The request() function in re/src/sip/request.c fails with EINVAL when sending stateless requests (for example ACKs) to a TLS server, which makes SIP calls terminate.

This is because request() calls sip_send_conn() which always passes a NULL host to sip_transp_send(). This gets passed down to conn_send() in re/src/sip/transp.c and ultimately to tls_set_verify_server() which fails with EINVAL.

I patched this in #42