Did ares_set_servers_csv() return ARES_EBADSTR as it should?  It does appear when it does that, it leaves the channel in a "bad" state since existing servers are cleared before parse. I'm not sure of any other instances where a channel might have no servers, as even in the case where it can't determine one from configuration, it uses a localhost fallback.  It may make more sense to kill the ares__destroy_servers_state()  call at the beginning of set_servers_csv(), since ares_set_servers_ports() clears it which gets called after a successful parse.

I'd agree that there should probably be a sanity check in ares_send() to not try an invalid ares_malloc(), ARES_ESERVFAIL would be as good an error condition as any in this case.

On 3/9/18 7:07 PM, Francisco Sedano Crippa (fsedanoc) wrote:


I noticed today if you pass a string with spaces to set_servers_csv, like:

" ,"

It will take the first server as " " (note the space), it will notice it's not a valid IP and fail. So far so good.

However, nservers for the channel will stay set to -1, so when ares_send is 
called, this will be executed:

  query->server_info = ares_malloc(channel->nservers *

The negative value will be misinterpreted to a huge number since argument is size_t and we agree things smell really bad from here. In practice, such a mem allocation fails and we return ENOMEM (which is also misleading), but it's a very incorrect behaviour.

I was thinking on just adding a check at the beginning of ares_send() to exit if 
nservers is <= 0.

Do you guys agree with the approach? If that’s the case, which error do you suggest to return? No one really matches, I’d say ARES_ENOTFOUND, but that implies we tried to contact the server…


*. .:|:.:|:. _Francisco Sedano_ | CCIE 14859, Tech Lead Software Engineering | CSG Enterprise Access and Services Group (EASG)*

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