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[15/40] e1000x: Take CRC into consideration for size check

Message ID 20230414113737.62803-16-akihiko.odaki@daynix.com
State New
Headers show
Series igb: Fix for DPDK | expand

Commit Message

Akihiko Odaki April 14, 2023, 11:37 a.m. UTC 
Section 13.7.15 Receive Length Error Count says:
>  Packets over 1522 bytes are oversized if LongPacketEnable is 0b
> (RCTL.LPE). If LongPacketEnable (LPE) is 1b, then an incoming packet
> is considered oversized if it exceeds 16384 bytes.

> These lengths are based on bytes in the received packet from
> <Destination Address> through <CRC>, inclusively.

As QEMU processes packets without CRC, the number of bytes for CRC
need to be subtracted.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
---
 hw/net/e1000x_common.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Philippe Mathieu-Daudé April 14, 2023, 3:03 p.m. UTC | #1 
On 14/4/23 13:37, Akihiko Odaki wrote:
> Section 13.7.15 Receive Length Error Count says:
>>   Packets over 1522 bytes are oversized if LongPacketEnable is 0b
>> (RCTL.LPE). If LongPacketEnable (LPE) is 1b, then an incoming packet
>> is considered oversized if it exceeds 16384 bytes.
> 
>> These lengths are based on bytes in the received packet from
>> <Destination Address> through <CRC>, inclusively.
> 
> As QEMU processes packets without CRC, the number of bytes for CRC
> need to be subtracted.
> 
> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> ---
>   hw/net/e1000x_common.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/net/e1000x_common.c b/hw/net/e1000x_common.c
> index 6cc23138a8..b4dfc74b66 100644
> --- a/hw/net/e1000x_common.c
> +++ b/hw/net/e1000x_common.c
> @@ -142,10 +142,10 @@ bool e1000x_is_oversized(uint32_t *mac, size_t size)
>   {
>       /* this is the size past which hardware will
>          drop packets when setting LPE=0 */
> -    static const int maximum_ethernet_vlan_size = 1522;
> +    static const int maximum_ethernet_vlan_size = 1522 - 4;
>       /* this is the size past which hardware will
>          drop packets when setting LPE=1 */
> -    static const int maximum_ethernet_lpe_size = 16 * KiB;
> +    static const int maximum_ethernet_lpe_size = 16 * KiB - 4;
>   
>       if ((size > maximum_ethernet_lpe_size ||
>           (size > maximum_ethernet_vlan_size

IMHO this function could be simplified. Something like:

   bool long_packet_enabled = mac[RCTL] & E1000_RCTL_LPE;
   size_t oversize = long_packet_enabled ? 16 * KiB : ETH_VLAN_MAXSIZE;
   size_t crc32_size = sizeof(uint32_t);

   if (mac[RCTL] & E1000_RCTL_SBP) {
     return false;
   }

   if (size + crc32_size > oversize ) {
     ...
     return true;
   }

   return false;
}
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Patch

diff --git a/hw/net/e1000x_common.c b/hw/net/e1000x_common.c
index 6cc23138a8..b4dfc74b66 100644
--- a/hw/net/e1000x_common.c
+++ b/hw/net/e1000x_common.c
@@ -142,10 +142,10 @@  bool e1000x_is_oversized(uint32_t *mac, size_t size)
 {
     /* this is the size past which hardware will
        drop packets when setting LPE=0 */
-    static const int maximum_ethernet_vlan_size = 1522;
+    static const int maximum_ethernet_vlan_size = 1522 - 4;
     /* this is the size past which hardware will
        drop packets when setting LPE=1 */
-    static const int maximum_ethernet_lpe_size = 16 * KiB;
+    static const int maximum_ethernet_lpe_size = 16 * KiB - 4;
 
     if ((size > maximum_ethernet_lpe_size ||
         (size > maximum_ethernet_vlan_size