Merge branch 'protover-rust-impl_squashed'

43 files changed, 1908 insertions, 331 deletions

diff --git a/Makefile.am b/Makefile.am
index ad2ceb66a9..137fb1edcb 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -26,7 +26,7 @@ TESTING_TOR_BINARY=$(top_builddir)/src/or/tor$(EXEEXT)
 endif
 
 if USE_RUST
-rust_ldadd=$(top_builddir)/src/rust/target/release/@TOR_RUST_UTIL_STATIC_NAME@
+rust_ldadd=$(top_builddir)/src/rust/target/release/@TOR_RUST_STATIC_NAME@
 else
 rust_ldadd=
 endif
diff --git a/changes/ticket22840 b/changes/ticket22840
new file mode 100644
index 0000000000..6d234fb0d4
--- /dev/null
+++ b/changes/ticket22840
@@ -0,0 +1,8 @@
+  o Major features (Rust experimentation):
+    - Tor now ships with an optional implementation of one of its smaller
+      modules (protover.c) in the Rust programming language.  To try it
+      out, install a Rust build environment, and configure Tor with
+      "--enable-rust --enable-cargo-online-mode".  This should not
+      cause any user-visible changes, but should help us gain more experience
+      with Rust, and plan future Rust integration work.
+      Implementation by Chelsea Komlo. Closes ticket 22840.
diff --git a/configure.ac b/configure.ac
index c026464269..0e93e8de5e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -439,12 +439,12 @@ if test "x$enable_rust" = "xyes"; then
   dnl For now both MSVC and MinGW rust libraries will output static libs with
   dnl the MSVC naming convention.
   if test "$bwin32" = "true"; then
-    TOR_RUST_UTIL_STATIC_NAME=tor_util.lib
+    TOR_RUST_STATIC_NAME=tor_rust.lib
   else
-    TOR_RUST_UTIL_STATIC_NAME=libtor_util.a
+    TOR_RUST_STATIC_NAME=libtor_rust.a
   fi
 
-  AC_SUBST(TOR_RUST_UTIL_STATIC_NAME)
+  AC_SUBST(TOR_RUST_STATIC_NAME)
   AC_SUBST(CARGO_ONLINE)
   AC_SUBST(RUST_DL)
 
diff --git a/src/common/compat_rust.c b/src/common/compat_rust.c
deleted file mode 100644
index 366fd4037b..0000000000
--- a/src/common/compat_rust.c
+++ /dev/null
@@ -1,39 +0,0 @@
-/* Copyright (c) 2017, The Tor Project, Inc. */
-/* See LICENSE for licensing information */
-
-/**
- * \file rust_compat.c
- * \brief Rust FFI compatibility functions and helpers. This file is only built
- * if Rust is not used.
- **/
-
-#include "compat_rust.h"
-#include "util.h"
-
-/**
- * Free storage pointed to by <b>str</b>, and itself.
- */
-void
-rust_str_free(rust_str_t str)
-{
-    char *s = (char *)str;
-    tor_free(s);
-}
-
-/**
- * Return zero-terminated contained string.
- */
-const char *
-rust_str_get(const rust_str_t str)
-{
-    return (const char *)str;
-}
-
-/* If we were using Rust, we'd say so on startup. */
-rust_str_t
-rust_welcome_string(void)
-{
-    char *s = tor_malloc_zero(1);
-    return (rust_str_t)s;
-}
-
diff --git a/src/common/compat_rust.h b/src/common/compat_rust.h
deleted file mode 100644
index 72fde39296..0000000000
--- a/src/common/compat_rust.h
+++ /dev/null
@@ -1,28 +0,0 @@
-/* Copyright (c) 2017, The Tor Project, Inc. */
-/* See LICENSE for licensing information */
-
-/**
- * \file rust_compat.h
- * \brief Headers for rust_compat.c
- **/
-
-#ifndef TOR_RUST_COMPAT_H
-#define TOR_RUST_COMPAT_H
-
-#include "torint.h"
-
-/**
- * Strings allocated in Rust must be freed from Rust code again. Let's make
- * it less likely to accidentally mess up and call tor_free() on it, because
- * currently it'll just work but might break at any time.
- */
-typedef uintptr_t rust_str_t;
-
-void rust_str_free(rust_str_t);
-
-const char *rust_str_get(const rust_str_t);
-
-rust_str_t rust_welcome_string(void);
-
-#endif /* !defined(TOR_RUST_COMPAT_H) */
-
diff --git a/src/common/include.am b/src/common/include.am
index cd5eea3404..2856c40fdc 100644
--- a/src/common/include.am
+++ b/src/common/include.am
@@ -101,11 +101,6 @@ LIBOR_A_SRC = \
   $(threads_impl_source)				\
   $(readpassphrase_source)
 
-if USE_RUST
-else
-LIBOR_A_SRC += src/common/compat_rust.c
-endif
-
 src/common/src_common_libor_testing_a-log.$(OBJEXT) \
   src/common/log.$(OBJEXT): micro-revision.i
 
@@ -156,7 +151,6 @@ COMMONHEADERS = \
   src/common/compat.h				\
   src/common/compat_libevent.h			\
   src/common/compat_openssl.h			\
-  src/common/compat_rust.h			\
   src/common/compat_threads.h			\
   src/common/compat_time.h			\
   src/common/compress.h				\
diff --git a/src/or/include.am b/src/or/include.am
index 7216aba9af..3ff71d5ad7 100644
--- a/src/or/include.am
+++ b/src/or/include.am
@@ -78,6 +78,7 @@ LIBTOR_A_SOURCES = \
 	src/or/parsecommon.c			\
 	src/or/periodic.c				\
 	src/or/protover.c				\
+	src/or/protover_rust.c				\
 	src/or/proto_cell.c				\
 	src/or/proto_control0.c				\
 	src/or/proto_ext_or.c				\
diff --git a/src/or/main.c b/src/or/main.c
index 4ab5f311fe..7c6941fc0e 100644
--- a/src/or/main.c
+++ b/src/or/main.c
@@ -60,7 +60,6 @@
 #include "circuitlist.h"
 #include "circuituse.h"
 #include "command.h"
-#include "compat_rust.h"
 #include "compress.h"
 #include "config.h"
 #include "confparse.h"
@@ -128,6 +127,10 @@
 
 void evdns_shutdown(int);
 
+// helper function defined in Rust to output a log message indicating if tor is
+// running with Rust enabled. See src/rust/tor_util
+char *rust_welcome_string(void);
+
 /********* PROTOTYPES **********/
 
 static void dumpmemusage(int severity);
@@ -3111,14 +3114,13 @@ tor_init(int argc, char *argv[])
                  "Expect more bugs than usual.");
   }
 
-  {
-    rust_str_t rust_str = rust_welcome_string();
-    const char *s = rust_str_get(rust_str);
-    if (strlen(s) > 0) {
-      log_notice(LD_GENERAL, "%s", s);
-    }
-    rust_str_free(rust_str);
+#ifdef HAVE_RUST
+  char *rust_str = rust_welcome_string();
+  if (rust_str != NULL && strlen(rust_str) > 0) {
+    log_notice(LD_GENERAL, "%s", rust_str);
   }
+  tor_free(rust_str);
+#endif
 
   if (network_init()<0) {
     log_err(LD_BUG,"Error initializing network; exiting.");
diff --git a/src/or/protover.c b/src/or/protover.c
index 1a3e69be10..0e74deb112 100644
--- a/src/or/protover.c
+++ b/src/or/protover.c
@@ -27,6 +27,8 @@
 #include "protover.h"
 #include "routerparse.h"
 
+#ifndef HAVE_RUST
+
 static const smartlist_t *get_supported_protocol_list(void);
 static int protocol_list_contains(const smartlist_t *protos,
                                   protocol_type_t pr, uint32_t ver);
@@ -735,3 +737,5 @@ protover_free_all(void)
   }
 }
 
+#endif
+
diff --git a/src/or/protover.h b/src/or/protover.h
index 657977279e..7f1938e0c9 100644
--- a/src/or/protover.h
+++ b/src/or/protover.h
@@ -70,11 +70,15 @@ typedef struct proto_entry_t {
   smartlist_t *ranges;
 } proto_entry_t;
 
+#if !defined(HAVE_RUST) && defined(TOR_UNIT_TESTS)
 STATIC smartlist_t *parse_protocol_list(const char *s);
-STATIC void proto_entry_free(proto_entry_t *entry);
 STATIC char *encode_protocol_list(const smartlist_t *sl);
 STATIC const char *protocol_type_to_str(protocol_type_t pr);
 STATIC int str_to_protocol_type(const char *s, protocol_type_t *pr_out);
+STATIC void proto_entry_free(proto_entry_t *entry);
+
+#endif
+
 #endif /* defined(PROTOVER_PRIVATE) */
 
 #endif /* !defined(TOR_PROTOVER_H) */
diff --git a/src/or/protover_rust.c b/src/or/protover_rust.c
new file mode 100644
index 0000000000..27f19c5fea
--- /dev/null
+++ b/src/or/protover_rust.c
@@ -0,0 +1,19 @@
+/* Copyright (c) 2016-2017, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/*
+ * \file protover_rust.c
+ * \brief Provide a C wrapper for functions exposed in /src/rust/protover,
+ * and safe translation/handling between the Rust/C boundary.
+ */
+
+#include "or.h"
+#include "protover.h"
+
+#ifdef HAVE_RUST
+
+/* Define for compatibility, used in main.c */
+void protover_free_all(void) {};
+
+#endif
+
diff --git a/src/rust/Cargo.lock b/src/rust/Cargo.lock
index 4ac9606ce8..224d2135bf 100644
--- a/src/rust/Cargo.lock
+++ b/src/rust/Cargo.lock
@@ -3,6 +3,14 @@ name = "tor_util"
 version = "0.0.1"
 dependencies = [
  "libc 0.2.22 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tor_allocate 0.0.1",
+]
+
+[[package]]
+name = "external"
+version = "0.0.1"
+dependencies = [
+ "libc 0.2.22 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -10,5 +18,38 @@ name = "libc"
 version = "0.2.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "protover"
+version = "0.0.1"
+dependencies = [
+ "external 0.0.1",
+ "libc 0.2.22 (registry+https://github.com/rust-lang/crates.io-index)",
+ "smartlist 0.0.1",
+ "tor_allocate 0.0.1",
+ "tor_util 0.0.1",
+]
+
+[[package]]
+name = "smartlist"
+version = "0.0.1"
+dependencies = [
+ "libc 0.2.22 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "tor_allocate"
+version = "0.0.1"
+dependencies = [
+ "libc 0.2.22 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "tor_rust"
+version = "0.1.0"
+dependencies = [
+ "protover 0.0.1",
+ "tor_util 0.0.1",
+]
+
 [metadata]
 "checksum libc 0.2.22 (registry+https://github.com/rust-lang/crates.io-index)" = "babb8281da88cba992fa1f4ddec7d63ed96280a1a53ec9b919fd37b53d71e502"
diff --git a/src/rust/Cargo.toml b/src/rust/Cargo.toml
index fc4377e8b4..953c9b96b7 100644
--- a/src/rust/Cargo.toml
+++ b/src/rust/Cargo.toml
@@ -1,5 +1,5 @@
 [workspace]
-members = ["tor_util"]
+members = ["tor_util", "protover", "smartlist", "external", "tor_allocate", "tor_rust"]
 
