[RFC][PATCH 1/3] netlink check sender

[Chris Wright <chrisw@xxxxxxxx>]

* Add check_sender callback to struct netlink_opt.
* Add netlink_kernel_create_check() to register that callback, and turn
  netlink_kernel_create() into a simple wrapper around that.
* Invoke callback when set to verify sender in sender's context.

===== net/netlink/af_netlink.c 1.69 vs edited =====
--- 1.69/net/netlink/af_netlink.c       2005-01-21 12:25:32 -08:00
+++ edited/net/netlink/af_netlink.c     2005-02-11 18:05:59 -08:00
@@ -71,6 +71,7 @@ struct netlink_opt
        struct netlink_callback *cb;
        spinlock_t              cb_lock;
        void                    (*data_ready)(struct sock *sk, int bytes);
+       int                     (*check_sender)(struct sk_buff *skb);
 };
 
 #define nlk_sk(__sk) ((struct netlink_opt *)(__sk)->sk_protinfo)
@@ -636,9 +637,17 @@ int netlink_attachskb(struct sock *sk, s
 int netlink_sendskb(struct sock *sk, struct sk_buff *skb, int protocol)
 {
        struct netlink_opt *nlk;
-       int len = skb->len;
-
+       int err, len = skb->len;
+       
        nlk = nlk_sk(sk);
+
+       printk("%s: %s(%d) send_check %p\n", __FUNCTION__, current->comm, 
current->pid, nlk->check_sender);
+       if (nlk->check_sender)
+               if ((err = nlk->check_sender(skb))) {
+                       netlink_detachskb(sk, skb);
+                       return err;
+               }
+
 #ifdef NL_EMULATE_DEV
        if (nlk->handler) {
                skb_orphan(skb);
@@ -1033,7 +1042,8 @@ static void netlink_data_ready(struct so
  */
 
 struct sock *
-netlink_kernel_create(int unit, void (*input)(struct sock *sk, int len))
+netlink_kernel_create_check(int unit, void (*input)(struct sock *sk, int len),
+                           int (*check)(struct sk_buff *skb))
 {
        struct socket *sock;
        struct sock *sk;
@@ -1053,8 +1063,10 @@ netlink_kernel_create(int unit, void (*i
        }
        sk = sock->sk;
        sk->sk_data_ready = netlink_data_ready;
-       if (input)
+       if (input) {
                nlk_sk(sk)->data_ready = input;
+               nlk_sk(sk)->check_sender = check;
+       }
 
        if (netlink_insert(sk, 0)) {
                sock_release(sock);
@@ -1459,7 +1471,7 @@ MODULE_ALIAS_NETPROTO(PF_NETLINK);
 EXPORT_SYMBOL(netlink_ack);
 EXPORT_SYMBOL(netlink_broadcast);
 EXPORT_SYMBOL(netlink_dump_start);
-EXPORT_SYMBOL(netlink_kernel_create);
+EXPORT_SYMBOL(netlink_kernel_create_check);
 EXPORT_SYMBOL(netlink_register_notifier);
 EXPORT_SYMBOL(netlink_set_err);
 EXPORT_SYMBOL(netlink_set_nonroot);
===== include/linux/netlink.h 1.23 vs edited =====
--- 1.23/include/linux/netlink.h        2005-02-06 21:59:39 -08:00
+++ edited/include/linux/netlink.h      2005-02-11 14:56:23 -08:00
@@ -116,7 +116,11 @@ struct netlink_skb_parms
 #define NETLINK_CREDS(skb)     (&NETLINK_CB((skb)).creds)
 
 
-extern struct sock *netlink_kernel_create(int unit, void (*input)(struct sock 
*sk, int len));
+extern struct sock *netlink_kernel_create_check(int unit, void (*input)(struct 
sock *sk, int len), int (*check)(struct sk_buff *skb));
+static inline struct sock *netlink_kernel_create(int unit, void 
(*input)(struct sock *sk, int len)) 
+{
+       return netlink_kernel_create_check(unit, input, NULL);
+}
 extern void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err);
 extern int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 pid, 
int nonblock);
 extern int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, __u32 pid,