nfs_map_group_to_gid
if (nfs_map_group_to_gid(server, group->data, group->len, &gid) == 0) {
int nfs_map_group_to_gid(const struct nfs_server *, const char *, size_t, kgid_t *);
if (len <= 0 || nfs_map_group_to_gid(server, p, len, gid) != 0)