Re: Is mac address reference safe w/ zero copy?

["David S. Miller" <davem@xxxxxxxxxx>]

Rusty Russell writes:
 > Hi Dave, et al,
 > 
 >      The following code in route.c:ip_route_input_slow()
 > 
 >              if (dev->hard_header_len) {
 >                      int i;
 >                      unsigned char *p = skb->mac.raw;
 >                      printk(KERN_WARNING "ll header: ");
 >                      for (i=0; i<dev->hard_header_len; i++, p++) {
 >                              printk("%02x", *p);
 > 
 >      Is this safe w/ paged skbs?  Can I assume this in the ipt_mac
 > mac-address-matching netfilter module (which can only be called on
 > incoming or forwarded packets)?

It is safe unless you can show a place where an ethernet header
lands somewhere other than skb->data on input :-)

Format of input SKBs really have not changed at device header level.

Later,
David S. Miller
davem@xxxxxxxxxx