netdev - Re: [PATCH updated] net: add ability to clear per-interface network statistics via procfs

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Message-Id: <20080516.130309.258561311.davem@davemloft.net>
Date:	Fri, 16 May 2008 13:03:09 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	dada1@...mosbay.com
Cc:	jimi@...x.net, netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH updated] net: add ability to clear per-interface
 network statistics via procfs

From: Eric Dumazet <dada1@...mosbay.com>
Date: Fri, 16 May 2008 18:20:58 +0200

netdev CC:'d, people please...  Eric, you in particular know
better :-)))

> James Cammarata a écrit :
> > From: James Cammarata <jimi@...x.net>
> >
> > Added the ability to write to /proc/net/dev in order to clear the 
> > interface counters for a given interface.  The ability to zero out 
> > counters (especially the error counters) is extremely useful when 
> > troubleshooting interface issues.  Now diffed against 2.6.25.4, and 
> > added some sanity checking.
> >
> Hello James
> 
> 1) Every call to get_proc_net() should be paired with a call to 
> put_net(), or else you  leak  struct net.
> 
> 2) I am not sure this is the right way to do this... Did you consider to 
> extend ethtool instead ?
> 
> > Syntax:
> >  echo 'net clear-stats ifdev' > /proc/net/dev
> > Where "ifdev" is the device name you wish to clear.
> >
> > This code is based mainly on the code found in drivers/scsi/scsi_proc.c
> >
> > Signed-off-by: James Cammarata <jimi@...x.net>
> > ---
> >
> > --- linux-2.6.25.4/net/core/dev.c       2008-05-15 10:00:12.000000000 
> > -0500
> > +++ linux-2.6.25.4-jcammara/net/core/dev.c      2008-05-16 
> > 07:02:48.000000000 -0500
> > @@ -2455,2 +2455,78 @@
> >
> > +/**
> > + * proc_net_dev_write - handle writes to /proc/net/dev
> > + * @file: not used
> > + * @buf: buffer to write
> > + * @length: length of buf, at most PAGE_SIZE
> > + * @ppos: not used
> > + *
> > + * Description: this provides a mechanism to clear statistics on a
> > + * per-interface basis
> > + * "echo 'net clear-stats ifdev' >/proc/net/dev"
> > + * with  "ifdev" replaced by the device name you wish to clear.
> > + *
> > + */
> > +static ssize_t proc_net_dev_write(struct file *file, const char 
> > __user *buf,
> > +                                  size_t length, loff_t *ppos)
> > +{
> > +        char *buffer, *p;
> > +        char devname[IFNAMSIZ];
> > +        struct net *net;
> > +        struct net_device *dev;
> > +        int err;
> > +
> > +        if (!buf || length > PAGE_SIZE)
> > +                return -EINVAL;
> > +
> > +        buffer = (char *)__get_free_page(GFP_KERNEL);
> > +        if (!buffer)
> > +                return -ENOMEM;
> > +
> > +        err = -EFAULT;
> > +        if (copy_from_user(buffer, buf, length))
> > +                goto out;
> > +
> > +        err = -EINVAL;
> > +        if (length < PAGE_SIZE)
> > +                buffer[length] = '\0';
> > +        else if (buffer[PAGE_SIZE-1])
> > +                goto out;
> > +
> > +        err = -ENXIO;
> > +        net = get_proc_net(file->f_dentry->d_inode);
> > +        if (!net)
> > +                goto out;
> > +
> > +        /*
> > +         * Usage: echo "net clear-stats ifdev" >/proc/net/dev
> > +         * with  "ifdev" replaced by the device name you wish to clear.
> > +         */
> > +        if (!strncmp("net clear-stats",buffer,15)) {
> > +                p = buffer + 16;
> > +                if(sscanf(p,"%16s",devname)>0) {
> > +                        dev = dev_get_by_name(net,devname);
> > +                        if (dev) {
> > +                                if (dev->get_stats) {
> > +                                        struct net_device_stats *stats =
> > +                                               dev->get_stats(dev);
> > +                                        memset(stats,0,
> > +                                               sizeof(struct 
> > net_device_stats));
> > +                                }
> > +                                dev_put(dev);
> > +                        }
> > +                }
> > +        }
> > +
> > +        /*
> > +         * convert success returns so that we return the
> > +         * number of bytes consumed.
> > +         */
> > +        if (!err)
> > +                err = length;
> > +
> Here probably, you should add
> 
>     put_net(net);
> 
> > + out:
> > +        free_page((unsigned long)buffer);
> > +        return err;
> > +}
> > +
> > static void *softnet_seq_start(struct seq_file *seq, loff_t *pos)
> > @@ -2498,2 +2574,3 @@
> >        .read    = seq_read,
> > +        .write   = proc_net_dev_write,
> >        .llseek  = seq_lseek,
> >
> >
> 
> 
> 
> 
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