HTTP Redirect(如HTTP 301，HTTP 302)不允许无限循环重定向，否则会出现错误提示，如Chrome：

Error 310 (net::ERR_TOO_MANY_REDIRECTS): There were too many redirects.

这在HTTP 1.1规范中有明确要求：

A client SHOULD detect infinite redirection loops, since such loops generate network traffic for each redirection.
via:http://www.ietf.org/rfc/rfc2616.txt

HTTP 1.0中，最多允许5次连续的HTTP Redirect。

Note: previous versions of this specification recommended a
maximum of five redirections. Content developers should be aware
that there might be clients that implement such a fixed
limitation.
via:http://www.ietf.org/rfc/rfc2616.txt

HTTP 1.1未有明确的次数限制，现实中的情况是：

• Chrome 和 Firefox最多允许20次HTTP Redirect。

Maximum number of redirects to follow per request. Default: 20.
via:http://kb.mozillazine.org/Network.http.redirection-limit

• IE 7/8允许最多10次连续HTTP Redirect，IE 6/9允许超过100次。
  via:http://stackoverflow.com/questions/9384474/in-chrome-how-many-redirects-are-too-many

综合结论：最多5次HTTP Redirect是安全的。