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
genl_parse_getfamily(struct nlmsghdr * nlh)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
genl_resolve_family(struct rtnl_handle * grth,const char * family)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
53 addattr_l(&req.n, sizeof(req), CTRL_ATTR_FAMILY_NAME,
54 family, strlen(family) + 1);
55
56 if (rtnl_talk(grth, &req.n, &req.n, sizeof(req)) < 0) {
57 fprintf(stderr, "Error talking to the kernel\n");
58 return -2;
59 }
60
61 return genl_parse_getfamily(&req.n);
62 }
63
genl_init_handle(struct rtnl_handle * grth,const char * family,int * genl_family)64 int genl_init_handle(struct rtnl_handle *grth, const char *family,
65 int *genl_family)
66 {
67 if (*genl_family >= 0)
68 return 0;
69
70 if (rtnl_open_byproto(grth, 0, NETLINK_GENERIC) < 0) {
71 fprintf(stderr, "Cannot open generic netlink socket\n");
72 return -1;
73 }
74
75 *genl_family = genl_resolve_family(grth, family);
76 if (*genl_family < 0)
77 return -1;
78
79 return 0;
80 }
81