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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>
This commit is contained in:
Neil Horman 2012-06-01 12:59:24 -04:00 committed by Thomas Graf
parent 43eab4696d
commit 0c408aad1f
2 changed files with 148 additions and 45 deletions
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190
lib/genl/ctrl.c
View File

@ -61,6 +61,47 @@ static struct nla_policy family_grp_policy[CTRL_ATTR_MCAST_GRP_MAX+1] = {
[CTRL_ATTR_MCAST_GRP_ID] = { .type = NLA_U32 },
};
static int parse_mcast_grps(struct genl_family *family, struct nlattr *grp_attr)
{
struct nlattr *nla;
int remaining, err;
if (!grp_attr)
BUG();
nla_for_each_nested(nla, grp_attr, remaining) {
struct nlattr *tb[CTRL_ATTR_MCAST_GRP_MAX+1];
int id;
const char * name;
err = nla_parse_nested(tb, CTRL_ATTR_MCAST_GRP_MAX, nla,
family_grp_policy);
if (err < 0)
goto errout;
if (tb[CTRL_ATTR_MCAST_GRP_ID] == NULL) {
err = -NLE_MISSING_ATTR;
goto errout;
}
id = nla_get_u32(tb[CTRL_ATTR_MCAST_GRP_ID]);
if (tb[CTRL_ATTR_MCAST_GRP_NAME] == NULL) {
err = -NLE_MISSING_ATTR;
goto errout;
}
name = nla_get_string(tb[CTRL_ATTR_MCAST_GRP_NAME]);
err = genl_family_add_grp(family, id, name);
if (err < 0)
goto errout;
}
err = 0;
errout:
return err;
}
static int ctrl_msg_parser(struct nl_cache_ops *ops, struct genl_cmd *cmd,
struct genl_info *info, void *arg)
{
@ -137,37 +178,9 @@ static int ctrl_msg_parser(struct nl_cache_ops *ops, struct genl_cmd *cmd,
}
if (info->attrs[CTRL_ATTR_MCAST_GROUPS]) {
struct nlattr *nla, *nla_grps;
int remaining;
nla_grps = info->attrs[CTRL_ATTR_MCAST_GROUPS];
nla_for_each_nested(nla, nla_grps, remaining) {
struct nlattr *tb[CTRL_ATTR_MCAST_GRP_MAX+1];
int id;
const char * name;
err = nla_parse_nested(tb, CTRL_ATTR_MCAST_GRP_MAX, nla,
family_grp_policy);
if (err < 0)
goto errout;
if (tb[CTRL_ATTR_MCAST_GRP_ID] == NULL) {
err = -NLE_MISSING_ATTR;
goto errout;
}
id = nla_get_u32(tb[CTRL_ATTR_MCAST_GRP_ID]);
if (tb[CTRL_ATTR_MCAST_GRP_NAME] == NULL) {
err = -NLE_MISSING_ATTR;
goto errout;
}
name = nla_get_string(tb[CTRL_ATTR_MCAST_GRP_NAME]);
err = genl_family_add_grp(family, id, name);
if (err < 0)
goto errout;
}
err = parse_mcast_grps(family, info->attrs[CTRL_ATTR_MCAST_GROUPS]);
if (err < 0)
goto errout;
}
err = pp->pp_cb((struct nl_object *) family, pp);
@ -176,6 +189,104 @@ errout:
return err;
}
/**
* process responses from from the query sent by genl_ctrl_probe_by_name
* @arg nl_msg Returned message.
* @arg name genl_family structure to fill out.
*
* Process returned messages, filling out the missing informatino in the
* genl_family structure
*
* @return Indicator to keep processing frames or not
*
*/
static int probe_response(struct nl_msg *msg, void *arg)
{
struct nlattr *tb[CTRL_ATTR_MAX+1];
struct nlmsghdr *nlh = nlmsg_hdr(msg);
struct genl_family *ret = (struct genl_family *)arg;
if (genlmsg_parse(nlh, 0, tb, CTRL_ATTR_MAX, ctrl_policy))
return NL_SKIP;
if (tb[CTRL_ATTR_FAMILY_ID])
genl_family_set_id(ret, nla_get_u16(tb[CTRL_ATTR_FAMILY_ID]));
if (tb[CTRL_ATTR_MCAST_GROUPS])
if (parse_mcast_grps(ret, tb[CTRL_ATTR_MCAST_GROUPS]) < 0)
return NL_SKIP;
return NL_STOP;
}
/**