 [profile.release]
 debug = true
diff --git a/src/rust/external/Cargo.toml b/src/rust/external/Cargo.toml
new file mode 100644
index 0000000000..bccd7033a7
--- /dev/null
+++ b/src/rust/external/Cargo.toml
@@ -0,0 +1,13 @@
+[package]
+authors = ["The Tor Project"]
+version = "0.0.1"
+name = "external"
+
+[dependencies]
+libc = "0.2.22"
+
+[lib]
+name = "external"
+path = "lib.rs"
+crate_type = ["rlib", "staticlib"]
+
diff --git a/src/rust/external/external.rs b/src/rust/external/external.rs
new file mode 100644
index 0000000000..b9e17f021d
--- /dev/null
+++ b/src/rust/external/external.rs
@@ -0,0 +1,33 @@
+// Copyright (c) 2016-2017, The Tor Project, Inc. */
+// See LICENSE for licensing information */
+
+use libc::{c_char, c_int};
+use std::ffi::CString;
+
+extern "C" {
+    fn tor_version_as_new_as(
+        platform: *const c_char,
+        cutoff: *const c_char,
+    ) -> c_int;
+}
+
+/// Wrap calls to tor_version_as_new_as, defined in src/or/routerparse.c
+pub fn c_tor_version_as_new_as(platform: &str, cutoff: &str) -> bool {
+    // CHK: These functions should log a warning if an error occurs. This
+    // can be added when integration with tor's logger is added to rust
+    let c_platform = match CString::new(platform) {
+        Ok(n) => n,
+        Err(_) => return false,
+    };
+
+    let c_cutoff = match CString::new(cutoff) {
+        Ok(n) => n,
+        Err(_) => return false,
+    };
+
+    let result: c_int = unsafe {
+        tor_version_as_new_as(c_platform.as_ptr(), c_cutoff.as_ptr())
+    };
+
+    result == 1
+}
diff --git a/src/rust/external/lib.rs b/src/rust/external/lib.rs
new file mode 100644
index 0000000000..0af0d6452d
--- /dev/null
+++ b/src/rust/external/lib.rs
@@ -0,0 +1,14 @@
+//! Copyright (c) 2016-2017, The Tor Project, Inc. */
+//! See LICENSE for licensing information */
+
+//! Interface for external calls to tor C ABI
+//!
+//! The purpose of this module is to provide a clean interface for when Rust
+//! modules need to interact with functionality in tor C code rather than each
+//! module implementing this functionality repeatedly.
+
+extern crate libc;
+
+mod external;
+
+pub use external::*;
diff --git a/src/rust/include.am b/src/rust/include.am
index 20afc6c4db..025d921b31 100644
--- a/src/rust/include.am
+++ b/src/rust/include.am
@@ -1,4 +1,4 @@
-include src/rust/tor_util/include.am
+include src/rust/tor_rust/include.am
 
