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Serve consensus diffs on request.

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This commit is contained in:
Nick Mathewson 2017-04-28 14:36:24 -04:00
parent e5f82969ca
commit 0418357ffd
1 changed files with 94 additions and 3 deletions
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97
src/or/directory.c
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@ -13,6 +13,7 @@
#include "config.h"
#include "connection.h"
#include "connection_edge.h"
#include "consdiffmgr.h"
#include "control.h"
#include "compat.h"
#define DIRECTORY_PRIVATE
@ -3180,6 +3181,16 @@ write_http_response_header(dir_connection_t *conn, ssize_t length,
cache_lifetime);
}
/** Array of compression methods to use (if supported) for serving
* precompressed data, ordered from best to worst. */
static compress_method_t srv_meth_pref_precompressed[] = {
LZMA_METHOD,
ZSTD_METHOD,
ZLIB_METHOD,
GZIP_METHOD,
NO_METHOD
};
/** Parse the compression methods listed in an Accept-Encoding header <b>h</b>,
* and convert them to a bitfield where compression method x is supported if
* and only if 1 &lt;&lt; x is set in the bitfield. */
@ -3483,6 +3494,69 @@ warn_consensus_is_too_old(networkstatus_t *v, const char *flavor, time_t now)
}
}
/** If there is an X-Or-Diff-From-Consensus header included in <b>headers</b>,
* set <b>digest_out<b> to a new smartlist containing every 256-bit
* hex-encoded digest listed in that header and return 0. Otherwise return
* -1. */
static int
parse_or_diff_from_header(smartlist_t **digests_out, const char *headers)
{
char *hdr = http_get_header(headers, "X-Or-Diff-From-Consensus");
if (hdr == NULL) {
return -1;
}
smartlist_t *hex_digests = smartlist_new();
*digests_out = smartlist_new();
smartlist_split_string(hex_digests, hdr, " ",
SPLIT_SKIP_SPACE|SPLIT_IGNORE_BLANK, -1);
SMARTLIST_FOREACH_BEGIN(hex_digests, const char *, hex) {
uint8_t digest[DIGEST256_LEN];
if (base16_decode((char*)digest, sizeof(digest), hex, strlen(hex)) ==
DIGEST256_LEN) {
smartlist_add(*digests_out, tor_memdup(digest, sizeof(digest)));
} else {
log_fn(LOG_PROTOCOL_WARN, LD_DIR,
"X-Or-Diff-From-Consensus header contained bogus digest %s; "
"ignoring.", escaped(hex));
}
} SMARTLIST_FOREACH_END(hex);
SMARTLIST_FOREACH(hex_digests, char *, cp, tor_free(cp));
smartlist_free(hex_digests);
return 0;
}
/**
* Try to find the best consensus diff possible in order to serve a client
* request for a diff from one of the consensuses in <b>digests</b> to the
* current consensus of flavor <b>flav</b>. The client supports the
* compression methods listed in the <b>compression_methods</b> bitfield:
* place the method chosen (if any) into <b>compression_used_out</b>.
*/
static struct consensus_cache_entry_t *
find_best_diff(const smartlist_t *digests, int flav,
unsigned compression_methods,
compress_method_t *compression_used_out)
{
struct consensus_cache_entry_t *result = NULL;
SMARTLIST_FOREACH_BEGIN(digests, const uint8_t *, diff_from) {
unsigned u;
for (u = 0; u < ARRAY_LENGTH(srv_meth_pref_precompressed); ++u) {
compress_method_t method = srv_meth_pref_precompressed[u];
if (0 == (compression_methods & (1u<<method)))
continue; // client doesn't like this one, or we don't have it.
if (consdiffmgr_find_diff_from(&result, flav, DIGEST_SHA3_256,
diff_from, DIGEST256_LEN,
method) == CONSDIFF_AVAILABLE) {
tor_assert_nonfatal(result);
*compression_used_out = method;
return result;
}
}
} SMARTLIST_FOREACH_END(diff_from);
return NULL;
}
/** Helper function for GET /tor/status-vote/current/consensus
*/
static int
@ -3542,16 +3616,33 @@ handle_get_current_consensus(dir_connection_t *conn,
goto done;
}
struct consensus_cache_entry_t *cached_diff = NULL;
smartlist_t *diff_from_digests = NULL;
compress_method_t compression_used = NO_METHOD;
if (!parse_or_diff_from_header(&diff_from_digests, args->headers)) {
tor_assert(diff_from_digests);
cached_diff = find_best_diff(diff_from_digests, flav,
args->compression_supported,
&compression_used);
SMARTLIST_FOREACH(diff_from_digests, uint8_t *, d, tor_free(d));
smartlist_free(diff_from_digests);
}
conn->spool = smartlist_new();
clear_spool = 1;
{
spooled_resource_t *spooled;
if (flavor)
if (cached_diff) {
spooled = spooled_resource_new_from_cache_entry(cached_diff);
} else if (flavor) {
spooled = spooled_resource_new(DIR_SPOOL_NETWORKSTATUS,
(uint8_t*)flavor, strlen(flavor));
else
compression_used = compressed ? ZLIB_METHOD : NO_METHOD;
} else {
spooled = spooled_resource_new(DIR_SPOOL_NETWORKSTATUS,
NULL, 0);
compression_used = compressed ? ZLIB_METHOD : NO_METHOD;
}
tor_free(flavor);
smartlist_add(conn->spool, spooled);
}
@ -3606,7 +3697,7 @@ handle_get_current_consensus(dir_connection_t *conn,
clear_spool = 0;
write_http_response_header(conn, -1,
compressed ? ZLIB_METHOD : NO_METHOD,
compression_used,
smartlist_len(conn->spool) == 1 ? lifetime : 0);
if (! compressed)
conn->compress_state = tor_compress_new(0, ZLIB_METHOD,