[PATCH] generic netlink: dynamic multicast groups

Johannes Berg
2007-07-03T11:54:05Z

Introduce API to dynamically register and unregister multicast groups.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
---
Some hackish modifications to iproute2's genl command confirm that it
does indeed work.

include/linux/genetlink.h | 13 +++
include/net/genetlink.h | 22 +++++
net/netlink/genetlink.c | 190 ++++++++++++++++++++++++++++++++++++++++++++--
3 files changed, 218 insertions(+), 7 deletions(-)

--- wireless-dev.orig/include/net/genetlink.h 2007-07-03 11:49:35.468696328 +0200
+++ wireless-dev/include/net/genetlink.h 2007-07-03 11:49:54.328696328 +0200
@@ -5,6 +5,22 @@
#include <net/netlink.h>

/**
+ * struct genl_multicast_group - generic netlink multicast group
+ * @name: name of the multicast group, names are per-family
+ * @id: multicast group ID, assigned by the core, to use with
+ * genlmsg_multicast().
+ * @list: list entry for linking
+ * @family: pointer to family, need not be set before registering
+ */
+struct genl_multicast_group
+{
+ struct genl_family *family; /* private */
+ struct list_head list; /* private */
+ char name[GENL_NAMSIZ];
+ u32 id;
+};
+
+/**
* struct genl_family - generic netlink family
* @id: protocol family idenfitier
* @hdrsize: length of user specific header in bytes
@@ -14,6 +30,7 @@
* @attrbuf: buffer to store parsed attributes
* @ops_list: list of all assigned operations
* @family_list: family list
+ * @mcast_groups: multicast groups list
*/
struct genl_family
{
@@ -25,6 +42,7 @@ struct genl_family
struct nlattr ** attrbuf; /* private */
struct list_head ops_list; /* private */
struct list_head family_list; /* private */
+ struct list_head mcast_groups; /* private */
};

/**
@@ -73,6 +91,10 @@ extern int genl_register_family(struct g
extern int genl_unregister_family(struct genl_family *family);
extern int genl_register_ops(struct genl_family *, struct genl_ops *ops);
extern int genl_unregister_ops(struct genl_family *, struct genl_ops *ops);
+extern int genl_register_mc_group(struct genl_family *family,
+ struct genl_multicast_group *grp);
+extern void genl_unregister_mc_group(struct genl_family *family,
+ struct genl_multicast_group *grp);

extern struct sock *genl_sock;

--- wireless-dev.orig/net/netlink/genetlink.c 2007-07-03 11:49:35.588696328 +0200
+++ wireless-dev/net/netlink/genetlink.c 2007-07-03 11:49:54.318696328 +0200
@@ -3,6 +3,7 @@
*
* Authors: Jamal Hadi Salim
* Thomas Graf <tgraf@suug.ch>
+ * Johannes Berg <johannes@sipsolutions.net>
*/

#include <linux/module.h>
@@ -13,6 +14,7 @@
#include <linux/string.h>
#include <linux/skbuff.h>
#include <linux/mutex.h>
+#include <linux/bitmap.h>
#include <net/sock.h>
#include <net/genetlink.h>

@@ -42,6 +44,17 @@ static void genl_unlock(void)
#define GENL_FAM_TAB_MASK (GENL_FAM_TAB_SIZE - 1)

static struct list_head family_ht[GENL_FAM_TAB_SIZE];
+/*
+ * Bitmap of multicast groups that are currently in use.
+ *
+ * To avoid an allocation at boot of just one unsigned long,
+ * declare it global instead.
+ * Bit 0 is marked as already used since group 0 is invalid,
+ * bit 1 is marked as already used since group 1 is the controller group.
+ */
+static unsigned long mc_group_start = 0x3;
+static unsigned long *mc_groups = &mc_group_start;
+static unsigned long mc_groups_longs = 1;

static int genl_ctrl_event(int event, void *data);

@@ -116,6 +129,77 @@ static inline u16 genl_generate_id(void)
return id_gen_idx;
}

