prop224 prepwork: Introduce HS circuitmap subsystem.

The HS circuitmap is a hash table that maps introduction and rendezvous
tokens to specific circuits such that given a token it's easy to find
the corresponding circuit. It supports rend circuits and v2/v3 intro
circuits.

It will be used by the prop224 ESTABLISH_INTRO code to register and
lookup v3 introduction circuits.

The next commit after this removes the old code and fixes the unittests.
Please consult both commits while reviewing functionality differences
between the old and new code. Let me know if you want this rebased
differently :)

WRT architectural differences, this commit removes the rendinfo pointer
from or_circuit_t. It then adds an hs_token_t pointer and a hashtable
node for the HS circuitmap. IIUC, this adds another pointer to the
weight of or_circuit_t. Let me know if you don't like this, or if you
have suggestions on improving it.

1 files changed, 69 insertions, 0 deletions

diff --git a/src/or/hs_circuitmap.h b/src/or/hs_circuitmap.h
new file mode 100644
index 0000000000..a2be97c029
--- /dev/null
+++ b/src/or/hs_circuitmap.h
@@ -0,0 +1,69 @@
+/* Copyright (c) 2016, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file hs_circuitmap.h
+ * \brief Header file for hs_circuitmap.c.
+ **/
+
+#ifndef TOR_HS_CIRCUITMAP_H
+#define TOR_HS_CIRCUITMAP_H
+
+typedef HT_HEAD(hs_circuitmap_ht, or_circuit_t) hs_circuitmap_ht;
+
+typedef struct hs_token_s hs_token_t;
+typedef struct or_circuit_t or_circuit_t;
+
+/** Public HS circuitmap API: */
+
+or_circuit_t *hs_circuitmap_get_rend_circ(const uint8_t *cookie);
+or_circuit_t *
+hs_circuitmap_get_intro_circ_v3(const ed25519_public_key_t *auth_key);
+or_circuit_t *hs_circuitmap_get_intro_circ_v2(const uint8_t *digest);
+
+void hs_circuitmap_register_rend_circ(or_circuit_t *circ,
+                                      const uint8_t *cookie);
+void hs_circuitmap_register_intro_circ_v2(or_circuit_t *circ,
+                                          const uint8_t *digest);
+void hs_circuitmap_register_intro_circ_v3(or_circuit_t *circ,
+                                         const ed25519_public_key_t *auth_key);
+
+void hs_circuitmap_remove_circuit(or_circuit_t *circ);
+
+void hs_circuitmap_init(void);
+void hs_circuitmap_free_all(void);
+
+#ifdef HS_CIRCUITMAP_PRIVATE
+
+/** Represents the type of HS token. */
+typedef enum {
+  /** A rendezvous cookie (128bit)*/
+  HS_TOKEN_REND,
+  /** A v2 introduction point pubkey (160bit) */
+  HS_TOKEN_INTRO_V2,
+  /** A v3 introduction point pubkey (256bit) */
+  HS_TOKEN_INTRO_V3,
+} hs_token_type_t;
+
+/** Represents a token used in the HS protocol. Each such token maps to a
+ *  specific introduction or rendezvous circuit. */
+struct hs_token_s {
+  /* Type of HS token. */
+  hs_token_type_t type;
+
+  /* The size of the token (depends on the type). */
+  size_t token_len;
+
+  /* The token itself. Memory allocated at runtime. */
+  uint8_t *token;
+};
+
+#endif /* HS_CIRCUITMAP_PRIVATE */
+
+#ifdef TOR_UNIT_TESTS
+
+hs_circuitmap_ht *get_hs_circuitmap(void);
+
+#endif /* TOR_UNIT_TESTS */
+
+#endif /* TOR_HS_CIRCUITMAP_H */