lib/libgenl.c

   1 /*
   2  * libgenl.c    GENL library
   3  */
   4
   5 #include <stdio.h>
   6 #include <stdlib.h>
   7 #include <unistd.h>
   8
   9 #include <linux/genetlink.h>
  10 #include "libgenl.h"
  11
  12 static int genl_parse_getfamily(struct nlmsghdr *nlh)
  13 {
  14         struct rtattr *tb[CTRL_ATTR_MAX + 1];
  15         struct genlmsghdr *ghdr = NLMSG_DATA(nlh);
  16         int len = nlh->nlmsg_len;
  17         struct rtattr *attrs;
  18
  19         if (nlh->nlmsg_type != GENL_ID_CTRL) {
  20                 fprintf(stderr, "Not a controller message, nlmsg_len=%d "
  21                         "nlmsg_type=0x%x\n", nlh->nlmsg_len, nlh->nlmsg_type);
  22                 return -1;
  23         }
  24
  25         len -= NLMSG_LENGTH(GENL_HDRLEN);
  26
  27         if (len < 0) {
  28                 fprintf(stderr, "wrong controller message len %d\n", len);
  29                 return -1;
  30         }
  31
  32         if (ghdr->cmd != CTRL_CMD_NEWFAMILY) {
  33                 fprintf(stderr, "Unknown controller command %d\n", ghdr->cmd);
  34                 return -1;
  35         }
  36
  37         attrs = (struct rtattr *) ((char *) ghdr + GENL_HDRLEN);
  38         parse_rtattr(tb, CTRL_ATTR_MAX, attrs, len);
  39
  40         if (tb[CTRL_ATTR_FAMILY_ID] == NULL) {
  41                 fprintf(stderr, "Missing family id TLV\n");
  42                 return -1;
  43         }
  44
  45         return rta_getattr_u16(tb[CTRL_ATTR_FAMILY_ID]);
  46 }
  47
  48 int genl_resolve_family(struct rtnl_handle *grth, const char *family)
  49 {
  50         GENL_REQUEST(req, 1024, GENL_ID_CTRL, 0, 0, CTRL_CMD_GETFAMILY,
  51                      NLM_F_REQUEST);
  52         struct nlmsghdr *answer;
  53         int fnum;
  54
  55         addattr_l(&req.n, sizeof(req), CTRL_ATTR_FAMILY_NAME,
  56                   family, strlen(family) + 1);
  57
  58         if (rtnl_talk(grth, &req.n, &answer) < 0) {
  59                 fprintf(stderr, "Error talking to the kernel\n");
  60                 return -2;
  61         }
  62
  63         fnum = genl_parse_getfamily(answer);
  64         free(answer);
  65
  66         return fnum;
  67 }
  68
  69 int genl_init_handle(struct rtnl_handle *grth, const char *family,
  70                      int *genl_family)
  71 {
  72         if (*genl_family >= 0)
  73                 return 0;
  74
  75         if (rtnl_open_byproto(grth, 0, NETLINK_GENERIC) < 0) {
  76                 fprintf(stderr, "Cannot open generic netlink socket\n");
  77                 return -1;
  78         }
  79
  80         *genl_family = genl_resolve_family(grth, family);
  81         if (*genl_family < 0)
  82                 return -1;
  83
  84         return 0;
  85 }