 EXTRA_DIST +=\
 	src/rust/Cargo.toml \
diff --git a/src/rust/protover/Cargo.toml b/src/rust/protover/Cargo.toml
new file mode 100644
index 0000000000..04d2f2ed7d
--- /dev/null
+++ b/src/rust/protover/Cargo.toml
@@ -0,0 +1,25 @@
+[package]
+authors = ["The Tor Project"]
+version = "0.0.1"
+name = "protover"
+
+[dependencies]
+libc = "0.2.22"
+
+[dependencies.smartlist]
+path = "../smartlist"
+
+[dependencies.external]
+path = "../external"
+
+[dependencies.tor_util]
+path = "../tor_util"
+
+[dependencies.tor_allocate]
+path = "../tor_allocate"
+
+[lib]
+name = "protover"
+path = "lib.rs"
+crate_type = ["rlib", "staticlib"]
+
diff --git a/src/rust/protover/ffi.rs b/src/rust/protover/ffi.rs
new file mode 100644
index 0000000000..cf2e9fd783
--- /dev/null
+++ b/src/rust/protover/ffi.rs
@@ -0,0 +1,185 @@
+// Copyright (c) 2016-2017, The Tor Project, Inc. */
+// See LICENSE for licensing information */
+
+//! FFI functions, only to be called from C.
+//!
+//! Equivalent C versions of this api are in `src/or/protover.c`
+
+use libc::{c_char, c_int, uint32_t};
+use std::ffi::CStr;
+use std::ffi::CString;
+
+use protover::*;
+use smartlist::*;
+use tor_allocate::allocate_and_copy_string;
+
+/// Translate C enums to Rust Proto enums, using the integer value of the C
+/// enum to map to its associated Rust enum
+/// This is dependant on the associated C enum preserving ordering.
+fn translate_to_rust(c_proto: uint32_t) -> Result<Proto, &'static str> {
+    match c_proto {
+        0 => Ok(Proto::Link),
+        1 => Ok(Proto::LinkAuth),
+        2 => Ok(Proto::Relay),
+        3 => Ok(Proto::DirCache),
+        4 => Ok(Proto::HSDir),
+        5 => Ok(Proto::HSIntro),
+        6 => Ok(Proto::HSRend),
+        7 => Ok(Proto::Desc),
+        8 => Ok(Proto::Microdesc),
+        9 => Ok(Proto::Cons),
+        _ => Err("Invalid protocol type"),
+    }
+}
+
+/// Provide an interface for C to translate arguments and return types for
+/// protover::all_supported
+#[no_mangle]
+pub extern "C" fn protover_all_supported(
+    c_relay_version: *const c_char,
+    missing_out: *mut *mut c_char,
+) -> c_int {
+
+    if c_relay_version.is_null() {
+        return 1;
+    }
+
+    // Require an unsafe block to read the version from a C string. The pointer
+    // is checked above to ensure it is not null.
+    let c_str: &CStr = unsafe { CStr::from_ptr(c_relay_version) };
+
+    let relay_version = match c_str.to_str() {
+        Ok(n) => n,
+        Err(_) => return 1,
+    };
+
+    let (is_supported, unsupported) = all_supported(relay_version);
+
+    if unsupported.len() > 0 {
+        let c_unsupported = match CString::new(unsupported) {
+            Ok(n) => n,
+            Err(_) => return 1,
+        };
+
+        let ptr = c_unsupported.into_raw();
+        unsafe { *missing_out = ptr };
+    }
+
+    return if is_supported { 1 } else { 0 };
+}
+
+/// Provide an interface for C to translate arguments and return types for
+/// protover::list_supports_protocol
+#[no_mangle]
+pub extern "C" fn protocol_list_supports_protocol(
+    c_protocol_list: *const c_char,
+    c_protocol: uint32_t,
+    version: uint32_t,
+) -> c_int {
+    if c_protocol_list.is_null() {
+        return 1;
+    }
+
+    // Require an unsafe block to read the version from a C string. The pointer
+    // is checked above to ensure it is not null.
+    let c_str: &CStr = unsafe { CStr::from_ptr(c_protocol_list) };
+
+    let protocol_list = match c_str.to_str() {
+        Ok(n) => n,
+        Err(_) => return 1,
+    };
+
+    let protocol = match translate_to_rust(c_protocol) {
+        Ok(n) => n,
+        Err(_) => return 0,
+    };
+
+    let is_supported =
+        protover_string_supports_protocol(protocol_list, protocol, version);
+
+    return if is_supported { 1 } else { 0 };
+}
+
+/// Provide an interface for C to translate arguments and return types for
+/// protover::get_supported_protocols
+#[no_mangle]
+pub extern "C" fn protover_get_supported_protocols() -> *mut c_char {
+    // Not handling errors when unwrapping as the content is controlled
+    // and is an empty string
+    let empty = CString::new("").unwrap();
+
+    let supported = get_supported_protocols();
+    let c_supported = match CString::new(supported) {
+        Ok(n) => n,
+        Err(_) => return empty.into_raw(),
+    };
+
+    c_supported.into_raw()
+}
+
+/// Provide an interface for C to translate arguments and return types for
+/// protover::compute_vote
+#[no_mangle]
+pub extern "C" fn protover_compute_vote(
+    list: *const Stringlist,
+    threshold: c_int,
+) -> *mut c_char {
+
+    if list.is_null() {
+        let empty = String::new();
+        return allocate_and_copy_string(&empty);
+    }
+
+    // Dereference of raw pointer requires an unsafe block. The pointer is
+    // checked above to ensure it is not null.
+    let data: Vec<String> = unsafe { (*list).get_list() };
+
+    let vote = compute_vote(data, threshold);
+
+    allocate_and_copy_string(&vote)
+}
+
+/// Provide an interface for C to translate arguments and return types for
+/// protover::is_supported_here
+#[no_mangle]
+pub extern "C" fn protover_is_supported_here(
+    c_protocol: uint32_t,
+    version: uint32_t,
+) -> c_int {
+    let protocol = match translate_to_rust(c_protocol) {
+        Ok(n) => n,
+        Err(_) => return 0,
+    };
+
+    let is_supported = is_supported_here(protocol, version);
+
+    return if is_supported { 1 } else { 0 };
+}
+
+/// Provide an interface for C to translate arguments and return types for
+/// protover::compute_for_old_tor
+#[no_mangle]
+pub extern "C" fn protover_compute_for_old_tor(
+    version: *const c_char,
+) -> *mut c_char {
+    // Not handling errors when unwrapping as the content is controlled
+    // and is an empty string
+    let empty = String::new();
+
+    if version.is_null() {
+        return allocate_and_copy_string(&empty);
+    }
+
+    // Require an unsafe block to read the version from a C string. The pointer
+    // is checked above to ensure it is not null.
+    let c_str: &CStr = unsafe { CStr::from_ptr(version) };
+
+    let version = match c_str.to_str() {
+        Ok(n) => n,
+        Err(_) => return allocate_and_copy_string(&empty),
+    };
+
+    let supported = compute_for_old_tor(&version);
+
+    allocate_and_copy_string(&supported)
+}
diff --git a/src/rust/protover/lib.rs b/src/rust/protover/lib.rs
new file mode 100644
index 0000000000..5a5dea4408
--- /dev/null
+++ b/src/rust/protover/lib.rs
@@ -0,0 +1,33 @@
+//! Copyright (c) 2016-2017, The Tor Project, Inc. */
+//! See LICENSE for licensing information */
+
+//! Versioning information for different pieces of the Tor protocol.
+//!
+//! The below description is taken from src/rust/protover.c, which is currently
+//! enabled by default. We are in the process of experimenting with Rust in
+//! tor, and this protover module is implemented to help achieve this goal.
+//!
+//! Starting in version 0.2.9.3-alpha, Tor places separate version numbers on
+//! each of the different components of its protocol. Relays use these numbers
+//! to advertise what versions of the protocols they can support, and clients
+//! use them to find what they can ask a given relay to do.  Authorities vote
+//! on the supported protocol versions for each relay, and also vote on the
+//! which protocols you should have to support in order to be on the Tor
+//! network. All Tor instances use these required/recommended protocol versions
+//! to tell what level of support for recent protocols each relay has, and
+//! to decide whether they should be running given their current protocols.
+//!
+//! The main advantage of these protocol versions numbers over using Tor
+//! version numbers is that they allow different implementations of the Tor
+//! protocols to develop independently, without having to claim compatibility
+//! with specific versions of Tor.
+
+extern crate libc;
+extern crate smartlist;
+extern crate external;
+extern crate tor_allocate;
+
+mod protover;
+pub mod ffi;
+
+pub use protover::*;
diff --git a/src/rust/protover/protover.rs b/src/rust/protover/protover.rs
new file mode 100644
index 0000000000..11e9d0079e
--- /dev/null
+++ b/src/rust/protover/protover.rs
@@ -0,0 +1,851 @@
+// Copyright (c) 2016-2017, The Tor Project, Inc. */
+// See LICENSE for licensing information */
+
+use external::c_tor_version_as_new_as;
+
+use std::str::FromStr;
+use std::fmt;
+use std::collections::{HashMap, HashSet};
+use std::string::String;
+
+/// The first version of Tor that included "proto" entries in its descriptors.
+/// Authorities should use this to decide whether to guess proto lines.
+const FIRST_TOR_VERSION_TO_ADVERTISE_PROTOCOLS: &'static str = "0.2.9.3-alpha";
+
+/// The maximum number of subprotocol version numbers we will attempt to expand
+/// before concluding that someone is trying to DoS us
+const MAX_PROTOCOLS_TO_EXPAND: u32 = 500;
+
+/// Currently supported protocols and their versions
+const SUPPORTED_PROTOCOLS: &'static [&'static str] = &[
+    "Cons=1-2",
+    "Desc=1-2",
+    "DirCache=1-2",
+    "HSDir=1-2",
+    "HSIntro=3-4",
+    "HSRend=1-2",
+    "Link=1-4",
+    "LinkAuth=1,3",
+    "Microdesc=1-2",
+    "Relay=1-2",
+];
+
+/// Known subprotocols in Tor. Indicates which subprotocol a relay supports.
+#[derive(Hash, Eq, PartialEq, Debug)]
+pub enum Proto {
+    Cons,
+    Desc,
+    DirCache,
+    HSDir,
+    HSIntro,
+    HSRend,
+    Link,
+    LinkAuth,
+    Microdesc,
+    Relay,
+}
+
+impl fmt::Display for Proto {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{:?}", self)
+    }
+}
+
+/// Translates a string representation of a protocol into a Proto type.
+/// Error if the string is an unrecognized protocol name.
+impl FromStr for Proto {
+    type Err = &'static str;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "Cons" => Ok(Proto::Cons),
+            "Desc" => Ok(Proto::Desc),
+            "DirCache" => Ok(Proto::DirCache),
+            "HSDir" => Ok(Proto::HSDir),
+            "HSIntro" => Ok(Proto::HSIntro),
+            "HSRend" => Ok(Proto::HSRend),
+            "Link" => Ok(Proto::Link),
+            "LinkAuth" => Ok(Proto::LinkAuth),
+            "Microdesc" => Ok(Proto::Microdesc),
+            "Relay" => Ok(Proto::Relay),
+            _ => Err("Not a valid protocol type"),
+        }
+    }
+}
+
+/// Get the string representation of current supported protocols
+///
+/// # Returns
+///
+/// A `String` whose value is the existing protocols supported by tor.
+/// Returned data is in the format as follows:
+///
+/// "HSDir=1-1 LinkAuth=1"
+///
+pub fn get_supported_protocols() -> String {
+    SUPPORTED_PROTOCOLS.join(" ")
+}
+
+/// Translates a vector representation of a protocol list into a HashMap
+fn parse_protocols(
+    protocols: &[&str],
+) -> Result<HashMap<Proto, HashSet<u32>>, &'static str> {
+    let mut parsed = HashMap::new();
+
+    for subproto in protocols {
+        let (name, version) = get_proto_and_vers(subproto)?;
+        parsed.insert(name, version);
+    }
+    Ok(parsed)
+}
+
+/// Translates a string representation of a protocol list to a HashMap
+fn parse_protocols_from_string<'a>(
+    protocol_string: &'a str,
+) -> Result<HashMap<Proto, HashSet<u32>>, &'static str> {
+    let protocols: &[&'a str] =
+        &protocol_string.split(" ").collect::<Vec<&'a str>>()[..];
+
+    parse_protocols(protocols)
+}
+
+/// Translates supported tor versions from  a string into a HashMap, which is
+/// useful when looking up a specific subprotocol.
+///
+/// # Returns
+///
+/// A `Result` whose `Ok` value is a `HashMap<Proto, <u32>>` holding all
+/// subprotocols and versions currently supported by tor.
+///
+/// The returned `Result`'s `Err` value is an `&'static str` with a description
+/// of the error.
+///
+fn tor_supported() -> Result<HashMap<Proto, HashSet<u32>>, &'static str> {
+    parse_protocols(&SUPPORTED_PROTOCOLS)
+}
+
+/// Get the unique version numbers supported by a subprotocol.
+///
+/// # Inputs
+///
+/// * `version_string`, a string comprised of "[0-9,-]"
+///
+/// # Returns
+///
+/// A `Result` whose `Ok` value is a `HashSet<u32>` holding all of the unique
+/// version numbers.  If there were ranges in the `version_string`, then these
+/// are expanded, i.e. `"1-3"` would expand to `HashSet<u32>::new([1, 2, 3])`.
+/// The returned HashSet is *unordered*.
+///
+/// The returned `Result`'s `Err` value is an `&'static str` with a description
+/// of the error.
+///
+/// # Errors
+///
+/// This function will error if:
+///
+/// * the `version_string` is empty or contains an equals (`"="`) sign,
+/// * the expansion of a version range produces an error (see
+///  `expand_version_range`),
+/// * any single version number is not parseable as an `u32` in radix 10, or
+/// * there are greater than 2^16 version numbers to expand.
+///
+fn get_versions(version_string: &str) -> Result<HashSet<u32>, &'static str> {
+    if version_string.is_empty() {
+        return Err("version string is empty");
+    }
+
+    let mut versions = HashSet::<u32>::new();
+
+    for piece in version_string.split(",") {
+        if piece.contains("-") {
+            for p in expand_version_range(piece)? {
+                versions.insert(p);
+            }
+        } else {
+            versions.insert(u32::from_str(piece).or(
+                Err("invalid protocol entry"),
+            )?);
+        }
+
+        if versions.len() > MAX_PROTOCOLS_TO_EXPAND as usize {
+            return Err("Too many versions to expand");
+        }
+    }
+    Ok(versions)
+}
+
+
+/// Parse the subprotocol type and its version numbers.
+///
+/// # Inputs
+///
+/// * A `protocol_entry` string, comprised of a keyword, an "=" sign, and one
+/// or more version numbers.
+///
+/// # Returns
+///
+/// A `Result` whose `Ok` value is a tuple of `(Proto, HashSet<u32>)`, where the
+/// first element is the subprotocol type (see `protover::Proto`) and the last
+/// element is a(n unordered) set of unique version numbers which are supported.
+/// Otherwise, the `Err` value of this `Result` is a description of the error
+///
+fn get_proto_and_vers<'a>(
+    protocol_entry: &'a str,
+) -> Result<(Proto, HashSet<u32>), &'static str> {
+    let mut parts = protocol_entry.splitn(2, "=");
+
+    let proto = match parts.next() {
+        Some(n) => n,
+        None => return Err("invalid protover entry"),
+    };
+
+    let vers = match parts.next() {
+        Some(n) => n,
+        None => return Err("invalid protover entry"),
+    };
+
+    let versions = get_versions(vers)?;
+    let proto_name = proto.parse()?;
+
+    Ok((proto_name, versions))
+}
+
+/// Parses a single subprotocol entry string into subprotocol and version
+/// parts, and then checks whether any of those versions are unsupported.
+/// Helper for protover::all_supported
+///
+/// # Inputs
+///
+/// Accepted data is in the string format as follows:
+///
+/// "HSDir=1-1"
+///
+/// # Returns
+///
+/// Returns `true` if the protocol entry is well-formatted and only contains
+/// versions that are also supported in tor. Otherwise, returns false
+///
+fn contains_only_supported_protocols(proto_entry: &str) -> bool {
+    let (name, mut vers) = match get_proto_and_vers(proto_entry) {
+        Ok(n) => n,
+        Err(_) => return false,
+    };
+
+    let currently_supported: HashMap<Proto, HashSet<u32>> =
+        match tor_supported() {
+            Ok(n) => n,
+            Err(_) => return false,
+        };
+
+    let supported_versions = match currently_supported.get(&name) {
+        Some(n) => n,
+        None => return false,
+    };
+
+    vers.retain(|x| !supported_versions.contains(x));
+    vers.is_empty()
+}
+
+/// Determine if we support every protocol a client supports, and if not,
+/// determine which protocols we do not have support for.
+///
+/// # Inputs
+///
+/// Accepted data is in the string format as follows:
+///
+/// "HSDir=1-1 LinkAuth=1-2"
+///
+/// # Returns
+///
+/// Return `true` if every protocol version is one that we support.
+/// Otherwise, return `false`.
+/// Optionally, return parameters which the client supports but which we do not
+///
+/// # Examples
+/// ```
+/// use protover::all_supported;
+///
+/// let (is_supported, unsupported)  = all_supported("Link=1");
+/// assert_eq!(true, is_supported);
+///
+/// let (is_supported, unsupported)  = all_supported("Link=5-6");
+/// assert_eq!(false, is_supported);
+/// assert_eq!("Link=5-6", unsupported);
+///
+pub fn all_supported(protocols: &str) -> (bool, String) {
+    let unsupported = protocols
+        .split_whitespace()
+        .filter(|v| !contains_only_supported_protocols(v))
+        .collect::<Vec<&str>>();
+
+    (unsupported.is_empty(), unsupported.join(" "))
+}
+
+/// Return true iff the provided protocol list includes support for the
+/// indicated protocol and version.
+/// Otherwise, return false
+///
+/// # Inputs
+///
+/// * `list`, a string representation of a list of protocol entries.
+/// * `proto`, a `Proto` to test support for
+/// * `vers`, a `u32` version which we will go on to determine whether the
+/// specified protocol supports.
+///
+/// # Examples
+/// ```
+/// use protover::*;
+///
+/// let is_supported = protover_string_supports_protocol("Link=3-4 Cons=1",
+///                                                      Proto::Cons,1);
+/// assert_eq!(true, is_supported);
+///
+/// let is_not_supported = protover_string_supports_protocol("Link=3-4 Cons=1",
+///                                                           Proto::Cons,5);
+/// assert_eq!(false, is_not_supported)
+/// ```
+pub fn protover_string_supports_protocol(
+    list: &str,
+    proto: Proto,
+    vers: u32,
+) -> bool {
+    let supported: HashMap<Proto, HashSet<u32>>;
+
+    match parse_protocols_from_string(list) {
+        Ok(result) => supported = result,
+        Err(_) => return false,
+    }
+
+    let supported_versions = match supported.get(&proto) {
+        Some(n) => n,
+        None => return false,
+    };
+
+    supported_versions.contains(&vers)
+}
+
+/// Fully expand a version range. For example, 1-3 expands to 1,2,3
+/// Helper for get_versions
+///
+/// # Inputs
+///
+/// `range`, a string comprised of "[0-9,-]"
+///
+/// # Returns
+///
