[tor-commits] [tor/master] Comment the heck out of the stream/circuit attaching process.

commit f3e158edf7d8128d4f1e028c5604e70469730947 Author: Nick Mathewson nickm@torproject.org Date: Thu Oct 27 12:03:52 2016 -0400

Comment the heck out of the stream/circuit attaching process. --- src/or/addressmap.c | 18 ++++++-- src/or/circuituse.c | 100 +++++++++++++++++++++++++++++++++---------- src/or/connection_edge.c | 109 +++++++++++++++++++++++++++++++++-------------- 3 files changed, 168 insertions(+), 59 deletions(-)

diff --git a/src/or/addressmap.c b/src/or/addressmap.c index 33fd7e0..85a6434 100644 --- a/src/or/addressmap.c +++ b/src/or/addressmap.c @@ -376,29 +376,38 @@ addressmap_rewrite(char *address, size_t maxlen, char *addr_orig = tor_strdup(address); char *log_addr_orig = NULL;

+ /* We use a loop here to limit the total number of rewrites we do, + * so that we can't hit an infinite loop. */ for (rewrites = 0; rewrites < 16; rewrites++) { int exact_match = 0; log_addr_orig = tor_strdup(escaped_safe_str_client(address));

+ /* First check to see if there's an exact match for this address */ ent = strmap_get(addressmap, address);

if (!ent || !ent->new_address) { + /* And if we don't have an exact match, try to check whether + * we have a pattern-based match. + */ ent = addressmap_match_superdomains(address); } else { if (ent->src_wildcard && !ent->dst_wildcard && !strcasecmp(address, ent->new_address)) { - /* This is a rule like *.example.com example.com, and we just got - * "example.com" */ + /* This is a rule like "rewrite *.example.com to example.com", and we + * just got "example.com". Instead of calling it an infinite loop, + * call it complete. */ goto done; } - exact_match = 1; }

if (!ent || !ent->new_address) { + /* We still have no match at all. We're done! */ goto done; }

+ /* Check wither the flags we were passed tell us not to use this + * mapping. */ switch (ent->source) { case ADDRMAPSRC_DNS: { @@ -431,6 +440,8 @@ addressmap_rewrite(char *address, size_t maxlen, goto done; }

+ /* Now fill in the address with the new address. That might be via + * appending some new stuff to the end, or via just replacing it. */ if (ent->dst_wildcard && !exact_match) { strlcat(address, ".", maxlen); strlcat(address, ent->new_address, maxlen); @@ -438,6 +449,7 @@ addressmap_rewrite(char *address, size_t maxlen, strlcpy(address, ent->new_address, maxlen); }

+ /* Is this now a .exit address? If so, remember where we got it.*/ if (!strcmpend(address, ".exit") && strcmpend(addr_orig, ".exit") && exit_source == ADDRMAPSRC_NONE) { diff --git a/src/or/circuituse.c b/src/or/circuituse.c index 166971c..11d7820 100644 --- a/src/or/circuituse.c +++ b/src/or/circuituse.c @@ -14,7 +14,7 @@ * module keeps track of which streams can be attached to which circuits (in * circuit_get_best()), and attaches streams to circuits (with * circuit_try_attaching_streams(), connection_ap_handshake_attach_circuit(), - * and connection_ap_handshake_attach_chosen_circuit(). + * and connection_ap_handshake_attach_chosen_circuit() ). * * This module also makes sure that we are building circuits for all of the * predicted ports, using circuit_remove_handled_ports(), @@ -1876,16 +1876,22 @@ circuit_get_open_circ_or_launch(entry_connection_t *conn, c->state, conn_state_to_string(c->type, c->state)); } tor_assert(ENTRY_TO_CONN(conn)->state == AP_CONN_STATE_CIRCUIT_WAIT); + + /* Will the exit policy of the exit node apply to this stream? */ check_exit_policy = conn->socks_request->command == SOCKS_COMMAND_CONNECT && !conn->use_begindir && !connection_edge_is_rendezvous_stream(ENTRY_TO_EDGE_CONN(conn)); + + /* Does this connection want a one-hop circuit? */ want_onehop = conn->want_onehop;

