[tor-commits] [tor/master] addr: New find_my_address() to support multiple address families
dgoulet at torproject.org
dgoulet at torproject.org
Wed Jun 24 17:58:40 UTC 2020
commit 9e85056de9ffe4858e2a07a5fd5e5fd4d144e688
Author: David Goulet <dgoulet at torproject.org>
Date: Thu Jun 18 13:39:20 2020 -0400
addr: New find_my_address() to support multiple address families
resolve_my_address() was beyond repair in terms of refactoring. Way too
complex and doing too many things.
This commit implements find_my_address() which in theory does the same as
resolve_my_address() but in a more clean, concise and modern way using the
tor_addr_t interface and for multiple address family.
The caller needs to pass the address family (IPv4 or IPv6) which this
interface supports. For both, a last resolved cache is used as well.
Implements #33233
Signed-off-by: David Goulet <dgoulet at torproject.org>
---
src/app/config/resolve_addr.c | 490 ++++++++++++++++++++++++++++++++++++++++++
src/app/config/resolve_addr.h | 4 +
2 files changed, 494 insertions(+)
diff --git a/src/app/config/resolve_addr.c b/src/app/config/resolve_addr.c
index 6b66a7100..5cabb5889 100644
--- a/src/app/config/resolve_addr.c
+++ b/src/app/config/resolve_addr.c
@@ -19,6 +19,31 @@
#include "lib/net/gethostname.h"
#include "lib/net/resolve.h"
+/** Maximum "Address" statement allowed in our configuration. */
+#define MAX_CONFIG_ADDRESS 2
+
+/** Errors use when finding our IP address. Some are transient and some are
+ * persistent, just attach semantic to the values. They are all negative so
+ * one can do a catch all. */
+
+#define ERR_FAIL_RESOLVE -1 /* Hostname resolution failed. */
+#define ERR_GET_HOSTNAME -2 /* Unable to get local hostname. */
+#define ERR_NO_OPT_ADDRESS -3 /* No Address in config. */
+#define ERR_TOO_MANY_ADDRESS -4 /* Too many Address for one family. */
+#define ERR_GET_INTERFACE -5 /* Unable to query network interface. */
+#define ERR_UNUSABLE_ADDRESS -6 /* Unusable address. It is internal. */
+#define ERR_DEFAULT_DIRAUTH -7 /* Using default authorities. */
+#define ERR_ADDRESS_IS_INTERNAL -8 /* IP is internal. */
+
+/** Ease our life. Arrays containing state per address family. These are to
+ * add semantic to the code so we know what is accessed. */
+#define IDX_IPV4 0 /* Index to AF_INET. */
+#define IDX_IPV6 1 /* Index to AF_INET6. */
+#define IDX_SIZE 2 /* How many indexes do we have. */
+
+/** Last resolved addresses. */
+static tor_addr_t last_resolved_addrs[IDX_SIZE];
+
/** Last value actually set by resolve_my_address. */
static uint32_t last_resolved_addr_v4 = 0;
@@ -36,6 +61,471 @@ reset_last_resolved_addr_v4(void)
last_resolved_addr_v4 = 0;
}
+/** @brief Return true iff the given IP address can be used as a valid
+ * external resolved address.
+ *
+ * Two tests are done in this function:
+ * 1) If the address if NOT internal, it can be used.
+ * 2) If the address is internal and we have custom directory authorities
+ * configured then it can they be used. Important for testing networks.
+ *
+ * @param addr The IP address to validate.
+ * @param options Global configuration options.
+ * @param warn_severity Log level that should be used on error.
+ * @param explicit_ip Was the IP address explicitly given.
+ *
+ * @return Return 0 if it can be used. Return error code ERR_* found at the
+ * top of the file.
