haproxy/include/common/hpack-enc.h
Willy Tarreau eaeeb68f23 MINOR: hpack: provide a function to encode an HTTP path
The new function hpack_encode_path() supports encoding a path into
the ":path" header. It knows about "/" and "/index.html" which use
a single byte, and falls back to literal encoding for other ones,
with a fast path for short paths < 127 bytes.
2018-12-11 09:07:02 +01:00

263 lines
9.1 KiB
C

/*
* HPACK compressor (RFC7541)
*
* Copyright (C) 2014-2017 Willy Tarreau <willy@haproxy.org>
* Copyright (C) 2017 HAProxy Technologies
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
#ifndef _COMMON_HPACK_ENC_H
#define _COMMON_HPACK_ENC_H
#include <stdint.h>
#include <string.h>
#include <common/buf.h>
#include <common/config.h>
#include <common/http.h>
#include <common/ist.h>
int hpack_encode_header(struct buffer *out, const struct ist n,
const struct ist v);
/* Returns the number of bytes required to encode the string length <len>. The
* number of usable bits is an integral multiple of 7 plus 6 for the last byte.
* The maximum number of bytes returned is 4 (2097279 max length). Larger values
* return 0.
*/
static inline int hpack_len_to_bytes(size_t len)
{
ssize_t slen = len;
slen -= 127;
if (__builtin_expect(slen < 0, 1))
return 1;
if (slen < (1 << 14)) {
if (__builtin_expect(slen < (1 << 7), 1))
return 2;
else
return 3;
}
if (slen < (1 << 21))
return 4;
return 0;
}
/* Encodes <len> into <out>+<pos> and return the new position. The caller is
* responsible for checking for available room using hpack_len_to_bytes()
* first.
*/
static inline int hpack_encode_len(char *out, int pos, int len)
{
int code = len - 127;
if (code < 0) {
out[pos++] = len;
} else {
out[pos++] = 127;
for (; code >= 128; code >>= 7)
out[pos++] = code | 128;
out[pos++] = code;
}
return pos;
}
/* Tries to encode header field index <idx> with short value <val> into the
* aligned buffer <out>. Returns non-zero on success, 0 on failure (buffer
* full). The caller is responsible for ensuring that the length of <val> is
* strictly lower than 127, and that <idx> is lower than 64 (static list only),
* and that the buffer is aligned (head==0).
*/
static inline int hpack_encode_short_idx(struct buffer *out, int idx, struct ist val)
{
if (out->data + 2 + val.len > out->size)
return 0;
/* literal header field with incremental indexing */
out->area[out->data++] = idx | 0x40;
out->area[out->data++] = val.len;
ist2bin(&out->area[out->data], val);
out->data += val.len;
return 1;
}
/* Tries to encode header field index <idx> with long value <val> into the
* aligned buffer <out>. Returns non-zero on success, 0 on failure (buffer
* full). The caller is responsible for ensuring <idx> is lower than 64 (static
* list only), and that the buffer is aligned (head==0).
*/
static inline int hpack_encode_long_idx(struct buffer *out, int idx, struct ist val)
{
int len = out->data;
if (!hpack_len_to_bytes(val.len) ||
1 + len + hpack_len_to_bytes(val.len) + val.len > out->size)
return 0;
/* emit literal with indexing (7541#6.2.1) :
* [ 0 | 1 | Index (6+) ]
*/
out->area[len++] = idx | 0x40;
len = hpack_encode_len(out->area, len, val.len);
memcpy(out->area + len, val.ptr, val.len);
len += val.len;
out->data = len;
return 1;
}
/* Tries to encode a :status pseudo-header with the integer status <status>
* into the aligned buffer <out>. Returns non-zero on success, 0 on failure
* (buffer full). The caller is responsible for ensuring that the status is
* comprised between 100 and 999 inclusive and that the buffer is aligned. It's
* inlined because it's easily optimizable by the compiler.
*/
static inline int hpack_encode_int_status(struct buffer *out, unsigned int status)
{
int len = out->data;
int size = out->size;
unsigned char c = 0;
/* try to emit a single byte code */
len++;
if (__builtin_expect(len > size, 0))
goto fail;
c = (status <= 304) ?
(status <= 204) ?
(status == 204) ? 0x89 :
(status == 200) ? 0x88 :
0: /* > 204 */
(status == 304) ? 0x8b :
(status == 206) ? 0x8a :
0:
(status <= 404) ?