+/// A `Result` whose `Ok` value a vector of unsigned integers representing the
+/// expanded range of supported versions by a single protocol.
+/// Otherwise, the `Err` value of this `Result` is a description of the error
+///
+/// # Errors
+///
+/// This function will error if:
+///
+/// * the specified range is empty
+/// * the version range does not contain both a valid lower and upper bound.
+///
+fn expand_version_range(range: &str) -> Result<Vec<u32>, &'static str> {
+    if range.is_empty() {
+        return Err("version string empty");
+    }
+
+    let mut parts = range.split("-");
+
+    let lower_string = parts.next().ok_or(
+        "cannot parse protocol range lower bound",
+    )?;
+
+    let lower = u32::from_str_radix(lower_string, 10).or(Err(
+        "cannot parse protocol range lower bound",
+    ))?;
+
+    let higher_string = parts.next().ok_or(
+        "cannot parse protocol range upper bound",
+    )?;
+
+    let higher = u32::from_str_radix(higher_string, 10).or(Err(
+        "cannot parse protocol range upper bound",
+    ))?;
+
+    // We can use inclusive range syntax when it becomes stable.
+    Ok((lower..higher + 1).collect())
+}
+
+/// Checks to see if there is a continuous range of integers, starting at the
+/// first in the list. Returns the last integer in the range if a range exists.
+/// Helper for compute_vote
+///
+/// # Inputs
+///
+/// `list`, an ordered  vector of `u32` integers of "[0-9,-]" representing the
+/// supported versions for a single protocol.
+///
+/// # Returns
+///
+/// A `bool` indicating whether the list contains a range, starting at the
+/// first in the list, and an `u32` of the last integer in the range.
+///
+/// For example, if given vec![1, 2, 3, 5], find_range will return true,
+/// as there is a continuous range, and 3, which is the last number in the
+/// continuous range.
+///
+fn find_range(list: &Vec<u32>) -> (bool, u32) {
+    if list.len() == 0 {
+        return (false, 0);
+    }
+
+    let mut iterable = list.iter().peekable();
+    let mut range_end = match iterable.next() {
+        Some(n) => *n,
+        None => return (false, 0),
+    };
+
+    let mut has_range = false;
+
+    while iterable.peek().is_some() {
+        let n = *iterable.next().unwrap();
+        if n != range_end + 1 {
+            break;
+        }
+
+        has_range = true;
+        range_end = n;
+    }
+
+    (has_range, range_end)
+}
+
+/// Contracts a HashSet representation of supported versions into a string.
+/// Helper for compute_vote
+///
+/// # Inputs
+///
+/// `supported_set`, a set of integers of "[0-9,-]" representing the
+/// supported versions for a single protocol.
+///
+/// # Returns
+///
+/// A `String` representation of this set in ascending order.
+///
+fn contract_protocol_list<'a>(supported_set: &'a HashSet<u32>) -> String {
+    let mut supported_clone = supported_set.clone();
+    let mut supported: Vec<u32> = supported_clone.drain().collect();
+    supported.sort();
+
+    let mut final_output: Vec<String> = Vec::new();
+
+    while supported.len() != 0 {
+        let (has_range, end) = find_range(&supported);
+        let current = supported.remove(0);
+
+        if has_range {
+            final_output.push(format!(
+                "{}-{}",
+                current.to_string(),
+                &end.to_string(),
+            ));
+            supported.retain(|&x| x > end);
+        } else {
+            final_output.push(current.to_string());
+        }
+    }
+
+    final_output.join(",")
+}
+
+/// Parses a protocol list without validating the protocol names
+///
+/// # Inputs
+///
+/// * `protocol_string`, a string comprised of keys and values, both which are
+/// strings. The keys are the protocol names while values are a string
+/// representation of the supported versions.
+///
+/// The input is _not_ expected to be a subset of the Proto types
+///
+/// # Returns
+///
+/// A `Result` whose `Ok` value is a `HashSet<u32>` holding all of the unique
+/// version numbers.
+///
+/// The returned `Result`'s `Err` value is an `&'static str` with a description
+/// of the error.
+///
+/// # Errors
+///
+/// This function will error if:
+///
+/// * The protocol string does not follow the "protocol_name=version_list"
+/// expected format
+/// * If the version string is malformed. See `get_versions`.
+///
+fn parse_protocols_from_string_with_no_validation<'a>(
+    protocol_string: &'a str,
+) -> Result<HashMap<String, HashSet<u32>>, &'static str> {
+    let protocols = &protocol_string.split(" ").collect::<Vec<&'a str>>()[..];
+
+    let mut parsed: HashMap<String, HashSet<u32>> = HashMap::new();
+
+    for subproto in protocols {
+        let mut parts = subproto.splitn(2, "=");
+
+        let name = match parts.next() {
+            Some(n) => n,
+            None => return Err("invalid protover entry"),
+        };
+
+        let vers = match parts.next() {
+            Some(n) => n,
+            None => return Err("invalid protover entry"),
+        };
+
+        let versions = get_versions(vers)?;
+
+        parsed.insert(String::from(name), versions);
+    }
+    Ok(parsed)
+}
+
+/// Protocol voting implementation.
+///
+/// Given a list of strings describing protocol versions, return a new
+/// string encoding all of the protocols that are listed by at
+/// least threshold of the inputs.
+///
+/// The string is sorted according to the following conventions:
+///   - Protocols names are alphabetized
+///   - Protocols are in order low to high
+///   - Individual and ranges are listed together. For example,
+///     "3, 5-10,13"
+///   - All entries are unique
+///
+/// # Examples
+/// ```
+/// use protover::compute_vote;
+///
+/// let protos = vec![String::from("Link=3-4"), String::from("Link=3")];
+/// let vote = compute_vote(protos, 2);
+/// assert_eq!("Link=3", vote)
+/// ```
+pub fn compute_vote(
+    list_of_proto_strings: Vec<String>,
+    threshold: i32,
+) -> String {
+    let empty = String::from("");
+
+    if list_of_proto_strings.is_empty() {
+        return empty;
+    }
+
+    // all_count is a structure to represent the count of the number of
+    // supported versions for a specific protocol. For example, in JSON format:
+    // {
+    //  "FirstSupportedProtocol": {
+    //      "1": "3",
+    //      "2": "1"
+    //  }
+    // }
+    // means that FirstSupportedProtocol has three votes which support version
+    // 1, and one vote that supports version 2
+    let mut all_count: HashMap<String, HashMap<u32, usize>> = HashMap::new();
+
+    // parse and collect all of the protos and their versions and collect them
+    for vote in list_of_proto_strings {
+        let this_vote: HashMap<String, HashSet<u32>> =
+            match parse_protocols_from_string_with_no_validation(&vote) {
+                Ok(result) => result,
+                Err(_) => continue,
+            };
+
+        for (protocol, versions) in this_vote {
+            let supported_vers: &mut HashMap<u32, usize> =
+                all_count.entry(protocol).or_insert(HashMap::new());
+
+            for version in versions {
+                let counter: &mut usize =
+                    supported_vers.entry(version).or_insert(0);
+                *counter += 1;
+            }
+        }
+    }
+
+    let mut final_output: HashMap<String, String> =
+        HashMap::with_capacity(SUPPORTED_PROTOCOLS.len());
+
+    // Go through and remove verstions that are less than the threshold
+    for (protocol, versions) in all_count {
+        let mut meets_threshold = HashSet::new();
+        for (version, count) in versions {
+            if count >= threshold as usize {
+                meets_threshold.insert(version);
+            }
+        }
+
+        // For each protocol, compress its version list into the expected
+        // protocol version string format
+        let contracted = contract_protocol_list(&meets_threshold);
+        if !contracted.is_empty() {
+            final_output.insert(protocol, contracted);
+        }
+    }
+
+    write_vote_to_string(&final_output)
+}
+
+/// Return a String comprised of protocol entries in alphabetical order
+///
+/// # Inputs
+///
+/// * `vote`, a `HashMap` comprised of keys and values, both which are strings.
+/// The keys are the protocol names while values are a string representation of
+/// the supported versions.
+///
+/// # Returns
+///
+/// A `String` whose value is series of pairs, comprising of the protocol name
+/// and versions that it supports. The string takes the following format:
+///
+/// "first_protocol_name=1,2-5, second_protocol_name=4,5"
+///
+/// Sorts the keys in alphabetical order and creates the expected subprotocol
+/// entry format.
+///
+fn write_vote_to_string(vote: &HashMap<String, String>) -> String {
+    let mut keys: Vec<&String> = vote.keys().collect();
+    keys.sort();
+
+    let mut output = Vec::new();
+    for key in keys {
+        // TODO error in indexing here?
+        output.push(format!("{}={}", key, vote[key]));
+    }
+    output.join(" ")
+}
+
+/// Returns a boolean indicating whether the given protocol and version is
+/// supported in any of the existing Tor protocols
+///
+/// # Examples
+/// ```
+/// use protover::*;
+///
+/// let is_supported = is_supported_here(Proto::Link, 5);
+/// assert_eq!(false, is_supported);
+///
+/// let is_supported = is_supported_here(Proto::Link, 1);
+/// assert_eq!(true, is_supported);
+/// ```
+pub fn is_supported_here(proto: Proto, vers: u32) -> bool {
+    let currently_supported: HashMap<Proto, HashSet<u32>>;
+
+    match tor_supported() {
+        Ok(result) => currently_supported = result,
+        Err(_) => return false,
+    }
+
+    let supported_versions = match currently_supported.get(&proto) {
+        Some(n) => n,
+        None => return false,
+    };
+
+    supported_versions.contains(&vers)
+}
+
+/// Older versions of Tor cannot infer their own subprotocols
+/// Used to determine which subprotocols are supported by older Tor versions.
+///
+/// # Inputs
+///
+/// * `version`, a string comprised of "[0-9,-]"
+///
+/// # Returns
+///
+/// A `String` whose value is series of pairs, comprising of the protocol name
+/// and versions that it supports. The string takes the following format:
+///
+/// "HSDir=1-1 LinkAuth=1"
+///
+/// This function returns the protocols that are supported by the version input,
+/// only for tor versions older than FIRST_TOR_VERSION_TO_ADVERTISE_PROTOCOLS.
+///
+pub fn compute_for_old_tor(version: &str) -> String {
+    if c_tor_version_as_new_as(
+        version,
+        FIRST_TOR_VERSION_TO_ADVERTISE_PROTOCOLS,
+    )
+    {
+        return String::new();
+    }
+
+    if c_tor_version_as_new_as(version, "0.2.9.1-alpha") {
+        let ret = "Cons=1-2 Desc=1-2 DirCache=1 HSDir=1 HSIntro=3 HSRend=1-2 \
+                   Link=1-4 LinkAuth=1 Microdesc=1-2 Relay=1-2";
+        return String::from(ret);
+    }
+
+    if c_tor_version_as_new_as(version, "0.2.7.5") {
+        let ret = "Cons=1-2 Desc=1-2 DirCache=1 HSDir=1 HSIntro=3 HSRend=1 \
+                   Link=1-4 LinkAuth=1 Microdesc=1-2 Relay=1-2";
+        return String::from(ret);
+    }
+
+    if c_tor_version_as_new_as(version, "0.2.4.19") {
+        let ret = "Cons=1 Desc=1 DirCache=1 HSDir=1 HSIntro=3 HSRend=1 \
+                   Link=1-4 LinkAuth=1 Microdesc=1 Relay=1-2";
+        return String::from(ret);
+    }
+    String::new()
+}
+
+#[cfg(test)]
+mod test {
+    #[test]
+    fn test_get_versions() {
+        use std::collections::HashSet;
+
+        use super::get_versions;
+
+        assert_eq!(Err("version string is empty"), get_versions(""));
+        assert_eq!(Err("invalid protocol entry"), get_versions("a,b"));
+        assert_eq!(Err("invalid protocol entry"), get_versions("1,!"));
+
+        {
+            let mut versions: HashSet<u32> = HashSet::new();
+            versions.insert(1);
+            assert_eq!(Ok(versions), get_versions("1"));
+        }
+        {
+            let mut versions: HashSet<u32> = HashSet::new();
+            versions.insert(1);
+            versions.insert(2);
+            assert_eq!(Ok(versions), get_versions("1,2"));
+        }
+        {
+            let mut versions: HashSet<u32> = HashSet::new();
+            versions.insert(1);
+            versions.insert(2);
+            versions.insert(3);
+            assert_eq!(Ok(versions), get_versions("1-3"));
+        }
+        {
+            let mut versions: HashSet<u32> = HashSet::new();
+            versions.insert(1);
+            versions.insert(2);
+            versions.insert(5);
+            assert_eq!(Ok(versions), get_versions("1-2,5"));
+        }
+        {
+            let mut versions: HashSet<u32> = HashSet::new();
+            versions.insert(1);
+            versions.insert(3);
+            versions.insert(4);
+            versions.insert(5);
+            assert_eq!(Ok(versions), get_versions("1,3-5"));
+        }
+    }
+
+    #[test]
+    fn test_contains_only_supported_protocols() {
+        use super::contains_only_supported_protocols;
+
+        assert_eq!(false, contains_only_supported_protocols(""));
+        assert_eq!(false, contains_only_supported_protocols("Cons="));
+        assert_eq!(true, contains_only_supported_protocols("Cons=1"));
+        assert_eq!(false, contains_only_supported_protocols("Cons=0"));
+        assert_eq!(false, contains_only_supported_protocols("Cons=0-1"));
+        assert_eq!(false, contains_only_supported_protocols("Cons=5"));
+        assert_eq!(false, contains_only_supported_protocols("Cons=1-5"));
+        assert_eq!(false, contains_only_supported_protocols("Cons=1,5"));
+        assert_eq!(false, contains_only_supported_protocols("Cons=5,6"));
+        assert_eq!(false, contains_only_supported_protocols("Cons=1,5,6"));
+        assert_eq!(true, contains_only_supported_protocols("Cons=1,2"));
+        assert_eq!(true, contains_only_supported_protocols("Cons=1-2"));
+    }
+
+    #[test]
+    fn test_find_range() {
+        use super::find_range;
+
+        assert_eq!((false, 0), find_range(&vec![]));
+        assert_eq!((false, 1), find_range(&vec![1]));
+        assert_eq!((true, 2), find_range(&vec![1, 2]));
+        assert_eq!((true, 3), find_range(&vec![1, 2, 3]));
+        assert_eq!((true, 3), find_range(&vec![1, 2, 3, 5]));
+    }
+
+    #[test]
+    fn test_expand_version_range() {
+        use super::expand_version_range;
+
+        assert_eq!(Err("version string empty"), expand_version_range(""));
+        assert_eq!(Ok(vec![1, 2]), expand_version_range("1-2"));
+        assert_eq!(Ok(vec![1, 2, 3, 4]), expand_version_range("1-4"));
+        assert_eq!(
+            Err("cannot parse protocol range lower bound"),
+            expand_version_range("a")
+        );
+        assert_eq!(
+            Err("cannot parse protocol range upper bound"),
+            expand_version_range("1-a")
+        );
+    }
+
+    #[test]
+    fn test_contract_protocol_list() {
+        use std::collections::HashSet;
+        use super::contract_protocol_list;
+
+        {
+            let mut versions = HashSet::<u32>::new();
+            assert_eq!(String::from(""), contract_protocol_list(&versions));
+
+            versions.insert(1);
+            assert_eq!(String::from("1"), contract_protocol_list(&versions));
+
+            versions.insert(2);
+            assert_eq!(String::from("1-2"), contract_protocol_list(&versions));
+        }
+
+        {
+            let mut versions = HashSet::<u32>::new();
+            versions.insert(1);
+            versions.insert(3);
+            assert_eq!(String::from("1,3"), contract_protocol_list(&versions));
+        }
+
+        {
+            let mut versions = HashSet::<u32>::new();
+            versions.insert(1);
+            versions.insert(2);
+            versions.insert(3);
+            versions.insert(4);
+            assert_eq!(String::from("1-4"), contract_protocol_list(&versions));
+        }
+
+        {
+            let mut versions = HashSet::<u32>::new();
+            versions.insert(1);
+            versions.insert(3);
+            versions.insert(5);
+            versions.insert(6);
+            versions.insert(7);
+            assert_eq!(
+                String::from("1,3,5-7"),
+                contract_protocol_list(&versions)
+            );
+        }
+
+        {
+            let mut versions = HashSet::<u32>::new();
+            versions.insert(1);
+            versions.insert(2);
+            versions.insert(3);
+            versions.insert(500);
+            assert_eq!(
+                String::from("1-3,500"),
+                contract_protocol_list(&versions)
+            );
+        }
+    }
+}
diff --git a/src/rust/protover/tests/protover.rs b/src/rust/protover/tests/protover.rs
new file mode 100644
index 0000000000..f4e394b3e2
--- /dev/null
+++ b/src/rust/protover/tests/protover.rs
@@ -0,0 +1,291 @@
+// Copyright (c) 2016-2017, The Tor Project, Inc. */
+// See LICENSE for licensing information */
+
+extern crate protover;
+
+#[test]
+fn parse_protocol_list_with_single_proto_and_single_version() {
+    let protocol = "Cons=1";
+    let (is_supported, unsupported) = protover::all_supported(protocol);
+    assert_eq!(true, is_supported);
+    assert_eq!("", &unsupported);
+}
+
+#[test]
+fn parse_protocol_list_with_single_protocol_and_multiple_versions() {
+    let protocol = "Cons=1-2";
+    let (is_supported, unsupported) = protover::all_supported(protocol);
+    assert_eq!(true, is_supported);
+    assert_eq!("", &unsupported);
+}
+
+#[test]
+fn parse_protocol_list_with_different_single_protocol_and_single_version() {
+    let protocol = "HSDir=1";
+    let (is_supported, unsupported) = protover::all_supported(protocol);
+    assert_eq!(true, is_supported);
+    assert_eq!("", &unsupported);
+}
+
+#[test]
+fn parse_protocol_list_with_single_protocol_and_supported_version() {
+    let protocol = "Desc=2";
+    let (is_supported, unsupported) = protover::all_supported(protocol);
+    assert_eq!(true, is_supported);
+    assert_eq!("", &unsupported);
+}
+
+#[test]
+fn parse_protocol_list_with_two_protocols_and_single_version() {
+    let protocols = "Cons=1 HSDir=1";
+    let (is_supported, unsupported) = protover::all_supported(protocols);
