Hi folks. Yes, ares_set_servers_csv() returned what it should. It’s just the behavior afterwards which is not correct. I’ll submit PR for adding this check, thanks.
. .:|:.:|:. Francisco Sedano | CCIE 14859, Tech Lead Software Engineering | CSG Enterprise Access and Services Group (EASG) From: c-ares <c-ares-boun...@cool.haxx.se> on behalf of David Drysdale <drysd...@google.com> Reply-To: c-ares hacking <c-ares@cool.haxx.se> Date: Sunday, 11 March 2018 at 08:29 To: c-ares hacking <c-ares@cool.haxx.se> Subject: Re: Wrong handling on badly formatted strings passed to set_servers_csv On Sat, Mar 10, 2018 at 1:03 PM, Brad House <b...@mainstreetsoftworks.com<mailto:b...@mainstreetsoftworks.com>> wrote: Did ares_set_servers_csv() return ARES_EBADSTR as it should? There's a test that implies that it will: https://github.com/c-ares/c-ares/blob/master/test/ares-test-misc.cc#L86-L88 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. +1 -Brad On 3/9/18 7:07 PM, Francisco Sedano Crippa (fsedanoc) wrote: Hello, I noticed today if you pass a string with spaces to set_servers_csv, like: "127.0.0.1 , 200.0.0.1" It will take the first server as "127.0.0.1 " (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 * sizeof(query->server_info[0])); 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… Thanks! . .:|:.:|:. Francisco Sedano | CCIE 14859, Tech Lead Software Engineering | CSG Enterprise Access and Services Group (EASG)
