[PATCH v3] compat: backport netlink changes used in the nl80211 cleanup

[Felix Fietkau <nbd@openwrt.org>]

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
---
v2:
- fix genl_unregister_family wrapper (removes the family from the internal list)
- fix error handling in doit ops
v3:
- fix a theoretical race in family unregister

--- a/include/linux/compat-2.6.37.h
+++ b/include/linux/compat-2.6.37.h
@@ -45,6 +45,68 @@ static inline void skb_checksum_none_ass
 
 #define pcmcia_enable_device(link)	pcmcia_request_configuration(link, &link->conf)
 
+#include <net/genetlink.h>
+
+struct compat_genl_info {
+	struct genl_info *info;
+
+	u32 snd_seq;
+	u32 snd_pid;
+	struct genlmsghdr *genlhdr;
+	struct nlattr **attrs;
+	void *user_ptr[2];
+};
+#define genl_info compat_genl_info
+
+struct compat_genl_ops {
+	struct genl_ops ops;
+
+	u8 cmd;
+	u8 internal_flags;
+	unsigned int flags;
+	const struct nla_policy *policy;
+
+	int (*doit)(struct sk_buff *skb, struct genl_info *info);
+	int (*dumpit)(struct sk_buff *skb, struct netlink_callback *cb);
+	int (*done)(struct netlink_callback *cb);
+};
+#define genl_ops compat_genl_ops
+
+struct compat_genl_family {
+	struct genl_family family;
+
+	struct list_head list;
+
+	unsigned int id, hdrsize, version, maxattr;
+	const char *name;
+	bool netnsok;
+
+	struct nlattr **attrbuf;
+
+	int (*pre_doit)(struct genl_ops *ops, struct sk_buff *skb,
+			struct genl_info *info);
+
+	void (*post_doit)(struct genl_ops *ops, struct sk_buff *skb,
+			  struct genl_info *info);
+};
+
+#define genl_family compat_genl_family
+
+#define genl_register_family_with_ops compat_genl_register_family_with_ops
+
+int genl_register_family_with_ops(struct genl_family *family,
+				  struct genl_ops *ops, size_t n_ops);
+
+#define genl_unregister_family compat_genl_unregister_family
+
+int genl_unregister_family(struct genl_family *family);
+
+#define genl_info_net(_info) genl_info_net((_info)->info)
+#define genlmsg_reply(_msg, _info) genlmsg_reply(_msg, (_info)->info)
+#define genlmsg_put(_skb, _pid, _seq, _fam, _flags, _cmd) genlmsg_put(_skb, _pid, _seq, &(_fam)->family, _flags, _cmd)
+#define genl_register_mc_group(_fam, _grp) genl_register_mc_group(&(_fam)->family, _grp)
+#define genl_unregister_mc_group(_fam, _grp) genl_unregister_mc_group(&(_fam)->family, _grp)
+
 #endif /* (LINUX_VERSION_CODE < KERNEL_VERSION(2,6,37)) */
 
 #endif /* LINUX_26_37_COMPAT_H */
--- a/compat/compat-2.6.37.c
+++ b/compat/compat-2.6.37.c
@@ -42,4 +42,116 @@ EXPORT_SYMBOL_GPL(net_ns_type_operations
 
 #endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,35)*/ 
 
+#undef genl_info
+#undef genl_unregister_family
+
+static LIST_HEAD(compat_nl_fam);
+
+static struct genl_ops *genl_get_cmd(u8 cmd, struct genl_family *family)
+{
+	struct genl_ops *ops;
+
+	list_for_each_entry(ops, &family->family.ops_list, ops.ops_list)
+		if (ops->cmd == cmd)
+			return ops;
+
+	return NULL;
+}
+
+
+static int nl_doit_wrapper(struct sk_buff *skb, struct genl_info *info)
+{
+	struct compat_genl_info compat_info;
+	struct genl_family *family;
+	struct genl_ops *ops;
+	int err;
+
+	list_for_each_entry(family, &compat_nl_fam, list) {
+		if (family->id == info->nlhdr->nlmsg_type)
+			goto found;
+	}
+	return -ENOENT;
+
+found:
+	ops = genl_get_cmd(info->genlhdr->cmd, family);
+	if (!ops)
+		return -ENOENT;
+
+	memset(&compat_info.user_ptr, 0, sizeof(compat_info.user_ptr));
+	compat_info.info = info;
+#define __copy(_field) compat_info._field = info->_field
+	__copy(snd_seq);
+	__copy(snd_pid);
+	__copy(genlhdr);
+	__copy(attrs);
+#undef __copy
+	if (family->pre_doit) {
+		err = family->pre_doit(ops, skb, &compat_info);
+		if (err)
+			return err;
+	}
+
+	err = ops->doit(skb, &compat_info);
+
+	if (family->post_doit)
+		family->post_doit(ops, skb, &compat_info);
+
+	return err;
+}
+
+int compat_genl_register_family_with_ops(struct genl_family *family,
+					 struct genl_ops *ops, size_t n_ops)
+{
+	int i, ret;
+
+#define __copy(_field) family->family._field = family->_field
+	__copy(id);
+	__copy(hdrsize);
+	__copy(version);
+	__copy(maxattr);
+	strncpy(family->family.name, family->name, sizeof(family->family.name));
+#if (LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,32))
+	__copy(netnsok);
+#endif
+#undef __copy
+
+	ret = genl_register_family(&family->family);
+	if (ret < 0)
+		return ret;
+
+	family->attrbuf = family->family.attrbuf;
+	family->id = family->family.id;
+
+	for (i = 0; i < n_ops; i++) {
+#define __copy(_field) ops[i].ops._field = ops[i]._field
+		__copy(cmd);
+		__copy(flags);
+		__copy(policy);
+		__copy(dumpit);
+		__copy(done);
+#undef __copy
+		ops[i].ops.doit = nl_doit_wrapper;
+		ret = genl_register_ops(&family->family, &ops[i].ops);
+		if (ret < 0)
+			goto error_ops;
+	}
+	list_add(&family->list, &compat_nl_fam);
+
+	return ret;
+
+error_ops:
+	compat_genl_unregister_family(family);
+	return ret;
+}
+EXPORT_SYMBOL(compat_genl_register_family_with_ops);
+
+int compat_genl_unregister_family(struct genl_family *family)
+{
+	int err;
+	err = genl_unregister_family(&family->family);
+	list_del(&family->list);
+	return err;
+}
+EXPORT_SYMBOL(compat_genl_unregister_family);
+
 #endif /* LINUX_VERSION_CODE < KERNEL_VERSION(2,6,37) */