commit 0418357ffd575ff4a3ec95937f596776c3b9ecec Author: Nick Mathewson nickm@torproject.org Date: Fri Apr 28 14:36:24 2017 -0400
Serve consensus diffs on request. --- src/or/directory.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 94 insertions(+), 3 deletions(-)
diff --git a/src/or/directory.c b/src/or/directory.c index 4d03c12..cf272f7 100644 --- a/src/or/directory.c +++ b/src/or/directory.c @@ -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 << 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,