PF_RT_RETURN_TTL
snl_add_msg_attr_u8(nw, PF_RT_RETURN_TTL, r->return_ttl);
{ .type = PF_RT_RETURN_TTL, .off = _OUT(r.return_ttl), .cb = snl_attr_get_uint8 },
nlattr_add_u8(nw, PF_RT_RETURN_TTL, rule->return_ttl);
{ .type = PF_RT_RETURN_TTL, .off = _OUT(return_ttl), .cb = nlattr_get_uint8 },