Re: [PATCH] Fix vlan networking on little-endian systems

[Daniel Kiper]

On Tue, Mar 01, 2022 at 11:18:52AM -0500, Chad Kimes via Grub-devel wrote:
> Vlan configuration seems to have never worked on little-endian systems. This 
> is
> likely because VLANTAG_IDENTIFIER is not byte-swapped before copying into the
> net buffer, nor is vlantag. We can resolve this by using grub_cpu_to_be16 and
> its inverse when copying vlan info to/from the net buffer.

Please add your Signed-off-by tag here.

> ---
>  grub-core/net/ethernet.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/grub-core/net/ethernet.c b/grub-core/net/ethernet.c
> index 4d7ceed6f..e49ccc940 100644
> --- a/grub-core/net/ethernet.c
> +++ b/grub-core/net/ethernet.c
> @@ -58,7 +58,7 @@ send_ethernet_packet (struct 
> grub_net_network_level_interface *inf,
>    struct etherhdr *eth;
>    grub_err_t err;
>    grub_uint8_t etherhdr_size;
> -  grub_uint16_t vlantag_id = VLANTAG_IDENTIFIER;
> +  grub_uint16_t vlantag_id = grub_cpu_to_be16 (VLANTAG_IDENTIFIER);

s/grub_cpu_to_be16/grub_cpu_to_be16_compile_time/

>    etherhdr_size = sizeof (*eth);
>    COMPILE_TIME_ASSERT (sizeof (*eth) + 4 < GRUB_NET_MAX_LINK_HEADER_SIZE);
> @@ -93,8 +93,9 @@ send_ethernet_packet (struct 
> grub_net_network_level_interface *inf,
>                     (char *) nb->data + etherhdr_size - 6, 2);
>
>        /* Add the tag in the middle */
> +      grub_uint16_t vlan = grub_cpu_to_be16 (inf->vlantag);
>        grub_memcpy ((char *) nb->data + etherhdr_size - 6, &vlantag_id, 2);
> -      grub_memcpy ((char *) nb->data + etherhdr_size - 4, (char *) 
> &(inf->vlantag), 2);
> +      grub_memcpy ((char *) nb->data + etherhdr_size - 4, &vlan, 2);
>      }
>
>    return inf->card->driver->send (inf->card, nb);
> @@ -118,9 +119,9 @@ grub_net_recv_ethernet_packet (struct grub_net_buff *nb,
>    /* Check if a vlan-tag is present. If so, the ethernet header is 4 bytes */
>    /* longer than the original one. The vlantag id is extracted and the 
> header */
>    /* is reseted to the original size. */
> -  if (grub_get_unaligned16 (nb->data + etherhdr_size - 2) == 
> VLANTAG_IDENTIFIER)
> +  if (grub_get_unaligned16 (nb->data + etherhdr_size - 2) == 
> grub_cpu_to_be16 (VLANTAG_IDENTIFIER))

Ditto.

>      {
> -      vlantag = grub_get_unaligned16 (nb->data + etherhdr_size);
> +      vlantag = grub_be_to_cpu16 (grub_get_unaligned16 (nb->data + 
> etherhdr_size));
>        etherhdr_size += 4;
>        /* Move eth type to the original position */
>        grub_memcpy((char *) nb->data + etherhdr_size - 6,

Daniel