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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-21 08:19:28 +00:00
![Denis V. Lunev](/assets/img/avatar_default.png)
This patch make processing netlink user -> kernel messages synchronious. This change was inspired by the talk with Alexey Kuznetsov about current netlink messages processing. He says that he was badly wrong when introduced asynchronious user -> kernel communication. The call netlink_unicast is the only path to send message to the kernel netlink socket. But, unfortunately, it is also used to send data to the user. Before this change the user message has been attached to the socket queue and sk->sk_data_ready was called. The process has been blocked until all pending messages were processed. The bad thing is that this processing may occur in the arbitrary process context. This patch changes nlk->data_ready callback to get 1 skb and force packet processing right in the netlink_unicast. Kernel -> user path in netlink_unicast remains untouched. EINTR processing for in netlink_run_queue was changed. It forces rtnl_lock drop, but the process remains in the cycle until the message will be fully processed. So, there is no need to use this kludges now. Signed-off-by: Denis V. Lunev <den@openvz.org> Acked-by: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru> Signed-off-by: David S. Miller <davem@davemloft.net>
477 lines
11 KiB
C
477 lines
11 KiB
C
/*
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* connector.c
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*
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* 2004-2005 Copyright (c) Evgeniy Polyakov <johnpol@2ka.mipt.ru>
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* All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/list.h>
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#include <linux/skbuff.h>
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#include <linux/netlink.h>
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#include <linux/moduleparam.h>
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#include <linux/connector.h>
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#include <linux/mutex.h>
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#include <net/sock.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Evgeniy Polyakov <johnpol@2ka.mipt.ru>");
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MODULE_DESCRIPTION("Generic userspace <-> kernelspace connector.");
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static u32 cn_idx = CN_IDX_CONNECTOR;
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static u32 cn_val = CN_VAL_CONNECTOR;
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module_param(cn_idx, uint, 0);
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module_param(cn_val, uint, 0);
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MODULE_PARM_DESC(cn_idx, "Connector's main device idx.");
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MODULE_PARM_DESC(cn_val, "Connector's main device val.");
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static DEFINE_MUTEX(notify_lock);
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static LIST_HEAD(notify_list);
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static struct cn_dev cdev;
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int cn_already_initialized = 0;
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/*
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* msg->seq and msg->ack are used to determine message genealogy.
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* When someone sends message it puts there locally unique sequence
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* and random acknowledge numbers. Sequence number may be copied into
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* nlmsghdr->nlmsg_seq too.
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*
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* Sequence number is incremented with each message to be sent.
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*
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* If we expect reply to our message then the sequence number in
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* received message MUST be the same as in original message, and
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* acknowledge number MUST be the same + 1.
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*
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* If we receive a message and its sequence number is not equal to the
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* one we are expecting then it is a new message.
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*
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* If we receive a message and its sequence number is the same as one
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* we are expecting but it's acknowledgement number is not equal to
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* the acknowledgement number in the original message + 1, then it is
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* a new message.
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*
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*/
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int cn_netlink_send(struct cn_msg *msg, u32 __group, gfp_t gfp_mask)
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{
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struct cn_callback_entry *__cbq;
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unsigned int size;
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struct sk_buff *skb;
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struct nlmsghdr *nlh;
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struct cn_msg *data;
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struct cn_dev *dev = &cdev;
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u32 group = 0;
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int found = 0;
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if (!__group) {
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spin_lock_bh(&dev->cbdev->queue_lock);
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list_for_each_entry(__cbq, &dev->cbdev->queue_list,
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callback_entry) {
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if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
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found = 1;
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group = __cbq->group;
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}
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}
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spin_unlock_bh(&dev->cbdev->queue_lock);
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if (!found)
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return -ENODEV;
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} else {
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group = __group;
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}
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if (!netlink_has_listeners(dev->nls, group))
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return -ESRCH;
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size = NLMSG_SPACE(sizeof(*msg) + msg->len);
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skb = alloc_skb(size, gfp_mask);
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if (!skb)
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return -ENOMEM;
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nlh = NLMSG_PUT(skb, 0, msg->seq, NLMSG_DONE, size - sizeof(*nlh));
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data = NLMSG_DATA(nlh);
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memcpy(data, msg, sizeof(*data) + msg->len);
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NETLINK_CB(skb).dst_group = group;
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return netlink_broadcast(dev->nls, skb, 0, group, gfp_mask);
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nlmsg_failure:
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kfree_skb(skb);
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return -EINVAL;
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}
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EXPORT_SYMBOL_GPL(cn_netlink_send);
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/*
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* Callback helper - queues work and setup destructor for given data.
