The nfs_proc.stp tapset is full of probes that return 'server_ip', a binary IP address of the server. A typical line to generate that value looks like this: server_ip = __i2n_ip_proto($dir,0) That works fine for IPv4. That binary value can be used in comparisons, as an array index, etc. However, the above doesn't work for IPv6. That function (if it supported IPv6) would return the address of a structure that holds the IPv6 address. Those probes should be changed to return a string representation of the IP address, which can be compared properly for both IPv4 and IPv6. (Bug #13646 provided the base tapset IPv6 support.)
Created attachment 12578 [details] the patch related to changes that give nfs_proc IPv6 support
Commit d03599, eed54b and 506de2 are related updates for supporting IPv6. With systemtap version <= 4.2, get_ip will work with only IPv4 and a long type will be returned for get_ip(); with version > 4.3, both IPv4 and IPv6 are supported while return type is String.
Comment on attachment 12578 [details] the patch related to changes that give nfs_proc IPv6 support https://paste.centos.org/view/617b7556