# HG changeset patch
# User Maxim Dounin <mdounin@mdounin.ru>
# Date 1309184986 -14400
# Node ID 3d27d8f8ccb38fb59bb9b5a613dc0c1c8a01a507
# Parent f17d4d2f60c125d977233e9c4998459499006c32
Gzip filter: handle empty flush buffers.

Empty flush buffers are legitimate and may happen e.g. due to $r->flush()
calls in embedded perl. If there are no data buffered in zlib deflate()
will return Z_BUF_ERROR (i.e. no progress possible) without adding anything
to output. Don't treat Z_BUF_ERROR as fatal and correctly send empty flush
buffer if we have no data in output at all.

See this thread for details:

http://nginx.org/pipermail/nginx/2010-November/023693.html

diff --git a/src/http/modules/ngx_http_gzip_filter_module.c b/src/http/modules/ngx_http_gzip_filter_module.c
--- a/src/http/modules/ngx_http_gzip_filter_module.c
+++ b/src/http/modules/ngx_http_gzip_filter_module.c
@@ -758,6 +758,7 @@ static ngx_int_t
ngx_http_gzip_filter_deflate(ngx_http_request_t *r, ngx_http_gzip_ctx_t *ctx)
{
int rc;
+ ngx_buf_t *b;
ngx_chain_t *cl;
ngx_http_gzip_conf_t *conf;

@@ -769,7 +770,7 @@ ngx_http_gzip_filter_deflate(ngx_http_re

rc = deflate(&ctx->zstream, ctx->flush);

- if (rc != Z_OK && rc != Z_STREAM_END) {
+ if (rc != Z_OK && rc != Z_STREAM_END && rc != Z_BUF_ERROR) {
ngx_log_error(NGX_LOG_ALERT, r->connection->log, 0,
"deflate() failed: %d, %d", ctx->flush, rc);
return NGX_ERROR;
@@ -818,8 +819,6 @@ ngx_http_gzip_filter_deflate(ngx_http_re

if (ctx->flush == Z_SYNC_FLUSH) {

- ctx->zstream.avail_out = 0;
- ctx->out_buf->flush = 1;
ctx->flush = Z_NO_FLUSH;

cl = ngx_alloc_chain_link(r->pool);
@@ -827,7 +826,22 @@ ngx_http_gzip_filter_deflate(ngx_http_re
return NGX_ERROR;
}

- cl->buf = ctx->out_buf;
+ b = ctx->out_buf;
+
+ if (ngx_buf_size(b) == 0) {
+
+ b = ngx_calloc_buf(ctx->request->pool);
+ if (b == NULL) {
+ return NGX_ERROR;
+ }
+
+ } else {
+ ctx->zstream.avail_out = 0;
+ }
+
+ b->flush = 1;
+
+ cl->buf = b;
cl->next = NULL;
*ctx->last_out = cl;
ctx->last_out = &cl->next;

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