+ /* Do we need a high-uptime circuit? */ need_uptime = !conn->want_onehop && !conn->use_begindir && smartlist_contains_int_as_string(options->LongLivedPorts, conn->socks_request->port);

+ /* Do we need an "internal" circuit? */ if (desired_circuit_purpose != CIRCUIT_PURPOSE_C_GENERAL) need_internal = 1; else if (conn->use_begindir || conn->want_onehop) @@ -1893,21 +1899,31 @@ circuit_get_open_circ_or_launch(entry_connection_t *conn, else need_internal = 0;

- circ = circuit_get_best(conn, 1, desired_circuit_purpose, + /* We now know what kind of circuit we need. See if there is an + * open circuit that we can use for this stream */ + circ = circuit_get_best(conn, 1 /* Insist on open circuits */, + desired_circuit_purpose, need_uptime, need_internal);

if (circ) { + /* We got a circuit that will work for this stream! We can return it. */ *circp = circ; return 1; /* we're happy */ }

+ /* Okay, there's no circuit open that will work for this stream. Let's + * see if there's an in-progress circuit or if we have to launch one */ + + /* Do we know enough directory info to build circuits at all? */ int have_path = have_enough_path_info(!need_internal);

if (!want_onehop && (!router_have_minimum_dir_info() || !have_path)) { + /* If we don't have enough directory information, we can't build + * multihop circuits. + */ if (!connection_get_by_type(CONN_TYPE_DIR)) { int severity = LOG_NOTICE; - /* FFFF if this is a tunneled directory fetch, don't yell - * as loudly. the user doesn't even know it's happening. */ + /* Retry some stuff that might help the connection work. */ if (entry_list_is_constrained(options) && entries_known_but_down(options)) { log_fn(severity, LD_APP|LD_DIR, @@ -1928,14 +1944,16 @@ circuit_get_open_circ_or_launch(entry_connection_t *conn, routerlist_retry_directory_downloads(time(NULL)); } } - /* the stream will be dealt with when router_have_minimum_dir_info becomes - * 1, or when all directory attempts fail and directory_all_unreachable() + /* Since we didn't have enough directory info, we can't attach now. The + * stream will be dealt with when router_have_minimum_dir_info becomes 1, + * or when all directory attempts fail and directory_all_unreachable() * kills it. */ return 0; }

- /* Do we need to check exit policy? */ + /* Check whether the exit policy of the chosen exit, or the exit policies + * of _all_ nodes, would forbid this node. */ if (check_exit_policy) { if (!conn->chosen_exit_name) { struct in_addr in; @@ -1976,16 +1994,25 @@ circuit_get_open_circ_or_launch(entry_connection_t *conn, } }

- /* is one already on the way? */ - circ = circuit_get_best(conn, 0, desired_circuit_purpose, + /* Now, check whether there already a circuit on the way that could handle + * this stream. This check matches the one above, but this time we + * do not require that the circuit will work. */ + circ = circuit_get_best(conn, 0 /* don't insist on open circuits */, + desired_circuit_purpose, need_uptime, need_internal); if (circ) log_debug(LD_CIRC, "one on the way!"); + if (!circ) { + /* No open or in-progress circuit could handle this stream! We + * will have to launch one! + */ + + /* THe chosen exit node, if there is one. */ extend_info_t *extend_info=NULL; - uint8_t new_circ_purpose; const int n_pending = count_pending_general_client_circuits();

+ /* Do we have too many pending circuits? */ if (n_pending >= options->MaxClientCircuitsPending) { static ratelim_t delay_limit = RATELIM_INIT(10*60); char *m; @@ -1999,6 +2026,8 @@ circuit_get_open_circ_or_launch(entry_connection_t *conn, return 0; }

