sip-in hold/retr error handling: simply send BYE Because we know that the SIP state is CONNECTED at the time of any such error event, we can call initiate_bye() instead of disconnect_sip(), and thereby get rid of struct gsm_mncc_cause which will never be used in this scenario anyway.

/*
 * Here we define the structure used to capture the result
 * of From header field parsing.
 */

struct grok_from {
	char		*uri;
	unsigned	uri_len;
	char		*user;
	unsigned	user_len;
	char		*cnam;
	unsigned	cnam_len;
	int		cnam_quoted;
};