[tor-commits] [tor/main] Implement congestion control parameter negotiation
dgoulet at torproject.org
dgoulet at torproject.org
Tue Feb 22 20:48:20 UTC 2022
commit b6d5fbba7d7e0e2cfa0c0cbb7f91e6039e3decf9
Author: Mike Perry <mikeperry-git at torproject.org>
Date: Thu Nov 4 00:44:38 2021 +0000
Implement congestion control parameter negotiation
---
src/core/crypto/onion_crypto.c | 200 +++++++++++++++++++++++++++++++++++------
src/core/crypto/onion_crypto.h | 10 ++-
src/core/mainloop/cpuworker.c | 22 ++++-
3 files changed, 198 insertions(+), 34 deletions(-)
diff --git a/src/core/crypto/onion_crypto.c b/src/core/crypto/onion_crypto.c
index 1e9913539f..13f8f54b35 100644
--- a/src/core/crypto/onion_crypto.c
+++ b/src/core/crypto/onion_crypto.c
@@ -41,15 +41,17 @@
#include "lib/crypt_ops/crypto_dh.h"
#include "lib/crypt_ops/crypto_util.h"
#include "feature/relay/routerkeys.h"
+#include "core/or/congestion_control_common.h"
#include "core/or/circuitbuild.h"
#include "core/or/crypt_path_st.h"
#include "core/or/extend_info_st.h"
+#include "trunnel/circ_params.h"
/* TODO-324: Add this to the specification! */
-const uint8_t NTOR3_CIRC_VERIFICATION[] = "circuit extend";
-const size_t NTOR3_CIRC_VERIFICATION_LEN = 14;
+static const uint8_t NTOR3_CIRC_VERIFICATION[] = "circuit extend";
+static const size_t NTOR3_CIRC_VERIFICATION_LEN = 14;
#define NTOR3_VERIFICATION_ARGS \
NTOR3_CIRC_VERIFICATION, NTOR3_CIRC_VERIFICATION_LEN
@@ -210,6 +212,93 @@ onion_skin_create(int type,
return r;
}
+/**
+ * Takes a param request message from the client, compares it to our
+ * consensus parameters, and creates a reply message and output
+ * parameters.
+ *
+ * This function runs in a worker thread, so it can only inspect
+ * arguments and local variables.
+ *
+ * Returns 0 if successful.
+ * Returns -1 on parsing, parameter failure, or reply creation failure.
+ */
+static int
+negotiate_v3_ntor_server_circ_params(const uint8_t *param_request_msg,
+ size_t param_request_len,
+ const circuit_params_t *our_ns_params,
+ circuit_params_t *params_out,
+ uint8_t **resp_msg_out,
+ size_t *resp_msg_len_out)
+{
+ circ_params_response_t *resp = NULL;
+ circ_params_request_t *param_request = NULL;
+ ssize_t resp_msg_len;
+
+ if (circ_params_request_parse(¶m_request, param_request_msg,
+ param_request_len) < 0) {
+ return -1;
+ }
+
+ /* CC is enabled if the client wants it, and our consensus paramers
+ * allow it. If both are true, its on. If either is false, it's off. */
+ params_out->cc_enabled =
+ circ_params_request_get_cc_supported(param_request) &&
+ our_ns_params->cc_enabled;
+
+ resp = circ_params_response_new();
+
+ if (circ_params_response_set_version(resp, 0) < 0) {
+ circ_params_request_free(param_request);
+ circ_params_response_free(resp);
+ return -1;
+ }
+
+ /* The relay always chooses its sendme_inc, and sends it to the client */
+ params_out->sendme_inc_cells = our_ns_params->sendme_inc_cells;
+
+ if (circ_params_response_set_sendme_inc_cells(resp,
+ our_ns_params->sendme_inc_cells) < 0) {
+ circ_params_request_free(param_request);
+ circ_params_response_free(resp);
+ return -1;
+ }
+
+ /* Use the negotiated cc_enabled value to respond */
+ if (circ_params_response_set_cc_enabled(resp, params_out->cc_enabled) < 0) {
+ circ_params_request_free(param_request);
+ circ_params_response_free(resp);
+ return -1;
+ }
+
+ resp_msg_len = circ_params_response_encoded_len(resp);
+
