genl: modify genl_ctrl_resolve and friends to allow for module auto-loading
Generic netlink has the ability to autoload modules in response to a request for a family. Currently libnl uses a GETFAMILY call with the NLM_F_DUMP flag to list all the available families, but doing so neglects the possibility of an autoloaded module. This patch modifies the genl code to probe the kernel for a specific family rather than dumping a list of all the currenlty available ones, making autoload work properly. Signed-off-by: Neil Horman <nhorman@tuxdriver.com> CC: Thomas Graf <tgraf@redhat.com>
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parent
43eab4696d
commit
0c408aad1f
2 changed files with 148 additions and 45 deletions
190
lib/genl/ctrl.c
190
lib/genl/ctrl.c
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@ -61,6 +61,47 @@ static struct nla_policy family_grp_policy[CTRL_ATTR_MCAST_GRP_MAX+1] = {
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[CTRL_ATTR_MCAST_GRP_ID] = { .type = NLA_U32 },
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};
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static int parse_mcast_grps(struct genl_family *family, struct nlattr *grp_attr)
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{
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struct nlattr *nla;
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int remaining, err;
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if (!grp_attr)
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BUG();
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nla_for_each_nested(nla, grp_attr, remaining) {
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struct nlattr *tb[CTRL_ATTR_MCAST_GRP_MAX+1];
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int id;
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const char * name;
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err = nla_parse_nested(tb, CTRL_ATTR_MCAST_GRP_MAX, nla,
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family_grp_policy);
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if (err < 0)
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goto errout;
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if (tb[CTRL_ATTR_MCAST_GRP_ID] == NULL) {
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err = -NLE_MISSING_ATTR;
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goto errout;
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}
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id = nla_get_u32(tb[CTRL_ATTR_MCAST_GRP_ID]);
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if (tb[CTRL_ATTR_MCAST_GRP_NAME] == NULL) {
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err = -NLE_MISSING_ATTR;
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goto errout;
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}
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name = nla_get_string(tb[CTRL_ATTR_MCAST_GRP_NAME]);
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err = genl_family_add_grp(family, id, name);
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if (err < 0)
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goto errout;
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}
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err = 0;
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errout:
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return err;
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}
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static int ctrl_msg_parser(struct nl_cache_ops *ops, struct genl_cmd *cmd,
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struct genl_info *info, void *arg)
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{
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@ -137,37 +178,9 @@ static int ctrl_msg_parser(struct nl_cache_ops *ops, struct genl_cmd *cmd,
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}
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if (info->attrs[CTRL_ATTR_MCAST_GROUPS]) {
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struct nlattr *nla, *nla_grps;
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int remaining;
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nla_grps = info->attrs[CTRL_ATTR_MCAST_GROUPS];
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nla_for_each_nested(nla, nla_grps, remaining) {
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struct nlattr *tb[CTRL_ATTR_MCAST_GRP_MAX+1];
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int id;
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const char * name;
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err = nla_parse_nested(tb, CTRL_ATTR_MCAST_GRP_MAX, nla,
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family_grp_policy);
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if (err < 0)
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goto errout;
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if (tb[CTRL_ATTR_MCAST_GRP_ID] == NULL) {
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err = -NLE_MISSING_ATTR;
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goto errout;
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}
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id = nla_get_u32(tb[CTRL_ATTR_MCAST_GRP_ID]);
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if (tb[CTRL_ATTR_MCAST_GRP_NAME] == NULL) {
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err = -NLE_MISSING_ATTR;
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goto errout;
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}
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name = nla_get_string(tb[CTRL_ATTR_MCAST_GRP_NAME]);
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err = genl_family_add_grp(family, id, name);
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if (err < 0)
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goto errout;
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}
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err = parse_mcast_grps(family, info->attrs[CTRL_ATTR_MCAST_GROUPS]);
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if (err < 0)
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goto errout;
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}
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err = pp->pp_cb((struct nl_object *) family, pp);
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@ -176,6 +189,104 @@ errout:
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return err;
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}
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/**
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* process responses from from the query sent by genl_ctrl_probe_by_name
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* @arg nl_msg Returned message.
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* @arg name genl_family structure to fill out.
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*
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* Process returned messages, filling out the missing informatino in the
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* genl_family structure
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*
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* @return Indicator to keep processing frames or not
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*
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*/
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static int probe_response(struct nl_msg *msg, void *arg)
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{
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struct nlattr *tb[CTRL_ATTR_MAX+1];
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struct nlmsghdr *nlh = nlmsg_hdr(msg);
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struct genl_family *ret = (struct genl_family *)arg;
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if (genlmsg_parse(nlh, 0, tb, CTRL_ATTR_MAX, ctrl_policy))
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return NL_SKIP;
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if (tb[CTRL_ATTR_FAMILY_ID])
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genl_family_set_id(ret, nla_get_u16(tb[CTRL_ATTR_FAMILY_ID]));
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if (tb[CTRL_ATTR_MCAST_GROUPS])
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if (parse_mcast_grps(ret, tb[CTRL_ATTR_MCAST_GROUPS]) < 0)
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return NL_SKIP;
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return NL_STOP;
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}
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/**
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* Look up generic netlink family by family name querying the kernel directly
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* @arg sk Socket.
