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Gzip: use zlib to write header and trailer.

When nginx is used with zlib patched with [1], which provides
integration with the future IBM Z hardware deflate acceleration, it ends
up computing CRC32 twice: one time in hardware, which always does this,
and one time in software by explicitly calling crc32().

crc32() calls were added in changesets 133:b27548f540ad ("nginx-0.0.1-
2003-09-24-23:51:12 import") and 134:d57c6835225c ("nginx-0.0.1-
2003-09-26-09:45:21 import") as part of gzip wrapping feature - back
then zlib did not support it.

However, since then gzip wrapping was implemented in zlib v1.2.0.4,
and it's already being used by nginx for log compression.

This patch replaces hand-written gzip wrapping with the one provided by
zlib. It simplifies the code, and makes it avoid computing CRC32 twice
when using hardware acceleration.

[1] madler/zlib#410
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iii-i committed Jul 12, 2019
1 parent 29fea7d commit cfa1316368dcc6dc1aa82e3d0b67ec0d1cf7eebb
Showing with 7 additions and 117 deletions.
  1. +7 −117 src/http/modules/ngx_http_gzip_filter_module.c
@@ -55,44 +55,23 @@ typedef struct {
unsigned redo:1;
unsigned done:1;
unsigned nomem:1;
unsigned gzheader:1;
unsigned buffering:1;
unsigned intel:1;

size_t zin;
size_t zout;

uint32_t crc32;
z_stream zstream;
ngx_http_request_t *request;
} ngx_http_gzip_ctx_t;


#if (NGX_HAVE_LITTLE_ENDIAN && NGX_HAVE_NONALIGNED)

struct gztrailer {
uint32_t crc32;
uint32_t zlen;
};

#else /* NGX_HAVE_BIG_ENDIAN || !NGX_HAVE_NONALIGNED */

struct gztrailer {
u_char crc32[4];
u_char zlen[4];
};

#endif


static void ngx_http_gzip_filter_memory(ngx_http_request_t *r,
ngx_http_gzip_ctx_t *ctx);
static ngx_int_t ngx_http_gzip_filter_buffer(ngx_http_gzip_ctx_t *ctx,
ngx_chain_t *in);
static ngx_int_t ngx_http_gzip_filter_deflate_start(ngx_http_request_t *r,
ngx_http_gzip_ctx_t *ctx);
static ngx_int_t ngx_http_gzip_filter_gzheader(ngx_http_request_t *r,
ngx_http_gzip_ctx_t *ctx);
static ngx_int_t ngx_http_gzip_filter_add_data(ngx_http_request_t *r,
ngx_http_gzip_ctx_t *ctx);
static ngx_int_t ngx_http_gzip_filter_get_buf(ngx_http_request_t *r,
@@ -446,12 +425,6 @@ ngx_http_gzip_body_filter(ngx_http_request_t *r, ngx_chain_t *in)
return ctx->busy ? NGX_AGAIN : NGX_OK;
}

if (!ctx->gzheader) {
if (ngx_http_gzip_filter_gzheader(r, ctx) != NGX_OK) {
goto failed;
}
}

rc = ngx_http_next_body_filter(r, ctx->out);

if (rc == NGX_ERROR) {
@@ -643,7 +616,7 @@ ngx_http_gzip_filter_deflate_start(ngx_http_request_t *r,
ctx->zstream.opaque = ctx;

rc = deflateInit2(&ctx->zstream, (int) conf->level, Z_DEFLATED,
- ctx->wbits, ctx->memlevel, Z_DEFAULT_STRATEGY);
ctx->wbits + 16, ctx->memlevel, Z_DEFAULT_STRATEGY);

if (rc != Z_OK) {
ngx_log_error(NGX_LOG_ALERT, r->connection->log, 0,
@@ -652,45 +625,12 @@ ngx_http_gzip_filter_deflate_start(ngx_http_request_t *r,
}

ctx->last_out = &ctx->out;
ctx->crc32 = crc32(0L, Z_NULL, 0);
ctx->flush = Z_NO_FLUSH;

