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-rw-r--r--lib/libgenl.c159
1 files changed, 159 insertions, 0 deletions
diff --git a/lib/libgenl.c b/lib/libgenl.c
new file mode 100644
index 0000000..fca07f9
--- /dev/null
+++ b/lib/libgenl.c
@@ -0,0 +1,159 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * libgenl.c GENL library
+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <linux/genetlink.h>
+#include "libgenl.h"
+
+static int genl_parse_getfamily(struct nlmsghdr *nlh)
+{
+ struct rtattr *tb[CTRL_ATTR_MAX + 1];
+ struct genlmsghdr *ghdr = NLMSG_DATA(nlh);
+ int len = nlh->nlmsg_len;
+ struct rtattr *attrs;
+
+ if (nlh->nlmsg_type != GENL_ID_CTRL) {
+ fprintf(stderr, "Not a controller message, nlmsg_len=%d "
+ "nlmsg_type=0x%x\n", nlh->nlmsg_len, nlh->nlmsg_type);
+ return -1;
+ }
+
+ len -= NLMSG_LENGTH(GENL_HDRLEN);
+
+ if (len < 0) {
+ fprintf(stderr, "wrong controller message len %d\n", len);
+ return -1;
+ }
+
+ if (ghdr->cmd != CTRL_CMD_NEWFAMILY) {
+ fprintf(stderr, "Unknown controller command %d\n", ghdr->cmd);
+ return -1;
+ }
+
+ attrs = (struct rtattr *) ((char *) ghdr + GENL_HDRLEN);
+ parse_rtattr(tb, CTRL_ATTR_MAX, attrs, len);
+
+ if (tb[CTRL_ATTR_FAMILY_ID] == NULL) {
+ fprintf(stderr, "Missing family id TLV\n");
+ return -1;
+ }
+
+ return rta_getattr_u16(tb[CTRL_ATTR_FAMILY_ID]);
+}
+
+int genl_resolve_family(struct rtnl_handle *grth, const char *family)
+{
+ GENL_REQUEST(req, 1024, GENL_ID_CTRL, 0, 0, CTRL_CMD_GETFAMILY,
+ NLM_F_REQUEST);
+ struct nlmsghdr *answer;
+ int fnum;
+
+ addattr_l(&req.n, sizeof(req), CTRL_ATTR_FAMILY_NAME,
+ family, strlen(family) + 1);
+
+ if (rtnl_talk(grth, &req.n, &answer) < 0) {
+ fprintf(stderr, "Error talking to the kernel\n");
+ return -2;
+ }
+
+ fnum = genl_parse_getfamily(answer);
+ free(answer);
+
+ return fnum;
+}
+
+static int genl_parse_grps(struct rtattr *attr, const char *name, unsigned int *id)
+{
+ const struct rtattr *pos;
+
+ rtattr_for_each_nested(pos, attr) {
+ struct rtattr *tb[CTRL_ATTR_MCAST_GRP_MAX + 1];
+
+ parse_rtattr_nested(tb, CTRL_ATTR_MCAST_GRP_MAX, pos);
+
+ if (tb[CTRL_ATTR_MCAST_GRP_NAME] && tb[CTRL_ATTR_MCAST_GRP_ID]) {
+ if (strcmp(name, rta_getattr_str(tb[CTRL_ATTR_MCAST_GRP_NAME])) == 0) {
+ *id = rta_getattr_u32(tb[CTRL_ATTR_MCAST_GRP_ID]);
+ return 0;
+ }
+ }
+ }
+
+ errno = ENOENT;
+ return -1;
+}
+
+int genl_add_mcast_grp(struct rtnl_handle *grth, __u16 fnum, const char *group)
+{
+ GENL_REQUEST(req, 1024, GENL_ID_CTRL, 0, 0, CTRL_CMD_GETFAMILY,
+ NLM_F_REQUEST);
+ struct rtattr *tb[CTRL_ATTR_MAX + 1];
+ struct nlmsghdr *answer = NULL;
+ struct genlmsghdr *ghdr;
+ struct rtattr *attrs;
+ int len, ret = -1;
+ unsigned int id;
+
+ addattr16(&req.n, sizeof(req), CTRL_ATTR_FAMILY_ID, fnum);
+
+ if (rtnl_talk(grth, &req.n, &answer) < 0) {
+ fprintf(stderr, "Error talking to the kernel\n");
+ return -2;
+ }
+
+ ghdr = NLMSG_DATA(answer);
+ len = answer->nlmsg_len;
+
+ if (answer->nlmsg_type != GENL_ID_CTRL) {
+ errno = EINVAL;
+ goto err_free;
+ }
+
+ len -= NLMSG_LENGTH(GENL_HDRLEN);
+ if (len < 0) {
+ errno = EINVAL;
+ goto err_free;
+ }
+
+ attrs = (struct rtattr *) ((char *) ghdr + GENL_HDRLEN);
+ parse_rtattr(tb, CTRL_ATTR_MAX, attrs, len);
+
+ if (tb[CTRL_ATTR_MCAST_GROUPS] == NULL) {
+ errno = ENOENT;
+ fprintf(stderr, "Missing mcast groups TLV\n");
+ goto err_free;
+ }
+
+ if (genl_parse_grps(tb[CTRL_ATTR_MCAST_GROUPS], group, &id) < 0)
+ goto err_free;
+
+ ret = rtnl_add_nl_group(grth, id);
+
+err_free:
+ free(answer);
+ return ret;
+}
+
+int genl_init_handle(struct rtnl_handle *grth, const char *family,
+ int *genl_family)
+{
+ if (*genl_family >= 0)
+ return 0;
+
+ if (rtnl_open_byproto(grth, 0, NETLINK_GENERIC) < 0) {
+ fprintf(stderr, "Cannot open generic netlink socket\n");
+ return -1;
+ }
+
+ *genl_family = genl_resolve_family(grth, family);
+ if (*genl_family < 0)
+ return -1;
+
+ return 0;
+}