2: header already sent
Roman Arutyunyan
arut at nginx.com
Sun Jul 15 05:26:10 UTC 2018
Hi,
On Sat, Jul 14, 2018 at 05:21:02PM -0700, Dk Jack wrote:
> Hi Roman,
> Thanks for taking the time to respond to my question.
>
> I've tried your suggestion. I've done a finalize_req and tried
> NGX_DONE/OK/... All give me the same result. I get the same result with or
> without the finalize_req i.e. I still see the 'header already sent'
> message. I've experimented with the different 'rc' values for the
> finalize_req i.e. 'rc = NGX_DONE/OK/ERROR' as well. I still see the same
> result. Please let me know if you have any other suggestions you'd like me
> to try. Thanks.
Can you show your debug log?
https://nginx.org/en/docs/debugging_log.html
> On Sat, Jul 14, 2018 at 2:37 PM Roman Arutyunyan <arut at nginx.com> wrote:
>
> > Hi Dk Jack,
> >
> > On Fri, Jul 13, 2018 at 01:18:40PM -0700, Dk Jack wrote:
> > > Sorry, I made a typo in my earlier email. Please read the following
> > > sentence:
> > >
> > > "When I send the response in the *content* phase handler, I am am seeing
> > > 'header already sent' messages in the error log."
> > >
> > > as
> > >
> > > "When I send the response in the *access* phase handler, I am am seeing
> > > 'header already sent' messages in the error log."
> >
> > That's because you do not finalize the request after you send a response in
> > the access handler. A content handler (standard static or another one) is
> > still called at the content phase. It tries to send a second response and
> > obviously gets this error.
> >
> > Finalize the request in the access phase after you send the response with
> > this call:
> >
> > ngx_http_finalize_request(r, rc)
> >
> > where rc is what ngx_http_output_filter() returned. Then return NGX_DONE
> > from the access handler to prevent further request processing.
> >
> > If you want to return a standard error page, simply return its HTTP status
> > code
> > from your access handler instead.
> >
> > > On Thu, Jul 12, 2018 at 1:29 PM Dk Jack <dnj0496 at gmail.com> wrote:
> > >
> > > > Hi,
> > > > Sorry for sending this again. I haven't been able to resolve my issue.
> > > > I've read several modules for example and gone over several docs etc.
> > but
> > > > with no success so far.
> > > >
> > > > In my module, I need to either drop the request or allow the request.
> > When
> > > > I drop the request, I need to send custom response and status. The
> > custom
> > > > response and status don't come from the config file. When I send the
> > > > response in the content phase handler, I am am seeing 'header already
> > sent'
> > > > messages in the error log. How can prevent further processing of the
> > > > request after my handler is called for the terminal case?
> > > >
> > > > Since my module needs to examine all requests irrespective of the uri,
> > I
> > > > tried registering a content phase handler and send the custom response
> > in
> > > > that handler. However, my content phase handler is never invoked. I
> > suspect
> > > > some other content handler is overriding my content handler. Is there
> > a
> > > > way I can prevent that i.e. for a request, can I force only my content
> > > > handler to be called.
> > > >
> > > > Please let me know what I am doing wrong? I just need to send/perform
> > > > custom response/actions when a request matches my criteria. I've
> > include a
> > > > skeleton of my code.
> > > > Any inputs are greatly appreciated. Thanks.
> > > >
> > > > regards,
> > > > Dk.
> > > >
> > > > http_mod_send_response(ngx_http_request_t *r, ngx_uint_t custom_status,
> > > > char *body, ngx_int_t blen)
> > > > {
> > > > ngx_int_t rc;
> > > > ngx_log_t *log = r->connection->log;
> > > > ngx_buf_t *buf = ngx_create_temp_buf(r->pool, (blen+16)); // pad.
> > > >
> > > > if (NULL == buf) {
> > > > ngx_log_error(NGX_LOG_ERR, log, 0, "%s: Failed to allocate buffer",
> > > > __FUNCTION__);
> > > > return NGX_ERROR;
> > > > }
> > > >
> > > > buf->last = ngx_copy(buf->start, (unsigned char*) data, dlen);
> > > > rc = ngx_http_discard_request_body(r);
> > > > if (rc != NGX_OK) {
> > > > ngx_log_error(NGX_LOG_ERR, log, 0, "%s: Discard req. body failed.
> > > > rc=%i", __FUNCTION__, rc);
> > > > return rc;
> > > > }
> > > >
> > > > r->headers_out.status = custom_status;
> > > > r->headers_out.content_length_n = buf->last - buf->pos;
> > > > r->headers_out.content_type.len = sizeof("text/plain") - 1;
> > > > r->headers_out.content_type.data = (u_char *) "text/plain";
> > > >
> > > > rc = ngx_http_send_header(r);
> > > > if (rc == NGX_ERROR || rc > NGX_OK || r->header_only) {
> > > > ngx_log_error(NGX_LOG_ERR, log, 0, "%s: Send header failed. rc=%i",
> > > > __FUNCTION__, rc);
> > > > return rc;
> > > > }
> > > >
> > > > ngx_chain_t *out_chain = ngx_alloc_chain_link(r->pool);
> > > > if (NULL == out_chain) {
> > > > ngx_log_error(NGX_LOG_ERR, log, 0, "%s: Buffer chain alloc failed",
> > > > __FUNCTION__);
> > > > return NGX_ERROR;
> > > > }
> > > >
> > > > out_chain->buf = buf;
> > > > out_chain->next = NULL;
> > > > buf->last_buf = 1;
> > > > buf->last_in_chain = 1;
> > > >
> > > > return ngx_http_output_filter(r, out_chain);
> > > > }
> > > >
> > > > typedef struct {
> > > > unsigned done:1;
> > > > } ngx_http_mod_ctx_t;
> > > >
> > > > int
> > > > http_module_process_request(ngx_http_request_t *r, ngx_uint_t *status,
> > > > char *body, ngx_uint_t *blen)
> > > > {
> > > > if (/* request matches criteria */) {
> > > > /* other boiler plate code */
> > > > *status = get_custom_status();
> > > > *body = get_custom_body();
> > > > *blen = ngx_strlen(body);
> > > > return *status; // this can be different from custom status.
