Allow for wildcards in k8s ingress host, fixes #792

[sheerun]

Example ingress:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  namespace: deis
  name: deis
spec:
  rules:
  - host: "*.example.com"
    http:
      paths:
      - path: /
        backend:
          serviceName: deis-router
          servicePort: 80

[dtomcej]

The subdomain rule you implemented here does not allow for capital letters, numbers, or dashes/underscores. This means that ww2.example.com will not have a properly matched rule.

[sheerun]

@dtomcej I've changed it to allow dashes and capital letter, but I believe underscores are disallowed in domain names, aren't they?

[dtomcej]

http://stackoverflow.com/a/2183140

The commenter is correct, many services include underscores in the subdomains.

[sheerun]

@dtomcej fixed

[dtomcej]

Why not just "{subdomain:[A-Za-z0-9-_]*}"? The underscore may be the first character in the subdomain:

_test.example.com

[sheerun]

@dtomcej fixed

[dtomcej]

LGTM
Ping @containous/traefik

[errm]

LGTM

[emilevauge]

If we allow _ then we may use the same regex \\da-z\\.-_ in https://github.com/containous/traefik/blob/master/server.go#L754 :)

PS: I edited my comment, read too quickly ;)