* Look up generic netlink family by family name querying the kernel directly
* @arg sk Socket.
* @arg name Family name.
*
* Directly query's the kernel for a given family name. The caller will own a
* reference on the returned object which needsd to be given back after usage
* using genl_family_put.
*
* Note: This API call differs from genl_ctrl_search_by_name in that it querys
* the kernel directly, alowing for module autoload to take place to resolve the
* family request. Using an nl_cache prevents that operation
*
* @return Generic netlink family object or NULL if no match was found.
*/
static struct genl_family *genl_ctrl_probe_by_name(struct nl_sock *sk, const char *name)
{
struct nl_msg *msg;
struct genl_family *ret = NULL;
struct nl_cb *cb;
int rc;
ret = genl_family_alloc();
if (!ret)
goto out;
genl_family_set_name(ret, name);
msg = nlmsg_alloc();
if (!msg)
goto out_fam_free;
if (!(cb = nl_cb_clone(nl_socket_get_cb(sk))))
goto out_msg_free;
genlmsg_put(msg, NL_AUTO_PID, NL_AUTO_SEQ, GENL_ID_CTRL,
0, 0, CTRL_CMD_GETFAMILY, 1);
if (nla_put_string(msg, CTRL_ATTR_FAMILY_NAME, name))
goto out_cb_free;
rc = nl_send_auto_complete(sk, msg);
if (rc < 0)
goto out_cb_free;
nl_cb_set(cb, NL_CB_VALID, NL_CB_CUSTOM, probe_response, (void *)ret);
nl_recvmsgs(sk, cb);
if (genl_family_get_id(ret) != 0) {
nlmsg_free(msg);
nl_cb_put(cb);
return ret;
}
out_cb_free:
nl_cb_put(cb);
out_msg_free:
nlmsg_free(msg);
out_fam_free:
genl_family_put(ret);
ret = NULL;
out:
return ret;
}
/** @endcond */
/**
@ -299,14 +410,10 @@ struct genl_family *genl_ctrl_search_by_name(struct nl_cache *cache,
*/
int genl_ctrl_resolve(struct nl_sock *sk, const char *name)
{
struct nl_cache *cache;
struct genl_family *family;
int err;
if ((err = genl_ctrl_alloc_cache(sk, &cache)) < 0)
return err;
family = genl_ctrl_search_by_name(cache, name);
family = genl_ctrl_probe_by_name(sk, name);
if (family == NULL) {
err = -NLE_OBJ_NOTFOUND;
goto errout;
@ -315,8 +422,6 @@ int genl_ctrl_resolve(struct nl_sock *sk, const char *name)
err = genl_family_get_id(family);
genl_family_put(family);
errout:
nl_cache_free(cache);
return err;
}
@ -348,14 +453,11 @@ static int genl_ctrl_grp_by_name(const struct genl_family *family,
int genl_ctrl_resolve_grp(struct nl_sock *sk, const char *family_name,
const char *grp_name)
{
struct nl_cache *cache;
struct genl_family *family;
int err;
if ((err = genl_ctrl_alloc_cache(sk, &cache)) < 0)
return err;
family = genl_ctrl_search_by_name(cache, family_name);
family = genl_ctrl_probe_by_name(sk, family_name);
if (family == NULL) {
err = -NLE_OBJ_NOTFOUND;
goto errout;
@ -364,8 +466,6 @@ int genl_ctrl_resolve_grp(struct nl_sock *sk, const char *family_name,
err = genl_ctrl_grp_by_name(family, grp_name);
genl_family_put(family);
errout:
nl_cache_free(cache);
return err;
}

3
tests/test-genl.c
View File

@ -84,6 +84,9 @@ int main(int argc, char *argv[])
if ((err = genl_ops_resolve(sock, &ops)) < 0)
nl_cli_fatal(err, "Unable to resolve family name");
if (genl_ctrl_resolve(sock, "nlctrl") != GENL_ID_CTRL)
nl_cli_fatal(NLE_INVAL, "Resolving of \"nlctrl\" failed");
msg = nlmsg_alloc();
if (msg == NULL)
nl_cli_fatal(NLE_NOMEM, "Unable to allocate netlink message");