diff --git a/changes/launch_authcon_on_skew b/changes/launch_authcon_on_skew new file mode 100644 index 0000000000..276e860575 --- /dev/null +++ b/changes/launch_authcon_on_skew @@ -0,0 +1,7 @@ + o Minor features + - When we get a connection from a non-authority that tells us our + clock is skewed, and we haven't heard about clock skew (or lack + thereof) from an authority, launch a connection to an authority + so we can find out whether we're really skewed. Related to + bug 1074. Patch from "AltF4". + diff --git a/src/or/command.c b/src/or/command.c index 4b70deeef4..a13f9ec66e 100644 --- a/src/or/command.c +++ b/src/or/command.c @@ -45,6 +45,13 @@ uint64_t stats_n_destroy_cells_processed = 0; uint64_t stats_n_versions_cells_processed = 0; /** How many CELL_NETINFO cells have we received, ever? */ uint64_t stats_n_netinfo_cells_processed = 0; +/** Have we received a NETINFO cell from a trusted dir, ever? Used + * to decide what to do about time skew. + * 0 == No, and and we haven't tried asking an authority yet + * 1 == No, we've launched a query but haven't heard back yet + * 2 == Yes + **/ +static int received_netinfo_from_trusted_dir = 0; /* These are the main functions for processing cells */ static void command_process_create_cell(cell_t *cell, or_connection_t *conn); @@ -621,17 +628,16 @@ command_process_netinfo_cell(cell_t *cell, or_connection_t *conn) } /* Act on apparent skew. */ - /** Warn when we get a netinfo skew with at least this value. */ + /** Warn when we get a netinfo skew with at least this value. + Ignore if we've already received skew info from a trusted dir */ #define NETINFO_NOTICE_SKEW 3600 if (labs(apparent_skew) > NETINFO_NOTICE_SKEW && - router_get_by_id_digest(conn->identity_digest)) { + router_get_by_id_digest(conn->identity_digest) && + received_netinfo_from_trusted_dir != 2) { char dbuf[64]; - int severity; - /*XXXX be smarter about when everybody says we are skewed. */ - if (router_digest_is_trusted_dir(conn->identity_digest)) - severity = LOG_WARN; - else - severity = LOG_INFO; + + int severity = router_digest_is_trusted_dir(conn->identity_digest) ? + LOG_WARN : LOG_INFO; format_time_interval(dbuf, sizeof(dbuf), apparent_skew); log_fn(severity, LD_GENERAL, "Received NETINFO cell with skewed time from " "server at %s:%d. It seems that our clock is %s by %s, or " @@ -640,13 +646,31 @@ command_process_netinfo_cell(cell_t *cell, or_connection_t *conn) conn->_base.address, (int)conn->_base.port, apparent_skew>0 ? "ahead" : "behind", dbuf, apparent_skew>0 ? "behind" : "ahead"); - if (severity == LOG_WARN) /* only tell the controller if an authority */ + if (severity == LOG_WARN) { /* only tell the controller if an authority */ control_event_general_status(LOG_WARN, "CLOCK_SKEW SKEW=%ld SOURCE=OR:%s:%d", apparent_skew, conn->_base.address, conn->_base.port); + received_netinfo_from_trusted_dir = 2; + /* Connect to a trusted dir to trigger a NETINFO cell + * only if we haven't already */ + } else if (received_netinfo_from_trusted_dir == 0) { + routerstatus_t *any_trusted_dir = + router_pick_trusteddirserver(NO_AUTHORITY, 0); + tor_addr_t trusted_dir_addr; + tor_addr_from_ipv4h(&trusted_dir_addr, any_trusted_dir->addr); + connection_or_connect(&trusted_dir_addr, + any_trusted_dir->or_port, + any_trusted_dir->identity_digest); + received_netinfo_from_trusted_dir = 1; + } } + /* Note that we received a good netinfo cell from a trusted directory */ + if (router_digest_is_trusted_dir(conn->identity_digest) && + labs(apparent_skew) <= NETINFO_NOTICE_SKEW) + received_netinfo_from_trusted_dir = 2; + /* XXX maybe act on my_apparent_addr, if the source is sufficiently * trustworthy. */