+int genl_register_mc_group(struct genl_family *family,
+ struct genl_multicast_group *grp)
+{
+ int id = find_first_zero_bit(mc_groups,
+ mc_groups_longs * BITS_PER_LONG);
+ unsigned long *new_groups;
+ size_t nlen = (mc_groups_longs + 1) * sizeof(unsigned long);
+ int err;
+
+ genl_lock();
+
+ if (id >= mc_groups_longs * BITS_PER_LONG) {
+ if (mc_groups == &mc_group_start) {
+ new_groups = kzalloc(nlen, GFP_KERNEL);
+ if (!mc_groups) {
+ err = -ENOMEM;
+ goto out;
+ }
+ mc_groups = new_groups;
+ *mc_groups = mc_group_start;
+ } else {
+ new_groups = krealloc(mc_groups, nlen, GFP_KERNEL);
+ if (!new_groups) {
+ err = -ENOMEM;
+ goto out;
+ }
+ mc_groups = new_groups;
+ mc_groups[mc_groups_longs] = 0;
+ }
+ mc_groups_longs++;
+ }
+
+ err = netlink_change_ngroups(NETLINK_GENERIC,
+ sizeof(unsigned long) * NETLINK_GENERIC);
+ if (err)
+ goto out;
+
+ grp->id = id;
+ set_bit(id, mc_groups);
+ list_add_tail(&grp->list, &family->mcast_groups);
+ grp->family = family;
+
+ genl_ctrl_event(CTRL_CMD_NEWMCAST_GRP, grp);
+ out:
+ genl_unlock();
+ return 0;
+}
+EXPORT_SYMBOL(genl_register_mc_group);
+
+void genl_unregister_mc_group(struct genl_family *family,
+ struct genl_multicast_group *grp)
+{
+ BUG_ON(grp->family != family);
+ genl_lock();
+ netlink_clear_multicast_users(NETLINK_GENERIC, grp->id);
+ clear_bit(grp->id, mc_groups);
+ list_del(&grp->list);
+ genl_ctrl_event(CTRL_CMD_DELMCAST_GRP, grp);
+ grp->id = 0;
+ grp->family = NULL;
+ genl_unlock();
+}
+
+static void genl_unregister_mc_groups(struct genl_family *family)
+{
+ struct genl_multicast_group *grp, *tmp;
+
+ list_for_each_entry_safe(grp, tmp, &family->mcast_groups, list)
+ genl_unregister_mc_group(family, grp);
+}
+
/**
* genl_register_ops - register generic netlink operations
* @family: generic netlink family
@@ -216,6 +300,7 @@ int genl_register_family(struct genl_fam
goto errout;

INIT_LIST_HEAD(&family->ops_list);
+ INIT_LIST_HEAD(&family->mcast_groups);

genl_lock();

@@ -275,6 +360,8 @@ int genl_unregister_family(struct genl_f
{
struct genl_family *rc;

+ genl_unregister_mc_groups(family);
+
genl_lock();

list_for_each_entry(rc, genl_family_chain(family->id), family_list) {
@@ -410,6 +497,67 @@ static int ctrl_fill_info(struct genl_fa
nla_nest_end(skb, nla_ops);
}

+ if (!list_empty(&family->mcast_groups)) {
+ struct genl_multicast_group *grp;
+ struct nlattr *nla_grps;
+ int idx = 1;
+
+ nla_grps = nla_nest_start(skb, CTRL_ATTR_MCAST_GROUPS);
+ if (nla_grps == NULL)
+ goto nla_put_failure;
+
+ list_for_each_entry(grp, &family->mcast_groups, list) {
+ struct nlattr *nest;
+
+ nest = nla_nest_start(skb, idx++);
+ if (nest == NULL)
+ goto nla_put_failure;
+
+ NLA_PUT_U32(skb, CTRL_ATTR_MCAST_GRP_ID, grp->id);
+ NLA_PUT_STRING(skb, CTRL_ATTR_MCAST_GRP_NAME,
+ grp->name);
+
+ nla_nest_end(skb, nest);
+ }
+ nla_nest_end(skb, nla_grps);
+ }
+
+ return genlmsg_end(skb, hdr);
+
+nla_put_failure:
+ return genlmsg_cancel(skb, hdr);
+}
+
+static int ctrl_fill_mcgrp_info(struct genl_multicast_group *grp, u32 pid,
+ u32 seq, u32 flags, struct sk_buff *skb,
+ u8 cmd)
+{
+ void *hdr;
+ struct nlattr *nla_grps;
+ struct nlattr *nest;
+
+ hdr = genlmsg_put(skb, pid, seq, &genl_ctrl, flags, cmd);
+ if (hdr == NULL)
+ return -1;
+
+ NLA_PUT_STRING(skb, CTRL_ATTR_FAMILY_NAME, grp->family->name);
+ NLA_PUT_U16(skb, CTRL_ATTR_FAMILY_ID, grp->family->id);
+
+ nla_grps = nla_nest_start(skb, CTRL_ATTR_MCAST_GROUPS);
+ if (nla_grps == NULL)
+ goto nla_put_failure;
+
+ nest = nla_nest_start(skb, 1);
+ if (nest == NULL)
+ goto nla_put_failure;
+
+ NLA_PUT_U32(skb, CTRL_ATTR_MCAST_GRP_ID, grp->id);
+ NLA_PUT_STRING(skb, CTRL_ATTR_MCAST_GRP_NAME,
+ grp->name);
+
+ nla_nest_end(skb, nest);
+ nla_nest_end(skb, nla_grps);
+
return genlmsg_end(skb, hdr);

nla_put_failure:
@@ -453,8 +601,8 @@ errout:
return skb->len;
}

-static struct sk_buff *ctrl_build_msg(struct genl_family *family, u32 pid,
- int seq, u8 cmd)
+static struct sk_buff *ctrl_build_family_msg(struct genl_family *family,
+ u32 pid, int seq, u8 cmd)
{
struct sk_buff *skb;
int err;
@@ -472,6 +620,25 @@ static struct sk_buff *ctrl_build_msg(st
return skb;
}