+ */
+static int
+address_can_be_used(const tor_addr_t *addr, const or_options_t *options,
+ int warn_severity, const bool explicit_ip)
+{
+ tor_assert(addr);
+
+ /* Public address, this is fine. */
+ if (!tor_addr_is_internal(addr, 0)) {
+ goto allow;
+ }
+
+ /* We have a private IP address. It is allowed only if we set custom
+ * directory authorities. */
+ if (using_default_dir_authorities(options)) {
+ log_fn(warn_severity, LD_CONFIG,
+ "Address '%s' is a private IP address. Tor relays that use "
+ "the default DirAuthorities must have public IP addresses.",
+ fmt_addr(addr));
+ return ERR_DEFAULT_DIRAUTH;
+ }
+
+ if (!explicit_ip) {
+ /* Even with custom directory authorities, only an explicit internal
+ * address is accepted. */
+ log_fn(warn_severity, LD_CONFIG,
+ "Address %s was resolved and thus not explicitly "
+ "set. Even if DirAuthorities are custom, this is "
+ "not allowed.", fmt_addr(addr));
+ return ERR_ADDRESS_IS_INTERNAL;
+ }
+
+ allow:
+ return 0;
+}
+
+/** @brief Get IP address from the given config line and for a specific address
+ * family.
+ *
+ * This can fail is more than two Address statement are found for the same
+ * address family. It also fails if no statement is found.
+ *
+ * On failure, no out parameters should be used or considered valid.
+ *
+ * @param options Global configuration options.
+ * @param warn_severity Log level that should be used on error.
+ * @param family IP address family. Only AF_INET and AF_INET6 are supported.
+ * @param method_out OUT: String denoting by which method the address was
+ * found. This is described in the control-spec.txt as
+ * actions for "STATUS_SERVER".
+ * @param hostname_out OUT: String containing the hostname gotten from the
+ * Address value if any.
+ * @param addr_out OUT: Tor address of the address found in the cline or
+ * resolved from the cline.
+ *
+ * @return Return 0 on success that is an address has been found or resolved
+ * successfully. Return error code ERR_* found at the top of the file.
+ */
+static int
+get_address_from_config(const or_options_t *options, int warn_severity,
+ int family, const char **method_out,
+ char **hostname_out, tor_addr_t *addr_out)
+{
+ bool explicit_ip = false;
+ int num_valid_addr = 0;
+
+ tor_assert(options);
+ tor_assert(addr_out);
+ tor_assert(method_out);
+ tor_assert(hostname_out);
+
+ log_debug(LD_CONFIG, "Attempting to get address from configuration");
+
+ if (!options->Address) {
+ log_info(LD_CONFIG, "No Address option found in configuration.");
+ return ERR_NO_OPT_ADDRESS;
+ }
+
+ for (const config_line_t *cfg = options->Address; cfg != NULL;
+ cfg = cfg->next) {
+ int af;
+ tor_addr_t addr;
+
+ af = tor_addr_parse(&addr, cfg->value);
+ if (af == family) {
+ tor_addr_copy(addr_out, &addr);
+ *method_out = "CONFIGURED";
+ explicit_ip = true;
+ num_valid_addr++;
+ continue;
+ }
+
+ /* Not an IP address. Considering this value a hostname and attempting to
+ * do a DNS lookup. */
+ if (!tor_addr_lookup(cfg->value, family, &addr)) {
+ tor_addr_copy(addr_out, &addr);
+ *method_out = "RESOLVED";
+ *hostname_out = tor_strdup(cfg->value);
+ explicit_ip = false;
+ num_valid_addr++;
+ continue;
+ } else {
+ /* If we have hostname we are unable to resolve, it is an persistent
+ * error and thus we stop right away. */
+ log_fn(warn_severity, LD_CONFIG,
+ "Could not resolve local Address '%s'. Failing.", cfg->value);
+ return ERR_FAIL_RESOLVE;
+ }
+ }
+
+ if (!num_valid_addr) {
+ log_fn(warn_severity, LD_CONFIG,
+ "No Address option found for family %s in configuration.",
+ fmt_af_family(family));
+ return ERR_NO_OPT_ADDRESS;
+ }
+
+ if (num_valid_addr >= MAX_CONFIG_ADDRESS) {
+ log_fn(warn_severity, LD_CONFIG,
+ "Found %d Address statement of address family %s. "
+ "Only one is allowed.", num_valid_addr, fmt_af_family(family));
+ return ERR_TOO_MANY_ADDRESS;
+ }
+
+ /* Great, we found an address. */
+ return address_can_be_used(addr_out, options, warn_severity, explicit_ip);
+}
+
+/** @brief Get IP address from the local hostname by calling gethostbyname()
+ * and doing a DNS resolution on the hostname.