+    assert_eq!(true, is_supported);
+    assert_eq!("", &unsupported);
+}
+
+
+#[test]
+fn parse_protocol_list_with_single_protocol_and_two_nonsequential_versions() {
+    let protocol = "Desc=1,2";
+    let (is_supported, unsupported) = protover::all_supported(protocol);
+    assert_eq!(true, is_supported);
+    assert_eq!("", &unsupported);
+}
+
+
+#[test]
+fn parse_protocol_list_with_single_protocol_and_two_sequential_versions() {
+    let protocol = "Desc=1-2";
+    let (is_supported, unsupported) = protover::all_supported(protocol);
+    assert_eq!(true, is_supported);
+    assert_eq!("", &unsupported);
+}
+
+#[test]
+fn parse_protocol_list_with_single_protocol_and_protocol_range_returns_set() {
+    let protocol = "Link=1-4";
+    let (is_supported, unsupported) = protover::all_supported(protocol);
+    assert_eq!(true, is_supported);
+    assert_eq!("", &unsupported);
+}
+
+#[test]
+fn parse_protocol_list_with_single_protocol_and_protocol_set() {
+    let protocols = "Link=3-4 Desc=2";
+    let (is_supported, unsupported) = protover::all_supported(protocols);
+    assert_eq!(true, is_supported);
+    assert_eq!("", &unsupported);
+}
+
+#[test]
+fn protover_all_supported_with_two_values() {
+    let protocols = "Microdesc=1-2 Relay=2";
+    let (is_supported, unsupported) = protover::all_supported(protocols);
+    assert_eq!("", &unsupported);
+    assert_eq!(true, is_supported);
+}
+
+#[test]
+fn protover_all_supported_with_one_value() {
+    let protocols = "Microdesc=1-2";
+    let (is_supported, unsupported) = protover::all_supported(protocols);
+    assert_eq!("", &unsupported);
+    assert_eq!(true, is_supported);
+}
+
+#[test]
+fn protover_all_supported_with_empty() {
+    let protocols = "";
+    let (is_supported, unsupported) = protover::all_supported(protocols);
+    assert_eq!(true, is_supported);
+    assert_eq!("", &unsupported);
+}
+
+#[test]
+fn protover_all_supported_with_three_values() {
+    let protocols = "LinkAuth=1 Microdesc=1-2 Relay=2";
+    let (is_supported, unsupported) = protover::all_supported(protocols);
+    assert_eq!("", &unsupported);
+    assert_eq!(true, is_supported);
+}
+
+#[test]
+fn protover_all_supported_with_unsupported_protocol() {
+    let protocols = "Wombat=9";
+    let (is_supported, unsupported) = protover::all_supported(protocols);
+    assert_eq!(false, is_supported);
+    assert_eq!("Wombat=9", &unsupported);
+}
+
+#[test]
+fn protover_all_supported_with_unsupported_versions() {
+    let protocols = "Link=3-999";
+    let (is_supported, unsupported) = protover::all_supported(protocols);
+    assert_eq!(false, is_supported);
+    assert_eq!("Link=3-999", &unsupported);
+}
+
+#[test]
+fn protover_all_supported_with_unsupported_low_version() {
+    let protocols = "Cons=0-1";
+    let (is_supported, unsupported) = protover::all_supported(protocols);
+    assert_eq!(false, is_supported);
+    assert_eq!("Cons=0-1", &unsupported);
+}
+
+#[test]
+fn protover_all_supported_with_unsupported_high_version() {
+    let protocols = "Cons=1-3";
+    let (is_supported, unsupported) = protover::all_supported(protocols);
+    assert_eq!(false, is_supported);
+    assert_eq!("Cons=1-3", &unsupported);
+}
+
+#[test]
+fn protover_all_supported_with_mix_of_supported_and_unsupproted() {
+    let protocols = "Link=3-4 Wombat=9";
+    let (is_supported, unsupported) = protover::all_supported(protocols);
+    assert_eq!(false, is_supported);
+    assert_eq!("Wombat=9", &unsupported);
+}
+
+#[test]
+fn protover_string_supports_protocol_returns_true_for_single_supported() {
+    let protocols = "Link=3-4 Cons=1";
+    let is_supported = protover::protover_string_supports_protocol(
+        protocols,
+        protover::Proto::Cons,
+        1,
+    );
+    assert_eq!(true, is_supported);
+}
+
+#[test]
+fn protover_string_supports_protocol_returns_false_for_single_unsupported() {
+    let protocols = "Link=3-4 Cons=1";
+    let is_supported = protover::protover_string_supports_protocol(
+        protocols,
+        protover::Proto::Cons,
+        2,
+    );
+    assert_eq!(false, is_supported);
+}
+
+#[test]
+fn protover_string_supports_protocol_returns_false_for_unsupported() {
+    let protocols = "Link=3-4";
+    let is_supported = protover::protover_string_supports_protocol(
+        protocols,
+        protover::Proto::Cons,
+        2,
+    );
+    assert_eq!(false, is_supported);
+}
+
+#[test]
+fn protover_all_supported_with_unexpected_characters() {
+    let protocols = "Cons=*-%";
+    let (is_supported, unsupported) = protover::all_supported(protocols);
+    assert_eq!(false, is_supported);
+    assert_eq!("Cons=*-%", &unsupported);
+}
+
+#[test]
+fn protover_compute_vote_returns_empty_for_empty_string() {
+    let protocols = vec![String::from("")];
+    let listed = protover::compute_vote(protocols, 1);
+    assert_eq!("", listed);
+}
+
+#[test]
+fn protover_compute_vote_returns_single_protocol_for_matching() {
+    let protocols = vec![String::from("Cons=1")];
+    let listed = protover::compute_vote(protocols, 1);
+    assert_eq!("Cons=1", listed);
+}
+
+#[test]
+fn protover_compute_vote_returns_two_protocols_for_two_matching() {
+    let protocols = vec![String::from("Link=1 Cons=1")];
+    let listed = protover::compute_vote(protocols, 1);
+    assert_eq!("Cons=1 Link=1", listed);
+}
+
+#[test]
+fn protover_compute_vote_returns_one_protocol_when_one_out_of_two_matches() {
+    let protocols = vec![String::from("Cons=1 Link=2"), String::from("Cons=1")];
+    let listed = protover::compute_vote(protocols, 2);
+    assert_eq!("Cons=1", listed);
+}
+
+#[test]
+fn protover_compute_vote_returns_protocols_that_it_doesnt_currently_support() {
+    let protocols = vec![String::from("Foo=1 Cons=2"), String::from("Bar=1")];
+    let listed = protover::compute_vote(protocols, 1);
+    assert_eq!("Bar=1 Cons=2 Foo=1", listed);
+}
+
+#[test]
+fn protover_compute_vote_returns_matching_for_mix() {
+    let protocols = vec![String::from("Link=1-10,500 Cons=1,3-7,8")];
+    let listed = protover::compute_vote(protocols, 1);
+    assert_eq!("Cons=1,3-8 Link=1-10,500", listed);
+}
+
+#[test]
+fn protover_compute_vote_returns_matching_for_longer_mix() {
+    let protocols = vec![
+        String::from("Desc=1-10,500 Cons=1,3-7,8"),
+        String::from("Link=123-456,78 Cons=2-6,8 Desc=9"),
+    ];
+
+    let listed = protover::compute_vote(protocols, 1);
+    assert_eq!("Cons=1-8 Desc=1-10,500 Link=78,123-456", listed);
+}
+
+#[test]
+fn protover_compute_vote_returns_matching_for_longer_mix_with_threshold_two() {
+    let protocols = vec![
+        String::from("Desc=1-10,500 Cons=1,3-7,8"),
+        String::from("Link=123-456,78 Cons=2-6,8 Desc=9"),
+    ];
+
+    let listed = protover::compute_vote(protocols, 2);
+    assert_eq!("Cons=3-6,8 Desc=9", listed);
+}
+
+#[test]
+fn protover_compute_vote_handles_duplicated_versions() {
+    let protocols = vec![String::from("Cons=1"), String::from("Cons=1")];
+    assert_eq!("Cons=1", protover::compute_vote(protocols, 2));
+
+    let protocols = vec![String::from("Cons=1-2"), String::from("Cons=1-2")];
+    assert_eq!("Cons=1-2", protover::compute_vote(protocols, 2));
+}
+
+#[test]
+fn protover_compute_vote_handles_invalid_proto_entries() {
+    let protocols = vec![
+        String::from("Cons=1"),
+        String::from("Cons=1"),
+        String::from("Link=a"),
+    ];
+    assert_eq!("Cons=1", protover::compute_vote(protocols, 2));
+
+    let protocols = vec![
+        String::from("Cons=1"),
+        String::from("Cons=1"),
+        String::from("Link=1-%"),
+    ];
+    assert_eq!("Cons=1", protover::compute_vote(protocols, 2));
+}
+
+#[test]
+fn protover_is_supported_here_returns_true_for_supported_protocol() {
+    assert_eq!(true, protover::is_supported_here(protover::Proto::Cons, 1));
+}
+
+#[test]
+fn protover_is_supported_here_returns_false_for_unsupported_protocol() {
+    assert_eq!(false, protover::is_supported_here(protover::Proto::Cons, 5));
+}
diff --git a/src/rust/smartlist/Cargo.toml b/src/rust/smartlist/Cargo.toml
new file mode 100644
index 0000000000..51f486c4d7
--- /dev/null
+++ b/src/rust/smartlist/Cargo.toml
@@ -0,0 +1,13 @@
+[package]
+authors = ["The Tor Project"]
+version = "0.0.1"
+name = "smartlist"
+
+[dependencies]
+libc = "0.2.22"
+
+[lib]
+name = "smartlist"
+path = "lib.rs"
+crate_type = ["rlib", "staticlib"]
+
diff --git a/src/rust/smartlist/lib.rs b/src/rust/smartlist/lib.rs
new file mode 100644
index 0000000000..14a8148315
--- /dev/null
+++ b/src/rust/smartlist/lib.rs
@@ -0,0 +1,8 @@
+// Copyright (c) 2016-2017, The Tor Project, Inc. */
+// See LICENSE for licensing information */
+
+extern crate libc;
+
+mod smartlist;
+
+pub use smartlist::*;
diff --git a/src/rust/smartlist/smartlist.rs b/src/rust/smartlist/smartlist.rs
new file mode 100644
index 0000000000..ec5d7a57f5
--- /dev/null
+++ b/src/rust/smartlist/smartlist.rs
@@ -0,0 +1,115 @@
+// Copyright (c) 2016-2017, The Tor Project, Inc. */
+// See LICENSE for licensing information */
+
+use std::slice;
+use libc::{c_char, c_int};
+use std::ffi::CStr;
+
+/// Smartlists are a type used in C code in tor to define a collection of a
+/// generic type, which has a capacity and a number used. Each Smartlist
+/// defines how to extract the list of values from the underlying C structure
+///
+/// Implementations are required to have a C representation, as this module
+/// serves purely to translate smartlists as defined in tor to vectors in Rust.
+pub trait Smartlist<T> {
+    fn get_list(&self) -> Vec<T>;
+}
+
+#[repr(C)]
+pub struct Stringlist {
+    pub list: *const *const c_char,
+    pub num_used: c_int,
+    pub capacity: c_int,
+}
+
+impl Smartlist<String> for Stringlist {
+    fn get_list(&self) -> Vec<String> {
+        let empty: Vec<String> = Vec::new();
+        let mut rust_list: Vec<String> = Vec::new();
+
+        if self.list.is_null() || self.num_used == 0 {
+            return empty;
+        }
+
+        // unsafe, as we need to extract the smartlist list into a vector of
+        // pointers, and then transform each element into a Rust string.
+        let elems: &[*const i8] =
+            unsafe { slice::from_raw_parts(self.list, self.num_used as usize) };
+
+        for elem in elems.iter() {
+            if elem.is_null() {
+                continue;
+            }
+
+            // unsafe, as we need to create a cstring from the referenced
+            // element
+            let c_string = unsafe { CStr::from_ptr(*elem) };
+
+            let r_string = match c_string.to_str() {
+                Ok(n) => n,
+                Err(_) => return empty,
+            };
+
+            rust_list.push(String::from(r_string));
+        }
+
+        rust_list
+    }
+}
+
+// TODO: CHK: this module maybe should be tested from a test in C with a
+// smartlist as defined in tor.
+#[cfg(test)]
+mod test {
+    #[test]
+    fn test_get_list_of_strings() {
+        extern crate libc;
+
+        use std::ffi::CString;
+        use libc::c_char;
+
+        use super::Smartlist;
+        use super::Stringlist;
+
+        {
+            // test to verify that null pointers are gracefully handled
+            use std::ptr;
+
+            let sl = Stringlist {
+                list: ptr::null(),
+                num_used: 0,
+                capacity: 0,
+            };
+
+            let data = sl.get_list();
+            assert_eq!(0, data.len());
+        }
+
+        {
+            let args = vec![String::from("a"), String::from("b")];
+
+            // for each string, transform  it into a CString
+            let c_strings: Vec<_> = args.iter()
+                .map(|arg| CString::new(arg.as_str()).unwrap())
+                .collect();
+
+            // then, collect a pointer for each CString
+            let p_args: Vec<_> =
+                c_strings.iter().map(|arg| arg.as_ptr()).collect();
+
+            let p: *const *const c_char = p_args.as_ptr();
+
+            // This is the representation that we expect when receiving a
+            // smartlist at the Rust/C FFI layer.
+            let sl = Stringlist {
+                list: p,
+                num_used: 2,
+                capacity: 2,
+            };
+
+            let data = sl.get_list();
+            assert_eq!("a", &data[0]);
+            assert_eq!("b", &data[1]);
+        }
+    }
+}
diff --git a/src/rust/tor_allocate/Cargo.toml b/src/rust/tor_allocate/Cargo.toml
new file mode 100644
index 0000000000..ceb08b78ab
--- /dev/null
+++ b/src/rust/tor_allocate/Cargo.toml
@@ -0,0 +1,13 @@
+[package]
+authors = ["The Tor Project"]
+version = "0.0.1"
+name = "tor_allocate"
+
+[dependencies]
+libc = "0.2.22"
+
+[lib]
+name = "tor_allocate"
+path = "lib.rs"
+crate_type = ["rlib", "staticlib"]
+
diff --git a/src/rust/tor_allocate/lib.rs b/src/rust/tor_allocate/lib.rs
new file mode 100644
index 0000000000..937a5dcf63
--- /dev/null
+++ b/src/rust/tor_allocate/lib.rs
@@ -0,0 +1,15 @@
+// Copyright (c) 2016-2017, The Tor Project, Inc. */
+// See LICENSE for licensing information */
+
+//! Allocation helper functions that allow data to be allocated in Rust
+//! using tor's specified allocator. In doing so, this can be later freed
+//! from C.
+//!
+//! This is currently a temporary solution, we will later use tor's allocator
+//! by default for any allocation that occurs in Rust. However, as this will
+//! stabalize in 2018, we can use this as a temporary measure.
+
+extern crate libc;
+
+mod tor_allocate;
+pub use tor_allocate::*;
diff --git a/src/rust/tor_allocate/tor_allocate.rs b/src/rust/tor_allocate/tor_allocate.rs
new file mode 100644
index 0000000000..8a6fabe9cb
--- /dev/null
+++ b/src/rust/tor_allocate/tor_allocate.rs
@@ -0,0 +1,101 @@
+// Copyright (c) 2016-2017, The Tor Project, Inc. */
+// See LICENSE for licensing information */
+
+use libc::{c_char, c_void};
+use std::{ptr, slice, mem};
+
+#[cfg(not(test))]
+extern "C" {
+    fn tor_malloc_(size: usize) -> *mut c_void;
+}
+
+// Defined only for tests, used for testing purposes, so that we don't need
+// to link to tor C files. Uses the system allocator
+#[cfg(test)]
+extern "C" fn tor_malloc_(size: usize) -> *mut c_void {
+    use libc::malloc;
+    unsafe { malloc(size) }
+}
+
+/// Allocate memory using tor_malloc_ and copy an existing string into the
+/// allocated buffer, returning a pointer that can later be called in C.
+///
+/// # Inputs
+///
+/// * `src`, a reference to a String.
+///
+/// # Returns
+///
+/// A `*mut c_char` that should be freed by tor_free in C
+///
+/// Allow unused unsafe as at compile-time, we get warnings that unsafe is not
+/// needed even though this calls tor_malloc in C.
+///
+#[allow(unused_unsafe)]
+pub fn allocate_and_copy_string(src: &String) -> *mut c_char {
+    let bytes: &[u8] = src.as_bytes();
+
+    let size = mem::size_of_val::<[u8]>(bytes);
+    let size_one_byte = mem::size_of::<u8>();
+
+    // handle integer overflow when adding one to the calculated length
+    let size_with_null_byte = match size.checked_add(size_one_byte) {
+        Some(n) => n,
+        None => return ptr::null_mut(),
+    };
+
+    let dest = unsafe { tor_malloc_(size_with_null_byte) as *mut u8 };
+
+    if dest.is_null() {
+        return ptr::null_mut();
+    }
+
+    unsafe { ptr::copy_nonoverlapping(bytes.as_ptr(), dest, size) };
+
+    // set the last byte as null, using the ability to index into a slice
+    // rather than doing pointer arithmatic
+    let slice = unsafe { slice::from_raw_parts_mut(dest, size_with_null_byte) };
+    slice[size] = 0; // add a null terminator
+
+    dest as *mut c_char
+}
+
+#[cfg(test)]
+mod test {
+
+    #[test]
+    fn test_allocate_and_copy_string_with_empty() {
+        use std::ffi::CStr;
+        use libc::{free, c_void};
+
+        use tor_allocate::allocate_and_copy_string;
+
+        let empty = String::new();
+        let allocated_empty = allocate_and_copy_string(&empty);
+
+        let allocated_empty_rust =
+            unsafe { CStr::from_ptr(allocated_empty).to_str().unwrap() };
+
+        assert_eq!("", allocated_empty_rust);
+
+        unsafe { free(allocated_empty as *mut c_void) };
+    }
+
+    #[test]
+    fn test_allocate_and_copy_string_with_not_empty_string() {
+        use std::ffi::CStr;
+        use libc::{free, c_void};
+
+        use tor_allocate::allocate_and_copy_string;
+
+        let empty = String::from("foo bar biz");
+        let allocated_empty = allocate_and_copy_string(&empty);
+
+        let allocated_empty_rust =
+            unsafe { CStr::from_ptr(allocated_empty).to_str().unwrap() };
+
+        assert_eq!("foo bar biz", allocated_empty_rust);
+
+        unsafe { free(allocated_empty as *mut c_void) };
+    }
+}
diff --git a/src/rust/tor_rust/Cargo.toml b/src/rust/tor_rust/Cargo.toml
new file mode 100644
index 0000000000..86fad3ee76
--- /dev/null
+++ b/src/rust/tor_rust/Cargo.toml
@@ -0,0 +1,16 @@
+[package]
+authors = ["The Tor Project"]
+name = "tor_rust"
+version = "0.1.0"
+
+[lib]
+name = "tor_rust"
+path = "lib.rs"
+crate_type = ["rlib", "staticlib"]
+
+[dependencies.tor_util]
+path = "../tor_util"
+
+[dependencies.protover]
+path = "../protover"
+
diff --git a/src/rust/tor_rust/include.am b/src/rust/tor_rust/include.am
new file mode 100644
index 0000000000..7d30592b07
--- /dev/null
+++ b/src/rust/tor_rust/include.am
@@ -0,0 +1,12 @@
+EXTRA_DIST +=\
+	src/rust/tor_rust/Cargo.toml \
+	src/rust/tor_rust/lib.rs \
+	src/rust/tor_rust/tor_rust.rs
+
+src/rust/target/release/@TOR_RUST_STATIC_NAME@: FORCE
+	( cd "$(abs_top_srcdir)/src/rust/tor_rust" ; \
+		CARGO_TARGET_DIR="$(abs_top_builddir)/src/rust/target" \
+		CARGO_HOME="$(abs_top_builddir)/src/rust" \
+		$(CARGO) build --release --quiet $(CARGO_ONLINE) )
+
+FORCE:
diff --git a/src/rust/tor_rust/lib.rs b/src/rust/tor_rust/lib.rs
new file mode 100644
index 0000000000..c1585c0480
--- /dev/null
+++ b/src/rust/tor_rust/lib.rs
@@ -0,0 +1,5 @@
+extern crate tor_util;
+extern crate protover;
+
+pub use tor_util::*;
+pub use protover::*;
diff --git a/src/rust/tor_util/Cargo.toml b/src/rust/tor_util/Cargo.toml
index f175fbdfb0..d7379a5988 100644
--- a/src/rust/tor_util/Cargo.toml
+++ b/src/rust/tor_util/Cargo.toml
@@ -8,6 +8,9 @@ name = "tor_util"
 path = "lib.rs"
 crate_type = ["rlib", "staticlib"]
 
