Function pointer dev->hard_header (in net_init.c) is initialised to "eth_header" (def in ethernet/eth.c) in func "ether_setup" called from "init_etherdev". we call init_etherdev from our driver to initialise dev. The function hard_header is called from ip_queue_xmit. But I am rather confused the way its being called. if(skb_headroom(skb) < dev->hard_header_len && dev->hard_header) where hard_header is a function pointer. Declared as below int (*hard_header) (struct sk_buff *skb, struct device *dev, unsigned short type, void *daddr, void *saddr, unsigned len); Can anybody explain how the required arguements are passed to hardware header. The hard_header is the function which finally pushes hardware header into our skb.Pls correct me in case I'm wrong. <mrwangxc@263.net> wrote: > >Hi all, > > I am trying to understand the tcp/ip implementation > >in Linux. > >My doubt is where the ethernet header is being formed > >for the outgoing packet. > >I was able to know that it is being cached in dst_entry > >as "struct hh_cache" held by both neighbour table as well as rtable. > >This reduces the time taken to form ethernet header > >for each and every packet going out. > > > >But I was not able to see where exactly the cached ethernet header > is > >being pushed into sk_buff holding our packet. > > > >As I see eth_header(ethernet/eth.c) pushes the header into > >sk_buff but this func is not being called by anybody? > Loopback.c (linux\drivers\net): dev->hard_header = eth_header; > Net_init.c (linux\drivers\net): dev->hard_header = eth_header; > > they must have used the "dev->hard_header" interface(there are a lot > of such "interface" in the tcp/ip stack) > u can trace it back to find out how these things happen > & i'm glad to hear about the things you find out, more details,better. > > > >Can any body help? __________________________________________________ FREE voicemail, email, and fax...all in one place. Sign Up Now! http://www.onebox.com -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ IRC Channel: irc.openprojects.net / #kernelnewbies Web Page: http://www.kernelnewbies.org/
