Hi, could you please hava a look at the following change:
http://cr.openjdk.java.net/~simonis/webrevs/8060470.v1 https://bugs.openjdk.java.net/browse/JDK-8060470 It's probably easier to read the following in the webrev, but I copy it below for discussion. Regards, Volker So here comes the first version of this change. Its main focus is the unification and simplification of Inet{4,6}AddressImpl_getLocalHostName() (notice that these native methods are currently only called from InetAddress.getLocalHost() so the impact is manageable): - Simplification: the current implementation has three versions of this function: two versions of Inet4AddressImpl_getLocalHostName() (one for "_ALLBSD_SOURCE && !HAS_GLIBC_GETHOSTBY_R" and another one for the other Unix versions) and one version of Inet6AddressImpl_getLocalHostName(). All these functions are very similar and can be easily factored out into one new method. - Unification: there are subtle and probably unnecessary differences between the IPv4 and IPv6 version of these methods which can be easily eliminated. The only difference between the two IPv4 versions was the ai_family flag passed as hint to the getaddrinfo() call. The Mac version used AF_UNSPEC while the general Unix version used AF_INET. I don't see a reason (and my tests didn't show any problems) why we couldn't use AF_INET on MacOS as well. The IPv6 version used AF_UNSPEC as well. The new refactored method getLocalHostName() which is now called from both, the single instance of Inet4AddressImpl_getLocalHostName() and Inet6AddressImpl_getLocalHostName() uses AF_INET in the IPv4 case (which shouldn't change anything) and AF_INET6 for the IPv6 case. Additionally, it uses the flag AI_V4MAPPED in the IPv6 case. This will return an IPv4-mapped IPv6 addresses if no matching IPv6 addresses could be found. The last difference between the old IPv4 and IPv6 versions was the fact that the IPv4 versions always did a reverse lookup for the host name. That means that after querying the hostname with gethostname(), they used a call to getaddrinfo() to get the IP address of the host name and finally they called getnameinfo() on that IP address to get the host name once again. The IPv6 version only did this reverse lookup on Solaris. It is unclear why this reverse lookup was necessary at all. Especially if we take into account that the resulting host name will be only used in InetAddress.getLocalHost() where it will finally serve as input to InetAddressImpl.lookupAllHostAddr() which will in turn do exactly the same reverse lookup procedure (at least if the default name service is used). Therefore the new implementation switches this reverse lookup off by default unless the user requests it with the two system properties java.net.doIPv4ReverseLookupInGetLocalHost and java.net.doIPv6ReverseLookupInGetLocalHost for IPv4 and IPv6 respectively. Consequently, the new Unix version of Java_java_net_Inet{4,6}AddressImpl_getLocalHostName is now equal to its Windows counterpart which simply returns the result of gethostname() as well. Notice that for these properties, the name "IPv4" and "IPv6" refer to the actual InetAddressImpl version (i.e. either Inet4AddressImpl or Inet6AddressImpl) that is used by InetAddress. On most modern hosts, InetAddress will use an Inet6AddressImpl helper if the host is IPv6 "capable". That doesn't necessarily mean that InetAddress.getLocalHost() will return an IPv6 address or even that there's a network interface with an IPv6 address - it just means that the network stack can handle IPv6. InetAddress can be forced to use the Inet4AddressImpl helper by setting the java.net.preferIPv4Stack property to false. In the new implementation both properties java.net.doIPv4ReverseLookupInGetLocalHost and java.net.doIPv6ReverseLookupInGetLocalHost are set to false by default. But the old behavior could be restored by setting java.net.doIPv4ReverseLookupInGetLocalHost=true and java.net.doIPv6ReverseLookupInGetLocalHost=true (Solaris only). In a previous mail thread [2] we discussed the possibility of replacing the call to getnameinfo() in Inet{4,6}AddressImpl_getLocalHostName() by simply using the ai_canonname field returned by the getaddrinfo() call. But because I think the reverse lookup is unnecessary anyway (and disabled by default in the new implementation), I didn't tried that any more and stayed with the old version. I've built these changes on Linux, Solaris, MacOS X and AIX and manually tested them on various hosts with different IPv4/IPv6 setups without any problems. In cases where the output of InetAddress.getLocalHost() differed in the new version this was only a difference in the hostname part of the InetAddress (i.e. fully qualified name vs. simple name) and this could be easily restored with the help of the new system properties. Notice that for the new version the host name now usually corresponds to what the hostname command returns on Unix which is probably what most people would expect. In the old version the host name was more dependent on the local system configuration (i.e. /etc/hosts or /etc/nsswitch.conf) as discussed in [2]. The following mail threads already discuss this issue: [1] http://mail.openjdk.java.net/pipermail/net-dev/2014-October/thread.html#8721 [2] http://mail.openjdk.java.net/pipermail/net-dev/2013-June/thread.html#6543 PS: We probably shouldn't discuss this too long as there are other methods like Java_java_net_Inet{4,6}AddressImpl_lookupAllHostAddr which are waiting for unification and simplification as well :)
