"/etc/resolv.conf" assumed default path is wrong for termux

[rawrrawrfox]

termux: the default path for resolv.conf file is not "/etc/resolv.conf", but the code presumes that to be the case

termux is a terminal app for android capable of running many linux utilites

the file resolv.conf is not found at the default location which therefore breaks other projects which use this one as a dependency

i ran accross this problem when trying to run the termux version of onionshare (https://github.com/oleanderxoxo/onidroid) which uses this library as a dependency somewhere downstream

i'm not sure what would be the most elegant solution to the resolv.conf location problem, but i've tested this code, and it works as a quickfix nonetheless

it checks if the $PREFIX environment variable is set and if it points to the termux app's "...data/files/usr" system path, then specifies explicitly the location of the resolv.conf file when creating the resolver object, which needs to be $PREFIX + "/etc/resolv.conf"

[temoto]

@rawrrawrfox thank you. Configurable location of resolv.conf is a great feature.

I think we should try to support one of:

• EVENTLET_RESOLV_CONF=/path/to/resolv.conf or just RESOLV_CONF at first, becase second option plain $PREFIX/etc/resolv.conf may break unexpectedly in a lot of build environments.
• $PREFIX/etc/resolv.conf seems most reasonable after specific path option for resolv.conf file.

Unless required, I'm strongly against hardcode integration with one particular platform+application (Android/termux). It should work for other applications that set PREFIX like termux but to another value. IMHO, it would be awkward to limit this useful feature to Android.

@eventlet/developers @jstasiak @tipabu @clayg @edwardgeorge @nat-goodspeed @vikt0rs please say

[clayg]

@rawrrawrfox I agree with @temoto strong preference for EVENTLET_RESOLV_CONF=/path/to/resolv.conf - I found no such facility in dns.resolver.Resolver

No need for anything platform specific:

diff --git a/eventlet/support/greendns.py b/eventlet/support/greendns.py
index 76545c7..eadac2b 100644
--- a/eventlet/support/greendns.py
+++ b/eventlet/support/greendns.py
@@ -408,7 +408,8 @@ class ResolverProxy(object):
         return aliases
 
 
-resolver = ResolverProxy(hosts_resolver=HostsResolver())
+resolver = ResolverProxy(hosts_resolver=HostsResolver(), filename=os.environ.get(
+    'EVENTLET_RESOLV_CONF', '/etc/resolv.conf'))
 
 
 def resolve(name, family=socket.AF_INET, raises=True, _proxy=None,