How to filter with mime types

Question

Again thanks for the help getting up and running.
Now that I am up and running I know my task at hand and I have comleted most of it except for a couple of things. Here is my task:
To have 1 URL filter lists. Lets call it WhiteList-special. What my manager wants is this.
To all URL's matching the WhiteList-special filter allow the connections filtering out a set of mime types.
To all URL's not in the WhiteList (still allow them them) but apply a different set of mime type restrictions.
How can I go about doing this? Do I use the http:// resource and set up the whitelist-special there with a mime list and then in default set up an allow list of basically .* with a different mime type list ??
Also I noticed that in the mime.types file gnu zip (.gz) was listed as an encoding and not application. Thus if I include the gz mime type in my <Filter "filter-ct" ...> line the gz seems to be ignored. I block all other mime types that are of the application type but I cannot block any encoding type. Am I doing something wrong?
thanks
Doug

Answer 1

Here is what you can do:
(the simplest way)
Use a filter that will add a variable to all the mime-types that you want to whitelist.
Then use a filter to deny all the other types. In the below code, the identity filter is the one that you can use to touch all the whitelist -- (below, it only allows text/plain), and the deny filter will deny all the rest.
To your question on content-type, check how the content-length is obtained in the below code.
-------obj.conf------------
<Object ppath="http://.*">
ObjectType fn="cache-enable" query-maxlen="10" log-report="off"
ObjectType fn="cache-setting" lm-factor="0.10" max-uncheck="7200"
Output fn="insert-filter" type="text/plain" filter="identityfilter"
Output fn="insert-filter" type="*" filter="denyfilter"
Service fn="proxy-retrieve" method="*"
</Object>
|cat identityfilter.c
* Usage:
*     At the end of magnus.conf:
*         Init fn="load-modules"
*              shlib="<path>/identityfilter.<ext>"
*              NativeThread="no"
*     Inside an object in obj.conf:
*         Output fn="insert-filter"
*                type="text/*"
*                filter="identityfilter"
#include "nsapi.h"
int identityfilter_insert(FilterLayer *layer, pblock *pb) {
    pblock_nninsert("identityfilter", 1, layer->context->rq->vars);
    return REQ_PROCEED;
void identityfilter_remove(FilterLayer *layer) {
int identityfilter_write(FilterLayer *layer, const void *buf, int amount) {
    return net_write(layer->lower, buf , amount);
NSAPI_PUBLIC int nsapi_module_init(pblock *pb, Session *sn, Request *rq) {
    FilterMethods methods = FILTER_METHODS_INITIALIZER;
    methods.insert = &identityfilter_insert;
    methods.remove = &identityfilter_remove;
    methods.write = &identityfilter_write;
    const Filter *filter = filter_create("identityfilter", FILTER_CONTENT_TRANSLATION, &methods);
    return REQ_PROCEED;
|cat denyfilter.c
* Usage:
*     At the end of magnus.conf:
*         Init fn="load-modules"
*              shlib="<path>/denyfilter.<ext>"
*              NativeThread="no"
*     Inside an object in obj.conf:
*         Output fn="insert-filter"
*                type="text/*"
*                filter="denyfilter"
#include "nsapi.h"
int denyfilter_insert(FilterLayer *layer, pblock *pb) {
    char* processed = pblock_findval("identityfilter", layer->context->rq->vars);
    if (!processed) {
        pb_param *pp = pblock_remove("content-length", layer->context->rq->srvhdrs);
        if (pp) param_free(pp);
        layer->context->data = (void*)1;
        Request* rq = layer->context->rq;
        rq->status_num = 403;
        pp = pblock_remove("status", rq->srvhdrs);
        if (pp) param_free(pp);
        pblock_nvinsert("status", "403", rq->srvhdrs);
    } else {
        layer->context->data = (void*)0;
    return REQ_PROCEED;
void denyfilter_remove(FilterLayer *layer) {
int denyfilter_write(FilterLayer *layer, const void *buf, int amount) {
    if ( layer->context->data ) return IO_ERROR;
    else return net_write(layer->lower, buf, amount);
NSAPI_PUBLIC int nsapi_module_init(pblock *pb, Session *sn, Request *rq) {
    FilterMethods methods = FILTER_METHODS_INITIALIZER;
    methods.insert = &denyfilter_insert;
    methods.remove = &denyfilter_remove;
    methods.write = &denyfilter_write;
    const Filter *filter = filter_create("denyfilter", FILTER_CONTENT_TRANSLATION, &methods);
    return REQ_PROCEED;
-----------------------------------What is my best approach? Can I simply call another Filter from mine?
check out func_exec and friends in nsapi.