+ *
+ * On failure, no out parameters should be used or considered valid.
+ *
+ * @param options Global configuration options.
+ * @param warn_severity Log level that should be used on error.
+ * @param family IP address family. Only AF_INET and AF_INET6 are supported.
+ * @param method_out OUT: String denoting by which method the address was
+ * found. This is described in the control-spec.txt as
+ * actions for "STATUS_SERVER".
+ * @param hostname_out OUT: String containing the local hostname.
+ * @param addr_out OUT: Tor address resolved from the local hostname.
+ *
+ * @return Return 0 on success that is an address has been found and resolved
+ * successfully. Return error code ERR_* found at the top of the file.
+ */
+static int
+get_address_from_hostname(const or_options_t *options, int warn_severity,
+ int family, const char **method_out,
+ char **hostname_out, tor_addr_t *addr_out)
+{
+ int ret;
+ char hostname[256];
+
+ tor_assert(addr_out);
+ tor_assert(method_out);
+
+ log_debug(LD_CONFIG, "Attempting to get address from local hostname");
+
+ if (tor_gethostname(hostname, sizeof(hostname)) < 0) {
+ log_fn(warn_severity, LD_NET, "Error obtaining local hostname");
+ return ERR_GET_HOSTNAME;
+ }
+ if (tor_addr_lookup(hostname, family, addr_out)) {
+ log_fn(warn_severity, LD_NET,
+ "Could not resolve local hostname '%s'. Failing.", hostname);
+ return ERR_FAIL_RESOLVE;
+ }
+
+ ret = address_can_be_used(addr_out, options, warn_severity, false);
+ if (ret < 0) {
+ return ret;
+ }
+
+ /* addr_out contains the address of the local hostname. */
+ *method_out = "GETHOSTNAME";
+ *hostname_out = tor_strdup(hostname);
+
+ return 0;
+}
+
+/** @brief Get IP address from a network interface.
+ *
+ * On failure, no out parameters should be used or considered valid.
+ *
+ * @param options Global configuration options.
+ * @param warn_severity Log level that should be used on error.
+ * @param family IP address family. Only AF_INET and AF_INET6 are supported.
+ * @param method_out OUT: Always "INTERFACE" on success which is detailed in
+ * the control-spec.txt as actions for "STATUS_SERVER".
+ * @param addr_out OUT: Tor address found attached to the interface.
+ *
+ * @return Return 0 on success that is an address has been found. Return
+ * error code ERR_* found at the top of the file.
+ */
+static int
+get_address_from_interface(const or_options_t *options, int warn_severity,
+ int family, const char **method_out,
+ tor_addr_t *addr_out)
+{
+ int ret;
+
+ tor_assert(method_out);
+ tor_assert(addr_out);
+
+ log_debug(LD_CONFIG, "Attempting to get address from network interface");
+
+ if (get_interface_address6(warn_severity, family, addr_out) < 0) {
+ log_fn(warn_severity, LD_CONFIG,
+ "Could not get local interface IP address.");
+ return ERR_GET_INTERFACE;
+ }
+
+ ret = address_can_be_used(addr_out, options, warn_severity, false);
+ if (ret < 0) {
+ return ret;
+ }
+
+ *method_out = "INTERFACE";
+
+ return 0;
+}
+
+/** @brief Update the last resolved address cache using the given address.
+ *
+ * A log notice is emitted if the given address has changed from before. Not
+ * emitted on first resolve.
+ *
+ * Control port event "STATUS_SERVER" is emitted with the new information if
+ * it has changed.
+ *
+ * Finally, tor is notified that the IP address has changed.
+ *
+ * @param addr IP address to update the cache with.
+ * @param method_used By which method did we resolved it (for logging and
+ * control port).
+ * @param hostname_used Which hostname was used. If none were used, it is an
+ * empty string. (for logging and control port).
