libnftnl adding element to a set of type ipv4_addr or ipv6_addr

[Easynet <devel@easynet.dev>]

Hi,

I'm building a small firewall daemon that it receives if an user is 
authenticated and then is adding his IP in a set to be allowed for 24h.
I'm new in nftnl library and I started to read the documentation and 
also the examples.

Until now I was able to add in my daemon these tools based on libnftnl:

- create / delete / get tables
- create / delete chains
- create / delete sets.

Right now I'm facing an issue that I can't understand how to build the 
nftnl packet for adding an element to my set, which has interval and 
timeout flags.

The function I'm using it looks very similar to one in libnftnl, with 
modifications:

/*
* Set add element
*/
int32_t nft_set_element_add(char *req_family, char *table_name, char 
*set_name, char *element)
{
     struct mnl_socket *nl;
     char buf[MNL_SOCKET_BUFFER_SIZE];
     struct mnl_nlmsg_batch *batch;
     struct nlmsghdr *nlh;
     uint32_t portid, seq, family;
     struct nftnl_set *s;
     struct nftnl_set_elem *e;
     uint16_t data;
     uint32_t mask;
     uint32_t data32;
     uint64_t data64;
     uint64_t timeout;

     char strAddr[32];

     in_addr_t ipv4;

     int ret;

     s = nftnl_set_alloc();
     if (s == NULL) {
         perror("OOM");
         exit(EXIT_FAILURE);
     }

     seq = time(NULL);

     family = nft_check_table_family(req_family);

     nftnl_set_set_str(s, NFTNL_SET_TABLE, table_name);
     nftnl_set_set_str(s, NFTNL_SET_NAME, set_name);

     /* Add to dummy elements to set */
     e = nftnl_set_elem_alloc();
     if (e == NULL) {
         perror("OOM");
         exit(EXIT_FAILURE);
     }

     strcpy(strAddr, "192.168.10.10");

     ipv4 = inet_addr(strAddr);
     printf("IPv4: %u\n", ipv4);
     //timeout = 3600;

     nftnl_set_elem_set(e, NFTNL_SET_ELEM_KEY, &ipv4, sizeof(ipv4));
     //nftnl_set_elem_set(e, NFTNL_SET_ELEM_TIMEOUT, &timeout , 
sizeof(timeout));
     nftnl_set_elem_add(s, e);

     batch = mnl_nlmsg_batch_start(buf, sizeof(buf));

     nftnl_batch_begin(mnl_nlmsg_batch_current(batch), seq++);
     mnl_nlmsg_batch_next(batch);

     nlh = nftnl_nlmsg_build_hdr(mnl_nlmsg_batch_current(batch),
                     NFT_MSG_NEWSETELEM, family,
                     NLM_F_CREATE | NLM_F_EXCL | NLM_F_ACK,
                     seq++);
     nftnl_set_elems_nlmsg_build_payload(nlh, s);
     nftnl_set_free(s);
     mnl_nlmsg_batch_next(batch);

     nftnl_batch_end(mnl_nlmsg_batch_current(batch), seq++);
     mnl_nlmsg_batch_next(batch);

     nl = mnl_socket_open(NETLINK_NETFILTER);
     if (nl == NULL) {
         perror("mnl_socket_open");
         exit(EXIT_FAILURE);
     }

     if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0) {
         perror("mnl_socket_bind");
         exit(EXIT_FAILURE);
     }
     portid = mnl_socket_get_portid(nl);

     if (mnl_socket_sendto(nl, mnl_nlmsg_batch_head(batch),
                   mnl_nlmsg_batch_size(batch)) < 0) {
         perror("mnl_socket_send");
         return(EXIT_FAILURE);
     }

     mnl_nlmsg_batch_stop(batch);

     ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
     while (ret > 0) {
         ret = mnl_cb_run(buf, ret, 0, portid, NULL, NULL);
         if (ret <= 0)
             break;
         ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
     }
     if (ret == -1) {
         perror("error");
         return EXIT_FAILURE;
     }
     mnl_socket_close(nl);

     return EXIT_SUCCESS;
}

I was able to add timeout flag for the IP, but the IP is added as a range:

         set IPTVv4_ALLOW {
                 type ipv4_addr
                 flags interval,timeout
                 elements = { 192.168.10.10-255.255.255.255 }
         }


I couldn't find too much information in the documentation or looking 
into the nftables code or Linux Kernel. For me are too complicated to 
understand the logic behind.
Can somebody advice me how can I implement the nflnl message correctly 
to be able to add just the host for example? Or where I can find the 
info about how nftnl message should be created?

Kind regards.