IPPROTO_RAW wrongly used with AF_PACKET

[go2sh]

Describe the bug
Zephyr specifies the use of IPPROTO_RAW with AF_PACKET sockets. This is not in line how Linux specifies this. `IPPROTO_RAW´ is specified as sub type for IP frames. [1] Used as EtherType this specifies an old length field type. [2]

To Reproduce
Use AF_PACKET socket.

Expected behavior
IPPROTO_RAW is not treated as a protocol with AF_PACKET sockets, but with AF_INET/AF_INET6 through a SOCK_RAW socket.

Impact
Incompatibility (and maintaining this). overhead when using AF_PACKET.

Logs and console output
None.

Environment (please complete the following information):

• OS: Linux
• Toolchain: Zephyr SDK
• Commit SHA: df53184

Additional context
None.

[jukkar]

The original plan was to be aligned with Linux here, but it seems that target was missed then. I suppose you are talking about this line

zephyr/subsys/net/lib/sockets/sockets_packet.c

Line 56 in ab7a6de

proto = IPPROTO_RAW;

I think we can easily remove that one, the original plan was to have some default value if user gives proto as 0 which is not a valid value.

[jukkar]

More info. According to this page https://stackoverflow.com/questions/49309029/confusion-with-af-inet-with-sock-raw-as-the-socket-type-v-s-af-packet-with-so the protocol field should be allowed to be 0 with AF_PACKET.

[go2sh]

It's not only this line. This adds additional overhead:

zephyr/subsys/net/ip/net_core.c

Line 131 in 658f935

ret = net_packet_socket_input(pkt, IPPROTO_RAW);

[go2sh]

More info. According to this page https://stackoverflow.com/questions/49309029/confusion-with-af-inet-with-sock-raw-as-the-socket-type-v-s-af-packet-with-so the protocol field should be allowed to be 0 with AF_PACKET.

Here is also more info: https://man7.org/linux/man-pages/man7/raw.7.html
TLDR:
IPPROTO_RAW means send only sockets and the IP header needs to be provided by the user.

[jukkar]

I think raw7 manual page only talks about AF_INET/6 sockets, not AF_PACKET ones.

[go2sh]

https://man7.org/linux/man-pages/man7/packet.7.html Doesn't talk about IPPROTO_RAW either.

AF_PACKET is a layer 2 socket and IPPROTO_RAW is used at l3/l4 sockets.

[jukkar]

Doesn't talk about IPPROTO_RAW either.

Yes, I noticed the same, it does not talk about IPPROTO_RAW. Only place IPPROTO_RAW is mentioned is in raw(7).