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mw/kubernetes: Rewrite parseRequest and Readability improvements (#939)

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* mw/kubernetes: rewrite parseRequest

Stop looking at the qtype in parseRequest and make k.Namespace a map.
Fallout from this is that pkg/strings as it is not used anymore. Also
add a few helper functions to make unexposed namespaces easier to see in
the code.

Add wildcard tests to the middleware tests.

* Fix tests

Add a whole bunch of comments to document what we are trying to do.

* This is now answered

* up coverage

* duh

* Update testcase

* Make it nodata
This commit is contained in:
Miek Gieben 2017-08-22 20:44:42 +01:00 • committed by Yong Tang
parent 60d5e71a1a
commit 6a4e69eb9f
9 changed files with 189 additions and 168 deletions
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125
middleware/kubernetes/parse.go
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@ -13,80 +13,87 @@ type recordRequest struct {
port string
// The protocol is usually _udp or _tcp (if set), and comes from the protocol part of a well formed
// SRV record.
protocol string
endpoint string
service string
protocol string
endpoint string
// The servicename used in Kubernetes.
service string
// The namespace used in Kubernetes.
namespace string
// A each name can be for a pod or a service, here we track what we've seen. This value is true for
// pods and false for services. If we ever need to extend this well use a typed value.
// A each name can be for a pod or a service, here we track what we've seen, either "pod" or "service".
podOrSvc string
}
// parseRequest parses the qname to find all the elements we need for querying k8s.
// parseRequest parses the qname to find all the elements we need for querying k8s. Anything
// that is not parsed will have the wildcard "*" value (except r.endpoint).
// Potential underscores are stripped from _port and _protocol.
func (k *Kubernetes) parseRequest(state request.Request) (r recordRequest, err error) {
// 3 Possible cases:
// o SRV Request: _port._protocol.service.namespace.type.zone
// o A Request (endpoint): endpoint.service.namespace.type.zone
// o A Request (service): service.namespace.type.zone
// Federations are handled in the federation middleware.
// 1. _port._protocol.service.namespace.pod|svc.zone
// 2. (endpoint): endpoint.service.namespace.pod|svc.zone
// 3. (service): service.namespace.pod|svc.zone
//
// Federations are handled in the federation middleware. And aren't parsed here.
base, _ := dnsutil.TrimZone(state.Name(), state.Zone)
segs := dns.SplitDomainName(base)
offset := 0
if state.QType() == dns.TypeSRV {
// The kubernetes peer-finder expects queries with empty port and service to resolve
// If neither is specified, treat it as a wildcard
if len(segs) == 3 {
r.port = "*"
r.service = "*"
offset = 0
} else {
if len(segs) != 5 {
return r, errInvalidRequest
}
// This is a SRV style request, get first two elements as port and
// protocol, stripping leading underscores if present.
if segs[0][0] == '_' {
r.port = segs[0][1:]
} else {
r.port = segs[0]
if !wildcard(r.port) {
return r, errInvalidRequest
}
}
if segs[1][0] == '_' {
r.protocol = segs[1][1:]
if r.protocol != "tcp" && r.protocol != "udp" {
return r, errInvalidRequest
}
} else {
r.protocol = segs[1]
if !wildcard(r.protocol) {
return r, errInvalidRequest
}
}
if r.port == "" || r.protocol == "" {
return r, errInvalidRequest
}
offset = 2
}
}
if (state.QType() == dns.TypeA || state.QType() == dns.TypeAAAA) && len(segs) == 4 {
// This is an endpoint A/AAAA record request. Get first element as endpoint.
r.endpoint = segs[0]
offset = 1
}
r.port = "*"
r.protocol = "*"
r.service = "*"
r.namespace = "*"
// r.endpoint is the odd one out, we need to know if it has been set or not. If it is
// empty we should skip the endpoint check in k.get(). Hence we cannot set if to "*".
if len(segs) == (offset + 3) {
r.service = segs[offset]
r.namespace = segs[offset+1]
r.podOrSvc = segs[offset+2]
// start at the right and fill out recordRequest with the bits we find, so we look for
// pod|svc.namespace.service and then either
// * endpoint
// *_protocol._port
last := len(segs) - 1
r.podOrSvc = segs[last]
if r.podOrSvc != Pod && r.podOrSvc != Svc {
return r, errInvalidRequest
}
last--
if last < 0 {
return r, nil
}
return r, errInvalidRequest
r.namespace = segs[last]
last--
if last < 0 {
return r, nil
}
r.service = segs[last]
last--
if last < 0 {
return r, nil
}
// Becuase of ambiquity we check the labels left: 1: an endpoint. 2: port and protocol.
// Anything else is a query that is too long to answer and can safely be delegated to return an nxdomain.
switch last {
case 0: // endpoint only
r.endpoint = segs[last]
case 1: // service and port
r.protocol = stripUnderscore(segs[last])
r.port = stripUnderscore(segs[last-1])
default: // too long
return r, errInvalidRequest
}
return r, nil
}
// stripUnderscore removes a prefixed underscore from s.
func stripUnderscore(s string) string {
if s[0] != '_' {
return s
}
return s[1:]
}
// String return a string representation of r, it just returns all fields concatenated with dots.