Thanks Rami, it helps a lot. I'm using SocketCAN as reference for doing this, and I see AF_CAN at socket.h. I saw that protocol family create is called by __sock_create(). Also found that proto_ops bind is used (in the example of the CAN) to find the interface where the communication realy happens.. I am wondering if is possible to achieve my goal with and only with out of tree module. I'm planing to get this merged at main tree anyway, but first I would like to keep it out ou tree until is ready... Cheers,  2016-03-26 8:04 GMT-03:00 Rami Rosen <roszenrami@gmail.com>:

Hi Daniel,

Following are answers for several of your questions: Adding a protocol in Linux is done first by defining a protocol, and then registering it with the proto_register() method: http://lxr.free-electrons.com/source/net/core/sock.c#L2815 For that you need to define a proto object; for TCPv4 it is done thus, for example: http://lxr.free-electrons.com/source/net/ipv4/tcp_ipv4.c#L2315

Defining a protocol is not enough, you should also register a protocol handler for this protocol. Defining a protocol handler is done first by defining a packet_type object of this protocol and then defining a callback for this packet_type. So for example, for IPv4, a packet_type object called ip_packet_type is defined in http://lxr.free-electrons.com/source/net/ipv4/af_inet.c#L1677

The protocol handler for this packet type is ip_rcv(): http://lxr.free-electrons.com/source/net/ipv4/ip_input.c#L378

This protocol is registered with dev_add_pack(): http://lxr.free-electrons.com/source/net/core/dev.c#L397

So, for example, for IPv4 it is done in inet_init(): http://lxr.free-electrons.com/source/net/ipv4/af_inet.c#L1791

Apart from the protocol handler, a unique Ethernet type should be defined for this protocol; for IPv4 we have 0x0800 (ETH_P_IP) http://lxr.free-electrons.com/source/include/uapi/linux/if_ether.h#L46 and for the ARP protocol we have 0x0806 (ETH_P_ARP), and so on.

The Ethernet type in the Ethernet header represents the protocol assigned to this packet.

The net_device_ops structure is not related, it merely represents the interface of the of the kernel representation of network device (a net_device object) to userspace, for userspace operations like setting the MTU, setting the MAC address, bringing the device up and down, putting the device in promiscuous mode, and more.

Hope this helps!

Regards, Rami Rosen http://ramirose.wix.com/ramirosen

On 26 March 2016 at 05:00, Daniel. <danielhilst@gmail.com> wrote:

...

Hi everybody,

I'm planing to write a socket API for Nordic's nRF24L01+ and I was digging on socket code and find all supported protocols at include/linux/socket.h with all that #define AF_x y. So my questions are:

1) Is it possible to write a new protocol for linux with an out of tree module without modifing socket.h file? 2) Could netlink socket be used to solve this? .. and 3) I saw that there is net_device_ops and proto_ops. How they are tied together?

Thanks in advance and Best regards,

-- "Do or do not. There is no try" Yoda Master

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