> > > > }
> > > >
> > > > return NGX_DECLINED;
> > > > }
> > > >
> > > > static ngx_int_t
> > > > ngx_http_request_handler(ngx_http_request_t *r)
> > > > {
> > > > ngx_http_mod_ctx_t *ctx = ngx_http_get_module_ctx(r,
> > nginx_http_module);
> > > >
> > > > if (ctx) {
> > > > ngx_log_error(NGX_LOG_DEBUG, r->connection->log, 0, "duplicate
> > > > invokation");
> > > > return NGX_DECLINED;
> > > > } else {
> > > > ctx = ngx_palloc(r->connection->pool, sizeof(ngx_http_mod_ctx_t));
> > > > if (ctx == NULL) {
> > > > ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
> > > > "Out of memory. Cannot allocate context");
> > > > return NGX_ERROR;
> > > > }
> > > >
> > > > ctx->done = 0;
> > > > ngx_http_set_ctx(r, ctx, nginx_http_module);
> > > > }
> > > >
> > > > ngx_int_t rc = 0;
> > > > char custom_body[512];
> > > > ngx_uint_t blen;
> > > > ngx_uint_t custom_status;
> > > > if (!ctx->done) {
> > > > rc = http_module_process_request(r, &custom_status, custom_body,
> > > > &blen);
> > > > }
> > > >
> > > > ctx->done = 1;
> > > > if ((rc != 0) && (rc != NGX_DECLINED)) {
> > > > return http_mod_send_response(r, custom_status, custom_body, blen);
> > > > /* alternate implementation, send response in content handler.
> > > > ngx_buf_t *buf = ngx_create_temp_buf(r->pool, blen);
> > > > buf->last = ngx_copy(buf->start, (unsigned char*) data, dlen);
> > > > ctx->custom_body = buf;
> > > > ctx->rcode = custom_status;
> > > > */
> > > > }
> > > >
> > > > return NGX_DECLINED;
> > > > }
> > > >
> > > > static ngx_int_t
> > > > http_module_content_handler(ngx_http_request_t *r)
> > > > {
> > > > ngx_log_error(NGX_LOG_ERR, r->connection->log, 0, "%s: invoked",
> > > > __FUNCTION__);
> > > > ngx_http_ss_ctx_t *ctx = ngx_http_get_module_ctx(r,
> > > > nginx_mitigator_module);
> > > >
> > > > if (ctx && ctx->content) {
> > > > ctx->content = 0;
> > > > return http_mod_send_response(r, ctx->rcode, ctx->custom_body);
> > > > } else {
> > > > ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
> > > > "%s: ctx = %p, content = %d", __FUNCTION__, ctx, ctx
> > ?
> > > > ctx->content : -1);
> > > > }
> > > >
> > > > return NGX_DECLINED;
> > > > }
> > > >
> > > > static ngx_int_t
> > > > ngx_http_module_init (ngx_conf_t *cf)
> > > > {
> > > > ngx_http_core_main_conf_t *cmcf =
> > ngx_http_conf_get_module_main_conf(cf,
> > > > ngx_http_core_module);
> > > >
> > > > if (!cmcf) {
> > > > ngx_log_error(NGX_LOG_ERR, cf->log, 0, "Failed to retrieve module
> > main
> > > > conf");
> > > > return NGX_ERROR;
> > > > }
> > > >
> > > > ngx_http_handler_pt *hptr =
> > > > ngx_array_push(&cmcf->phases[NGX_HTTP_ACCESS_PHASE].handlers);
> > > > if (hptr == NULL) {
> > > > ngx_log_error(NGX_LOG_ERR, cf->log, 0, "Could not retrieve access
> > > > phase handler");
> > > > return NGX_ERROR;
> > > > }
> > > >
> > > > *hptr = ngx_http_request_handler;
> > > > ngx_log_error(NGX_LOG_INFO, cf->log, 0, "[init] Installed request
> > > > handler");
> > > >
> > > > ngx_http_handler_pt *cptr =
> > > > ngx_array_push(&cmcf->phases[NGX_HTTP_CONTENT_PHASE].handlers);
> > > > if (cptr == NULL) {
> > > > ngx_log_error(NGX_LOG_ERR, cf->log, 0, "Could not retrieve access
> > > > phase handler");
> > > > return NGX_ERROR;
> > > > }
> > > >
> > > > *cptr = ngx_http_request_handler;
> > > > ngx_log_error(NGX_LOG_INFO, cf->log, 0, "[init] Installed request
> > > > handler");
> > > >
> > > > return NGX_OK;
> > > > }
> > > >
> > > >
> > > >
> >
> > > _______________________________________________
> > > nginx-devel mailing list
> > > nginx-devel at nginx.org
> > > http://mailman.nginx.org/mailman/listinfo/nginx-devel
> >
> >
> > --
> > Roman Arutyunyan
> > _______________________________________________
> > nginx-devel mailing list
> > nginx-devel at nginx.org
> > http://mailman.nginx.org/mailman/listinfo/nginx-devel
> >
> _______________________________________________
> nginx-devel mailing list
> nginx-devel at nginx.org
> http://mailman.nginx.org/mailman/listinfo/nginx-devel
--
Roman Arutyunyan
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