(status == 404) ? 0x8d :
(status == 400) ? 0x8c :
0: /* > 404 */
(status == 500) ? 0x8e :
0;
if (c)
goto last;
/* fall back to literal */
len += 4;
if (__builtin_expect(len > size, 0))
goto fail;
/* basic encoding of the status code */
out->area[len - 5] = 0x48; // indexed name -- name=":status" (idx 8)
out->area[len - 4] = 0x03; // 3 bytes status
out->area[len - 3] = '0' + status / 100;
out->area[len - 2] = '0' + status / 10 % 10;
c = '0' + status % 10;
last:
out->area[len - 1] = c;
out->data = len;
return 1;
fail:
return 0;
}
/* Tries to encode a :status pseudo-header with the integer status <status>
* also represented by <str> into the aligned buffer <out>. Returns non-zero
* on success or 0 on failure (buffer full). The caller is responsible for
* ensuring that the status is comprised between 100 and 999 inclusive, that
* <str> contains a valid representation of the numerical value, and that the
* buffer is aligned. This version is preferred when the caller already knows
* a string representation of the status because it avoids the computation in
* the uncompressed case. It's inlined because it's easily optimizable.
*/
static inline int hpack_encode_str_status(struct buffer *out, unsigned int status, struct ist str)
{
/* don't try too hard, we already have the ASCII value for less common cases */
if (status == 200 || status == 304) {
if (out->data >= out->size)
return 0;
out->area[out->data] = (status == 304) ? 0x8b : 0x88;
out->data++;
return 1;
}
return hpack_encode_short_idx(out, 8, str); // name=":status" (idx 8)
}
/* Tries to encode a :method pseudo-header with the method in <meth>, which
* also exists as a string in <str>, into the aligned buffer <out>. Returns
* non-zero on success or 0 on failure (buffer full). The caller is responsible
* for ensuring that the string matches <meth>, that it's smaller than 127
* bytes, and that the buffer is aligned. If <meth> is unknown then using
* HTTP_METH_OTHER will lead to the string being encoded as a literal. It's
* inlined because it's easily optimizable.
*/
static inline int hpack_encode_method(struct buffer *out, enum http_meth_t meth, struct ist str)
{
if (out->data < out->size && meth == HTTP_METH_GET)
out->area[out->data++] = 0x82; // indexed field : idx[02]=(":method", "GET")
else if (out->data < out->size && meth == HTTP_METH_POST)
out->area[out->data++] = 0x83; // indexed field : idx[03]=(":method", "POST")
else
return hpack_encode_short_idx(out, 2, str); // name=":method" (idx 2)
return 1;
}
/* Tries to encode a :scheme pseudo-header with the scheme in <scheme>, into
* the aligned buffer <out>. Returns non-zero on success or 0 on failure
* (buffer full). Only "http" and "https" are recognized and handled as indexed
* values, others are turned into short literals. The caller is responsible for
* ensuring that the scheme is smaller than 127 bytes, and that the buffer is
* aligned. Normally the compiler will detect constant strings in the comparison
* if the code remains inlined.
*/
static inline int hpack_encode_scheme(struct buffer *out, struct ist scheme)
{
if (out->data < out->size && isteq(scheme, ist("https")))
out->area[out->data++] = 0x87; // indexed field : idx[07]=(":scheme", "https")
else if (out->data < out->size && isteq(scheme, ist("http")))
out->area[out->data++] = 0x86; // indexed field : idx[06]=(":scheme", "http")
else
return hpack_encode_short_idx(out, 6, scheme); // name=":scheme" (idx 6)
return 1;
}
/* Tries to encode a :path pseudo-header with the path in <path>, into the
* aligned buffer <out>. Returns non-zero on success or 0 on failure (buffer
* full). The well-known values "/" and "/index.html" are recognized, and other
* ones are handled as literals. The caller is responsible for ensuring that
* the buffer is aligned. Normally the compiler will detect constant strings
* in the comparison if the code remains inlined.
*/
static inline int hpack_encode_path(struct buffer *out, struct ist path)
{
if (out->data < out->size && isteq(path, ist("/")))
out->area[out->data++] = 0x84; // indexed field : idx[04]=(":path", "/")
else if (out->data < out->size && isteq(path, ist("/index.html")))
out->area[out->data++] = 0x85; // indexed field : idx[05]=(":path", "/index.html")
else if (path.len < 127)
return hpack_encode_short_idx(out, 4, path); // name=":path" (idx 4)
else
return hpack_encode_long_idx(out, 4, path); // name=":path" (idx 4)
return 1;
}
#endif /* _COMMON_HPACK_ENC_H */