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Re: [PATCH v3 01/13] net: eth: Add a helper to pad a short ethernet fram
From: |
Philippe Mathieu-Daudé |
Subject: |
Re: [PATCH v3 01/13] net: eth: Add a helper to pad a short ethernet frame |
Date: |
Tue, 16 Mar 2021 09:49:45 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 |
On 3/16/21 9:12 AM, Bin Meng wrote:
> Add a helper to pad a short ethernet frame to the minimum required
> length, which can be used by backend codes.
>
> Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
>
> ---
>
> Changes in v3:
> - use 'without' instead of 'sans'
> - add a helper to pad short frames
>
> include/net/eth.h | 25 +++++++++++++++++++++++++
> 1 file changed, 25 insertions(+)
>
> diff --git a/include/net/eth.h b/include/net/eth.h
> index 0671be6916..bc064f8e52 100644
> --- a/include/net/eth.h
> +++ b/include/net/eth.h
> @@ -31,6 +31,31 @@
>
> #define ETH_ALEN 6
> #define ETH_HLEN 14
> +#define ETH_ZLEN 60 /* Min. octets in frame without FCS */
> +
> +/**
> + * pad_short_frame - pad a short frame to the minimum ethernet frame length
> + *
> + * If the ethernet frame size is shorter than 60 bytes, it will be padded to
> + * 60 bytes at the address @min_pkt.
> + *
> + * @min_pkt: buffer address to hold the padded frame
> + * @pkt: address to hold the original ethernet frame
> + * @size: size of the original ethernet frame
> + * @return true if the frame is padded, otherwise false
> + */
> +static inline bool pad_short_frame(uint8_t *min_pkt, const uint8_t *pkt,
> + int size)
> +{
> + if (size < ETH_ZLEN) {
> + /* pad to minimum ethernet frame length */
> + memcpy(min_pkt, pkt, size);
> + memset(&min_pkt[size], 0, ETH_ZLEN - size);
> + return true;
> + }
> +
> + return false;
> +}
I don't want to be too nitpicky but since I'm Cc'ed...
- 'ethernet' -> 'Ethernet'
- I'm not sure inlining is justified
- The same function is used for 2 different operations,
. check if padding is required
. do the padding
- If we provide a function a buffer to fill, we need to check the
buffer size is big enough to avoid overflow
What about something like:
bool pad_short_frame(char *padded_pkt, size_t *padded_buflen,
const void *pkt, size_t pkt_size);
{
assert(padded_buflen && *padded_buflen >= ETH_ZLEN);
if (src_size >= ETH_ZLEN) {
return false;
}
/* pad to minimum ethernet frame length */
memcpy(padded_pkt, pkt, pkt_size);
memset(&padded_pkt[pkt_size], 0, ETH_ZLEN - padded_buflen);
*padded_buflen = ETH_ZLEN;
return true;
}
What do you think?
- [PATCH v3 00/13] net: Pad short frames for network backends, Bin Meng, 2021/03/16
- [PATCH v3 01/13] net: eth: Add a helper to pad a short ethernet frame, Bin Meng, 2021/03/16
- Re: [PATCH v3 01/13] net: eth: Add a helper to pad a short ethernet frame,
Philippe Mathieu-Daudé <=
- [PATCH v3 03/13] net: slirp: Pad short frames to minimum size before send, Bin Meng, 2021/03/16
- [PATCH v3 02/13] net: Add a 'do_not_pad" to NetClientState, Bin Meng, 2021/03/16
- [PATCH v3 04/13] net: tap: Pad short frames to minimum size before send, Bin Meng, 2021/03/16
- [PATCH v3 05/13] hw/net: virtio-net: Initialize nc->do_not_pad to true, Bin Meng, 2021/03/16
- [PATCH v3 06/13] hw/net: e1000: Remove the logic of padding short frames in the receive path, Bin Meng, 2021/03/16
- [PATCH v3 07/13] hw/net: vmxnet3: Remove the logic of padding short frames in the receive path, Bin Meng, 2021/03/16
- [PATCH v3 08/13] hw/net: i82596: Remove the logic of padding short frames in the receive path, Bin Meng, 2021/03/16
- [PATCH v3 09/13] hw/net: ne2000: Remove the logic of padding short frames in the receive path, Bin Meng, 2021/03/16