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
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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On Fri, 25 Mar 2016 23:00:48 -0300, "Daniel." said:
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?
Rami Rosen gave a good outline of what's needed. But the *first* question you should ask is why a hardware device needs its own socket API rather than re-using an existing one. Basically, if it's an intelligent enough device or SOC, you should be able to get it to talk at least UDP or something. And if it's not that smart, maybe you shouldn't be trying to use sockets to talk to it. So what are the reasons you're doing a new socket API instead of using the existing stuff?
Enviado do meu smartphone BlackBerry 10. Mensagem original De: Valdis.Kletnieks@vt.edu Enviada: sábado, 26 de março de 2016 16:59 Para: Daniel. Cc: kernelnewbies Assunto: Re: Adding new protocol to linux. On Fri, 25 Mar 2016 23:00:48 -0300, "Daniel." said:
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?
Rami Rosen gave a good outline of what's needed. But the *first* question you should ask is why a hardware device needs its own socket API rather than re-using an existing one. Basically, if it's an intelligent enough device or SOC, you should be able to get it to talk at least UDP or something. And if it's not that smart, maybe you shouldn't be trying to use sockets to talk to it. So what are the reasons you're doing a new socket API instead of using the existing stuff? Hi Valdis, thanks for the answer. The big problem here is that this piece of hardware has really tiny payloads, only 32 bytes long and is not of standard type. Also I want to add some routing bits, the final goal is to have something like xbee but GPL and cheaper. I thought to use IP at first but the hw payloads are too small, so I think in writing a new protocol module and then I found the socket.h file. Thanks for your reply Cheers
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Valdis.Kletnieks＠vt.edu