On Fri, Apr 10, 2009 at 4:12 AM, Thierry <chocapiiic.tiery@xxxxxxxxx> wrote:
> Hi,
>
> I have tried to change groupId, with different value, but there should
> be somethings wrong: the userspace prgm doesn't receive message.
> I would like to know if there is a plugin for tcpdump or an way of
> capture trafic on netlink socket, just like usual network socket in
> order to see were is my problem: in kernel space code or userspace
> code.
> My program code is attached, with english commit (sorry for last mail).
> I have also tried my code on differents kernel (redhat 4.4 with kernel
> 2.6.9-42.ELsmp, centos52 kernel 2.6.18-92.1.22).
>
> If there is other ways to send information from kernel space to user space...
> My aim is to capture data trafic from infiniband and dump trafic, for
> example in a netlink socket. Then I will be able with a userspace code
> to translate informations in .cap files.
> Thats why I think netlink_broadcast is a good idea.
>
> I will be always looking at kernelnewbie mailinglsit for several month,
>
> Regards,
>
> Thierry
>
>
>
> --------------
> kernel-level code
>
>
> #include <linux/config.h>
> #include <linux/socket.h>
> #include <linux/kernel.h>
> #include <linux/module.h>
> #include <linux/netlink.h>
> #include <net/sock.h>
>
> #define NETLINK_IB 24
> #define MAX_PAYLOAD 1024
> #define GROUP_IB 59
>
>
> static struct sock *nl_sk = NULL;
>
> static void nl_ib_data_ready (struct sock *sk, int len)
> {
> wake_up_interruptible(sk->sk_sleep);
> }
>
> static void netlink_ib_open()
> {
> struct sk_buff *skb = NULL;
> struct nlmsghdr *nlh = NULL;
> int err;
> u32 pid;
>
> //Socket_create
> nl_sk = netlink_kernel_create(NETLINK_IB, GROUP_IB, nl_ib_data_ready,
> THIS_MODULE);
>
> skb = alloc_skb(NLMSG_SPACE(MAX_PAYLOAD),GFP_KERNEL);
> nlh = (struct nlmsghdr *)skb->data;
>
> nlh->nlmsg_len = NLMSG_SPACE(MAX_PAYLOAD);
> nlh->nlmsg_pid = 0; //from kernel
> nlh->nlmsg_flags = 0;
>
> strcpy(NLMSG_DATA(nlh), "Message from kernel ");
> NETLINK_CB(skb).pid = 0;
> NETLINK_CB(skb).dst_pid = 0; //Multicast
> NETLINK_CB(skb).dst_group = GROUP_IB;
>
> //data send
> printk( KERN_ALERT "data sent\n");
> netlink_broadcast(nl_sk, skb, 0, GROUP_IB, GFP_KERNEL);
> sock_release(nl_sk->sk_socket);
> }
check this out:
http://www.linuxjournal.com/article/7356
read the comment, amazingly, someone else HAVE EXACTLY THE SAME
PROBLEM as yours, and his comment:
========================
here is missed one importang thing:
before strcpy we should call
skb_put(skb, NLMSG_SPACE(MAX_PAYLOAD))
or change
nlh = (struct nlmsghdr *)skb->data;
nlh->nlmsg_len = NLMSG_SPACE(MAX_PAYLOAD);
nlh->nlmsg_pid = 0; /* from kernel */
nlh->nlmsg_flags = 0;
==========================
and looking into kernel source:
s = skb_copy_expand(skb, 8, 0, GFP_ATOMIC);
skb_push(s, 8);
s->data[0] = 'z';
s->data[1] = 'y';
s->data[2] = 'd';
s->data[3] = 'a';
s->data[4] = 's';
printk("len1=%d, len2=%d", skb->len, s->len);
netlink_broadcast(rtnl, s, 0, RTMGRP_LINK, GFP_ATOMIC);
and this:
/*ÌîдÊý¾Ý±¨Ïà¹ØÐÅÏ¢*/
nlh = NLMSG_PUT(skb, 0, 0, WAI_K_MSG, size-sizeof(*nlh));
pos = NLMSG_DATA(nlh);
memset(pos, 0, len);
/*´«Êäµ½Óû§¿Õ¼äµÄÊý¾Ý*/
memcpy(pos, msg, len);
/*¼ÆËã¾¹ý×Ö½Ú¶ÔÆäºóµÄÊý¾Ýʵ¼Ê³¤¶È*/
nlh->nlmsg_len = skb->tail - old_tail;
NETLINK_CB(skb).dst_group = COMMTYPE_GROUP;
netlink_broadcast(netlink_sk, skb, 0, COMMTYPE_GROUP, GFP_ATOMIC);
all having the same pattern as the comment.
Hopefully this helps.
--
Regards,
Peter Teoh
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