty-lines: extra empty line at the end of a block (revive)
libnetwork/drivers/bridge/link.go:26:90: empty-lines: extra empty line at the end of a block (revive)
libnetwork/drivers/bridge/setup_ipv6_test.go:17:34: empty-lines: extra empty line at the end of a block (revive)
libnetwork/drivers/bridge/setup_ip_tables.go:392:4: empty-lines: extra empty line at the start of a block (revive)
libnetwork/drivers/bridge/bridge.go:804:50: empty-lines: extra empty line at the start of a block (revive)
libnetwork/drivers/overlay/ov_serf.go:183:29: empty-lines: extra empty line at the start of a block (revive)
libnetwork/drivers/overlay/ov_utils.go:81:64: empty-lines: extra empty line at the end of a block (revive)
libnetwork/drivers/overlay/peerdb.go:172:67: empty-lines: extra empty line at the start of a block (revive)
libnetwork/drivers/overlay/peerdb.go:209:67: empty-lines: extra empty line at the start of a block (revive)
libnetwork/drivers/overlay/peerdb.go:344:89: empty-lines: extra empty line at the start of a block (revive)
libnetwork/drivers/overlay/peerdb.go:436:63: empty-lines: extra empty line at the start of a block (revive)
libnetwork/drivers/overlay/overlay.go:183:36: empty-lines: extra empty line at the start of a block (revive)
libnetwork/drivers/overlay/encryption.go:69:28: empty-lines: extra empty line at the end of a block (revive)
libnetwork/drivers/overlay/ov_network.go:563:81: empty-lines: extra empty line at the start of a block (revive)
libnetwork/default_gateway.go:32:43: empty-lines: extra empty line at the start of a block (revive)
libnetwork/errors_test.go:9:40: empty-lines: extra empty line at the start of a block (revive)
libnetwork/service_common.go:184:64: empty-lines: extra empty line at the end of a block (revive)
libnetwork/endpoint.go:161:55: empty-lines: extra empty line at the end of a block (revive)
libnetwork/store.go:320:33: empty-lines: extra empty line at the end of a block (revive)
libnetwork/store_linux_test.go:11:38: empty-lines: extra empty line at the end of a block (revive)
libnetwork/sandbox.go:571:36: empty-lines: extra empty line at the start of a block (revive)
libnetwork/service_common.go:317:246: empty-lines: extra empty line at the start of a block (revive)
libnetwork/endpoint.go:550:17: empty-lines: extra empty line at the end of a block (revive)
libnetwork/sandbox_dns_unix.go:213:106: empty-lines: extra empty line at the start of a block (revive)
libnetwork/controller.go:676:85: empty-lines: extra empty line at the end of a block (revive)
libnetwork/agent.go:876:60: empty-lines: extra empty line at the end of a block (revive)
libnetwork/resolver.go:324:69: empty-lines: extra empty line at the end of a block (revive)
libnetwork/network.go:1153:92: empty-lines: extra empty line at the end of a block (revive)
libnetwork/network.go:1955:67: empty-lines: extra empty line at the start of a block (revive)
libnetwork/network.go:2235:9: empty-lines: extra empty line at the start of a block (revive)
libnetwork/libnetwork_internal_test.go:336:26: empty-lines: extra empty line at the start of a block (revive)
libnetwork/resolver_test.go:76:35: empty-lines: extra empty line at the end of a block (revive)
libnetwork/libnetwork_test.go:303:38: empty-lines: extra empty line at the end of a block (revive)
libnetwork/libnetwork_test.go:985:46: empty-lines: extra empty line at the end of a block (revive)
libnetwork/ipam/allocator_test.go:1263:37: empty-lines: extra empty line at the start of a block (revive)
libnetwork/errors_test.go:9:40: empty-lines: extra empty line at the end of a block (revive)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
The correct formatting for machine-readable comments is;
//<some alphanumeric identifier>:<options>[,<option>...][ // comment]
Which basically means:
- MUST NOT have a space before `<identifier>` (e.g. `nolint`)
- Identified MUST be alphanumeric
- MUST be followed by a colon
- MUST be followed by at least one `<option>`
- Optionally additional `<options>` (comma-separated)
- Optionally followed by a comment
Any other format will not be considered a machine-readable comment by `gofmt`,
and thus formatted as a regular comment. Note that this also means that a
`//nolint` (without anything after it) is considered invalid, same for `//#nosec`
(starts with a `#`).