+[dependencies.tor_allocate]
+path = "../tor_allocate"
+
 [dependencies]
-libc = "*"
+libc = "0.2.22"
 
diff --git a/src/rust/tor_util/ffi.rs b/src/rust/tor_util/ffi.rs
index af4bfc41af..76c6e6d394 100644
--- a/src/rust/tor_util/ffi.rs
+++ b/src/rust/tor_util/ffi.rs
@@ -1,56 +1,26 @@
-//! FFI functions, only to be called from C.
-//!
-//! Equivalent C versions of these live in `src/common/compat_rust.c`
-
-use std::mem::forget;
-use std::ffi::CString;
+// Copyright (c) 2016-2017, The Tor Project, Inc. */
+// See LICENSE for licensing information */
 
-use libc;
-use rust_string::RustString;
-
-/// Free the passed `RustString` (`rust_str_t` in C), to be used in place of
-/// `tor_free`().
-///
-/// # Examples
-/// ```c
-/// rust_str_t r_s = rust_welcome_string();
-/// rust_str_free(r_s);
-/// ```
-#[no_mangle]
-#[cfg_attr(feature = "cargo-clippy", allow(needless_pass_by_value))]
-pub unsafe extern "C" fn rust_str_free(_str: RustString) {
-    // Empty body: Just drop _str and we're done (Drop takes care of it).
-}
+//! FFI functions to announce Rust support during tor startup, only to be
+//! called from C.
+//!
 
