[OpenSER-Devel] concurrency issues in lcr

[Dan Pascu]

This line in reload_gws() is not atomic:

    (*lcrs_ws_reload_counter)++;

An atomic counter should be used for that, otherwise the value of 
lcrs_ws_reload_counter may end up with the wrong value if 2 concurrent 
processes modify it in a narrow time window.

The same is true for the lines above that:

    if (*lcrs == lcrs_1) {
	lcrs_2[i].end_record = 1;
	*lcrs = lcrs_2;
    } else {
	lcrs_1[i].end_record = 1;
	*lcrs = lcrs_1;
    }

and the similar lines for gateways:

    if (*gws == gws_1) {
	gws_2[i].ip_addr = 0;
	*gws = gws_2;
    } else {
	gws_1[i].ip_addr = 0;
	*gws = gws_1;
    }

Without locking the wrong table pointer could end up in lcrs and gws, or 
even worse, mixed lcr and gw table pointers. The whole lcr reload 
mechanism is very fragile in this regard if concurrent lcr_reload 
commands arrive in narrow time intervals, even though it appears to make 
provisions to be able to do 2 reloads in a narrow time window.

IMO all 3 operations presented above should be done together under a lock.

Even better a more robust reload mechanism should be implemented, because 
it's very difficult to prevent a provisioning system from issuing the 
reload lcr command multiple times when the provisioning interface allows 
concurrent access to its resources.

-- 
Dan