I tried to run zookeeper c-client on a machine with IPv6 enabled. When connecting to the IPv6 address a connect(...) gave a "Address family not supported by protocol" error. The reason was, that a few lines earlier, the socket was opened with PF_INET instead of PF_INET6. Changing that the following way:
turned the error message into "Invalid argument".
When printing out sizeof(struct sockaddr), sizeof(struct sockaddr_in) and sizeof(struct sockaddr_in6) I got sockaddr: 16, sockaddr_in: 16 and sockaddr_in6: 28.
So in the code calling
the parameter address_len is too small.
Same applies to how IPv6 addresses are handled in the function getaddrs(zhandle_t *zh).
(Big Thanks+kiss to Thilo Fromm for helping me debug this.)