Even though there's an accepted answer that has been highly upvoted I'd like to suggest an alternative and point out shortcomings of the accepted answer.
request.getHeader("Remote_Addr")
is specified to return exactly the same as request.getRemoteAddr()
. Hence, it makes no sense to check both. Also note that getRemoteAddr
is a method of javax.servlet.ServletRequest
(i.e. HTTP-agnostic) while getHeader
is in javax.servlet.http.HttpServletRequest
.
Furthermore, some proxies use Client-IP
rather than X-Forwarded-For
. For a discussion see https://stackoverflow.com/a/7446010/131929.
I don't know how reliable the use of HTTP_X_FORWARDED_FOR
over X-Forwarded-For
is. In Java I'd rather use the direct, short form. For a discussion see https://stackoverflow.com/a/3834169/131929. Upper/lower case makes no difference because getHeader
is specified to be case insensitive.
Java alternative
public final class ClientIpAddress {
// CHECKSTYLE:OFF
// https://stackoverflow.com/a/11327345/131929
private static Pattern PRIVATE_ADDRESS_PATTERN = Pattern.compile(
"(^127\\.)|(^192\\.168\\.)|(^10\\.)|(^172\\.1[6-9]\\.)|(^172\\.2[0-9]\\.)|(^172\\.3[0-1]\\.)|(^::1$)|(^[fF][cCdD])",
Pattern.CANON_EQ);
// CHECKSTYLE:ON
private ClientIpAddress() {
}
/**
* Extracts the "real" client IP address from the request. It analyzes request headers
* {@code REMOTE_ADDR}, {@code X-Forwarded-For} as well as {@code Client-IP}. Optionally
* private/local addresses can be filtered in which case an empty string is returned.
*
* @param request HTTP request
* @param filterPrivateAddresses true if private/local addresses (see
* https://en.wikipedia.org/wiki/Private_network#Private_IPv4_address_spaces and
* https://en.wikipedia.org/wiki/Unique_local_address) should be filtered i.e. omitted
* @return IP address or empty string
*/
public static String getFrom(HttpServletRequest request, boolean filterPrivateAddresses) {
String ip = request.getRemoteAddr();
String headerClientIp = request.getHeader("Client-IP");
String headerXForwardedFor = request.getHeader("X-Forwarded-For");
if (StringUtils.isEmpty(ip) && StringUtils.isNotEmpty(headerClientIp)) {
ip = headerClientIp;
} else if (StringUtils.isNotEmpty(headerXForwardedFor)) {
ip = headerXForwardedFor;
}
if (filterPrivateAddresses && isPrivateOrLocalAddress(ip)) {
return StringUtils.EMPTY;
} else {
return ip;
}
}
private static boolean isPrivateOrLocalAddress(String address) {
Matcher regexMatcher = PRIVATE_ADDRESS_PATTERN.matcher(address);
return regexMatcher.matches();
}
}
PHP alternative
function getIp()
{
$ip = $_SERVER['REMOTE_ADDR'];
if (empty($ip) && !empty($_SERVER['HTTP_CLIENT_IP'])) {
$ip = $_SERVER['HTTP_CLIENT_IP'];
} elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
// omit private IP addresses which a proxy forwarded
$tmpIp = $_SERVER['HTTP_X_FORWARDED_FOR'];
$tmpIp = filter_var(
$tmpIp,
FILTER_VALIDATE_IP,
FILTER_FLAG_IPV4 | FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE
);
if ($tmpIp != false) {
$ip = $tmpIp;
}
}
return $ip;
}