+ /* If this is a hidden service trying to start an introduction point, + * handle that case. */ if (desired_circuit_purpose == CIRCUIT_PURPOSE_C_INTRODUCE_ACK_WAIT) { /* need to pick an intro point */ rend_data_t *rend_data = ENTRY_TO_EDGE_CONN(conn)->rend_data; @@ -2036,7 +2065,7 @@ circuit_get_open_circ_or_launch(entry_connection_t *conn, "Discarding this circuit.", conn->chosen_exit_name); return -1; } - } else { + } else { /* ! (r && node_has_descriptor(r)) */ log_debug(LD_DIR, "considering %d, %s", want_onehop, conn->chosen_exit_name); if (want_onehop && conn->chosen_exit_name[0] == '$') { @@ -2059,7 +2088,7 @@ circuit_get_open_circ_or_launch(entry_connection_t *conn, extend_info = extend_info_new(conn->chosen_exit_name+1, digest, NULL, NULL, &addr, conn->socks_request->port); - } else { + } else { /* ! (want_onehop && conn->chosen_exit_name[0] == '$') */ /* We will need an onion key for the router, and we * don't have one. Refuse or relax requirements. */ log_fn(opt ? LOG_INFO : LOG_WARN, LD_APP, @@ -2077,8 +2106,10 @@ circuit_get_open_circ_or_launch(entry_connection_t *conn, } } } - } + } /* Done checking for general circutis with chosen exits. */

+ /* What purpose do we need to launch this circuit with? */ + uint8_t new_circ_purpose; if (desired_circuit_purpose == CIRCUIT_PURPOSE_C_REND_JOINED) new_circ_purpose = CIRCUIT_PURPOSE_C_ESTABLISH_REND; else if (desired_circuit_purpose == CIRCUIT_PURPOSE_C_INTRODUCE_ACK_WAIT) @@ -2087,6 +2118,8 @@ circuit_get_open_circ_or_launch(entry_connection_t *conn, new_circ_purpose = desired_circuit_purpose;

#ifdef ENABLE_TOR2WEB_MODE + /* If tor2Web is on, then hidden service requests should be one-hop. + */ if (options->Tor2webMode && (new_circ_purpose == CIRCUIT_PURPOSE_C_ESTABLISH_REND || new_circ_purpose == CIRCUIT_PURPOSE_C_INTRODUCING)) { @@ -2094,6 +2127,7 @@ circuit_get_open_circ_or_launch(entry_connection_t *conn, } #endif

+ /* Determine what kind of a circuit to launch, and actually launch it. */ { int flags = CIRCLAUNCH_NEED_CAPACITY; if (want_onehop) flags |= CIRCLAUNCH_ONEHOP_TUNNEL; @@ -2105,6 +2139,8 @@ circuit_get_open_circ_or_launch(entry_connection_t *conn,

extend_info_free(extend_info);

+ /* Now trigger things that need to happen when we launch circuits */ + if (desired_circuit_purpose == CIRCUIT_PURPOSE_C_GENERAL) { /* We just caused a circuit to get built because of this stream. * If this stream has caused a _lot_ of circuits to be built, that's @@ -2128,6 +2164,10 @@ circuit_get_open_circ_or_launch(entry_connection_t *conn, } } } /* endif (!circ) */ + + /* We either found a good circuit, or launched a new circuit, or failed to + * do so. Report success, and delay. */ + if (circ) { /* Mark the circuit with the isolation fields for this connection. * When the circuit arrives, we'll clear these flags: this is @@ -2327,7 +2367,9 @@ connection_ap_handshake_attach_chosen_circuit(entry_connection_t *conn,

pathbias_count_use_attempt(circ);

+ /* Now, actually link the connection. */ link_apconn_to_circ(conn, circ, cpath); + tor_assert(conn->socks_request); if (conn->socks_request->command == SOCKS_COMMAND_CONNECT) { if (!conn->use_begindir) @@ -2342,12 +2384,11 @@ connection_ap_handshake_attach_chosen_circuit(entry_connection_t *conn, return 1; }

-/** Try to find a safe live circuit for CONN_TYPE_AP connection conn. If - * we don't find one: if conn cannot be handled by any known nodes, - * warn and return -1 (conn needs to die, and is maybe already marked); - * else launch new circuit (if necessary) and return 0. - * Otherwise, associate conn with a safe live circuit, do the - * right next step, and return 1. +/** Try to find a safe live circuit for stream <b>conn</b>. If we find one, + * attach the stream, send appropriate cells, and return 1. Otherwise, + * try to launch new circuit(s) for the stream. If we can launch + * circuits, return 0. Otherwise, if we simply can't proceed with + * this stream, return -1. (conn needs to die, and is maybe already marked). */ /* XXXX this function should mark for close whenever it returns -1; * its callers shouldn't have to worry about that. */ @@ -2366,6 +2407,7 @@ connection_ap_handshake_attach_circuit(entry_connection_t *conn)

conn_age = (int)(time(NULL) - base_conn->timestamp_created);