+ if (resp_msg_len < 0) {
+ circ_params_request_free(param_request);
+ circ_params_response_free(resp);
+ return -1;
+ }
+
+ *resp_msg_out = tor_malloc_zero(resp_msg_len);
+
+ resp_msg_len = circ_params_response_encode(*resp_msg_out, resp_msg_len,
+ resp);
+ if (resp_msg_len < 0) {
+ circ_params_request_free(param_request);
+ circ_params_response_free(resp);
+
+ tor_free(*resp_msg_out);
+ return -1;
+ }
+
+ *resp_msg_len_out = (size_t)resp_msg_len;
+
+ circ_params_request_free(param_request);
+ circ_params_response_free(resp);
+
+ return 0;
+}
+
/* This is the maximum value for keys_out_len passed to
* onion_skin_server_handshake, plus 16. We can make it bigger if needed:
* It just defines how many bytes to stack-allocate. */
@@ -226,6 +315,7 @@ int
onion_skin_server_handshake(int type,
const uint8_t *onion_skin, size_t onionskin_len,
const server_onion_keys_t *keys,
+ const circuit_params_t *our_ns_params,
uint8_t *reply_out,
size_t reply_out_maxlen,
uint8_t *keys_out, size_t keys_out_len,
@@ -233,7 +323,7 @@ onion_skin_server_handshake(int type,
circuit_params_t *params_out)
{
int r = -1;
- memset(params_out, 0, sizeof(*params_out)); // TODO-324: actually set this!
+ memset(params_out, 0, sizeof(*params_out));
switch (type) {
case ONION_HANDSHAKE_TYPE_TAP:
@@ -290,6 +380,9 @@ onion_skin_server_handshake(int type,
uint8_t keys_tmp[MAX_KEYS_TMP_LEN];
uint8_t *client_msg = NULL;
size_t client_msg_len = 0;
+ uint8_t *reply_msg = NULL;
+ size_t reply_msg_len = 0;
+
ntor3_server_handshake_state_t *state = NULL;
if (onion_skin_ntor3_server_handshake_part1(
@@ -303,25 +396,17 @@ onion_skin_server_handshake(int type,
return -1;
}
- uint8_t reply_msg[1] = { 0 };
- size_t reply_msg_len = 1;
- {
- /* TODO-324, Okay, we have a message from the client trying to negotiate
- * parameters. We need to decide whether the client's request is okay,
- * what we're going to say in response, and what circuit parameters
- * we've just negotiated
- */
-
- /* NOTE! DANGER, DANGER, DANGER!
-
- Remember that this function can be run in a worker thread, and so
- therefore you can't access "global" state that isn't lock-protected.
-
- CAVEAT HAXX0R!
- */
-
+ if (negotiate_v3_ntor_server_circ_params(client_msg,
+ client_msg_len,
+ our_ns_params,
+ params_out,
+ &reply_msg,
+ &reply_msg_len) < 0) {
+ ntor3_server_handshake_state_free(state);
tor_free(client_msg);
+ return -1;
}
+ tor_free(client_msg);
uint8_t *server_handshake = NULL;
size_t server_handshake_len = 0;
@@ -331,12 +416,15 @@ onion_skin_server_handshake(int type,
reply_msg, reply_msg_len,
&server_handshake, &server_handshake_len,
keys_tmp, keys_tmp_len) < 0) {
- // XXX TODO-324 free some stuff
+ tor_free(reply_msg);
+ ntor3_server_handshake_state_free(state);
return -1;
}
+ tor_free(reply_msg);
if (server_handshake_len > reply_out_maxlen) {
- // XXX TODO-324 free that stuff
+ tor_free(server_handshake);
+ ntor3_server_handshake_state_free(state);
return -1;
}
@@ -346,6 +434,7 @@ onion_skin_server_handshake(int type,
memwipe(keys_tmp, 0, keys_tmp_len);
memwipe(server_handshake, 0, server_handshake_len);
tor_free(server_handshake);
+ ntor3_server_handshake_state_free(state);
r = (int) server_handshake_len;
}
@@ -362,6 +451,61 @@ onion_skin_server_handshake(int type,
return r;
}
+/**
+ * Takes a param response message from the exit, compares it to our
+ * consensus parameters for sanity, and creates output parameters
+ * if sane.
