Add a lockfile to the Tor data directory to avoid situations where two Tors start with the same datadir, or where a --list-fingerprints races with a server to create keys, or such.

svn:r16722

1 files changed, 11 insertions, 0 deletions

diff --git a/src/or/router.c b/src/or/router.c
index 842cb7b52a..4c85a7b2ab 100644
--- a/src/or/router.c
+++ b/src/or/router.c
@@ -235,6 +235,17 @@ init_key_from_file(const char *fname, int generate, int severity)
       goto error;
     case FN_NOENT:
       if (generate) {
+        if (!have_lockfile()) {
+          if (try_locking(get_options(), 0)<0) {
+            /* Make sure that --list-fingerprint only creates new keys
+             * if there is no possibility for a deadlock. */
+            log(severity, LD_FS, "Another Tor process has locked \"%s\". Not "
+                "writing any new keys.", fname);
+            /*XXXX The 'other process' might make a key in a second or two;
+             * maybe we should wait for it. */
+            goto error;
+          }
+        }
         log_info(LD_GENERAL, "No key found in \"%s\"; generating fresh key.",
                  fname);
         if (crypto_pk_generate_key(prkey)) {