A Sample of using socket cookie and uid for traffic monitoring

Hello Chenbo Feng,

The patch 51570a5ab2b7: "A Sample of using socket cookie and uid for traffic monitoring" from Mar 22, 2017, leads to the following static checker warning:

	./samples/bpf/cookie_uid_helper_example.c:185 print_table()
	warn: unsigned 'res' is never less than zero.

samples/bpf/cookie_uid_helper_example.c
176 static void print_table(void)
177 {

   178          struct stats curEntry;
   179          uint32_t curN = UINT32_MAX;
   180          uint32_t nextN, res;
                                ^^^

Unsigned.

181
182 while (bpf_map_get_next_key(map_fd, &curN, &nextN) > -1) {

   183                  curN = nextN;
   184                  res = bpf_map_lookup_elem(map_fd, &curN, &curEntry);
   185                  if (res < 0) {
                            ^^^^^^^

Not possible.

186 error(1, errno, "fail to get entry value of Key: %u\n",
187 curN);
188 } else {
189 printf("cookie: %u, uid: 0x%x, Packet Count: %lu,"
190 " Bytes Count: %lu\n", curN, curEntry.uid,
191 curEntry.packets, curEntry.bytes);
192 }
193 }
194 }

regards,
dan carpenter