+ *
+ * Returns -1 on parsing or insane params, 0 if success.
+ */
+static int
+negotiate_v3_ntor_client_circ_params(const uint8_t *param_response_msg,
+ size_t param_response_len,
+ circuit_params_t *params_out)
+{
+ circ_params_response_t *param_response = NULL;
+ bool cc_enabled;
+ uint8_t sendme_inc_cells;
+
+ if (circ_params_response_parse(¶m_response, param_response_msg,
+ param_response_len) < 0) {
+ return -1;
+ }
+
+ cc_enabled =
+ circ_params_response_get_cc_enabled(param_response);
+
+ /* If congestion control came back enabled, but we didn't ask for it
+ * because the consensus said no, close the circuit */
+ if (cc_enabled && !congestion_control_enabled()) {
+ circ_params_response_free(param_response);
+ return -1;
+ }
+ params_out->cc_enabled = cc_enabled;
+
+ /* We will only accept this response (and this circuit) if sendme_inc
+ * is within a factor of 2 of our consensus value. We should not need
+ * to change cc_sendme_inc much, and if we do, we can spread out those
+ * changes over smaller increments once every 4 hours. Exits that
+ * violate this range should just not be used. */
+#define MAX_SENDME_INC_NEGOTIATE_FACTOR 2
+
+ sendme_inc_cells =
+ circ_params_response_get_sendme_inc_cells(param_response);
+
+ if (sendme_inc_cells >
+ MAX_SENDME_INC_NEGOTIATE_FACTOR*congestion_control_sendme_inc() ||
+ sendme_inc_cells <
+ congestion_control_sendme_inc()/MAX_SENDME_INC_NEGOTIATE_FACTOR) {
+ circ_params_response_free(param_response);
+ return -1;
+ }
+ params_out->sendme_inc_cells = sendme_inc_cells;
+
+ circ_params_response_free(param_response);
+ return 0;
+}
+
/** Perform the final (client-side) step of a circuit-creation handshake of
* type <b>type</b>, using our state in <b>handshake_state</b> and the
* server's response in <b>reply</b>. On success, generate <b>keys_out_len</b>
@@ -382,7 +526,7 @@ onion_skin_client_handshake(int type,
if (handshake_state->tag != type)
return -1;
- memset(params_out, 0, sizeof(*params_out)); // TODO-324: actually set this!
+ memset(params_out, 0, sizeof(*params_out));
switch (type) {
case ONION_HANDSHAKE_TYPE_TAP:
@@ -450,10 +594,12 @@ onion_skin_client_handshake(int type,
return -1;
}
- {
- // XXXX TODO-324: see what the server said, make sure it's okay, see what
- // parameters it gave us, make sure we like them, and put them into
- // `params_out`
+ if (negotiate_v3_ntor_client_circ_params(server_msg,
+ server_msg_len,
+ params_out) < 0) {
+ tor_free(keys_tmp);
+ tor_free(server_msg);
+ return -1;
}
tor_free(server_msg);
diff --git a/src/core/crypto/onion_crypto.h b/src/core/crypto/onion_crypto.h
index 45e8eeca0c..cb0188ff54 100644
--- a/src/core/crypto/onion_crypto.h
+++ b/src/core/crypto/onion_crypto.h
@@ -29,10 +29,11 @@ void onion_handshake_state_release(onion_handshake_state_t *state);
* Parameters negotiated as part of a circuit handshake.