+ /* Is this connection so old that we should give up on it? */ if (conn_age >= get_options()->SocksTimeout) { int severity = (tor_addr_is_null(&base_conn->addr) && !base_conn->port) ? LOG_INFO : LOG_NOTICE; @@ -2376,12 +2418,14 @@ connection_ap_handshake_attach_circuit(entry_connection_t *conn) return -1; }

+ /* We handle "general" (non-onion) connections much more straightforwardly. + */ if (!connection_edge_is_rendezvous_stream(ENTRY_TO_EDGE_CONN(conn))) { /* we're a general conn */ origin_circuit_t *circ=NULL;

/* Are we linked to a dir conn that aims to fetch a consensus? - * We check here because this conn might no longer be needed. */ + * We check here because the conn might no longer be needed. */ if (base_conn->linked_conn && base_conn->linked_conn->type == CONN_TYPE_DIR && base_conn->linked_conn->purpose == DIR_PURPOSE_FETCH_CONSENSUS) { @@ -2399,6 +2443,9 @@ connection_ap_handshake_attach_circuit(entry_connection_t *conn) } }

+ /* If we have a chosen exit, we need to use a circuit that's + * open to that exit. See what exit we meant, and whether we can use it. + */ if (conn->chosen_exit_name) { const node_t *node = node_get_by_nickname(conn->chosen_exit_name, 1); int opt = conn->chosen_exit_optional; @@ -2412,6 +2459,7 @@ connection_ap_handshake_attach_circuit(entry_connection_t *conn) "Requested exit point '%s' is not known. %s.", conn->chosen_exit_name, opt ? "Trying others" : "Closing"); if (opt) { + /* If we are allowed to ignore the .exit request, do so */ conn->chosen_exit_optional = 0; tor_free(conn->chosen_exit_name); return 0; @@ -2424,6 +2472,7 @@ connection_ap_handshake_attach_circuit(entry_connection_t *conn) "would refuse request. %s.", conn->chosen_exit_name, opt ? "Trying others" : "Closing"); if (opt) { + /* If we are allowed to ignore the .exit request, do so */ conn->chosen_exit_optional = 0; tor_free(conn->chosen_exit_name); return 0; @@ -2432,11 +2481,15 @@ connection_ap_handshake_attach_circuit(entry_connection_t *conn) } }

- /* find the circuit that we should use, if there is one. */ + /* Find the circuit that we should use, if there is one. Otherwise + * launch it. */ retval = circuit_get_open_circ_or_launch( conn, CIRCUIT_PURPOSE_C_GENERAL, &circ); - if (retval < 1) // XXXX++ if we totally fail, this still returns 0 -RD + if (retval < 1) { + /* We were either told "-1" (complete failure) or 0 (circuit in + * progress); we can't attach this stream yet. */ return retval; + }

log_debug(LD_APP|LD_CIRC, "Attaching apconn to circ %u (stream %d sec old).", @@ -2445,7 +2498,8 @@ connection_ap_handshake_attach_circuit(entry_connection_t *conn) * sucking. */ circuit_log_path(LOG_INFO,LD_APP|LD_CIRC,circ);

- /* We have found a suitable circuit for our conn. Hurray. */ + /* We have found a suitable circuit for our conn. Hurray. Do + * the attachment. */ return connection_ap_handshake_attach_chosen_circuit(conn, circ, NULL);

} else { /* we're a rendezvous conn */ diff --git a/src/or/connection_edge.c b/src/or/connection_edge.c index 1ee0c0f..6b68a19 100644 --- a/src/or/connection_edge.c +++ b/src/or/connection_edge.c @@ -830,7 +830,8 @@ connection_ap_rescan_and_attach_pending(void) #endif

