[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: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index f3fb7e5..8c38ee6 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -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 @@
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 @@
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);