+ */
+static void
+update_resolved_cache(const tor_addr_t *addr, const char *method_used,
+ const char *hostname_used)
+{
+ /** Have we done a first resolve. This is used to control logging. */
+ static bool have_resolved_once[IDX_SIZE] = { false, false };
+ bool *done_one_resolve;
+ bool have_hostname = false;
+ tor_addr_t *last_resolved;
+
+ tor_assert(addr);
+ tor_assert(method_used);
+ tor_assert(hostname_used);
+
+ /* Do we have an hostname. */
+ have_hostname = strlen(hostname_used) > 0;
+
+ switch (tor_addr_family(addr)) {
+ case AF_INET:
+ done_one_resolve = &have_resolved_once[IDX_IPV4];
+ last_resolved = &last_resolved_addrs[IDX_IPV4];
+ break;
+ case AF_INET6:
+ done_one_resolve = &have_resolved_once[IDX_IPV6];
+ last_resolved = &last_resolved_addrs[IDX_IPV6];
+ break;
+ default:
+ tor_assert_nonfatal_unreached();
+ return;
+ }
+
+ /* Same address last resolved. Ignore. */
+ if (tor_addr_eq(last_resolved, addr)) {
+ return;
+ }
+
+ /* Don't log notice if this is the first resolve we do. */
+ if (*done_one_resolve) {
+ /* Leave this as a notice, regardless of the requested severity,
+ * at least until dynamic IP address support becomes bulletproof. */
+ log_notice(LD_NET,
+ "Your IP address seems to have changed to %s "
+ "(METHOD=%s%s%s). Updating.",
+ fmt_addr(addr), method_used,
+ have_hostname ? " HOSTNAME=" : "",
+ have_hostname ? hostname_used : "");
+ ip_address_changed(0);
+ }
+
+ /* Notify control port. */
+ control_event_server_status(LOG_NOTICE,
+ "EXTERNAL_ADDRESS ADDRESS=%s METHOD=%s%s%s",
+ fmt_addr(addr), method_used,
+ have_hostname ? " HOSTNAME=" : "",
+ have_hostname ? hostname_used : "");
+ /* Copy address to cache. */
+ tor_addr_copy(last_resolved, addr);
+ *done_one_resolve = true;
+}
+
+/** @brief Attempt to find our IP address that can be used as our external
+ * reachable address.
+ *
+ * The following describe the algorithm to find an address. Each have
+ * specific conditions so read carefully.
+ *
+ * On success, true is returned and depending on how the address was found,
+ * the out parameters can have different values.
+ *
+ * On error, false is returned and all out parameters are untouched.
+ *
+ * 1. Look at the configuration Address option.
+
+ * If Address is a public address, True is returned and addr_out is set
+ * with it, the method_out is set to "CONFIGURED" and hostname_out is set
+ * to NULL.
+ *
+ * If Address is an internal address but NO custom authorities are used,
+ * an error is returned.
+ *
+ * If Address is a hostname, that is it can't be converted to an address,
+ * it is resolved. On success, addr_out is set with the address,
+ * method_out is set to "RESOLVED" and hostname_out is set to the resolved
+ * hostname. On failure to resolve, an error is returned.
+ *
+ * If no given Address, fallback to the local hostname (see section 2).
+ *
+ * 2. Look at the local hostname.
+ *
+ * If the local hostname resolves to a non internal address, addr_out is
+ * set with it, method_out is set to "GETHOSTNAME" and hostname_out is set
+ * to the resolved hostname.
+ *
+ * If a local hostname can NOT be found, an error is returned.
+ *
+ * If the local hostname resolves to an internal address, an error is
+ * returned.
+ *
+ * If the local hostname can NOT be resolved, fallback to the network
+ * interface (see section 3).
+ *
+ * 3. Look at the network interface.
+ *
+ * Attempt to find the first public usable address from the list of
+ * network interface returned by the OS.
+ *
+ * On failure, an error is returned. This error indicates that all
+ * attempts have failed and thus the address for the given family can not
+ * be found.
+ *
+ * On success, addr_out is set with it, method_out is set to "INTERFACE"
+ * and hostname_out is set to NULL.
+ *
+ * @param options Global configuration options.
+ * @param family IP address family. Only AF_INET and AF_INET6 are supported.
+ * @param warn_severity Logging level.
+ * @param addr_out OUT: Set with the IP address found if any.
