Could you provide the piece(s) of code where kernel does this type of operation ? Of course just suggest me some file where search, I am really curios and I would like understand better this question but at the same time I am unable to find the files where look for.
I had a written a Realtek ethernet card driver long time back (its been almost 6yrs since) for my own curiosity. So my memory right now is sketchy! :) You can start off by gong through the n/w device driver for some card (eg: drivers/net/8139too.c) and work your way up the stack (next you can look at net/ipv4/ip_input.c). The basic idea is that when a packet is rx'ed by the n/w device, it creates a sk_buff (socket buffer) and passes this up the stack where it's processed by the various protocol layers (IP, TCP etc). Though I'm not certain if the n/w device driver populates the various skb fields in the n/w or host byte order. Only inspecting the code will tell. HTH, -mandeep
Many thanks, Pietro.
-----Original Message----- From: Mandeep Sandhu [mailto:mandeepsandhu.chd@gmail.com] Sent: lunedì 15 ottobre 2012 10:33 To: Pietro Paolini Cc: kernelnewbies@kernelnewbies.org Subject: Re: Network Byte order not reached reading from a sock RAW
On Mon, Oct 15, 2012 at 1:16 PM, Pietro Paolini <P.Paolini@ext.adbglobal.com> wrote:
Hello, Thanks for your answer, my question is why when I read from the buffer data is already in host byte order and not in network byte order.
The 'raw' payload in your packet might still be in the n/w byte order and you will have to convert it using the ntoh*() functions (I'm not 100% sure about this though).
CMIIW, as I haven't touched sockets in a long time! :)
HTH, -mandeep
Thanks Pietro Paolini.
From: Mandeep Sandhu [mailto:mandeepsandhu.chd@gmail.com] Sent: sabato 13 ottobre 2012 05:30 To: Pietro Paolini Cc: kernelnewbies@kernelnewbies.org Subject: Re: Network Byte order not reached reading from a sock RAW
On Oct 12, 2012 9:36 PM, "Pietro Paolini" <P.Paolini@ext.adbglobal.com> wrote:
Hello,
I am struggling with the byte order question on a x86_32 arch, I am doing some modifications on a program which actually works fine on a MIPS arch.
I do a reading from a RAW socket in this way:
/* Configure socket */ if ((fd = socket(AF_INET, SOCK_RAW, IPPROTO_IGMP)) < 0) { perror("Error on socket creation, exit"); exit(1); } .... if (setsockopt(fd, IPPROTO_IP, IP_PKTINFO, (void *)&va, sizeof(va))) { perror("Error on setsockopt, exit"); exit(1); } va = 0; .... .... struct msghdr mhdr; struct __in_pktinfo *pktinfo = NULL; ... ... nrd = recvmsg(env->mrouter_fd, &mhdr, 0); ... ip = (struct iphdr *)iov.iov_base;
When I print the saddr (or daddr) of the received ip packet it is printed as host byte order instead of what I am expecting, the network byte order. I can just use the htonl() family functions for solve the problem but I would like understand if it is the normal behavior or if there is an issues on my code, or if the device driver of my NIC can influence the question.
I think you should use ntoh*() functions when accessing data rx'ed from the n/w. Network byte order is big endian and your host is little endian, so you'll have convert it to the right order before accessing. You should use hton*() functions when tx'ing data. CMIIW. HTH, -mandeep
Many thanks, Pietro.
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies