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Merge remote-tracking branch 'public/bug11553_024' into bug11553_025
Conflicts: src/or/channel.h
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commit
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changes/bug11553
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changes/bug11553
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@ -0,0 +1,15 @@
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o Minor features:
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- When we run out of usable circuit IDs on a channel, log only one
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warning for the whole channel, and include a description of
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how many circuits there were on the channel. Fix for part of ticket
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#11553.
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o Major features (performance):
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- Avoid wasting cycles looking for usable circuit IDs. Previously,
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when allocating a new circuit ID, we would in the worst case do a
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linear scan over the entire possible range of circuit IDs before
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deciding that we had exhausted our possibilities. Now, we
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try 64 circuit IDs at random before deciding that we probably
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won't succeed. Fix for a possible root cause of ticket
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#11553.
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@ -728,9 +728,6 @@ channel_init(channel_t *chan)
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/* Init timestamp */
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chan->timestamp_last_added_nonpadding = time(NULL);
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/* Init next_circ_id */
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chan->next_circ_id = crypto_rand_int(1 << 15);
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/* Initialize queues. */
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TOR_SIMPLEQ_INIT(&chan->incoming_queue);
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TOR_SIMPLEQ_INIT(&chan->outgoing_queue);
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@ -149,11 +149,8 @@ struct channel_s {
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circ_id_type_bitfield_t circ_id_type:2;
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/** DOCDOC*/
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unsigned wide_circ_ids:1;
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/**
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* Which circ_id do we try to use next on this connection? This is
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* always in the range 0..1<<15-1.
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*/
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circid_t next_circ_id;
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/** Have we logged a warning about circID exhaustion on this channel? */
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unsigned warned_circ_ids_exhausted:1;
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/** For how many circuits are we n_chan? What about p_chan? */
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unsigned int num_n_circuits, num_p_circuits;
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@ -77,18 +77,21 @@ channel_connect_for_circuit(const tor_addr_t *addr, uint16_t port,
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return chan;
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}
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/** Iterate over values of circ_id, starting from conn-\>next_circ_id,
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* and with the high bit specified by conn-\>circ_id_type, until we get
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* a circ_id that is not in use by any other circuit on that conn.
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/** Search for a value for circ_id that we can use on <b>chan</b> for an
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* outbound circuit, until we get a circ_id that is not in use by any other
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* circuit on that conn.
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*
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* Return it, or 0 if can't get a unique circ_id.
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*/
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static circid_t
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get_unique_circ_id_by_chan(channel_t *chan)
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{
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#define MAX_CIRCID_ATTEMPTS 64
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circid_t test_circ_id;
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circid_t attempts=0;
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circid_t high_bit, max_range;
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circid_t high_bit, max_range, mask;
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tor_assert(chan);
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@ -98,23 +101,40 @@ get_unique_circ_id_by_chan(channel_t *chan)
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"a client with no identity.");
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return 0;
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}
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max_range = (chan->wide_circ_ids) ? (1u<<31) : (1u<<15);
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max_range = (chan->wide_circ_ids) ? (1u<<31) : (1u<<15);
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mask = max_range - 1;
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high_bit = (chan->circ_id_type == CIRC_ID_TYPE_HIGHER) ? max_range : 0;
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do {
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/* Sequentially iterate over test_circ_id=1...max_range until we find a
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* circID such that (high_bit|test_circ_id) is not already used. */
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test_circ_id = chan->next_circ_id++;
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if (test_circ_id == 0 || test_circ_id >= max_range) {
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test_circ_id = 1;
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chan->next_circ_id = 2;
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}
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if (++attempts > max_range) {
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/* Make sure we don't loop forever if all circ_id's are used. This
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* matters because it's an external DoS opportunity.
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if (++attempts > MAX_CIRCID_ATTEMPTS) {
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/* Make sure we don't loop forever because all circuit IDs are used.
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*
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* Once, we would try until we had tried every possible circuit ID. But
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* that's quite expensive. Instead, we try MAX_CIRCID_ATTEMPTS random
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* circuit IDs, and then give up.
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*
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* This potentially causes us to give up early if our circuit ID space
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* is nearly full. If we have N circuit IDs in use, then we will reject
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* a new circuit with probability (N / max_range) ^ MAX_CIRCID_ATTEMPTS.
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* This means that in practice, a few percent of our circuit ID capacity
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* will go unused.
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*
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* The alternative here, though, is to do a linear search over the
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* whole circuit ID space every time we extend a circuit, which is
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* not so great either.
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*/
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log_warn(LD_CIRC,"No unused circ IDs. Failing.");
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if (! chan->warned_circ_ids_exhausted) {
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chan->warned_circ_ids_exhausted = 1;
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log_warn(LD_CIRC,"No unused circIDs found on channel %s wide "
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"circID support, with %u inbound and %u outbound circuits. "
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"Failing a circuit.",
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chan->wide_circ_ids ? "with" : "without",
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chan->num_p_circuits, chan->num_n_circuits);
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}
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return 0;
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}
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crypto_rand((char*) &test_circ_id, sizeof(test_circ_id));
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test_circ_id &= mask;
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test_circ_id |= high_bit;
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} while (circuit_id_in_use_on_channel(test_circ_id, chan));
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return test_circ_id;
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@ -271,8 +271,6 @@ dir_connection_new(int socket_family)
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*
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* Set timestamp_last_added_nonpadding to now.
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*
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* Assign a pseudorandom next_circ_id between 0 and 2**15.
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*
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* Initialize active_circuit_pqueue.
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*
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* Set active_circuit_pqueue_last_recalibrated to current cell_ewma tick.
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