/** Tell any AP streams that are listed as waiting for a new circuit to try - * again, either attaching to an available circ or launching a new one. + * again. If there is an available circuit for a stream, attach it. Otherwise, + * launch a new circuit. * * If <b>retry</b> is false, only check the list if it contains at least one * streams that we have not yet tried to attach to a circuit. @@ -845,8 +846,9 @@ connection_ap_attach_pending(int retry) if (untried_pending_connections == 0 && !retry) return;

- /* Don't allow modifications to pending_entry_connections while we are - * iterating over it. */ + /* Don't allow any modifications to list while we are iterating over + * it. We'll put streams back on this list if we can't attach them + * immediately. */ smartlist_t *pending = pending_entry_connections; pending_entry_connections = smartlist_new();

@@ -873,6 +875,7 @@ connection_ap_attach_pending(int retry) continue; }

+ /* Okay, we're through the sanity checks. Try to handle this stream. */ if (connection_ap_handshake_attach_circuit(entry_conn) < 0) { if (!conn->marked_for_close) connection_mark_unattached_ap(entry_conn, @@ -882,12 +885,17 @@ connection_ap_attach_pending(int retry) if (! conn->marked_for_close && conn->type == CONN_TYPE_AP && conn->state == AP_CONN_STATE_CIRCUIT_WAIT) { + /* Is it still waiting for a circuit? If so, we didn't attach it, + * so it's still pending. Put it back on the list. + */ if (!smartlist_contains(pending_entry_connections, entry_conn)) { smartlist_add(pending_entry_connections, entry_conn); continue; } }

+ /* If we got here, then we either closed the connection, or + * we attached it. */ UNMARK(); } SMARTLIST_FOREACH_END(entry_conn);

@@ -1186,6 +1194,8 @@ connection_ap_handshake_rewrite(entry_connection_t *conn,

/* Remember the original address so we can tell the user about what * they actually said, not just what it turned into. */ + /* XXX yes, this is the same as out->orig_address above. One is + * in the output, and one is in the connection. */ if (! conn->original_dest_address) { /* Is the 'if' necessary here? XXXX */ conn->original_dest_address = tor_strdup(conn->socks_request->address); @@ -1193,7 +1203,7 @@ connection_ap_handshake_rewrite(entry_connection_t *conn,

/* First, apply MapAddress and MAPADDRESS mappings. We need to do * these only for non-reverse lookups, since they don't exist for those. - * We need to do this before we consider automapping, since we might + * We also need to do this before we consider automapping, since we might * e.g. resolve irc.oftc.net into irconionaddress.onion, at which point * we'd need to automap it. */ if (socks->command != SOCKS_COMMAND_RESOLVE_PTR) { @@ -1205,9 +1215,12 @@ connection_ap_handshake_rewrite(entry_connection_t *conn, } }

- /* Now, handle automapping. Automapping happens when we're asked to - * resolve a hostname, and AutomapHostsOnResolve is set, and - * the hostname has a suffix listed in AutomapHostsSuffixes. + /* Now see if we need to create or return an existing Hostname->IP + * automapping. Automapping happens when we're asked to resolve a + * hostname, and AutomapHostsOnResolve is set, and the hostname has a + * suffix listed in AutomapHostsSuffixes. It's a handy feature + * that lets you have Tor assign e.g. IPv6 addresses for .onion + * names, and return them safely from DNSPort. */ if (socks->command == SOCKS_COMMAND_RESOLVE && tor_addr_parse(&addr_tmp, socks->address)<0 && @@ -1247,7 +1260,8 @@ connection_ap_handshake_rewrite(entry_connection_t *conn, }

/* Now handle reverse lookups, if they're in the cache. This doesn't - * happen too often, since client-side DNS caching is off by default. */ + * happen too often, since client-side DNS caching is off by default, + * and very deprecated. */ if (socks->command == SOCKS_COMMAND_RESOLVE_PTR) { unsigned rewrite_flags = 0; if (conn->entry_cfg.use_cached_ipv4_answers) @@ -1292,11 +1306,12 @@ connection_ap_handshake_rewrite(entry_connection_t *conn, } }