return NGX_OK;
}


static ngx_int_t
ngx_http_gzip_filter_gzheader(ngx_http_request_t *r, ngx_http_gzip_ctx_t *ctx)
{
ngx_buf_t *b;
ngx_chain_t *cl;
static u_char gzheader[10] =
{ 0x1f, 0x8b, Z_DEFLATED, 0, 0, 0, 0, 0, 0, 3 };

b = ngx_calloc_buf(r->pool);
if (b == NULL) {
return NGX_ERROR;
}

b->memory = 1;
b->pos = gzheader;
b->last = b->pos + 10;

cl = ngx_alloc_chain_link(r->pool);
if (cl == NULL) {
return NGX_ERROR;
}

cl->buf = b;
cl->next = ctx->out;
ctx->out = cl;

ctx->gzheader = 1;

return NGX_OK;
}


static ngx_int_t
ngx_http_gzip_filter_add_data(ngx_http_request_t *r, ngx_http_gzip_ctx_t *ctx)
{
@@ -743,14 +683,9 @@ ngx_http_gzip_filter_add_data(ngx_http_request_t *r, ngx_http_gzip_ctx_t *ctx)

} else if (ctx->in_buf->flush) {
ctx->flush = Z_SYNC_FLUSH;
}

if (ctx->zstream.avail_in) {

ctx->crc32 = crc32(ctx->crc32, ctx->zstream.next_in,
ctx->zstream.avail_in);

} else if (ctx->flush == Z_NO_FLUSH) {
} else if (ctx->zstream.avail_in == 0) {
/* ctx->flush == Z_NO_FLUSH */
return NGX_AGAIN;
}

@@ -932,13 +867,11 @@ static ngx_int_t
ngx_http_gzip_filter_deflate_end(ngx_http_request_t *r,
ngx_http_gzip_ctx_t *ctx)
{
int rc;
ngx_buf_t *b;
ngx_chain_t *cl;
struct gztrailer *trailer;
int rc;
ngx_chain_t *cl;

ctx->zin = ctx->zstream.total_in;
ctx->zout = 10 + ctx->zstream.total_out + 8;
ctx->zout = ctx->zstream.total_out;

rc = deflateEnd(&ctx->zstream);

@@ -960,50 +893,7 @@ ngx_http_gzip_filter_deflate_end(ngx_http_request_t *r,
*ctx->last_out = cl;
ctx->last_out = &cl->next;

if (ctx->zstream.avail_out >= 8) {
trailer = (struct gztrailer *) ctx->out_buf->last;
ctx->out_buf->last += 8;
ctx->out_buf->last_buf = 1;

} else {
b = ngx_create_temp_buf(r->pool, 8);
if (b == NULL) {
return NGX_ERROR;
}

b->last_buf = 1;

cl = ngx_alloc_chain_link(r->pool);
if (cl == NULL) {
return NGX_ERROR;
}

cl->buf = b;
cl->next = NULL;
*ctx->last_out = cl;
ctx->last_out = &cl->next;
trailer = (struct gztrailer *) b->pos;
b->last += 8;
}

#if (NGX_HAVE_LITTLE_ENDIAN && NGX_HAVE_NONALIGNED)

trailer->crc32 = ctx->crc32;
trailer->zlen = ctx->zin;

#else

trailer->crc32[0] = (u_char) (ctx->crc32 & 0xff);
trailer->crc32[1] = (u_char) ((ctx->crc32 >> 8) & 0xff);
trailer->crc32[2] = (u_char) ((ctx->crc32 >> 16) & 0xff);
trailer->crc32[3] = (u_char) ((ctx->crc32 >> 24) & 0xff);

trailer->zlen[0] = (u_char) (ctx->zin & 0xff);
trailer->zlen[1] = (u_char) ((ctx->zin >> 8) & 0xff);
trailer->zlen[2] = (u_char) ((ctx->zin >> 16) & 0xff);
trailer->zlen[3] = (u_char) ((ctx->zin >> 24) & 0xff);

#endif
ctx->out_buf->last_buf = 1;

ctx->zstream.avail_in = 0;
ctx->zstream.avail_out = 0;

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