Re: [PATCH v4] staging: r8188eu: fix too many leading tabs

[Joash Naidoo <joash.n09@gmail.com>]

Greg KH <gregkh@linuxfoundation.org> writes:

> On Wed, Sep 28, 2022 at 06:20:28PM +0200, Joash Naidoo wrote:
>> > But also, shouldn't you just be using the ip_hdr() call 
>> > instead of doing
>> > the crazy cast above?
>>
>> I would need to investigate and test first before commenting. 
>> If a change
>> had to be made, I believe it will go in a separate patch?
>
> Yes, that would be good to do as a patch series.
>
> thanks,
>
> greg k-h

Hi all

I want to investigate Greg's suggestion to replace the original 
code's iph cast with ip_hdr(). Looking into the ip_hdr() function 
it seems it effectively casts skb->head + skb->network_header 
property (See [1, 2]) whereas the original code casts skb->data + 
ETH_HLEN [3]. My goal was to use printk statements to see if 
they're equivalent before making any actual changes.

Could anyone advise to a high level action which will trigger the 
dhcp_flag_bcast() function, as seen in my patch. I have limited 
knowledge but I would imagine this function is called when the 
device broadcasts an IP address request from the DHCP server. I am 
using dhcpcd as a client and I have tried to manually trigger this 
action by deleting device's lease file and restarting dhcpcd. 
Among trying other basic things, I have been unsuccessful at 
triggering this function.

Looking further up the code at the rtw_xmit() function [4], I 
learnt the following. Perhaps understanding br_port may also help 
me.

	void *br_port = NULL;
	br_port = rcu_dereference(padapter->pnetdev->rx_handler_data); 
	// <-- this returns 0x00

	if (br_port && check_fwstate(pmlmepriv, WIFI_STATION_STATE | 
	WIFI_ADHOC_STATE)) { // <-- false because of br_port, second 
	condition is true
		res = rtw_br_client_tx(padapter, ppkt); // <-- later calls 
		the dhcp_flag_bcast() See [5]

		if (res == -1) {
			rtw_free_xmitframe(pxmitpriv, pxmitframe);
			return -1;
		}
	}

[1] 
https://elixir.bootlin.com/linux/v6.0-rc5/source/include/linux/ip.h#L19
[2] 
https://elixir.bootlin.com/linux/v6.0-rc5/source/include/linux/skbuff.h#L2819
[3] 
https://elixir.bootlin.com/linux/v6.0-rc5/source/drivers/staging/r8188eu/core/rtw_br_ext.c#L611
[4] 
https://elixir.bootlin.com/linux/v6.0-rc5/source/drivers/staging/r8188eu/core/rtw_xmit.c#L1670
[5] 
https://elixir.bootlin.com/linux/v6.0-rc5/source/drivers/staging/r8188eu/core/rtw_xmit.c#L1598

Thank you all for your time and support.

Kind regards,
Joash