GIT blame tells me I made that change on July 6, 2011. Though I could not reproduce the issue myself, it was reported for BOINC Version 6.10.58 in TRAC ticket #1041 on 27 Jan 2011 <http://boinc.berkeley.edu/trac/ticket/1041>, with c-ares version 1.6.0 and curl version 7.21.2.
AT&T U-Verse stopped installing those 2-Wire routers some time ago, though there undoubtedly still are some in use (mine was replaced only quite recently), and I commented in the TRAC ticket that it might be possible to work around the problem by configuring the Mac's Internet settings to use an external DNS server instead of the one built into the router. We are currently using c-ares 1.11.0 and curl 7.50.2 on the Mac, The latest versions are c-ares 1.13.0 and curl 7.55.1. So it is quite likely that this was fixed in c-ares and curl some time ago. But the issue goes back even further. On December 13, 2010 I wrote: > As you may recall, I dropped back from c-ares version 1.7.0 to version 1.6.0 > in April (BOINC 6.10.45) to work around the "Can't resolve host name" > problem. The issue was that c-ares tried to resolve the DNS via IPv6, but > did not automatically retry with IPv4 when that failed under certain > circumstances. IPv6 support was added to c-ares version 1.7.0, so reverting > to c-ares 1.6.0 effectively eliminated IPv6 support from cURL. > > I'm subscribed to the c-ares developer email listserv, and a recent posting > gave me enough information that I've now been able to fix this problem with a > simple patch to c-ares. > > It turns out that c-ares has had code to fall back to IPv4 since IPv6 support > was added in c-ares version 1.7.0, but this was not working for certain > cases. Specifically, when used with the Mac's default wi-fi settings, > certain routers (those provided with AT&T U-Verse Internet connections) > return "Refused" for the IPv6 AAAA query, and this response was not one of > the cases which caused a fallback to try an IPv4 A query. My patch simply > makes c-ares try an IPv4 A query for _any_ failure of the IPv6 AAAA query. > > In the meantime, c-ares version 1.7.4 has just been released, and the current > version of cURL is 7.21.2. I'm trying to decide whether we should upgrade to > the latest versions (we're still using c-ares 1.6.0 and cURL 7.19.7) or > should I continue to use cURL 7.19.7 with a patched c-ares 1.7.0. (My c-ares > patch can be applied to any version of c-ares since 1.7.0.) > > One factor is that we have been applying patches to 3 files in cURL 7.19.7 to > address a problem where it was not deleting old cached DNS records. The > source code that we were patching has changed a lot in the current cURL is > 7.21.2. And the changes log at <http://curl.haxx.se/changes.html#7_20_0> > under Bugfixes for version 7.20.0 includes: > * never-pruned DNS cached entries > > So this may have been fixed in cURL 7.20.0. Cheers, --Charlie On Aug 22, 2017, at 12:58 PM, Juha Sointusalo <juha.sointus...@gmail.com> wrote: > On 17 August 2017 at 12:18, Jord van der Elst <els...@gmail.com> wrote: > >> HI all, >> >> On the BOINC forums a user asks the following: >> *** >> Has anyone tried using BOINC in a NAT64+DNS64 network? I've moved my laptop >> to such network (after previously using it in IPv4-only and dual-stack >> Internet-connected networks), and nothing seems to work > > > Charlie, > > The client has this code in it: > > #ifdef __APPLE__ > // cURL 7.19.7 with c-ares 1.7.0 did not fall back to IPv4 when IPv6 > // DNS lookup failed on Macs with certain default settings if connected > // to the Internet by an AT&T U-Verse 2-Wire Gateway. This work-around > // may not be needed any more for cURL 7.21.7, but keep it to be safe. > curl_easy_setopt(curlEasy, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4); > #endif > > Now that there seems to be IPv6-only networks perhaps that workaround needs > to be reconsidered. > > -Juha _______________________________________________ boinc_dev mailing list boinc_dev@ssl.berkeley.edu https://lists.ssl.berkeley.edu/mailman/listinfo/boinc_dev To unsubscribe, visit the above URL and (near bottom of page) enter your email address.