-/// Lends an immutable, NUL-terminated C String.
-///
-/// # Examples
-/// ```c
-/// rust_str_t r_s = rust_welcome_string();
-/// const char *s = rust_str_get(r_s);
-/// printf("%s", s);
-/// rust_str_free(r_s);
-/// ```
-#[no_mangle]
-pub unsafe extern "C" fn rust_str_get(str: RustString) -> *const libc::c_char {
-    let res = str.as_ptr();
-    forget(str);
-    res
-}
+use libc::c_char;
+use tor_allocate::allocate_and_copy_string;
 
 /// Returns a short string to announce Rust support during startup.
 ///
 /// # Examples
 /// ```c
-/// rust_str_t r_s = rust_welcome_string();
-/// const char *s = rust_str_get(r_s);
-/// printf("%s", s);
-/// rust_str_free(r_s);
+/// char *rust_str = rust_welcome_string();
+/// printf("%s", rust_str);
+/// tor_free(rust_str);
 /// ```
 #[no_mangle]
-pub extern "C" fn rust_welcome_string() -> RustString {
-    let s = CString::new("Tor is running with Rust integration. Please report \
-                          any bugs you encouter.")
-            .unwrap();
-    RustString::from(s)
+pub extern "C" fn rust_welcome_string() -> *mut c_char {
+    let rust_welcome = String::from(
+        "Tor is running with Rust integration. Please report \
+         any bugs you encouter.",
+    );
+    allocate_and_copy_string(&rust_welcome)
 }
diff --git a/src/rust/tor_util/include.am b/src/rust/tor_util/include.am
deleted file mode 100644
index ec3898577b..0000000000
--- a/src/rust/tor_util/include.am
+++ /dev/null
@@ -1,13 +0,0 @@
-EXTRA_DIST +=\
-	src/rust/tor_util/Cargo.toml \
-	src/rust/tor_util/lib.rs \
-	src/rust/tor_util/ffi.rs \
-	src/rust/tor_util/rust_string.rs
-
-src/rust/target/release/@TOR_RUST_UTIL_STATIC_NAME@: FORCE
-	( cd "$(abs_top_srcdir)/src/rust/tor_util" ; \
-		CARGO_TARGET_DIR="$(abs_top_builddir)/src/rust/target" \
-		CARGO_HOME="$(abs_top_builddir)/src/rust" \
-		$(CARGO) build --release --quiet $(CARGO_ONLINE) )
-
-FORCE:
diff --git a/src/rust/tor_util/lib.rs b/src/rust/tor_util/lib.rs
index 79d583d1ae..42fa9d5ad0 100644
--- a/src/rust/tor_util/lib.rs
+++ b/src/rust/tor_util/lib.rs
@@ -1,13 +1,11 @@
-//! C <-> Rust compatibility helpers and types.
+// Copyright (c) 2016-2017, The Tor Project, Inc. */
+// See LICENSE for licensing information */
+
+//! Small module to announce Rust support during startup for demonstration
+//! purposes.
 //!
-//! Generically useful, small scale helpers should go here. This goes for both
-//! the C side (in the form of the ffi module) as well as the Rust side
-//! (individual modules per functionality). The corresponding C stuff lives in
-//! `src/common/compat_rust.{c,h}`.
 
 extern crate libc;
+extern crate tor_allocate;
 
