ok,

I've created patch which must feet nginx rules and my needs, please find it below.
when I've checked sources of zlib.h I found this "windowBits can also be greater than 15 for optional zip decoding. Add 32 to windowBits to enable zlib and gzip decoding with automatic header detection, or add 16 to decode only the gzip format (the zlib format will return a Z_DATA_ERROR)."
As I can understand if pass here +16 it will work only with gzip, +32 will take both.

We have huge traffic, and throw this module goes a lot of sites which don't checking RFC browser supports both of it, I'm just counting alerts in error log and with +32 this amount much smaller.

Regarding yandex stuff, I don't know why they made it this way, but they sending 3 chunks: 1st is 16 bytes weird gzip header and nothing more, next chunk correct html content, and 3rd one is zero size.

Idiotic, but browser can handle it. May we work this way, try to gunzip if we got error try to gunzip next chunk, or if we have fatal error just pass whole stream unchanged, at least on first chunk?

My patch follows:
--- /root/work/ngx_http_gunzip_filter_module-0.3/ngx_http_gunzip_filter_module.c 2010-03-22 11:11:16.000000000 -0700
+++ ngx_http_gunzip_filter_module.c 2010-04-20 15:59:01.000000000 -0700
@@ -16,6 +16,9 @@
typedef struct {
ngx_flag_t enable;
ngx_bufs_t bufs;
+ ngx_uint_t pass;
+ ngx_hash_t types;
+ ngx_array_t *types_keys;
} ngx_http_gunzip_conf_t;


@@ -40,6 +43,17 @@
ngx_http_request_t *request;
} ngx_http_gunzip_ctx_t;

+#define NGX_HTTP_GUNZIP_PASS_ANY 0x02
+#define NGX_HTTP_GUNZIP_PASS_CONTENT_TYPE 0x04
+#define NGX_HTTP_GUNZIP_PASS_200 0x08
+
+static ngx_conf_bitmask_t ngx_http_gzip_pass_mask[] = {
+ { ngx_string("any"), NGX_HTTP_GUNZIP_PASS_ANY },
+ { ngx_string("content_type"), NGX_HTTP_GUNZIP_PASS_CONTENT_TYPE },
+ { ngx_string("200"), NGX_HTTP_GUNZIP_PASS_200 },
+ { ngx_null_string, 0 }
+};
+

static ngx_int_t ngx_http_gunzip_filter_inflate_start(ngx_http_request_t *r,
ngx_http_gunzip_ctx_t *ctx);
@@ -78,6 +92,20 @@
offsetof(ngx_http_gunzip_conf_t, bufs),
NULL },

+ { ngx_string("gunzip_pass"),
+ NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_1MORE,
+ ngx_conf_set_bitmask_slot,
+ NGX_HTTP_LOC_CONF_OFFSET,
+ offsetof(ngx_http_gunzip_conf_t, pass),
+ &ngx_http_gzip_pass_mask },
+
+ { ngx_string("gunzip_filter_types"),
+ NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_1MORE,
+ ngx_http_types_slot,
+ NGX_HTTP_LOC_CONF_OFFSET,
+ offsetof(ngx_http_gunzip_conf_t, types_keys),
+ &ngx_http_html_default_types[0] },
+
ngx_null_command
};

@@ -130,6 +158,10 @@
/* TODO ignore content encoding? */

if (!conf->enable
+ || ((conf->pass & NGX_HTTP_GUNZIP_PASS_200 ) && (r->upstream)
+ && (r->upstream->state) && (r->upstream->state->status != 200))
+ || ((conf->pass & NGX_HTTP_GUNZIP_PASS_CONTENT_TYPE)
+ && ngx_http_test_content_type(r, &conf->types) == NULL)
|| r->headers_out.content_encoding == NULL
|| r->headers_out.content_encoding->value.len != 4
|| ngx_strncasecmp(r->headers_out.content_encoding->value.data,
@@ -138,26 +170,29 @@
return ngx_http_next_header_filter(r);
}

+ if (! conf->pass & NGX_HTTP_GUNZIP_PASS_ANY )
+ {
#if (nginx_version >= 8025 || (nginx_version >= 7065 && nginx_version < 8000))

- r->gzip_vary = 1;
-
- if (!r->gzip_tested) {
- if (ngx_http_gzip_ok(r) == NGX_OK) {
- return ngx_http_next_header_filter(r);
- }
+ r->gzip_vary = 1;

- } else if (!r->gzip_ok) {
- return ngx_http_next_header_filter(r);
- }
+ if (!r->gzip_tested) {
+ if (ngx_http_gzip_ok(r) == NGX_OK) {
+ return ngx_http_next_header_filter(r);
+ }
+
+ } else if (!r->gzip_ok) {
+ return ngx_http_next_header_filter(r);
+ }

#else

- if (ngx_http_gzip_ok(r) == NGX_OK) {
- return ngx_http_next_header_filter(r);
- }
+ if (ngx_http_gzip_ok(r) == NGX_OK) {
+ return ngx_http_next_header_filter(r);
+ }

#endif
+ }

ctx = ngx_pcalloc(r->pool, sizeof(ngx_http_gunzip_ctx_t));
if (ctx == NULL) {
@@ -314,8 +349,8 @@
ctx->zstream.zfree = ngx_http_gunzip_filter_free;
ctx->zstream.opaque = ctx;

- /* windowBits +16 to decode gzip, zlib 1.2.0.4+ */
- rc = inflateInit2(&ctx->zstream, MAX_WBITS + 16);
+ /* windowBits +32 to decode gzip and zlib, zlib 1.2.0.4+ */
+ rc = inflateInit2(&ctx->zstream, MAX_WBITS + 32);

if (rc != Z_OK) {
ngx_log_error(NGX_LOG_ALERT, r->connection->log, 0,
@@ -669,6 +704,24 @@
ngx_conf_merge_bufs_value(conf->bufs, prev->bufs,
(128 * 1024) / ngx_pagesize, ngx_pagesize);

+ ngx_conf_merge_bitmask_value(conf->pass, prev->pass,
+ NGX_CONF_BITMASK_SET);
+
+#if (nginx_version < 8000)
+ if (ngx_http_merge_types(cf, conf->types_keys, &conf->types,
+ prev->types_keys, &prev->types,
+ ngx_http_html_default_types)
+ != NGX_OK)
+#else
+ if (ngx_http_merge_types(cf, &conf->types_keys, &conf->types,
+ &prev->types_keys, &prev->types,
+ ngx_http_html_default_types)
+ != NGX_OK)
+#endif
+ {
+ return NGX_CONF_ERROR;
+ }
+
return NGX_CONF_OK;
}