4 ms·

The latter. You can always set your /etc/hosts or equivalent to map "localhost" to some random IP that is not loopback. Or a proxy could proxy that hostname,

The latter. You can always set your /etc/hosts or equivalent to map "localhost" to some random IP that is not loopback. Or a proxy could proxy that hostname, etc. In the new setup proxies can't proxy localhost unless you set a pref to explicitly let them do that, and for "localhost" and hostnames ending in ".localhost" Firefox won't even ask the DNS stack for the IP, assuming loopback instead.

cesarb 6y ago
> Firefox won't even ask the DNS stack for the IP, assuming loopback instead. Which loopback, 127.0.0.1, ::1, or both?
- arp242 6y ago
  You have all of 127.0.0.0/8 as a loopback; I hope it doesn't hard-code 127.0.0.1 as I use some other addresses as well.
  - bzbarsky 6y ago
    "localhost" is hardcoded to resolve to "127.0.0.1" (ignoring IPv6 for now). The "is secure context" state applies to 127.0.0.0/8 (again ignoring IPv6). See NetAddr::IsLoopBackAddressWithoutIPv6Mapping in https://searchfox.org/mozilla-central/source/netwerk/dns/DNS.cpp https://searchfox.org/mozilla-central/source/netwerk/dns/DNS... I'm pretty sure all of this is clearly specified at this point, so browsers should end up all aligning on a common behavior here at some point, if they haven't yet.
- bzbarsky 6y ago
  Looking at the code in the DNS service in Firefox, it kinda looks like this for localhost: 1) If IPv6 disabled in prefs or caller explicitly requested IPv4 only, 127.0.0.1. 2) If localhost explicitly listed in the IPv4-only domains list in prefs, 127.0.0.1. 3) If caller explicitly requested IPv6 only, ::1. 4) Otherwise both 127.0.0.1 and ::1. See nsHostResolver::InitLoopbackRecord in https://searchfox.org/mozilla-central/source/netwerk/dns/nsHostResolver.cpp https://searchfox.org/mozilla-central/source/netwerk/dns/nsH... and nsDNSService::GetAFForLookup in https://searchfox.org/mozilla-central/source/netwerk/dns/nsDNSService2.cpp https://searchfox.org/mozilla-central/source/netwerk/dns/nsD... for the key.af calculation that goes into that, as far as I can tell.
  - deleted 6y ago
    [deleted]
Konohamaru 6y ago
It is amazing to behold a comment written in wizard-tongue like the above.

cesarb 6y ago

> Firefox won't even ask the DNS stack for the IP, assuming loopback instead. Which loopback, 127.0.0.1, ::1, or both?

arp242 6y ago
You have all of 127.0.0.0/8 as a loopback; I hope it doesn't hard-code 127.0.0.1 as I use some other addresses as well.
- bzbarsky 6y ago
  "localhost" is hardcoded to resolve to "127.0.0.1" (ignoring IPv6 for now). The "is secure context" state applies to 127.0.0.0/8 (again ignoring IPv6). See NetAddr::IsLoopBackAddressWithoutIPv6Mapping in https://searchfox.org/mozilla-central/source/netwerk/dns/DNS.cpp https://searchfox.org/mozilla-central/source/netwerk/dns/DNS... I'm pretty sure all of this is clearly specified at this point, so browsers should end up all aligning on a common behavior here at some point, if they haven't yet.
bzbarsky 6y ago
Looking at the code in the DNS service in Firefox, it kinda looks like this for localhost: 1) If IPv6 disabled in prefs or caller explicitly requested IPv4 only, 127.0.0.1. 2) If localhost explicitly listed in the IPv4-only domains list in prefs, 127.0.0.1. 3) If caller explicitly requested IPv6 only, ::1. 4) Otherwise both 127.0.0.1 and ::1. See nsHostResolver::InitLoopbackRecord in https://searchfox.org/mozilla-central/source/netwerk/dns/nsHostResolver.cpp https://searchfox.org/mozilla-central/source/netwerk/dns/nsH... and nsDNSService::GetAFForLookup in https://searchfox.org/mozilla-central/source/netwerk/dns/nsDNSService2.cpp https://searchfox.org/mozilla-central/source/netwerk/dns/nsD... for the key.af calculation that goes into that, as far as I can tell.
- deleted 6y ago
  [deleted]

Konohamaru 6y ago

It is amazing to behold a comment written in wizard-tongue like the above.