-mod rust_string;
 pub mod ffi;
-
-pub use rust_string::*;
diff --git a/src/rust/tor_util/rust_string.rs b/src/rust/tor_util/rust_string.rs
deleted file mode 100644
index 46ec3fd7a8..0000000000
--- a/src/rust/tor_util/rust_string.rs
+++ /dev/null
@@ -1,101 +0,0 @@
-use std::ffi::CString;
-use std::mem::forget;
-use libc;
-
-/// Compatibility wrapper for strings allocated in Rust and passed to C.
-///
-/// Rust doesn't ensure the safety of freeing memory across an FFI boundary, so
-/// we need to take special care to ensure we're not accidentally calling
-/// `tor_free`() on any string allocated in Rust. To more easily differentiate
-/// between strings that possibly (if Rust support is enabled) were allocated
-/// in Rust, C has the `rust_str_t` helper type. The equivalent on the Rust
-/// side is `RustString`.
-///
-/// Note: This type must not be used for strings allocated in C.
-#[repr(C)]
-#[derive(Debug)]
-pub struct RustString(*mut libc::c_char);
-
-impl RustString {
-    /// Returns a pointer to the underlying NUL-terminated byte array.
-    ///
-    /// Note that this function is not typically useful for Rust callers,
-    /// except in a direct FFI context.
-    ///
-    /// # Examples
-    /// ```
-    /// # use tor_util::RustString;
-    /// use std::ffi::CString;
-    ///
-    /// let r = RustString::from(CString::new("asdf").unwrap());
-    /// let c_str = r.as_ptr();
-    /// assert_eq!(b'a', unsafe { *c_str as u8});
-    /// ```
-    pub fn as_ptr(&self) -> *const libc::c_char {
-        self.0 as *const libc::c_char
-    }
-}
-
-impl From<CString> for RustString {
-    /// Constructs a new `RustString`
-    ///
-    /// # Examples
-    /// ```
-    /// # use tor_util::RustString;
-    /// use std::ffi::CString;
-    ///
-    /// let r = RustString::from(CString::new("asdf").unwrap());
-    /// ```
-    fn from(str: CString) -> RustString {
-        RustString(str.into_raw())
-    }
-}
-
-impl Into<CString> for RustString {
-    /// Reconstructs a `CString` from this `RustString`.
-    ///
-    /// Useful to take ownership back from a `RustString` that was given to C
-    /// code.
-    ///
-    /// # Examples
-    /// ```
-    /// # use tor_util::RustString;
-    /// use std::ffi::CString;
-    ///
-    /// let cs = CString::new("asdf").unwrap();
-    /// let r = RustString::from(cs.clone());
-    /// let cs2 = r.into();
-    /// assert_eq!(cs, cs2);
-    /// ```
-    fn into(self) -> CString {
-        // Calling from_raw is always OK here: We only construct self using
-        // valid CStrings and don't expose anything that could mutate it
-        let ret = unsafe { CString::from_raw(self.0) };
-        forget(self);
-        ret
-    }
-}
-
-impl Drop for RustString {
-    fn drop(&mut self) {
-        // Don't use into() here, because we would need to move out of
-        // self. Same safety consideration. Immediately drop the created
-        // CString, which takes care of freeing the wrapped string.
-        unsafe { CString::from_raw(self.0) };
-    }
-}
-
-#[cfg(test)]
-mod test {
-    use std::mem;
-    use super::*;
-
-    use libc;
-
-    /// Ensures we're not adding overhead by using RustString.
-    #[test]
-    fn size_of() {
-        assert_eq!(mem::size_of::<*mut libc::c_char>(),
-                   mem::size_of::<RustString>())
-    }
-}
diff --git a/src/rust/tor_util/tests/rust_string.rs b/src/rust/tor_util/tests/rust_string.rs
deleted file mode 100644
index 1ff605a43c..0000000000
--- a/src/rust/tor_util/tests/rust_string.rs
+++ /dev/null
@@ -1,37 +0,0 @@
-extern crate tor_util;
-extern crate libc;
-
-use std::ffi::CString;
-use tor_util::RustString;
-
-#[test]
-fn rust_string_conversions_preserve_c_string() {
-    let s = CString::new("asdf foo").unwrap();
-    let r = RustString::from(s.clone());
-    let r2 = RustString::from(s.clone());
-    let c = r2.as_ptr();
-    assert_eq!(unsafe { libc::strlen(c) }, 8);
-    let c_str = r.into();
-    assert_eq!(s, c_str);
-}
-
-#[test]
-fn empty_string() {
-    let s = CString::new("").unwrap();
-    let r = RustString::from(s.clone());
-    let c = r.as_ptr();
-    assert_eq!(unsafe { libc::strlen(c) }, 0);
-    let c_str = r.into();
-    assert_eq!(s, c_str);
-}
-
-#[test]
-fn c_string_with_unicode() {
-    // The euro sign is three bytes
-    let s = CString::new("asd€asd").unwrap();
-    let r = RustString::from(s.clone());
-    let c = r.as_ptr();
-    assert_eq!(unsafe { libc::strlen(c) }, 9);
-    let c_str = r.into();
-    assert_eq!(s, c_str);
-}
diff --git a/src/test/include.am b/src/test/include.am
index 50cee693ab..8bfc12e9b7 100644
--- a/src/test/include.am
+++ b/src/test/include.am
@@ -150,7 +150,6 @@ src_test_test_SOURCES = \
 	src/test/test_routerkeys.c \
 	src/test/test_routerlist.c \
 	src/test/test_routerset.c \
-	src/test/test_rust.c \
 	src/test/test_scheduler.c \
 	src/test/test_shared_random.c \
 	src/test/test_socks.c \
diff --git a/src/test/test.c b/src/test/test.c
index da4f7a0553..00857c2386 100644
--- a/src/test/test.c
+++ b/src/test/test.c
@@ -1227,7 +1227,6 @@ struct testgroup_t testgroups[] = {
   { "routerkeys/", routerkeys_tests },
   { "routerlist/", routerlist_tests },
   { "routerset/" , routerset_tests },
-  { "rust/", rust_tests },
   { "scheduler/", scheduler_tests },
   { "socks/", socks_tests },
   { "shared-random/", sr_tests },
diff --git a/src/test/test.h b/src/test/test.h
index 634f3e7b02..b1a3366a80 100644
--- a/src/test/test.h
+++ b/src/test/test.h
@@ -239,7 +239,6 @@ extern struct testcase_t router_tests[];
 extern struct testcase_t routerkeys_tests[];
 extern struct testcase_t routerlist_tests[];
 extern struct testcase_t routerset_tests[];
-extern struct testcase_t rust_tests[];
 extern struct testcase_t scheduler_tests[];
 extern struct testcase_t storagedir_tests[];
 extern struct testcase_t socks_tests[];
diff --git a/src/test/test_protover.c b/src/test/test_protover.c
index 6ce54890d6..9ae907183b 100644
--- a/src/test/test_protover.c
+++ b/src/test/test_protover.c
@@ -12,6 +12,13 @@ static void
 test_protover_parse(void *arg)
 {
   (void) arg;
+#ifdef HAVE_RUST
+  /** This test is disabled on rust builds, because it only exists to test
+   * internal C functions. */
+  tt_skip();
+ done:
+  ;
+#else
   char *re_encoded = NULL;
 
   const char *orig = "Foo=1,3 Bar=3 Baz= Quux=9-12,14,15-16,900";
@@ -78,12 +85,18 @@ test_protover_parse(void *arg)
     SMARTLIST_FOREACH(elts, proto_entry_t *, ent, proto_entry_free(ent));
   smartlist_free(elts);
   tor_free(re_encoded);
+#endif
 }
 
 static void
 test_protover_parse_fail(void *arg)
 {
   (void)arg;
+#ifdef HAVE_RUST
+  /** This test is disabled on rust builds, because it only exists to test
+   * internal C functions. */
+  tt_skip();
+#else
   smartlist_t *elts;
 
   /* random junk */
@@ -109,7 +122,7 @@ test_protover_parse_fail(void *arg)
   /* Broken range */
   elts = parse_protocol_list("Link=1,9-8,3");
   tt_ptr_op(elts, OP_EQ, NULL);
-
+#endif
  done:
   ;
 }
@@ -182,6 +195,32 @@ test_protover_all_supported(void *arg)
   tor_free(msg);
 }
 
+static void
+test_protover_list_supports_protocol_returns_true(void *arg)
+{
+  (void)arg;
+
+  const char *protocols = "Link=1";
+  int is_supported = protocol_list_supports_protocol(protocols, PRT_LINK, 1);
+  tt_int_op(is_supported, OP_EQ, 1);
+
+ done:
+  ;
+}
+
+static void
+test_protover_list_supports_protocol_for_unsupported_returns_false(void *arg)
+{
+  (void)arg;
+
+  const char *protocols = "Link=1";
+  int is_supported = protocol_list_supports_protocol(protocols, PRT_LINK, 10);
+  tt_int_op(is_supported, OP_EQ, 0);
+
+ done:
+  ;
+}
+
 #define PV_TEST(name, flags)                       \
   { #name, test_protover_ ##name, (flags), NULL, NULL }
 
@@ -190,6 +229,8 @@ struct testcase_t protover_tests[] = {
   PV_TEST(parse_fail, 0),
   PV_TEST(vote, 0),
   PV_TEST(all_supported, 0),
+  PV_TEST(list_supports_protocol_for_unsupported_returns_false, 0),
+  PV_TEST(list_supports_protocol_returns_true, 0),
   END_OF_TESTCASES
 };
 
diff --git a/src/test/test_rust.c b/src/test/test_rust.c
deleted file mode 100644
index 6ad57d6fcb..0000000000
--- a/src/test/test_rust.c
+++ /dev/null
@@ -1,31 +0,0 @@
-/* Copyright (c) 2017, The Tor Project, Inc. */
-/* See LICENSE for licensing information */
-
-#include "orconfig.h"
-#include "compat_rust.h"
-#include "test.h"
-#include "util.h"
-
-static void
-test_welcome_string(void *arg)
-{
-  (void)arg;
-  rust_str_t s = rust_welcome_string();
-  const char *c_str = rust_str_get(s);
-  tt_assert(c_str);
-  size_t len = strlen(c_str);
-#ifdef HAVE_RUST
-  tt_assert(len > 0);
-#else
-  tt_assert(len == 0);
-#endif
-
- done:
-  rust_str_free(s);
-}
-
-struct testcase_t rust_tests[] = {
-  { "welcome_string", test_welcome_string, 0, NULL, NULL },
-  END_OF_TESTCASES
-};
-
diff --git a/src/test/test_rust.sh b/src/test/test_rust.sh
index d559f94ce0..50740fd18e 100755
--- a/src/test/test_rust.sh
+++ b/src/test/test_rust.sh
@@ -1,13 +1,14 @@
 #!/bin/sh
-# Test all the Rust crates we're using
+# Test all Rust crates
 
-crates=tor_util
+crates="protover tor_util smartlist tor_allocate"
 
 exitcode=0
 
 for crate in $crates; do
     cd "${abs_top_srcdir:-.}/src/rust/${crate}"
     CARGO_TARGET_DIR="${abs_top_builddir}/src/rust/target" CARGO_HOME="${abs_top_builddir}/src/rust" "${CARGO:-cargo}" test ${CARGO_ONLINE-"--frozen"} || exitcode=1
+    cd -
 done
 
 exit $exitcode