- /* If we didn't automap it before, then this is still the address - * that came straight from the user, mapped according to any - * MapAddress/MAPADDRESS commands. Now other mappings, including - * previously registered Automap entries, TrackHostExits entries, - * and client-side DNS cache entries (not recommended). + /* If we didn't automap it before, then this is still the address that + * came straight from the user, mapped according to any + * MapAddress/MAPADDRESS commands. Now apply other mappings, + * including previously registered Automap entries (IP back to + * hostname), TrackHostExits entries, and client-side DNS cache + * entries (if they're turned on). */ if (socks->command != SOCKS_COMMAND_RESOLVE_PTR && !out->automap) { @@ -1361,11 +1376,14 @@ connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn, time_t now = time(NULL); rewrite_result_t rr;

+ /* First we'll do the rewrite part. Let's see if we get a reasonable + * answer. + */ memset(&rr, 0, sizeof(rr)); connection_ap_handshake_rewrite(conn,&rr);

if (rr.should_close) { - /* connection_ap_handshake_rewrite told us to close the connection, + /* connection_ap_handshake_rewrite told us to close the connection: * either because it sent back an answer, or because it sent back an * error */ connection_mark_unattached_ap(conn, rr.end_reason); @@ -1379,8 +1397,8 @@ connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn, const int automap = rr.automap; const addressmap_entry_source_t exit_source = rr.exit_source;

- /* Parse the address provided by SOCKS. Modify it in-place if it - * specifies a hidden-service (.onion) or particular exit node (.exit). + /* Now, we parse the address to see if it's an .onion or .exit or + * other special address. */ const hostname_type_t addresstype = parse_extended_hostname(socks->address);

@@ -1394,8 +1412,8 @@ connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn, }

/* If this is a .exit hostname, strip off the .name.exit part, and - * see whether we're going to connect there, and otherwise handle it. - * (The ".exit" part got stripped off by "parse_extended_hostname"). + * see whether we're willing to connect there, and and otherwise handle the + * .exit address. * * We'll set chosen_exit_name and/or close the connection as appropriate. */ @@ -1407,7 +1425,7 @@ connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn, const node_t *node = NULL;

/* If this .exit was added by an AUTOMAP, then it came straight from - * a user. Make sure that options->AllowDotExit permits that. */ + * a user. Make sure that options->AllowDotExit permits that! */ if (exit_source == ADDRMAPSRC_AUTOMAP && !options->AllowDotExit) { /* Whoops; this one is stale. It must have gotten added earlier, * when AllowDotExit was on. */ @@ -1436,7 +1454,12 @@ connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn, }

tor_assert(!automap); - /* Now, find the character before the .(name) part. */ + + /* Now, find the character before the .(name) part. + * (The ".exit" part got stripped off by "parse_extended_hostname"). + * + * We're going to put the exit name into conn->chosen_exit_name, and + * look up a node correspondingly. */ char *s = strrchr(socks->address,'.'); if (s) { /* The address was of the form "(stuff).(name).exit */ @@ -1492,10 +1515,12 @@ connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn, implies no. */ }

- /* Now, handle everything that isn't a .onion address. */ + /* Now, we handle everything that isn't a .onion address. */ if (addresstype != ONION_HOSTNAME) { /* Not a hidden-service request. It's either a hostname or an IP, - * possibly with a .exit that we stripped off. */ + * possibly with a .exit that we stripped off. We're going to check + * if we're allowed to connect/resolve there, and then launch the + * appropriate request. */

/* Check for funny characters in the address. */ if (address_is_invalid_destination(socks->address, 1)) { @@ -1542,7 +1567,7 @@ connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn, }

/* Then check if we have a hostname or IP address, and whether DNS or - * the IP address family are permitted */ + * the IP address family are permitted. Reject if not. */ tor_addr_t dummy_addr; int socks_family = tor_addr_parse(&dummy_addr, socks->address); /* family will be -1 for a non-onion hostname that's not an IP */ @@ -1564,8 +1589,9 @@ connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn, safe_str_client(socks->address)); connection_mark_unattached_ap(conn, END_STREAM_REASON_ENTRYPOLICY); return -1; + } else { + tor_assert_nonfatal_unreached_once(); } - /* No else, we've covered all possible returned value. */

