[uac_registrant] store the configured "expires" and use it for each re-REGISTER

...in order to avoid decreasing it if the registar is reducing it.
Reported by @sindy39
Fixes #3659

Author: bogdan-iancu

modules/uac_registrant/reg_records.c

@@ -89,12 +89,13 @@ int reg_build_sr_identifier(const str *aor, const str *contact,
 }
 
 void reg_print_record(reg_record_t *rec) {
-	LM_DBG("checking uac=[%p] state=[%d][%.*s] expires=[%d]"
+	LM_DBG("checking uac=[%p] state=[%d][%.*s] expires=[%d/%d]"
 			" last_register_sent=[%d] registration_timeout=[%d]"
 			" auth_user[%p][%d]->[%.*s] auth_password=[%p][%d]->[%.*s]"
 			" sock=[%p] clustering=[%.*s/%d] enabled=[%s]\n",
 		rec, rec->state,
-		uac_reg_state[rec->state].len, uac_reg_state[rec->state].s, rec->expires,
+		uac_reg_state[rec->state].len, uac_reg_state[rec->state].s,
+		rec->expires, rec->wanted_expires,
 		(unsigned int)rec->last_register_sent, (unsigned int)rec->registration_timeout,
 		rec->auth_user.s, rec->auth_user.len, rec->auth_user.len, rec->auth_user.s,
 		rec->auth_password.s, rec->auth_password.len,
@@ -244,6 +245,7 @@ int add_record(uac_reg_map_t *uac, str *now, unsigned int mode,
 
 	memset(record, 0, size);
 
+	record->wanted_expires = uac->expires;
 	record->expires = uac->expires;
 
 	td = &(record->td);

modules/uac_registrant/reg_records.h

@@ -84,6 +84,7 @@ typedef struct reg_record {
 	str auth_user;
 	str auth_password;
 	unsigned int state;
+	unsigned int wanted_expires;
 	unsigned int expires;
 	time_t last_register_sent;
 	time_t registration_timeout;

modules/uac_registrant/registrant.c

@@ -831,7 +831,7 @@ int send_register(unsigned int hash_index, reg_record_t *rec, str *auth_hdr)
 	cb_param->uac = rec;
 
 	/* get the string version of expires */
-	expires = int2str((unsigned long)(rec->expires), &expires_len);
+	expires = int2str((unsigned long)(rec->wanted_expires), &expires_len);
 
 	p = extra_hdrs.s;
 	memcpy(p, contact_hdr.s, contact_hdr.len);