s_server: Properly indicate ALPN protocol mismatch
Return SSL_TLSEXT_ERR_ALERT_FATAL from alpn_select_cb so that
an alert is sent to the client on ALPN protocol mismatch.
Fixes:
@@ -707,7 +707,7 @@ static int alpn_cb(SSL *s, const unsigned char **out, unsigned char *outlen,
if (SSL_select_next_proto
((unsigned char **)out, outlen, alpn_ctx->data, alpn_ctx->len, in,
inlen) != OPENSSL_NPN_NEGOTIATED) {
- return SSL_TLSEXT_ERR_NOACK;
+ return SSL_TLSEXT_ERR_ALERT_FATAL;
}
if (!s_quiet) {