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
- don't pass the query's quetion.name separately, as we're already
passing the query itself.
- remove a "fallthrough" in favor of combining the cases in the switch
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
- Make sure all log messages have the `[resolver]` prefix
- Use `logrus.WithError()` consistently
- Improve information included in some logs
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This was added in b3c883bb2f, but resulted
in a panic if the embedded DNS had to handle an unsupported query-type,
such as ANY.
This patch adds a debug log for this case (to better describe how it's
handled.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
These were purposefully ignored before but this goes ahead and "fixes"
most of them.
Note that none of the things gosec flagged are problematic, just
quieting the linter here.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
After moving libnetwork to this repo, we need to update all the import
paths for libnetwork to point to docker/docker/libnetwork instead of
docker/libnetwork.
This change implements that.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
Commit 2a480d515e updated the DNS library
and updated the error handling.
Due to changes in the library, we now had to check the response itself
to check if the response was truncated (Truncated DNS replies should
be sent to the client so that the client can retry over TCP).
However, 1e02aae252 added an incorrect
`nil` check to fix a panic, which ignored situations where
an error was returned, but no response (for example, if we failed
to connect to the DNS server).
In that situation, the error would be ignored, and further down we
would consider the connection to have been succesfull, but the DNS
server not returning a result.
After a "successful" lookup (but no results), we break the loop,
and don't attempt lookups in other DNS servers.
Versions before 1e02aae252 would produce:
Name To resolve: bbc.co.uk.
[resolver] query bbc.co.uk. (A) from 172.21.0.2:36181, forwarding to udp:192.168.5.1
[resolver] read from DNS server failed, read udp 172.21.0.2:36181->192.168.5.1:53: i/o timeout
[resolver] query bbc.co.uk. (A) from 172.21.0.2:38582, forwarding to udp:8.8.8.8
[resolver] received A record "151.101.0.81" for "bbc.co.uk." from udp:8.8.8.8
[resolver] received A record "151.101.192.81" for "bbc.co.uk." from udp:8.8.8.8
[resolver] received A record "151.101.64.81" for "bbc.co.uk." from udp:8.8.8.8
[resolver] received A record "151.101.128.81" for "bbc.co.uk." from udp:8.8.8.8
Versions after that commit would ignore the error, and stop further lookups:
Name To resolve: bbc.co.uk.
[resolver] query bbc.co.uk. (A) from 172.21.0.2:59870, forwarding to udp:192.168.5.1
[resolver] external DNS udp:192.168.5.1 returned empty response for "bbc.co.uk."
This patch updates the logic to handle the error to log the error (and continue with the next DNS):
- if an error is returned, and no response was received
- if an error is returned, but it was not related to a truncated response
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Signed-off-by: Tibor Vass <tibor@docker.com>
Under certain conditions it appears that the DNS response and returned
error can be nil. When this happens, checking resp.Truncated results in
a nil panic so we must first check that the response is not nil before
checking if a truncated response was received.
See moby/moby#40715
Signed-off-by: Sam Whited <sam@samwhited.com>
RFC434 states that DNS Servers should be case insensitive
This commit makes sure that all DNS queries will be translated
to lower ASCII characters and all svcRecords will be saved in
lower case to abide by the RFC
Relates to https://github.com/moby/moby/issues/21169
Signed-off-by: Arko Dasgupta <arko.dasgupta@docker.com>
- NXDOMAIN is an authoritive answer, so when receiving an NXDOMAIN, we're done.
From RFC 1035: Name Error - Meaningful only for responses from an authoritative
name server, this code signifies that the domain name referenced in the query
does not exist.
FROM RFC 8020: When an iterative caching DNS resolver receives an NXDOMAIN
response, it SHOULD store it in its cache and then all names and resource
record sets (RRsets) at or below that node SHOULD be considered unreachable.
Subsequent queries for such names SHOULD elicit an NXDOMAIN response.
- REFUSED can be a transitional status: (https://www.ietf.org/rfc/rfc1035.txt)
The name server refuses to perform the specified operation for
policy reasons. For example, a name server may not wish to provide the
information to the particular requester, or a name server may not wish to
perform a particular operation (e.g., zone)
Other errors are now logged as debug-message, which can be useful for
troubleshooting.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This addresses/alleviates https://github.com/docker/libnetwork/issues/2214
The new proposed limit should remediate the issue for most users.
Signed-off-by: Thiago Alves Silva <thiago.alves@aurea.com>
