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Gzip: use zlib to write header and trailer.
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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 @sw0x2A
iii-i authored and sw0x2A committed Aug 29, 2019
1 parent 3e072f4 commit 9c852f4
Showing 1 changed file with 7 additions and 117 deletions.
124 changes: 7 additions & 117 deletions src/http/modules/ngx_http_gzip_filter_module.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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,
Expand Down Expand Up @@ -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) {
Expand Down Expand Up @@ -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,
Expand All @@ -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)
{
Expand Down Expand Up @@ -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;
}

Expand Down Expand Up @@ -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);

Expand All @@ -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;
Expand Down

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