/* See if this is a hostname lookup that we can answer immediately. * (For example, an attempt to look up the IP address for an IP address.) @@ -1585,7 +1611,10 @@ connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn, } tor_assert(!automap); rep_hist_note_used_resolve(now); /* help predict this next time */ - } else if (socks->command == SOCKS_COMMAND_CONNECT) { + } + + /* Now see if this is a connect request that we can reject immediately */ + if (socks->command == SOCKS_COMMAND_CONNECT) { /* Special handling for attempts to connect */ tor_assert(!automap); /* Don't allow connections to port 0. */ @@ -1639,7 +1668,9 @@ connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn, } /* end "if we should check for internal addresses" */

/* Okay. We're still doing a CONNECT, and it wasn't a private - * address. Do special handling for literal IP addresses */ + * address. Here we do special handling for literal IP addresses, + * to see if we should reject this preemptively, and to set up + * fields in conn->entry_cfg to tell the exit what AF we want. */ { tor_addr_t addr; /* XXX Duplicate call to tor_addr_parse. */ @@ -1682,11 +1713,15 @@ connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn, } }

+ /* we never allow IPv6 answers on socks4. (TODO: Is this smart?) */ if (socks->socks_version == 4) conn->entry_cfg.ipv6_traffic = 0;

/* Still handling CONNECT. Now, check for exit enclaves. (Which we - * don't do on BEGINDIR, or there is a chosen exit.) + * don't do on BEGINDIR, or when there is a chosen exit.) + * + * TODO: Should we remove this? Exit enclaves are nutty and don't + * work very well */ if (!conn->use_begindir && !conn->chosen_exit_name && !circ) { /* see if we can find a suitable enclave exit */ @@ -1710,7 +1745,8 @@ connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn, if (consider_plaintext_ports(conn, socks->port) < 0) return -1;

- /* Remember the port so that we do predicted requests there. */ + /* Remember the port so that we will predict that more requests + there will happen in the future. */ if (!conn->use_begindir) { /* help predict this next time */ rep_hist_note_used_port(now, socks->port); @@ -1735,6 +1771,8 @@ connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn, if (circ) { rv = connection_ap_handshake_attach_chosen_circuit(conn, circ, cpath); } else { + /* We'll try to attach it at the next event loop, or whenever + * we call connection_ap_attach_pending() */ connection_ap_mark_as_pending_circuit(conn); rv = 0; } @@ -1811,8 +1849,8 @@ connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn, log_info(LD_REND,"Got a hidden service request for ID '%s'", safe_str_client(rend_data->onion_address));

- /* Lookup the given onion address. If invalid, stop right now else we - * might have it in the cache or not, it will be tested later on. */ + /* Lookup the given onion address. If invalid, stop right now. + * Otherwise, we might have it in the cache or not. */ unsigned int refetch_desc = 0; rend_cache_entry_t *entry = NULL; const int rend_cache_lookup_result = @@ -1826,6 +1864,7 @@ connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn, connection_mark_unattached_ap(conn, END_STREAM_REASON_TORPROTOCOL); return -1; case ENOENT: + /* We didn't have this; we should look it up. */ refetch_desc = 1; break; default: @@ -1835,8 +1874,9 @@ connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn, } }

- /* Help predict this next time. We're not sure if it will need - * a stable circuit yet, but we know we'll need *something*. */ + /* Help predict that we'll want to do hidden service circuits in the + * future. We're not sure if it will need a stable circuit yet, but + * we know we'll need *something*. */ rep_hist_note_used_internal(now, 0, 1);

/* Now we have a descriptor but is it usable or not? If not, refetch. @@ -1851,9 +1891,12 @@ connection_ap_handshake_rewrite_and_attach(entry_connection_t *conn, return 0; }

- /* We have the descriptor so launch a connection to the HS. */ + /* We have the descriptor! So launch a connection to the HS. */ base_conn->state = AP_CONN_STATE_CIRCUIT_WAIT; log_info(LD_REND, "Descriptor is here. Great."); + + /* We'll try to attach it at the next event loop, or whenever + * we call connection_ap_attach_pending() */ connection_ap_mark_as_pending_circuit(conn); return 0; }