+static struct sk_buff *ctrl_build_mcgrp_msg(struct genl_multicast_group *grp,
+ u32 pid, int seq, u8 cmd)
+{
+ struct sk_buff *skb;
+ int err;
+
+ skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+ if (skb == NULL)
+ return ERR_PTR(-ENOBUFS);
+
+ err = ctrl_fill_mcgrp_info(grp, pid, seq, 0, skb, cmd);
+ if (err < 0) {
+ nlmsg_free(skb);
+ return ERR_PTR(err);
+ }
+
+ return skb;
+}
+
static const struct nla_policy ctrl_policy[CTRL_ATTR_MAX+1] = {
[CTRL_ATTR_FAMILY_ID] = { .type = NLA_U16 },
[CTRL_ATTR_FAMILY_NAME] = { .type = NLA_NUL_STRING,
@@ -501,8 +668,8 @@ static int ctrl_getfamily(struct sk_buff
goto errout;
}

- msg = ctrl_build_msg(res, info->snd_pid, info->snd_seq,
- CTRL_CMD_NEWFAMILY);
+ msg = ctrl_build_family_msg(res, info->snd_pid, info->snd_seq,
+ CTRL_CMD_NEWFAMILY);
if (IS_ERR(msg)) {
err = PTR_ERR(msg);
goto errout;
@@ -523,7 +690,15 @@ static int genl_ctrl_event(int event, vo
switch (event) {
case CTRL_CMD_NEWFAMILY:
case CTRL_CMD_DELFAMILY:
- msg = ctrl_build_msg(data, 0, 0, event);
+ msg = ctrl_build_family_msg(data, 0, 0, event);
+ if (IS_ERR(msg))
+ return PTR_ERR(msg);
+
+ genlmsg_multicast(msg, 0, GENL_ID_CTRL, GFP_KERNEL);
+ break;
+ case CTRL_CMD_NEWMCAST_GRP:
+ case CTRL_CMD_DELMCAST_GRP:
+ msg = ctrl_build_mcgrp_msg(data, 0, 0, event);
if (IS_ERR(msg))
return PTR_ERR(msg);

@@ -557,8 +732,9 @@ static int __init genl_init(void)
goto errout_register;

netlink_set_nonroot(NETLINK_GENERIC, NL_NONROOT_RECV);
- genl_sock = netlink_kernel_create(NETLINK_GENERIC, GENL_MAX_ID,
- genl_rcv, NULL, THIS_MODULE);
+ /* only one static multicast group */
+ genl_sock = netlink_kernel_create(NETLINK_GENERIC, 1, genl_rcv,
+ NULL, THIS_MODULE);
if (genl_sock == NULL)
panic("GENL: Cannot initialize generic netlink\n");

--- wireless-dev.orig/include/linux/genetlink.h 2007-07-03 11:49:35.498696328 +0200
+++ wireless-dev/include/linux/genetlink.h 2007-07-03 11:49:54.328696328 +0200
@@ -39,6 +39,9 @@ enum {
CTRL_CMD_NEWOPS,
CTRL_CMD_DELOPS,
CTRL_CMD_GETOPS,
+ CTRL_CMD_NEWMCAST_GRP,
+ CTRL_CMD_DELMCAST_GRP,
+ CTRL_CMD_GETMCAST_GRP, /* unused */
__CTRL_CMD_MAX,
};

@@ -52,6 +55,7 @@ enum {
CTRL_ATTR_HDRSIZE,
CTRL_ATTR_MAXATTR,
CTRL_ATTR_OPS,
+ CTRL_ATTR_MCAST_GROUPS,
__CTRL_ATTR_MAX,
};

@@ -66,4 +70,13 @@ enum {

#define CTRL_ATTR_OP_MAX (__CTRL_ATTR_OP_MAX - 1)

+enum {
+ CTRL_ATTR_MCAST_GRP_UNSPEC,
+ CTRL_ATTR_MCAST_GRP_NAME,
+ CTRL_ATTR_MCAST_GRP_ID,
+ __CTRL_ATTR_MCAST_GRP_MAX,
+};
+
+#define CTRL_ATTR_MCAST_GRP_MAX (__CTRL_ATTR_MCAST_GRP_MAX - 1)
+
#endif /* __LINUX_GENERIC_NETLINK_H */