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host2regex: doesn't take in consideration * #3296

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host2regex: doesn't take in consideration * #3296

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@MustafaSaber MustafaSaber commented Nov 1, 2024 •
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converting host from Ingress/RouteGroup for Host predicate doesn't take into consideration that Ingress support wildcard hostnames (see https://kubernetes.io/docs/concepts/services-networking/ingress/#hostname-wildcards) and we produce invalid regex

This PR adds testcases to reproduce the error, requires fix before merging.

following ingress produce

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: simple
  labels:
    name: simple
spec:
  rules:
  - host: "*.example.org"
    http:
      paths:
      - pathType: Prefix
        path: "/"
        backend:
          service:
            name: simple
            port: 
              number: 80

Error:

[APP]time="2024-11-01T12:43:46Z" level=error msg="kube_default__simple_redirect_app_default_0____example_org_____ [2]: error parsing regexp: missing argument to repetition operator: *

fixes #3297

@MustafaSaber MustafaSaber added the bugfix Bug fixes and patches label Nov 1, 2024
@MustafaSaber MustafaSaber mentioned this pull request Nov 1, 2024
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maybe it's not a good idea to have this at all

MustafaSaber
MustafaSaber commented Nov 1, 2024
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dataclients/kubernetes/hosts_test.go
},
} {
t.Run(ti.msg, func(t *testing.T) {
regex := createHostRx(ti.host)
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another idea is to update validation webhook to say if the host regex is valid

@MustafaSaber MustafaSaber added do-not-merge major moderate risk, for example new API, small filter changes that have no risk like refactoring or logs labels Nov 1, 2024
szuecs
szuecs reviewed Nov 1, 2024
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dataclients/kubernetes/testdata/ingressV1/ingress-data/wildcard-ing-prefix.eskip Outdated
@@ -0,0 +1,3 @@
kube_foo__qux____example_org_____qux:
Host("^([a-z0-9]+(-[a-z0-9]+)?[.]example[.]org[.]?(:[0-9]+)?)$") && PathSubtree("/")
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I think you want
^([a-z0-9][a-z0-9-]*)?[.]example....

Better also to write down in the issue what kind of match or regexp you want to create.

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I want to match a valid hostname, it can't end or start with - I think this ([a-z0-9][a-z0-9-]*) can end with -

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@szuecs szuecs Nov 5, 2024 •
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What about foo-bar-qux.example , that your regexp doesn't match?

maybe:

^[a-z0-9]([a-z0-9-]*[a-z0-9])?[.]example....

Not sure if we need the capture group for the full first part of the hostname.

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updated the PR to match it, the new regex [a-z0-9]+((-[a-z0-9]+)?)*

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See #3297 (comment)

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@szuecs

A problem with the current implementation is that a request can flap between 2 or more routes

request to foo.example with

r: Host("*.example") -> <shunt>;
s: Host("foo.example") -> <shunt>;

@MustafaSaber MustafaSaber marked this pull request as draft November 8, 2024 10:17
AlexanderYastrebov
AlexanderYastrebov reviewed Nov 15, 2024
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dataclients/kubernetes/hosts.go
@@ -15,6 +15,9 @@ func createHostRx(hosts ...string) string {

hrx := make([]string, len(hosts))
for i, host := range hosts {
if strings.HasPrefix(host, "*.") {
host = strings.Replace(host, "*", "[a-z0-9]+((-[a-z0-9]+)?)*", 1)
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We need to verify this matches behaviour descibed at https://kubernetes.io/docs/concepts/services-networking/ingress/#hostname-wildcards

Makes sense to add this link as a comment.

Subdomain regexp looks strange with two capture groups using ? followed by *.

I guess subdomain shoud start and end with alphanumeric (not dash). Lets check this https://stackoverflow.com/questions/7930751/regexp-for-subdomain and similar answers and reuse/adopt regexp from there.

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wildcard hostnames produce invalid regex for Host predicate
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@MustafaSaber @szuecs @AlexanderYastrebov