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*/
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static int cn_call_callback(struct cn_msg *msg, void (*destruct_data)(void *), void *data)
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{
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struct cn_callback_entry *__cbq, *__new_cbq;
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struct cn_dev *dev = &cdev;
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int err = -ENODEV;
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spin_lock_bh(&dev->cbdev->queue_lock);
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list_for_each_entry(__cbq, &dev->cbdev->queue_list, callback_entry) {
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if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
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if (likely(!work_pending(&__cbq->work) &&
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__cbq->data.ddata == NULL)) {
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__cbq->data.callback_priv = msg;
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__cbq->data.ddata = data;
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__cbq->data.destruct_data = destruct_data;
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if (queue_work(dev->cbdev->cn_queue,
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&__cbq->work))
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err = 0;
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} else {
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struct cn_callback_data *d;
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err = -ENOMEM;
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__new_cbq = kzalloc(sizeof(struct cn_callback_entry), GFP_ATOMIC);
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if (__new_cbq) {
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d = &__new_cbq->data;
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d->callback_priv = msg;
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d->callback = __cbq->data.callback;
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d->ddata = data;
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d->destruct_data = destruct_data;
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d->free = __new_cbq;
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INIT_WORK(&__new_cbq->work,
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&cn_queue_wrapper);
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if (queue_work(dev->cbdev->cn_queue,
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&__new_cbq->work))
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err = 0;
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else {
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kfree(__new_cbq);
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err = -EINVAL;
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}
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}
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}
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break;
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}
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}
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spin_unlock_bh(&dev->cbdev->queue_lock);
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return err;
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}
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/*
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* Skb receive helper - checks skb and msg size and calls callback
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* helper.
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*/
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static int __cn_rx_skb(struct sk_buff *skb, struct nlmsghdr *nlh)
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{
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u32 pid, uid, seq, group;
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struct cn_msg *msg;
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pid = NETLINK_CREDS(skb)->pid;
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uid = NETLINK_CREDS(skb)->uid;
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seq = nlh->nlmsg_seq;
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group = NETLINK_CB((skb)).dst_group;
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msg = NLMSG_DATA(nlh);
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return cn_call_callback(msg, (void (*)(void *))kfree_skb, skb);
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}
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/*
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* Main netlink receiving function.
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*
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* It checks skb and netlink header sizes and calls the skb receive
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* helper with a shared skb.
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*/
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static void cn_rx_skb(struct sk_buff *__skb)
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{
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struct nlmsghdr *nlh;
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u32 len;
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int err;
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struct sk_buff *skb;
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skb = skb_get(__skb);
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if (skb->len >= NLMSG_SPACE(0)) {
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nlh = nlmsg_hdr(skb);
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if (nlh->nlmsg_len < sizeof(struct cn_msg) ||
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skb->len < nlh->nlmsg_len ||
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nlh->nlmsg_len > CONNECTOR_MAX_MSG_SIZE) {
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kfree_skb(skb);
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goto out;
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}
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len = NLMSG_ALIGN(nlh->nlmsg_len);
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if (len > skb->len)
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len = skb->len;
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err = __cn_rx_skb(skb, nlh);
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if (err < 0)
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kfree_skb(skb);
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}
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out:
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kfree_skb(__skb);
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}
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/*
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* Notification routing.
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*
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* Gets id and checks if there are notification request for it's idx
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* and val. If there are such requests notify the listeners with the
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* given notify event.
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*
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*/
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static void cn_notify(struct cb_id *id, u32 notify_event)
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{
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struct cn_ctl_entry *ent;
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mutex_lock(¬ify_lock);
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list_for_each_entry(ent, ¬ify_list, notify_entry) {
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int i;
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struct cn_notify_req *req;
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struct cn_ctl_msg *ctl = ent->msg;
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int idx_found, val_found;
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idx_found = val_found = 0;
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req = (struct cn_notify_req *)ctl->data;
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for (i = 0; i < ctl->idx_notify_num; ++i, ++req) {
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if (id->idx >= req->first &&
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id->idx < req->first + req->range) {
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idx_found = 1;
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break;
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}
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}
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for (i = 0; i < ctl->val_notify_num; ++i, ++req) {
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if (id->val >= req->first &&
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id->val < req->first + req->range) {
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val_found = 1;
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break;
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}
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}
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if (idx_found && val_found) {
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struct cn_msg m = { .ack = notify_event, };
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memcpy(&m.id, id, sizeof(m.id));
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cn_netlink_send(&m, ctl->group, GFP_KERNEL);
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}
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}
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mutex_unlock(¬ify_lock);
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}
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/*
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* Callback add routing - adds callback with given ID and name.
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* If there is registered callback with the same ID it will not be added.
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*
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* May sleep.
