Commit 82ace47a authored by Thomas Graf's avatar Thomas Graf Committed by Thomas Graf
Browse files

[NETLINK]: Generic netlink receive queue processor 



Introduces netlink_run_queue() to handle the receive queue of
a netlink socket in a generic way. Processes as much as there
was in the queue upon entry and invokes a callback function
for each netlink message found. The callback function may
refuse a message by returning a negative error code but setting
the error pointer to 0 in which case netlink_run_queue() will
return with a qlen != 0.

Signed-off-by: default avatarThomas Graf <tgraf@suug.ch>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a8f74b22

include/net/netlink.h

+6 −0
Original line number Diff line number Diff line
@@ -183,6 +183,12 @@ struct nla_policy { 
	u16		minlen;

};



extern void		netlink_run_queue(struct sock *sk, unsigned int *qlen,

					  int (*cb)(struct sk_buff *,

						    struct nlmsghdr *, int *));

extern void		netlink_queue_skip(struct nlmsghdr *nlh,

					   struct sk_buff *skb);



extern int		nla_validate(struct nlattr *head, int len, int maxtype,

				     struct nla_policy *policy);

extern int		nla_parse(struct nlattr *tb[], int maxtype,

net/netlink/af_netlink.c

+91 −0
Original line number Diff line number Diff line
@@ -58,6 +58,7 @@ 


#include <net/sock.h>

#include <net/scm.h>

#include <net/netlink.h>



#define Nprintk(a...)

#define NLGRPSZ(x)	(ALIGN(x, sizeof(unsigned long) * 8) / 8)
@@ -1411,6 +1412,94 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err) 
	netlink_unicast(in_skb->sk, skb, NETLINK_CB(in_skb).pid, MSG_DONTWAIT);

}



static int netlink_rcv_skb(struct sk_buff *skb, int (*cb)(struct sk_buff *,

						     struct nlmsghdr *, int *))

{

	unsigned int total_len;

	struct nlmsghdr *nlh;

	int err;



	while (skb->len >= nlmsg_total_size(0)) {

		nlh = (struct nlmsghdr *) skb->data;



		if (skb->len < nlh->nlmsg_len)

			return 0;



		total_len = min(NLMSG_ALIGN(nlh->nlmsg_len), skb->len);



		if (cb(skb, nlh, &err) < 0) {

			/* Not an error, but we have to interrupt processing

			 * here. Note: that in this case we do not pull

			 * message from skb, it will be processed later.

			 */

			if (err == 0)

				return -1;

			netlink_ack(skb, nlh, err);

		} else if (nlh->nlmsg_flags & NLM_F_ACK)

			netlink_ack(skb, nlh, 0);



		skb_pull(skb, total_len);

	}



	return 0;

}



/**

 * nelink_run_queue - Process netlink receive queue.

 * @sk: Netlink socket containing the queue

 * @qlen: Place to store queue length upon entry

 * @cb: Callback function invoked for each netlink message found

 *

 * Processes as much as there was in the queue upon entry and invokes

 * a callback function for each netlink message found. The callback

 * function may refuse a message by returning a negative error code

 * but setting the error pointer to 0 in which case this function

 * returns with a qlen != 0.

 *

 * qlen must be initialized to 0 before the initial entry, afterwards

 * the function may be called repeatedly until qlen reaches 0.

 */

void netlink_run_queue(struct sock *sk, unsigned int *qlen,

		       int (*cb)(struct sk_buff *, struct nlmsghdr *, int *))

{

	struct sk_buff *skb;



	if (!*qlen || *qlen > skb_queue_len(&sk->sk_receive_queue))

		*qlen = skb_queue_len(&sk->sk_receive_queue);



	for (; *qlen; (*qlen)--) {

		skb = skb_dequeue(&sk->sk_receive_queue);

		if (netlink_rcv_skb(skb, cb)) {

			if (skb->len)

				skb_queue_head(&sk->sk_receive_queue, skb);

			else {

				kfree_skb(skb);

				(*qlen)--;

			}

			break;

		}



		kfree_skb(skb);

	}

}



/**

 * netlink_queue_skip - Skip netlink message while processing queue.

 * @nlh: Netlink message to be skipped

 * @skb: Socket buffer containing the netlink messages.

 *

 * Pulls the given netlink message off the socket buffer so the next

 * call to netlink_queue_run() will not reconsider the message.

 */

void netlink_queue_skip(struct nlmsghdr *nlh, struct sk_buff *skb)

{

	int msglen = NLMSG_ALIGN(nlh->nlmsg_len);



	if (msglen > skb->len)

		msglen = skb->len;



	skb_pull(skb, msglen);

}



#ifdef CONFIG_PROC_FS

struct nl_seq_iter {
@@ -1659,6 +1748,8 @@ out: 
core_initcall(netlink_proto_init);



EXPORT_SYMBOL(netlink_ack);

EXPORT_SYMBOL(netlink_run_queue);

EXPORT_SYMBOL(netlink_queue_skip);

EXPORT_SYMBOL(netlink_broadcast);

EXPORT_SYMBOL(netlink_dump_start);

EXPORT_SYMBOL(netlink_kernel_create);