*/
typedef struct circuit_params_t {
- /* placeholder field for congestion control algorithm. Right now this
- * is always set to zero */
- int cc_algorithm;
- int cc_window;
+ /** Is true if congestion control is enabled in consensus or param,
+ * as per congestion_control_enabled() result. */
+ bool cc_enabled;
+ /** The number of cells in a sendme increment. Only used if cc_enabled=1. */
+ uint8_t sendme_inc_cells;
} circuit_params_t;
int onion_skin_create(int type,
@@ -43,6 +44,7 @@ int onion_skin_create(int type,
int onion_skin_server_handshake(int type,
const uint8_t *onion_skin, size_t onionskin_len,
const server_onion_keys_t *keys,
+ const circuit_params_t *ns_params,
uint8_t *reply_out,
size_t reply_out_maxlen,
uint8_t *keys_out, size_t key_out_len,
diff --git a/src/core/mainloop/cpuworker.c b/src/core/mainloop/cpuworker.c
index 7ca66a1c45..2cb667615d 100644
--- a/src/core/mainloop/cpuworker.c
+++ b/src/core/mainloop/cpuworker.c
@@ -21,6 +21,8 @@
#include "core/or/channel.h"
#include "core/or/circuitlist.h"
#include "core/or/connection_or.h"
+#include "core/or/congestion_control_common.h"
+#include "core/or/congestion_control_flow.h"
#include "app/config/config.h"
#include "core/mainloop/cpuworker.h"
#include "lib/crypt_ops/crypto_rand.h"
@@ -126,6 +128,11 @@ typedef struct cpuworker_request_t {
/** A create cell for the cpuworker to process. */
create_cell_t create_cell;
+ /**
+ * A copy of this relay's consensus params that are relevant to
+ * the circuit, for use in negotiation. */
+ circuit_params_t circ_ns_params;
+
/* Turn the above into a tagged union if needed. */
} cpuworker_request_t;
@@ -381,6 +388,12 @@ cpuworker_onion_handshake_replyfn(void *work_)
goto done_processing;
}
+ /* If the client asked for congestion control, if our consensus parameter
+ * allowed it to negotiate as enabled, allocate a congestion control obj. */
+ if (rpl.circ_params.cc_enabled) {
+ TO_CIRCUIT(circ)->ccontrol = congestion_control_new(&rpl.circ_params);
+ }
+
if (onionskin_answer(circ,
&rpl.created_cell,
(const char*)rpl.keys, sizeof(rpl.keys),
@@ -390,9 +403,6 @@ cpuworker_onion_handshake_replyfn(void *work_)
goto done_processing;
}
- /* TODO-324! We need to use rpl.circ_params here to initialize the congestion
- control parameters of the circuit. */
-
log_debug(LD_OR,"onionskin_answer succeeded. Yay.");
done_processing:
@@ -431,6 +441,7 @@ cpuworker_onion_handshake_threadfn(void *state_, void *work_)
n = onion_skin_server_handshake(cc->handshake_type,
cc->onionskin, cc->handshake_len,
onion_keys,
+ &req.circ_ns_params,
cell_out->reply,
sizeof(cell_out->reply),
rpl.keys, CPATH_KEY_MATERIAL_LEN,
@@ -559,6 +570,11 @@ assign_onionskin_to_cpuworker(or_circuit_t *circ,
if (should_time)
tor_gettimeofday(&req.started_at);
+ /* Copy the current cached consensus params relevant to
+ * circuit negotiation into the CPU worker context */
+ req.circ_ns_params.cc_enabled = congestion_control_enabled();
+ req.circ_ns_params.sendme_inc_cells = congestion_control_sendme_inc();
+
job = tor_malloc_zero(sizeof(cpuworker_job_t));
job->circ = circ;
memcpy(&job->u.request, &req, sizeof(req));
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