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*/
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int cn_add_callback(struct cb_id *id, char *name, void (*callback)(void *))
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{
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int err;
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struct cn_dev *dev = &cdev;
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if (!cn_already_initialized)
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return -EAGAIN;
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err = cn_queue_add_callback(dev->cbdev, name, id, callback);
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if (err)
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return err;
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cn_notify(id, 0);
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return 0;
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}
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EXPORT_SYMBOL_GPL(cn_add_callback);
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/*
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* Callback remove routing - removes callback
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* with given ID.
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* If there is no registered callback with given
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* ID nothing happens.
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*
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* May sleep while waiting for reference counter to become zero.
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*/
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void cn_del_callback(struct cb_id *id)
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{
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struct cn_dev *dev = &cdev;
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cn_queue_del_callback(dev->cbdev, id);
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cn_notify(id, 1);
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}
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EXPORT_SYMBOL_GPL(cn_del_callback);
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/*
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* Checks two connector's control messages to be the same.
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* Returns 1 if they are the same or if the first one is corrupted.
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*/
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static int cn_ctl_msg_equals(struct cn_ctl_msg *m1, struct cn_ctl_msg *m2)
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{
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int i;
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struct cn_notify_req *req1, *req2;
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if (m1->idx_notify_num != m2->idx_notify_num)
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return 0;
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if (m1->val_notify_num != m2->val_notify_num)
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return 0;
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if (m1->len != m2->len)
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return 0;
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if ((m1->idx_notify_num + m1->val_notify_num) * sizeof(*req1) !=
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m1->len)
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return 1;
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req1 = (struct cn_notify_req *)m1->data;
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req2 = (struct cn_notify_req *)m2->data;
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for (i = 0; i < m1->idx_notify_num; ++i) {
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if (req1->first != req2->first || req1->range != req2->range)
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return 0;
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req1++;
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req2++;
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}
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for (i = 0; i < m1->val_notify_num; ++i) {
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if (req1->first != req2->first || req1->range != req2->range)
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return 0;
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req1++;
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req2++;
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}
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return 1;
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}
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/*
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* Main connector device's callback.
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*
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* Used for notification of a request's processing.
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*/
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static void cn_callback(void *data)
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{
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struct cn_msg *msg = data;
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struct cn_ctl_msg *ctl;
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struct cn_ctl_entry *ent;
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u32 size;
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if (msg->len < sizeof(*ctl))
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return;
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ctl = (struct cn_ctl_msg *)msg->data;
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size = (sizeof(*ctl) + ((ctl->idx_notify_num +
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ctl->val_notify_num) *
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sizeof(struct cn_notify_req)));
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if (msg->len != size)
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return;
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if (ctl->len + sizeof(*ctl) != msg->len)
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return;
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/*
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* Remove notification.
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*/
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if (ctl->group == 0) {
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struct cn_ctl_entry *n;
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mutex_lock(¬ify_lock);
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list_for_each_entry_safe(ent, n, ¬ify_list, notify_entry) {
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if (cn_ctl_msg_equals(ent->msg, ctl)) {
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list_del(&ent->notify_entry);
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kfree(ent);
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}
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}
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mutex_unlock(¬ify_lock);
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return;
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}
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size += sizeof(*ent);
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ent = kzalloc(size, GFP_KERNEL);
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if (!ent)
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return;
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ent->msg = (struct cn_ctl_msg *)(ent + 1);
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memcpy(ent->msg, ctl, size - sizeof(*ent));
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mutex_lock(¬ify_lock);
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list_add(&ent->notify_entry, ¬ify_list);
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mutex_unlock(¬ify_lock);
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}
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static int __devinit cn_init(void)
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{
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struct cn_dev *dev = &cdev;
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int err;
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dev->input = cn_rx_skb;
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dev->id.idx = cn_idx;
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dev->id.val = cn_val;
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dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR,
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CN_NETLINK_USERS + 0xf,
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dev->input, NULL, THIS_MODULE);
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if (!dev->nls)
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return -EIO;
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dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
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if (!dev->cbdev) {
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if (dev->nls->sk_socket)
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sock_release(dev->nls->sk_socket);
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return -EINVAL;
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}
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cn_already_initialized = 1;
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err = cn_add_callback(&dev->id, "connector", &cn_callback);
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if (err) {
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cn_already_initialized = 0;
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cn_queue_free_dev(dev->cbdev);
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if (dev->nls->sk_socket)
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sock_release(dev->nls->sk_socket);
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return -EINVAL;
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}
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return 0;
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}
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static void __devexit cn_fini(void)
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{
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struct cn_dev *dev = &cdev;
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cn_already_initialized = 0;
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cn_del_callback(&dev->id);
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cn_queue_free_dev(dev->cbdev);
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if (dev->nls->sk_socket)
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sock_release(dev->nls->sk_socket);
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}
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subsys_initcall(cn_init);
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module_exit(cn_fini);
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