Add postfork support for nss

We need this in our unit tests, since otherwise NSS will notice
we've forked and start cussing us out.

I suspect we'll need a different hack for daemonizing, but this
should be enough for tinytest to work.

src/ext/tinytest.c

@@ -25,6 +25,7 @@
 #ifdef TINYTEST_LOCAL
 #include "tinytest_local.h"
 #endif
+#define TINYTEST_POSTFORK
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -118,6 +119,12 @@ testcase_run_bare_(const struct testcase_t *testcase)
 
 #ifndef NO_FORKING
 
+#ifdef TINYTEST_POSTFORK
+void tinytest_postfork(void);
+#else
+static void tinytest_postfork(void) { }
+#endif
+
 static enum outcome
 testcase_run_forked_(const struct testgroup_t *group,
 		     const struct testcase_t *testcase)
@@ -187,6 +194,7 @@ testcase_run_forked_(const struct testgroup_t *group,
 		int test_r, write_r;
 		char b[1];
 		close(outcome_pipe[0]);
+		tinytest_postfork();
 		test_r = testcase_run_bare_(testcase);
 		assert(0<=(int)test_r && (int)test_r<=2);
 		b[0] = "NYS"[test_r];

src/lib/crypt_ops/crypto_init.c

@@ -127,3 +127,13 @@ crypto_global_cleanup(void)
 
   return 0;
 }
+
+/** Run operations that the crypto library requires to be happy again
+ * after forking. */
+void
+crypto_postfork(void)
+{
+#ifdef ENABLE_NSS
+  crypto_nss_postfork();
+#endif
+}

src/lib/crypt_ops/crypto_init.h

@@ -24,5 +24,6 @@ int crypto_global_init(int hardwareAccel,
 
 void crypto_thread_cleanup(void);
 int crypto_global_cleanup(void);
+void crypto_postfork(void);
 
 #endif /* !defined(TOR_CRYPTO_H) */

src/lib/crypt_ops/crypto_nss_mgt.c

@@ -93,3 +93,10 @@ crypto_nss_global_cleanup(void)
 {
   NSS_Shutdown();
 }
+
+void
+crypto_nss_postfork(void)
+{
+  crypto_nss_global_cleanup();
+  crypto_nss_early_init();
+}

src/lib/crypt_ops/crypto_nss_mgt.h

@@ -26,6 +26,8 @@ void crypto_nss_early_init(void);
 int crypto_nss_late_init(void);
 
 void crypto_nss_global_cleanup(void);
+
+void crypto_nss_postfork(void);
 #endif
 
 #endif /* !defined(TOR_CRYPTO_NSS_H) */

src/test/testing_common.c

@@ -223,6 +223,13 @@ an_assertion_failed(void)
   tinytest_set_test_failed_();
 }
 
+void tinytest_postfork(void);
+void
+tinytest_postfork(void)
+{
+  crypto_postfork();
+}
+
 /** Main entry point for unit test code: parse the command line, and run
  * some unit tests. */
 int