e1000e: use ip_hdrlen() instead of bit shift

[PATCH] e1000e: use ip_hdrlen() instead of bit shift

Posted by Moon Yeounsu 1 year, 6 months ago

There's no reason to use bit shift to find the UDP header.
It's not intuitive and it reinvents well-defined functions.

Signed-off-by: Moon Yeounsu <yyyynoom@gmail.com>
---
 drivers/net/ethernet/intel/e1000e/netdev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
index 360ee26557f7..07c4cf84bdf3 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -5731,7 +5731,7 @@ static int e1000_transfer_dhcp_info(struct e1000_adapter *adapter,
 		if (ip->protocol != IPPROTO_UDP)
 			return 0;
 
-		udp = (struct udphdr *)((u8 *)ip + (ip->ihl << 2));
+		udp = (struct udphdr *)((u8 *)ip + ip_hdrlen(skb));
 		if (ntohs(udp->dest) != 67)
 			return 0;
 
-- 
2.45.2

Re: [PATCH] e1000e: use ip_hdrlen() instead of bit shift

Posted by Florian Westphal 1 year, 6 months ago

Moon Yeounsu <yyyynoom@gmail.com> wrote:
> There's no reason to use bit shift to find the UDP header.
> It's not intuitive and it reinvents well-defined functions.
> 
> Signed-off-by: Moon Yeounsu <yyyynoom@gmail.com>
> ---
>  drivers/net/ethernet/intel/e1000e/netdev.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
> index 360ee26557f7..07c4cf84bdf3 100644
> --- a/drivers/net/ethernet/intel/e1000e/netdev.c
> +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
> @@ -5731,7 +5731,7 @@ static int e1000_transfer_dhcp_info(struct e1000_adapter *adapter,
>  		if (ip->protocol != IPPROTO_UDP)
>  			return 0;
>  
> -		udp = (struct udphdr *)((u8 *)ip + (ip->ihl << 2));
> +		udp = (struct udphdr *)((u8 *)ip + ip_hdrlen(skb));

This helper needs skb_network_header being set up correctly, are you
sure thats the case here?  ip pointer is fetched via data + 14 right
above, so it doesn't look like this would work.

Re: [PATCH] e1000e: use ip_hdrlen() instead of bit shift

Posted by Moon Yeounsu 1 year, 6 months ago

On Thu, Aug 1, 2024 at 11:06 PM Florian Westphal <fw@strlen.de> wrote:
> This helper needs skb_network_header being set up correctly, are you
> sure thats the case here?  ip pointer is fetched via data + 14 right
> above, so it doesn't look like this would work.
I read it once more carefully, and yes, you are right.
Sorry for wasting your time...
It is my first patch to the netdev subsystem.
So... I was too excited. It's all my fault.
Next time, I'll be careful and deliberate.

Thank you for reviewing.