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* @arg name Family name.
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*
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* Directly query's the kernel for a given family name. The caller will own a
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* reference on the returned object which needsd to be given back after usage
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* using genl_family_put.
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*
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* Note: This API call differs from genl_ctrl_search_by_name in that it querys
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* the kernel directly, alowing for module autoload to take place to resolve the
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* family request. Using an nl_cache prevents that operation
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*
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* @return Generic netlink family object or NULL if no match was found.
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*/
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static struct genl_family *genl_ctrl_probe_by_name(struct nl_sock *sk, const char *name)
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{
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struct nl_msg *msg;
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struct genl_family *ret = NULL;
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struct nl_cb *cb;
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int rc;
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ret = genl_family_alloc();
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if (!ret)
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goto out;
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genl_family_set_name(ret, name);
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msg = nlmsg_alloc();
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if (!msg)
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goto out_fam_free;
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if (!(cb = nl_cb_clone(nl_socket_get_cb(sk))))
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goto out_msg_free;
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genlmsg_put(msg, NL_AUTO_PID, NL_AUTO_SEQ, GENL_ID_CTRL,
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0, 0, CTRL_CMD_GETFAMILY, 1);
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if (nla_put_string(msg, CTRL_ATTR_FAMILY_NAME, name))
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goto out_cb_free;
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rc = nl_send_auto_complete(sk, msg);
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if (rc < 0)
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goto out_cb_free;
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nl_cb_set(cb, NL_CB_VALID, NL_CB_CUSTOM, probe_response, (void *)ret);
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nl_recvmsgs(sk, cb);
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if (genl_family_get_id(ret) != 0) {
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nlmsg_free(msg);
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nl_cb_put(cb);
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return ret;
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}
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out_cb_free:
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nl_cb_put(cb);
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out_msg_free:
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nlmsg_free(msg);
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out_fam_free:
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genl_family_put(ret);
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ret = NULL;
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out:
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return ret;
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}
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/** @endcond */
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/**
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@ -299,14 +410,10 @@ struct genl_family *genl_ctrl_search_by_name(struct nl_cache *cache,
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*/
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int genl_ctrl_resolve(struct nl_sock *sk, const char *name)
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{
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struct nl_cache *cache;
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struct genl_family *family;
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int err;
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if ((err = genl_ctrl_alloc_cache(sk, &cache)) < 0)
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return err;
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family = genl_ctrl_search_by_name(cache, name);
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family = genl_ctrl_probe_by_name(sk, name);
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if (family == NULL) {
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err = -NLE_OBJ_NOTFOUND;
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goto errout;
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@ -315,8 +422,6 @@ int genl_ctrl_resolve(struct nl_sock *sk, const char *name)
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err = genl_family_get_id(family);
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genl_family_put(family);
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errout:
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nl_cache_free(cache);
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return err;
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}
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@ -348,14 +453,11 @@ static int genl_ctrl_grp_by_name(const struct genl_family *family,
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int genl_ctrl_resolve_grp(struct nl_sock *sk, const char *family_name,
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const char *grp_name)
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{
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struct nl_cache *cache;
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struct genl_family *family;
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int err;
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if ((err = genl_ctrl_alloc_cache(sk, &cache)) < 0)
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return err;
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family = genl_ctrl_search_by_name(cache, family_name);
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family = genl_ctrl_probe_by_name(sk, family_name);
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if (family == NULL) {
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err = -NLE_OBJ_NOTFOUND;
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goto errout;
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@ -364,8 +466,6 @@ int genl_ctrl_resolve_grp(struct nl_sock *sk, const char *family_name,
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err = genl_ctrl_grp_by_name(family, grp_name);
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genl_family_put(family);
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errout:
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nl_cache_free(cache);
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return err;
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}
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@ -84,6 +84,9 @@ int main(int argc, char *argv[])
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if ((err = genl_ops_resolve(sock, &ops)) < 0)
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nl_cli_fatal(err, "Unable to resolve family name");
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if (genl_ctrl_resolve(sock, "nlctrl") != GENL_ID_CTRL)
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nl_cli_fatal(NLE_INVAL, "Resolving of \"nlctrl\" failed");
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msg = nlmsg_alloc();
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if (msg == NULL)
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nl_cli_fatal(NLE_NOMEM, "Unable to allocate netlink message");
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