+ * @param method_out OUT: (optional) String denoting by which method the
+ * address was found. This is described in the
+ * control-spec.txt as actions for "STATUS_SERVER".
+ * @param hostname_out OUT: String containing the hostname if any was used.
+ * Only be set for "RESOLVED" and "GETHOSTNAME" methods.
+ * Else it is set to NULL.
+ *
+ * @return True if the address was found for the given family. False if not or
+ * on errors.
+ */
+bool
+find_my_address(const or_options_t *options, int family, int warn_severity,
+ tor_addr_t *addr_out, const char **method_out,
+ char **hostname_out)
+{
+ int ret;
+ const char *method_used;
+ char *hostname_used = tor_strdup("");
+ tor_addr_t my_addr;
+
+ tor_assert(options);
+ tor_assert(addr_out);
+
+ /*
+ * Step 1: Discover address by attempting 3 different methods consecutively.
+ */
+
+ /* Attempt #1: Get address from configuration. */
+ ret = get_address_from_config(options, warn_severity, family, &method_used,
+ &hostname_used, &my_addr);
+ if (ret == 0) {
+ log_fn(warn_severity, LD_CONFIG, "Address found in configuration: %s",
+ fmt_addr(&my_addr));
+ } else {
+ /* Unable to resolve an Address statement is a failure. Also, using
+ * default dirauth error means that the configured address is internal
+ * which is only accepted if custom authorities are used. */
+ if (ret == ERR_FAIL_RESOLVE || ret == ERR_DEFAULT_DIRAUTH) {
+ return false;
+ }
+
+ /* Attempt #2: Get local hostname and resolve it. */
+ ret = get_address_from_hostname(options, warn_severity, family,
+ &method_used, &hostname_used, &my_addr);
+ if (ret == 0) {
+ log_fn(warn_severity, LD_CONFIG, "Address found from local hostname: "
+ "%s", fmt_addr(&my_addr));
+ } else if (ret < 0) {
+ /* Unable to get the hostname results in a failure. If the address is
+ * internal, we stop right away. */
+ if (ret == ERR_GET_HOSTNAME || ret == ERR_ADDRESS_IS_INTERNAL) {
+ return false;
+ }
+
+ /* Attempt #3: Get address from interface. */
+ ret = get_address_from_interface(options, warn_severity, family,
+ &method_used, &my_addr);
+ if (ret == 0) {
+ log_fn(warn_severity, LD_CONFIG, "Address found from interface: %s",
+ fmt_addr(&my_addr));
+ } else {
+ /* We've exhausted our attempts. Failure. */
+ log_fn(warn_severity, LD_CONFIG, "Unable to find our IP address.");
+ return false;
+ }
+ }
+ }
+ tor_assert(method_used);
+
+ /* From here, my_addr is a valid IP address of "family" and can be used as
+ * our external IP address. */
+
+ /*
+ * Step 2: Update last resolved address cache and inform the control port.
+ */
+ update_resolved_cache(&my_addr, method_used, hostname_used);
+
+ if (method_out) {
+ *method_out = method_used;
+ }
+ if (hostname_out) {
+ *hostname_out = NULL;
+ if (strlen(hostname_used) > 0) {
+ *hostname_out = hostname_used;
+ } else {
+ tor_free(hostname_used);
+ }
+ } else {
+ tor_free(hostname_used);
+ }
+
+ tor_addr_copy(addr_out, &my_addr);
+ return true;
+}
+
/**
* Attempt getting our non-local (as judged by tor_addr_is_internal()
* function) IP address using following techniques, listed in
diff --git a/src/app/config/resolve_addr.h b/src/app/config/resolve_addr.h
index 6c94fe06b..2cd27d170 100644
--- a/src/app/config/resolve_addr.h
+++ b/src/app/config/resolve_addr.h
@@ -15,6 +15,10 @@ int resolve_my_address_v4(int warn_severity, const or_options_t *options,
uint32_t *addr_out,
const char **method_out, char **hostname_out);
+bool find_my_address(const or_options_t *options, int family,
+ int warn_severity, tor_addr_t *addr_out,
+ const char **method_out, char **hostname_out);
+
uint32_t get_last_resolved_addr_v4(void);
void reset_last_resolved_addr_v4(void);
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