tls: add a mutual authentication test

Also, make it clearer that TLS keys and certificates can only
be set once on a configuration.  (mbedTLS makes this confusing!)

This mutual test is only fully validated on mbed, because wolfSSL
seems to not properly validate this in many configurations.

1 files changed, 3 insertions, 5 deletions

diff --git a/docs/man/nng_tls_config_own_cert.3tls.adoc b/docs/man/nng_tls_config_own_cert.3tls.adoc
index 66027305..814bc94c 100644
--- a/docs/man/nng_tls_config_own_cert.3tls.adoc
+++ b/docs/man/nng_tls_config_own_cert.3tls.adoc
@@ -18,7 +18,6 @@ nng_tls_config_own_cert - configure own certificate and key
 [source, c]
 ----
 #include <nng/nng.h>
-#include <nng/supplemental/tls/tls.h>
 
 int nng_tls_config_own_cert(nng_tls_config *cfg, const char *cert,
     const char *key, const char *pass);
@@ -38,10 +37,9 @@ have it, and will have to in order to validate this certificate anyway).
 The _key_ may be encrypted with a password, in which can be supplied in _pass_.
 The value `NULL` should be supplied for _pass_ if the key is not encrypted.
 
-On servers, it is possible to call this function multiple times for the
-same configuration.
-This can be useful for specifying different parameters
-to be used for different cryptographic algorithms.
+This cannot be called more than once for a given TLS configuration.
+(Earlier versions of NNG allowed this, but it was never used, brittle,
+and the source of confusion.)
 
 The certificate located in _cert_ and _key_ must be NUL (`\0`) terminated C
 strings containing